U.S. GOVERNMENT PUBLISHING OFFICE

35–231PDF WASHINGTON : 2019

THE STATE OF CLIMATE SCIENCE 

AND WHY IT MATTERS 

HEARING 

BEFORE THE

COMMITTEE ON SCIENCE, SPACE, AND 

TECHNOLOGY 

HOUSE OF REPRESENTATIVES 

ONE HUNDRED SIXTEENTH CONGRESS 

FIRST SESSION 

FEBRUARY 13, 2019 

Serial No. 116–1 

Printed for the use of the Committee on Science, Space, and Technology 

( 

Available via the World Wide Web: http://science.house.gov 
(II) 

COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY 

HON. EDDIE BERNICE JOHNSON, Texas, Chairwoman 

ZOE LOFGREN, California 

DANIEL LIPINSKI, Illinois 

SUZANNE BONAMICI, Oregon 

AMI BERA, California, 

Vice Chair 

CONOR LAMB, Pennsylvania 

LIZZIE FLETCHER, Texas 

HALEY STEVENS, Michigan 

KENDRA HORN, Oklahoma 

MIKIE SHERRILL, New Jersey 

BRAD SHERMAN, California 

STEVE COHEN, Tennessee 

JERRY MCNERNEY, California 

ED PERLMUTTER, Colorado 

PAUL TONKO, New York 

BILL FOSTER, Illinois 

DON BEYER, Virginia 

CHARLIE CRIST, Florida 

SEAN CASTEN, Illinois 

KATIE HILL, California 

BEN MCADAMS, Utah 

JENNIFER WEXTON, Virginia 

FRANK D. LUCAS, Oklahoma, 

Ranking Member 

MO BROOKS, Alabama 

BILL POSEY, Florida 

RANDY WEBER, Texas 

BRIAN BABIN, Texas 

ANDY BIGGS, Arizona 

ROGER MARSHALL, Kansas 

NEAL DUNN, Florida 

RALPH NORMAN, South Carolina 

MICHAEL CLOUD, Texas 

TROY BALDERSON, Ohio 

PETE OLSON, Texas 

ANTHONY GONZALEZ, Ohio 

MICHAEL WALTZ, Florida 

JIM BAIRD, Indiana 

VACANCY 

VACANCY 
(III) 

C O N T E N T S 

February 13, 2019 

Page 

Hearing Charter ...................................................................................................... 2 

Opening Statements 

Statement by Representative Eddie Bernice Johnson, Chairwoman, Committee on Science, Space, and Technology, U.S. House of Representatives .... 8 

Written Statement ............................................................................................ 10 

Statement by Representative Frank D. Lucas, Ranking Member, Committee 

on Science, Space, and Technology, U.S. House of Representatives ................ 12 

Written Statement ............................................................................................ 14 

Witnesses: 

Dr. Robert Kopp, Director, Rutgers Institute of Earth, Ocean, and Atmospheric Sciences, and Professor, Department of Earth and Planetary 

Sciences, Rutgers University 

Oral Statement ................................................................................................. 17 

Written Statement ............................................................................................ 19 

Dr. Jennifer Francis, Senior Scientist, Woods Hole Research Center 

Oral Statement ................................................................................................. 33 

Written Statement ............................................................................................ 35 

Dr. Joseph Majkut, Director of Climate Policy, Niskanen Center 

Oral Statement ................................................................................................. 41 

Written Statement ............................................................................................ 43 

Dr. Kristie L. Ebi, Rohm and Haas Endowed Professor in Public Health 

Sciences, and Director, Center for Health and the Global Environment, 

University of Washington 

Oral Statement ................................................................................................. 54 

Written Statement ............................................................................................ 56 

Dr. Natalie M. Mahowald, Irving Porter Church Professor of Engineering, 

Faculty Director for the Environment, Atkinson Center for a Sustainable 

Future, Cornell University 

Oral Statement ................................................................................................. 76 

Written Statement ............................................................................................ 78 

Discussion ................................................................................................................. 115

Appendix I: Answers to Post-Hearing Questions 

Dr. Robert Kopp, Director, Rutgers Institute of Earth, Ocean, and Atmospheric Sciences, and Professor, Department of Earth and Planetary 

Sciences, Rutgers University ............................................................................... 152 

Dr. Jennifer Francis, Senior Scientist, Woods Hole Research Center ................. 157 

Dr. Joseph Majkut, Director of Climate Policy, Niskanen Center ....................... 162 

Dr. Kristie L. Ebi, Rohm and Haas Endowed Professor in Public Health 

Sciences, and Director, Center for Health and the Global Environment, 

University of Washington .................................................................................... 168 
Page

IV 

Appendix II: Additional Material for the Record 

Letter submitted by Representative Lizzie Fletcher, Committee on Science, 

Space, and Technology, U.S. House of Representatives .................................... 246 

Report submitted by Representative Bill Foster, Committee on Science, Space, 

and Technology, U.S. House of Representatives ............................................... 248 

Article submitted by Representative Sean Casten, Committee on Science, 

Space, and Technology, U.S. House of Representatives .................................... 269 
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THE STATE OF CLIMATE SCIENCE 

AND WHY IT MATTERS 

WEDNESDAY, FEBRUARY 13, 2019 

HOUSE OF REPRESENTATIVES, 

COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY, 

Washington, D.C. 

The Committee met, pursuant to notice, at 10:01 a.m., in room 

2318, Rayburn House Office Building, Hon. Eddie Bernice Johnson 

[Chairwoman of the Committee] presiding. 
2 

COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY 

U.S. HOUSE OF REPRESENTATIVES 

HEARING CHARTER 

The State of Climate Science and Why it Matters 

PURPOSE 

Wednesday, February 13,2019 

10:00 a.m. 

2318 Rayburn House Office Building 

On Tuesday, February 12th, the Committee on Science, Space, and Technology will hold a full 

Committee hearing entitled "The State of Climate Science and Why it Matters. " The purpose of 

this hearing is to provide a big-picture assessment of the current state of climate science. The 

Committee will receive expert testimony on recently published significant climate reports and 

discuss report findings that include the physical mechanisms of climate change, risks to human 

society at different levels of warming, and the need for adaptation and mitigation. 

WITNESSES 

• Dr. Natalie M. Mahowald- Irving Porter Church Professor of Engineering, Faculty 

Director for the Environment, Atkinson Center for a Sustainable Future, Cornell 

University 

• Dr. Robert Kopp- Director, Rutgers Institute of Earth, Ocean, and Atmospheric 

Sciences, and Professor, Department of Earth and Planetary Sciences, Rutgers University 

• Dr. Jennifer Francis Senior Scientist, Woods Hole Research Center 

• Dr. Joseph Majkut- Director of Climate Policy, Niskanen Center 

• Dr. Kristie Ebi- Rohm & Haas Endowed Professor in Public Health Sciences, Director, 

Center for Health and the Global Environment (CHanGE), University of Washington 

BACKGROUND 

The State of Climate Science 

While the understanding of the basic physical mechanisms of climate change has not changed 

significantly over the last 20 years, recent research has provided even stronger evidence in support 

of the scientific consensus that the climate is warming and it is primarily driven by the emissions 

of greenhouse gases due to human activities. In addition, there is significant literature on the 

contemporary impacts of climate change to human and ecological systems, as well as extensive 

analysis of likely future impacts given different levels of warming. Several recent national and 

international reports, described below, have assessed and synthesized the current state of scientific 

understanding of climate change and related impacts, as well as the costs and benefits of different 

mitigation strategies. 
3 

Recent Climate Reports 

IPCC Special Report on Global Warming of 1.5°C. Released in October Z018, the 

Intergovernmental Panel on Climate Change (IPCC) 1 Special Report on Global Warming of l.SOC2 

(IPCC SRI.S) was produced separately from the periodic assessments required under the United 

Nations Framework Convention on Climate Change (UNFCCC). The IPCC SR1.5 was 

commissioned by world leaders, including some from small island nations, under the ZOIS Paris 

Agreement. 3 While the final pledges under the Paris Agreement would limit warming to zoe, some 

countries requested a study on how the risks of warming of l.S°C above preindustrial levels would 

compare to the risks of warming of zoe. The report's 91 authors and review editors from 40 

countries drew its conclusions through a review of over 6,000 studies. Apart from comparing the 

risks of l.S°C to zoe, it provides context for these targets by showing where they fall on the current 

emissions trajectory. 

The report found that limiting warming to 1.5°C rather than zoe would have wide-ranging benefits. 

However, doing so "would require rapid, far-reaching and unprecedented changes in all aspects of 

society," including cutting global carbon emissions to net zero by ZOSO, and boosting renewable 

energy to make up over 50 percent of the U.S. energy mix by ZOSO. It is estimated that achieving 

this goal would require five times the current investment in low carbon technologies, as well as 

high prices on carbon emissions. The scientific literature has demonstrated lower risks at 1.5°C 

compared with zoe in every category addressed. In fact, one of the biggest differences between 

this report and past IPCC assessments is that it provides an unprecedented level of granularity in 

differentiating the risks of a l.S°C world compared with a zoe world. Though the IPCC SRl.S 

finds it is more difficult to transition global carbon emissions to a level that would limit warming 

to l.S°C than to zoe, it would avoid enormous losses to global Gross Domestic Product (GDP). 

The U.S. could lose around l.Z percent of its GDP for every additional l°C of warming above the 

current levels. The IPCC SRl.S concludes that though technology to limit warming to I.S°C does 

exist, global political trends make this outcome difficult, even nearly impossible, to achieve. 

Fourth National Climate Assessment. The National Climate Assessment is a congressionally 

mandated report published quadrennially by the U.S. Global Change Research Program 

(USGCRP), a federal program directed by Congress to coordinate 13 member federal agencies4 

1 The Intergovernmental Panel on Climate Change (IPCC) was created by the United Nations Framework 

Convention on Climate Change (UNFCCC), a multilateral agreement signed by President George H.W. Bush and 

ratified by the Senate. It is an international body that develops non-policy-prescriptive reports; these reports do not 

produce their own science but rather synthesize current climate science to inform decision makers and the public and 

are usually released every 5 to 6 years. (https://www.ipcc.ch/) 2 IPCC, 2018: Summary for Policymakers. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of 

global warming of I.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the 

context of strengthening the global response to the threat of climate change, sustainable development, and efforts to 

eradicate poverty (Masson-Delmotte, V., P. Zhai, H.-0. Portner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, 

Moufouma-Okia, C. Pean, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, 

Maycock, M. Tignor, and T. Waterfield (eds.)]. World Meteorological Organization, Geneva, Switzerland, 32 pp. 3 A multilateral agreement to limit climate change to 2C signed by 195 countries in 2016. https://unfccc.int/processand-meetings/the-paris-agreement/the-paris-agreement 

4 The 13 agencies are the Departments of Agriculture, Commerce, Defense, Energy, Health and Human Services, the 

Interior, State, and Transportation, as well as the Environmental Protection Agency, National Aeronautics and Space 

z 
4 

that conduct or apply research on global environmental change. 5 Volume I of the Fourth National 

Climate Assessment (NCA4 Vol 1): Climate Science Special Report,6 released in 2017, examines 

the latest science on the physical drivers of climate change, climate models and projections, 

changes in temperature and extreme weather, ocean acidification, and sea level rise. More than 

300 scientists in the l3 member agencies wrote this 470-page volume, and its conclusions are 

based on the evaluation of over I ,500 climate science studies. The final product was then peer 

reviewed by the National Academies of Science, Engineering and Medicine (NASEM). 

The report is consistent with the last twenty years of climate science, which has confirmed that 

since the turn of the century, climate change is occurring and is caused by carbon pollution released 

by human industrial activity. More robust evidence now exists showing the correlation between 

human activities and increases in global temperature, the warming and further acidification of our 

oceans, rising sea levels, and disappearing arctic ice sheets. The conclusions of the report are 

scientifically conservative; the authors required a large amount of evidence and a high number of 

studies supporting a finding before including it in the report's conclusions. Though NCA4 Vol I 

does not provide policy recommendations or assess climate mitigation or adaption strategies, it 

does note that limiting global warming to 2°C will require major reductions in greenhouse gas 

emissions. 

Volume II of the Fourth National Climate Assessment (NCA4 Vol 2): Impacts, Risks, and 

Adaptation in the United States, 7 released in November 2018, is a I ,524-page report that 

exhaustively outlines the effects and risks of climate change in the U.S., which is broken into I 0 

geographic regions,8 and 16 national topics.9 The NCA4 Vol 2 shows how climate change is 

increasingly impacting our communities, and how mitigation and adaptation strategies can 

improve the circumstances. Key scientific advances since the Third National Climate Assessment 

(NCA3) include advances in attribution of human influence on climate and extreme weather 

events, rapid changes for ice loss globally, as well as increases in ocean acidification, warming 

and deoxygenation. Following feedback received after the publication of the NCA3, the NCA4 

provided its analysis in a more localized format to better describe and communicate specific 

climate change impacts on different regions across the country. The NCA4 Vol2 finds that under 

high emissions scenarios with limited or no adaptation, losses are great: a predicted $141 billion 

Administration, National Science Foundation, Smithsonian Institution, and U.S. Agency for International 

Development. 

5 It was established by Presidential Initiative in 1989 under George H. W. Bush, and mandated by Congress in the 

Global Change Research Act of 1990. (https://www.globalchange.gov/about/legal-mandate) 6 USGCRP, 2017: Climate Science Special Report: Fourth National Climate Assessment, Volume I [Wuebbles, 

D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. U.S. Global Change 

Research Program, Washington, DC, USA, 470 pp., doi: l0.7930/JOJ964J6. 7 USGCRP, 2018: Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, 

Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. 

Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 1515 pp. doi: 10.7930/NCA4.2018 8 Regions include Northeast, Southeast, U.S. Caribbean, Midwest, Norther Great Plains, Southern Great Plains, 

Northwest, Southwest, Alaska, Hawai'i & U.S.-Affiliated Pacific Islands. 9 National topics include Our Changing Climate, Water, Energy Supply, Delivery & Demand, Land Cover & LandUse Change, Forests, Ecosystems, Ecosystem Services, & Biodiversity, Coastal Effects, Oceans & Marine 

Resources, Agriculture & Rural Communities, Built Environment, Urban Systems, & Cities, Transportation, Air 

Quality, Human Health, Tribes & Indigenous Peoples, Climate Effects on U.S. International Interests, Sectoral 

Interactions, Multiple Stressors, & Complex Systems. 

3 
5 

from heat-related deaths, $118 billion from sea level rise, $32 billion in costs to infrastructure, and 

$160 billion lost wages from two billion lost labor hours by the end of the century. It is very likely 

that some impacts are irreversible. However, many impacts can be avoided or substantially reduced 

if emissions of greenhouse gases are reduced. 

Climate Change and Extreme Weather Events. The nascent field of extreme event attribution 

tries to determine how much of an extreme event can be attributed to climate change versus regular 

weather patterns. The field is advancing rapidly, and in 2016, the NASEM published Attribution 

of Extreme Weather Events in the Context of Climate Change, 10 which looked at the consensus on 

to what extent scientists can estimate the influence climate change has on extreme weather events. 

Extreme event attribution teases out the effects of anthropogenic, or human-caused, climate change 

from other factors that influence climate, such as changes in solar activity and natural, internal 

processes of the climate system, such as El Nino. 

The NASEM study found that climate change is exacerbating some extreme weather events, with 

temperature-such as heat waves and long-term warming- being the strongest influence of climate 

change on extreme events. It finds less certain links between climate change and the occurrence of 

tornadoes, hurricanes, or wildfires. However, the intensity of hurricanes, such as the extreme 

precipitation during Hurricane Harvey, has been linked to climate change. 11 Similarly, the Bulletin 

of the American Meteorological Society released a supplement in December 2018 entitled 

"Explaining Extreme Events of 2017 From a Climate Perspective"12 which found that events 

ranging from the floods in South America to heatwaves in China were made more likely due to 

anthropogenic climate change. It is important to note that current scientific literature cannot 

definitively answer whether climate change "caused" an individual weather event to occur; rather 

that that climate change can alter the intensity or frequency of certain events. 13 Nevertheless, the 

report marks the "second year that scientists have identified extreme weather events that they said 

could not have happened without warming of the climate through human-induced climate 

change."14 

Climate Change and Health. As scientific evidence of direct and indirect impacts of climate 

change on human health is becoming clearer, the global health community is actively framing 

climate change as a public health crisis. In 2018, the Lancet Countdown Report: Tracking 

10 National Academies of Sciences, Engineering, and Medicine. 2016. Attribution of Extreme Weather Events in the 

Context of Climate Change. Washington, DC: The National Academies Press. https://doi.org/10.17226/21852. 11 Vano J, Dettinger M., Cifelli Ret. al, "Hydroclimatic Extremes as Challenges for the Water Management 

Community: Lessons From the Oroville Dam and Hurricane Harvey." Special Supplement to the Bulletin of the 

American Meteorological Society, Vol. 99 No. 12, December 2018. "Explaining Extreme Events of2017 From a 

Climate Perspective." 12 Special Supplement to the Bulletin of the American Meteorological Society, Vol. 99 No. 12, December 2018. 

"Explaining Extreme Events of 2017 From a Climate Perspective." 

https://www.ametsoc.org!ams/index.cfrnlpublicationslbulletin-of-the-american-meteorological-societybams/explaining-extreme-events-from-a-climate-perspective/ 

13 National Academies of Sciences, Engineering, and Medicine News. 2016. New Report Says Science Can Estimate 

Influence of Climate Change on Some Types of Extreme Events. 

http:llwww8.nationa/academies.orr:!onpinews!newsitem.aspx?RecordlD=21852 

14 https://www.ametsoc.org!ams/index.cfrn/publicationslbulletin-of-the-american-meteorological-societybams/explaining-extreme-events-from-a-climate-perspective/ 

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6 

Progress on Health and Climate Change 15 was released as a collaboration between researchers 

around the world. The Lancet Countdown tracks the connections between health and climate as 

well as how climate change solutions can mitigate health impacts. The Lancet Countdown finds 

that current public health challenges due to climate change will be further exacerbated as global 

temperatures rise and the nature and scale of our global response to climate change will 

determine global health for generations. 

24fh Conference of the Parties (COP24) Special Report: Health and Climate Change. 16 During 

the Conference of Parties 23 (COP23) held in Bonn, Germany on behalf of the Republic of Fiji, 

Prime Minister Bainimarama ofFiji requested that the World Health Organization (WHO) prepare 

a report on health and climate change to be delivered at the COP24 in Katowice, Poland. 17 The 

COP24 Special Report made many recommendations such as promoting actions to reduce global 

carbon emissions and other air pollutants, tracking progress in health due to climate change 

mitigation, and mobilizing subnationalleaders to take action on this issue. They also recommended 

highlighting the health implications of climate adaptation and mitigation strategies. 

The IPCC SRI.S included health implications throughout its findings. Climate change impacts 

such as increased global temperatures, extreme weather events, and flooding and sea level rise can 

exacerbate the spread of infectious and vector borne diseases, degrade air quality, and endanger 

food and water security. Limiting warming to l.5°C would have many public health benefits. 

The key messages from the human health chapter of the NCA4 Volume 2 show that climate change 

is already affecting the health of all Americans through increased exposure to extreme weather 

events and infectious or vector-borne diseases, and through changes in air quality and mental 

health stress. The most vulnerable populations, such as lower-income communities, the elderly, 

children, and some communities of color, are likely to experience even greater health risks from 

climate change. However, adaptation measures can help reduce the impacts and risk of climaterelated health impacts, and mitigation of greenhouse gas emissions has clear economic and health 

benefits. 18 

Evidence of Climate Change Impacts 

Climate change is already affecting communities in direct and indirect ways. Some scientifically 

supported evidence of climate change impacts include: 

Sea Level Rise. The average global sea level has risen approximately 7-8 inches since 1900, "with 

almost half this rise occurring since 1993 as oceans have warmed and land-based ice has melted." 

By 2030, global mean sea level is very likely (emphasis theirs) to rise by 0.3-0.6 feet. 19 

15 Watts N, Amann M, Ayeb-Karlsson S, eta/.: The Lancet Countdown on health and climate change: from 25 years 

of inaction to a global transformation for public health. Lancet. 2018; 391(10120): 581--630. 

https://www.thelancet.com/journals/lancet/article/PIISO 140-6736( 18)32594-7/fulltext 16COP24 special report: health and climate change. Geneva: World Health Organization; 2018. Licence: CC BYNC-SA 3.0 !GO. https://anps.who.int/iris/bitstreamlhandle/10665/276405/9789241514972-eng.odf?ua=1 17 https://www.who.int/globalchange/publications/COP24-report-health-climate-change/en/ 1

' NCA4 Volume 2 19 NCA4 Volume I 

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Global Temperature Rise. The planet has already warmed about 1 °C above preindustrial levels, 

and at the current trajectory of carbon emissions, the world could reach anthropogenic global 

warming of 1.5°C as soon as 2030.20 

Shrinking Arctic Ice Sheets. Annually averaged arctic ice sheet extent has decreased over 3.5 

percent every decade from 1979 to 2016, with the "annual arctic sea ice maximum in March 

2017 ... the lowest maximum areal extent on record."21 

Warming Oceans. Over 90 percent of the heat attributed to anthropogenic emissions to date have 

been absorbed by the oceans, making them warmer. Global average sea surface temperature could 

increase by approximately 2. 7°C by 2100 in a high emissions scenario. 22 

Extreme Weather Events. Extreme weather events alone have cost the United States over $1 

trillion since 1980,23 with the U.S. experiencing 14 weather and climate disasters totaling $14 

billion in 2018 alone.24 

Additional Reading 

IPCC Special Report: Global Warming of 1.5°C: Summary for Policymakers 

https://www.ipcc.ch/sr15/chapter/summarv-for-policy-makers/ 

The 1.5 Health Report: Synthesis on Health & Climate Science in the IPCC SR1.5 

https://www.who.int/globalchange/181008 the 1 5 healthreport.pdf 

NCA4 Volume 1 Executive Summary 

https://science20 17 .globalchange.gov/chapter/executive-summary/ 

NCA4 Volume 2 Summary Findings 

https://nca2018.globalchange.gov/downloads/NCA4 Ch01 Summarv-Findings.pdf 

20 IPCC SR 1.5 21 NCA4 Volume I 22 NCA4 Volume I 23 NCA4 Volume 1 24 NOAA.gov, February 6th, 2018. "2018 was 4th hottest year on record for the globe." 

https://www.noaa.gov/news/2018-was-4th-hottest-year-on-record-for-globe 

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Chairwoman JOHNSON. This hearing will come to order. Without 

objection, the Chair is authorized to declare a recess at any time. 

Good morning, and welcome to today’s hearing entitled, ‘‘The 

State of Climate Science and Why it Matters.’’ Let me first welcome everyone to the full Committee hearing of the Committee on 

Science, Space, and Technology for the 116th Congress. I’m looking 

forward to a productive and collegial meeting today, one in which 

rigorous scientific discourse can help enable the creation of a sound 

public policy. 

Every committee is meeting because we’ve had to alter committee meetings this week because we’ve had two funerals. And so 

we will have Members coming and going, and we hope that you’ll 

understand. 

I also want to welcome all of our distinguished witnesses and 

thank them for their flexibility in making themselves available to 

participate in this rescheduled hearing. 

Today’s hearing is the first in what will be multiple climatechange-related hearings this Congress. Following the release of the 

IPCC (Intergovernmental Panel on Climate Change) Special Report 

on Global Warming of 1.5 °C, and the National Climate Assessment last year, it is clear that we’re responsible for our planet 

warming at an alarming rate, and we already are feeling the impacts of this warming today. Setting the stage with a discussion of 

the most relevant and up-to-date scientific evidence from these and 

other reports will allow us to better understand the climate-related 

impacts we are experiencing in all of our districts. The evidence of 

continued unmitigated emissions of greenhouse gases is clear. Our 

coastal communities are dealing with sea-level rise and ocean acidification, and all communities are dealing with more severe weather 

incidences and the increased exposure to extreme heat and poor air 

quality. 

Today’s discussion on climate science is important to deepening 

our fundamental understanding of why the climate is changing and 

how this manifests in ways that impact society. It will also help us 

as we turn our focus to the role of science and innovative technology development to devise adaptation and mitigation strategies, 

which will have numerous positive benefits for our economy, our 

safety and security, and our public health. I am glad we have the 

leading experts in these fields who worked closely on these reports 

to guide our discussion. 

I also want to note that the impacts of climate change are not 

limited to what is described in these climate science reports. Just 

last week, NOAA’s (National Oceanic and Atmospheric Administration) State of the Climate Report for 2018 found that it was the 

wettest year for the contiguous United States in the past 35 years. 

NASA (National Aeronautics and Space Administration) and NOAA 

also found that last year had the fourth-highest global surface temperature since 1880. It has almost become a given that we can expect record-breaking temperatures every year, especially since the 

past 5 years have been the warmest in modern record. 

Though this Administration has regrettably chosen to ignore the 

findings of its own scientists in regards to climate change, we as 

lawmakers have a responsibility to protect the public’s interest. I 

plan to do this by making sure this Committee is informed by the 
9 

most relevant and up-to-date science as we work to conduct our 

legislative and oversight responsibilities. The Science Committee 

oversees much of the Federal climate research, and as well as the 

development and demonstration of new and innovative technologies, which makes our role as Members of this Committee critical to preparing our country to deal with climate change. 

I look forward to kicking off a fruitful and informative discussion 

that will continue throughout this Congress on why we need to act 

on climate change now. 

[The prepared statement of Chairwoman Johnson follows:] 
10 

Opening Statement 

Chairwoman Eddie Bernice Johnson 

House Committee on Science, Space, and Technology 

The State of Climate Science and Why it Matters 

February 13,2019 

Let me first welcome everyone to the first full Committee Hearing of the Committee on Science, 

Space, and Technology for the I 16th Congress. I am looking forward to a productive and 

collegial meeting today, one in which rigorous scientific discourse can help enable the creation 

of sound public policy. 

I also want to welcome all of our distinguished witnesses, and thank them for their flexibility in 

making themselves available to participate in this rescheduled hearing. 

Today's hearing is the first in what will be multiple climate change-related hearings this 

Congress. Following the release of the IPCC special report on global warming of 1.5°C, and the 

National Climate Assessment last year, it is clear that we are responsible for our planet warming 

at an alarming rate, and we already feeling the impacts of this warming today. Setting the stage 

with a discussion of the most relevant and up-to date scientific evidence from these and other 

reports, will allow us to better understand the climate-related impacts we are experiencing in all 

of our districts. The evidence of continued unmitigated emissions of greenhouse gases is clear. 

Our coastal communities are dealing with sea level rise and ocean acidification, and all 

communities are dealing with more severe weather incidents, and the increased exposure to 

extreme heat and poor air quality. 

Today's discussion on climate science is important to deepening our fundamental understanding 

of why the climate is changing, and how this manifests in ways that impact society. It will also 

help us as we turn our focus to the role of science and innovative technology development to 

devise adaptation and mitigation strategies, which will have numerous positive benefits for our 

economy, our safety and security, and our public health. I am glad we have the leading experts in 

these fields who worked closely on these reports to guide our discussion. 

I also want to note that the impacts of climate change are not limited to what is described in these 

climate science reports. Just last week, NOAA's State of the Climate Report for 2018 found that 

it was the wettest year for the contiguous U.S. in the past 35 years. NASA and NOAA also found 

that last year had the fourth highest global surface temperature since 1880. It has almost become 

a given that we can expect record-breaking temperatures every year, especially since the past 

five years have been the warmest in the modern record. 

Though this Administration has regrettably chosen to ignore the findings of its own scientists in 

regards to climate change, we as lawmakers have a responsibility to protect the public's interest. 

I plan to do this by making sure this Committee is informed by the most relevant and up to date 

science as we work to conduct our legislative and oversight responsibilities. The Science 

Committee oversees much of the federal climate research, as well as the development and 

1 
11 

demonstration of new and innovative technologies, which makes our role as Members of this 

Committee critical to preparing our country to deal with climate change. 

I look forward to kicking off a fruitful and informative discussion that will continue throughout 

this Congress on why we need to act on climate change now. 

Thank you, and I will now yield to Ranking Member Lucas for his statement. 

2 
12 

Chairwoman JOHNSON. Now I will recognize the Ranking Member’s opening statement. 

Mr. LUCAS. Thank you, Chairwoman Johnson, and I would like 

to again thank you for holding this hearing and providing a platform to hold a constructive dialog on the issue of climate change. 

I’m proud to be a western Oklahoma farmer and to represent a 

resilient community of farmers. As any farmer can tell you, we are 

especially dependent on the weather. Droughts and heat waves 

come and go naturally, but the changing climate has intensified 

their impacts. 

We know the climate is changing and that global industrial activity has played a role in this phenomenon. But our communities, 

like the farmers and ranchers in my district, need to know more 

about the extent to which a changing climate affects short- and 

long-term weather patterns. 

I believe the Federal Government has a responsibility to 

prioritize research so that we can better understand the complex 

relationship between climate and weather and increase preparedness in our communities. I also believe it’s critical that America 

leads the world in developing the next-generation technologies to 

address the effects of climate change. 

Fortunately, we have a unique opportunity here on the Science 

Committee to promote research and technology solutions. American 

industry, innovators, and researchers at our national labs are pioneering technologies that capture carbon emissions from coal and 

natural gas, batteries that store energy from intermittent energy 

sources like wind and solar, and advanced nuclear reactors that 

can provide cleaner, more affordable power. These technologies 

have the potential to reduce greenhouse gas emissions around the 

world and ensure American energy dominance. 

America has always led the way in technology advances. In 1919, 

my great aunt’s prized possession was a phonograph, a mechanical 

device which was then state-of-the-art technology. A hundred years 

later, we listen to music on our cell phones, and no one could have 

predicted the incredible leap forward in technology. Americans are 

always innovating, finding surprising ways to meet new challenges. 

Energy is no exception. Hydraulic fracking revolutionized energy 

production, unlocking a vast American energy resource that was 

unimaginable just a decade ago. Developed by industry in cooperation with the national labs, fracking reduced the environmental 

footprint of energy production and has brought cleaner, cheaper 

natural gas to the market around the world. 

Through innovation, we can repeat this incredible success. The 

next technological breakthrough is right around the corner, and if 

we want to succeed, we must continue to focus on realistic, technology-driven solutions to climate change that can compete in today’s economy. We won’t succeed in pie-in-the-sky policies that demand 100 percent renewable energy at the expense of reliable 

power from nuclear and fossil fuels and raise energy prices for 

businesses and consumers. 

Today, we’ll hear from Dr. Joseph Majkut, the Director of Climate Policy for the Niskanen Center, who will stress that it’s essential that we take a realistic, innovative, and competitive approach to addressing climate change. I share his belief that by in-
13 

vesting in research to develop carbon capture, carbon use, advanced nuclear and renewable energy technologies, we can 

incentivize innovation and growth in these industries and reduce 

carbon emissions in the process. Innovation is good for the global 

environment and the American economy. 

I take environmental policy very seriously. This dedication comes 

from being raised by people who lived through the worst prolonged 

environmental disaster in American history, the great drought and 

Dust Bowl of the 1930s. We have a responsibility to ensure events 

like the Dust Bowl never occur again. 

While this Committee cannot control the weather, we can 

prioritize investments in basic science and energy research that 

will revolutionize the global energy market. America led the world 

in coal, oil, and gas. Now we must lead again, and partner with industry to develop breakthrough energy technologies and make our 

existing energy sources cleaner and more affordable. 

I thank our witnesses for being here today, and I yield back the 

balance of my time, Madam Chairman. 

[The prepared statement of Mr. Lucas follows:] 
14 

Ranking Member Lucas Opening 

Statement on Climate Change at Full 

Committee Hearing 

Feb 12,2019 Opening Statement 

Chairwoman Johnson, I would like to thank you for holding this hearing and 

providing a platform to hold a constructive dialogue on the issue of climate 

change. 

I'm proud to be a Western Oklahoma farmer and to represent a resilient 

community of farmers. As any farmer can tell you, we are especially dependent 

on the weather. Droughts and heat waves come and go naturally, but the 

changing climate has intensified their impacts. 

We know the climate is changing and that global industrial activity has played a 

role in this phenomenon. But our communities, like the farmers and ranchers in 

my district need to know more about the extent to which a changing climate 

affects short- and long-term weather patterns. 

I believe the federal government has a responsibility to prioritize research so we 

can better understand the complex relationship between climate and weather 

and increase preparedness in our communities. 

I also believe it is critical that America leads the world in developing the next 

generation technologies to address the effects of climate change. 

Fortunately, we have a unique opportunity here on the Science Committee to 

promote research and technology solutions. American industry, innovators, and 

researchers at our national labs are pioneering technologies that capture 

carbon emissions from coal and natural gas, batteries that store energy from 

intermittent energy sources like wind and solar, and advanced nuclear reactors 

that can provide cleaner, more affordable power. These technologies have the 

potential to reduce greenhouse gas emissions around the world and ensure 

American energy dominance. 

America has always led the way in technological advancement. In 1919, my 

great aunt's prized possession was a phonograph- a mechanical device which 

was then state-of-the-art-technology. A hundred years later, we listen to music 

on our cell phones, and no one could have predicted the incredible leap 

forward in technology. Americans are always innovating, finding surprising ways 

to meet new challenges. 
15 

Energy is no exception. Hydraulic fracturing revolutionized energy production, 

unlocking a vast, American energy resource that was unimaginable just a 

decade before. Developed by industry in cooperation with the national labs, 

fracking reduced the environmental footprint of energy production and brought 

cleaner, cheaper natural gas to the market around the world. 

Through innovation, we can repeat this incredible success. The next technology 

breakthrough is right around the corner- and if we want to succeed, we must 

continue to focus on realistic, technology-driven solutions to climate change 

that can compete in today's economy. 

We won't succeed with pie-in-the-sky policies that demand 100% renewable 

energy at the expense of reliable power from nuclear and fossil fuels and raise 

energy prices for businesses and consumers. 

Today we will hear from Dr. Joseph Majkut, the Director of Climate Policy for the 

Niskanen Center, who will stress that it is essential that we take a realistic, 

innovative, and competitive approach to addressing climate change. 

I share his belief that by investing in research to develop carbon capture, 

carbon use, advanced nuclear, and renewable energy technologies, we can 

incentivize innovation and growth in these industries - and reduce global 

emissions in the process. Innovation is good for the global environment and the 

American economy. 

I take environmental policy very seriously. This dedication comes from being 

raised by people who lived through the worst prolonged environmental disaster 

in American history, the drought and dust bowl of the 1930s. We have a 

responsibility to ensure events like the dust bowl never happen again. 

While this Committee cannot control the weather, we can prioritize investments 

in basic science and energy research that will revolutionize the global energy 

market. 

America led the world in coal, oil, and gas. Now we must lead again, and 

partner with industry to develop breakthrough energy technologies and make 

our existing energy sources cleaner and more affordable. I thank our witnesses 

for being here today and I yield the balance of my time. 
16 

Chairwoman JOHNSON. Thank you very much, Mr. Lucas. 

If there are Members who wish to submit additional opening 

statements, your statements will be added to the record at this 

point. 

At this time I’d like to introduce our witnesses. Our first witness 

is Dr. Natalie Mahowald, the Irving Porter Church Professor of Engineering, and the Faculty Director for the Environment of the Atkinson Center for a Sustainable Future at Cornell University. Due 

to the weather-related travel delays, she’s joining us through a 

video link from Ithaca, New York. Her research looks at natural 

feedbacks in the climate system, and Dr. Mahowald was the lead 

author on the IPCC Special Report on 1.5 °C Global Warming 

released last year and the IPCC Fifth Assessment from Working 

Group 1 on the physical science of climate change in 2013. 

She received her Ph.D. in meteorology from the Massachusetts 

Institute of Technology, and we now will recognize—she’ll be our 

first witness. 

Our second witness is Dr. Robert Kopp, who is Director of Rutgers Institute of Earth, Ocean, and Atmospheric Sciences, and Professor in the Department of Earth and Planetary Sciences at Rutgers University. He also serves as Co-Director of Rutgers’ Coastal 

Climate Risk and Resilience Initiative. Dr. Kopp’s research focuses 

on past and future sea-level change and the utilization of climate 

risk information and decisionmaking. He is a lead author of volume 

1 of the Fourth National Climate Assessment (NCA 4) released last 

year and the IPCC’s Sixth Assessment Report, which is due out in 

2021. 

Dr. Kopp received his Ph.D. in geobiology from the California Institute of Technology. 

Our third witness, Dr. Jennifer Francis, who is a Senior Scientist 

at the Woods Hole Research Center. Dr. Francis’ research focuses 

on climate change impacts in the Arctic and how that affects 

weather around the world, especially how a warming Arctic may 

lead to a weakened jet stream. Dr. Francis is regularly quoted in 

media outlets. 

Dr. Francis received her Ph.D. in atmospheric sciences from the 

University of Washington. 

Our fourth witness is Dr. Joseph Majkut from the Niskanen Center. He is an expert on climate science policy, and risk and uncertainty analysis for decisionmaking, and is frequently cited by 

media outlets on climate scientific research. 

He received his Ph.D. in atmospheric and oceanic sciences from 

Princeton University. 

Our final witness, Dr. Kristie Ebi, who is the Director of the Center for Health and the Global Environment, or CHanGE program, 

and the Rohm and Haas Endowed Professor in Public Health 

Sciences at the University of Washington. Dr. Ebi’s research includes estimating current and future health risks of climate change 

and estimating the health co-benefits of mitigation policies and 

technologies. Dr. Ebi was the chapter lead on the Human Health 

Chapter, volume 2, of the Fourth National Climate Assessment released last year. She also co-chairs the National Academies Committee to Advise a U.S. Global Change Research program. 
17 

Dr. Ebi received her Ph.D. in epidemiology from the University 

of Michigan. 

As our witnesses shall know, you will each have 5 minutes for 

your spoken testimony. Your written testimony will be included in 

the record of the hearing. When all of you have completed your spoken testimony, we will begin a round of questions. Each Member 

will have 5 minutes to question the panel. 

And we will start with a witness that is appearing on the screen, 

Dr. Mahowald. 

[Audio malfunction in hearing room.] 

Chairwoman JOHNSON [continuing]. We can’t—let’s go to Dr. 

Kopp and then return when we get the technology working. 

TESTIMONY OF DR. ROBERT KOPP, 

DIRECTOR, RUTGERS INSTITUTE OF EARTH, OCEAN, 

AND ATMOSPHERIC SCIENCES, 

AND PROFESSOR, DEPARTMENT OF EARTH AND 

PLANETARY SCIENCES, RUTGERS UNIVERSITY 

Dr. KOPP. All right. Well, thank you, Chairwoman Johnson, 

Ranking Member Lucas, and Committee Members for inviting me 

to speak today. My name is Robert Kopp. I am the Director of the 

Rutgers Institute of Earth, Ocean, and Atmospheric Sciences and 

a Professor at Rutgers University. My research focuses on past and 

future sea-level change and on the interactions between climate 

change and the economy. 

I served as one of the 29 lead authors of the fourth volume—of 

the first volume of the Fourth National Climate Assessment, and 

I was invited here to speak to the fourth assessment. I should note 

that I’m doing so in my personal capacity, not to represent the U.S. 

Global Change Research Program or Rutgers. 

The Fourth National Climate Assessment provides an up-to-date 

assessment of the scientific understanding of climate change, its 

current effects on the United States, and its potential future impacts. It draws out key findings from the massive body of peer-reviewed science to support scientifically informed climate risk management. Its first volume focuses on the physical science; the second on impacts, risks, and adaptation. The report’s nearly 2,000 

pages are data-driven and extensively referenced. Both volumes 

underwent detailed transparent review processes, including open 

reviews by external experts in the general public and thorough reviews by independent experts convened by the National Academies. 

The process of drafting the National Climate Assessment was 

painstaking and complex, but its fundamental findings are simple 

and urgent. First, climate change is real, it is happening now, and 

humans are responsible for it. The planet is running a fever. Its 

average temperature has increased by nearly 2 °F since 1900 with 

humans responsible for essentially all of the warming since 1950. 

Second, climate change isn’t an issue for the distant future. It’s 

already affecting Americans in every region of the country. Across 

the country, heat waves are becoming more frequent, heavy rainfall 

more intense, and coastal flooding more common as a result of climate change and sea-level rise. Studies show that climate change 

intensified the dry hot summer of 2011 in Texas and Oklahoma, 
18 

the recent drought in California, and the rainfall of Hurricane Harvey in 2017. 

Third, climate change is not just an environmental challenge. It’s 

an economic challenge, an infrastructure challenge, a public-health 

challenge, and a national-security challenge. As the report notes, 

and I quote, ‘‘In the absence of more significant global mitigation 

efforts, climate change is projected to impose substantial damages 

on the U.S. economy, human health, and the environment,’’ particularly in scenarios with limited adaptation. 

Fourth, every amount—every additional amount of greenhouse 

gas emitted makes climate change more severe. In order to stabilize global climate at any level, human—any level of warming, 

human emissions of carbon dioxide must be brought as close to zero 

as possible with any continued emission of CO2 balanced by human 

removal of carbon dioxide from the atmosphere, whether that’s by 

expanding forests or using new, little-tested technologies. In other 

words, to stabilize the global climate, net global carbon dioxide 

emissions must be brought to zero. The faster we reduce our emissions, the less severe the effects and the lower the risk of unwelcome surprises. 

Fifth, though the pace is not yet adequate to minimize climate 

risk, Americans are already starting to respond by reducing emissions and beginning to adapt to climate-change impacts. As the report notes, 110 cities, several States, and an increasing number of 

companies have adopted emissions-reduction targets. The report 

highlights adaptation planning efforts by cities and transport systems, the use of innovative farming techniques to deal with wet 

and dry extremes, and efforts to measure—to manage water scarcity in places like the Colorado River basin and Texas’ Edwards 

Aquifer. These mitigation and adaptation efforts need to grow dramatically and rapidly to effectively manage climate risk. 

In conclusion, the National Climate Assessment shows that climate change is real, it’s here, and we humans are responsible for 

it. To stabilize the global climate, we need to bring net global 

greenhouse gas emissions to zero. The sooner we do this, the smaller the risks to our economy, health, infrastructure, and security 

that we will have to manage. But even with strong emissions reductions, there will still be major adaptation challenges ahead. It’s 

therefore essential that climate change become a routine and integrated part of decisionmaking at all levels, public and private, Federal, State, and local. 

Thank you for holding this important hearing today. It’s my hope 

that, as the Science Committee, you will look closely at how to advance the climate science enterprise in a manner that supports climate risk management. 

[The prepared statement of Dr. Kopp follows:] 
19 

Statement of 

Robert E. Kopp 

Professor, Department of Earth and Planetary Sciences 

Director, Rutgers Institute of Earth, Ocean, and Atmospheric Sciences 

Rutgers University- New Brunswick 

before the 

Committee on Science, Space, and Technology 

U.S. House of Representatives 

February 12, 2019 

1\YTGERS 

Institute of Earth, Ocean, and 

Atmospheric Sciences 
20 

Thank you, Chairwoman Johnson, Ranking Member Lucas, and committee members for inviting 

me to speak today. 

My name is Robert Kopp. I am the Director of the Rutgers Institute of Earth, Ocean, and 

Atmospheric Sciences1 and a Professor in the Department of Earth and Planetary Sciences at 

Rutgers University-New Brunswick. I also serve as co-director of Rutgers' Coastal Climate Risk 

& Resilience (C2R2) initiative, which trains graduate students to work together across 

disciplines and with stakeholders to address coastal resilience challenges. I am also one of the 

directors of the Climate Impact Lab2, a multi-institutional collaboration applying climate 

modeling and Big Data approaches to assess the economic risks of climate change. My research 

focuses on past and future sea-level change, on the interactions between physical climate change 

and the economy, and on the use of climate risk information in decision making. 

I served as one of the twenty-nine lead authors of Volume 1 of the Fourth National Climate 

Assessment (NCA). I am also currently serving as a lead author of the Sixth Assessment Report 

of the Intergovernmental Panel on Climate Change, which is due out in 2021. 

While the bulk of my testimony is focused on presenting the findings of the Fourth NCA, I am 

speaking on my own behalf. My testimony is not itself a product of the assessment process, nor 

does it necessarily represent the positions of the US Global Change Research Program or of 

Rutgers University. I also would like to note that I was not one of the three coordinating lead 

authors who oversaw Volume 1, nor was I an author of Volume 2. My comments on Volume 2 

are based on my technical contributions and my reading of it as a climate scientist who is up to 

date with in much of the relevant literature. 

The National Climate Assessment process 

In 1990, President George H. W. Bush signed the Global Warming Response Act of !990, which 

established the interagency U.S. Global Change Research Program (USGCRP) under the 

auspices of the National Science and Technology Council's Subcommittee on Global Change 

Research. One of the key tasks of the USGCRP was to undertake a quadrennial National Climate 

Assessment, which "I) integrates, evaluates, and interprets the findings of the Program ... ; 2) 

analyzes the effects of global change on the natural environment, agriculture, energy production 

and use, land and water resources, transportation, human health and welfare, human social 

systems, and biological diversity; and 3) analyzes current trends in global change, both humaninduced and natural, and projects major trends for the subsequent 25 to 100 years."3 

The first NCA was released by USGCRP in the year 2000; the second in 2009; and the third in 

2014. The Fourth NCA was developed in two volumes: the first volume, published in 2017, 

focusing on the physical science, and the second volume, in 2018, on Impacts, Risks, and 

Adaptation. The report is data-driven and transparent, with nearly 2000 extensively referenced 

pages and key findings backed by detailed traceable accounts. 

1 For more information: eoas.rutgers.edu 2 For more information: impactlab.org 3 Global Change Research Act of 1990. Pub. L. No. 101-606, 104 Stat. 3096-3104, November 16, 1990. 

https://go.usa.gov/xESJs. 

2 
21 

Both volumes underwent extensive review processes involving an open review by external 

experts and the general public, a thorough review by independent experts convened by the 

National Academies of Sciences, Engineering, and Medicine, and multiple rounds of interagency 

review. Report authors provided written responses to all the review comments, which are 

available online for the external and National Academies reviews. 

Climate science is a massive enterprise; while at a global scale, the fundamentals are well 

established, and in many cases have been known for many decades, even over a century, the 

scientific understanding of the details is rapidly evolving. 

As the periodic nature of the NCA reports reflects, the goal of the NCA process is to provide an 

up-to-date assessment of the scientific understanding of climate change, its current effects on the 

United States, and its potential future impacts across a broad range of emissions scenarios. It 

considers a broad range of possible futures, from one in which fossil fuel use and emissions 

continue to grow to one in which emissions are rapidly reduced and reach zero before the end of 

the century. 

Key messages ofthe Fourth National Climate Assessment 

The National Climate Assessment draws out key findings from the massive body of peerreviewed science in order to support scientifically informed climate risk management by federal, 

state, local, and private-sector decision-making. In addition, by identifYing key decision-relevant 

uncertainties, it can also help direct scientific inquiry toward decision-relevant ends. 

The most fundamental messages of Volume l of the report are simple, and they are not novel: 

I) Climate change is real, it is here now, and humans are responsible for it. 

2) Every additional amount of greenhouse gas emitted makes climate change more 

severe. 

3) The faster we reduce our emissions, the less severe the effects and the lower the risk 

of unwelcome surprises. 

Volume 2 expands upon the human consequences of climate change and how the US is 

responding to them. It tells us that: 

I) Climate change is not an issue for the distant future - it is already affecting 

Americans in every region of the country. 

2) Climate change is not just an environmental challenge; it is an economic challenge, 

an infrastmcture challenge, a public health challenge and a national security 

challenge. 

3) Though the pace is not yet adequate to minimize climate risk, Americans are already 

starting to respond by reducing emissions and beginning to adapt to climate change 

impacts. 

3 
22 

Let me expand upon these points. 

Climate change is real, it is here now, and humans are responsible for it. 

Our planet is running a fever. 

To quote the NCA: 

Global climate is changing rapidly compared to the pace of natural variations in climate 

that have occurred throughout Earth's history. Global average temperature has increased 

by about 1.8°F from 1901 to 2016, and observational evidence does not support any 

credible natural explanations for this amount of warming; instead, the evidence 

consistently points to human activities, especially emissions of greenhouse or heattrapping gases, as the dominant cause.4 

Global average carbon dioxide concentration are now about 410 parts per million- nearly 50% 

higher than they were at the start of the Industrial Revolution, and a level not seen on this planet 

for at least about three million years. Carbon dioxide's role as a heat-trapping gas has been 

known since the discoveries of Eunice Foote and John Tyndall in the mid~ 19th century. Thus, a 

warming planet should be entirely expected. 

In contrast, to quote the NCA, 

Solar output changes and internal natural variability can only contribute marginally to the 

observed changes in climate over the last century, and there is no convincing evidence for 

natural cycles in the observational record that could explain the observed changes in 

climate.5 

It is likely- a term the NCA uses to mean a chance of at least two in three- that the human 

contribution to global warming over 1951-2010 is between 93 to 123 percent. (Values larger 

than 100 percent reflect that, in the absence of human emissions, the planet might actually have 

cooled over this time period.) 

Further, "Thousands of studies conducted by researchers around the world have documented 

changes in surface, atmospheric, and oceanic temperatures; melting glaciers; diminishing snow 

cover; shrinking sea ice; rising sea levels; ocean acidification; and increasing atmospheric water 

vapor."6 

"Heat waves have become more frequent in the United States since the 1960s, while 

extreme cold has become less frequent."7 

4 K. Hay hoe et al., Our Changing Climate, in IMPACTS, RISKS, AND ADAPTATION IN THE UNITED STATES: FOURTH 

NATIONAL CLIMATE AsSESSMENT, VOLUME II 72-144,73 (D. R. Reidmiller et al. eds., 2018), 

doi:I0.7930/NCA4.2018.CH2. 

5 D. J. Wuebbles et al., Executive summary, in CLIMATE SCIENCE SPECIAL REPORT: FOURTH NATIONAL CLIMATE 

ASSESSMENT, VOLUME l I ~34, 14 (D. J. Wuebbles et al. eds., 2017), doi: I 0. 7930/JODJ5CTG. 6 Id at 10. 7 ld at II. 

4 
23 

"Heavy rainfall is increasing in intensity and frequency across the United States."8 

Higher temperatures are making soil drier, contributing to the intensity of droughts.9 

Global average sea level has risen by about 8 inches since 1900,10 and recent work 

published since Volume I of the NCA was completed shows that global average sea level 

is now rising at more than 1.5 inches per decade - close to three times the average rate 

over the last century. 11 This has led to an increase in the frequency of coastal flooding: 

frequencies that, in some cities, have increased by a factor often since the middle of the 

last century .

12 

Every additional amount of greenhouse gas emitted makes climate change more severe. 

In the words of the NCA, 

The magnitude of climate change beyond the next few decades will depend primarily on 

the amount of greenhouse gases (especially carbon dioxide) emitted globally. Without 

major reductions in emissions, the increase in annual average global temperature relative 

to preindustrial times could reach 9°F (5°C) or more by the end of this century. With 

significant reductions in emissions, the increase in annual average global temperature 

could be limited to 3.6°F (2°C) or lessY 

To a first approximation, carbon dioxide warms the planet in proportion to the total amount 

emitted - every ton of C02 emitted increases the planet's temperature a little, every trillion tons 

by about 0.4°-l.2°F (0.2-0.7°C).14 As a reference, current global armual C02 emissions are 

about 42 billion tons, 15 so if C02 emissions were frozen at the current levels, we would expect 

global average temperature to increase by about l °F every 25 years - in fact, somewhat faster 

due to the effects of greenhouse gases other than COz. 

The COz warming is extremely long-lived- most of it happens within a decade or two of 

emission, and most of it persists for well over a millennium. 16 

The consequence of these physical relationships is that, in order to stabilize global climate, 

human emissions of C02 must be balanced by human removal of C02 from the atmosphere, 

8 /dat11. 

9 M. F. Wehner eta!., Droughts, Floods, and Wildfires, in CLIMATE SCIENCE SPECIAL REPORT: FOURTH NATIONAL 

CLIMATE ASSESSMENT, VOLUME I 231-256 (D. J. Wuebbles eta!. eds., 2017). 10 William V. Sweet et al., Sea level rise, in CLIMATE SCIENCE SPECIAL REPORT: FOURTH NATIONAL CLIMATE 

ASSESSMENT, VOLUME I 333-363 (D. J. Wuebbles et al. eds., 2017). 11 WCRP Global Sea Level Budget Group, Global sea-level budget 1993-present, 10 EARTH SYSTEM SCIENCE 

DATA 1551-1590 (2018). 12 Sweet et al., supra note I 0. 13 Wuebbles et al., supra note 5 at II. 14 Matthew Collins, Reto Knutti & others, Chapter 12: Long-term Climate Change: Projections, Commitments and 

Irreversibility, in CLIMATE CHANGE 2013: THE PHYSICAL SCIENCE BASIS , 12 (Thomas F. Stocker, Dabe Qin, & 

others eds., 2013), http://www.ipcc.ch/report/ar5/wgll. 15 Corinne Le Quere et al., Global Carbon Budget 2018, !0 EARTH SYSTEM SCIENCE DATA 2141-2194 (2018). 16 F. Joos et al., Carbon dioxide and climate impulse response functions for the computation of greenhouse gas 

metrics: a multi-model analysis, 13 ATMOSPHERIC CHEMISTRY AND PHYSICS 2793-2825 (20 13). 

5 
24 

whether by expanding forests or using new, little-tested technologies. In other words, to stabilize 

global climate, net global C02 emissions must be brought to zero. 

The faster we reduce our emissions, the less severe the effects and the lower the risk of 

unwelcome surprises. 

For example, rapid emission reductions could limit warming this century over the contiguous 

United States to about l-5°F, whereas sustained emissions growth could lead to 6-l2°F of 

warming- with extreme high temperatures rising even faster. 17 Similarly, global average sea 

level rise this century will very likely be less than 3 feet in a low-emissions future, whereas a 

high-emissions future raises the odds on extreme Antarctic instability, potentially leading to 6 

feet or more of rise over the course of this century. 18 

And the less we push the Earth's climate from the historical conditions that gave birth to modem 

civilization, the lower the odds that it will surprise us in potentially dangerous ways. 19 

The first volume's final chapter, which I helped lead, offers a perspective on the way the climate 

system might surprise us, and comes to three key conclusions: 

First, one way the climate system might surprise us is through the cumulative effects of multiple, 

or 'compound' extreme events- for example simultaneous heat and drought, wildfires associated 

with hot and dry conditions, flooding associated with high precipitation on top of snow or 

waterlogged ground, or-to take one recent and now sadly familiar example- multiple severe 

hurricanes in quick succession. The human impacts of these compound extremes can be larger 

than that of the individual extremes in isolation. This area is an emerging area of research that is 

just now starting to come into focus; thus the potential for surprises. 

Second, both modeling and geological records of past climate changes demonstrate that selfreinforcing cycles "within the climate system have the potential to accelerate human-induced 

climate change and even shift the Earth's climate system, in part or in whole, into new states that 

are very different from those experienced in the recent past- for example, ones with greatly 

diminished ice sheets or different large-scale patterns of atmosphere or ocean circulation."20 It is 

such feedbacks that undergird the potential for high-end sea-level rise mentioned earlier. 

Third, comparison of the geological record and climate model simulations reveal another insight. 

Climate models often have difficulty reproducing past warm climates, which we can learn about 

from the geological record. In the words of the NCA, "The systematic tendency of climate 

models to underestimate temperature change during warm paleoclimates suggests that climate 

models are more likely to underestimate than to overestimate the amount of long-term future 

change."21 For example, some of the reconstructions of past warm periods from the geological 

record may be explained if, above some threshold of C02 higher than the current level, 

17 R. S. Vose et al., Temperature changes in the United States, in CLIMATE SCIENCE SPECIAL REPORT: FOURTH 

NATIONAL CLIMATE ASSESSMENT, VOLUME I 185-206 (D. J. Wuebbles eta!. eds., 2017), doi: 10.7930/JON29V45. 

" Sweet eta!., supra note I 0; Robert E. Kopp et al., Evolving understanding of Antarctic ice-sheet physics and 

ambiguity in probabilistic sea-level projections, 5 EARTH'S FUTURE 1217-1233 (20 17). 19 Robert E. Kopp et al., Potential surprises- compound extremes and tipping elements, in CLIMATE SciENCE 

SPECIAL REPORT: FOURTH NATIONAL CLIMATE ASSESSMENT, VOLUME I 411-429 (D. J. Wuebbles eta!. eds., 2017). 20 ld at411. 21 Id. at 411. 

6 
25 

widespread reductions in cloud cover increases the sensitivity of the climate to greenhouse gases 

-a possibility pointed to by a few studies.22 

These large scale, global effects are important, but nobody lives at the global or national average 

everyone lives somewhere, and Volume 2 looks at the human effects of these changes. 

Climate change is not an issue for the distant future- it is already affecting Americans in 

every region of the country. 

To help with planning at a state and local level, the report details impacts and adaptation 

measures in ten regions covering the United States and its affiliated islands. For example, as 

Hurricanes Harvey and Irma reminded us, 

The Southeast's coastal plain and inland low-lying regions support a rapidly growing 

population, a tourism economy, critical industries, and important cultural resources that 

are highly vulnerable to climate change impacts. The combined effects of changing 

extreme rainfall events and sea level rise are already increasing flood frequencies, which 

impacts property values and infrastructure viability, particularly in coastal cities. Without 

significant adaptation measures, these regions are projected to experience daily high tide 

flooding by the end of the century.23 

Scientists are increasingly able to evaluate the ways in which climate change is making weather 

more extreme. For example, studies show that climate change intensified the dry, hot summer of 

2011 in Texas and Oklahoma and the 2012-2017 drought in California. A warm, moisture-laden 

atmosphere led to more intense rainfall during Hurricane Harvey in 2017- as much as 38% more 

rain, one study estimated, over the entire duration of the storm. 24 And sea-level rise has made 

every severe coastal flood, including that of Hurricane Sandy in 2012, more intense and 

damaging.25 Sensitive assets like roads, hospitals, power plants, and contamination sites are 

increasingly frequently threatened. 26 

Climate change is not just an environmental challenge; it is an economic challenge, an 

infrastructure challenge, a public health challenge and a national security challenge. 

The National Climate Assessment notes, drawing in part on my work with my collaborators in 

the Climate Impact Lab, that "in the absence of more significant global mitigation efforts, 

climate change is projected to impose substantial damages on the U.S. economy, human health, 

and the environment. Under scenarios with high emissions and limited or no adaptation, annual 

22 For example, Rodrigo Caballero & Matthew Huber, State-dependent climate sensitivity in past warm climates and 

its implications for fttture climate projections, 110 PNAS 14162-14167 (2013). 23 L. Carteret al., Southeast, in IMPACTS, RISKS, AND ADAPTATION IN THE UNITED STATES: FOURTH NATIONAL 

CLIMATE ASSESSMENT, VOLUME II 743-808, 744 (D. R. Reidmiller et al. eds., 2018), doi: 

10.7930/NCA4.20!8.CH19. 

24 Wehner et al., supra note 9; Vose et al., supra note 17. 25 Kenneth G. Miller eta!., A geological perspective on sea-level rise and its impacts along the US. mid-Atlantic 

coast, I EARTH'S FuTuRE 3-18 (2013). 26 K. Kloese] et al., Southern Great Plains, in IMPACTS, RISKS, AND ADAPTATION IN THE UNITED STATES: FOURTH 

NATIONAL CLIMATE ASSESSMENT, VOLUME II 987-1035 (D. R. Reidmiller eta!. eds., 2018), doi: 

10.7930/NCA4.2018.CH23. 

7 
26 

losses in some sectors are estimated to grow to hundreds of billions of dollars by the end of the 

century. "27 

The report notes that "the health and well-being of Americans are already affected by climate 

change, with the adverse health consequences projected to worsen with additional climate 

change. Climate change affects human health by altering exposures to heat waves, floods, 

droughts, and other extreme events; vector-, food- and waterborne infectious diseases; changes in 

the quality and safety of air, food, and water; and stresses to mental health and well-being."28 

And it notes that "Climate change, variability, and extreme events, in conjunction with other 

factors, can exacerbate conflict, which has implications for U.S. national security. Climate 

impacts already affect U.S. military infrastructure, and the U.S. military is incorporating climate 

risks in its planning." 29 

This finding about national security impacts is echoed by the US Intelligence Community's most 

recent Worldwide Threat Assessment, which notes that "Global enviromnental and ecological 

degradation, as well as climate change, are likely to fuel competition for resources, economic 

distress, and social discontent through 2019 and beyond."30 

Though the pace is not yet adequate to minimize climate risk, Americans are already starting 

to respond by reducing emissions and beginning to adapt to climate change impacts. 

In terms of mitigation, for example, the report notes that 110 cities have adopted emissions 

reduction targets; several states have mandatory or voluntary targets; and an increasing number 

of companies are implementing emissions reduction target and internal carbon prices as well. 

In terms of adaptation, the report highlights a multitude of examples from around the country. 

For example, it notes municipal adaptation planning efforts for climate change and/or more 

frequent flooding in New York City, Boston, Atlanta, and Charleston.31 Transport systems like 

the Port Authority of New York and New Jersey and the Metropolitan Atlantic Rapid Transit 

Authority are building climate resilience into their infrastructure plans.32 In the Midwest, the 

report highlights the use of cover crops and water management systems to limit soil erosion in 

response to more intense rains, as well as the use of green infrastructure to handle stormwater in 

27 J. Martinich et al., Reducing Risks Through Emissions Mitigation, in IMPACTS, RISKS, AND ADAPTATION IN THE 

UNITED STATES: FOURTH NATIONAL CLIMATE ASSESSMENT, VOLUME II 1346-1386, 1347 (C. W. Avery et al. eds., 

2018), doi: 10.7930/NCA4.2018.CH29. 28 K. L. Ebi et al., Human Health, ill IMPACTS, RISKS, AND ADAPTATION IN THE UNITED STATES: FOURTH NATIONAL 

CLIMATE AsSESSMENT, VOLUME II 572--603,540 (D. R. Reidmilleret al. eds., 2018), doi: 

10.7930/NCA4.2018.CH14. 

29 J. B. Smith et al., Climate Effects on US. International interests, in IMPACTS, RISKS, AND ADAPTATION IN THE 

UNITED STATES: FOURTH NATIONAL CLIMATE ASSESSMENT, VOLUME II 604-637, 605 (C. W. Avery et a!. eds., 

2018), doi: 10.7930/NCA4.2018.CHI6. 30 DANIEL R. COATS, WORLDWIDE THREAT ASSESSMENT OF THE US INTELLIGENCE COMMUNITY 23 (2019), 

https:l/www.dni.govlfiles/ODNI/documents/20 19-A T A-SFR---SSCI.pdf. 31 L. A. Dupigny-Giroux et al., Northeast, in IMPACTS, RISKS, AND ADAPTATION IN THE UNITED STATES: FOURTH 

NATIONAL CLIMATE ASSESSMENT, VOLUME II 669-742 (D. R. Reidmiller et al. eds., 2018), doi: 

l0.7930/NCA4.20!8.CH18; Carteret al., supra note 23. 32 Dupigny-Giroux et al., supra note 31; Carteret al., supra note 23. 

8 
27 

cities like St. Louis and Minneapolis.33 On the west coast, the report highlights the growing use 

of dry fanning methods in places like Oregon's Willamette Valley, as well as the growing 

number of Native American nations that have begun to consider relocation as a last resort.34 In 

the Southwest, it highlights the multistate, binational efforts to manage Colorado River waters.35 

In Texas, the Edwards Aquifer Recovery Implementation Program Habitat Conservation 

Program - addressing the aquifer that provides water to San Antonio, San Marcos, and Austin -

incorporates advanced water conservation and market-based solutions for dealing with 

groundwater pumping during droughts. Forty-four public water supply desalination plants in 

Texas are helping increase water supply in times of drought.36 

Scientific uncertainty and climate risk management 

Uncertainty is integral to science, and one of the main drivers of scientific pursuits. There is a 

strong tendency among scientists to focus on what is new, tantalizing, and unknown, rather than 

what is old and well understood. 

In the world of scientific assessments, a great deal of effort has gone into formalizing language 

for evaluating what is known and how well it is known. The National Climate Assessment, like 

the Intergovernmental Panel on Climate Change, uses a set of specific definitions for terms like 

'likely,' 'very likely', and 'virtually certain.' For example, 'likely' means 'at least two chances in 

three,' 'very likely' means 'at least nine chances in ten', and 'virtually certain' means 'at least 

ninety-nine changes in one-hundred.' These judgements of likelihood are based upon an expert 

evaluation that looks across the available scientific literature. 

Similarly, these assessments have defined a set of formal language to characterize the strength of 

the relevant evidence. For example, 'very high confidence' conclusions have strong evidence, for 

example based on well-established theory, multiple sources with consistent results, and well 

accepted methods. 'Medium confidence' conclusions have suggestive evidence (e.g., a few 

sources with limited consistency using emerging methods). 'Low corifidence' conclusions are 

used to highlight areas of inconclusive evidence, inconsistent findings, and limited agreement on 

methods and conceptual frameworks. 

Here are some examples from the first volume of the Fourth NCA: 

Global annual average temperature (as calculated from instrumental records over both 

land and oceans) has increased by more than l.2°F (0.65°C) for the period 1986-2016 

relative to 190 1-1960; the ... change over the entire period from 190 1-2016 is l.8°F 

(l.0°C) (very high corifidence[).]37 

Many lines of evidence demonstrate that it is extremely likely that human influence has 

been the dominant cause of the observed warming since the mid-20th century. Over the 

33 J. Angel et al., Midwest, in IMPACTS, RISKS, AND ADAPTATION lN THE UNITED STATES: FOURTH NATIONAL 

CLIMATE AsSESSMENT, VOLUME II 872-940 (D. R. Reidmiller et al. eds., 2018), doi: 10.7930/NCA4.2018.CH2l. 34 C. May eta!., Northwest, in IMPACTS, RISKS, AND ADAPTATION IN THE UNITED STATES: FOURTH NATIONAL 

CLIMATE ASSESSMENT, VOLUME II 1036-1100 (D. R. Reidmilleret al. eds., 2018), doi: 10.7930/NCA4.2018.CH24. 35 P. Gonzalez et al., Southwest, in IMPACTS, RISKS, AND ADAPTATION lN THE UNITED STATES: FOURTH NATIONAL 

CLIMATE ASSESSMENT, VOLUME II 1101-1184 (D. R. Reidmiller et al. eds., 2018), doi: 10.7930/NCA4.2018.CH25. 36 Kloesel et al., supra note 26. 37 Wuebbles et al., supra note 5 at 13. 

9 
28 

last century, there are no convincing alternative explanations supported by the extent of 

the observational evidence. Solar output changes and internal natural variability can only 

contribute marginally to the observed changes in climate over the last century, and there 

is no convincing evidence for natural cycles in the observational record that could explain 

the observed changes in climate. (Very high confidence)38 

The frequency and intensity of heavy precipitation events in the United States are 

projected to continue to increase over the 21st century (high confidence). There are, 

however, important regional and seasonal differences in projected changes in total 

precipitation: the northern United States, including Alaska, is projected to receive more 

precipitation in the winter and spring, and parts of the southwestern United States are 

projected to receive less precipitation in the winter and spring (medium confidence).39 

Relative to the year 2000, [global average sea level] is very likely to rise by 0.3-0.6 feet 

(9-18 em) by 2030,0.5-1.2 feet (15-38 em) by 2050, and 1.0-4.3 feet (30-130 em) by 

2100 (very high corifidence in lower bounds; medium corifidence in upper bounds for 

2030 and 2050; low confidence in upper bounds for 2100).40 

For effective climate risk management, it's important to consider not only high-confidence 

conclusions, but also low-confidence ones. Low-confidence conclusions are often associated 

with areas subject to what is sometimes called 'deep uncertainty': areas where there is little 

agreement among experts about the relative importance of different processes or likely values of 

key variables. 41 In many cases, deep uncertainty is associated with what the report also calls 

'potential surprises.' 

An archetypal example of this, given the current scientific understanding, involves the behavior 

of the Antarctic ice sheet late in this century and beyond. As the report notes, "Emerging science 

regarding Antarctic ice sheet stability suggests that, for high emission scenarios, a [global 

average sea level] rise exceeding 8 feet (2.4 m) by 2100 is physically possible, although the 

probability of such an extreme outcome cannot currently be assessed."42 This deep uncertainty 

arises in large part from expert disagreement about the importance of different processes that can 

give rise to self-reinforcing cycles leading to relatively rapid ice-sheet loss. 

What does the presence of deep uncertainty mean for risk management?43 

Consider two dice games, played against the house (in this case, Mother Nature). In both games, 

there is a large pot on the table, representing assets at risk, and you have no choice but to play the 

game. 

In the first game, if you roll snake-eyes on a pair of dice, you lose the pot; otherwise you keep it. 

Thus, there is a well-defined, 1-in-36 chance of losing. A risk-neutral player should be willing to 

38 ld at 14. 39 /dat21. 

40 Sweet et al., supra note 10 at 333. 41 Robert J. Lempert, A new decision sciences for complex systems, 99 PNAS 7309-7313 (2002). 42 Sweet et al., supra note I 0 at 333. 43 The remainder of this section of my written testimony is based on my own research and experience, not on the 

Fourth National Climate Assessment. 

10 
29 

spend l/36'h of the pot to insure the rest. In the game, this expenditure might be a side bet; with 

respect to sea-level rise, it might represent investment in protective measures against global 

mean sea-level rise exceeding 1.2 feet by 2050. 

In the second game, Mother Nature has written a number between 2 and 7 on a piece of a paper 

you cannot see. If you roll above this number, you get to keep the pot; if you do not, you lose it. 

This game exhibits deep uncertainty: different expert players might have different conceptual 

models underlying how this number was selected and may not agree on how likely different 

numbers are. 

You definitely would not play this game the same way you would play the first game deep 

uncertainty does not justify assuming the most optimistic possible state of the world. Unless you 

are extremely risk averse, you probably also would not play the game the same way you would if 

you knew for certain a seven was written down; if you did that, there is a fair chance you would 

lose a good deal, though not as much as if you were too optimistic. 

This second game is roughly analogous to the current state of understanding of the prospect of 

global average sea-level rise between 4 and 8 feet over this century under a high-emissions 

future. 

Fortunately, we are not playing a one-shot game. Sea-level rise takes place over time, and we 

will not get 8 feet of sea-level rise tomorrow. Scientific understanding is evolving, and it is quite 

possible that within thirty years research will reveal what number is written on that sheet of 

paper. It might also turn out within thirty years that we are on course for a low-emissions future, 

in which case the uncertainty will be less deep and more closely resemble that of the first game. 

Many decisions have a timeframe within the next thirty years and are not affected by this deep 

uncertainty in sea-level rise. Other decisions may require action now for the long-term. For 

instance, the existing rail tunnels under the Hudson River are about a century old. In building a 

new tunnel - a process that is slow and yields a product that may well last for over a century - it 

may be more cost-effective to build now for high-end sea-level rise rather than trying to retrofit 

if it turns out in a couple decades that the world is on course for a high-end rise. 

Still other decisions permit staged, adaptive management: take action for the next thirty years but 

know now what follow-on actions you will take depending on what number turns out to be 

written down. This last approach may be the best for jointly minimizing climate and investment 

risk when managing complex systems, such as the portfolio of actions required to protect coastal 

populations from sea-level rise. 

This last approach of adaptive management is also known in the literature as a 'flexible 

adaptation pathways' approach. A key part of such approaches is the inclusion of research 

investments focused on narrowing key uncertainties as one part of a portfolio of risk 

management strategies. Another key part is drawing up contingency plans for different possible 

futures in advance and mapping out which future discoveries will trigger which actions. 

Managing climate risk in this way requires long-term, sustained investment in research that cuts 

across the disciplinary boundaries of climate science, social science, engineering, and decision 

science. 

1l 
30 

Advancing the climate science enterprise for climate risk management44 

The recognition of the urgent need for scientific knowledge to inform action has led to the 

development of what is sometimes called 'transdisciplinary' science.45 Transdisciplinary science 

brings researchers from different disciplines together with stakeholders to tackle a common realworld problem. Transdisciplinary science is not necessarily applied research, as it may aim not 

only to translate existing understanding into practice but also to address some of the fundamental 

scientific uncertainties relevant to effective risk management. The tie to real-world problems is, 

however, a core element. 

Climate risk management calls out for such transdisciplinary research, as well as for educational 

initiatives preparing students to conduct such research. At Rutgers, we have a number of such 

efforts. For example, our Coastal Climate Risk and Resilience program46 trains graduate students 

to work with natural scientists, social scientists, engineers, urban planners, and stakeholders to 

manage coastal risk. The New Jersey Climate Change Alliance47 is a University-managed 

network of stakeholders that links scientific experts with local, state, and private decisionmakers. And we are a partner in the Climate Impact Lab, which is bringing climate scientists, 

economists, and data scientists together with stakeholders in state governments and the private 

sector to better integrate economic assessments of climate risk into regulatory and investment 

decisions. 

But true transdisciplinarity is hard - it requires a considerable investment on the part of 

researchers or their institutions in maintaining strong, working, trusting relationships with 

stakeholders. And building such relationships takes time- if it must be done from scratch, it does 

not fit well with the time pressures faced by pre-tenure faculty or graduate students. 

Right now, in the climate risk area, most transdisciplinary collaborations are driven by strong 

personalities or short-term funding opportunities. But the climate risk problem is not going to go 

away. Society is not well served if the networks that sustain such collaborations have to be 

rebuilt when individuals leave an institution or funding temporarily dries up. 

Fortunately, there is an example of academic institutions supporting transdisciplinary 

collaborations that has worked in the United States for over a century, long before the modem 

jargon of 'transdisciplinarity' was coined. 

In 1862, amidst the bloodshed of the Civil War, Abraham Lincoln signed the Morrill Act, 

establishing the United States' land-grant college system. The Morrill Act and follow-on 

legislation transformed higher education in the United States. They established a network of 

universities devoted to training the next generation of farmers and engineers, conducting 

innovative and useful research to advance agriculture, and engaging with farmers to disseminate 

the fruits of this research. The Smith-Lever Act of 1914 established cooperative extension 

44 This section of my written testimony is based on my own research and experience, not on the Fourth National 

Climate Assessment. 45 Gertrude Hirsch Hadom et al., The Emergence ofTransdisciplinarity as a Form of Research, in HANDBOOK OF 

TRANSDISCIPLINARY RESEARCH 19-39 (Gertrude Hirsch Hadorn et al. eds., 2008), https://doi.org/10.1 007/978-1-

4020-6699-3_2 (last visited Feb 6, 2019). 46 For more information: c2r2.rutgers.edu 47 For more information: njadapt.rutgers.edu 

12 
31 

services at land-grant institutions with the aim of bringing scientific knowledge about agriculture 

out of the universities and into the country. The cooperative extension services have placed 

agents in every US county and built networks of trust that link the land-grant institutions to the 

(primarily agricultural) community. 

It is worth considering an investment analogous to that of cooperative extension in expanding the 

infrastructure for scientific climate risk management. The unique advantage of land-grant 

universities is the extension tradition, upon which can be built robust networks to sustain 

stakeholder engagement in climate risk research and education. This requires support to shift the 

maintenance of stakeholder networks away from individual investigators and grants and to the 

institution. 

Building upon the extension strength also requires addressing countervailing incentives at the 

level of the individual scientist. Transdisciplinary research is inherently slower than more ivorytower research, requiring that researchers invest time in stakeholder engagement. More flexible 

tenure evaluation processes that recognize the value of this engagement can help advance this 

mission, and this shift would be assisted by appropriate nudges from funding agencies. 

In conclusion: 

The National Climate Assessment provides an extensively reviewed evaluation of a vast body of 

scientific literature. It shows that: 

Climate change is real, it is here, and we humans are responsible for it. To stabilize global 

climate, we need to bring net global greenhouse gas emissions to zero; the sooner we do this, the 

smaller the risks -to our economy, infrastructure, health, and national security -that we will 

have to manage. But even with strong emission reductions, there will still be major adaptation 

challenges ahead. It is therefore essential that climate change become a routine and integrated 

part of decision-making at all levels - public and private; federal, state, and local. 

Thank you for holding this hearing today. It's my hope that, as the Science Committee, you will 

look closely at both how to advance the climate science enterprise in a manner that supports 

climate risk management and also at how to support climate risk management that is 

scientifically informed. 

13 
32 

ROBERT E. KOPP is Director of the Rutgers Institute of Earth, Ocean, and Atmospheric 

Sciences and a Professor in the Department of Earth and Planetary Sciences at Rutgers 

University-New Brunswick. He also serves as co-director of Rutgers' Coastal Climate Risk & 

Resilience (C2R2) initiative, which trains graduate students to work together across disciplines 

and with stakeholders to address coastal resilience challenges, and as a director of the Climate 

Impact Lab, a multi-institutional collaboration applying climate modeling, econometrics, and Big 

Data approaches to assess the economic risks of climate change 

Professor. Kopp's research focuses on past and future sea-level change, on the interactions 

between physical climate change and the economy, and on the use of climate risk information in 

decision making. He is a lead author of Economic Risks of Climate Change: An American 

Prospectus (Columbia University Press, 2015), the Fourth National Climate Assessment, and the 

Intergovernmental Panel on Climate Change's Sixth Assessment Report. He has authored more 

than 80 peer-reviewed scientific journal articles, and his work has also appeared in popular 

venues, including the New York Times Sunday Review. 

Previously, he was Associate Director of the Rutgers Energy Institute, an AAAS Science & 

Technology Policy Fellow at the U.S. Department of Energy, and a postdoctoral fellow in 

geosciences and public policy at Princeton University. 

Professor Kopp is a fellow of the American Geophysical Union and a recipient of the American 

Geophysical Union's James B. Macelwane and William Gilbert Medals and the International 

Union for Quaternary Research (INQUA)'s Sir Nicholas Shackleton Medal. He has an 

undergraduate degree in geophysical sciences from the University of Chicago and a Ph.D. in 

geobiology from the California Institute of Technology. 
33 

Chairwoman JOHNSON. Thank you very much, Dr. Kopp. Do we 

have that ready yet? OK. We’ll move to Dr. Francis. 

TESTIMONY OF DR. JENNIFER FRANCIS, 

SENIOR SCIENTIST, WOODS HOLE RESEARCH CENTER 

Dr. FRANCIS. Good morning. My name is Jennifer Francis. I’m an 

atmospheric scientist at the Woods Hole Research Center in Massachusetts, and I study the connections between climate change and 

extreme weather. Thank you, Chairwoman Johnson and Members 

of the Committee, for the opportunity to testify here today. 

It’s not your imagination. Extreme weather events have become 

more frequent in recent decades. If we could have figure 1. 

[Slide.] 

Dr. FRANCIS. According to this analysis by Munich Re, one of the 

foremost reinsurance companies in the world, the occurrence of extreme weather events has nearly tripled since the 1980s. They are 

shown by the green, blue, and orange bars in this figure. 

Images of recent extreme weather events are etched into our 

memories: Neighborhoods flooded by feet of rain unleashed by Hurricanes Harvey and Florence, docks sitting high and dry in California’s reservoirs, and a sunken New Jersey roller coaster in the 

wake of Superstorm Sandy to name only a few. Yes, extreme 

weather has always happened, but there’s no question that it’s 

more vicious now, and all the signs point to it getting worse as the 

globe continues to warm under a thickening blanket of greenhouse 

gases. 

Before I go any further, let’s clear up a few definitions that sometimes cause confusion. Climate change versus global warming: Climate change means all the ways that the climate system is changing, while global warming is just one of those ways. Climate versus 

weather: Climate is the average of all the weather that occurs at 

a particular location, while weather is the day-to-day swings in 

temperature and precipitation. Think of climate as your personality 

and weather as your mood on any given day. 

The links between climate change and extreme weather are a hot 

topic of scientific research. Some of the connections are straightforward. For example, global warming is making heat waves more 

intense and persistent and therefore more deadly. And as the air 

and oceans warm, evaporation also increases, which fuels an uptick 

in heavy precipitation events. The warmer oceans are also fueling 

rapid intensification of tropical storms, and because sea level is 

higher, storm surges are doing more damage now. On a happier 

note, though, fewer low-temperature records are being broken. All 

of these changes are clearly tied to a warming planet. 

Other less straightforward connections are emerging as well. The 

polar vortex has been in the news a lot lately, so let’s start with 

winter extremes. The polar vortex is a frigid pool of air encircled 

by strong winds that sits up high above the Arctic only during winter. Recent studies suggest it has been weakening and deforming 

more often lately, and when that happens, extreme cold and hot 

temperatures strike the northern hemisphere. 

If I could at the next figure, please. 

[Slide.] 
34 

Dr. FRANCIS. This map of temperature departures during the recent Eastern cold snap demonstrates this clearly, so even though 

cold records are being broken less often, severe cold spells and heat 

waves will still happen. 

Turning southward, global warming appears to be widening the 

tropics. This may sound like a good thing, but it’s causing abnormal heat and drought in temperate regions such as Australia, 

southern California, and South Africa. We’re also learning that earlier spring snow melt is causing high latitude land areas to dry out 

and warm up faster. This creates land temperature patterns that 

can trap summer weather systems and make them stagnant. Studies have linked deadly summer heat waves and floods to this 

change in the climate. 

Finally, rapid Arctic warming may be favoring weather regimes 

that exacerbate drought, heat, and wildfires in our Western States 

while stacking the deck toward cool and stormy conditions in the 

East. Remember the parade of bomb cyclones that struck the eastern seaboard last winter? This pattern was responsible. 

In a nutshell, we know that our atmosphere is warmer and wetter, which alters every weather event that happens now. It’s relatively easy to determine that climate change made Harvey’s rainfall more intense, but it’s much harder to say whether Harvey 

would have stalled over Houston in the absence of climate change. 

There’s no doubt that the Arctic has warmed much faster than 

elsewhere, but whether Arctic air is surging southward more frequently now because of climate change is a cutting-edge research 

question. 

This is just a sampling of the many topics being studied in our 

universities and research laboratories, the results of which are crucial to understanding climate change impacts, knowledge that will 

help decisionmakers and each of us prepare for a future with even 

more destructive weather extremes. Clearly more work is needed to 

confirm or reject these complex relationships, though many are already coming into sharp focus. 

Thank you again for inviting me to be here. 

[The prepared statement of Dr. Francis follows:] 
35 

WOODS HOLE RESEARCH CENTER 

Testimony for Congressional Hearing 

House Science, Space, and Technology Committee 

10:00 am EST, 12 February 2019 

by jennifer Francis PhD, Senior Scientist at the Woods Hole Research Center, Falmouth, MA 

www.whrc.org I jenniferAFrancis.com 

My name is Jennifer Francis. I'm an atmospheric scientist at the Woods Hole Research Center in 

Massachusetts. My research focuses on the connection between climate change and extreme 

weather events. Thank you, Chairwoman Johnson and members of the committee, for the 

opportunity to testify here today. 

It's not your imagination: extreme weather events have become more frequent in recent decades. 

According to analysis by Munich Re, one of the foremost reinsurance companies in the world, 

the occurrence of extreme weather events around the globe has nearly tripled since the 1980s 

[Fig. 1]. 

MumcllRE 

Figure 1: Number of extreme events related to weather (green, blue, and orange) and non-weather (red) 

events from 1980 to 2017. Compiled by Munich Re, 2018: https:j fnatcatservice.munichre.com 

149 Woods Hole Road· Falmouth, MA 02540-1644 USA · 508-540-9900 · whrc.org 
36 

WOODS RESEARCH CENTER 

Images of floods caused by feet of rain unleashed by hurricanes Harvey and Florence, docks 

sitting on dry soil in California's reservoirs, a sunken New Jersey roller coaster in the wake of 

Superstorrn Sandy to name only a very few are forever etched in our memories. Yes, extreme 

weather has always happened, but there's no question that it's more vicious now, and all signs 

point to it getting worse as the globe continues to warm under a thickening blanket of greenhouse 

gases. 

Before I go any further, let's clear up a few definitions that sometimes cause confusion. Climate 

change versus global warming: Climate change means all the ways that the climate system is 

changing, while global warming is just one of those ways. Climate versus weather: Climate is the 

average of all the weather that occurs at a particular location, while weather is the day-to-day 

swings in temperature and precipitation. Think of climate as your personality, while weather is 

your mood on any given day. 

The links between climate change and extreme weather are a hot topic of scientific research. 

Some of the connections are straightforward and undisputed. For example, increasing global 

temperatures are making heat waves more intense and persistent, and therefore more deadly. As 

the air and oceans warm, evaporation also increases, which fuels an uptick in heavy precipitation 

events [Fig. 2]. 

Observed Change in Heavy Precipitation 

Observed Change in the Total Annual Precipitation Falling in the Heaviest 1% of Events 

1958-2016 

Figure 2: from National Climate Assessment Report 2018: https:jjnca2018.globalchange.govf 

149 Woods Hole Road· Falmouth. MA 02540-1644USA · 508-540-9900 · whrc.org 
37 

WOODS HOLE RESEARCH CENTER 

The extra moisture and warmer 

oceans are also fueling rapid 

intensification of tropical storms. 

Storm surges are doing more 

damage because sea level is higher. 

On a happier note, though, fewer 

low-temperature records are being 

broken. Evidence of these changes is 

abundant and clearly tied to a 

warming planet owing to human 

influences [Fig. 3]. 

Recent studies are uncovering a 

myriad of other less straightforward 

connections, as well. The polar 

vortex has been in the news a lot 

lately, so let's start with winter 

extremes. 

The true polar vortex is a pool of 

frigid air encircled by strong winds 

that sits about 30 miles above the 

Arctic during winter. Some evidence 

suggests it has been weakening and 

deforming more often lately1

, and 

when that happens, extreme cold 

AND hot temperatures strike areas 

in the northern hemisphere, as is 

clearly apparent in temperature 

anomalies during the severe cold 

snap two weeks ago [Fig. 4]. New 

research suggests that rapid Arctic 

warming is making these vortex 

splits more likely2

• So even though 

cold records are being broken less 

often, severe and persistent cold 

spells will still happen. 

:: '"*"·~--~ ~.4/: o.o ~l"/'~'e,· \:(.,.e,'""' .,, .. ~ ... ,.1srug 

-05 

·1 0 

!J: , "V' ~ { '; '' , ,, ,,''\ ''' ),t)l'i 

1880 1900 1920 1940 1960 1980 2000 2020 

(c) 

20 

1.5 

05 

0.0 

-05 

·1 0 

1900 1920 HMO 1960 1980 2000 2020 

All Human and Naturatlnttuences 

1880 1900 1920 1940 1960 1980 2000 2020 

Figure 3: Climate model simulations illustrating the roles of 

various factors influencing global temperature changes since 

the late 1800s. Note that natural factors alone (top) would 

have caused the Earth to be in a gradual cooling cycle. From 

National Climate Assessment Report 2018. 

Turning southward, global warming appears to be widening the tropical zone farther north and 

south. A symptom of this expansion is abnormal heat and drought in temperate regions such as 

Australia, southern California, and South Africa. 

149 \'>:ioods Hole Road· Falmouth, Mi\ 02540-1644 USA · 508-540-9900 · whrc.org 
38 

WOODS HOLE RESEARCH CENTER 

Figure 4: Global 

near-surface air 

temperature 

departures during 

the late january 

2019 extreme cold 

spell in the 

Midwest. From the 

U. of Maine's 

Climate Reanalyzer 

http:ffwww.climate 

reanalyzer.org 

Another emerging hypothesis is related to the rapid loss of the spring snowcovcr over northern 

parts of continents. This earlier melt is causing high-latitude land areas to dry out and warm up 

faster, creating land temperature patterns that can trap summer weather systems in slow steering 

currents, making them stagnant. Studies have linked deadly summer heat waves and floods to 

this change in the climate3 

Finally, a complex interplay between shifting ocean temperature patterns and a rapidly warming 

Arctic may be favoring weather regimes that exacerbate drought, heat, and wildfires in our 

western states while stacking the deck toward cool and stormy conditions in the east. Remember 

the parade of "bomb cyclones" that struck the eastern seaboard last winter? This west/cast 

pattern was responsible. 

In a nutshell, we know that climate change has made our atmosphere warmer and wetter, which 

alters every weather event that happens now. But assessing how climate change may affect the 

track and persistence of a weather system is still a challenge. It's relatively easy to determine that 

climate change made Hurricane Harvey's rainfall more intense4

, but it's much harder to say 

whether Harvey would have formed in the absence of climate change, or whether climate change 

caused it to stall over Houston. There's no doubt that the Arctic has warmed much faster than 

elsewhere, but whether Arctic air is surging southward more frequently now because of climate 

change is a cutting-edge research question. 

149 Woods Hole Road· falmouth, M.A. 02540·1644 USA · 508-540,9900 · whrc.org 
39 

WOODS HOLE RESEARCH CENTER 

This is just a sampling of the many topics being studied in our country's universities and 

research laboratories, the results of which are crucial to understanding climate change impacts 

that will help decision-makers and each of us prepare for a future with even more intense and 

destructive weather extremes. Clearly more work is needed to confirm or reject these complex 

relationships, though many are already coming into sharp focus. 

Thank you again for the opportunity to participate in this hearing. 

References 

1. https://journals.ametsoc.org/doi/1 0.1175 /BAMS-D-16-0259.1 

2. https://agupubs.onlinelibrary.wiley.com/ doi/ abs/10.1 029/20 18JD02922 2 

3. https:f/www.nature.comjarticles/srep45242 

4. https:f/agupubs.onlinelibrary.wiley.com/ doi/ 10.1029/20 18EF000825 

149 Woods Hole Road· Falmouth, Mi\ 02540-1644 t:SA · 508-540-9900 · whrc.org 
40 

Dr. Jennifer Francis is an atmospheric scientist at the Woods Hole Research Center. 

She is well known for her research on the link between climate change and extreme 

weather. Dr. Francis' research has focused especially on the connection between the 

rapidly warming Arctic and disruptions to the jet stream. 

She is regularly quoted in major media outlets and appears on television to explain 

climate change impacts. This year, her research has been featured in the New York 

Times, the Wall Street journal, USA Today, the Chicago Tribune, on NPR, and on PBS 

News Hour. Her writing has appeared in the Washington Post. 

Before WHRC, Dr. Francis was at the Rutgers University Department of Marine and 

Coastal Sciences. She received her Ph.D. in Atmospheric Sciences from the 

University of Washington and her undergraduate degree from San Jose State. 
41 

Chairwoman JOHNSON. Thank you, Dr. Francis. 

Dr. Majkut? 

TESTIMONY OF DR. JOSEPH MAJKUT, 

DIRECTOR OF CLIMATE POLICY, NISKANEN CENTER 

Dr. MAJKUT. Good morning, and thank you for having me, Chairwoman Johnson, Ranking Member Lucas, Members of the Committee. 

My name is Joseph Majkut, and I am the Director of Climate 

Policy at the Niskanen Center, which is a 501(c)(3) located here in 

Washington. We work to promote public policy to advance an open 

society and particularly in climate we promote a mainstream understanding of climate science. It’s nothing to be afraid of. And we 

aim to better characterize the risks of climate change. And on the 

policy side we support market-based policies to reduce greenhouse 

gas emissions. 

The Committee asked that we comment on the recent United Nations’ Intergovernmental Panel on Climate Change’s Special Report 

on Global Warming of 1.5 °C, as well as the Fourth National Climate Assessment prepared by the USGRCP (U.S. Global Change 

Research Program), and I’d like to offer a brief summary of those 

reports. 

Climate change is real, and global emissions of greenhouse gases 

are driving latter-day global warming. Manifestations of that 

warming are increasingly observed, as Dr. Francis just told us in 

great detail, and attributed to global emissions as well. But these 

are early days, so many of the changes scientists expect to see are 

either subtle or undetectable at high confidence. 

Yet as climate change continues, more severe and perverse effects will manifest themselves causing economic harms and damages to individuals, ecosystems, and other things that we tend to 

be concerned about. The science tells us also that limiting climate 

change means ceasing global emissions, and that’s a challenging 

thing to do. 

The goals articulated in international agreements, that is limiting warming to 1.5 or 2 °C globally are probably unlikely given 

that they would require global emissions to fall by 45—or 25 percent by 2030 and further from there. That doesn’t mean that the 

impulse to do that is unjustified given the risks we face. Those 

emissions reductions, however, sit in stark contrast to what we’ve 

seen over the last few decades. To even get close, we’ll need significant innovation in low-carbon technology, finance, and market design in order to be able to provide reliable, affordable, and globally 

accessible low-carbon energy. 

Given the present circumstance, how should this Committee respond this Congress? I’ve got three areas that I think the Committee should point its attention to. First, the time to talk about 

solving climate change has really passed us. We’re managing a 

chronic condition, and we cannot place the burden on reducing 

global emissions alone. Rather, we must prioritize reducing social— 

societal vulnerability and adapting to climate change where we 

can. While this will largely be an effort for the private sector and 

local government, those efforts will be bolstered by continued Federal support for research into climate change’s effects and the risks 
42 

that our communities face. This research can be disseminated 

through social and professional networks, and devices like the National Climate Assessment provide a very good venue for that 

work. 

Second, a world aiming for 2 °C will require a portfolio of lowcarbon energy sources, including carbon capture and storage for 

fossil fuels. In a world aiming for 1.5 °C, processes that remove carbon from the atmosphere will need to be deployed at a scale capturing up to 1/4 of today’s emissions, and that is a mind-boggling 

number for an infant technology. Both of these will be large industries, but the technologies are so infant that they need your support. Faster progress is possible through smart investments in advanced research, which deserve the Committee’s continued attention and support. 

Third, we have to research alternatives. Last Congress I testified 

before your Subcommittees on Environment and Energy on a research and governance agenda for so-called geo-engineering technologies, which could sever the link between global emissions and 

warming. While we had a productive hearing, there’s still much 

that this Committee could do to support early research into these 

technologies and help establish a set of norms under which that research could be done. 

Thank you for inviting me to testify, and I look forward to a robust discussion. 

[The prepared statement of Dr. Majkut follows:] 
43 

STATEMENT OF JOSEPH MAJKUT 

DIRECTOR OF CLIMATE POLICY 

NISKANEN CENTER 

CONCERNING THE STATE OF CLIMATE SCIENCE 

FEBRUARY 13,2018 

Good morning Chairwoman Johnson, Ranking Member Lucas, and members of the Committee. I 

am grateful for the invitation to join you today, and for the opportunity to share my perspective 

on the state of climate science, and why it matters. 

My name is Joseph Majkut. I am the director of climate policy at the Niskanen Center, located 

here in Washington, D.C. 1 The Niskanen Center is nonpartisan 501(c)(3) organization that 

promotes public policy to advance an open society. We reject ideological dogmatism and argue 

for a balanced consideration of the need for social justice, civil liberties, individual freedom, and 

community wellbeing. Our work in climate seeks to promote mainstream understanding of 

climate science, better characterize the risks of climate change, and support market-based 

policies to reduce greenhouse gas emissions. 

The atmosphere, and the climate it maintains, are a public good. No matter your beliefs about the 

proper size and scope of government, the reality is that government must act to reduce the risks 

of climate change, and it already is doing so in several areas. But at present, far too many tons of 

C02 are emitted here, and abroad, without sufficient regard to the damages they will cause 

future generations. In the long term, that will make us worse off. 

The responses to this problem do not have to be onerous government regulation and mandates, 

and they don't have to be hasty. It wouldn't be wise to halt emissions tomorrow or prevent future 

economic growth, but we could be doing much more to reduce emissions here in the United 

States beyond the already laudable reductions we've seen in the last 10 years. Congress should 

pursue new solutions to outpace and underspend the mix of regulations and subsidies that we 

have today. There is no better innovative force than the private sector, but if you really want 

energy innovation, you need to show innovators there is a market waiting for them. 

For this hearing, we were asked to advise the committee on how recent scientific advances have 

affected our understanding of the risks of climate change and what society can do to respond to 

those risks. We were asked to specifically comment on the United Nations Intergovernmental 

1 The Niskanen Center's writing and analysis on climate matters can be found here: 

https://niskanencenter.orglblog/policies/climate/ 
44 

Panel on Climate Change's Special Report Global Warming of 1.5C2 and the 4th National 

Climate Assessment prepared by the U.S. Global Change Research Program.3 

I think a fair summary of those reports might go as follows. Climate change is real and global 

emissions of greenhouse gases are a leading driver of latter-day global warming. The 

manifestations of that warming are being increasingly observed in climate indices and 

understood as a factor in weather and climate events. But these are early days, so many of the 

changes scientists expect are still subtle or even undetectable at high confidence. As climate 

change continues, more severe and pervasive effects will reveal themselves, causing damages to 

individuals, ecosystems, and economic harm. 

However, halting climate change at the levels being targeted in international agreements, either 

1.5 or 2 degrees C, would require significant reductions in global emissions rates to start 

immediately and proceed quickly. To be consistent with continued economic growth, those 

reductions will require technological innovations to provide reliable, affordable, and 

globally-accessible low-carbon energy. 

Given where we find ourselves, how should this committee respond in this Congress? 

First, the time to talk about solving climate change has passed. The warming that has already 

occurred is evident and will continue with global emissions. We are managing a chronic 

condition and we cannot place the whole burden on reducing global emissions. Reducing societal 

vulnerability and adapting to climate change should be a priority, but is also largely an activity 

done in the private sector and through local governance. Those efforts can be meaningfully 

informed through federal support for research into how climate change will affect our 

communities. The products of that work can be disseminated through social and professional 

networks, as well as through efforts like the repeating National Climate Assessment. Identifying 

new research needs and new means of understanding climate risks at all levels of government is 

valuable. 

Second, I think it is prudent for the committee to recognize that the emissions reductions 

necessary to meet any temperature target, but especially anything approaching 2 or l.SC, will 

require substantial technological innovations and a portfolio of low-carbon energy sources. In all 

likelihood, emissions pathways consistent with a 2C warming limit will involve some form of 

carbon capture and storage for fossil fuels and I.SC will necessitate carbon removal technology.4 

2 Intergovernmental Panel on Climate Change: https://www.ipcc.chfsr151 

3 United States Global Change Research Program: https:flnca2018.globalchange.gov 4 Nature: Negative Emissions Physically Needed To Keep Global Warming Below 2'C 
45 

These, in addition to novel renewable and energy storage solutions, can be aided by smart 

investments in advanced research and deserve the committee's continued attention and support. 

Third, we should be researching alternatives. In the case of stabilizing temperatures at modest 

levels or warming, the only alternative to massive reductions in global emissions and 

deployments of carbon removal would be the deployment of geoengineering technologies that 

would intentionally offset the warming effect of global emissions. I was honored to testifY last 

Congress before the Subcommittees on Enviromnent and Energy on a research and governance 

agenda for those technologies. While we had a productive hearing, there is still much that this 

committee could do to both support early research into these technologies and help establish a set 

of norms under which that research could be done. We do not know if we will use such 

technologies, just as we can't be sure that future generations will deploy carbon removal, but we 

can create knowledge for them. 

The General Picture of Climate Science 

Note: The text in this section is excerpted from a previously published paper available in fUll by 

download, 5 which offers my summary of the state of basic science on climate change and its 

drivers. 

The foundations of climate science date back to the early 19th century, when scientists-using 

their newfound sophistication in chemistry and physics-became aware that heat trapping gases 

in the atmosphere maintained global temperatures above freezing. Despite continued scientific 

study, the field was of little public interest until the 1960s, when scientists became increasingly 

concerned that greenhouse gas emissions might dangerously interfere with the planet's climate. 

Such concerns have inspired growing volumes of scientific research into the causes and potential 

effects of climate change ever since. 

The contemporary state of knowledge regarding climate science is compiled by the 

Intergovernmental Panel on Climate Change (IPCC) and other scientific societies, including the 

National Academies ofSciences.6 Just as basic chemistry and physics would predict, industrial 

activity has indeed increased the amount of greenhouse gases in the atmosphere (primarily C02), 

trapped heat, and warmed the climate. Associated changes have been measured in temperatures, 

rainfall, sea level, and other basic ecological and physical conditions around the world. 

https://www.nature.com/articles/ncomms8958 

5 Climate Science: A Guide to the Debate, Niskanen Center, March 2017: 

https://niskanencenter.org/wp-content/uploads/2017/03/NISKANEN-CLI MA TE-PRIMER-2017 -03-13.pdf 

• National Academies of Sciences and the Royal Society, Climate Change: Evidence and Causes, 2014: 

https://www.nap.edu/catalog/18730/climate-change-evidence-and-causes 
46 

According to the IPCC AR5, these effects should be expected to continue with additional 

emissions, "increasing the likelihood of severe, pervasive and irreversible impacts for people and 

ecosystems." 

The 4th National Climate Assessment 

The 4th National Climate Assessment presents a detailed evaluation of the available literature on 

how climate change has affected natural systems and human interests-across different regions, 

economic sectors, and ecological systems within the United States; how it will continue to do so 

in the future; and what communities are doing in response. The detailed report released in the fall 

of2018 was preceded by a special report on climate science released the previous year.7 

What, if any, climate change are we seeing in the United States? 

The authors of the NCA4 spend a lot of time assessing and identifying how and where weather 

and climate have changed over the United States in the last century and decades and the 

relationship. The summary report is itself quite long and detailed, but the topline messages are 

also pretty clear. 

Changes in weather and environmental conditions are evident in the United States, though 

detecting trends and associating them with global emissions is still an emerging field of study. So 

while there is pretty high confidence in the connection between global temperatures and 

emissions, that confidence diminishes as scientists consider more regional and local trends, 

particular classes of weather events, and individual weather events themselves. 

The NCA reports on climate trends in varying phenomena. Some examples from the 3rd chapter 

on the special report on science show the varying levels of phenomena, and the heterogeneity of 

regional climate trends. (Bulleted list are quotes) 

• Temperature Change: Detectable anthropogenic warming since 1901 has occurred over 

the western and northern regions of the contiguous United States according to 

observations and CMIP5 models (medium confidence), although over the southeastern 

United States there has been no detectable warming trend since 190 l. 

• Precipitation Change: For the continental United States, there is high confidence in the 

detection of extreme precipitation increases, while there is low confidence in attributing 

the extreme precipitation changes purely to anthropogenic forcing. 

7 US GCRP, National Climate Assessment 4 Volume 1: Climate Science Special Report 

https://science2017 .globalchange.gov 
47 

• Precipitation Change: For the continental United States, there is high confidence in the 

detection of extreme precipitation increases, while there is low confidence in attributing 

the extreme precipitation changes purely to anthropogenic forcing. 

• Extreme Storms: There is broad agreement in the literature that human factors 

(greenhouse gases and aerosols) have had a measurable impact on the observed oceanic 

and atmospheric variability in the North Atlantic, and there is medium corifidence that 

this has contributed to the observed increase in Atlantic hurricane activity since the 

1970s. There is no consensus on the relative magnitude of human and natural influences 

on past changes in hurricane activity. 

• Arctic Changes: It is very likely that human activities have contributed to observed arctic 

surface temperature warming, sea ice loss, glacier mass loss, and Northern Hemisphere 

snow extent decline (high confidence). 

• Sea Level Rise: Human-caused climate change has made a substantial contribution to 

global mean sea level rise since 1900 (high confidence), contributing to a rate of rise that 

is greater than during any preceding century in at least 2,800 years (medium corifidence). 

The relationship between specific instances of extreme weather and climate change is also 

complicated, but connections are emerging both in the physical world, and in scientific 

understanding in the field of extreme event attribution. The NCA lists a few examples where 

particular temperature events have been linked to climate change with medium corifidence, like a 

2011 heat wave in Texas. 

As the NCA reports, such individual assessments are in their early days and confidence in them 

increases with the detection and attribution of underlying trends (i.e. temperature trends and heat 

waves) or an understanding of physical mechanisms (i.e. warming surface waters and tropical 

cyclone strength and wetness). 

What are the drivers of climate risks for the United States? 

The predicted severity of climate risks depends strongly on the scenarios that you evaluate or 

highlight. The NCA reports that for a scenario with low future global emissions (RCP2.5), 

temperature increases over the continental US will range between 2.8 and 7.3 degrees F by the 

end of the century. But in a scenario with high future global emissions (RCP8.5), temperature 

increases range between 8.5-11.9 degrees F. In general, the negative effects of climate change 

get worse with total warming. 

In a bit of good news, the worst case scenarios used in NCA4 are looking unlikely. The RCP8.5 

scenario combines assumptions of high population growth, stagnating economic growth, and 

limited energy efficiency and technological innovation, resulting in high levels oflong-term ghg 
48 

emissions. In reality, there have been substantial advancements made in low and zero carbon 

technologies8, and GDP per unit of energy use has been rising steadily since 19909

• These 

promising trends, as well as declining levels of global poverty, indicate that the RCP8.5 scenario 

can likely be avoided. 

In a bit of bad news, the best case scenarios used in NCA4 are looking unlikely. The best case 

scenario (RCP2.6) would require global emissions cuts to proceed rapidly starting very soon. 

And as I discuss in the next section, nothing in the recent history of emissions indicates that we 

will come at all close. Even if you add up all that countries pledged to do as part of the Paris 

Climate Agreement, fully-achieved emissions reductions would still be too slow to meet 

stringent temperature targets. 

In general, it is appropriate for scientific assessment to consider a range of plausible outcomes 

and even to push the bounds of plausibility to examine how the climate system works in extreme 

scenarios. And just because something is unlikely does not mean that it is absurd to consider it. 

Rather, we should consider climate risk across a broad set of scenarios, calibrate our expectations 

the best we can, and understand that human agency will make a primary difference between the 

worse case and the best case over this whole century. 

Comments on the UN IPCC Special Report on l.SC 

The IPCC Special Report on l.SC assessed the state of the scientific literature on the relative 

impacts of global warming between 1.5 and 2 C and the future greenhouse emissions necessary 

to meet or otherwise exceed those levels of global warming. This report differs from previous 

efforts from the IPCC, which analyzed scenarios with average warming between I and 4 C at the 

end of this century. 10 

What motivates the 1.5 C goal? 

The study was commissioned after diplomats set the ambitious intention of keeping warming to 

within 1.5C as part of the Paris Climate Agreement, accelerating ambition beyond the 

previously-established goal of2C. By its nature, the l.SC goal was politically determined (same 

with 2C) and it was motivated by the desire to spare particularly vulnerable people, places, and 

things from the impacts of imminent climate change. 

8 1nternational Renewable Energy Energy Agency, Renewable Power Generation Costs in 2017 

httpsHwww irena ora/-/medja/Eiles/IRENA/Agencv/Publicatjon/2018/JanfiRENA 2017 Power Costs 2 

.Q18.J;Wf 

9 World Bank: GDP per Unit of Energy Use 

https:/ldata.worldbank.org/indicator!EG.GDP.PUSE.KO.PP.KD 

10 Intergovernmental Panel on Climate Change, Assessment Report 5: 

https:/lwww.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_SPM_EINAL.pdf 
49 

The IPCC survey shows that the impacts of climate change are projected to increase with 

warming, but that there is no particular global calamity that we know will occur at either 1.5C or 

2C, or even beyond 2C with certainty. The world does respond to warming in round numbers, so 

there isn't some level above which everything is lost or below which everything is fine. Instead, 

the risks go up with the extent of warming. Halting global warming at 3C would mean less 

damages than 4, 2C less than 3 C, and l.SC less than 2C. 

As we consider global warming between 1.5 and 2C, the IPCC reports that projections reveal 

significant and notable effects: 

o the increase in global sea level at the end of this century could increase by an 

additional4 inches (10 em) against a rise of 15 (40cm). 

o doubling of the land area that will experience a transition between native 

ecosystems (up to 13% of global land area) and a doubling of the number of 

animal and insect species that will lose a majority of their historical climatological 

range. 

While even the doubling of a particular effect is significant, it also doesn't demonstrate that there 

is some qualitative shift in climate impacts that might occur between 1.5 and 2C. But the report 

does show that particular climate effects could fairly be called devastating for some locations or 

ecosystems, even at such modest warmings. The prevalence of coral reefs provides an example. 

At 1.5C, coral reefs are projected to decline by 70-90%. But at 2C, the decline is projected to be 

greater than 99o/o-an absolute catastrophe for that particular kind of ecosystem and related 

economies. 

Is 1.5C (or 2C) even possible? 

The IPCC authors report that maintaining warming below 1.5C will require emissions reductions 

that imply a significant demand for technical innovations in low carbon energy. Unfortunately, 

the emissions reductions necessary to keep temperatures below 1.5C are quite rapid and strain 

credulity. 

The IPCC reports the now common scientific understanding that global temperatures have 

increased about I degree centigrade above pre industrial levels (likely range of 0.8 to 1.2 C). 

That gives us about the 0.5C of warming before 1.5C. Scientific analysis tells us that there is a 

relatively proportional relationship between the total historical global emissions and the level of 

global warming that follows. Temperature increase is a function of the cumulative stock of long 

lived climate pollutants, primarily C02, in the atmosphere. This stock effect means that for every 

year of emissions, the total amount of warming we expect to see goes up a little bit. It also means 

that we can roughly translate that remaining warming into remaining global emissions. 
50 

For the special report, the IPCC did just that. They found that the so-called carbon budget is 

between 420 GtC02 and 770 GtC02. For reference, current global emissions are about 42 

GtC02 per year and US emissions are just over 5 GtC02 per year. 11 That means that global 

warming in excess of 1.5C would be likely within 10 to 20 years at today's global emissions 

levels. After that, there is enough C02 in the air to warming beyond the stretch goal of Paris. 

To avoid such a warming, global emissions would need to fall precipitously in the coming 

decades. The IPCC reports 45 percent from 2010 levels by 2030 and by nearly 100 percent by 

2050 (since emissions have gone up since 2010, even larger cuts to today's emissions are 

necessary). The more moderate goal of limiting warming to 2C would similarly require 

emissions rates to fall 25 percent by 2030 and for emissions to be functionally eliminated by 

around 2070. 

Such a dramatic turnaround is inconsistent with the past few decades, which saw steady 

increases in C02 emissions from fossil fuel burning (rising from- 25 - 37 GtC02) and relatively 

stable emissions from deforestation (between 4 - 6 GtC02)Y The rise in fossil emissions is 

largely attributable to increases in economic growth and energy demand, with a relatively flat 

C02 intensity of energy supply globally. That increase was moderated, however, by increasing 

energy efficiency of the economy. 

To continue global economic growth, the energy efficiency of the economy should continue to 

increase and the C02 intensity of the energy supply must decrease. That means that we need to 

reduce the price of energy from clean sources relative to emitting sources, so that the transition 

to a clean economy is a benefit for society. 

While the cost of generating energy from renewable resources like wind and solar has fallen in 

recent years, and the forward outlook is sunnier still, the reality is that the IPCC report should 

serve as wakeup call for anyone dedicating their efforts to halting warming at l.SC, 2C, or more. 

The rate and depth of emissions cuts implied by these targets indicate that we should endeavor to 

keep all options on the table when addressing climate change. In a recent survey of the available 

literature of decarbonizing just the U.S. power sector, authors Themstrom and Jenkins surveyed 

30 papers and found a sturdy consensus that "a diversified mix of low-C02 generation resources 

offers the best chance of affordably achieving deep decarbonization. 13" ln particular, the ability 

11 US Environmental Protection Agency, 2018 Emissions Inventory: 

https:/lwww .epa. gov/sites/production/files/2018-04/documents/9509 _fastfacts _2018041 Ov2_ 508.pdf 12 Global Carbon Project, 2018 Global Carbon Budget: 

http://www.globalcarbonproject.org/carbonbudget/18/files/GCP _ CarbonBudget_2018.pdf 13 Jenkins and Thernstrom, DEEP DECARBONIZATION OF THE ELECTRIC POWER SECTOR 

INSIGHTS FROM RECENT LITERATURE, 2017: 
51 

to generate and dispatch electricity from non-renewable sources such as energy storage, nuclear 

reactors, or fossil-fuels with carbon capture and storage appears to be of great value. 

After emissions reach zero, the scenarios examined by the IPCC that limit warming to l.5C 

require substantial negative emissions, or carbon dioxide removal. That is the removal of C02 

from the atmosphere through technological processes (like burning cultivated biomass for energy 

and capturing the resulting C02 before it escapes to the atmosphere) or growing trees in forests. 

Carbon dioxide removal is invoked in all scenarios that appear consistent with limiting warming 

to l.5C in this century in the IPCC report. The amount of carbon dioxide removal invoked across 

the different scenarios analyzed by the IPCC is primarily driven by how much is emitted in the 

next few decades, with slower emissions reductions implying higher burdens for carbon removal. 

The amount of carbon dioxide that would need to be removed from the atmosphere is 

gargantuan, between 100-1000 GtC02, over the course of the century. 

Supporting early development of the technologies and processes that will be necessary to remove 

C02 at those levels would be a helpful contribution from this committee. The prospective scope 

of such an operation is enormous and is a real opportunity for industrial innovation. Given the 

advantages of fossil fuels, it is reasonable to think that they will continue to be a major energy 

source, creating a market for carbon capture as part of the emissions reductions portfolio. And 

the industry opportunity is large. A study published last week estimated that a meaningful 

deployment of carbon capture would be approximate 2-4 times the modern day oil industry, by 

volume ofproductY If you add in the potential for a carbon removal industry, then the scale of 

the opportunity grows. 

Climate action is not inconsistent with the continued use of fossil fuels in coming decades. In 

fact, successfully meeting these proposed targets will probably require their continued use in 

conjunction with carbon capture. 

Conclusion and Recommendations 

Thank you for your time today. Climate change is an important topic for public policymakers to 

which scientific information can make significant inputs. We all know that scientific 

considerations are not the only factor at play, but it is and remains one of our greatest 

achievements. In this case, science can help us understand the scope of the problem and the 

effectiveness of proposed responses. The U.S. research enterprise overseen by this committee is 

https:/lwww.innovationreform.orglwp-contentluploads/2018/02/EIRP-Deep-Decarb-Lit-Review-Jenkins-Th 

ernstrom-March-2017 .pdf 14 https:l/www.nature.com/articles/nclimate3231 
52 

a valuable resource in either regard. I thank the Committee for its attention to this issue and look 

forward to an ongoing conversation. 
53 

JOSEPH MAJKUT 

Director of Climate Policy 

Joseph Majkut is director of climate policy at 

the Niskanen Center. He is an in climate 

science, climate policy, and risk and uncertainty 

analysis for decision making. He is >ro.m'""'"" 

cited by prominent media outlets; his writing 

has been featured in scientific journals, public 

media, and environmental trade press; and he 

has been invited to testifY before Congress on 

climate and scientific research. Before joining 

the Niskanen Center, he worked on climate 

change policy in Congress as a congressional 

science fellow, supported by the American 

Association for the Advancement of Science. He holds a PhD from Princeton 

in Atmospheric and Oceanic Sciences, a master's degree in Applied 

Mathematics from the Delft University of Technology, and a bachelor's degree in 

Mathematics from Harvey Mudd College. 
54 

Chairwoman JOHNSON. Thank you very much, Dr. Majkut. 

Dr. Ebi? 

TESTIMONY OF DR. KRISTIE L. EBI, 

ROHM AND HAAS ENDOWED PROFESSOR 

IN PUBLIC HEALTH SCIENCES, AND 

DIRECTOR, CENTER FOR HEALTH AND 

THE GLOBAL ENVIRONMENT (CHanGE), 

UNIVERSITY OF WASHINGTON 

Dr. EBI. Thank you, Chairman Johnson, Ranking Member Lucas, 

distinguished Members of the Committee, for the opportunity to 

speak with you today. As you know, my name is Kristie Ebi. I’ve 

got more than 20 years’ experience—— 

[Audio malfunction in hearing room.] 

Dr. EBI. Do you want me to start over? Sorry about that. The evidence is clear. Climate change is adversely affecting the health of 

Americans. Climate change is heating the land and oceans, melting 

snow and ice, increasing the frequency and severity of extreme 

weather events, and raising sea levels. All of these have significant 

implications for our health and well-being, as well as for our public 

health and healthcare infrastructure. It is timely and appropriate 

for Congress to understand this issue of critical national importance so that effective actions can be taken to protect and promote 

the health of all Americans now and in the future. 

Climate change affects human health by altering exposures to 

heat waves, floods, droughts, and other extreme events by increasing the prevalence of some vector, food, and water-borne infectious 

diseases; by reducing the quality and safety of our air, food, and 

water; and by worsening our mental health and well-being. Climate 

change also can affect health by, for example, undermining economic productivity and reducing labor productivity. 

As the Fourth U.S. National Climate Assessment highlights, 

Americans are already suffering and dying from our changing climate with primarily negative risks projected to increase with each 

additional unit of warming. The IPCC’s Special Report on Global 

Warming of 1.5 °C, which assessed research in the U.S. and globally, concluded that lower risks are projected at 1.5, than at 2 °C 

for heat-related morbidity and mortality, for ozone mortality if the 

precursor emissions remain high. Risks from vector-borne diseases 

such as malaria, dengue fever, and Lyme disease are projected to 

increase with warming from 1.5 to 2 °C, including potential shifts 

in their geographic range to areas previously unexposed to these 

diseases. 

Individuals and communities are differentially exposed to climate-related hazards and disproportionately affected by climate-related health risks. Populations experiencing greater risk include 

children, older adults, low-income communities, and some communities of color. 

The adverse health impacts of climate change have many potential economic and social costs, including medical expenses and 

caregiving services, as well as costs that are harder to quantify 

such as those associated with pain, suffering, inconvenience, or reduced enjoyment of leisure activities. Further, our healthcare infra-
55 

structure is vulnerable to extreme events with, for example, many 

hospitals and healthcare clinics located in coastal regions subject to 

flooding. 

The magnitude and pattern of future health risks depend on the 

rapidity and extent of greenhouse gas emission reductions and on 

the level of ambition and investment in adaptation. Many projected 

risks and costs which, in some cases, may be extremely 

unaffordable, can be reduced by taking immediate action to increase preparedness for effectively managing health and healthcare 

infrastructure risks. Examples include developing early notification 

and response plans such as for extreme heat, implementing integrated surveillance of climate-sensitive infectious diseases, and incorporating climate projections into emergency preparedness and 

disaster risk-management initiatives. These steps can protect 

health now and provide a basis for more effective adaptation to our 

future climate. 

Nearly all mitigation policies to reduce greenhouse gas emissions 

have benefits for health for Americans in the near- and in the longterm by reducing premature mortality and by avoiding hospitalizations. By the end of this century, thousands of premature deaths 

could be avoided and hundreds of millions of dollars in health-related economic benefits gained each year under a pathway of lower 

greenhouse gas emissions. 

Finally, on a personal note, I grew up in Senator Dingell’s district. He was a very dedicated public servant who helped write 

most of our major environmental and energy laws that were passed 

by Congress. My condolences to his family, his friends, and his colleagues. Thank you. 

[The prepared statement of Dr. Ebi follows:] 
56 

Written Testimony of 

Kristie L. Ebi 

Rohm and Hass Endowed Professor in Public Health Science 

School of Public Health 

University of Washington 

Full Committee Hearing 

on: 

The State of Climate Science 

before the 

United States House Committee on Science, Space, and Technology 

February 13,2019 

Good morning, Chairwoman Johnson and Ranking Member Lucas. Thank you for the 

opportunity to speak with the full committee today about the current understanding of the health 

risks of climate change. My name is Kristie L. Ebi; I am the Director of the Center for Health 

and the Global Environment (CHanGE) and the Rohrn and Hass Endowed Professor in Public 

Health Sciences at the University ofWashington School of Public Health. Climate change is 

affecting the health of Americans today and will affect our health and our public health and 

healthcare infrastructure in the future. This is an issue of critical national importance. Therefore, 

it is timely and appropriate for Congress to understand these challenges so that effective actions 

can be taken to protect and promote the health of Americans now and in the future. 

In summary, the evidence is clear: climate change is adversely affecting the health of Americans, 

with the impacts projected to increase with each additional unit of warming, depending on the 

rapidity and extent of greenhouse gas emission reductions. Climate change has warmed the 

world by roughly l.8°F since preindustrial times, with the rate of warming increasing 

significantly since the 1970s 1• This warming is heating the land and oceans, melting snow and 

ice, increasing the frequency and severity of extreme weather events, and raising sea levels. All 

of these have potential implications for our health and well-being. 

There are immediate actions that could increase preparedness for effectively managing these 

risks, including the risks to our healthcare infrastructure. Further, nearly all mitigation policies to 

reduce greenhouse gas emissions have benefits for health. The costs associated with those 

benefits, as measured by reductions in premature mortality and avoided hospitalizations, are 

about the same as the cost of the policies. 

The following sections (I) summarize the health risks of a changing climate in the United States, 

including the risks for our health care infrastructure, and describe populations at particular risk; 

(2) show how adaptation can protect and promote population health today and in the future; and 

1

https•//sdeoce2Q 17 e!oba!chao"' f.QV/ 
57 

(3) discuss the significant health co-benefits of mitigation policies and technologies. My 

testimony draws primarily from the 4th U.S. National Climate Assessment (NCA4)2 and the 

Lancet Countdown Brief for the United States3• Other recent publications and assessments of the 

health risks of climate change include the Lancet Countdown4; the Intergoverrunental Panel on 

Climate Change Special Report on Warming of l.5°C5

; and a publication in the New England 

Journal of Medicine on the imperative for climate action to protect health6• 

Health risks of a changing climate in the United States 

There is an increasing body of evidence highlighting the damaging effects of climate change on 

human health and health care infrastructure. This research was assessed in the NCA4 in the 

chapter on human health and in the sectoral chapters, and the Lancet Countdown Brief for the 

United States. These reports, and the underlying science on which they are based, concluded that 

climate change harms health and health care infrastructure. A key message from the NCA4 was: 

The health and well-being of Americans are already affected by climate change, with the 

adverse health consequences projected to worsen with additional climate change. 

Climate change affects human health by altering exposures to heat waves, floods, 

droughts, and other extreme events; vector-,food- and waterborne infectious diseases; 

changes in the quality and safety of air, food, and water; and stresses to mental health 

and well-being. 

A wide range of health outcomes can be affected by weather, climate variability, and climate 

change (Figure 1). Scientists have explored the many different pathways linking our changing 

climate with human health. For example, recent warming has lengthened the pollen season in the 

Midwest anywhere from 2-4 weeks, exacerbating allergic rhinitis and allergic asthma7• 

Additional warming is likely to further lengthen the season, substantially reducing the quality of 

life for those with these conditions. 

The adverse health effects attributed to climate change have many potential economic and social 

costs, including medical expenses, caregiving services, lost productivity, as well as costs that are 

harder to quantify, such as those associated with pain, suffering, inconvenience, or reduced 

enjoyment of leisure activities2• These health burdens are typically borne by the affected 

individual and by family, friends, employers, communities, and insurance or assistance 

programs. 

A recent research project I conducted with colleagues summarized the 109 published projections 

of the health risks associated with temperature extremes and occupational heat stress, air quality, 

2 https:lfnca20 18.globalchange.gov/chapter/14/ 3 http:llwww.lancetcountdown.org/media/ 1426/20 18-lancet-countdown-policy-brief-usa.pdf 4 http:llwww.lancetcountdown.org/the-report/ 

5 https:llwww.ipcc.ch/sr 15/ 

' Haines A, Ebi K. The imperative for climate action to protect health. New England Journal of Medicine 

20 19;380:263-273. 7

Ziska L, Knowlton K, Rogers C, et al. Recent warming by latitude associated with increased length of ragweed 

pollen season in central North America. Proceedings of the National Academy of Sciences 20 I I; I 08( I 0): 4248. 

2 
58 

undernutrition, and vector-borne diseases to estimate how these risks would differ at increases in 

warming of 1.5°C, 2°C, and higher8. Risks were higher at 2°C for adverse health consequences 

associated with exposures to high ambient temperatures, ground-level ozone, and undernutrition, 

with regional variations. Risks for vector-borne diseases could increase or decrease with higher 

global mean temperatures, depending on regional climate responses and disease ecology. The 

Intergovernmental Panel on Climate Change Special Report on Warming of 1.5°C concluded 

that5: 

Any increase in global warming is projected to affect human health, with primarily 

negative consequences (high confidence). Lower risks are projected at 1.5°C than at 2°C 

for heat-related morbidity and mortality (ver;v high confidence) and for ozone-related 

mortality if emissions needed for ozone formation remain high (high confidence). Urban 

heat islands often amplify the impacts ofheatwaves in cities (high confidence). Risks 

from some vector-borne diseases, such as malaria and dengue fever, are projected to 

increase with warming from 1.5°C to 2°C, including potential shifts in their geographic 

range (high confidence). 

Figure 1: Summary of the health risks of climate change in the United States 

' Ebi KL, Hasegawa T, Hayes K, Monaghan A, Paz S, Berry P. Health risks of warming of ! S C, 2" C. and higher, 

above pre-industrial temperatures. Environmental Research Letters 2018;13:063007, 

3 
59 

Another key message from the NCA4 was that although everyone is exposed to a changing 

climate, exposure and resilience capacity vary across the population (Figure 2): 

People and communities are differentially exposed to hazards and disproportionately 

qtfected by climate-related health risks. Populations experiencing greater health risks 

include children. older adults. low-income communities, and some communities of color. 

Figure 2 shows examples of populations at higher risk of exposure to adverse climate-related 

health threats along with adaptation measures that can help address disproportionate impacts. 

When considering the full range of threats from climate change as welt as other environmental 

exposures, these groups are among the most exposed, most sensitive, and have the least 

individual and community resources to prepare for and respond to health threats. White text 

indicates the risks faced by those communities, while dark text indicates actions that can be taken 

to reduce those risks. 

Figure 2: Exposure and resilience vary across populations and communities 2 

Low-income communities and some communities of color are often already overburdened with 

poor environmental conditions and are disproportionately affected by, and less resilient to, 

climate-sensitive health outcomes2. Climate change is expected to compound existing health 

issues in Native American and Alaska Native communities, partly due to the loss of traditional 

foods and practices, the mental stress from permanent community displacement, increased 

injuries from lack of permafrost, storm damage and flooding, smoke inhalation, damage to water 

and sanitation systems, decreased food security, and new infectious diseases 

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60 

Vulnerability is typically higher in communities with less access to information, resources, 

institutions, and other factors to prepare for and avoid the health risks of climate change. Some 

of these communities include poor people in high-income regions, minority groups, women, 

pregnant women, those experiencing discrimination, children under five, persons with physical 

and mental illness, persons with physical and cognitive disabilities, the homeless, those living 

alone, Indigenous people, people displaced because of weather and climate, the socially isolated, 

poorly planned communities, the disenfranchised, those with less access to healthcare, the 

uninsured and underinsured, those living in inadequate housing, and those with limited financial 

resources to rebound from disasters2• 

Summary of selected health risks 

This section summarizes some of the most well-understood health risks associated with climate 

change and their effects across the United States. 

Extreme heat: Summers are starting earlier, lasting longer, and are on average hotter, with 

temperature records being broken regularly. The average summer temperature in 2016 was 2.2°F 

greater than the 1986-2005 average, resulting in 12.3 million more Americans exposed to 

extreme heat that year3. Thus, it should not be surprising that extreme heat is the leading cause of 

weather-related deaths in the U.S. 

Exposure to extreme heat can lead to heat exhaustion, life threatening heat stroke, and exacerbate 

chronic lung, heart, and kidney diseases. Further, emerging evidence suggests that hotter 

temperatures can cause pregnancy complications, worsen mental health conditions, and increase 

suicides, amongst other risks3• One estimate projected that by the year 2050, approximately 

3,400 more Americans could die annually from heat-related causes9• 

Individuals more sensitive to exposure to extreme heat include children, pregnant women, 

outdoor workers, older adults, those who are chronically ill, and low-income families. Health 

risks may be higher earlier in the summer season when people are less accustomed to 

experiencing higher temperatures. Here are some of the facts: 

• At least 729 children died from heatstroke across the country after being left in hot cars 

between 1990 and 201410• 

• Studies in the United States have linked extreme heat exposure to preterm births and low 

birth weights 11 • 

9 U.S. Environmental Protection Agency. Multi-Model Framework for Quantitative Sectoral Impacts Analysis: A 

Technical Report for the Fourth National Climate Assessment [Internet]. Washington DC; 2017. Available from: 

https:lfcfpub.epa.gov/si/si_public_record_Report.cfm!Lab=OAP&dirEntryld=335095 

10 Zonfrillo MR. Ramsay ML, Fennell JE, Andreasen A. Unintentional non-traffic injury and fatal events: Threats to 

children in and around vehicles. Traffic injury prevention 20 18; 19(2), 184-188. 11 Kuehn L., McCormick,$. Heat exposure and maternal health in the face of climate change. International journal 

of environmental research and public health Kuehn, L., & McCormick, S. (20 17). Heat exposure and maternal 

health in the face of climate change. International journal of environmental research and public health, 14(8), 

853.20 17; 14(8), 853. 

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61 

• Outdoor workers in the agriculture and construction industries are disproportionately 

vulnerable to heat-related illness. In Maricopa County, Arizona, 115 men in these 

industries died due to heat-related causes between 2002-2009, comprising 35% of all 

male deaths from heat-related causes 12 • 

However, heat-related deaths can be prevented. Strategies to accomplish this include heatwave 

early warning and response systems, which provide advanced and timely information to 

individuals about the risks of thermal extremes through television, radio, text messaging, and 

other forms of communication, empowering individuals and communities to make smart choices 

to protect themselves. Other options include individual acclimatization (the process of adjusting 

to higher temperatures) and protective measures, such as air conditioning at home, cooling 

shelters, green space in the neighborhood, and resilient power grids to avoid power outages 

during extreme weather events2• 

Communities across the United States should learn from past heat-related tragedies to protect 

populations from future extreme heat events. The City of Philadelphia, PA provides an example. 

In July 1993, a devastating heat wave hit the Mid-Atlantic region, resulting in 118 excess deaths 

in Philadelphia13 . Since that tragic event, the City of Philadelphia took proactive measures to 

prevent a repeat occurrence, despite rising summer temperatures. The City developed a system 

triggered when the National Weather Service issues an Excessive Heat Warning. The 

Philadelphia Department of Public Health (PDPH) Excessive Heat Public Safety Plan uses a 

variety of communication tools, including press releases, social media, and the PDPH website to 

inform the public about heat-related dangers. An emergency phone line staffed with public health 

nurses is also opened, as are cooling centers to allow individuals without access to cooling to 

seek relief. This comprehensive heat early warning system provides frequent and consistent 

messaging to the public, warning of the dangers of extreme temperatures and providing 

information on how to stay cool. Since 1993, heat-related deaths in Philadelphia have fallen 

dramatically, with annual deaths now in the low single digits. 

Analyses of hospital admissions, emergency room visits, and emergency medical services calls 

show that hot days also are associated with an increase in heat-related illnesses, including 

cardiovascular and respiratory complications, renal failure, electrolyte imbalance, kidney stones, 

negative impacts on fetal health, and preterm birth2• Risks vary across regions. The health care 

costs from just one heatwave in California were estimated at $179 million14.These costs could be 

reduced substantially with investments in heatwave early warning systems and other preventive 

measures, saving money and lives. 

12 Petitti DB, Harlan SL, Choweii-Puente G, Ruddell D. Occupation and Environmental Heat-Associated Deaths in 

Maricopa County, Arizona: A Case-Control Study. PLoS ONE 2013;8(5): e62596. 

https://doi.org/1 0.1371/journal.pone.0062596 

'

3 Kalkstein LS, Sheridan SC, Kalkstein Aj. Heat/Health Warning Systems: Development, Implementation, and 

Intervention Activities. In: Ebi K.L., Burton 1., McGregor G.R. (eds) Biometeorology for Adaptation to Climate 

Variability and Change. Biometeorology, vel I. 2009. Springer, Dordrecht 14 Knowlton K, Rotkin-EIIman M, Geballe L, Max W, Solomon GM. Six Climate Change-Related Events In The 

United States Accounted For About $14 Billion In Lost Lives And Health Costs. Health Affairs 2011 Nov 2 [cited 

2018 Nov 7];30( II ):2167-76. Available from: http://www.healthaffairs.org/doi/1 0.1377/hlthaff.20 11.0229 

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62 

Heatwave early warning systems established in large cities across America informed the 

development of the National Integrated Heat Health Information System (NIHHIS) that provides 

an online portal of information and resources to help communities understand prepare for the 

health impacts of extreme heat 15 • NIHHIS is an interagency partnership developed by the Centers 

for Disease Control and Prevention, the National Oceanic and Atmospheric Administration, and 

domestic and international partners, with the goals of building understanding of the problem of 

extreme heat; defining demand for climate services that enhance societal resilience; developing 

science-based products and services from a sustained climate science research program; and 

improving capacity, communication, and societal understanding of the problem in order to 

reduce morbidity and mortality due to extreme heat. Communities, particularly in smaller cities 

and rural areas, generally need human and financial resources to design and implement heatwave 

early warning systems that take into account local vulnerabilities and capacities. 

Extreme Weather and Climate Events: Extreme weather and climate events, such as floods, 

droughts, and wildfires, are increasing with climate change, threatening health and healthcare 

facilities. Hurricanes also cause significant damage. The health, well-being, and security of 

populations are significantly and increasingly affected by extreme weather and climate events. 

Death, physical injury, and increased risk of disease and mental health impacts can result from 

climate-related disasters. The indirect consequences can include substantial and long-lasting 

impacts on health systems, population health, and livelihoods. These events can destroy health 

care infrastructure, damage medical equipment and supplies, result in fewer health personnel to 

provide care, and disrupt health-related services (e.g. water and sanitation facilities), leading to a 

reduced capacity to meet public health needs2

•

3• Loss of livelihoods (e.g. lower crop yields) and 

population displacement can also adversely affect, for example, nutritional status and mental 

illness. 

One example is the health impacts of drought and periods of unusually dry weather. In late 2015, 

California was in the fourth year of its most severe drought since becoming a state, with 63 

emergency proclamations declared in cities, counties, tribal governments, and special districts2• 

Households in Tulare and Mariposa counties reported a range of drought-related health impacts, 

including increased dust leading to allergies, asthma, and other respiratory issues and acute stress 

and diminished peace of mind. These health impacts were not evenly distributed, with more 

negative physical and mental health impacts reported when drought negatively affected 

household property and finances. 

Extreme weather and climate events are having an increasingly devastating impact on Americans 

in terms of lives lost, lives affected, and economic cost. In 2017 alone there were 16 billiondollar disasters in the U.S. that together cost about $306 billion dollars16. The official death toll 

was estimated at 3,278, although the actual total was likely much higher. During the same year, 

23 events (floods, storms, wildfires) affected approximately 866,835 individuals, and the homes 

of 109,108 individuals were destroyed3• The U.S. had 14 billion-dollar disasters in 2018, killing 

at least 247 people, and costing the nation an estimated $91 million (Figure 3). Most ofthat 

15 https:l/toolkit.climate.govltoollnational-integrated-heat-health-information-system-nihhis 16 https:l/www.ncdc.noaa.gov/billions/ 

7 
63 

damage, about $73 billion, was attributable to three events: Hurricanes Michael and Florence and 

the collection of wildfires that raged across the West. Since 1980, overall damages from 219 

weather and climate billion-dollar disasters in the U.S. exceeded $1.6 trillion., with over l 0,000 

deaths. 

Figure 3: U.S. 2018 billion-dollar weather and climate disasters 

U.S. 2018 Billion-Dollar Weather and Climate Disasters 

The 2018 wildfire season in California was the deadliest and most destructive on record, with 

8,527 fires burning an area of nearly 1.9 million acres, the largest amount burned in a fire season, 

and about 1 00 fatalities. In addition, large populations were exposed to gases and fine 

particulates that can harm the heart and lungs; at times, the air quality in parts of California were 

unhealth for all to breathe. Wildfires are expected to become more common as the climate 

continues to change, which means more Americans could be exposed and adversely affected. 

The impacts of an extreme weather or climate event are often not confined to the directly 

affected area. For example, wildfire smoke can affect air quality over multiple states. Individuals 

displaced by hurricanes or floods may move to other regions to seek shelter and access health 

care. 

Children, older adults, low-income communities, some communities of color, and those 

experiencing discrimination are disproportionately affected by extreme weather and climate 

events, partially because they are often excluded in planning processes. Other populations that 

could experience increased sensitivity to extreme weather and climate events include outdoor 

workers and communities disproportionately burdened by poor environmental quality. 

ln addition to the direct hanns on human health, extreme weather and climate events have the 

potential to adversely affect the operation of hospitals and other critical healthcare physical 

8 
64 

infrastructure. During Hurricane Harvey, hospitals in Houston, Texas were challenged to provide 

essential medical services to their patients. According to Darrel Pile, chief executive of the 

Southeast Texas Regional Advisory Council, Harvey "challenged every plan we've written, 

every resource, every piece of inventory .. .it was just unimaginable 17 ." Despite the challenges 

faced during and after Harvey, the impacts on healthcare could have been far worse, had health 

systems not had plans in place to deal with an event of this magnitude. Such plans included 

sealing flood-prone areas and making provisions for extra personnel and supplies. As climate 

change increases the risks of extreme weather and climate events that can disrupt healthcare 

operations, additional planning will be needed to ensure continuity of care even during 

meteorological conditions thought unimaginable a decade ago. 

Air quality: Poor air quality causes a host of health complications, including premature 

mortality, exacerbations of chronic obstructive pulmonary disease, asthma, and allergies. Climate 

change is decreasing air quality by increasing concentrations of ground-level ozone that harms 

the lungs and can cause early death. Long-term exposure to ozone is linked to aggravation of 

asthma and is likely one cause of asthma development. Long-term exposures to higher 

concentrations of ozone may also be linked to permanent lung damage, such as abnormal lung 

development in children. 

Earlier springs, warmer temperatures, precipitation changes, and higher carbon dioxide 

concentrations can increase exposure to pollen allergens that can be especially problematic to 

those with hay fever and asthma. Warmer spring temperatures cause some plants to start 

producing pollen earlier, while warmer fall temperatures extend the growing season for other 

plants, such as ragweed18• Figure 4 shows changes in the ragweed pollen season from 1995-

2015. While air quality across the U.S. improved since 1988, it has been deteriorating in western 

states because of wildfires. 

People most at risk from poorer air quality include people with asthma, children, older adults, 

and people who are active outdoors, especially outdoor workers. In addition, people with certain 

genetic characteristics, and people with reduced intake of certain nutrients, such as vitamins C 

and E, are at greater risk from ozone exposure19. 

17 https://www.washingtonpost.com/national/health-science/some-hospitals-evacuated-but-houstons-vaunted· 

medical-world-mostly-withstands-harvey/20 17/08/30/2e9e5a2c-8d90-ll e7 -84c0-

02cc069f2c37 _story.html?utm_term=.2c45181 Oa9db 18 https://www.epa.gov/climate-indicators/climate-change-indicators-ragweed-pollen-season 19 https://www.epa.gov/arc-x/climate-adaptation-ground-level-ozone-and-health 

9 
65 

Figure 4: Changes in the ragweed pollen season, 1995-2(}15 

This figure shows how the length of ragweed pollen season changed at 11 locations in the 

central United States and Canada between 1995 and 2015. Red circles represent a longer pollen 

season; the blue circle represents a shorter season. Larger circles indicate larger changes. 

Source: EPA 

Infectious diseases: Multiple infectious diseases are transmitted by mosquitoes, ticks, and fleas 

(e.g. vectors), including Lyme disease, dengue fever, and West Nile virus. The number of cases 

of climate-sensitive infectious diseases tripled between 2004-2016, with over 96,000 

documented cases in 20 163• Areas not accustomed to particular infectious diseases are reporting 

cases for the first time. For instance, in my home of Western Washington, public health officials 

identified the first locally-transmitted case of West Nile Virus, a likely harbinger of trends to 

come as summers continue to warm in the Pacific Northwest. 

Climate change is expected to alter the geographic range, seasonal distribution, and abundance of 

disease vectors, exposing more people in North America to ticks that carry Lyme disease or other 

bacterial and viral agents, and to mosquitoes that transmit West Nile and other viral diseases2

• In 

the absence of adaptation, exposure to the mosquito Aedes aegypti that can transmit dengue, 

Zika, chikungunya, and yellow fever viruses, is projected to increase by the end of the century 

due to climatic, demographic, and socioeconomic changes, with some of the largest increases 

projected to occur in North America. Similarly, changes in temperature may influence the 

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66 

distribution and abundance of tick species that transmit common pathogens. At the same time, 

very high temperatures may reduce transmission risk for some diseases. 

Changing weather patterns interact with other factors, including how pathogens adapt and 

change, changing ecosystems and land use, demographics, human behavior, and the status of 

public health infrastructure and management. Economic development may substantially reduce 

transmission risk by reducing contacts with vector populations. 

Outbreaks occurring in other countries can impact U.S. populations and military personnel living 

abroad and can sometimes affect the United States2• For example, the 2015-16 El Niiio, one of 

the strongest on record, may have contributed to the 2014-16 Zika epidemic in the Americas. 

Warmer conditions may have facilitated expansion of the geographic range of mosquito 

populations and increased their capacity to transmit Zika virus. Zika virus can cause a wide range 

of symptoms, including fever, rash, and headaches, as well as birth defects. The outbreak began 

in South America and spread to areas with mosquitoes capable of transmitting the virus, 

including Puerto Rico, the U.S. Virgin Islands, Florida, and Texas. 

Effective public health strategies can reduce the dangers associated with the expansion of the 

geographic range of climate-sensitive infectious diseases. As diseases move into new areas, 

public health messaging on appropriate prevention strategies must be adopted in order to prevent 

uncontrolled outbreaks. Similarly, continuing education for healthcare professionals should 

emphasize the potential health hazards associated with climate change. Many medical staff may 

be faced with conditions never encountered heretofore in their careers and must be prepared to 

treat them appropriately. 

Additionally, it is possible to forecast where and when the associated diseases could occur based 

on understanding the environmental determinants of these vectors and the pathogens they can 

carry20• This vital information can provide up to months lead time for public health practitioners 

to prepare for and effectively respond to outbreaks. 

Water-related illnesses and deaths: The growth rate of several important human pathogens that 

can contaminate water depend on the temperature of the water. Because there are thresholds for 

of how many organisms are required for disease to occur, increasing water temperatures 

associated with climate change are projected to alter the seasonality of growth and the 

geographic range of harmful algae and coastal pathogens3. Further, runoff from more frequent 

and intense rainfall is projected to increasingly compromise recreational waters and sources of 

drinking water through increased introductions of pathogens and toxic algal blooms. Projected 

increases in extreme precipitation and flooding, combined with inadequate water and sewer 

infrastructure, can contribute to viral and bacterial contamination from combined sewage 

overflows and a lack of access to potable drinking water, increasing exposure to pathogens that 

can cause gastrointestinal illnesses. 

20 Morin CW, Semenza JC, Trtanj JM, Glass GE, Boyer C, Ebi KL. Unexplored Opportunities: Use of Climate-and 

Weather-Driven Early Warning Systems to Reduce the Burden of Infectious Diseases. Current Environmental Health 

Reports 2018: p. 1-9; https://doi.org/10.1007/s40572-018-0221-0 

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67 

There is robust scientific understanding of the relationship between warmer water temperatures 

associated with longer summers and the growth of bacteria called Vibrios that can cause 

diarrheal illnesses, food poisoning, and skin infections. In the Northeast U.S., there was a 27% 

increase in the coastline area suitable for Vibrios in the 20 I Os vs the 1980s3• This means more 

Americans could be at risk through contact with the water or by eating contaminated shellfish. 

Increases in air temperatures and heatwaves are expected to increase temperature-sensitive 

marine pathogens such as Vibrios. Improving research and communication around the risks 

posed by Vibrios is essential to protecting human health as well as the viability of the shellfish 

industry that forms a critical component of many coastal and Native American communities. 

The relationships between precipitation and temperature-driven transmission of waterborne 

diseases are complex and site-specific, with, for example, some areas finding increased numbers 

of cases associated with excessive rainfall and others finding stronger associations with drought. 

Heavy rainfall, flooding, and high temperatures are associated with increases in diarrheal disease 

and can increase other bacterial and parasitic infections such as leptospirosis and 

cryptosporidiosis. 

Food security and nutrition: Climate change, including changes in some extreme weather and 

climate events, can adversely affect U.S. and global food security by, for example, altering 

exposures to certain pathogens and toxins (for example, Salmonella and Campylobacter), 

disrupting food availability, decreasing access to food, and increasing food prices2. Food quality 

also is expected to be affected by rising carbon dioxide concentrations that decrease dietary iron, 

zinc, protein, and other macro- and micronutrients in key staple crops such as wheat and rice. 

However, any impact on human health will depend on the many other drivers of global food 

security and factors such as food chain management, human behavior, and food safety 

governance. 

Projected changes in carbon dioxide concentrations and climate change could diminish expected 

gains in global nutrition2• 

Mental health: Exposure to short-lived or prolonged weather- or climate-related events can 

result in mental health consequences, from stress and distress symptoms to clinical disorders, 

such as anxiety, depression, post-traumatic stress, and suicidaJity2. These mental health impacts 

can interact with other health, social, and environmental stressors to diminish an individual's 

well-being. Individuals whose households experienced a flood or risk of flood report higher 

levels of depression and anxiety, with these impacts possibly persisting for several years. 

Disasters present a heavy burden on the mental health of children when there is forced 

displacement from their home or a loss of family and community stability. Increased use of 

alcohol and tobacco are common following disasters as well as droughts. Higher temperatures 

can lead to an increase in aggressive behaviors, including homicide. 

Groups potentially more vulnerable include the elderly, pregnant women, people with 

preexisting mental illness, the economically disadvantaged, tribal and Indigenous communities, 

and first responders. Social cohesion, good coping skills, and preemptive disaster planning are 

examples of adaptive measures that can help reduce the risk of prolonged psychological impacts. 

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Adaptation can protect and promote population health today and in the future 

Targeted policies and programs are needed to protect vulnerable populations, and healthcare 

systems must become more resilient. The NCA4 concluded: 

Proactive adaptation policies and programs reduce the risks and impacts from climatesensitive health outcomes and from disruptions in healthcare services. Additional benefits 

to health arise from explicitly accounting for climate change risks in infrastructure 

planning and urban design. 

Individuals, communities, public health departments, healthcare facilities, organizations, and 

others are taking action to reduce health and social vulnerabilities to current climate change and 

to increase resilience to the risks projected in coming decades2• 

Examples of state-level adaptation actions include conducting vulnerability and adaptation 

assessments, developing comprehensive response plans (such as for extreme heat), climateproofing healthcare infrastructure, and implementing integrated surveillance of climate-sensitive 

infectious disease that can incorporate short-term to seasonal forecasts (such as for Lyme disease 

or dengue fever)2• Incorporating climate projections into emergency preparedness and disaster 

risk management can increase preparedness for changing weather patterns. 

Local efforts include altering urban design (for example, by using cool roofs, tree shades, and 

green walkways) and improving water management (for example, via desalination plants or 

watershed protection?. These can provide health and social justice benefits, elicit neighborhood 

participation, and increase resilience for specific populations, such as outdoor workers. 

Early warning and response systems can protect population health now and provide a basis for 

more effective adaptation to future climate2• Improvements in forecasting weather and climate 

conditions and in environmental observation systems, in combination with social factors, can 

provide information on when and where changing weather patterns could result in increasing 

numbers of cases of, for example, heat stress or an infectious disease. 

Adaptation is needed for our healthcare infrastructure. For example, in coastal regions, many 

hospitals and clinics are located in areas subject to flooding, as was witnessed in Houston, 

Miami, and Puerto Rico following hurricanes in 20172• This also is true in many other coastal 

communities. Mapping which hospitals may be subject to various levels of inundation is an 

important step; figure 5 shows the locations of hospitals in Charleston County, South Carolina, 

and Miami-Dade County, Florida, with respect to storm surge inundation for different categories 

of hurricanes making landfall at high tide2• Colors indicate the lowest category hurricane 

affecting a given location, with darker blue shading indicating areas with the greatest 

susceptibility to flooding and darker red dots indicating the most vulnerable hospitals. Four of 

the 38 (1 1%) hospitals in Miami-Dade County face possible storm surge inundation following a 

Category 2 hurricane; this could increase to 26 (68%) following a Category 5 hurricane. 

Charleston hospitals are more exposed to inundation risks. Seven of the II (64%) hospitals in 

Charleston County face possible storm surge inundation following a Category 2; this could 

increase to 9 (82%) following a Category 4. The impacts of a storm surge will depend on the 

effectiveness of resilience measures, such as flood walls, deployed by the facilities. 

13 
69 

J:igure 5: Hospitals at risk from storm surge by hurricanes in Miami-Dade Coun(v, Florida 

and Charleston County, South Carolina 

Charleston County, SC Charleston, SC Inset Area 

Miami-Dade County, FL Miami, FL Inset Area 

Hurricane Flooding 

111111 Category 1 Ill!!!! Category 2 lliiiil Category 3 CJ Category 4 CJ Category 5 

Hospital Flooding by Hurricane Category 

• None • Category 1 • Category 2 I) Category 3 0 Category 4 0 Category 5 

Data from National Hurricane Center 20 I 8 and the Department of Homeland Security 2018 

In addition, healthcare facilities may benefit from modifications to prepare for potential future 

extreme weather and climate events. For example, Nicklaus Children's Hospital, formerly Miami 

Children's, invested $!!.3 million in a range of technology retrofits, including a hurricaneresistant shell, to withstand Category 4 hurricanes for uninterrupted, specialized medical care 

services2 . The hospital was able to operate uninterrupted during Hurricane Irma and provided 

shelter for spouses and families of storm-duty staff and some storm evacuees. 

14 
70 

Adaptation efforts outside the health sector can have health benefits when, for example, 

infrastructure planning is designed to cool ambient temperatures and attenuate storm water 

runoff and when interagency planning initiatives involve transportation, ecosystem management, 

urban planning, and water management2. Adaptation measures developed and deployed in other 

sectors can harm population health if they are developed and implemented without taking health 

into consideration. 

Health co-benefits of mitigation policies and technologies 

Most policies to reduce emissions have health benefits for the health of Americans in the near 

and long term. The NCA4 concluded: 

Reducing greenhouse gas emissions would benefit the health of Americans in the near 

and long term. By the end of this century, thousands of American lives could be saved 

and hundreds of billions of dollars in health-related economic benefits gained each year 

under a pathway of lower greenhouse gas emissions. 

Policies to reduce greenhouse-gas emissions in the energy sector, housing, and the built 

environment more generally (ranging from buildings to parks); transportation; and agriculture 

and food systems can result in near-term benefits to human health6• These benefits can arise from 

reduced exposure to air pollution, particularly fine particulates (particulate matter with a 

diameter of :<:=2.5 Jlll1 (PM2.5), including black carbon) and ground-level ozone (levels of which 

may increase with climate change). 

There is a growing literature in which the health benefits of reductions in air pollution as a result 

of climate-change mitigation strategies are quantified. For example, under a scenario of lower 

greenhouse gas emissions (RCP4.5), by the end of this century, thousands of lives could be saved 

and hundreds of billions of dollars of health-related costs could be avoided compared to a 

scenario of higher emissions (RCP8.5)2• Annual health impacts (including from temperature 

extremes, poor air quality, and vector-borne diseases) and health-related costs are projected to be 

approximately 50% less under lower greenhouse gas emissions (RCP4.5) than under higher 

emissions (RCP8.5). The projected lives saved and economic benefits are likely to underestimate 

the true value because they do not include benefits of impacts that are difficult to quantify, such 

as mental health or long-term health impacts. 

For example, figure 6 shows estimated changes in annual net mortality due to extremely hot and 

cold days in 49 U.S. cities for 2080-2099 as compared to 1989-20002• Across these cities, the 

change in mortality is projected to be an additional 9,300 deaths each year under higher 

greenhouse gas emissions (RCP8.5) and an additional 3,900 deaths each year under lower 

emissions (RCP4.5). There is an approximate 50% reduction in these estimates under the 

assumption that the human health response to extreme temperatures in all 49 cities was equal to 

that of Dallas today (for example, as a result of availability of air conditioning or physiological 

adaptation). For example, in Atlanta, an additional 349 people are projected to die from extreme 

temperatures each year by the end of century under RCP8.5. Assuming residents of Atlanta in 

2090 have the adaptive capacity of Dallas residents today, this number is reduced to 128 

additional deaths per year. 

IS 
71 

Figure 6; Projected change in annual extreme temperature-related mortality2 

Lower Scenario Change in Mortality Rate 

(RCP4.5) 

Higher Scenario 

(RCP8.5) (deaths per 100,000 people) 

.10.1-12.0 

88.1-10.0 

86.1-8.0 

C) 4.1-6.0 

0 2.1-4.0 

0 0.0-2.0 

Cities without circles should not be interpreted as having no extreme temperature impact. Data 

were not available for the U.S. Caribbean, Alaska, and Hawaii and the U.S.-Affiliated Pacific 

Islands regions. 

Other examples include:2 

• Under higher emissions (RCP8.5), almost two billion labor hours are projected to be lost 

annually by 2090 from the impacts of temperature extremes, costing an estimated $160 

billion in lost wages (2015 dollars). States within the Southeast and Southern Great Plains 

regions are projected to experience higher impacts, with labor productivity in jobs with 

greater exposure to heat projected to decline by 3%. Some counties in Texas and Florida 

are projected to experience more than 6% losses in annual labor hours by the end of the 

century. 

• Annual national cases of West Nile neuroinvasive disease are projected to more than 

double by 2050 due to increasing temperatures, among other factors, resulting in 

approximately $1 billion per year in hospitalization costs and premature deaths under 

higher emissions (RCP8.5; 2015 dollars).ln this same scenario, an additional3300 cases 

and $3.3 billion in costs (2015 dollars) are projected each year by the end of the century. 

Approximately half of these cases and costs would be avoided under lower emissions 

(RCP4.5). 

• By the end of the century, warming under a higher scenario (RCP8.5) is projected to 

increase the length oftime recreational waters have concentrations of harmful algal 

blooms (cyanobacteria) above the recommended public health threshold by one month 

annually; these bacteria can produce a range of toxins that can cause gastrointestinal 

illness, neurological disorders, and other illnesses. The increase in the number of days 

where recreational waters pose this health risk is almost halved under lower emissions 

(RCP4.5). 

Although the health benefits of policies to reduce carbon emissions are potentially large, there 

may be unintended adverse consequences6. An example is the introduction of diesel engines that 

were sometimes promoted to reduce greenhouse-gas emissions but release more fine particulates 

and nitrogen oxides than gasoline engines. Poorly designed food and agricultural policies to 

reduce greenhouse-gas emissions could threaten food security by limiting protein sources and 

16 
72 

increasing food prices for the poor. In addition, increased exposure to household air pollution 

could result from improving the energy efficiency of households through the use of insulation 

and draft proofing without improving ventilation. Mitigation policies must consider and 

minimize these potential harmful effects. 

Con elusion 

Climate change is affecting the health of Americans, with the magnitude and pattern of future 

harms dependent on the urgency and level of ambition in designing and implementing adaptation 

and mitigation measures that will promote and protect our health and our public health and 

healthcare infrastructure as the climate continues to change. 

17 
73 

Kristie L. Ebi is director of the Center for Health and the Global Environment (CHanGE), and Rohm and 

Haas Endowed Professor in Public Health Sciences at the University of Washington. She has been 

conducting research and practice on the health risks of climate variability and change for more than 

twenty years, including on extreme events, thermal stress, foodbome safety and security, and vectorbome 

diseases. She focuses on understanding sources of vulnerability; estimating current and future health risks 

of climate change; designing and implementing adaptation policies and measures to reduce the risks of 

climate change in multi-stressor environments; and on estimating the health co-benefits of mitigation 

policies and technologies. She has supported multiple countries in Central America, Europe, Africa, Asia, 

and the Pacific in assessing their vulnerability and implementing adaptation measures. She co-chairs the 

International Committee On New Integrated Climate change assessment Scenarios (!CONICS), 

facilitating development of new climate change scenarios; chairs the National Academies Board on 

Environmental Change and Society; and co-chairs the National Academies Committee to Advise the U.S. 

Global Change Research Program. Dr. Ebi's scientific training includes an M.S. in toxicology and a Ph.D. 

and a Masters of Public Health in epidemiology, and two years of postgraduate research at the London 

School of Hygiene and Tropical Medicine. She has edited five books on aspects of climate change and 

has more than 200 publications. 
74 

Chairwoman JOHNSON. Thank you very much. 

We’re going to return now to our first witness. No? She’s not 

quite ready. 

Let me thank all of the witnesses. We now will go to our first 

round of questions. I will go through a few questions I have at the 

beginning. 

Last month’s government shutdown lasted for 35 days. During 

that time, many Federal science activities were put on hold. While 

some essential activities continued like the National Weather Service forecast, many other activities stopped entirely like updates to 

NOAA’s climate and hurricane models. There were also staffing 

issues like the National Center for Environmental Protection, 

which had just one person out of 200 on staff during the shutdown. 

These questions are for any or all of you that would like to respond. First question, what are the short- and long-term impacts 

of a government shutdown on Federal climate science? And with 

the United States currently a global leader in climate science, how 

do government shutdowns risk the U.S. leadership in producing top 

climate science? And what impact does it have on the rest of the 

world? We are heading to another potential shutdown, but hopefully it won’t occur. But what are the top risks of our climate 

science enterprise when or if another shutdown is a reality? 

You can start, Dr. Kopp. 

Dr. KOPP. Sure. I’ll just give a couple quick examples. So during 

the last shutdown, I was at an IPCC lead author meeting in Vancouver, and there were several of our co-authors who couldn’t make 

it there because of the shutdown. And then of course, if you’re looking at a large collaboration, having people who not only can’t be 

there but also can’t even be there remotely sort of makes you an 

unreliable partner, right? And so if you ask, how does this affect 

U.S. leadership, well, if we are an unreliable partner in international collaborations, that does make it harder for us to be a 

leader. 

Another example, one of my co-authors at NOAA, we’re working 

on a paper together, he didn’t have access to his computer or data 

during the shutdown, and so all of the analyses that might’ve happened during that time were stalled. It’s one thing if this is a couple of weeks, but if it’s a chronic condition, this really accumulates. 

Dr. FRANCIS. I would just add to what Dr. Kopp has mentioned. 

There were several major scientific conferences that occurred during the shutdown, and a large number of government employees 

were just unable to attend and present the research that they’d 

been working on for literally years, which is a huge detriment to 

their careers. Also, several field programs that were supposed to 

occur could not, so in some cases those field programs maybe won’t 

happen ever or at least they’ll be delayed for a year or more because there’s a lot of planning and logistics that have to be lined 

up to make those field programs work. There was also a big delay 

in processing proposals for more research or processing reports on 

that research, and all of that just delays the progress of science. 

Chairwoman JOHNSON. Thank you. 

Dr. EBI. To add to the other comments, everything you heard so 

far this morning about climate change is driven by data, and those 

data need to be collected. Equipment is not perfect, as we saw so 
75 

far this morning, and someone needs to go out and fix equipment. 

There are various things that need to take place to make sure that 

you continue those data series. You can’t make up data that you 

can’t go back and regenerate what you didn’t collect, and so having 

these gaps where we don’t have our critical Federal employees taking care of collecting the data that we need so critically to provide 

the science you need to make informed decisions. 

Chairwoman JOHNSON. Thank you very much. Now, according to 

the IPCC’s special report, limiting global warming to 1.5 centigrade 

over the long-term would, compared to 2, provide clear benefits to 

people and natural ecosystems. However, it would also require 

rapid far-reaching and unprecedented changes in all aspects of society to achieve decarbonization of our economy. 

So for each panelist, if you would just comment, what are the potential costs of failing to limit warming to 1.5 centigrade? The witnesses can speak to their own areas of expertise in societal, economic, and environmental impacts. 

Dr. KOPP. Well, I mean, there are a number of risks that accumulate the more carbon dioxide we put in. More heat waves lead 

to more mortality, as we’ve heard from our other speakers. Sealevel rise will be somewhat higher under 2 degrees versus 1.5 degrees, and so that leads to more coastal flooding. 

Both of those goals are heavy lifts, and so, the most important 

thing to keep in mind, I would argue, is that to stabilize climate 

at any level we need to get net global greenhouse gas emissions to 

zero. And I think it’s important we recognize the more warming we 

let happen, the more the risks accumulate, but we’ve got to keep 

that goal as our centerpiece, net global—net-zero global greenhouse 

gas emissions. 

Dr. FRANCIS. And I would just reiterate the fact that we are already seeing a large increase in the occurrence of extreme weather 

events and the intensity of many of those types of events, and 

that’s only going to get worse as the globe continues to warm. 

And I just wanted to add also that it may seem arbitrary to pick 

1.5 or 2.0-degree warming of the earth, but that’s actually a very 

useful thing to do because we can use these very sophisticated climate models that have been developed by many groups over many 

years to simulate the kinds of extreme events and the kinds of 

changes in the physical climate system that would occur under 

both of those scenarios. They’re very useful for helping us visualize 

what the world would look like under those two different kinds of 

conditions, and by doing that, we can see we really don’t want a 

world with a 2-degree warming, and we certainly don’t want to go 

past that, so it’s a very useful exercise to go through visualizing 

these endpoints. 

Dr. MAJKUT. Yes, I would echo my colleagues that the way I 

think about climate risk as we progress through these various temperature levels is the planet doesn’t really care about it being 

1.5 °C or 2 °C, but the risks accumulate as we go higher and higher 

up through warming levels. 

The thing that jumped out to me as I was preparing for the hearing was the effect on coral reefs, funny enough. At 1.5 °C scientists 

are projecting that up to 90 percent of coral reefs globally will be 

substantially diminished by warming events, and at 2 °C that num-
76 

ber goes to over 99 percent, which would be utterly devastating. So 

when we think about these global targets, we could really interpret 

it—interpret those low-temperature targets as being hedges, right, 

looking to avoid catastrophic impacts on particular systems. 

Chairwoman JOHNSON. Dr. Ebi? 

Dr. EBI. Another critical conclusion of the Special Report on 

Global Warming of 1.5 is that it is possible to stay below 1.5 °C, 

and we can do that with current technologies. We have to increase 

our level of ambition. We have to be more proactive, but it’s not 

impossible. So there is both the message that it’s critical that we 

do so and that it’s possible to make that commitment to stay below 

1.5. 

And as the other speakers mentioned, as we increase from today, 

which is 1 °C above preindustrial to 1.5 to 2 degrees, that each unit 

of warming is associated with adverse consequences for our health, 

our livelihoods, our ecosystems, and for our economies. 

Chairwoman JOHNSON. Thank you very much. Before we proceed, 

I think we might have Dr. Mahowald ready for testimony. You may 

proceed. 

TESTIMONY OF DR. NATALIE M. MAHOWALD, 

IRVING PORTER CHURCH PROFESSOR OF ENGINEERING, 

FACULTY DIRECTOR FOR THE ENVIRONMENT, 

ATKINSON CENTER FOR A SUSTAINABLE FUTURE, 

CORNELL UNIVERSITY 

Dr. MAHOWALD. Chairwoman Johnson, Ranking Member Lucas, 

and distinguished Members of the Committee, thank you for the 

opportunity to testify at today’s hearing on the state of climate 

science and why it matters. I’d also like to thank the technical staff 

in the House and here at Cornell for making this happen. 

My name is Natalie Mahowald. I’m a Professor of Atmospheric 

Sciences at Cornell University with over 20 years’ research expertise in climate science. I’m here today because—to explain why climate science matters and to put simply, it matters because the 

health and well-being of Americans matter, the U.S. economy matters, national security matters, and ensuring that the next generation of citizens can enjoy a better lifestyle than we do matters. 

Over the past year, we’ve witnessed record-breaking storms, precipitation, heat waves, fires, and flooding, all of which show the 

power of weather and the potential for changes in climate to harm 

human lives and livelihoods. At the same time, we’re witnessing a 

global revolution in the development of innovative new technologies 

that hold the promise of delivering a low-carbon-emitting future. 

China and Europe in particular are investing heavily in these new 

technologies. The United States can take a leadership role in business, science, and technology to bring both clean energy and new 

jobs to thousands of Americans. 

These topics—climate change, its impacts, and the technologies 

to mitigate and adapt its effects—were the subject of the IPCC’s 

special report on limiting warming to 1.5 °C, on which I was a lead 

author. This report comes at a critical time when we are rejecting 

the old-fashioned view that either we protect the environment or 

we promote business. The goal of the report is to identify solutions 
77 

to reach low-climate targets while promoting economic growth and 

eradicating poverty. 

Scientific evidence is clear that human activities have caused 

warming of 1.0 °C since the late 1800s. If we keep warming at the 

same rate, we will pass 1.5 °C around 2040. Past emissions alone, 

however, are unlikely to cause 1.5 degrees warming. In other 

words, if we can cut emissions quickly enough, we can arrest the 

Earth’s warming trends, keep temperatures below 1.5 degrees. This 

would require extremely ambitious emission cuts, 45 percent reduction in global emissions by 2030, which is much more ambitious 

than agreed to by the Paris Agreement and the voluntary reduction. In fact, the voluntary reductions agreed to through the Paris 

Agreement are likely to result in a warming of perhaps 3 °C. While 

this falls short of the stated goals of the Paris Agreement where 

governments agreed to keep warming below 2 degrees, it is much 

lower than the business-as-usual scenarios of up to a 5-degree increase in warming by 2100. 

The climate impacts will be lower at lower temperatures. Adaptation to climate change is easier at lower temperatures, but it’s 

still going to be required. Whatever temperature target policymakers set as a goal, the 1.5 report provides a menu of policy options from which they can choose. This report also suggests an 

array of technologies and techniques across many sectors that may 

be deployed to strengthen the response to climate change. Combined, these policies, technologies, and techniques can help reduce 

climate change impacts either through mitigation or adaptation 

and are appropriate for any climate target. For example, reducing 

subsidies for fossil fuels or removing regulatory barriers for new 

energy-producing technology and promoting a stable business environment to low-carbon technologies and techniques can create jobs, 

save money, improve health, and mitigate climate change. 

Promoting policies at the local, State, and Federal levels that 

move existing financing into new areas of research development 

and deployment for the energy industry, transportation, agriculture, and building sectors can create new business opportunities 

and technologies while mitigating for climate. 

Finally, an important new area of research will be carbon dioxide 

removal and utilization technology. The world is very different 

today than it was 50 years ago in terms of how we live, how we 

interact with each other, virtually and in person, and globally. The 

world in 50 years will again be different, and the challenge of climate change will be one of the key ways that define our future in 

terms of mitigation and adaptation to climate change. Keeping 

America in a business and technological leadership role requires 

thoughtful investment in research development and deployment 

and innovative technologies and techniques that our international 

competitors are already investing in and will result in a more prosperous, healthier, safer America and world. 

Thank you for the opportunity to testify. I look forward to your 

questions. 

[The prepared statement of Dr. Mahowald follows:] 
78 

Statement to the 

Committee on Science, Space and Technology 

Of the United States House of Representatives 

Hearing on 

"The State of Climate Science and Why it Matters" 

February 12, 2019 

Natalie Mahowald 

Irving Porter Church Professor of Engineering 

Department of Earth and Atmospheric Sciences 

and 

Faculty Director, 

Atkinson Center for a Sustainable Future 

Cornell University 
79 

Chairwoman Johnson, Ranking Member lucas and distinguished members of the committee: 

thank you for the opportunity to testify at today's hearing on the State of Climate Science and 

Why it Matters. 

My name is Natalie Mahowald. I am the Faculty Director for the Atkinson Center for a 

Sustainable Future at Cornell University, as well as the Irving Porter Church Professor of 

Engineering in the area of Atmospheric Sciences in the Department of Earth and Atmospheric 

Sciences. I have research expertise in climate change science for over 20 years. 

I have been asked to present to the Committee results from the Intergovernmental Panel on 

Climate Change's Special Report on Limiting Warming to 1.5C (the "1.5 report"), on which I was 

a lead author. As an attachment to my written testimony, I would like to submit for the record a 

copy of the summary for policy makers from the Special Report on 1.5C. 

The Intergovernmental Panel on Climate Change is overseen by the United Nations 

Environment Programme and the World Meteorological Organization. The purpose of the IPCC 

is to assess scientific and socioeconomic information for policymakers to help them make 

informed decisions. The IPCC organizes the scoping, writing and approval of assessment 

reports, which undergo strict review and scrutiny by the scientific community before also being 

approved by the government approval session of the IPCC 1. Assessment reports do not report 

new research, nor do they contain the scientific opinions of a few scientists, but rather they are 

a consensus view of the scientific literature. All of the results included in the summary for 

policymakers represent those in which the scientific community has medium or high 

confidence, meaning that multiple scientific papers, with different authors and using different 

approaches, came to the same conclusion. Thus, these reports are meant to be as helpful as 

possible for policymakers by providing them only with information representing the consensus 

view of current scientific literature. 

There were 91 authors from 44 countries (including several from the United States) who wrote 

the 1.5 report. Another 133 scientists contributed elements to the report. The report was 

reviewed three times by experts, which included over 42,000 comments from more than 1,000 

reviewers. Each comment was considered and responded to by the authors. The Summary for 

Policymakers for the report was approved line-by-line by all the governments participating in 

the IPCC as representing both the underlying report and the peer reviewed scientific literature. 

Each of the previous IPCC reports have all undergone a similarly robust review to ensure that 

they represent the consensus view of the scientific literature. 

The 1.5C report was unique in several ways. First, this was the first IPCC report to be 

specifically requested by governments. Second, the mandate for the report was extremely 

broad: not only was the goal to access the impacts of limiting warming to 1.5C but to also 

examine how efforts to limit warming to 1.5C might strengthen the global response to the 

1 https://www.ipcc.ch/2018/10/08/summary-for-policymakers-of-ipcc-special-report-on-global-warming-of-1-Scapproved-by-governments/ 
80 

threat of climate change, promote sustainable development and increase efforts to eradicate 

poverty2• Finally, this particular report comes at a critical time when we are rejecting the oldfashioned view that either we protect the environment OR we promote businesses and 

eradication of poverty. The goal of the 1.5C report was to identify solutions that will protect 

the environment WHILE promoting economic growth and eradicating poverty. In other words, 

this report focuses on identifying ways to create sustainable development and mitigation 

strategies to reach low climate targets, while also protecting us against the climate change that 

we cannot avoid. 

For many years, the scientific consensus on climate change has been clear, with over 97% of 

climate scientists agreeing that human-caused climate change is a problem we need to 

address3• This has been seen in IPCC reports, National Assessment Reports, including the 4th 

assessment released this year, 4 as well as review documents from the United States' most 

esteemed scientists in the National Academies.5 

The consensus of the scientific evidence clearly demonstrates that human activities have 

caused l.OC of global warming since the late 1800s. Current trends suggest that if we keep 

warming at the same rate, we will pass 1.5C around 2040. Without concerted climate action, 

some estimates suggest warming of 4-5C by 2100. 

Past emissions alone, however, are unlikely to cause 1.5C of warming. In other words, if we can 

cut net emissions quickly enough, we can arrest the earth's warming trends and keep 

temperatures below 1.5C. This would require extremely ambitious emission cuts-a 45% 

reduction in global emissions by 2030, much more ambitious than agreed to by the Paris 

Agreement. For example, the emission reductions voluntarily agreed to by different countries 

as part of the Paris Agreement are likely to result in warming of about 3.0C by 2100 6• While 

this falls short of the stated goals of the Paris agreement, where governments agreed to try to 

keep warming below 2.0C, it is much lower than the business-as-usual scenarios of perhaps 5C 

warming at 2100, assuming only technological innovation.7 

We are already seeing the impact of climate change on extreme events, for example an 

increase in the intensity of precipitation, increased heat waves and droughts. A new set of 

research completed in time for the 1.5C report looked at the importance of only 0.5C warming 

on extreme events. These studies focused on, for example, the difference between a warming 

of 0.5C and the 1.0C of today using historical data, or between 1.0 and 1.5C in future climate 

projections, and they suggest that even small changes, such as 0.5C warming, can have 

significant impacts on humans and ecosystems. In addition, the climate impacts from 1.5 C 

2 https://www.ipcc.ch/2018/10/08/summary-for-policymakers-of-ipcc-special-report-on-global-warming-of-1-5capproved-by-governments/ 

3 https:Uclimate.nasa.gov/scientific-consensus/ 

4 https:f/nca2018.globalchange.gov/ 

5 https:j /www.nap.edu/ catalog/18730/climate-change-evidence-and-causes 6 https:ljreport.ipcc.ch/sr15/index.html (Summary for Policy Makers,Dl.l, page 20) 7 https:ljwww.ipcc.ch/report/arS/syr/ (Summary for Policy Makers: SPM2.2, page 10) 
81 

global warming are less than that from 2.0C or higher temperatures. Overall, the lower we can 

keep the global warming, the less climate impacts there will be (Figure 2 from the report}. 

How the level of global warming affects impacts and/or risks associated with 

the Reasons for Concern (RFCs) and selected natural, managed and human 

systems 

Five Reasons For Concern (RFCs) illustrate the impacts and risks of 

different levels of global warming for people, economies and ecosystems 

across sectors and regions. 

Impacts and risks associated with the Reasons for Concern (RFCs) 

f. 

·Vo,high 

M('l(h>rate . 

Undcl€ctabt~ 

Impacts and risks for selected natural, managed and human systems 

White indicates that no 

change. 

Adaptation to climate change at the current l.OC or at a potential future at l.SC is much easier 

than at higher temperatures, but will still be required in agricultural lands and cities, and 

especially in low-lying regions. The poor and vulnerable will be much more able to adapt if the 

level of global warming is lower. In other words, the lower the anthropogenic temperature 

changes are kept, the easier it will be for both ecosystems and people to adapt. Making sure 

that new infrastructure investments are consistent with future climate projections is vital to 

both mitigation and adaptation efforts. 
82 

Ambitious mitigation will be required to keep climate change below l.SC. This includes 

strategies such as conversion to sustainable energy- wind or solar, for example- and adoption 

of sustainable agricultural practices as quickly as possible. Changes in individual behaviors such 

as energy conservation or shifts in diet can also make a huge difference in cutting emissions. In 

addition, development of new technologies or methods to remove carbon dioxide from the 

atmosphere are likely to be required to keep global warming below l.SC. Scenarios that keep 

warming below l.SC are shown in Figure 3a from the l.SC report below 

Global emissions pathway dmracte:ristiu 

General ch.,..cteristics of the evolu1!on ol anthropogenic net emissions of C(h, and total emissions o! 

!SCw!thnoor 

illustrated in figure Sl'M3S. 

Global total net CO> emissions 

While limiting warming to 1.5C may not be the pathway chosen by policymakers, the 1.5 C 

report provides a menu of policy choices from which policymakers- who hail from different 

regions and face different challenges- may choose. The LSC report also suggests an array of 

technologies and techniques across many sectors that could be deployed to help strengthen 

the response to the threat of global warming. Combined, these policies and technologies can 

help reduce climate change impacts either through mitigation or adaptation and they are 
83 

appropriate for any climate target. For example, reducing subsidies or regulatory environments 

that make fossil fuel energy sources less attractive, while incentivizing stable business 

investment and public-private partnerships in low carbon energies and industry can create jobs, 

save money and mitigate climate change. Promoting policies at the local, state and federal 

level that shift private and public financing into new areas of research, development and 

deployment for the energy, industry, transportation, agriculture and building sectors can create 

new business opportunities and technologies while also mitigating the effects of climate 

change. The l.SC report found that an important new area of research will be carbon dioxide 

removal and utilization technologies. Recent reports from the National Academies also show 

the promise of a well-organized research agenda in this area8. 

Ambitious cuts in emissions can be consistent with ensuring people around the world are 

healthy, prosperous and supplied with ample food, clean air and water. New energy 

production technologies such as solar and wind can be actually cheaper than older, dirtier 

fossil-fuel based technologies, and may in some cases require much less infrastructure. 

Development and deployment of similar low carbon technologies in other sectors remains an 

important area that needs addressing. The l.SC report shows that the goals of reaching low 

climate targets and other goals, such as prosperity and environmental protections, are not 

mutually exclusive. Indeed, limiting warming can go hand in hand with increasing economic 

prosperity. While much more action needs to be undertaken, the good news is momentum is 

beginning in the areas of research, development and deployment of innovative technologies 

and techniques. This Congress has an opportunity to build on that momentum to help the 

United States lead in the development of these new technologies and result in a more 

prosperous, healthier and safer world. 

Thank you again for the invitation to testify. I am happy to elaborate on any of these points or 

answer any questions the Committee may have. 

8 Negative Emissions Technologies and Reliable Sequestration: A Research 

Agenda. http://nap.edu/25259 and Gaseous Carbon Waste Streams Utilization: Status and 

Research Needs: http://nap.edu/25232 
84 

Attachment A 

Short Narrative Biography 

February 12, 2019 

Natalie Mahowald 
85 

Natalie Mahowald is the Irving Porter Church Professor of Engineering, in the area of 

Atmospheric Sciences at Cornell University in the Department of Earth and Atmospheric 

Sciences. She is also a Faculty Director for the Atkinson Center for a Sustainable Future. She 

earned her undergraduate degrees in Physics and German at Washington University in St. Louis 

in 1988, her M.S. in Natural Resource Policy at the University of Michigan, and her Ph.D. in 

Meteorology at MIT in 1996. She also worked in air pollution consulting and studied in 

Germany before her Ph.D. She did her postdoctoral work at Stockholm University, before moving 

to a faculty position at University of California, Santa Barbara. She then moved to the National 

Center of Atmospheric Research before starting as a faculty member at Cornell in 2007. 

She has numerous scientific awards to her name, including being named a Fellow of both the 

American Meteorological Society (20 11) and the American Geophysical Union (20 13 ), and being 

awarded a Guggenheim Fellowship (2013). She was named by Thompson ISI as a highly cited 

research for 2002-2012, and for each of the years since. She was the Henry G. Houghton 

Awardee from the Aemrican Meteorological Society (for best young atmospheric chemistry or 

physical meteorologist in 2006). She has over 170 peer reviewed publications, and a Web of 

Science H-factor of 68. 

She was a lead author on the Special Report on 1.5C from the Intergovernmental Panel on 

Climate Change just approved last October, as well as on the 5rh Assessment from the, Working 

Group 1 on the Physical science of Climate Change in 2013. 

The focus of Natalie's work is on natural feedbacks in the climate system, and how they 

responded in the past to natural climate forcings, and how they are likely to respond in the future. 

Much of her work focused on mineral aerosols, which are an excellent example of an earth 

system process: they both respond to climate, as well as force climate to change. She has also 

worked on fire, the carbon cycle, and more recently on understanding natural emissions of 

methane and nitrous oxide. 
86 

Attachment B 

IPCC Special Report: Summary for Policymakers 

February 12, 2019 

Natalie Mahowald 
87 
88 

Global warming of 1.5°( 

An IPCC Special Report on the impacts of global warming of 1 .SOC 

above pre-industrial levels and related global greenhouse gas emission pathways, 

in the context of strengthening the global response to the threat of climate change, 

sustainable development, and efforts to eradicate poverty 

Summary for Policymakers 

Valerie Masson-Delmotte 

Co-chair Working Group I 

Hans-Otto Portner 

Co-Chair Working Group II 

Jim Skea 

Co-Chair Working Group Ill 

Anna Pirani 

Head of WGI TSU 

Roz Pidcock 

Head of Communication 

Yang Chen 

Science Officer 

Elisabeth lonnoy 

Project Assistant 

Edited by 

Wilfran Moufouma-Okia 

Head of Science 

Sarah Connors 

Science Officer 

Xiao Zhou 

Science Assistant 

Panmao Zhai 

Co-Chair Working Group I 

Debra Roberts 

Co-Chair Working Group II 

Priyadarshi R. Shukla 

Co-Chair Working Group Ill 

Clotilde Pean 

Head of Operations 

J. B. Robin Matthews 

Science Officer 

Melissa I. Gomis 

Graphics Officer 

Tom Maycock Melinda Tignor Tim Waterfield 

Science Editor Head of WGII TSU IT Officer 

Working Group I Technical Support Unit 
89 

Front cover layout: Nigel Hawtin 

Front cover artwork: Time to Choose by Alisa Singer- www.environmentalgraphiti.org- ©Intergovernmental Pane! on Climate Change. 

The artwork was inspired by a graphic from the SPM {Figure SPM.1). 

© 2018lntergovernmental Panel on Climate Change. 

Printed October 2018 by the IPCC, Switzerland. 

Electronic copies of this Summary for Policymakers are available from the IPCC website www.lpcc.ch 

ISBN 978·92·9169·151-7 
90 
91 

Summary for Policymakers 

Summary 

for Policymakers 

Drafting Authors: 

Myles Allen (UK), Mustafa Babiker (Sudan), Yang Chen (China), Heleen de Coninck 

{Nether!ands/EU), Sarah Connors {UK), Ren€e van Diemen (Netherlands), Opha Pauline 

Dube {Botswana), Kristie l. Ebi (USA), Francois Engelbrecht (South Africa), Marion Ferrat 

(UKJFrance), James Ford (UK/Canada), Piers Forster (UK), Sabine Fuss (Germany), Tania 

Guillen Bolafios (Germany/Nicaragua), Jordan Harold (UK), Ove Hoegh-Gu!dberg {Australia), 

Jean-Charles Hourcade (France), Daniel Huppmann (Austria), Daniela Jacob (Germany), 

Kejun Jiang (China), Tom Gabriel Johansen (Norway), Mikiko Kainuma (Japan), Kiane de 

Kleijne (Netherlands/EO), Elmar Kriegler (Germany), Debora ley (Guatemala/Mexico), 

Diana Liverman (USA), Natalie Mahowald (USA), Valerie Masson-Delmotte (France), 

J. B. Robin Matthews (UK), Richard Millar (UK), Katja Mintenbeck (Germany), Angela Morelli 

(Norway/Italy), Wilfran Moufouma-Okla (France/Congo), luis Mundaca {Sweden/Chile), 

Maike Nicolai (Germany), Chukwumerije Okereke (UK/Nigeria}, Minai Pathak (India), Antony 

Payne (UK), Roz Pidcock (UK), Anna Pirani (Italy), Elvira Poloczanska {UK/ Australia), HansOtto POrtner {Germany), Aromar Revi (India), Keywan Riahi (Austria), Debra C Roberts 

(South Africa), Joeri Rogelj (Austria/Belgium), Joyashree Roy (India), Sonia I. Seneviratne 

(Switzerland), Priyadarshi R. Shukla (India), James Skea (UK), Raphael Slade (UK), Drew 

Shindel! (USA), Chandni Singh (India), William Solecki (USA), Linda Steg (Netherlands), 

Michael Taylor (Jamaica), Petra Tschakert (Australia/Austria), Henri Walsman (France), 

Rachel Warren (UK), Panmao Zhai (China), Kirsten Zickfeld (Canada). 

This Summary for Po!icymakers should be cited as: 

!PCC, 2018: Summary for Pollcymakers !n: Global warming of 1.5°C. An JPCC Special Report on the impam 

of global warming of 15°C above pre-industria/levels and related global greenhouse gas emission pathways, 

in the context of strengthening the global response to the threat of climate change, sustainable development, 

and efforts to eradicate poverty {V. Masson·D€!motte, P. Zha~ H. 0. POrtner, D. Roberts, 1 S~ea, P. R. Shukla, 

A. Plran~ W. Moufouma·Olda, C. Pean, R. Pidcock, S. Connors, J. B. R. Matthews, Y. Ch~n. X. Zhou, M.l. Gomis, 

E. Lonnoy, T. Maycock, M. Tignor, T. Waterlie!d (eds.)J. World Meteorological Organization, GeneWJ, Switzerland, 

32pp. 

I 
92 

Summary for Policymakers 

I Acknowledgements 

We are very grateful for the expertise, rigour and dedication shown throughout by 

the volunteer Coordinating lead Authors and lead Authors, working across scientific 

disciplines in each chapter of the report, with essential help by the many Contributing 

Authors. The Review Editors have played a critical role in assisting the author teams and 

ensuring the integrity of the review process. We express our sincere appreciation to all the 

expert and government reviewers. A special thanks goes to the Chapter Scientists of this 

report who went above and beyond what was expected of them: Neville Ellis, Tania Guillen 

Bolanos, Daniel Huppmann, Kiane de Kleijne, Richard Millar and Chandni Singh. 

We would also like to thank the three Intergovernmental Panel on Climate Change (I PC C) 

Vice-Chairs Ko Barrett, Thelma Krug, and Youba Sokona as well as the members of the 

WGI, WG!I and WGI!l Bureaux for their assistance, guidance, and wisdom throughout the 

preparation of the Report: Amjad Abdulla, Edvin Aldrian, Carlo Carrara,. Oiriba Korecha 

Dadi, Fatima Drlouech, Andreas Fischlin, Gregory Flato, Jan Fuglestvedt, Marl< Howden, 

Nagme!din G. E. Mahmoud, Carlos Mendez, Joy Jacqueline Pereira, RamOn Pichs~Madruga, 

Andy Reisinger, Roberto sanchez Rodriguez, Sergey Semenov, Muhammad !. Tariq, Diana 

Orge-Vorsatz, Carolina Vera, Pius Yanda, Noureddine Yassaa, and Taha Zatari. 

Our heartfelt thanks go to the hosts and organizers of the seeping meeting and the 

four Special Report on 1.snc lead Author Meetings. We gratefully acknowledge the 

support from the host countries and institutions: World Meteorological Organization, 

Switzerland; Ministry of Foreign Affairs, and the National Institute for Space Research 

(INPE), Brazil; Met Office and the University of Exeter, the United Kingdom; Swedish 

Meteorological and Hydrological Institute {SMH!), Sweden; the Ministry of Environment 

Natural Resources Conservation and Tourism, the National Climate Change Committee 

in the Department of Meteorological Services and the Botswana Global Environmental 

Change Committee at the University of Botswana, Botswana; and Korea Meteorological 

Administration (KMA) and lncheon Metropolitan dty, the Republic of Korea. The support 

provided by governments and institutions, as well as through contributions to the IPCC 

Trust Fund, is thankfully acknowledged as it enabled the participation of the author 

teams in the preparation of the Report. The efficient operation of the Working Group I 

Technical Support Unit was made possible by the generous financial support provided by 

the government of France and administrative and information technology support from the 

Unlversite Paris Saday (France), lnstltut Pierre Simon laplace (IPSl) and the laboratoire des 

Sciences du Climat et de I'Environnement (lSCE). We thank the Norwegian Environment 

Agency for supporting the preparation of the graphics for the Summary for Policymakers. 

We thank the UNEP library, who supported authors throughout the drafting process by 

providing literature for the assessment. 
93 

We would also like to thank Abda!ah Mokssit, Secretary of the IPCC, and the staff of the 

IPCC Secretariat: Kerstin Stendahl, Jonathan lynn, Sophie Sch!ingemann, Judith Ewa, Mxolisi 

Shongwe, Jesbin Baidya, Werani Zabula, Nina Peeva, Joe!!e Fernandez, Annie Courtin, laura 

Biagioni and Oksana Ekzarkho. Thanks are due to Elhousseine Gouaini who served as the 

conference officer for the 48th Session of the !PC C. 

Finally, our particular appreciation goes to the Working Group Technical Support Units 

whose tireless dedication, professionalism and enthusiasm led the production of this 

Special Report. This report could not have been prepared without the commitment of 

members of the Working Group I Technical Support Unit, all new to the IPCC, who rose 

to the unprecedented Sixth Assessment Report challenge and were pivotal in aU aspects 

of the preparation of the Report: Yang Chen, Sarah Connors, Melissa Gomis. Elisabeth 

lonnoy, Robin Matthews, Wilfran Moufouma-Okia, C!otilde Pean, Roz Pidcock, Anna Plrani, 

Nicholas Reay, Tim Waterfield, and Xiao Zhou. Our warmest thanks go to the collegial and 

collaborative support provided by Mar!ies Craig, Andrew Okem, Jan Petzold, Melinda Tignor 

and Nora Weyer from the WGII Technical Support Unit and Bhushan Kankal, Suvadip Neogi 

and Joana Portugal Pereira from the WG!l! Technical Support Unit. A special thanks goes 

to Kenny Coventry, Harmen Gudde, lrene lorenzoni, and Stuart Jenkins for their support 

with the figures in the Summary for Policymakers, as well as Nigel Hawtin for graphical 

support of the Report. In addition, the following contributions are gratefully acknowledged: 

Jatinder Padda (copy edit), Melissa Dawes (copy edit), Marilyn Anderson (index), Vincent 

Gregoire {layout) and Sarah !e Rouzlc (intern). 

The Special Report website has been developed by Habitat 7, led by Jamie Herring, and 

the report content has been prepared and managed for the website by Nicholas Reay and 

Tim Watertield. We gratefully acknowledge the UN Foundation for supporting the website 

development 

Summary for Policymakers 

I 
94 

I 

Summary for Policymakers 

Introduction 

This Report responds to the invitation for JPCC ' ... to provide a Special Report in 2018 on the impacts of global warming of 1.5cc 

above pre-industrial levels and related global greenhouse gas emission pathways' contained in the Decision of the 21st Conference 

of Parties of the United Nations Framework Convention on Climate Change to adopt the Paris Agreement 1 

The JPCC accepted the invitation in April 2016, deciding to prepare this Special Report on the impacts of global warming of 

1 S'C above pre-industrial levels and related global greenhouse gas emission pathways, In the context of strengthening the global 

response to the threat of climate change, sustainable development, and efforts to eradicate poverty. 

This Summary for Policymakers (SPM) presents the key findings of the Special Report, based on the assessment of the available 

scientific, technical and socio-economic literature2 relevant to global warming of 1.5°( and for the comparison between global 

warming of 1.5°( and 2°( above pre-industrial levels. The level of confidence associated with each key finding is reported using 

the IPCC calibrated language.3 The underlying scientific basis of each key finding is indicated by references provided to chapter 

elements. In the SPM, knowledge gaps are identified associated with the underlying chapters of the Report. 

A. Understanding Global Warming of 1 .SOC' 

A.1 Human activities are estimated to have caused approximately 1.0°C of global warmings above 

pre-industrial levels, with a likely range of o.s•c to 1.2'C. Global warming is likely to reach 1.5"C 

between 2030 and 2052 if it continues to increase at the current rate. (high confidence) (Figure 

SPM.1){1.2} 

A.1.1 Reflecting the long-term warming trend since pre-industrial times, observed global mean surface temperature (GMST) for 

the decade 2006-2015 was 0.87'( (likely between 0.75'( and 0.99'()5 higher than the average over the 1850-1900 

period (vety high confidence). Estimated anthropogenic global warming matches the level of observed warming to within 

±20C'Io (likely range}, Estimated anthropogenic global warming is currently increasing at 0.2°( (likely between 0.1 °( and 

0.3°C) per decade due to past and ongoing emissions (high confidence). {1.2.1, Table 1.1, 1.2.4} 

A.1.2 Warming greater than the global annual average is being experienced in many land regions and seasons, including two to 

three times higher in the Arctic. Warming is generally higher over land than over the ocean. (high confidence} {1.2.1, 1.2.2, 

Figure 1.1, Figure 1.3, 3.3.1. 3.3.2} 

A.1.3 Trends in intensity and frequency of some climate and weather extremes have been detected over time spans during which 

about 0.5°( of global warming occurred (medium confidence). This assessment is based on several lines of evidence, 

including attribution studies for changes in extremes since 1950. {3.3.1, 3.3.2, 3.3.3} 

1 Decision 1fCP21,paragraph2L 

2 lheassessmentcoversliteratureacc~ptedfo•pubficationby1SMay2013. 

4 Seea\soBoxSPM.l.CmeCnnti'ptsCentraitothisSp&i31Report 

S Pre1€r! l~vel of global warming is defmed as the average of a ~O·year period c€n!re-d on 2017 assumi~g tre recent rate of warmmg continues. 
95 

Summary for Polic.ymakers 

A.2 Warming from anthropogenic emissions from the pre-industrial period to the present will persist for 

centuries to millennia and will continue to cause further long~term changes in the climate system, 

such as sea level rise, with associated impacts (high confidence), but these emissions alone are 

unlikely to cause global warming of 1.s•c (medium confidence). (Figure SPM.1){1.2, 3.3, Figure 1.5} 

A.2.1 Anthropogenic emissions (including greenhouse gases, aerosols and their precursors} up to the present are unlikely to 

cause further warming of more than 0.5°( over the next two to three decades (high confidence) or on a century time scale 

(medium confidence). {1.2.4, Figure 1.5} 

A.2.2 Reaching and sustaining net zero global anthropogenic COl emissions and declining net non·C02 radiative forcing would 

halt anthropogenic global warming on multi·decada! time scales (high confidence). The maximum temperature reached is 

then determined by cumulative net global anthropogenic C02 emissions up to the time of net zero C02 emissions (high 

confidence) and the level of non·C02 radiative forcing in the decades prior to the time that maximum temperatures are 

reached (medillm confidence). On longer time scales, sustained net negative global anthropogenic C02 emissions and/ 

or further reductions in non-C02 radiative forcing may still be required to prevent further warming due to Earth system 

feedbacks and to reverse ocean acidification (medium confidence) and will be required to minimize sea level rise (Mgh 

confidence). {Cross-Chapter Box 2 in Chapter 1, 1.2.3, 1.2.4, Figure 1.4, 2.2.1, 2.2.2, 3.4.4.8, 3.4.5.1, 3.6.3.2) 

A.3 Climate-related risks for natural and human systems are higher for global warming of 1.5"C than 

at present, but lower than at z•c (high confidence). These risks depend on the magnitude and rate 

of warming, geographic location, levels of development and vulnerability, and on the choices and 

implementation of adaptation and mitigation options (high confidence). (Figure SPM.2) {1.3, 3.3, 

3.4, 5.6} 

A.3.1 Impacts on natural and human systems from global warming have already been observed {high confidence). Many land and 

ocean ecosystems and some of the services they provide have already changed due to global warming (high confidence). 

(Figure SPM.2) {1.4, 3.4, 3.5) 

A.3.2 Future dimate~re!ated risks depend on the rate, peak and duration of warming. In the aggregate, they are larger if global 

warming exceeds 1.5°( before returning to that level by 2100 than if global warming gradually stabilizes at 1.5°(, especially 

if the peak temperature is high {e.g., about 2°() {high confidence). Some impacts may be long-lasting or irreversible, such 

as the loss of some ecosystems (high confidence). (3.2, 3.4.4, 3.6.3, Cross-Chapter Box 8 in Chapter 3} 

A.3.3 Adaptation and mitigation are already occurring (high confidence). Future climate-related risks would be reduced by the 

upscaling and acceleration of far-reaching, multilevel and cross·sectoral climate mitigation and by both incremental and 

transformational adaptation (high confidence). {1 .2, 1.3, Table 3.5, 4.2.2, Cross~Chapter Box 9 in Chapter 4, Box 4.2, Box 

4.3, Box 4.6, 4.3.1, 4.3.2, 4.3.3, 4.3.4, 4.3.5, 4.4.1, 4.4.4, 4.4.5, 4.5.3) 

I 
96 

I 

Summary for Policymakers 

Cumulative emissions of C02 and future non-C02 radiative forcing determine 

the probability of limiting warming to 1.5°C 

a) Observed global temperature change and modeled 

responses to stylized anthropogenic emission and forcing pathways 

Global warming relative to 1850·1900 ('C) 

Observed monthly global 

mean surface temperature 

c) Cumulative net C02 emissions 

Billion tonnes CO< (Gt(Q,) 

Non·COl radiative forcing 
97 

Summary for Policymakers 

B. Projected Climate Change, Potential Impacts and Associated Risks 

8.1 Climate models project robust' differences in regional climate characteristics between present-day 

and global warming of 1.5°C~8 and between 1.5°C and 2°(.8 These differences indude increases 

in: mean temperature in most land and ocean regions (high confidence), hot extremes In most 

inhabited regions (high confidence), heavy precipitation in several regions (medium confidence), 

and the probability of drought and precipitation deficits in some regions (medium confidence). 

{3.3} 

B.1. 1 Evidence from attributed changes in some climate and weather extremes for a global warming of about OS'C supports 

the assessment that an additional 0.5°( of warming compared to present is associated with further detectable changes in 

these extremes (medium confidence). Severa! regional changes in climate are assessed to occur with global warming up 

to 1.5°( compared to pre-industrial levels, including wanning of extreme temperatures in many regions (high confidence}, 

increases in frequency, intensity, and/or amount of heavy precipitation in several regions (high confidence), and an increase 

in intensity or frequency of droughts in some regions (medium confidence). {3.2, 3.3.1, 3.3.2, 3.3.3, 3.3.4, Table 3.2) 

8.1.2 Temperature extremes on land are projected to warm more than GMST (high confidence): extreme hot days in mid-latitudes 

warm by up to about 3°( at global warming of 1.5°( and about 4°( at 2°(, and extreme cold nights in high latitudes warm 

by up to about 4.5°( at 1.5°( and about 6°( at 2°( (high confidence). The number of hot days is projected to increase in 

most land regions. with highest increases in the tropics (high confidence). {3.3.1, 3.3.2, Cross-Chapter Box 8 in Chapter 3} 

8.1.3 Risks from droughts and precipitation deficits are projected to be higher at zoe compared to 1.5°( of global warming in 

some regions (medium confidence). Risks from heavy precipitation events are projected to be higher at 2°( compared to 

1.5°C of global warming in several northern hemisphere high-latitude and/or high-elevation regions, eastern Asia and 

eastern North America (medium confidence). Heavy precipitation associated with troplcal cyclones is projected to be 

higher at 2°( compared to 1.5°( global warming (medium confidence}. There is generally low confidence in projected 

changes in heavy precipitation at 2°( compared to 1.5°( in other regions. Heavy precipitation when aggregated at global 

scale is projected to be higher at 2°( than at 1.5°( of global warming (medium confidence). As a consequence of heavy 

precipitation, the fraction of the global land area affected by flood hazards is projected to be larger at 2oc compared to 

1.5°( of global warming (medium confidence). {3.3.1, 3.3.3, 33.4, 3.3.5, 3.3.6) 

8.2 By 2100, global mean sea level rise is projected to be around 0.1 metre lower with global warming 

of 1.5"C compared to 2"C (medium confidence). Sea level will continue to rise well beyond 2100 

(high confidence), and the magnitude and rate of this rise depend on future emission pathways. 

A slower rate of sea level rise enables greater opportunities for adaptation in the human and 

ecological systems of small islands. low-lying coastal areas and deltas (medium confidence). 

{3.3, 3.4, 3.6} 

8.2.1 Model-based projections of global mean sea level rise (relative to 1986-2005) suggest an indicative range of 0.26 to 0.77 

m by 2100 for 1.5"( of global warming, 0.1 m (0.04--0.16 m) less than for a global warming of zoe (medium confidence). 

A reduction of 0.1 m in global sea level rise implies that up to 10 million fewer people would be exposed to related risks, 

based on population in the year 2010 and assuming no adaptation (medium confidence). {3.4.4, 3.4.5, 4.3.2} 

8.2.2 Sea level rise will continue beyond 2100 even if global warming is limited to 1.5°( in the 21st century {high cont;dence). 

Marine ice sheet instability in Antarctica andfor irreversible loss of the Greenland ice sheet could result in multi-metre rise 

in sea level over hundreds to thousands of years. These instabilities could be triggered at around 1.5°( to 2°( of global 

warming (medium confidence). (figure SPM.2) {3.3.9, 3.4.5, 3.5.2, 3.6.3, Box 3.3} 

7 RobustishereusedtonH!anthatatleasttwothirdsofclimatemtxlel'ishowt'lesamesigr.ofchangf!satthegndpoint;,catl!,andthatdlffere!lcesinlargeregionsarestatistica!Iy 

~1gmf1cant 

8 Proje~t~d changes m impam between different l!'vt>ls of global warming dre determined with respect to chang!"> m global mean surface a1r temperature 

I 
98 

I 

Summary for Policymakers 

10 

B.2.3 Increasing warming amplifies the exposure of small islands, !ow~lying coastal areas and deltas to the risks associated with 

sea level rise for many human and ecological systems, including increased saltwater intrusion, flooding and damage to 

infrastructure (high confidence). Risks associated with sea level rise are higher at 2°( compared to 1.5°C. The slower rate 

of sea level rise at global warming of 1.5°( reduces these risks, enabling greater opportunities for adaptation including 

managing and restoring natural coastal ecosystems and infrastructure reinforcement (medium confidence). (Figure SPM.2) 

{3.45, Box 3.5] 

8.3 On land, impacts on biodiversity and ecosystems, including species loss and extindion6 are 

projected to be lower at 1.5'C of global warming compared to 2'C. Limiting global warming to 

1.5'C compared to 2'C is projected to lower the impacts on terrestrial, freshwater and coastal 

ecosystems and to retain more of their services to humans (high confidence). (Figure SPM.2) 

{3.4, 3.5, Box 3.4, Box 4.2, Cross-Chapter Box 8 in Chapter 3} 

8.3.1 Of 105,000 species studied,9 6% of insects, 8% of plants and 4% of vertebrates are projected to lose over half of their 

climatically determined geographic range for global warming of 1 S'C, compared with 18% of insects, 16% of plants and 

8% of vertebrates for global warming of zoe (medium confidence). Impacts associated with other biodiversity~related 

risks such as forest fires and the spread of invasive species are lower at 1 S'C compared to zoe of global warming (high 

confidence). {3.4.3, 3.5.2] 

8.3.2 Approximately 4G/o {interquartile range 2-7%) of the global terrestrial !and area is projected to undergo a transformation 

of ecosystems from one type to another at 1°C of global warming, compared with 13% (interquartile range 8-20°/o) at zoe 

(medium confidence). This indicates that the area at risk is projected to be approximately 50% lower at 1.5°( compared to 

2'C (medium confidence). {3.4.3.1, 3.4.3.5} 

8.3.3 High-latitude tundra and boreal forests are particularly at risk of climate change-induced degradation and loss, with woody 

shrubs already encroaching into the tundra (high confidence) and this will proceed with further warming. limiting global 

warming to 1.5°( rather than 2°( is projected to prevent the thawing over centuries of a permafrost area in the range of 

1.5 to 2.5 million km' (medium confidence). {3.3.2, 3.4.3, 3.5.5] 

8.4 limiting global warming to 1.5°C compared to 2°C is projected to reduce increases in ocean 

temperature as well as associated increases in ocean acidity and decreases in ocean oxygen levels 

(high confidence). Consequently, limiting global warming to 1.5'C is projected to reduce risks 

to marine biodiversity. fisheries. and ecosystems. and their functions and services to humans. 

as illustrated by recent changes to Arctic sea ice and warm~water coral reef ecosystems (high 

confidence). {3.3, 3.4, 3.5, Box 3.4, Box 3.5) 

8.4.1 There is high confidence that the probability of a sea ice-free Arctic Ocean during summer is substantially lower at global 

warming of 1.5°( when compared to 2°C. With 1.5°( of global warming, one sea ice-free Arctic summer is projected per 

century, This likelihood is increased to at !east one per decade with 2°e global warming. Effects of a temperature overshoot 

are reversible for Arctic sea ice cover on decadal time scales (high confidence). {3.3.8, 3.4.4.7} 

B.4.2 Global warming of 1.5°( is projected to shift the ranges of many marine species to higher latitudes as well as increase the 

amount of damage to many ecosystems. It is also expected to drive the loss of coastal resources and reduce the productivity of 

fisheries and aquaculture (especially at low latitudes}. The risks of climate-induced impacts are projected to be higher at zoe than those at global warming of 1.5°( (high confidence). Coral reefs, for example, are projected to decline by a further 7Q-90% 

at 1.5°( (high confidence) with larger losses (>99%) at 2°( (very high confidence). The risk of irreversible loss of many marine 

and coastal ecosystems increases with global warming, especially at 2oc or rnore (high confidence). {3.4.4, Box 3.4} 

9 Consistent w1th earl~r studies, illustrative numb€rs were adopted from one recent meta·study 
99 

Summary for Policymakers 

8.4.3 The level of ocean acidification due to increasing C02 concentrations associated with global warming of 1.5°( is projected to 

amplify the adverse effects of warming, and even further at 2°(, impacting the growth, development, calcification, survival, 

and thus abundance of a broad range of species, for example, from algae to fish {high confidence). {3.3.1 0, 3.4.4} 

8.4.4 Impacts of climate change in the ocean are increasing risks to fisheries and aquaculture via impacts on the physiology, 

survivorship, habitat, reproduction, disease incidence, and risk of invasive species {medium confidence) but are projected to be 

less at 1.503( of global warming than at 2°C One global fishery model, for example, projected a decrease in global annual catch 

for marine fisheries of about 1.5 million tonnes for 1.5°C of global warming compared to a loss of more than 3 million tonnes 

for 2"C of global wanning {medium confidence). {3.4.4, Box 3.4} 

B.S Climate-related risks to health, livelihoods, food security, water supply, human security, and 

economic growth are projected to increase with global warming of 1.SOC and increase further with 

2"C. (Figure SPM.2) {3.4, 3.5, 5.2, Box 3.2, Box 3.3, Box 3.5, Box 3.6, Cross-Chapter Box 6 in Chapter 

3, Cross-Chapter Box 9 in Chapter 4, Cross-Chapter Box 12 in Chapter 5, 5.2} 

8..5.1 Populations at disproportionately higher risk of adverse consequences with global warming of 1.5°C and beyond include 

disadvantaged and vulnerable populations, some indigenous peoples, and local communities dependent on agricultural or 

coastal livelihoods (high confidence). Regions at disproportionately higher risk include Arctic ecosystems, dryland regions, 

small island developing states, and least Developed Countries (high confidence). Poverty and disadvantage are expected 

to increase in some populations as global warming increases; limiting global warming to 1.5°(, compared with 2°(, could 

reduce the number of people both exposed to climate-related risks and susceptible to poverty by up to several hundred 

million by 2050 (medium confidence). (3.4.1 0, 3.4.11, Box 3.5, Cross-Chapter Box 6 in Chapter 3, Cross-Chapter Box 9 in 

Chapter 4, Cross-Chapter Box 12 in Chapter 5, 4.2.2.2, 5.2.1, 5.2.2, 5.2.3, 5.6.3} 

8.5.2 Any increase in global warming is projected to affect human health, with primarily negative consequences (high confidence). 

lower risks are projected at 1.5°( than at 2°( for heat-related morbidity and mortality (vel}' high confidence) and for 

ozone-related mortality if emissions needed for ozone formation remain high (high confidence). Urban heat islands often 

amplify the impacts of heatwaves in cities (high confidence). Risks from some vector-borne diseases, such as malaria and 

dengue fever, are projected to increase with warming from 1 .5°( to 2°(, including potential shifts in their geographic range 

(high confidence). {3.4.7, 3.4.8, 3.5.5.8} 

8.5.3 limiting warming to 1.5°C compared with zoe is projected to result in smaller net reductions in yields of maize, rice, wheat, 

and potentially other cereal crops, particularly in sub-Saharan Africa, Southeast Asia, and Central and South America, and 

in the CO[dependent nutritional quality of rice and wheat {high confidence). Reductions in projected food availability are 

larger at 2°( than at 1.5°( of global warming in the Sahel, southern Africa, the Mediterranean, central Europe, and the 

Amazon (medium confidence). Livestock are projected to be adversely affected with rising temperatures, depending on the 

extent of changes in feed quality, spread of diseases, and water resource availability (high confidence). {3.4.6, 3.5.4, 3.5.5, 

Box 3.1, Cross-Chapter Box 6 in Chapter 3, Cross-Chapter Box 9 in Chapter 4} 

B.5.4 Depending on future socio-economic conditions, limiting global warming to 1.5°( compared to 2°( may reduce the 

proportion of the world population exposed to a climate change-induced increase in water stress by up to 50%, although 

there is considerable variability between regions (medium confidence). Many small island developing states could 

experience !ower water stress as a result of projected changes in aridity when global warming is limited to 1.5°C, as 

compared to 2"C {medium confidence). {3.3.5, 3.4.2, 3.4.8, 3.5.5, Box 3.2, Box 3.5, Cross-Chapter Box 9 in Chapter 4} 

8.5.5 Risks to global aggregated economic growth due to climate change impacts are projected to be lower at 1.5°( than at 

zoe by the end of this century10 (medium confidence). This excludes the costs of mitigation, adaptation investments and 

the benefits of adaptation. Countries in the tropics and Southern Hemisphere subtropics are projected to experience the 

largest impacts on economic growth due to climate change should global warming increase from 1.5°( to 2°( (medium 

confidence). {3.5.2, 3.5.3} 

I 

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100 

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Summary for Policymakers 

12 

8.5.6 Exposure to multiple and compound climate-related risks increases between 1.5°( and 2°( of global warming, with greater 

proportions of people both so exposed and susceptible to poverty in Africa and Asia {high confidence). For global warming 

from 1 .5°( to 2°(, risks across energy, food, and water sectors could overlap spatially and temporally, creating new and 

exacerbating current hazards, exposures, and vulnerabilities that could affect increasing numbers of people and regions 

(medium confidence). {Box 3.5, 3.3.1, 3.4.5.3, 3.4.5.6, 3.4.11, 3.5.4.9) 

8.5.7 There are multiple lines of evidence that since ARS the assessed levels of risk increased for four of the five Reasons for 

Concern (RFCs) for global warming to 2"C (high confidence). The risk transitions by degrees of global warming are now: 

from high to very high risk between 1.SOC and 2"C for RFC1 (Unique and threatened systems) (high confidence); from 

moderate to high risk between 1 °( and 1 .5°( for RFC2 (Extreme weather events) (medium confidence); from moderate to 

high risk between 1.5°( and 2°( for RFC3 (Distribution of impacts) (high confidence}; from moderate to high risk between 

1.5°( and 2.5°( for RFC4 (Global aggregate impacts) (medium confidence); and from moderate to high risk between 1°C 

and 2.5'C for RFC5 (large-scale singular events) (medium confidence). (Figure SPM.2) {3.4. 13; 3.5, 3.5.2) 

8.6 Most adaptation needs will be lower for global warming of 1.5'C compared to 2'C (high confidence). 

There are a wide range of adaptation options that can reduce the risks of climate change (high 

confidence). There are limits to adaptation and adaptive capacity for some human and natural 

systems at global warming of 1.5'C, with associated losses (medium confidence), The number and 

availability of adaptation options vary by sector (medium confidence). {Table 3.5, 4.3, 4.5, CrossChapter Box 9 in Chapter 4, Cross-Chapter Box 12 in Chapter 5} 

8.6.1 A wide range of adaptation options are available to reduce the risks to natural and managed ecosystems {e.g., ecosystembased adaptation, ecosystem restoration and avoided degradation and deforestation, biodiversity management, 

sustainable aquaculture, and local knowledge and indigenous knowledge), the risks of sea level rise (e.g., coastal defence 

and hardening), and the risks to health, livelihoods, food, water; and economic growth, especially in rural landscapes 

(e.g., efficient irrigation, social safety nets, disaster risk management risk spreading and sharing, and community~ 

based adaptation) and urban areas (e.g., green infrastructure, sustainable land use and planning, and sustainable water 

management) (medium confidence). {4.3.t, 4.3.2, 4.3.3, 4.3.5, 4.5.3, 4.5.4, 5.3.2, Box 4.2, Box 4.3, Box 4.6, Cross-Chapter 

Box 9 in Chapter 4). 

6.6.2 Adaptation is expected to be more challenging for ecosystems, food and health systems at 2'C of global warming than for 

1 S)C (medium confidence}. Some vulnerable regions, including small islands and least Developed Countries, are projected 

to experience high multiple interrelated climate risks even at global warming of 1.5°( (high confidence), {3.3.1, 3.4.5, 

Box 3.5, Table 3.5, Cross-Chapter Box 9 in Chapter 4, 5.6, Cross-Chapter Box 12 in Chapter 5, Box 5.3) 

8.6.3 limits to adaptive capacity exist at 1 .soc of global warming, become more pronounced at higher levels of warming and 

vary by sector, with site-specific implications for vulnerable regions, ecosystems and human health (medium confidence}. 

{Cross-Chapter Box 12 in Chapter 5, Box 3.5, Table 3.5) 
101 

Summary for Policymakers 

How the level of global warming affects impacts and/or risks associated with 

the Reasons for Concern (RFCs) and selected natural, managed and human 

systems 

Five Reasons For Concern (RFCs) illustrate the impacts and risks of 

different levels of global warming for people, economies and ecosystems 

across sectors and regions. 

Impacts and risks associated with the Reasons for Concern (RFCs) 

Impacts and risks for selected natural, managed and human systems 

dimate,re!ated hazards, 

combined with limited 

White indicates that no 

change. 

I 
102 

I 

Summary for Policymakers 

14 

C. Emission Pathways and System Transitions Consistent with 1.5°( 

Global Warming 

C.1 In model pathways with no or limited overshoot of 1.5°C. global net anthropogenic C02 emissions 

decline by about 45% from 2010 levels by 2030 (4()..60% interquartile range), reaching net zero 

around 2050 (2045-2055 interquartile range). For limiting global warming to below 2•c" C02 

emissions are projected to decline by about 25% by 2030 in most pathways (10-30% interquartile 

range) and reach net zero around 2070 (2065-2080 interquartile range). Non-co, emissions in 

pathways that limit global warming to 1.SOC show deep reductions that are similar to those in 

pathways limiting warming to 2•c. (high confidence) (Figure SPM.3a) {2.1. 2.3. Table 2.4) 

C.1.1 C02 emissions reductions that limit global warming to 1.5°( with no or limited overshoot can involve different portfolios of 

mitigation measures, striking different balances between lowering energy and resource intensity, rate of decarbonization, 

and the reliance on carbon dioxide removal. Different portfolios face different implementation challenges and potential 

synergies and trade-offs with sustainable development. (high confidence) (Figure SPM.3b) {2.3.2, 2.3.4, 2.4, 2.5.3} 

C.1.2 Modelled pathways that limit global warming to 1.5°( with no or limited overshoot involve deep reductions in emissions 

of methane and black carbon (35% or more of both by 2050 relative to 2010). These pathways also reduce most of the 

cooling aerosols, which partially offsets mitigation effects for two to three decades. Non-C02 emissions12 can be reduced 

as a result of broad mitigation measures in the energy sector. In addition, targeted non-C02 mitigation measures can 

reduce nitrous oxide and methane from agriculture, methane from the waste sector, some sources of black carbon, and 

hydrofluorocarbons. High bioenergy demand can increase emissions of nitrous oxide in some 1.5°C pathways, highlighting 

the importance of appropriate management approaches. Improved air quality resulting from projected reductions in many 

non-C02 emissions provide direct and immediate population health benefits in aii1.5°C model pathways. (high confidence) 

(Figure SPM.3a) {2.2.1, 2.3.3, 2.4.4, 2.5.3, 4.3.6, 5.4.2) 

C.1.3 limiting global warming requires limiting the total cumulative global anthropogenic emissions of C02 since the preindustria! period, that is, staying within a total carbon budget (high confidence). 13 By the end of 2017, anthropogenic (01 

emissions since the pre-industrial period are estimated to have reduced the total carbon budget for 1.5°( by approximately 

2200 ± 320 GtC02 (medium confidence). The associated remaining budget is being depleted by current emissions of 

42 ± 3 GtC02 per year {high confidence}. The choice of the measure of global temperature affects the estimated remaining 

carbon budget Using global mean surface air temperature, as in ARS, gives an estimate of the remaining carbon budget of 

580 GtC02 for a 50% probability of limiting warming to 1.5°(, and 420 GtC02 for a 66% probability (medium confidence). 14 

Alternatively, using GMST gives estimates of 770 and 570 GtC02, for 50% and 66% probabilities,15 respectively (medium 

confidence). Uncertainties in the size of these estimated remaining carbon budgets are substantial and depend on several 

factors. Uncertainties in the climate response to C02 and non-C01 emissions contribute ±400 GtC01 and the level of historic 

warming contributes ±250 GtC01 (medium confidence). Potential additional carbon release from future permafrost thawing 

and methane release from wetlands would reduce budgets by up to 100 GtC02 over the course of this century and more 

thereafter (medium confidence). In addition, the level of non-C02 mitigation in the future could alter the remaining carbon 

budget by 250 GtC02 in either direction (medium confidence}. {1.2.4, 2.2.2, 2.6.1, Table 2.2, Chapter 2 Supplementary 

Material} 

C.1.4 Solar radiation modification (SRM) measures are not included in any of the available assessed pathways. Although some 

SRM measures may be theoretically effective in reducing an overshoot, they face large uncertainties and knowledge gaps 

11 References to pa!hw~ys limiting global warming to 2"C are based on il 66% probability of staying below 2¢C 

13 There r:; a dear ~Clent·flc basis for il to~ai cd·bon budget com1>tent w:t!"l lPTiti~g global warmirg to 1.5"C However, neitner th1s total carto'l budget 'lor the fraction of this budget 

takenupbypaste'tlissionswereassessedmthisReport 

1 S These estimates use observed GMST to 2006··7015 and estimate future temperature changes using near surface a1r temperatures 
103 

Summary for Policymakers 

Global emissions pathway characteristics 

General characteristics of the evolution of anthropogenic net emissions of C02, and total emissions of 

methane, black carbon, and nitrous oxide in model pathways that limit global warming to lSC with no or 

limited overshoot. Net emissions are defined as anthropogenic emissions reduced by anthropogenic 

removals. Reductions in net emissions can be achieved through different portfolios of mitigation measures 

illustrated in Figure SPM.3b. 

Global total net co, emissions 

BI!Hon tonnes of COjyr 

Non-CO, emissions relative to 2010 

Emissions of non··CO, forcers are a!so reduced 

Methane emissions 

Black carbon embsion:, 

Nitrous oxide emissions 

----------- PJthw~ys!imitinr,glob~!w~rmingto 1St with noorlimitt-d(wNshoot 

P~thw~yswithhigherovershoot 

peru:nti!e of sc0narios f'Jtflwny$\Hl1iti<lf:i(IOb~t WJrfl)ing bdflw )'( (No(>l,owll,Jbove) 

I 

15 
104 

I 

Summary for Policymakers 

16 

Characteristics of four illustrative model pathways 

Different mitigation strategies can achieve the net emissions reductions that would be required to follow a 

pathway that limits global warming to lSC with no or limited overshoot. All pathways use Carbon Dioxide 

Removal (CDR), but the amount varies across pathways, as do the relative contributions of Bioenergywith 

Carbon Capture and Storage (BECCS) and removals in the Agriculture, Forestry and Other Land Use (AFOLU) 

sector. This has implications for emissions and several other pathway characteristics. 

Breakdown of contributions to global net C01 emissions in four illustrative model pathways 

' fossil fuel and industry vi,; AFOLU BECCS 

!:li!!iontonn€'\CO,p!.'ryear(GtCO>.Iyr) 

Globalinrticators Pl P2 

llillio»tonne5CO,peryilar(GtCO,fy') 

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wHch >tKwtal as well a~ techllolog~ea\ 

dwelopmMt follows historic~ I 

iMltl'ms tmi<;~kms reductions ~re 

P3 P4 lntuquartHel'llnge 

PDthwoydoss/firotiMI 

CO,cmMiOnchorrgein2030(%re!to2MO} 

No arlimlled oV¢rshoat No Oflim}tedav~nhoot N"oorilll)lted over5hoQt, ; Hight'rovershoot Noarhmited ovetshbot 

,fn20~1)(%mlto20JO) 

lli/OSO{%rofto1010) 

F'no/(!nergydemand'"in2030f%mlto2010} 

in10SO{%rdio20l0) 

in10SOI%J 

l'rimoryenNgyfm"l coG!m 21130(-it n>lt~ lOW) 

inXl50('liiroJw20JO} 

fmm biomass JJl 1030 {% r~lto2010j 

in_JOSO(%roltoJOliJ} 

in)050~[Cfto)OlO} 

CamulatwertsvnH2100(Gt('(h) 

Agrku!tomlCIIfemi>sion$1n2a30{%re/1o2011J) 

JlgricJituraiN>OI'misskiriSFnZ030(%te/to1010) 

' 

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70 

(-93,.81) 

1-n,l) 

(-11,2;4 

(47,65) 

(€S,S6) 

(·'34,3) 

(,78,..'!1) 

{-JG,/1) 

{":5£,6} 

i44,102) 

{S:l,l9(l) 

(29,80) 

(123,261} 

(2.45,436) 

(5'16,1299) 

{3M,6G2} 

(-.'10,-H) 

{-11,3} 
105 

Summary for Policymakers 

C.2 Pathways limiting global warming to 1.SOC with no or limited overshoot would require rapid 

and far-reaching transitions in energy. land, urban and infrastructure (induding transport and 

buildings), and industrial systems (high confidence). These systems transitions are unprecedented 

in terms of scale, but not necessarily in terms of speed, and imply deep emissions reductions in all 

sectors, a wide portfolio of mitigation options and a significant upscaling of investments in those 

options (medium confidence). {2.3, 2.4, 2.5, 4.2, 4.3, 4.4, 4.5} 

C.2.1 Pathways that limit global warming to 1.5°( with no or limited overshoot show system changes that are more rapid and 

pronounced over the next tvvo decades than in 2°C pathways (high confidence). The rates of system changes associated 

with limiting global warming to 1.5°( with no or llmited overshoot have occurred in the past within specific sectors, 

technologies and spatial contexts, but there is no documented historic precedent for their scale (medium confidence). 

{2.3.3, 2.3.4, 2.4, 25, 4.2.1, 4.2.2, Cross-Chapter Box 11 in Chapter 4} 

C.2.2 In energy systl!ms, modelled global pathways (considered in the literature) limiting global warming to 1.5oc with no or 

limited overshoot {for more details see Figure SPM.3b) generally meet energy service demand with lower energy use, 

including through enhanced energy efficiency, and show faster electrification of energy end use compared to 2°( {high 

confidence). In 1.5°( pathways with no or limited overshoot, low-emission energy sources are projected to have a higher 

share, compared with 2°C pathways, particularly before 2050 (high confidence}. In 1.5°( pathways with no or limited 

overshoot, renewables are projected to supply 70-85°/o (1nterquartile range) of electricity in 2050 (high confidence). In 

electricity generation, shares of nuclear and fossil fuels with carbon dioxide capture and storage (CCS) are modelled to 

increase in most 1 .5°C pathways with no or limited overshoot In modelled 1.5°C pathways with limited or no overshoot, 

the use of CCS would allow the electricity generation share of gas to be approximately 8% (3-11% interquartile range) 

of global electricity in 2050, while the use of coal shows a steep reduction in all pathways and would be reduced to dose 

to 0% (0-2% interquartile range) of electricity (high confidence}. While acknowledging the challenges, and differences 

between the options and national circumstances, political, economic, soda! and technical feasibility of solar energy, wind 

energy and electricity storage technologies have substantially improved over the past few years (high confidence). These 

improvements signal a potential system transition in electricity generation. (Figure SPM.3b) {2.4.1, 2.4.2, Figure 2.1, Table 

2.6. Table 2.7, Cross-Chapter Box 6 in Chapter 3, 4.2.1, 4.3.1, 4.3.3, 4.5.2) 

C.2.3 C02 emissions from industry in pathways limiting global warming to 1.5''( with no or limited overshoot are projected to 

be about 65-90% (interquartile range) lower in 2050 relative to 2010, as compared to SQ-80% for global warming of 

2°( {medium confidence). Such reductions can be achieved through combinations of new and existing technologies and 

practices, including electrification, hydrogen, sustainable bio·based feedstocks, product substitution, and carbon capture, 

utilization and storage (CCUS). These options are technically proven at various scales but their large-scale deployment 

may be limited by economic, financial, human capacity and institutional constraints in specific contexts, and specific 

characteristics of large-scale industria! installations. In industry, emissions reductions by energy and process efficiency 

by themselves are insufficient for limiting warming to 1.5°( with no or limited overshoot (high confidence). {2.4.3, 4.2. 1, 

Table 4.1, Table 4.3, 4.3.3, 4.3.4, 4.5.2} 

C.2.4 The urban and infrastructure system transition consistent with limiting global warming to 1.5°( with no or limited overshoot 

would imply, for example, changes in land and urban planning practices, as well as deeper emissions reductions in transport 

and buildings compared to pathways that limit global warming below 2°( (medium confidence). Technical measures 

I 

17 
106 

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Summary for Policymakers 

18 

C2.5 

C2.6 

C.2.7 

and practices enabling deep emissions reductions include various energy efficiency options. In pathways limiting global 

warming to 1.5°( with no or limited overshoot, the electricity share of energy demand in buildings would be about 55-75% 

in 2050 compared to SQ-70% in 2050 for 2"( global warming (medium confidence). In the transport sector. the share of 

low-emission final energy would rise from less than 5% in 2020 to about 35-65% in 2050 compared to 25-45% for 2"'C 

of global warming {medium confidence). Economic, institutional and socio-cultural barriers may inhibit these urban and 

infrastructure system transitions, depending on national regional and local circumstances, capabilities and the availability 

of capital (high confidence). (2.3.4, 2.43, 4.2.1, Table 4.1, 433, 4.5.2} 

Transitions in global and regional land use are found in all pathways limiting global warming to 1 S'C with no or limited 

overshoot, but their scale depends on the pursued mitigation portfolio. Model pathways that limit global warming to 1.5°( 

with no or limited overshoot project a 4 million kmz reduction to a 2.5 million km2 increase of non-pasture agricultural land 

for food and feed crops and a 0.5-11 million km2 reduction of pasture land, to be converted into a 0-6 million km2 increase 

of agricultural land for energy crops and a 2 million km2 reduction to 9.5 million km2 increase in forests by 2050 relative 

to 2010 {medium confidence). 16 Land-use transitions of similar magnitude can be obse!Ved in modelled 2°( pathways 

(medium confidence). Such large transitions pose profound challenges for sustainable management of the various demands 

on land for human settlements, food, livestock feed, fibre, bioenergy, carbon storage, biodiversity and other ecosystem 

services (Mgh confidence). Mitigation options limiting the demand for land include sustainable intensification of land*use 

practices. ecosystem restoration and changes towards less resource*intensive diets (high confidence). The implementation 

of !and-based mitigation options would require overcoming socio-economic, institutional, technological, finandng and 

environmental barriers that differ across regions (high confidence). {2.4.4, Figure 2.24, 4.12, 4.3.7, 4.5.2, Cross-Chapter 

Box 7 in Chapter 3) 

Additional annual average energy-related investments for the period 2016 to 2050 in pathways limiting warming to 

1.5'-'C compared to pathways without new climate policies beyond those in place today are estimated to be around 830 

billion USD201 0 (range of 150 billion to 1700 billion USD201 0 across six mode!s17). This compares to total annual average 

energy supply investments in 1.5"( pathways of 1460 to 3510 billion USD2010 and total annual average energy demand 

investments of 640 to 910 billion U$02010 for the period 2016 to 2050. Total energy-related investments increase by 

about 12°/o (range of 3% to 24%) in 1.5"C pathways relative to 2"( pathways. Annual investments in low-carbon energy 

technologies and energy efficiency are upscaled by roughly a factor of six (range of factor of 4 to 10) by 2050 compared to 

2015 (medium confidence). {2.5.2, Box 4.8, Figure 2.27) 

Modelled pathways limiting global warming to 1.5°( with no or limited overshoot project a wide range of global average 

discounted marginal abatement costs over the 21st century. They are roughly 3-4 times higher than in pathways limiting 

global warming to below 2°( (high confidence). The economic literature distinguishes marginal abatement costs from total 

mitigation costs in the economy. The literature on total mitigation costs of 1.5°( mitigation pathways is limited and was 

not assessed in this Report. Knowledge gaps remain in the integrated assessment of the e<onomy-wide costs and benefits 

of mitigation in line with pathways limiting warming to 1.5'C. {2.5.2; 2.6; figure 2.26} 

Hi Tke projected !and,use changes presented are not deployed to their UpPer limits slmultane.ou~ly in a single pa!hway, 

17 tnduding tl'.m pathways limitmg warming to 1.s~c wtth oo or limit-M overshoo! and four pathwat'S WJ!Il higll«r overshoot 
107 

Summary for Policymakers 

C.3 All pathways that limit global warming to 1.5'C with limited or no overshoot project the use of 

carbon dioxide removal (CDR) on the order of 1D0-1000 GtCO, over the 21st century. CDR would 

be used to compensate for residual emissions and, in most cases.· achieve net negative emissions 

to return global warming to 1.S'C following a peak (high confidence). CDR deployment of several 

hundreds of GtCO, is subject to multiple feasibility and sustainability constraints (high confidence). 

Significant near-term emissions reductions and measures to lower energy and land demand can 

limit CDR deployment to a few hundred GtCO, without reliance on bioenergy with carbon capture 

and storage (BECCS) (high confidence). {2.3, 2.4, 3.6.2, 4.3, 5.4} 

C.3. 1 Existing and potential CDR measures Include afforestation and reforestation, land restoration and soil carbon sequestration, 

BECCS, direct air carbon capture and storage (DACCS), enhanced weathering and ocean alkalinization. These differ widely 

in terms of maturity, potentials, costs. risks, co-benefits and trade-offs (high confidence). To date, only a few published 

pathways include CDR measures other than afforestation and BECCS. {2.3.4, 3.6.2, 4.3.2, 4.3.7) 

C.3.2 In pathways limiting global warming to 1.5'( with limited or no overshoot, BECCS deployment is projected to range from 

0-1, 0-8, and 0-16 GtCO, yr·1 in 2030, 2050, and 2100, respectively, while agriculture, forestry and land-use (AFOlU) 

related CDR measures are projected to remove D-5, 1-11, and 1-5 GtC02 yr1 in these years (medium confidence). The 

upper end of these deployment ranges by mid-century exceeds the BECCS potential of up to 5 GtC02 yr1 and afforestation 

potential of up to 3.6 GtC02 yr1 assessed based on recent literature (medium confidence). Some pathways avoid BECCS 

deployment completely through demand-side measures and greater reliance on AFOlU-related CDR measures (medium 

confidence). The use of bioenergy can be as high or even higher when BECCS is excluded compared to when it is included 

due to its potential for replacing fossil fuels across sectors (high confidence). (Figure SPM.3b) {2.3.3, 2.3.4, 2.4.2, 3.6.2, 

4.3.1, 4.2.3, 4.3.2, 4.3. 7, 4.4.3, Table 2.4) 

C.3.3 Pathways that overshoot 1.5"C of global warming rely on CDR exceeding residual C02 emissions later in the century to 

return to below 1 S'C by 2100, with larger overshoots requiring greater amounts of CDR (Figure SPM.3b) {high confidence}. 

limitations on the speed, scale. and societal acceptability of CDR deployment hence determine the ability to return global 

warming to below 1 .5°( following an overshoot. Carbon cycle and climate system understanding is still limited about the 

effectiveness of net negative emissions to reduce temperatures after they peak {high confidence). {2.2, 2.3.4, 2.35, 2.6, 

4.3.7, 4.5.2. Table 4.11) 

C.3.4 Most current and potential CDR measures could have significant impacts on land, energy, water or nutrients if deployed 

at large scale (high confidence). Afforestation and bioenergy may compete with other land uses and may have significant 

impacts on agricultural and food systems, biodiversity, and other ecosystem functions and services (high confidence). 

Effective governance is needed to limit such trade-offs and ensure permanence of carbon removal in terrestrial, geological 

and ocean reservoirs (high confidence). Feasibility and sustainability of CDR use could be enhanced by a portfolio of options 

deployed at substantial, but lesser scales, rather than a single option at very large scale (high confidence). (Figure SPM.3b) 

(2.3.4, 2.4.4, 2.5.3. 2.6. 3.6.2, 4.3.2, 4.3.7, 4.5.2, 5.4.1, 5.4.2; Cross-Chapter Boxes 7 and 8 in Chapter 3, Table 4.11, Table 

5.3, Figure 5.3) 

C3.5 Some AFOlU-related CDR measures such as restoration of natural ecosystems and soil carbon sequestration could provide 

co-benefits such as improved biodiversity, soil quality, and local food sewrity. If deployed at large scale, they would 

require governance systems enabling sustainable land management to conserve and protect land carbon stocks and other 

ecosystem functions and services (medium confidence). {Figure SPM.4) {2.3.3, 2.3.4, 2.4.2, 2.4.4, 3.6.2, 5.4.1, Cross-Chapter 

Boxes 3 in Chapter 1 and 7 in Chapter 3, 4.3.2, 4.3.7, 4.4.1, 4.5.2. Table 2.4) 

I 

19 
108 

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Summary for Policymakers 

20 

D. Strengthening the Global Response in the Context of Sustainable 

Development and Efforts to Eradicate Poverty 

0.1 Estimates of the global emissions outcome of current nationally stated mitigation ambitions as 

submitted under the Paris Agreement would lead to global greenhouse gas emissions" in 2030 

of 52-58 GtC02eq yr' (medium confidence). Pathways reflecting these ambitions would not limit 

global warming to 1.5'C, even if supplemented by very challenging increases in the scale and 

ambition of emissions reductions after 2030 (high confidence). Avoiding overshoot and reliance 

on future large .. cale deployment of carbon dioxide removal (CDR) can only be achieved if global 

CO, emissions start to decline well before 2030 (high confidence). {1.2, 2.3, 3.3, 3.4, 4.2, 4.4, CrossChapter Box 11 in Chapter 4} 

0.1.1 Pathways that limit gfobal warming to 1.5°( with no or limited overshoot show clear emission reductions by 2030 (high 

confidence}. All but one show a decline in global greenhouse gas emissions to below 35 GtC02eq yr1 in 2030, and half of 

available pathways fall within the 25-30 GtCO,eq yr' range (interquartile range), a 4Q-50% reduction from 2010 levels 

(high confidence}. Pathways reflecting current nationally stated mitigation ambition until 2030 are broadly consistent 

with cost-effective pathways that result in a global warming of about 3"( by 2100, with warming continuing afterwards 

(medium confidence). {2.3.3, 2.3.5, Cross-Chapter Box 11 in Chapter 4, 5.5.3.2} 

0. 1.2 Overshoot trajectories result in higher impacts and associated challenges compared to pathways that limit global warming 

to 1.5"C with no or limited overshoot (high confidence), Reversing warming after an overshoot of 0.2"C or larger during 

this century would require upscaling and deployment of CDR at rates and volumes that might not be achievable given 

considerable implementation challenges (medium confidence). {1.3.3, 2.3.4, 2.3.5, 2.5.1, 3.3, 4.3.7, Cross-Chapter Box 8 in 

Chapter 3, Cross-Chapter Box 11 in Chapter 4} 

0.1.3 The lower the emissions in 2030, the lower the challenge in limiting global warming to 1.5"C after 2030 with no or limited 

overshoot (/Jigh confidence). The challenges from delayed actions to reduce greenhouse gas emissions include the risk of 

cost escalation, lock~in in carbonwemitting infrastructure. stranded assets, and reduced flexibility in future response options 

in the medium to long term (high confidence}, These may increase uneven distributional impacts between countries at 

different stages of development (medium confidence). {2.3.5, 4.4.5, 5.4.2) 

0.2 The avoided climate change impacts on sustainable development, eradication of poverty and reducing 

inequalities would be greater if global warming were limited to 1.5'C rather than 2'(, if mitigation 

and adaptation synergies are maximized while trade-offs are minimized (high confidence). {1.1, 1.4, 

2.5, 3.3, 3.4. 5.2, Table 5.1} 

0.2.1 Climate change impacts and responses are closely linked to sustainable development which balances social well~being, 

economic prosperity and environmental protection. The United Nations Sustainable Development Goals (SDGs), adopted in 

2015, provide an established framework for assessing the llnks between global warming of 1 .5"( or 2°C and development 

goals that include poverty eradication, reducing inequalities, and climate action. (high confidence) {Cross-Chapter Box 4 in 

Chapter 1, 1.4, 5.1} 

0.2.2 The consideration of ethics and equity can help address the uneven distribution of adverse impacts associated with 

1 .soc and higher levels of global warming, as well as those from mitigation and adaptation, particularly for poor and 

disadvantaged populations, in all societies (high confidence). {1.1.1, 1.1.2, 1.4.3, 2.5.3, 3.4.10, 5.1, 5.2, 5.3. 5.4, CrossChapter Box 4 in Chapter 1, Cross-Chapter Boxes 6 and 8 in Chapter 3, and Cross-Chapter Box 12 in Chapter 5} 

0.2.3 Mitigation and adaptation consistent with limiting global warming to 1.5°C are underpinned by enabling conditions, assessed 

in this Report across the geophysical, environmental-ecological, technological, economic, socio-cultural and institutional 

18 GHG emissions have been aggr('gated with 100·year GWP values as introduc('d in the IPCC Se<ond Assessmtmt Report. 
109 

Summary for Policymakers 

dimensions of feasibility. Strengthened multilevel governance, institutional capacity, policy instruments, technological 

innovation and transfer and mobilization of finance, and changes in human behaviour and lifestyles are enabling conditions 

that enhance the feasibility of mitigation and adaptation options for 1.5"C~consistent systems transitions. (high confidence} 

{1.4, Cross-Chapter Box 3 in Chapter 1, 2.5.1, 4.4, 4.5, 5.6) 

0.3 Adaptation options specific to national contexts, if carefully selected together with enabling 

conditions, will have benefits for sustainable development and poverty reduction with global 

warming of 1SC, although trade·offs are possible (high confidence). {1.<1, 4.3, 4.5) 

D.3.1 Adaptation options that reduce the vulnerability of human and natural systems have many synergies with sustainable 

development, if well managed, such as ensuring food and water security, reducing disaster risks. improving health 

conditions, maintaining ecosystem services and reducing poverty and inequality (high confidence}. lncreasing investment 

in physical and social infrastructure is a key enabling condition to enhance the resilience and the adaptive capacities 

of societies. These benefits can occur in most regions with adaptation to 1.5°( of global warming (high confidence}. 

{1.4.3, 4.2.2, 4.3.1' 4.3.2, 4.3.3, 4.3.5, 4.4.1' 4.4.3, 4.5.3, 5.3.1, 5.3.2) 

0.3.2 Adaptation to 1.5°( global warming can also result in trade--offs or maladaptations with adverse impacts for sustainable 

development For example, if poorly designed or implemented, adaptation projects in a range of sectors can increase 

greenhouse gas emissions and water use, increase gender and social inequality, undermine health conditions, and encroach 

on natural ecosystems (high confidence). These trade~offs can be reduced by adaptations that include attention to poverty 

and sustainable development (high confidence). {4.3.2. 4.3.3, 4.5.4, 5.3.2; Cross-Chapter Boxes 6 and 7 in Chapter 3) 

0.3.3 A mix of adaptation and mitigation options to limit global warming to 1 ,5°(, implemented in a participatory and integrated 

manner. can enable rapid, systemic transitions in urban and rural areas (Mgh confidence). These are most effective when 

aligned with economic and sustainable development, and when local and regional governments and decision makers are 

supported by national governments {medium confidence). {4.3.2, 4.3.3, 4.4.1, 4.4.2) 

0.3.4 Adaptation options that also mitigate emissions can provide synergies and cost savings in most sectors and system 

transitions, such as when land management reduces emissions and disaster risk, or when low~carhon buildings are also 

designed for efficient cooling. Trade~offs between mitigation and adaptation, when limiting global warming to 1 .5°(, 

such as when bioenergy crops, reforestation or afforestation encroach on land needed for agricultural adaptation, can 

undermine food security, livelihoods, ecosystem functions and services and other aspects of sustainable development. (high 

confidence) {3.4.3, 4.3.2, 4.3.4, 4.4.1, 4.5.2, 4.5.3, 4.5.4) 

0.4 Mitigation options consistent with 1.5°C pathways are associated with multiple synergies and trade~ 

offs across the Sustainable Development Goals (SDGs). While the total number of possible synergies 

exceeds the number of trade-offs, their net effect will depend on the pace and magnitude of changes, 

the composition of the mitigation portfolio and the management of the transition. (high confidence) 

(Figure SPM.4) {2.5, 4.5, 5.4) 

0.4.1 1.5"C pathways have robust synergies particularly for the SDGs 3 (health), 7 (clean energy), 11 (cities and communities), 12 

(responsible consumption and production) and 14 (oceans) (very high confidence). Some 1.5°( pathways show potential 

trade-offs with mitigation for SDGs 1 (poverty), 2 (hunger), 6 {water) and 7 (energy access), if not managed carefully (high 

confidence). (figure SPM.4) {5.4.2; figure 5.4, Cross-Chapter Boxes 7 and 8 in Chapter 3) 

0.4.2 1.5°( pathways that include low energy demand (e.g., see P1 in Figure SPM.3a and SPM.3b), !ow material consumption, 

and low GHG-intensive food consumption have the most pronounced synergies and the lowest number of trade-offs with 

respect to sustainable development and the SDGs (high confidence). Such pathways would reduce dependence on CDR. In 

modelled pathways, sustainable development, eradicating poverty and reducing inequality can support limiting warming to 

1.5"C {high confidence). (Figure SPM.3b, figure SPM.4) {2.4.3, 2.5.1, 2.5.3, Figure 2.4, figure 2.28, 5.4.1, 5.4.2, Figure 5.4) 

I 

21 
110 

Summary for Policymakers 

22 

Indicative linkages between mitigation options and sustainable 

development using SDGs (The linkages do not show costs and benefits) 

Mitigation options deployed ln each sector can be associated with potential 

negative effects (trade-offs) with the Sustainable Development Goals 

potential is realized will depend on the selected portfolio of mitigation options, 

and local circumstances and context. Particularly in the energy-demand the 

larger than for trade-offs. The bars group individually assessed options by 

account the relative strength of the assessed mitigation-SDG connections. 

Length shows strength of connection Shades show level of confidence 

I 

I 

I 

I 

I II ;-,~1 ' 

••• ' u \>1 

.J 

I ••• • 

>"1 

\~, I 
111 

Summary for Policymakers 

0.4.3 1.5°( and 2°( modelled pathways often rely on the deployment of large·scale !and·re!ated measures like afforestation 

and bioenergy supply, which, if poorly managed, can compete with food production and hence raise food security concems 

(high confidence). The impacts of carbon dioxide removal {CDR) options on SDGs depend on the type of options and the 

scale of deployment (high confidence).lf poorly implemented, CDR options such as BECCS and AfOlU options would lead 

to trade·offs. ContexHelevant design and implementation requires considering people's needs, biodiversity, and other 

sustainable development dimensions (very high confidence}. (Figure SPM.4) {5.4.1.3, Cross·Chapter Box 7 in Chapter 3} 

0.4.4 Mitigation consistent with 1.5°( pathways creates risks for sustainable development in regions with high dependency on 

fossil fuels for revenue and employment generation (high confidence). Policies that promote diversification of the economy 

and the energy sector can address the associated challenges (high confidence). {5.4.1.2, Box 5.2} 

0.4.5 Redistributive policies across sectors and populations that shield the poor and vulnerable can resolve trade-offs for a range 

of SDGs, particularly hunger, poverty and energy access. Investment needs for such complementary policies are only a small 

fraction of the overall mitigation investments in 1 .5°C pathways. (high confidence) {2.4.3, 5.4.2, Figure 5.5} 

0.5 Limiting the risks from global warming of 1.SOC in the context of sustainable development and 

poverty eradication implies system transitions that can be enabled by an increase of adaptation 

and mitigation investments. policy instruments. the acceleration of technological innovation and 

behaviour changes (high confidence). {2.3, 2.4, 2.5, 3.2, 4.2, 4.4, 4.5, 5.2, 5.5, 5.6} 

D.5.1 Directing finance towards investment in infrastructure for mitigation and adaptation could provide additional resources. 

This could involve the mobilization of private funds by institutional investors, asset managers and development or 

investment banks, as we!! as the provision of public funds. Government policies that lower the risk of low-emission and 

adaptation investments can facilitate the mobilization of private funds and enhance the effectiveness of other public 

policies. Studies indicate a number of challenges, including access to finance and mobilization of funds. (high confidence) 

{2.5.1' 2.5.2, 4.4.5} 

D.5.2 Adaptation finance consistent with global warming of 1.5°C is difficult to quantify and compare with 2°C. Knowledge 

gaps include insufficient data to calculate specific climate resilience·enhancing investments from the provision of currently 

underinvested basic infrastructure. Estimates of the costs of adaptation might be lower at global warming of 1.5°( than for 

2°C.Adaptation needs have typically been supported by public sector sources such as national and subnationalgovernment 

budgets, and in developing countries together with support from development assistance, multilateral development banks, 

and United Nations Framework Convention on Climate Change channels (medium confidence). More recently there is a 

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Summary for Policymakers 

24 

growing understanding of the scale and increase in non-governmental organizations and private funding in some regions 

(medium confidence). Barriers include the scale of adaptation financing, limited capacity and access to adaptation finance 

(medium confidence). {4.4.5, 4.6) 

0.5.3 Global model pathways limiting global warming to 1.5°( are projected to involve the annual average investment needs 

in the energy system of around 2.4 trillion USD2010 between 2016 and 2035, representing about 2.5% of the world GDP 

(medium confidence). {4.4.5, Box 4.8) 

0.5.4 Policy tools can help mobilize incremental resources, including through shifting global investments and savings and 

through market and non-market based instruments as well as accompanying measures to secure the equity of the 

transition, acknowledging the challenges related with implementation, including those of energy costs, depreciation of 

assets and impacts on international competition, and utilizing the opportunities to maximize co·benefits (high confidence). 

{1.3.3, 2.3.4, 2.3.5, 2.5.1, 2.5.2, Cross-Chapter Box 8 in Chapter 3, Cross-Chapter Box 11 in Chapter 4, 4.4.5, 5.5.2) 

D.5.5 The systems transitions consistent with adapting to and limiting global warming to 1.5°( indude the widespread adoption 

of new and possibly disruptive technologies and practices and enhanced climate--driven innovation. These imply enhanced 

technological innovation capabilities, including in industry and finance. Both national innovation policies and international 

cooperation can contribute to the development, commercialization and widespread adoption of mitigation and adaptation 

technologies. Innovation policies may be more effective when they combine public support for research and development 

with policy mixes that provide incentives for technology diffusion. (high confidence) {4.4.4, 4.4.5}. 

D.5.6 Education, information, and community approaches, including those that are informed by indigenous knowledge and local 

knowledge, can accelerate the wide-scale behaviour changes consistent with adapting to and limiting global warming to 

1.5°C. These approaches are more effective when combined wlth other policies and tailored to the motivations, capabilities 

and resources of specific actors and contexts (high confidence). Public acceptability can enable or inhibit the implementation 

of policies and measures to limit global warming to 1.5°( and to adapt to the consequences. Public acceptability depends 

on the individual's evaluation of expected policy consequences, the perceived fairness of the distribution of these 

consequences, and perceived fairness of decision procedures (high confidence). {1.1, 15, 4.3.5, 4.4.1, 4.4.3, Box 4.3, 5.5.3, 

5.6.5) 

0.6 Sustainable development supports, and often enables, the fundamental societal and systems 

transitions and transformations that help limit global warming to 1 .SOC. Such changes facilitate the 

pursuit of climate-resilient development pathways that achieve ambitious mitigation and adaptation 

in conjunction with poverty eradication and efforts to reduce inequalities (high confidence), {Box 1.1, 

1.4.3, Figure 5.1, 5.5.3, Box 5.3} 

D.6.1 Social justice and equity are core aspects of climate-resilient development pathways that aim to limit global warming to 

1.5°( as they address challenges and inevitable trade-offs, widen opportunities, and ensure that options, visions, and values 

are deliberated, between and within countries and communities, without making the poor and disadvantaged worse off 

(high confidence). {5.5.2, 5.5.3, Box 5.3, Figure 5.1, Figure 5.6, Cross-Chapter Boxes 12 and 13 in Chapter 5) 

0.6.2 The potential for climate-resilient development pathways differs between and within regions and nations, due to different 

development contexts and systemic vulnerabilities (vefY high confidence). Efforts along such pathways to date have been 

limited (medium confidence) and enhanced efforts would involve strengthened and timely action from all countries and 

non-state actors (high confidence). {5.5.1, 5.5.3, figure 5.1) 

0.6.3 Pathways that are consistent with sustainable development show fewer mitigation and adaptation challenges and are 

associated with !ower mitigation costs. The large majority of modelling studies could not construct pathways characterized 

by lack of international cooperation, inequality and poverty that were able to limit global warming to 1.5°C (high 

confidence) {2.3.1, 2.5.1, 2.5.3, 5.5.2) 
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Summary for Policymakers 

0.7 Strengthening the capacities for climate action of national and sub~national authorities. civil society, 

the private sector, indigenous peoples and local communities can support the implementation of 

ambitious actions implied by limiting global warming to 1.SOC (high confidence). International 

cooperation can provide an enabling environment for this to be achieved in all countries and for all 

people, in the context of sustainable development. International cooperation is a critical enabler for 

developing countries and vulnerable regions (high confidence). {1.4, 2.3, 2.5, 4.2, 4.4, 4.5, 5.3, 5.4, 5.5, 

5.6, 5, Box 4.1, Box 4.2, Box 4.7, Box 5.3, Cross-Chapter Box 9 in Chapter 4, Cross-Chapter Box 13 in 

Chapter 5} 

D. 7,1 Partnerships involving non-state public and private actors, institutional investors, the banking system, civil society and 

scientific institutions would facilitate a{tions and responses consistent with limiting global warming to 1ST (very high 

confidence). {1.4, 4.4.1, 4.2.2, 4.4.3, 4.4.5, 4.5.3, 5.4.1, 5.6.2, Box 5.3}. 

D. 7.2 Cooperation on strengthened accountable multilevel governance that includes non-state actors such as industry, civil 

society and scientific institutions, coordinated sectoral and cross~sectoral policies at various governance levels, gender· 

sensitive policies, finance including innovative financing, and cooperation on technology development and transfer can 

ensure participation, transparency, capacity building and learning among different players (high confidence). {2.5.1, 2.5.2, 

4.2.2, 4.4.1, 4.4.2, 4.4.3, 4.4.4, 4.4.5, 4.5.3, Cross-Chapter Box 9 in Chapter 4, 5.3.1, 5.5.3, Cross-Chapter Box 13 in Chapter 

5, 5.6.1' 5.6.3} 

0.7.3 International cooperation is a critical enabler for developing countries and vulnerable regions to strengthen their action for 

the implementation of 1.5"C·consistent climate responses, including through enhancing access to finance and technology 

and enhancing domestic capacities, taking into account national and local circumstances and needs (high confidence). 

{2.3.1, 2.5.1, 4.4.1, 4.4.2, 4.4.4, 4.4.5, 5.4.1 5.5.3, 5.6.1, Box 4.1, Box 4.2, Box 4.7}. 

0.7.4 Collective efforts at all levels, in ways that reflect different circumstances and capabilities, in the pursuit of limiting global 

warming to 1.5°(, taking into account equity as well as effectiveness, can facilitate strengthening the global response to 

climate change, achieving sustainable development and eradicating poverty (high confidence). {1.4.2, 2.3.1, 2.5.1, 2.5.2, 

2.5.3, 4.2.2, 4.4.1,4.4.2, 4.4.3, 4.4.4,4.4.5, 4.5.3, 5.3.1, 5.4.1, 5.5.3, 5.6.1, 5.6.2, 5.6.3} 

I 

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Summary for Policymakers 

26 

Box ~PM.t: Core Concep~s Central to. ttils.Specla! Report 

Pre-industrial: Tha muttl·ceptury peiiod prior ;o thennset.oflarge'scale 

·period 1851>-190015 used to approximate pr<H'nduslrlal <iMST.{1.2.1.2l 

Carbon dioxide reti\Oval (ctiR): Anthropogenic acti.iliti.S rem~vi~g COi from the atmosphm" and durably storing lt tn 

geologica\ terrestrial or ocean reservQirs, or in pr?'"'cts. It lnctudi\s existing and potentia! an!hyopogenic $~!fancem~nt of 

biological or geochef!Jlcal sinks and direct air capture and storage, but exctu.des natural co, uptake not dlrectfy caused by 

hu'mah activities. 

Total. carbon b~d~et: Estimated cumulative. net global M!hr\lpoge~ic co, emissions {rQm the precin<lustriafperiod 

to the tim~ !hat anthropogenic CO, emissions. reach neq.ro that would re!;uh, at some probability, in limttinli global 

warming to a ~iveil level, accciunti!lg for the itnpact<Jf other,anthf~pogenic eml$$ions. {2.2,2} 

Remaining carbon budget: Esti!Tla!edcumulatlve net global antl)!oJ)ogenic CO, emlss~on< fro.m a given ~tarl <late to !he 

time that anthropogenic ce, emissions flla<:h net zero t1'at wo.uld result, at some probability, inlimltin!) glObal warming 

to a given level, accounting for the impact of. other anthr0pogenic emls$ions. {2.1\.2} 

Temperature overshOot: The temporary ex<;eedance of a spedfted level of global warming. 

Climat<l-r~silient dtivetopn\entpa!hways (CROPs): Trajectories that strengthen sustalflilble d<>V<llopmentat mu!tlpl~ 

Scales ;md .efforts to .eraffitate pOVerty through eQUitable. societal ~nq systems transitfl>nS ~nd transfOfO)alions While 

mducing the threat of climate change through ambitious mitigatjon( :adaptation and climate resmente, 
115 

Chairwoman JOHNSON. Thank you very much. 

Now, the Chair recognizes Mr. Lucas. 

Mr. LUCAS. Thank you, Chairwoman. I appreciate that. 

As I said in my opening statement, I represent a rural district 

where weather trends and predictions are extremely important to 

the agricultural community. Dr. Majkut, what are some of the 

things that we’re doing well, and what are some of the things we 

could do better to increase preparedness for weather events and 

other effects associated with climate change? 

Dr. MAJKUT. Thank you for the question. I actually think we’re 

doing fairly well. You look at the National Climate Assessment, 

and it shows a real effort on the part of the scientific community 

to start understanding what the medium- and long-term effects of 

climate change are going to be for communities like your own. And 

just one of the things—and that activity should definitely continue. 

One of the things we might think about doing better in the 

Science Committee and the Science Committee generally can think 

about doing is getting decisionmakers information that’s relevant 

on the timescales over which they make decisions, right? So you 

mentioned you represent a farming community and you’re a farmer 

yourself. You understand that what you think about the weather 

is a question for the next few days and the stuff you’re going to 

do over the next few days. It’s not necessarily clear that a 30-year 

projection is a helpful thing for what you’re deciding to do this year 

or next year. But if you’re designing a water system or a 

stormwater system or something like that, something you want to 

have around for a long time, then you really do want to have information around what the next 30 or 50 or 100 years are possibly 

going to look like. 

So where I think the scientific community can fairly say is learning how to do that, how to transfer that information and how to 

make the—kind of that whole range of timeframes from decade to 

decades to centuries available to people who need to think in that 

regard. 

Mr. LUCAS. My fear from this increased demand for immediate 

action is pushed down from the top, perhaps unrealistic proposals 

that aren’t practical. The last thing we want to do is dramatically 

raise energy prices for America. Dr. Majkut, with the growing demand for fossil fuels worldwide, what can we do to ensure that we 

are leading the way with low-carbon energy solutions? 

Dr. MAJKUT. Well, in particular, I think the Committee should 

continue to focus on and continue to be supportive of advanced research efforts for the things we think we’re going to need in the 

future, and that means reliable, affordable low-carbon energy. And 

in particular low carbon is the key thing that the climate is worried 

about, so it doesn’t particularly matter whether that’s energy that’s 

going to come from a windmill or a fancy kind of battery or is going 

to come from fossil fuels with carbon capture and storage, or advanced nuclear. Instead, the target should be having a broad array 

of energy sources that can be used here and abroad at affordable 

levels and putting in place a research enterprise that is pursuing 

them with real vigor. 
116 

Mr. LUCAS. We make lots of investment in research in the Federal Government, and that’s an important thing. How does the private sector advance what the government has started? 

Dr. MAJKUT. Well, the private sector is going to be the thing that 

actually scales those early run projects that received justifiable 

governmental support into use, right? That’s the thing that’s going 

to matter in sub-Saharan Africa, is going to matter in Southeast 

Asia, is going to matter in Oklahoma, how do those things compete 

in the marketplace. And so making sure that those innovations diffuse out is a matter of transitional policies and market design. 

Mr. LUCAS. From the back door of my house on the farm in western Oklahoma I can see windmills, electric windmills from one horizon to the other. Dr. Majkut, you have referred to the goals set 

by the Intergovernmental Panel on Climate Change as ambitious. 

Is there a scenario in which those ambitious goals can be reached 

by transitioning to 100 percent renewable? By the way, those windmills don’t always turn. They turn most of the time. We’re a great 

source, but not all the time. Is there a scenario of how we could 

get to 100 percent renewable? 

Dr. MAJKUT. You could probably write one out on paper where 

it’s physically possible, but I don’t know that that’s a necessary 

thing to do. And in particular if, like me and a lot of my colleagues 

and a lot of folks out in the—and your constituents are concerned 

about climate and you want to reduce greenhouse gas emissions, 

having a broad portfolio of options seems like the best choice, and 

there is a raft of literature showing you that if you want a reliable, 

low-cost energy system that has a lot less carbon emissions than 

we have today, you want a wide variety of technologies available. 

Mr. LUCAS. Thank you, Doc. I yield back the balance of my time, 

Madam Chairman. 

Chairwoman JOHNSON. Thank you very much, Mr. Lucas. Ms. 

Stevens? 

Ms. STEVENS. Thank you all so much for bringing your expertise 

and time to today’s hearing. We’re privileged to be able to engage 

with you. 

Certainly on this topic we have two choices. We can either embrace the need for climate change action and the embracing of climate science through fear or we can embrace it through opportunity. And I am so grateful that Dr. Mahowald was able to bring 

her testimony to us through video. And my questions are for you 

if we’re able to ask questions of her. Are we able to do that? OK. 

Fabulous. So how are we as a country measuring up globally in 

terms of the actions that we are taking around Federal investments to develop innovative technologies and solutions to address 

the impacts of climate change? 

Dr. MAHOWALD. Thank you very much for the question. You’re 

hearing me? Good. 

Ms. STEVENS. Yes. 

Dr. MAHOWALD. The United States is starting to get the momentum to deal with climate change mitigation and adaptation. Much 

of the adaptation efforts of course have started at the local level, 

but they need to be moving across local, State, and Federal levels. 

We need to be dealing more with the adaptation efforts for climate 

change, as well as mitigation across the board. At this point the 
117 

Federal efforts have not been consistent with what needs to happen 

for the ambitious targets for climate change. And some of the 

States have been reacting much more ambitiously than others, and 

there’s several studies suggesting that Federal-level coordination of 

the States’ efforts is much more efficient for the whole system in 

terms of transitioning to lower-carbon mitigation targets. Thank 

you. 

Ms. STEVENS. Thank you. Well, I happen to represent suburban 

metro Detroit, the home of the Nation’s automotive sector, and our 

automotive industry is in the race for the future, particularly 

around energy efficiency. And they see where China and Europe is 

moving, and they’re sort of waiting on the United States. And so 

I was wondering if you could shed a little bit more light in terms 

of any projections that you might have that our country could capture in terms of return on investment. Should we be making the 

right strategic investments to lay the foundation for our industrial 

sector to be making the investments in carbon neutrality? 

Dr. MAHOWALD. Well, the transportation sector is an important 

sector, and of course Detroit is the home of that in the United 

States. Our competitors are investing heavily in low-carbon options. China is trying to get rid of internal combustion engines. 

India also has efforts in this area. The United States has the technological and the business innovation advantage. If we can use 

this, we can maintain our advantage in the automobile industry 

and other industries as well. But more coordination across the—at 

the Federal level, across the Federal, State, and local levels will 

really help in this effort. Thank you. 

Ms. STEVENS. Thank you. I think it’s fair to say that there’s the 

‘‘if not but for’’ role the government can play. Certainly industry is 

making their investments, but they’re waiting on the Federal Government to lay the foundation, set the table, as we have in many 

ways where we created the highways and we plowed fields, but we 

need to set the table. 

And I want to get Dr. Kopp in just quickly with my remaining 

time available because you also mentioned this in your testimony 

saying that climate change is not just an environmental challenge, 

it’s an economic challenge. It’s an infrastructure challenge, a public 

health challenge, and a national security challenge. And while we 

have your great expertise in the room, I was wondering if you could 

maybe give us a few points around how the United States can continue to be a leader in addressing the impacts of climate change 

while also maintaining our global economic power. 

Dr. KOPP. Well, I want to come back to the thing I said at the 

very end of my remarks, which is that we need to make climate 

change a routine and integrated part of decisionmaking, public and 

private sector, Federal, State, and local, right? We make lots of decisions, particularly when we think about, say, infrastructure investments or particularly when we think about national security 

that play out over decades. And any time we’re thinking about 

changes over decades, we’re thinking about a world where the climate is changing in ways that we can project. And so we have to 

move beyond using the past as a guide to what we do and, when 

we’re building a new rail tunnel under the Hudson, say, or we’re 

building new water infrastructure, right, those need to be planned 
118 

with all the range of possible futures that we might project in 

mind. 

Ms. STEVENS. Yes, thank you. I yield back the remainder of my 

time. 

Chairwoman JOHNSON. Thank you very much. Mr. Brooks? 

Mr. BROOKS. Thank you, Madam Chairman. 

Dr. Kopp, I’m looking at your written testimony as opposed to 

your oral testimony. On page three you state, quote, ‘‘Climate 

change is real, it is here now, and humans are responsible for it,’’ 

end quote. Is that an accurate statement of your quote? 

Dr. KOPP. Yes, it is. 

Mr. BROOKS. And on page five of your written testimony you 

state, quote, ‘‘Global average sea level has risen by about 8 inches 

since 1900,’’ end quote, citing the Climate Science Special Report, 

Earth National Climate Assessment. Is that an accurate reading of 

that quote? 

Dr. KOPP. Yes, it is. 

Mr. BROOKS. Are you familiar with the Earth’s last glacial maximum roughly 21,000 years ago? 

Dr. KOPP. Yes, I am. 

Mr. BROOKS. And is it fair to say that sea levels during the last 

glacial maximum were roughly 400 feet lower than they are today? 

Dr. KOPP. Yes, it is. 

Mr. BROOKS. And would it also be fair to say, then, the sea levels 

over the last 21,000 years, 400 divided by 21,000 or 210 centuries, 

sea levels have risen on average over that 21,000-year period of 

time at roughly 2 feet per century? 

Dr. KOPP. Well, it was concentrated in the first half of that time, 

but yes. 

Mr. BROOKS. From the 21,000- to the 7,000-year-ago period is the 

concentration, then it still increased—sea levels did—but at a much 

lower rate during the last 7,000 years? 

Dr. KOPP. When they stopped rising is a scientific uncertainty, 

but certainly that by 7,000 years ago the giant ice sheet that was 

sitting on North America was gone, and so the contribution to sea 

level that came from that ice sheet ended. 

Mr. BROOKS. So apparently, somewhere between 21,000 and 

7,000 years ago we had a very significant rise in sea levels, much 

more than the 2-feet-per-century average of the overall 21,000-year 

period. Did humans cause that? 

Dr. KOPP. No, they did not. 

Mr. BROOKS. They did not. So there are other causes to sea-level 

rises other than humans, and at least in this instance over the last 

21,000 years we’re looking at an average sea-level rise of 2 feet per 

century on average, 210 centuries, a little over 400 feet total. What 

was the cause of that? 

Dr. KOPP. Well, if you go back 21,000 years ago, my home State 

was sitting in its northern edge is under about a mile of ice, and 

that ice sheet, which we call the Lorne Tide, had a whole lot of 

water locked up in it. And so as that ice melted, sea level rose. 

We’re now in a very different world where there’s—the ice on the 

planet is largely in—almost exclusively in Antarctica and Greenland, and so what we’re concerned about now—— 
119 

Mr. BROOKS. OK. I’m not asking what we’re concerned about 

now. I’m asking what caused the 400 feet in sea-level rise over the 

last 21,000 years? Would it be fair to say that it was global warming? 

Dr. KOPP. Yes, it would be. 

Mr. BROOKS. And what is it that caused that global warming 

that began roughly 18 to 21,000 years ago? 

Dr. KOPP. So that—we were in an Ice Age roughly 18,000 years 

ago, and the differences between the Ice Ages and the periods like 

we’re in now, which are called interglacials because we’re not in a 

glacial period, are paced by changes in Earth’s orbit, amplified by 

changes in carbon dioxide. 

Mr. BROOKS. OK. So there have been fluctuations in orbit, perhaps changes in carbon dioxide, and perhaps also some change in 

the actual tilt? 

Dr. KOPP. Yes, well, when I talk about changes in orbit on that 

frequency you’re talking about where Earth is pointing, what we 

call a precession. 

Mr. BROOKS. OK. And during the last glacial maximum, is it fair 

to say that almost all of Canada was uninhabitable, along with 

New England, New York, everything north of the Ohio River was 

in effect uninhabitable? 

Dr. KOPP. Certainly on the east side of the country, yes. 

Mr. BROOKS. And would it also be fair to say that certainly at 

least in that instance, global warming was a desirable thing if 

you’re a Canadian? 

Dr. KOPP. Well, there weren’t many Canadians, but yes. 

Mr. BROOKS. Well, there weren’t any back then. 

Dr. KOPP. Over in the West there were, but yes. 

Mr. BROOKS. OK. Now, let’s talk about the remedy for a second. 

You may recall that in 2008 Dr. Steven Chu, who later became 

President Obama’s Secretary of Energy, stated that, to combat climate change, quote, ‘‘Somehow, we have to figure out how to boost 

the price of gasoline to the levels in Europe,’’ end quote, which was 

about $8.70 per gallon. Do you agree with Steven Chu that that is 

a remedy that the United States should implement? 

Dr. KOPP. Well, there’s lots of policy solutions. My job is—— 

Mr. BROOKS. I’m just asking about this one. Yes or no? 

Dr. KOPP. We are dumping CO2 into the atmosphere. One way 

of dealing with the problem would be to put a price on carbon that 

reflected the cost of that carbon dioxide is imposing on the world. 

Mr. BROOKS. Is that a yes or a no? 

Dr. KOPP. I’m going to give you the scientific answer and say it 

depends. It’s one of the solutions that would work. 

Mr. BROOKS. All right. Thank you, Madam Chairman. I appreciate the time. 

Mrs. FLETCHER [presiding]. Thank you. I’ll now recognize Mr. 

Tonko. 

Mr. TONKO. Thank you, Madam Chairman. And I thank Chairwoman Johnson for holding what I think is a very important hearing today and for our witnesses for joining us. 

I am beyond excited that, as a Committee, we are committing to 

seriously examining and addressing the urgent threat of climate 

change. I’m glad that this majority is focused on climate change 
120 

and that we have stepped up to face the task at hand. And in particular, as a Member of the Science Committee, I am proud that 

after so many years of inaction, we are moving forward and giving 

this critical issue the time and focus it deserves and requires. Inaction is expensive. 

As we address climate change, our planning must be sciencebased and evidence-based. The overwhelming majority of the scientific community knows that climate change is happening and 

that we are already feeling the impacts. The scientific evidence on 

climate change clearly tells us that we need to take action. Taking 

action means there will be challenges but also opportunities. We 

have a real opportunity to transform our economy to one that is 

cleaner, safer, and more just. We have the chance to advance cleanenergy technologies, design the infrastructure of the future that 

will help communities endure and rethink every industry we have 

ever known. Investing in solutions and resilience today will help 

manage and limit those risks and serve as a foundation for job creation, healthier communities, and economic opportunity. 

It has been a decade since the House last seriously attempted to 

address climate change, and with that, Dr. Mahowald—and I will 

address you as a fellow upstate New Yorker. And I know what 

weather can mean at this time of year, so we’re sorry that you’re 

not with us, but thank you for joining us via technology. So, Doctor, 

how has our understanding of climate science and its impacts developed over the past 10 years? 

Dr. MAHOWALD. Thank you very much for the question and for 

your understanding of upstate New York’s weather. 

Our understanding of climate science over the last 10 years has 

really benefited from the leaps in technology in terms of computer 

simulation, high—some of the big data analysis methods that we 

now have. And some of what that has allowed us to do is to really 

see the impacts of small changes in temperature on humans and 

ecosystems. And this was highlighted in the 1.5 report. 

Often what scientists do is we simply look at the big changes, but 

for this particular report we were asked to look at the difference 

between 1.5 and 2 degrees, and we focused on that. Almost 6,000 

new studies were assessed in that report and really focused on 

what small changes in temperature can do in terms of impacts on 

humans. And that report highlights that small temperature 

changes, for example, can have a big impact. Thank you. 

Mr. TONKO. Thank you very much. And when many talk about 

climate change, they associate the tone of urgency. Do you think 

there’s more or less urgency than we faced a decade ago? 

Dr. MAHOWALD. Thank you for the question. I think there’s more 

urgency. Every day there’s more people on this planet asking for 

more energy, and we’re building more facilities. And right now, the 

technologies that people use, just by default, are technologies that 

emit a lot of carbon dioxide. The faster we can start using research, 

developing and deploying technologies that don’t emit as much 

CO2, this can snowball into making it more and more economically 

feasible and politically feasible. All the infrastructure will be there 

to have lower-carbon technologies deployed. So the urgency is twofold. It’s both because we’re accumulating this CO2 in the atmosphere, and in addition, we’re accumulating infrastructure and tech-
121 

nology that emits a lot of CO2. So there’s a lot of urgency on the 

technology side, and then of course we’re seeing more and more impacts on people. Thank you. 

Mr. TONKO. Thank you very much for your input and that of Cornell routinely on these issues. 

Dr. Ebi, according to both the IPCC’s special report and the NCA 

4, climate change takes a toll on mental health. Those who survive 

extreme weather events and see their communities damaged can 

suffer from depression, anxiety, suicidal thoughts, and 

posttraumatic stress disorder (PTSD). A report notes that droughts 

have led to an increase in alcohol and drug use and higher temperatures are associated with more aggressive behaviors. How does 

climate change affect mental health, and what steps can the medical community take to ease the psychological burden? 

Dr. EBI. Thank you. That’s an excellent summary of how climate 

change can affect mental health through exposure to extreme 

events. There needs to be increased awareness about this across 

the health professions so that there are greater actions when we 

have these extreme events, that we do have mental healthcare professionals available to help people after an event. And we need a 

lot greater preparedness for these events. If the United States was 

as prepared as it should be, we wouldn’t have seen the impacts 

we’ve seen over the last couple of years. So investing in adaptation, 

investing in making sure we understand what future risks could 

look like, we’re better able then to handle all of the challenges, including the mental health ones. Thank you. 

Mr. TONKO. Thank you very much. 

With that, I yield back, Madam Chair. 

Mrs. FLETCHER. Thank you. I will now recognize Mr. Weber for 

5 minutes. 

Mr. WEBER. I thank the gentlelady from Texas. Dr. Majkut, you 

mentioned that there is, quote, ‘‘No better incentive for us than the 

private sector, but if you really want energy innovation, you need 

to show the innovators there’s a market waiting for them,’’ end 

quote. Dr. Majkut, I ran an air-conditioning company for 35 years, 

built it from the ground up, and I know that when the weather got 

hot, my business on the Gulf Coast of Texas was in great demand. 

I will tell you this: The more the Department of Energy raised energy ratings and required that manufacturers build higher-efficient 

equipment, the more that those units cost. And the more they 

cost—air conditioning went up—the more the demand for that 

high-efficient equipment went down because people were already 

hard-pressed in living their lives and they couldn’t afford higher 

prices. And on the Gulf Coast of Texas you don’t want to be without air conditioning. Now, I don’t know how many of you all live 

in the southern part of the country, but it’s extremely important 

to us. 

Applying this same developing concept to clean-energy technologies, Dr. Majkut, how do we show innovators that there is a 

demand and a market waiting for them? 

Dr. MAJKUT. Well, it depends on the area in which you’re working, right? 

Mr. WEBER. Did I mention I live on the Gulf Coast of Texas? 

Dr. MAJKUT. Sure did, sir. 
122 

Mr. WEBER. Yes. 

Dr. MAJKUT. There’s a lot of things government can do to create 

markets for innovation. A lot of them fall into other committees’ jurisdiction, right? You can use tax policy, you could use incentive 

policies. I can’t speak to the air-conditioning example largely because it’s not my area of expertise, but I do know that we can look 

at cost-cutting measures, we can look at technological innovation to 

make more efficient air conditioners as an example, less costly at 

the front. We can look at financing mechanisms that amortize a 

more efficient air conditioner costs less to use over time, so how do 

you find ways to help people make an upfront capital investment, 

et cetera. 

Mr. WEBER. OK. I’m going to move along a little bit. That’s a 

great thought. As Ranking Member Lucas said, the push down 

from the top was the last thing we want to do because it would 

dramatically raise energy prices. And then there was some discussion between the witnesses with one of the Members about raising 

those energy prices. Do we raise those energy prices to whatever 

it takes? I know, Dr. Kopp, you didn’t have an exact price, but do 

we just commit to raising them to whatever it takes? Dr. Kopp? 

Dr. KOPP. I would say a number of the policy solutions you’re 

talking about would raise the per-unit energy price, but the idea 

behind trying to get the markets to work is that you wouldn’t necessarily be raising the amount that people are spending on energy 

because, to take the air-conditioning example that Dr. Majkut was 

talking about, right, it costs a little bit more up front just like solar 

costs a little bit more than a coal-powered plant upfront—— 

Mr. WEBER. But the—— 

Dr. KOPP. But you spend less over time—— 

Mr. WEBER. OK. I—— 

Dr. KOPP [continuing]. And so not—a lot of these policies 

wouldn’t necessarily—— 

Mr. WEBER. So—— 

Dr. KOPP [continuing]. Increase—— 

Mr. WEBER. Let me move down. So, Dr. Francis, whatever price 

it takes to get to that point, is that kind of the philosophy here? 

Does it matter if we raise energy prices? 

Dr. FRANCIS. I don’t think it’s fair to say that whatever cost it 

takes, but I think we need to have a strategic plan for—— 

Mr. WEBER. Would you put a percentage on that? Raise them 10 

percent, 20 percent, 15 percent? 

Dr. FRANCIS. Energy policy is not my area of expertise—— 

Mr. WEBER. OK. 

Dr. FRANCIS [continuing]. And economics is not in my field of expertise—— 

Mr. WEBER. Fair enough. 

Dr. FRANCIS [continuing]. But I feel that putting a higher price 

on energy—— 

Mr. WEBER. Let me jump—— 

Dr. FRANCIS [continuing]. Would do what we want it to do. 

Mr. WEBER. Let me jump over to Dr. Ebi here. Any price, 10 percent more, 15 percent more? 

Dr. EBI. The question is partially what’s the price but also how 

do you manage that. And is some of that price turned back—— 
123 

Mr. WEBER. Well, that’s a growing technology, and we want 

America to be in the lead, American business and enterprise, right, 

to be in the lead for this, but I think there is a price where you 

make it so untenable for Americans that all of a sudden they kind 

of get turned off to the idea, and we don’t want to do that. That’s 

my point. 

Let me move on. Mr. Lucas said that in his State, he’s got lots 

of windmills. And I think you said you could see them from one horizon to the next. Have you ever noticed that on the hottest day 

of the year the windmills aren’t turning, and that’s why it’s the 

hottest day of the year? I mean, it’s unbelievable that—we can’t 

rely on those. 

When it comes to national security—and you mentioned this, Dr. 

Kopp, actually in your comments—we’re going to need a backup 

that our country can depend on, and it’s going to have to be fossil 

fuel. I can tell you about requirements for energy. I’m working on 

nuclear energy capability. It needs to be at the table. It needs to 

be a major part of our portfolio. So we’ve got to take these things 

into account. And I appreciate you all being here today. And I’m 

out of time, Ms. Fletcher. 

Mrs. FLETCHER. Thank you. I’ll now recognize Mr. Foster for 5 

minutes. 

Mr. FOSTER. Thank you, Madam Chair. And first, I’d like to 

thank Chairwoman Johnson for convening this important hearing. 

The climate challenges facing humanity are large, and unfortunately, serious debate on the best paths forward has often been stifled by the politization of this issue, at least in this Committee. 

For years, too often we found ourselves wasting time arguing 

with non-technical witnesses about, for example, whether or not it’s 

a matter of scientific debate, whether or not it would be a good 

thing if the Greenland ice sheet melted. But—and so I was really 

thrilled to see some of the changes that appear to be occurring in 

this Committee. 

Over the last several years I have to say on a personal note I 

have grown truly tired of introducing myself as the only Ph.D. natural scientist in the U.S. Congress. And to that end, I am thrilled 

to welcome onto the Committee and into Congress Dr. Jim Baird 

as the second Ph.D. national—natural scientist in the U.S. Congress. And I would also like to congratulate my Republican colleagues on their wisdom in appointing him as the Ranking Member 

of the Research Subcommittee. 

More to that point, I’d also like to thank Ranking Member Lucas 

and my Republican colleagues for selecting Dr. Majkut as their witness for this hearing. He’s someone with a Ph.D. in relevant 

science and someone with views who are—which are inside the scientific mainstream, and that’s refreshing. He is also someone obviously who understands that the question here is not whether or not 

this problem is real but rather what is the most cost-effective way 

of solving it, and that is a refreshing change because on this Committee, we have to look deeply at the balance of research and policy 

spending to solve this problem. 

In terms of that, the best way forward, particularly the newer 

Members on the Committee will be faced with just a mountain of 

things that have been written on this, and what I consider the best 
124 

synthesis that I’ve seen was actually presented by former Energy 

Secretary Moniz in his testimony to the Senate last week. In a report that he highlighted by the Energy Futures Initiative, which 

he’s one of the leaders on, entitled, ‘‘Advancing the Landscape of 

Clean Energy Innovation’’ really to my mind touches the main 

points of what knobs we should be operating in our government 

both in terms of technological research, private–sector efforts, and 

public-private partnerships to solve this problem. 

And so with that, I would at this point like to ask unanimous 

consent to enter into the record the report of the Energy Futures 

Initiative entitled, ‘‘Advancing the Landscape of the Clean Energy 

Innovation.’’ 

Mrs. FLETCHER. Without objection. 

Mr. FOSTER. And so now I actually have one technical question 

for the entire panel. It seems to me that one of the changes in the 

last several years in the thinking on climate, is the rising of the 

profile of methane as a significant greenhouse gas, that if you look 

at the impressive progress, apparent progress in the 

decarbonization of the United States, a big part of that is by converting coal to natural gas use. And it now appears true that a significant—a large single-digit percentage of the methane that we 

burn actually gets vented, wasted, vented directly to the atmosphere without—before combustion. And so if that is true, the fact 

that it’s such a potent greenhouse gas really negates a lot of the 

progress in converting coal to natural gas. And apparently the technology to detect the thousands of small methane leaks is tough, 

and it’s not going to be cheap. So I wonder if you had any thinking 

on what we do about the methane problem and where the research 

that could really make a difference there would be. We can just go 

down the line if you want. 

Dr. KOPP. Yes, I mean, I think we’re sort of throwing money 

away and hurting the environment when you have natural gas 

leaks and there has been a lot of discussion about how much—how 

large those leaks are. All the incentives are there to try to solve 

those problems, and if it’s not happening, that might be a good 

area for this Committee to figure out how to push it along. 

Mr. FOSTER. Yes, I think one of the difficulties I’ve heard pronounced is that it’s simply finding a very large number of small 

leaks is not cost-effective in terms of the savings in natural gas, 

and that’s one of the things that makes it tough at least with current technology. 

Dr. FRANCIS. So I would just like to bring up another issue related to methane, and that is the fact that the permafrost areas in 

the high Arctic are warming dramatically. We expect to see a lot 

more thawing happen. And when permafrost thaws, the biological 

material that’s frozen in those soils can decompose then and become either methane or carbon dioxide. And we’re seeing the 

warming happening much faster up there in general and in the 

Arctic overall. And the loss of sea ice, which is a clear symptom of 

global warming, is contributing to the acceleration of that thawing 

of the permafrost. So this is another issue that I think we need to 

take very seriously, especially in the methane discussion. 

Mr. FOSTER. Thank you. And it appears my—— 

Mrs. FLETCHER. Mr. Foster, your time has expired. 
125 

I’d now like to recognize Mr. Babin. 

Mr. BABIN. Thank you, Madam Chair. I appreciate it. Thank you 

all for being here as expert witnesses. 

And we heard a little history a while ago. I had to leave the room 

for a minute, but I did catch the end of it, very interesting because 

I love history. Are you familiar, Dr. Kopp, with the Norse settlements in Iceland and Greenland but—in and around the year 1000 

and that there was farming and animal husbandry in Greenland 

for nearly 300 years, which lasted up until about 1300 and then we 

had what we call the Little Ice Age, which lasted up until about 

1700, and then the Greenland colony disappeared. But it’s 

archaeologically sound evidence that told us that it did last that 

long. What could have possibly caused the climate to change so 

much that we would have farming and animal husbandry in Greenland for a period of 2-1/2, 3 centuries? Could you have blamed that 

on human emissions or can you give me an answer to that question? 

Dr. KOPP. So there are fluctuations that we see in circulation in 

the North Atlantic. There’s something called the North Atlantic oscillation. That might have had a role to play there. The Little Ice 

Age, which was then triggered, may have had something to do with 

volcanic emissions. The details of that are still an area of research. 

A lot of that is more of a localized phenomenon in the North Atlantic. There’s some global temperature change, but that global temperature cooling actually starts around 1000 just so you—— 

Mr. BABIN. What you’re saying is we don’t really know, but in 

the opinion of everybody sitting at the table up there, was it more 

advantageous to have a little warming going on around the globe 

or was it more advantageous to have a little cooling going around 

the globe? Because during the Little Ice Age we lost lots and lots 

of humans to various causes that are in response and as a direct 

result of dropping temperatures. How would you answer it? 

Dr. KOPP. Well, it’s a—— 

Mr. BABIN. I would say that it would be more advantageous to 

have lived in a climate that was a little bit warmer. 

Dr. KOPP. Yes, so I would say that over that period we’re talking 

about a very small change in global temperature, roughly .3 °F, so 

it’s worth keeping that in context when we’re talking about the 

2 °F, so almost 10 times as much than we’ve seen over the last century. 

Mr. BABIN. Anybody else want to answer that? 

Dr. MAJKUT. Yes, Mr. Babin, I think the way I think about it is 

not that there is an ideal temperature that we know for certain 

that human flourishing will be maximal. Science can’t really tell us 

that in a meaningful way. What we do know is we’ve built our society around the temperatures that we’ve encountered over the last 

200, 300 years. And as Dr. Kopp says, we’re fixing to change those 

temperatures quite a bit. And that rapid transition is the cause for 

concern. 

Mr. BABIN. But we do know that when Canada and the eastern 

part—upper part of the United States was uninhabitable during 

the Ice Age, that it certainly wouldn’t have been conducive to economic development. I just feel like, you know, there’s no question 

that our climate is changing, no question whatsoever, but to blame 
126 

everything on human activity and expect the United States of 

America, the taxpayers in our country, to pick up the tab to pay 

carbon taxes and for carbon footprints and lower their quality of 

life and standard of living and increase the cost of living while our 

biggest polluters around the world absolutely go scot-free and continue. So it’s hard for me to justify how we could be expected to 

pay that kind of a price. 

And I want to ask one more question, too. Do you support a 

transparent and full accounting of cost, benefits, and projected impacts to the global climate of individual climate policy proposals? 

I’m going to ask Dr. Ebi. Is it the way you pronounce your name? 

I’m sorry. 

Dr. EBI. That’s fine. It’s a difficult name. But thank you for the 

question. 

Mr. BABIN. OK. 

Dr. EBI. We do need a full accounting, and that does happen 

under the United Nations’ Framework Convention on Climate 

Change at least in terms of emissions. And we know the United 

States alone is responsible for 25 percent of all emissions. There 

are efforts to try and understand better how much the cost of those 

emissions are in terms of impacts on our health, impacts on our 

ecosystems, our livelihoods, on our economies. And there’s a growing amount of work looking at what the benefits of action would 

be. 

Just from the health sector we know that the health benefits of 

many mitigation policies are of the same order of magnitude as the 

cost of mitigation, that if we get more people to ride their bicycles, 

to walk to work, to change their diets, to have less exposure to particulates, the avoided premature deaths, the avoided hospitalizations are a very large amount of money that would offset the cost 

of emission reductions. So we do need to look much more broadly 

at the cost and the benefits, taking into account who bears the cost 

and who reaps the benefits and how to make sure that this is done 

in a way that’s as fair as possible. 

Mr. BABIN. But if we are responsible for 25 percent of the emissions, as you say, then why should we pay nearly 100 percent of 

the cost? Because it sounds like that’s the direction that you folks 

would have us go. And I think my time is over and expired, so—— 

Mrs. FLETCHER. Yes, sir, I believe your time is expired. 

Mr. BABIN. Thank you. 

Mrs. FLETCHER. Now, I actually am going to recognize myself for 

5 minutes for questions. 

And I represent the western side of Houston and the greater 

Houston area along the Texas Gulf Coast along with some of my 

colleagues on the panel. It is also the heart of the energy industry. 

And Dr. Francis mentioned hurricane Harvey in her remarks this 

morning. Harvey, as we all know, was one of the most devastating 

disasters in our history. It was also our third 500-year storm in a 

span of less than 3 years, so we are seeing increased frequency and 

intensity of weather events. We are also seeing the risks of sealevel rise and concern about storm surge in our community. 

And in our district, we understand that climate change is real, 

and we believe working together in a collaborative way is the best 

approach for us to tackle this challenge. That means collaboration 
127 

between research institutions, industry, and governments at the 

Federal, State, and local levels. So we believe that everyone has to 

be a part of the solution and a part of addressing this challenge. 

And with that in mind, I have a few questions relating to these 

topics, first for Dr. Francis. Can you tell us briefly what the science 

tells us now about the intensity of the extreme weather events that 

we’ve experienced and how that might or will change in the future? 

Dr. FRANCIS. Yes, thank you for the question. As I mentioned in 

my oral testimony, there are certain things that we know for sure 

are happening in the climate system. And Houston is probably in 

the crosshairs of a lot of those. You have seen, as you said, increased flooding. We know that heavy precipitation events are increasing dramatically. You’ve seen heat waves increasing. You’ve 

even seen drought increasing. And we also expect to see tropical 

storms intensifying more rapidly, and potentially we expect to see 

more of the very strongest tropical storms. A lot of those things are 

very clear, and what is a little less clear relates back to Harvey 

and some of the extreme events that you all have witnessed and 

experienced, and that is we’re also seeing an increase in the persistence of weather regimes. So it could be dry, it could be hot, it 

could be cold, it could be wet, but we’re seeing an increased persistence, and we believe that that is also related to climate change. 

Mrs. FLETCHER. Thank you very much. And, more broadly for the 

panel, we do believe it’s important to include everyone in working 

together on these solutions, so, in particular, do any of you have 

experience with or suggestions on how the energy industry can 

work together with your institutions and with those of us who are 

making policy to be part of the solution toward climate mitigation? 

And I should also add I believe that they already are, and certainly 

in my district most of the industries have acknowledged and are 

working to combat climate change, but any specific ideas you have 

of policies or programs you think would be helpful for this Committee to know? 

Dr. KOPP. Well, so there’s sort of a style of doing science that I 

think very much gets at this, and that’s science that is sort of 

stakeholder-engaging and the jargon is transdisciplinary, but basically the idea is start with a problem, right? The problem is the 

resilience of the energy system off of Houston. And then you’re 

going to get together the different disciplines that you need to address it, you’re going to get together stakeholders, and you’re going 

to do the research together in a partnership. And that’s a very different style of doing research than what’s traditionally happened in 

universities. And I think we need to be rethinking a little bit of 

that part of the climate science enterprise to sort of make this more 

of a problem-focused thing. 

Mrs. FLETCHER. Thank you. Dr. Ebi? 

Dr. EBI. Thank you. It’s a very good question, and I want to echo 

that working with stakeholders is critically important in this process. And to step back more broadly and say that companies want 

to have healthy workers and healthy communities. They don’t want 

to see their workers flooded, they don’t want to see the impacts on 

their workers and on their families. And so there are ways that one 

can work together to try and ensure the resilience of the community while the companies work to ensure their own resilience to 
128 

make sure that, as these extreme events occur, they are not affected, that their facilities are not affected, so facilitating those 

partnerships at the Federal, State, and local levels is critically important. 

Mrs. FLETCHER. Thank you very much. My time has expired, so 

I will yield back the remainder and now recognize Mr. Baird for 5 

minutes. 

Mr. BAIRD. Thank you, Madam Chair. And this is my first congressional Committee hearing, so I hope you’ll excuse me if I make 

any procedural errors. And I’d prefer you not express those to me. 

I’ll just take that. I’m honored to be here in that capacity and to 

be able to have the discussion that we’re having today about climate change. I do appreciate my colleague Dr. Foster for those 

kind words. 

But as a farmer and an animal scientist, I know the importance 

of leaving the land healthier than how we found it for our next generation. I’ve got grandchildren, but I think it’s important to those 

children and grandchildren. And so the health of the land has always been a concern for agriculture people, and that is important 

to our ability to feed ourselves. 

But in that vein, I also recognize that the natural evolution process over time, the tremendous ability of mammalian tissue or mammals and plant tissue to adapt to their environment, I don’t see 

much discussion about that in some of the presentations. But I do 

find your presentations extremely interesting and very insightful. 

I would like to just point out a couple things. Dr. Ebi, not picking 

on you in any particular reason, but, for example, we mention 729 

children died from heatstroke from 1990 to 2014, so I guess my 

question there is, is that because the automobiles were better, or 

the children are less exposed to their environment than we have 

in previous centuries and so on? So I think we need to take those 

kind of factors in when we make those predictions about the impact 

of the climate on some of the issues we’re concerned about. 

For example, the elderly, are we older as a generation, so we’re 

becoming more susceptible as we age and so compared to 50 years 

ago we’re living a lot longer. And so those are just things that if 

you want to respond to that, you’re welcome to. It was really more 

of a comment than anything, but I’ll give you that option. 

Dr. EBI. Well, thank you. And thank you for those comments, 

and I do have a couple of short responses. On the evolution, the 

climate now is changing faster than it’s been in 10,000 years, and 

so it is a challenge for many of our plants and other species to try 

and evolve fast enough in the face of this rapid rate of change. 

In terms of the children dying in cars, the data were only collected over a certain period, so we don’t have data from before 

then. But the point is as temperatures are going up and we’re seeing more heat waves, we’re seeing higher temperatures in summer, 

people don’t realize how quickly cars heat up. And so it’s terribly 

unfortunate how many infants are dying in cars because people 

don’t realize, as they say I’m only going to be gone for a minute, 

that that minute may be too much for an infant in the higher temperatures we’re experiencing now. 

Mr. BAIRD. I really understand that and can appreciate that, and 

I think that’s a tremendous mistake that parents make. But my 
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question comes back to, is that because the cars are tighter, the 

windshields are better, the glass heats up more, and so on? No excuse for leaving those children, and I don’t want to comment about 

that. That’s OK. We’re OK there. 

But I do have some questions for Dr. Majkut. In the developing 

field of technology, the United States, I think we ought to be a 

leader in that because we have the ability and the talent to do it. 

We have the research capability. So my question to you is, are we 

behind other countries in our developing a cleaner environment, 

cleaner energy sources? 

Dr. MAJKUT. It’s a tough question to answer. I think the answer 

probably varies on exactly where you answer. I think in bulk, no. 

The U.S. research enterprise is really strong. We provide a lot of 

resources to that enterprise. And if you look at environmental performance not just on climate but on other issues over the last decades, we’re doing pretty well. 

Mr. BAIRD. So would it be fair to say that our country makes a 

lot more investments in cleaner energy sources than another country around the world in terms of reducing our pollution even 

though we use a lot of the fossil fuels? 

Dr. MAJKUT. I don’t know. I don’t know the relative spending, 

sorry. 

Mr. BAIRD. OK. Agriculture is extremely important, as I expressed. It’s extremely important to my district, and so we have 

Purdue University in the area, and Dr. Dukes has also provided 

some assessment of what the climate change has on agriculture, 

but it can impact growing season, plant growth, animals, and some 

of the things that’s already been discussed. So what do you think 

we ought to be doing right now to correct these areas? What are 

some of the things you think you might be able to do relatively rapidly? 

Dr. MAJKUT. On farming specifically? 

Mrs. FLETCHER. The gentleman’s time has expired. 

Mr. BAIRD. All these procedures, I tell you. Thank you very 

much. 

Mrs. FLETCHER. I now recognize Mr. Bera—Dr. Bera. 

Mr. BERA. Thank you, Chairwoman Fletcher. You look good in 

that chair, by the way. 

First off, it is glad that we’re kicking off this Congress and this 

Committee with a hearing on climate science, on climate change 

and really taking a look at what we can do to try to mitigate this. 

And you will hear aspirational goals. You can call them whatever 

you want, if it’s a Green New Deal or something, but aspirational 

goals are not things that we should shy away from as the United 

States. 

If we look at our own legacy and our own history going back to 

the—throughout our history but, recent history in the 1960s when 

President Kennedy challenged us to go to the moon, we had no idea 

how we were going to do it. It was an aspirational goal, but we put 

all of our intellect, industry into that, and we accomplished it. And 

we accomplished it faster than the President challenged us, so let’s 

not be afraid of setting these aspirational goals. And we know from 

going to the moon and the whole Apollo program, it was economi-
130 

cally sound as well because we can think about all the industries 

and innovation and discovery that came from that. 

I’m proud to be a Californian. I’m a lifelong Californian. And in 

our State we did pass legislation recently that moves us to the goal 

of 100 percent clean energy by 2045. That is an aspirational goal. 

But we also know we’re the fifth-largest economy in the world. It 

hasn’t stifled our economy. In fact, there’s over 500,000 clean and 

renewable energy jobs in California, and that’s growing. So, again, 

we don’t have to be afraid of setting those goals. 

Dr. Kopp, I think you mentioned getting to that goal of net-zero 

global greenhouse gas emissions. I think that’s an aspirational 

goal, but let’s set that goal out there and then let’s work toward 

it and use our innovation and intellect to get there. 

I’ve got from a science perspective and a question—and I’ll let all 

the witnesses comment on this—there’s also the issue of the carbon 

that is already sequestered in our atmosphere. And from the scientific perspective, what are the things we’re not talking about 

mitigating future emissions, but are there ideas out there for us to 

degrade the carbon that already is up there that is trapped? 

Dr. KOPP. I don’t know if Dr. Mahowald wants to take first crack 

at that. 

Mr. BERA. Sure, whoever wants—go ahead. 

Dr. MAHOWALD. I’m happy to speak if I’m able. 

Mr. BERA. Yes, please. 

Dr. MAHOWALD. The removal of carbon dioxide from the atmosphere is—innovative new technologies are moving in this direction, 

and we do need more investment in this type of research development and deployment of these technologies. There are some sectors 

that are going to be very difficult to cut the CO2 emissions from, 

and removing carbon dioxide from the atmosphere is a very good 

method of reducing climate risk at the same time as we are working to mitigate as well as adapt in other areas. So, for example, if 

you want to sequester more carbon in agricultural soil, this not 

only reduces the carbon dioxide in the atmosphere, it also makes 

the agricultural soil more resilient to climate change as an example. But there’s two recent National Academies reports on how to 

look at carbon dioxide removal, and I think it’s an area that the 

United States should invest more research and set up the business 

environment to allow companies to invest more in. Thank you. 

Mr. BERA. Great, thank you. Dr. Kopp? 

Dr. KOPP. Yes, just to add onto that, there’s a wide range of approaches you can take from expanding forests, which is slow but 

we know works, to a variety of technological approaches. As I said 

in my opening remarks, they’re sort of new and untested. I think 

one thing to keep in mind is that the amount of warming we have 

is roughly proportional to the—all the CO2 we’ve emitted, so if we 

want to reverse warming by removing CO2 from the atmosphere, 

we’re going to have to talk about building infrastructure that’s of 

a scale comparable to that that we’re currently using to put CO2

into the atmosphere, right? So the first use of these technologies 

is going to be, as Dr. Mahowald mentioned, for areas where it’s 

hard to get the CO2 out. But if we want to talk about reversing climate change, you’re talking about a huge growth of this area using 

technologies that are still really to be developed. 
131 

Mr. BERA. Right. Any last comments, please? 

Dr. EBI. One last comment to go to what you said at the beginning, I’m at a very large State university, and students are so excited about the possibilities of working in this area. Students want 

to contribute to the solutions. They want the training so that they 

can be part of this transition that we’re going to undergo. 

Mr. BERA. So it’s a lot like those of us who were growing up in 

the 1960s during the space race. It’s inspiring. And let’s not be 

afraid of setting those aspirational goals. 

I’ll yield back. 

Mrs. FLETCHER. Thank you. And before we move on to our next 

questions, I would like to enter into the record without objection a 

consensus letter to Congress from 31 nonpartisan scientific societies that acknowledge and affirm human contributions to climate 

change and notes the severity of climate change impacts is increasing and is expected to increase substantially in the coming decades. 

And with that, I recognize Mr. Waltz for 5 minutes. 

Mr. WALTZ. Thank you, Madam Chairman. 

So my district’s in northeast Florida. I grew up on Florida beaches. The seas are rising. Anyone who’s grown up there knows that 

the beach is smaller than when I was a child. I just don’t see how 

that’s disputable. But I do want America to lead this effort. We’ve 

led the world in coal, oil, and gas development. Now we need to do 

it with rapidly growing clean-energy markets. I think to succeed we 

need a very broad portfolio of—emphasis here—low-cost technologies to speed the transition to renewable cleaner energy. I 

think that includes nuclear undeniably. 

I would caution my colleagues, we have seen a lot of aspirational 

goals lately. I think we need to be very careful about crossing the 

line from aspirational to outlandish goals that could harm our 

economy and frankly give the edge to our global competitors in 

doing so and frankly take us backward in this effort. 

So I’m very concerned as a veteran as well about the national security implications of global warming. I have first-hand seen and 

unfortunately could not count the amount of soldiers that have died 

carrying diesel fuel back and forth to outposts that we could have 

sustained through clean technologies. I’ve seen—not to mention our 

global supply chains and not to mention I’ve spent a lot of time in 

Africa, Lake Chad basin where we’re dealing with the destabilizing 

effects in Nigeria, Niger, what have you. 

So my question for each of the panelists is what R&D—I mean, 

Dr.—did I say this right—Majkut? 

Dr. MAJKUT. Majkut. 

Mr. WALTZ. Majkut, excuse me. You said we’re doing pretty well 

in our investments, particularly relative to the rest of the world, 

and my question for each of you is, where are we not—across the 

menu of clean-energy technologies, where do we need to do more? 

And again, keeping this in the context of our broader economic 

base that I think we need to sustain all of these efforts. So where 

could we do more? Geothermal—and I’d ask you to choose. The answer can’t be yes, all of the above. 

Dr. MAJKUT. Let me say first we could be doing more, right? Like 

the scale of the challenge and a lot of the concerns that your colleagues point out about increasing costs with present-day tech-
132 

nologies to reduce greenhouse gas emissions, those are real and 

valid concerns. And in particular, you can’t expect these things to 

scale unless the prices at which they’re trading are competitive. So 

on the whole, doing more is not necessarily a bad thing, and then 

doing more smartly is probably the thing that the Committee 

should really pay attention to. 

When I read these IPCC reports or the National Climate Assessment or these other documents, the places where it seems like the 

technology hasn’t caught up with the need, carbon capture and 

storage is one, right? This allows us to use fossil fuels without— 

for power generation and take advantage of all of their desirable 

characteristics without emitting—— 

Mr. WALTZ. To make it more cost-effective or just to do it? 

Dr. MAJKUT. In large part simply to do it. There are very few facilities—— 

Mr. WALTZ. OK. 

Dr. MAJKUT [continuing]. At which this is happening. 

Mr. WALTZ. But just in the interest of time, my understanding 

is the majority of our dams in the United States do not generate 

electricity. Nuclear accounts for about 1/5 of the United States’ 

electrical generation right now. And then of course, we’re seeing 

just a boom in natural gas and where we can go with it. Would you 

agree that those are all areas where we can make greater investments that would make a difference on this issue? 

Dr. MAJKUT. Yes. 

Mr. WALTZ. Would any of the other panelists want to weigh in 

on either of those questions? 

Dr. FRANCIS. Thank you. So I’m from Massachusetts, and in 

Massachusetts we’ve had incentives for solar energy for about a 

decade now, and many roofs have solar panels on them. To put a 

solar array on your roof now, the payback period is about 6 years 

before you start basically making money on your investment. It 

saddens me to fly over your State frankly because I look down and 

I see almost no roofs with solar panels on them, and you’re just 

missing a huge opportunity. And yes, it took some incentives to get 

the ball rolling down the hill, but now, the incentives in Massachusetts are disappearing and still people are putting solar on their 

roofs. 

Mr. WALTZ. I would point out to that in Samsula, Florida, Florida Power & Light has a 1,200 solar facility, and it’s estimated to 

provide electricity to 14,000 homes, 30 million solar panels by 2030, 

but I’m sure we could all collectively do more. Those are State incentives to be clear—— 

Dr. FRANCIS. That’s—yes. 

Mr. WALTZ [continuing]. At the State level or local level. 

Dr. FRANCIS. Yes. 

Mr. WALTZ. Thank you so much. I yield my time. 

Mrs. FLETCHER. Thank you. I now recognize Ms. Bonamici for 5 

minutes. 

Ms. BONAMICI. Thank you very much, Madam Chairwoman. 

I want to thank Chairwoman Johnson and Ranking Member 

Lucas for holding this hearing, and I also wanted to take just a moment to say congratulations to the environmental—Environment 
133 

Subcommittee Chair Representative Fletcher and wish her a very 

happy birthday. Thank you. 

Mrs. FLETCHER. Thank you. 

Ms. BONAMICI. So thank you to the witnesses for being here 

today. The science is clear. I’ve been on this Committee the entire 

time I’ve been in Congress. We’ve had this conversation many 

times. This—consequences of inaction on climate change will be serious and swift. The findings of the recent report from the International Panel on Climate Change, the IPCC, and the Fourth National Climate Assessment are not just a wake-up call; they are an 

alarm. At the time when the world is facing record heat waves, 

droughts, more acidic oceans, rising sea levels, and a surge of—in 

extreme weather patterns, we must fight for comprehensive policies 

to protect the health of our oceans and our planet. 

I was concerned when the Trump Administration appeared to be 

burying the Fourth National Climate Assessment. They released it 

late on a—like late on a holiday weekend, so I shared findings from 

the assessment on Twitter every day for 6 weeks to call attention 

to the assessment when the President dismissed the findings in a 

Washington Post interview last year. I worked with my colleague 

on this Committee, Mr. Beyer. We led 96 of our colleagues in urging the President to heed the dire warning of the assessment and 

work with us to protect the health of our planet. 

The assessment is the most comprehensive science-based evaluation of the consequences of climate change, the risks of inaction 

and potential adaptation strategies for the United States to date. 

We cannot and should not dismiss its findings. 

Dr. Ebi, according to the air quality chapter, volume 2, of the assessment, more than 100 million people in the United States live 

in communities where air pollution exceeds health-based air quality standards. Climate change will increase the risk of unhealthy 

air quality. How are children, older adults, low-income individuals, 

communities of color, and those experiencing discrimination disproportionately affected by climate change, and what could we do 

to mitigate the health consequences of climate change for these vulnerable populations? 

Dr. EBI. Thank you for the question. And this is a very serious 

concern that there are people who are differentially exposed to poor 

air quality. It’s from particulate matter, it’s from ozone, and it’s 

also from things like pollen. And so people in the groups that you 

mentioned often live in communities that have much higher exposure, and it’s an opportunity, going back to the question we had a 

few minutes ago, of looking at issues like energy efficiency to make 

sure that we reduce how much comes out of our tailpipes so that 

people don’t have so much exposure. 

I will note that the United States cannot sell cars in China because we cannot meet their emissions standards. So there’s lots of 

opportunities to reduce emissions. Reduced emissions also from 

coal-fired power plants is incredibly important to protect people’s 

health. 

Ms. BONAMICI. Thank you. We also save healthcare costs, and we 

want to do that obviously. 

Dr. Kopp, I noticed in your written testimony there’s a sentence 

that you have in there about in 1990 President George H.W. Bush 
134 

signed the Global Warming Response Act of 1990. I just want to 

note that that was a long time ago, and we still need to respond. 

The coastal effects chapter of volume 2 of the Fourth National 

Climate Assessment states that 13.1 million people are potentially 

at risk of needing to migrate because of sea-level rise by the year 

2100, creating drastic consequences for socially and economically 

marginalized and low-income groups. In your testimony, you discuss how climate change is an infrastructure challenge. We’re having a lot of infrastructure conversations here on the Hill. What infrastructure investments and strategies should Congress address 

now to prepare for rising sea levels and avoid catastrophic damage? 

Dr. KOPP. Well, of course, that’s a complicated question because 

infrastructure is fundamentally local, and so the answer is going 

to differ depending on where you are. The fundamental thing is if 

you’re building infrastructure that’s going to be around for 80 years 

like—it is foolish not to take into account changing climate conditions and changing sea-level rise for that period and know when 

you build that what you’re going to do if it turns out we’re on a 

relatively, say, low sea-level rise course and what we’re going to do 

if it turns out we’re on a relatively high sea-level rise course. We 

aren’t—we don’t know yet because it depends both on ice sheet 

physics that are still being studied and on greenhouse gas emissions that we haven’t admitted yet whether we’re going to see 2 

feet of sea-level rise over the course of this century or more than 

6 feet. And those have very different implications, and so we need 

to be thinking about we can build flexibility into our designs and 

coupling the infrastructure designs and deployment to the science 

that will tell us that information as soon as it can. 

Ms. BONAMICI. Thank you very much, Madam Chairwoman, and 

I am just about out of time, so I yield back. 

Mrs. FLETCHER. Thank you. I’ll now recognize Mr. Norman for 5 

minutes. 

Mr. NORMAN. I want to thank the panel for taking the time. 

Mr. Majkut, I think what’s been said here—and I’ll ask all the 

panel—this country’s—and I’m from South Carolina. I’m a real estate developer. Is the figure right? We contribute 20 percent to 

emissions as opposed to other countries? 

Dr. MAJKUT. If I’m correct, it’s slightly less than like, maybe 15, 

16, but ballpark it’s right. 

Mr. NORMAN. OK. And I’ve heard the other comments that everybody needs to pay. How do we—if we’re 16 percent—pick your figure—how will we make the other 82 percent pay their fair share? 

Dr. MAJKUT. So like, first of all, we can generate a lot of innovative technologies here in the United States using our research enterprises that are exportable. We can share that knowledge 

through formal arrangements or informal ones or simply through 

exports. We can also demonstrate using a variety of policy instruments that it is possible to have a thriving economy and a healthy 

society with lower greenhouse gas emissions, and we can export 

those models as well. 

Mr. NORMAN. OK. Anybody—any of the other panelists have any 

comments on that? 

Dr. MAHOWALD. I’d be happy to comment. 

Mr. NORMAN. Yes, ma’am. 
135 

Dr. MAHOWALD. The other thing to recognize with this very good 

question is that under the Paris Agreement, countries have voluntarily agreed to cut emissions, and people have evaluated the cost 

of these and the relative cost to gross domestic product (GDP). And 

actually the United States’ voluntary contribution is actually quite 

low compared to its GDP. So other countries are volunteering to do 

more than their fair share. Thank you. 

Mr. NORMAN. If that’s the case, then it’s really apparent now we 

need to put a price tag on—prioritize or put a price tag, is that 

right, on what this is going to cost like the green energy deal 

that—we’re probably going to vote on. It’s a nonbinding resolution. 

But before we go doing away with flatulent cows, airplanes, we 

need to put a price on it, don’t we? 

Dr. MAJKUT. Yes, from a public policy perspective we should always be cognizant of the costs and benefits of the choices we’re 

making and try to be judicious in moving forward, seeking low-cost 

options. 

Mr. NORMAN. Yes. And in my world, you find your goal, put a 

price tag on it, and then move from there. And I think everyone 

would agree this is going to cost dollars. It’s going to cost and I 

think Mr. Kopp—Dr. Kopp, you wouldn’t put a figure on how much 

we’re going to have to pay for gas, but it’s going to be more expensive than what we’ve been paying, is that right? 

Dr. KOPP. Yes, so I think certainly the upfront cost of energy will 

go up, but average costs may go down. And I think it’s really important that when we look at the costs, we’re looking at the costs 

of climate change in comparison; there’s a lot of economic work 

going on to try to evaluate those two, and these have to be balanced against one another. 

Mr. NORMAN. They have to be balanced. And would it not be fair 

with increased costs, whatever figure we end up with, you’re going 

to rule out some of our most vulnerable communities that are not 

going to have access to energy, as an example. What kind of cost 

would that be to them and their health through PTSD, through 

their mental health? How would we put a number on that? 

Dr. MAJKUT. Well, I mean, I think the intent is not to like overly 

punish any particular class of people or any particular technology. 

It’s to put in place a system that we all are going to benefit from 

in the long-term. And that means that for day-to-day activities that 

people are going about, that they’re able to do that in a low-carbon 

way. Great. What we need to do as a society is find ways that that 

doesn’t end up being too costly. And frankly, I don’t know that it 

is going to be too costly. It’s just a matter of making smart investments, leading the way to innovation, and then scaling those up 

through the private sector. 

Mr. NORMAN. Dr. Majkut, if, as an example, this Green New 

Deal were implemented immediately, wouldn’t you agree it’s going 

to devastate our economy, and other countries are going to take up 

the practices that we are eliminating as in the cows that they 

grow, the other areas that we are going to have to—they will make 

the difference up in this even though we don’t? 

Dr. MAJKUT. Yes, in fact, the Green New Deal is a moving target, 

not sure what it is, but based on my understanding from the resolution that’s been introduced, as well as the things that have been 
136 

said by its primary backers, the decarbonization, that is reducing 

the CO2 associated with economic activity, is one of the cheapest 

elements of the Green New Deal. 

Mr. NORMAN. Thank you so much. I’m out of time. I yield back. 

Mrs. FLETCHER. Thank you. The Chair will now recognize Mr. 

McNerney for 5 minutes. 

Mr. MCNERNEY. I thank the Chair and I thank the witnesses 

this morning. 

Natural gas sounds great compared to coal, but the more effectiveness of natural gas and reflecting infrared radiation compared 

to carbon dioxide means that if just 2 percent of the produced gas 

escapes into the atmosphere, the efficiency benefit over coal is lost. 

Does anyone on the panel disagree with that? No? Does anyone 

want to make a remark about that? OK. Thank you. 

Dr. MAHOWALD. If I could say something? 

Mr. MCNERNEY. Sure, go ahead. 

Dr. MAHOWALD. Well, thank you for the question. One of the differences between methane and carbon dioxide is how long they reside in the atmosphere, so in the short-term methane can be very 

bad for the climate, as well as for air quality, but most of the impacts of methane are actually on air quality. But methane only 

lasts about 10 years in the atmosphere whereas carbon dioxide, 20 

to 30 percent of it is going to last centuries to thousands of years. 

So in terms of trying to solve the really big climate problem, we 

should focus on CO2. Methane is a big problem for air quality, especially and a little bit for climate, but we should try to mitigate 

the methane as much as possible. But it is actually lucrative to 

capture, so it’s a much easier target. 

Mr. MCNERNEY. That’s a good point. We need to capture it—— 

Dr. MAHOWALD. Studies show that it’s economic—that it’s actually economically feasible—— 

Mr. MCNERNEY. OK. 

Dr. MAHOWALD [continuing]. To capture much more methane if 

people were careful about it. 

Mr. MCNERNEY. Thank you. Dr. Kopp, how can positive feedback 

loops accelerate climate change? 

Dr. KOPP. Well, there—positive feedback loops are sort of a core 

part of how the climate system works, so to take one example, if 

we put more CO2 into the atmosphere, that causes some amount 

of the warming. It causes melting of ice in the Arctic. It makes the 

Arctic less reflective, so that causes more warming. When we talk 

about, say, tipping points in the climate system, which is language 

I don’t love but is used, there—all of those tipping points are driven by positive feedbacks having to do with things like, for instance, 

ice sheet ocean interactions leading to rapid loss of the Antarctic 

ice sheet. 

Mr. MCNERNEY. OK. Dr. Ebi, briefly, would you identify some research that the Federal Government should be engaged in on climate change it’s not doing right now? 

Dr. EBI. Thank you for the question. There are so many opportunities to increase the research enterprise in this area. I’ll speak 

specifically for health. There is almost no Federal research dollars 

going into research on the health impacts of a changing climate 

and how we can adapt more effectively to that, so any kind of in-
137 

vestment would be very beneficial for the health of Americans and 

for our healthcare infrastructure. 

Mr. MCNERNEY. Thank you. Dr. Kopp, I understand that most or 

all climate models underestimate or even grossly underestimate 

the rate of climate change. Do you agree with that? 

Dr. KOPP. So I think what you’re referring to is the statement 

in the climate assessment looking at the ability of climate models 

to reproduce past warm periods, and there’s definitely a systematic 

tendency of climate models if we compared them to the geological 

record, not to produce as much warming as we see evidenced in the 

geological record. 

Mr. MCNERNEY. Well, given the state that we’re in that the climate effects we’re seeing now are due to carbon dioxide that was 

introduced into the atmosphere decades ago, do you think we can 

avoid a 1.5 °C increase by just reducing carbon emissions alone? 

Dr. KOPP. As I think the 1.5 °C report tells us it is possible physically but it may be challenging. If we—we have to get greenhouse 

gas emissions to net zero very quickly if we want to do that. 

Mr. MCNERNEY. Well, I think because of that, we need to expand 

our research into climate intervention, and not that I want to go 

there, but given that 1.5-degree change is almost inevitable and 2- 

degree change is likely in my opinion, we need to understand the 

tools that would be available to avoid catastrophic change if it 

comes to that. Would you comment on that? 

Dr. KOPP. Yes, so I think it’s very clear it would be very helpful 

to have more effective technologies for removing carbon dioxide 

from the atmosphere, so that’s one category of climate intervention. 

There’s another category that has to do with putting—sorry, pollution in the stratosphere to make the planet more reflective, and I 

think that needs a lot of careful analysis to see what the risks are 

and whether that would be feasible from both a technological and 

policy perspective. 

Mr. MCNERNEY. Right. So we need to do research in order to understand what the risks and what the potential benefits of that 

would be? 

Dr. KOPP. Yes. 

Mr. MCNERNEY. Thank you. I yield back. 

Mrs. FLETCHER. Thank you. The Chair will now recognize Mr. 

Gonzalez for 5 minutes. 

Mr. GONZALEZ. Thank you, Madam Chair. Thank you to everybody for being here. 

As a newly elected Member of Congress, I just want to mention 

first how excited I am to serve with everyone on this Committee 

and look forward to working on bipartisan solutions that will make 

the American people proud. 

So I believe that climate change is real, and global industrial development is a contributing factor. I also believe that my first responsibility and my unyielding loyalty is to the hardworking men 

and women of Ohio’s 16th District and the economy that allows us 

to heat our homes, fuel our vehicles, and build our businesses. As 

I look at the most recent proposal, the Green New Deal, I cannot 

help but believe that this would put a tremendous burden on my 

community. 
138 

My community is proud of our blue-collar roots. We are proud of 

the products we make, the crops we farm, and the jobs that we 

hold. Simply put, the Green New Deal would threaten all of that. 

And we only really need to look to Germany and their what I’ll 

call ‘‘Green New Deal Lite,’’ for an example. Since 2000, Germany 

has spent an estimated Ö189 billion or about $220 billion in renewable energy projects while emissions have been stuck at roughly 

2009 levels and even rose recently. According to the Wall Street 

Journal, taxes and rising power generation costs have made Germany’s electric rates the highest in Europe. In sum, they’ve spent 

a lot of money, raised taxes and energy prices, and nothing really 

happened. 

The proponents of the Green New Deal are proud to admit that 

their plan represents a fundamental remaking of America’s economy. They believe in a system that relies on a near full government 

takeover of some of our most important industries to solve our 

most pressing problems. With Germany’s example and common 

sense as our guide, we simply know that this will not work. 

But it’s not enough to point fingers. As I said, this is real. We 

do have a problem, and the government can play a role in helping 

solve it. What I believe is the most reasonable path forward is a 

path that does not focus on a Federal takeover of our economy but 

rather a path that fosters a diverse set of energy sources and seeks 

to make alternative energy as affordable and reliable as the traditional sources we use today. And for that I do not wish to rely on 

government takeovers of our biggest industries but rather I want 

to focus on empowering the American people and unleashing the 

most powerful economic force in human history. If we do this, then 

we will be able to reduce carbon emissions at home but also abroad 

as we are able to commercialize these to-be-developed technologies 

and sell them around the world. And best of all, we will do that 

without having to ask my communities to pay a very steep price. 

With that, Dr. Majkut, could you comment briefly on the extent 

to which this is a global issue versus one we can solve on our own? 

And based on your understanding of global development patterns 

specifically in China, India, and Africa, how feasible and realistic 

is it to exclude fossil fuels from all sources of energy globally? 

Dr. MAJKUT. Thank you for the question. I think you’ve really hit 

the nail on the head, right? The science tells you this is a global 

issue. Atmosphere doesn’t care where carbon dioxide molecules 

come from. They have the same warming affect no matter where 

their source was combusted if it’s a fossil fuel source. 

What the United States can do is work to innovate the technologies we believe we’ll need to have not just an economy similar 

to today’s but one that is much larger globally and finding smart 

ways to make sure those technologies make it to market. And 

that’s an advanced research agenda, that’s industrial policies, and 

it’s market and finance design questions. 

Mr. GONZALEZ. OK. And then cost is obviously very important, 

and I think we focus a lot on that, which is right. But when I speak 

to our manufacturers, one of the issues that they talk about a lot 

is reliability of the grid. So if we were to switch to these technologies, the renewable technologies today exclusively, we turned 

the Green New Deal on today, would we even be able to manufac-
139 

1 Based on Climate Central’s Surging Seas Risk Zone Map (sealevel.climatecentral.org), much 

of the golf course at Mar-a-Lago floods at a water level about 3 feet above the current hightide line, and the swimming pool floods at a water level of about 5 feet above the current hightide line. Currently, the water level reaches about 1 foot above the high-tide line about once 

a year. Thus, the Mar-a-Lago golf course would be expected to flood annually with about 2 feet 

of sea-level rise, a level that will most likely be exceeded in south Florida in the 2060s or 2070s 

under a high-emissions scenario and around the end of the century in a low-emissions scenario. 

Continued 

ture? Would our manufacturers be able to rely on the grid as it’s 

currently constructed? 

Dr. MAJKUT. I don’t think so, no. It seems like the lights would 

go off. But that doesn’t mean that you couldn’t change over the 

course of a few decades, which is what we’re trying to do. 

Mr. GONZALEZ. Right. And then my last question and I hate 

these up or down ones, so I apologize, but when you think about 

the Green New Deal as you’ve seen it—and I know the details need 

to be fleshed out—do you believe that is a realistic path forward? 

Dr. MAJKUT. No, sir. I think—— 

Mr. GONZALEZ. Thank you. 

Dr. MAJKUT [continuing]. It’s a broad progressive agenda 

greenwashed by some climate details. 

Mr. GONZALEZ. Thank you. And I yield back the balance of my 

time. 

Mrs. FLETCHER. Thank you. The Chair will now recognize Mr. 

Cohen for 5 minutes. 

Mr. COHEN. Thank you, Madam Chair. First, I believe the New 

Green Deal is aspirational, and I think it’s important that it puts 

attention on the dangers to our planet at this time and the urgency 

of our actions. Some of the specifics certainly aren’t going to happen any time soon. Some of them will probably never happen at all. 

But the concept of putting people’s minds and attentions to climate 

change is very important. Does anybody disagree that it’s not an 

important matter to inform the public of the urgency of the 

changes that will occur to our planet? Thank you. 

That’s why I’m a sponsor of the bill because it brings attention 

to the issue. It’s getting warmer and warmer, hotter and hotter, 

more violent weather, hurricanes because of the warming oceans 

and currents, and rising levels—the sea level, endangering what 

we’ve known. I’ve read that Miami Beach could very easily be underwater and it oftentimes has water on Collins Avenue that they 

have to pump. I think where we ought to concentrate on is Mara-Lago and what are the climate consequences to Mar-a-Lago if we 

don’t act? Can anybody give me an idea about how long it might 

be before the oceans rise to a level to where Mar-a-Lago might be 

underwater? 

Dr. KOPP. So I don’t recall exactly how high Mar-a-Lago is. 

Mr. COHEN. It depends on the night and who’s sponsoring the 

party I understand. 

Dr. KOPP. But we could be looking at sea-level rise anywhere between 2 and 6 feet, and I think under—in this century, depending 

partially, as I said, on ice sheet physics and partially on how much 

CO2 we put into the atmosphere. And my suspicion—because I 

have actually looked at this before; I just don’t recall the details— 

is that certainly under those higher scenarios you might be looking 

at permanent flooding to some of that property. 1
140 

The swimming pool would be expected to flood annually with about 4 feet of sea-level rise. 

Under a high-emissions scenario, we would estimate that the 4-foot threshold has between a 

15 and 83 percent chance of being exceeded by the end of the century, depending on the approach used to estimate how fast Antarctica will melt. 

Mr. COHEN. What if the—if this happened, your 2 to 6 feet—and 

I know it’s decades and whatever, but they’re going to be—— 

Dr. KOPP. Oh, yes. 

Mr. COHEN [continuing]. Generations of people to be Mar-aLagites. Do they—what if they built a big seawall, a big beautiful 

seawall at Mar-a-Lago? Would that do any good against the ocean? 

Dr. KOPP. So the challenge in south Florida is that a lot of it is 

limestone that has—is porous, and so that means that the ocean 

water isn’t just coming from the side, it’s coming from underneath. 

So it’s sort of hard to protect south Florida only with seawalls. 

Mr. COHEN. That’s kind of like El Chapo. He came from underneath, he came from over, so the walls wouldn’t do any good there 

either. 

People have talked—the gentleman from South Carolina talked 

about the cost of all this and there are costs to doing things with 

industry, but there are tremendous costs if we don’t do anything. 

The air-conditioning bill at Mar-a-Lago would have to go up as it 

gets hotter and hotter and hotter. Has anybody done a study on the 

dollar cost, the fiscal cost to business if we don’t take action? 

Dr. KOPP. So we’re part of a collaboration called the Climate Impact Lab together with the University of Chicago, Berkeley, and 

Rhodium Group, and those are exactly the sort of questions we are 

working on. We’re still working toward some of that, but the approach we use is sort of to look at things like, for instance, how 

different years in the past have led to different air-conditioning expenditures, take the energy sector as an example, and how that 

varies based on how hot it is usually and how wealthy people are 

and use that to project forward. So this is a really cutting-edge 

area in climate research we’re sort of working toward using big 

data approaches to do—answer those sorts of questions. 

Mr. COHEN. So a lot of the issues that will arise like the use of 

more air conditioning really militates against poor people because 

they won’t have air conditioning at all often or can’t afford the utilities, and so they bear the brunt of climate change in a larger, 

greater way than wealthy people in a climate change burden. 

Dr. KOPP. Yes, and so generally what you find is that the poor 

suffer and the rich can spend to adapt, so they both bear costs, but 

in some cases it’s more personal costs, suffering, and the other is 

more monetary. 

Mr. COHEN. And somebody mentioned—which I pretty much understand, if we correct certain issues here and improve our—reduce 

our reduction—production of CO2, that you—if it doesn’t happen in 

the rest of the world, we’ve still got problems, but isn’t the best 

way to do that the Paris climate accords or some climate accords? 

Does anybody disagree with the fact that we ought to a climate 

treaty where we come together and have an accord? We’re all in 

agreement on that? Kumbaya. Thank you, and I yield back. 

Mrs. FLETCHER. Thank you. The Chair will now recognize Mr. 

Cloud for 5 minutes. 
141 

Mr. CLOUD. Thank you, Madam Chair. And may I again wish 

you happy birthday. Thank you all for being here. Mr. Majkut, at 

the beginning of your written testimony, you say that ‘‘There’s no 

better innovative force than the private sector, but if you really 

want energy innovation, you need to show innovators that there’s 

a market waiting for them.’’ Can you speak to what recommendations you would encourage for energy innovation in the market? 

Dr. MAJKUT. Sure. I think a lot of things are already in place 

showing energy innovators that there is market access for them. 

The Paris climate agreement is a great example, right? A lot of 

countries are saying they want to reduce greenhouse gas emissions, 

and that incentivizes people to innovate ways of doing it. 

Speaking of more at a U.S. national level, I think there’s a lot 

of things that could be done on the fiscal side, whether that’s a carbon price or smarter regulations than we have today to create a 

competitive marketplace. There are intermediate steps that can be 

taken when things aren’t quite ready to scale into the market. A 

good example of that would be the 45Q tax credits that are presently offered for producers—or people who capture carbon and sequester it or use it in some manner at new facilities. That gets you 

your first few. And then on the backend there is the scientific and 

engineering enterprise, which reduces the cost of doing all of this. 

Mr. CLOUD. Thank you. I hail from Texas, specifically the 27th 

District of Texas. It’s Gulf Coast. My district includes nuclear 

power. We had the number-one energy-exporting port in the Nation. We have wind energy. We have LNG, crude exports, very diverse as far as an energy portfolio is concerned. Texas is a leader 

in that, also a leader in wind energy and just having generally 

speaking a diverse portfolio. The Green New Deal, however, seeks 

to limit that to specifically noncarbon-produced energy in the next 

10 years. Is that feasible without crippling innovation and economy, or do you think that with new technologies, fossil fuels could 

play a part going forward? 

Dr. MAJKUT. Two things. One, I’m not a big fan of timetables 

generally. I think we know enough that we should be trying to 

bring low-carbon technology to market. Setting super ambitious 

goals—I understand the impulse. I totally agree, but I think you 

can get in your own way. And where we find ourselves today, that’s 

a very ambitious goal for where we’ve been. 

I think the climate doesn’t particularly care where energy comes 

from so long as it’s not emitting CO2, and that means that there 

are a lot of reasons why you’d want to pursue a diverse innovation 

portfolio. 

Mr. CLOUD. You say that climate doesn’t necessarily care where 

emissions come from. In a sense, too, the market doesn’t care 

where the energy source comes from, and the appetite globally for 

energy is growing. And it seems like one can make the case in a 

sense that we’ve now become the leading exporter of energy to the 

world, which is in essence creating stability in the world. People 

are able to buy energy from us instead of countries that hate us. 

U.S. companies generally also are more likely to care about being 

good stewards of creation so to speak than other energy-producing 

nations. Could the case be made that this continued progress in 
142 

this sort of realm would actually have more of a beneficial environmental effect going down the line? 

Dr. MAJKUT. Yes, if I interpret you correctly, I think so. Generally, U.S. practices are at the higher end on lots of environmental 

compliance issues. It also means freely available low-carbon energy 

is the thing that’s going to power the 21st century and make everybody better off. 

Mr. CLOUD. And could you also speak to how important a thriving economy is to creating innovative solutions? 

Dr. MAJKUT. It’s totally essential. What we seek in the Niskanen 

Center, what I think is best for this issue is an economy that’s 

flexible to new information, that provides routes for people to finance new projects and find profits where they can make them and 

then generally we want those—as long as those are low-carbon options, everybody is better off. That’s exactly what we’re looking to 

achieve. 

Mr. CLOUD. Thank you. I yield my 4 seconds back. 

Mrs. FLETCHER. Thank you. The Chair will now recognize Mr. 

Casten for 5 minutes. 

Mr. CASTEN. Thank you. Look, there is—there is no greater 

threat to our economic well-being, our national security, and even 

our survival as a species than climate change, and I want to thank 

Chair Bernice Johnson for taking it seriously, making it a priority 

of this Committee meeting, and I want to thank all of our guests 

today for your implicit acknowledgment that while we have the authority in this room to debate and ultimately change the laws of 

the United States, we have no such authority when it comes to the 

laws of thermodynamics, so thank you. 

I’d like to address my first question to Dr. Francis. We—I represent the 6th District of Illinois. We recently experienced a rather 

extreme cold snap. And as I think you know and we appreciate, 

these extreme low temperatures have in fact been attributed 

counterintuitively to warming in the Arctic that disrupts the jet 

stream. And yet we have a President who seems to think that a 

cold snap in one location disproves global warming. Could you 

please educate us on how global warming in aggregate can lead to 

periodic polar vortex events in the United States? 

Dr. FRANCIS. Yes, thank you very much. It’s not a simple story, 

and it’s an emerging science research question, although the 

science has been progressing very rapidly in this particular connection between what’s happening in the far north with weather patterns more generally and particularly with these extreme cold 

events in the winter. And what we’re learning is that there’s a region in the Arctic just north of western Russia where sea ice has 

been disappearing probably faster than anywhere else. And that 

particular location is special in the sense that when we lose ice in 

that area, it absorbs a lot of extra heat from the sun, which then 

gets returned to the atmosphere, and tends to create a pattern in 

the jet stream that can then influence the true polar vortex, which 

is much higher up in the atmosphere. 

When these conditions all align, it can topple if you will the polar 

vortex, which is a spinning river of air around this pool of cold air 

that sits over the Arctic in the wintertime. And when it’s a powerful enough punch to that polar vortex, it can cause it to deform or 
143 

even split into different circulations, and that’s exactly what happened this past winter that brought you a new record cold temperature for Illinois. One of these pools of cold air from the Arctic drifted down over North America and reinforced the cold air that’s already there during the wintertime. So this connection back to sea 

ice loss is the climate-change connection because that sea ice is disappearing because of global warming. 

Mr. CASTEN. Thank you. While Illinois has seen an increase in 

extremely cold weather, we’re also seeing an increase in extreme 

heat events. We saw it back in 1995 with the great heat wave in 

Chicago. A lot of the focus has been on urban impacts. There was 

a recent 2017 study in Environmental Health that analyzed heat 

waves in Illinois and found that there were actually significantly 

higher increases in hospitalizations per capita in rural areas. 

And with the consent of the Chair, I’d like to ask unanimous consent to enter this study into the record. 

Mrs. FLETCHER. Without objection. 

Mr. CASTEN. Thank you. The—my next question is for Dr. 

Mahowald. The cost of climate—of inaction on climate change is 

high, but over the last two decades we’ve seen cost of renewable 

technologies fall, lots more opportunities for energy efficiency, and 

at least some initial decoupling of economic growth from CO2 emissions. This is frankly not that surprising to me. I don’t think—nor 

to the business community because I think we all recognize that 

when we buy less fossil fuel, we actually save money and we have 

a little bit more money in our pocket, notwithstanding some earlier 

conversations about air-conditioner economics. If you invest a little 

bit more capital today to save a lot of money later, that’s a good 

thing. 

Dr. Mahowald, you had mentioned in your testimony that limiting warming can in fact go hand-in-hand with increasing economic prosperity, which I hope means that you agree with the 

points that I just made. I would welcome your thoughts on some 

of the policy changes you would encourage us to take up that would 

both lower CO2 emissions and incentivize more investment in the 

United States and economic growth. 

Dr. MAHOWALD. Well, thank you for the question. I want to be 

honest here. I’m actually a physical science expert, but I will talk 

a little bit about what the special report 1.5 has to say on the 

issue. The important thing that we looked at in this report is 

where one can cut emissions in the most economic way that also 

has benefits locally, for example, on air quality or ways that you 

can change people’s behavior that makes them healthier, as well as 

address this climate change. For example, if Americans and Europeans actually ate the amount of meat and dairy that their doctors 

recommended they do, they would be healthier. In addition, this 

would cut emissions of greenhouse gases. So there are a lot of ways 

that you would save money because you’re healthier, humans 

would be better off, Americans and Europeans would be better off 

and always, less hospital visits, feel healthier, and at the same 

time we’re trying to address climate change. So there’s quite a bit 

in the report where there’s benefits from climate mitigation that we 

can feel right now. 
144 

In addition, the—just the switch in some policies would make it 

easier for businesses in these innovative new sectors to have a stable business environment. And what’s happening in the United 

States now is the fragmentation a little bit. Some States are more 

aggressive than others. And so at the Federal level it would help 

trade within the United States if there was a little more leveling 

of the terrain. 

But overall, there are a multitude of policies and techniques and 

technologies that are proposed in this special report 1.5 that each 

individual State and local government, as well as the Federal Government, should evaluate that can make it so that it’s economically 

beneficial to address climate change. Thank you. 

Mr. CASTEN. Thank you. And I yield back my negative 1 minute, 

30 seconds of time. 

Mrs. FLETCHER. Thank you. The Chair will now recognize Mr. 

McAdams for 5 minutes. Oh, I’m sorry. 

Mr. MCADAMS. Thank you. 

Mrs. FLETCHER. I’m sorry, Mr. McAdams. 

Mr. MCADAMS. Yes. 

Mrs. FLETCHER. I didn’t see you, Mr. Marshall. 

Mr. MCADAMS. OK. 

Mrs. FLETCHER. I didn’t see that you were sitting—hadn’t gone. 

I’m sorry. The Chair will now recognize Mr. Marshall for 5 minutes 

and then Mr. McAdams. 

Mr. MARSHALL. OK. Thank you, Madam Chairwoman. Let me 

make my first official words as Ranking Member to wish you a 

happy birthday as well. And I’m looking beside me here—I was 

going to ask all the Members to join me in singing happy birthday 

so the people in the audience are going to have to help me here, 

Lizzie, OK? Happy birthday to you, happy birthday to you, happy 

birthday, dear Lizzie, happy birthday to you. 

Mrs. FLETCHER. Thank you very much. 

Mr. MARSHALL. You’re welcome. 

Mrs. FLETCHER. Your 5 minutes can begin now. 

Mr. MARSHALL. OK. All right. Well, I want to just take a second 

and focus on innovation. I’m a physician. I think innovation has 

done more to improve healthcare probably than anything I can 

think of. It has the potential to drive the cost of healthcare down 

more than any legislation that we can write up here. And I think 

of some of the great learning institutions, research institutions in 

Kansas, Kansas State University, Kansas University, Wichita 

State University. 

So, Dr. Majkut, let me ask you. If I’m going to go back, I’m going 

to be visiting with my leaders in those universities, what would 

you be telling them to think about for innovation, for research, and 

where do you see us going? Just give you some free rope here and 

chat a little bit. 

Dr. MAJKUT. I’m sure I would have a lot of ideas to share with 

them. I think we have a good grapple on the nature of this issue, 

and we have a good sense of what it is that we still need, right? 

Renewable energy is—we talked a little bit about today. It’s doing 

well. It’s market-competitive in a lot of cases, but it’s intermittent, 

right, not just because like the sun doesn’t shine at night, but 
145 

sometimes, over the space of months or years, you’re going to get 

different weather patterns, and that’s going to affect things. 

So really what we need to think about are what are the characteristics in energy sources that we want going forward that we 

don’t already have? So that might be easily dispatchable, very resilient, low-carbon energy sources, for example. Identify those, understand where you can find the most scale, both here in the United 

States and internationally, and pursue them with speed and vigor. 

Mr. MARSHALL. OK. I think about innovation across the country, 

fracking, some of those types of things are opportunities, carbon 

capture. Would you suggest us developing innovation here to help 

other countries? Do you think we should just send money to other 

countries to help them do things? 

Dr. MAJKUT. I think we should focus on innovation. All of our 

policies should be—at least as a side benefit, incentivize people to 

innovate new ways of doing things because what we really want is 

for people to do a lot more globally while emitting a lot less, and 

that’s an innovation challenge primarily. 

Mr. MARSHALL. OK. What’s the coolest innovation thing out 

there that we haven’t talked about today? 

Dr. MAJKUT. Oh, that’s interesting. Energy storage, the idea that 

we can find lots of interesting ways either through mechanical or 

chemical means to store a lot of energy is a very, I think, an interesting thing. My favorite example is very large flywheels like you 

have in the clutch of your car. You can, when you have excess energy, spin them up and when you need to take energy out of the 

storage system, you generate it from this massive spinning wheel. 

Mr. MARSHALL. OK. 

Dr. MAJKUT. I don’t know that that’s being deployed, but it’s a 

great idea. 

Mr. MARSHALL. OK. Thank you so much. I yield back. 

Mrs. FLETCHER. Thank you. I’ll now recognize Mr. McAdams for 

5 minutes. 

Mr. MCADAMS. I was going to sing happy birthday to you. You 

beat me to it. 

Mr. MARSHALL. Oh. 

Mr. MCADAMS. Thank you, Madam Chair, and I’m happy to be 

here for this hearing and for putting climate science at the top of 

our Committee’s priorities for this Congress. I think it’s an important issue for the entire Congress and happy to see us taking it up 

here on the Science Committee as well. 

Thank you to our witnesses for your—providing your expert testimony and really enlightening this conversation. 

I’m excited to join this Committee and to have an opportunity to 

understand the latest in climate research and highlight its importance in shaping our policies that will result in clean air, better environmental health, and a clean-energy economy. 

As the former Mayor of Salt Lake County, a county in Utah that 

often sees schoolkids kept inside for recess because the air’s not 

safe to breathe. I have four kids myself and was shocked to learn 

that part of their common vocabulary is ‘‘it’s an air day,’’ meaning 

they have—they don’t play outside at recess. They come home 

bouncing off the walls because they’ve been kept inside all day. 
146 

I know how important it is that we address our winter inversions 

in Utah, our summer ozone pollution, but while climate change is 

certainly real and important to us as a—to our global—to us as a 

planet, it’s also very important locally and the impacts that we feel 

locally vary from place to place, but we see it locally even in Utah. 

I know how important and imperative it is for Utah families to 

apply sound science to the solutions that we seek. 

Utah remains the youngest State in the country, and numerous 

studies document the risk to pregnant mothers, to their newborns, 

and to those with respiratory problems such as asthma when 

they’re exposed to dirty air. We’ve long been aware of the harm to 

older adults with heart and lung ailments as well, even the likelihood of premature death. 

Utah is keenly aware of the economic costs of climate change as 

well. When the Wasatch Mountains are not visible due to smog, 

our ability to sell our region to—we’re a region where tourism is 

an important part of our economy. The ability to sell our region to 

a new lifestyle-oriented businesses, it’s greatly diminished. 

Utah has had its share of environmental issues as well, devastating environmental issues from last summer’s catastrophic 

wildfires to extended drought to the shortening of a ski season, 

first-world problems I recognize, but it does have an impact on us 

when snow melt comes late and melts early. We also—in a desert 

area, much of our watershed is captured and stored in the form of 

snowfall, and then as snow melts, we have reservoirs, but as we 

have less snowfall and more rainfall, the ways in which over the 

last couple of centuries we’ve adapted to living in a desert, will not 

be adequate as climate patterns change and will be expensive for 

us. We can adapt fortunately. Unlike some places, we can adapt, 

but it will be expensive to us locally. 

So I think Utahns support efforts to protect our air, to protect 

our water, to protect our quality of life that we experience in our 

Rocky Mountains, and in fact our early pioneer settlers in Utah understood that in an arid landscape water is life itself, and anything 

that threatens the climate threatens our ability to sustain life over 

the long-term. 

As elected leaders, we have the capacity and the responsibility 

to have fact-based discussions about the issues of climate and environmental protection, and it is critical to our Nation’s goals for environmental sustainability, for economic prosperity, and our national security. 

So I believe that hearings such as the one today shows that we 

are serious about protecting health and spurring innovation to address the challenges that we face to transition to a clean-energy 

economy, and I’m proud to be here and to be part of the solution. 

I’m looking forward to working with this Committee to advance 

solutions to our climate crisis and to jumpstart, as I’ve said, a 

clean-energy economy. 

So my questions—I guess I’m almost out of time, so my first 

question and it may be my only question is to Dr. Ebi. The Fourth 

National Climate Assessment explains how the health of vulnerable populations such as older adults and children will be disproportionately affected by climate change. What are investments 

in research, not only technology research but also research to the 
147 

health and other areas of research should we make to further identify, to mitigate, and maybe even remedy these risks? 

Dr. EBI. Thank you for the question. It is such an important 

issue. As I mentioned before, the total Federal investment in this 

area is really incredibly small. A review by the Office of Management and Budget several years ago said that the NIH (National Institutes of Health) budget in this area is less than 0.02 percent of 

the budget, and it’s likely fallen since then. CDC (Centers for Disease Control and Prevention) gets a little bit of money to work with 

communities. So what we’re seeing are communities who are disadvantaged and don’t have access to those who can help them. 

They don’t have access to the research. Very few Departments of 

Health have access to the kinds of tools that they need. And we’ve 

got enormous opportunities to build on the research enterprise to 

improve the health of Americans right now. And it would be excellent if that investment would take place so that that could start 

soon. 

Mr. MCADAMS. Thank you. Thank you, Madam Chair. 

Mrs. FLETCHER. Thank you. Next, we’ll hear from Ms. Hill for 5 

minutes. 

Ms. HILL. Thank you, Madam Chair. So to our guests I want to 

thank you so much for your testimony, and I apologize for jumping 

between hearings this morning. But I—based on what I’ve heard 

so far, my impression is that in this Congress we should focus on 

setting the stage and laying the groundwork for the next 20 to 30 

years of addressing this issue. I’m hearing that we should focus on 

research, on infrastructure, on regulation, on public and private 

partnerships, and on global partnerships and leadership. And I’m 

wondering from you if you can talk—this question is to all of you— 

about in each of those areas, what are just the biggest gaps in research where we need to prioritize, the highest priority when it 

comes to infrastructure as we’re working on an infrastructure package, the biggest concern or need when it comes to regulation, the 

most significant impact we can have in terms of corporate incentives related to the public-private partnerships, and when it comes 

to the role of foreign policy on global partnerships and leadership. 

I realize those are a lot of questions, but pick the area you want 

to focus on and then just give it to me. 

Dr. KOPP. So quickly to give everyone—everybody have some 

time, I agree with all of the things you raised. One thing I think 

we need to think about is that this is a multigenerational challenge, so as we make the investments today—and I’m going to talk 

about the research enterprise—we need to think about, well, how 

are we building the research enterprise to help us deal with the 

fact that this is a problem that’s not going away; it’s a chronic 

problem? And so I would argue we need to be investing in something comparable to the agricultural extension program in our 

country where we have networks of researchers deployed throughout the country who serve as bridges from the research community 

to the people on the ground and help build those partnerships and 

sustain them so that they’re not dependent upon a grant here or 

there or personality here or there but we’re really building the sustainable research infrastructure to build a link between science and 

people making adaptation and mitigation decisions on the ground. 
148 

Dr. FRANCIS. And maybe just a little more specifically more related to my field would be some research priorities perhaps that 

this country has fallen behind in my opinion in terms of model development for climate modeling, and I think this is one of our primary tools for understanding what our future holds based on different scenarios for the future. And also seasonal forecast models, 

so understanding how the climate change is going to affect weather 

patterns, so not so much what the weather’s going to be tomorrow 

but getting a bigger lead time in weather patterns that will affect 

agriculture, which we talked about earlier, and other aspects to infrastructure, that sort of thing. 

Dr. MAJKUT. I think on the advanced research side focusing on 

having a portfolio of options available. This problem looks a lot different today than it did 10 years ago. I think we can reasonably 

expect it’ll look pretty different 10 years from now. And we want 

to leave our future policymakers or when you’re all much senior— 

more senior, a lot of options on the table. I think that’s a really important thing because the scale of the change that will be needed 

to meet the goals in these reports is substantial, not impossible, 

but it’s substantial. 

Ms. HILL. Well, and I think for you in particular, Doctor, I was 

curious about your thoughts on the public-private partnerships and 

the corporate incentives that we might be able to put into place. 

Dr. MAJKUT. I personally—and as an institution we see a fairly 

limited role for public-private partnerships. Largely, I think we 

should be focusing more on market design and particularly we support carbon tax in lieu of regulatory approaches—— 

Ms. HILL. OK. 

Dr. MAJKUT [continuing]. Which we presently have. 

Ms. HILL. OK. 

Dr. EBI. I’ll add an issue that hasn’t been raised is multidisciplinary. We’ve talked about a whole range of risks of a changing 

climate. Those all interact. They don’t happen at once. They happen together. We’re seeing heat waves and wildfires. And so making sure that we have the partnerships not only with our stakeholders but across the scientific community, which requires different thinking about how we conduct our research and frankly 

then how universities are organized to do that research. And so 

there does need to be significant incentives to move from a disciplinary-based focus to a much broader focus of how we can collectively 

put together our wisdom, working with the knowledge from our 

stakeholders, to come up with the innovative solutions that we 

need. 

Ms. HILL. Thank you. 

Dr. MAHOWALD. If I can speak? 

Ms. HILL. OK. I can’t quite hear. Yes. I’m looking at the TV. I 

have no idea if you know that I’m talking to you. 

Dr. MAHOWALD. So I did see you, but thank you for the question. 

I just want to mention also the area of carbon dioxide removal, we 

not only need to be working on mitigation and adaptation but a 

new area of carbon dioxide removal, there’s a lot of potential in this 

area, and there’s very little research money being put into this so 

far from the Federal Government, for example, or from companies. 
149 

So this is a new area that could also be very beneficial for reducing 

climate risk in the future. Thank you. 

Ms. HILL. Thank you so much. Do any of you have anything to 

add in the last 30 seconds? Great. Thank you so much. I yield back. 

Mrs. FLETCHER. Thank you. The Chair will now recognize Mr. Lipinski for 5 minutes. 

Mr. LIPINSKI. Thank you, Madam Chair. I was just speaking at 

an Introduce a Girl to Engineering Day event, and I was saying we 

need everyone that we can get on board to work on the solutions 

to the big problems that we face. And I mentioned specifically climate change being one of these major problems that—where we’re 

going to need all of the work that—all the best minds and brightest 

to figure out how we move to a clean-energy economy. One thing 

I think that we can do a good job at is from the government side 

is putting more funding into ARPA-E (Advanced Research Projects 

Agency - Energy) to help move some of these—get some of these 

innovations developed, moved forward. 

But another thing that I have been supportive of—and 10 years 

ago I actually introduced the first bipartisan carbon fee bill that 

was introduced where all the money would go back to the public, 

a fully refunded carbon fee. So I want to ask Dr. Majkut, you just 

briefly mentioned it. Why do you think that that would be an especially good way to approach this issue? 

Dr. MAJKUT. Three reasons. The first is when you take a direct 

run at the problem, which is greenhouse gas emissions, you are 

hopefully finding the lowest-cost option. That way you’re not playing favorites, renewables versus carbon capture versus nuclear, and 

you’re not pre-committing to things. Rather, decisionmakers 

throughout the country, whether they are engineers at Exxon 

Mobil or utility executives, are making decisions to favor low-carbon options. And all their efforts add up relatively quickly. So 

there’s a strong cost-effectiveness and a strong efficacy argument 

there. 

The other reason is—or the second reason is that insofar as this 

is a question of how do we get affordable, reliable, low-carbon energy out at scale, mechanisms like carbon pricing are the easiest 

way to achieve scale incentives for all those decisionmakers I just 

mentioned. 

And the third is I think importantly the signal that comes from 

there being congressional intent on climate change for problems of 

these timescales, decades, is very important. It provides a lot of 

certainty for economic firms out in the world both here and abroad 

that the United States is moving in a particular direction. In the 

environment we have now, we don’t have that. 

Mr. LIPINSKI. Thank you. Some of the questions have focused on, 

well, what are going to be the negative economic consequences from 

doing something on climate change. I want to focus from a scientific standpoint on what are the consequences to the U.S. economy that—if we fail to address this and slow the rise of greenhouse 

gases. What do you think—what would you worry about the most? 

So who wants to start? Mr. Kopp? 

Dr. KOPP. Sure. Thank you. So we actually had a paper out on 

that a couple years ago, and we looked at several different types 

of impacts. The two that floated to the top were both public health 
150 

impacts, so the effects on mortality and the effects on the ability 

of people to work outdoors. Both have quite large economic impacts. We also see economic impacts associated with the stresses 

that warmer temperatures put on the energy system. We see economic impacts from the damages that storms cause to the coast. 

We see economic impacts from the effects of warmer temperatures 

on agriculture. And those are just the sort of sectors where we can 

sort of look at past behavior and say something about the future. 

We also have a fair bit of concern about the things that we haven’t 

observed yet in the past that might cause risk. So when we start 

having more extreme events happening simultaneously, that’s a potentially large impact that’s harder to assess. 

Mr. LIPINSKI. Thank you. Who—anyone else want to add anything? Dr. Francis? 

Dr. FRANCIS. So just to follow up with—on that a little bit, we 

know that in 2018 the losses due to extreme weather were roughly 

$160 billion just to the United States, and the year before, 2017, 

they were up around $300 billion, so we’re not talking about small 

numbers here. 

But I think what keeps me up at night is thinking about my own 

daughter and the world that she’s going to face if we do nothing, 

and it—for me the scariest thing is thinking about the security 

issues overseas and how people are going to be more miserable and 

therefore more unhappy, and we’re going to be dealing with a lot 

more migration and wars that are the result of people just being 

very unhappy in their situation. 

Mr. LIPINSKI. That’s very sobering, but I think it’s a good way 

to end on that concern as we work on moving forward to solve this. 

And I yield back. Thank you. 

Mrs. FLETCHER. Thank you. 

Before we bring the hearing to a close, I want to thank our witnesses for being here today and testifying before the Committee. 

The record will remain open for 2 weeks for additional statements for the Members and for any additional questions the Committee may want to ask of the witnesses. 

The witnesses are excused, and the hearing is now adjourned. 

[Whereupon, at 12:48 p.m., the Committee was adjourned.] 
(151) 

Appendix I 

ANSWERS TO POST-HEARING QUESTIONS
152 

ANSWERS TO POST-HEARING QUESTIONS

Responses by Dr. Robert Kopp 
153 

when building infrastructure that is vulnerable to it. Such flexible adaptation pathways are 

already encouraged by some states and cities, such as California and New York City. 1 

The 2014 report of the President's State, local, and Tribal Leaders Task Force on Climate 

Preparedness and Resilience made a variety of recommendations regarding infrastructure that 

are worthy of consideration. 2 These include: 

Requiring consideration of climate-related risks and vulnerabilities as part of all 

Federal investments; 

Maximizing opportunities to take actions that have dual-benefits of increasing 

community resilience and reducing greenhouse gas emissions; 

Promoting and prioritizing the use of green and natural infrastructure ; 

Supporting and incentivizing climate resilient water resource planning and 

management; and 

Assisting transportation officials in better understanding the vulnerabilities and risks 

to transportation networks and facilities and integrate climate resilience planning 

and preparedness criteria throughout existing Federal transportation funding 

programs. 

More generally, as we assess the state of our nation's infrastructure, it's important that we 

evaluate not just whether it is in good repair, but whether it is in a state of good resilience. 

Repairing infrastructure to a state designed for climate conditions of the past is an inadequate 

approach, given that those conditions are now behind us. 

In addition, it is important that climate-related infrastructure decisions take into account the 

benefits of avoided greenhouse gas emissions. Under the Obama Administration, interagency 

estimates of the social cost of greenhouse gases provided a uniform, scientifically grounded 

approach to incorporating the costs of greenhouse gas emissions (and the benefits of their 

reductions) into regulatory decision-making. Toward the end of the Obama Administration, 

their use was being broadened to a variety of other planning and investment decisions. 

Reinstating and expanding their consistent use- and investing in the underlying scientific and 

economic research -can help ensure that such decisions are based upon an economically 

sound approach.3 

2. I appreciated that you discussed national security as a major area under threat of 

climate change, Dr. Kopp. Can you elaborate on the impact that climate change will 

1 NEW YORK CITY MAYOR'S OFFICE OF RECOVERY AND RESILIENCE, CliMATE RESILIENCY DESIGN GUIDELINES (2018), 

https://www1.nyc.gov/assets/orr/pdf/NYC_Ciimate_Resiliency_Design_Guidelines_v2-0.pdf; CALIFORNIA OcEAN 

PROTECTION COUNCIL & CAliFORNIA NATURAl RESOURCES AGENCY, STATE OF CALIFORNIA SEA-lEVEl RISE GUIDANCE: 2018 UPDATE 

(2018), http:/ /www.opc.ca.gov/climate-change/updating-californias-sea-level-rise-guidance/. 2 PRESIDENT'S STATE, LOCAL AND TRIBAl lEADERS TASK FORCE ON CliMATE PREPAREDNESS AND RESiliENCE, RECOMMENDATIONS TO 

THE PRESIDENT ( 2014 ), https:/ /oba mawhitehouse.archives.gov I sites/ default/files/docs/task _force _report_ O.pdf. 3 See NATIONAl ACADEMIES OF SCIENCES, ENGINEERING, AND MEDICINE, VALUING CLIMATE DAMAGES: UPDATING ESTIMATION OF THE 

SOCIAl COST OF CARSON DIOXIDE (2017) for an in-depth diSCUSSion. 

2 
154 

have on our nation's warfighters and its contribution to increased national security 

threats? 

The Fourth National Climate Assessment4 identifies several ways in which climate change will 

impact U.S. security interests. 

Climate change has already led to increases in extreme weather, and these increases will 

continue with further change. For example, sea-level rise is already enhancing the flooding 

associated with hurricanes, and climate change is projected to increase their wind intensity. 

Climate change is also already increasing the amount of rain falling in intense events, and thus 

the associated rain-driven flooding. Climate change is also increasing drought risk in some 

regions. 

As the National Climate Assessment notes, "Developing countries are often highly vulnerable to 

climate extremes, which can set back development and increase the need for disaster response 

and recovery assistance."5 The Department of Defense is often a key participant in post-disaster 

response efforts around the globe. 

While the direct effect of climate extremes on conflict risk remains a contested topic of 

research, it is clear that the effects of chronic development reversals can increase the risk of 

civil conflicts, which may affect US security interests.6 Climate change is also a potential driver 

of increased migration. As the NCA notes: 

Extreme weather events can in some cases result in population displacement... 

[T]ropical cyclones are projected to increase in intensity, which would increase the risk 

of forced migration. Slower changes, including sea level rise and reduced agricultural 

productivity related to changes in temperature and precipitation patterns, could also 

affect migration patterns. However, whether migration in response to climate change 

will generally cause or exacerbate violent conflict is still uncertain.7 

Department of Defense assets are also exposed to the effects of climate change; as the 

National Climate Assessment notes, "Climate change is already affecting U.S. Department of 

Defense (DoD) assets by, among other impacts, damaging roads, runways, and waterfront 

infrastructure."8 US Coast Guard assets are similarly exposed. 

4 J. B. Smith et al., Climate Effects on U.S. lnternationa/lnterests, in IMPACTS, RISKS, AND ADAPTATION IN THE UNITED 

STATES: FOURTH NATIONAL CLIMATE ASSESSMENT, VOLUME II 604-637 (C. W. Avery et aJ. eds., 2018), doi: 

10.7930/NCA4.2018.CH16. 

5 /d. at 610. 6 SOLOMON M. HSIANG & AMIR S. )INA, THE CAUSAL EFFECT OF ENVIRONMENTAL CATASTROPHE ON LONG-RUN ECONOMIC GROWTH: 

EVIDENCE FROM 6,700 CYCLONES (2014), http://www.nber.org/papers/w20352 (last visited Apr 30, 2018); Solomon M. 

Hsiang, Marshall Burke & Edward Miguel, Quantifying the influence of climate on human conflict, 341 SCIENCE 

(2013), http:/ /science.sciencemag.org/sci/341/6151/1235367.full.pdf; Havard Hegre et al., Forecasting civil conflict 

along the shared socioeconomic pathways, 11 ENVIRON. RES. LETT. 054002 (2016). 7 Smith et al., supra note 4 at 613. 

'ld. at 613. 

3 
155 

Domestic DoD bases are not isolated from their surrounding communities. Thus, it is important 

that DoD consider climate impacts not only directly on its own facilities, but also on the 

communities surrounding their installations that support base functioning. My colleagues at 

Rutgers have been involved in one such integrated study, the Joint land Use Study for Naval 

Weapons Station Earle. 9 

3. New Jersey has set a state standard to reach one hundred percent clean energy by 

2050. Yet, we to address climate change through achievable goals and by setting 

national standards. 

Dr. Kopp, you and your team at Rutgers, the State University of New Jersey, including 

Jennifer Francis, also on the panel, are doing excellent work on climate science given the 

resources the federal government has made available for this science. What sort of 

investments in the climate science enterprise could help make climate science more 

actionable and bridge the gap between the research and implementing a national 

energy plan? 

An actionable climate science enterprise requires a significant focus on what is sometimes 

called 'transdisciplinary' science. 10 Transdisciplinary science brings researchers from different 

disciplines together with stakeholders to tackle a common real-world problem. 

Transdisciplinary science is not necessarily applied research, as it may aim not only to translate 

existing understanding into practice but also to address some of the fundamental scientific 

uncertainties relevant to effective risk management. The tie to real-world problems is, 

however, a core element. 

Climate risk management- both on the mitigation and adaptation sides calls out for such 

transdisciplinary research, as well as for educational initiatives preparing students to conduct 

such research. At Rutgers, we have a number of such efforts. For example, our Coastal Climate 

Risk and Resilience program11 trains graduate students to work with natural scientists, social 

scientists, engineers, urban planners, and stakeholders to manage coastal risk. The New Jersey 

Climate Change Alliance12 is a University-managed network of stakeholders that links scientific 

experts with local, state, and private decision-makers. We are a partner in the Climate Impact 

lab, which is bringing climate scientists, economists, and data scientists together with 

stakeholders in state governments and the private sector to better integrate economic 

assessments of climate risk into regulatory and investment decisions. And we are working with 

the state to help build a New Jersey Wind Institute, which should bring a transdisciplinary 

approach to science and engineering related to off-shore wind energy. 

9 See https://www.visitmonmouth.com/page.aspx?ID=4782. 10 Gertrude Hirsch Hadorn et al., The Emergence of Transdisciplinarity as a Form of Research, in HANDBOOK OF 

TRANSDISCIPLINARY RESEARCH 19-39 (Gertrude Hirsch Hadorn et al. eds., 2008). 11 For more information: c2r2.rutgers.edu 12 For more information: njadapt.rutgers.edu 

4 
156 

But true transdisciplinarity is hard- it requires a considerable investment on the part of 

researchers or their institutions in maintaining strong, working, trusting relationships with 

stakeholders. And building such relationships takes time- if it must be done from scratch, it 

does not fit well with the time pressures faced by pre-tenure faculty or graduate students. 

Right now, in the climate risk area, most transdisciplinary collaborations are driven by strong 

personalities or short-term funding opportunities. But the climate risk problem is not going to 

go away. Society is not well served if the networks that sustain such collaborations have to be 

rebuilt when individuals leave an institution or funding temporarily dries up. 

Fortunately, there is an example of academic institutions supporting transdisciplinary 

collaborations that has worked in the United States for over a century, long before the modern 

jargon of 'transdisciplinarity' was coined. 

In 1862, amidst the bloodshed of the Civil War, Abraham lincoln signed the Morrill Act, 

establishing the United States' land-grant college system. The Morrill Act and follow-on 

legislation transformed higher education in the United States. They established a network of 

universities devoted to training the next generation of farmers and engineers, conducting 

innovative and useful research to advance agriculture, and engaging with farmers to 

disseminate the fruits of this research. The Smith-Lever Act of 1914 established cooperative 

extension services at land-grant institutions with the aim of bringing scientific knowledge about 

agriculture out of the universities and into the country. The cooperative extension services have 

placed agents in every US county and built networks of trust that link the land-grant institutions 

to the (primarily agricultural} community. 

It is worth considering an investment analogous to that of cooperative extension in expanding 

the infrastructure for scientific climate risk management. The unique advantage of land-grant 

universities is the extension tradition, upon which can be built robust networks to sustain 

stakeholder engagement in climate risk research and education. This requires support to shift 

the maintenance of stakeholder networks away from individual investigators and grants and to 

the institution. 

Building upon the extension strength also requires addressing countervailing incentives at the 

level of the individual scientist. Transdisciplinary research is inherently slower than more ivorytower research, requiring that researchers invest time in stakeholder engagement. More 

flexible tenure evaluation processes that recognize the value of this engagement can help 

advance this mission, and this shift would be assisted by appropriate nudges from funding 

agencies. 

5 
157 

Responses by Dr. Jennifer Francis 

WOODS HOLE RESEARCH CENTER 

Dr. Francis Responses to additional Questions for the Record 

1) You state in your testimony how extreme weather events have nearly tripled globally 

since the 1980s. You discuss the research that underlies this phenomenon, such as how global 

temperature rise is making heat waves more intense, and warmer oceans and air increases 

evaporation and thus heavy precipitation. In addition to the processes that we understand with 

high certainty, you pinpoint some of the emerging frontiers in this research such as uncovering 

complex interactions between the warming Arctic and the rest of the ocean and atmospheric 

system. 

a. Given that there are a number of frontiers in climate science that need more research to 

understand how the climate system is changing and will continue to change, which additional 

research needs related to climate science should be prioritized by federal funding? 

In my opinion, the following areas of research related to climate science should be prioritized for 

federal funding: 

• Identification and characterization of critical thresholds and tipping points in the climate 

system, beyond which reversal is most likely impossible. Policies should be designed to 

avoid crossing them. Thresholds may exist in both the physical climate system (e.g., amount 

of ice-sheet loss tolerable before runaway melting occurs, weakening of the capping surface 

layer in the Arctic Ocean that prevents warm Atlantic water from coming into contact with 

sea ice) and in ecosystems (e.g., minimum population of a species before extinction). The 

National Academies of Sciences report Abrupt Impacts of Climate Change (2013) is an 

excellent resource for this topic: https://www.nap.edu/catalog/18373/abrupt-impacts-ofclimate-change-anticipating-surprises 

• Proactive and reactive adaptation to climate-change impacts. As the climate changes, we 

will be forced to adapt one way or another. We have a choice: 

o Research to inform proactive responses- Based on climate projections at local/state 

levels, develop strategies to prepare for gradual change (e.g., sea-level rise, overall 

warming) and increasingly disruptive extreme events. Strategies should include 

making infrastructure more resilient (move or reinforce it). designing disaster plans 

to address future (not past) event likelihoods, reviewing building permit criteria to 

disallow construction in vulnerable locations, and promoting public education 

programs to alert residents to dangers and emergency plans. Proactive adaptation 

will save lives and money. 

149 Woods Hole Road· J:<almou!h, ;VIA 02540-1644 USA 

Telephone 508.540.9900 -Fax 508.540-9700 -wlmcor:g 
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WOODS HOLE RESEARCH CENTER 

o Research to inform reactive response- Smart adaptation strategies will not be able 

to prepare society for all extreme events, so more efficient and thoughtful 

emergency response plans- guided by up-to-date impact projections- are required. 

Reactive approaches alone will result in higher casualties, greater property and 

infrastructure damage, and longer societal disruption. Research is needed to refine 

projections of extreme events, economic impacts, evacuation plans, and rebuildversus-retreat strategies. 

• Attribution science- assessing contribution of climate change to exacerbating extreme 

weather events. Research should be supported that addresses these questions: 

o Is climate change making this type of extreme event more likely? If so, where and 

under what conditions? 

o What role did climate change play in making a particular extreme event more or less 

severe? 

o How should federal/state/local policies adapt to prepare for expected increases in 

extreme events? (proactive approach) 

o How should federal/state/local policies be revised to guide recovery efforts after 

extreme events that occur repetitively in an area? Should neighborhoods, 

businesses, and public infrastructure be rebuilt, or should alternative locations be 

sought (retreat)? When does it become unfair to taxpayers to have federal relief aid 

spent on rebuilding homes/businesses/infrastructure in disaster-prone areas, 

particularly private residences? 

• Observations- weather, ocean, ecosystems. Sustained measurements are critical to 

preparedness. 

o Maintain and expand satellite observation network. This is absolutely critical for 

weather prediction, climate science, and basic geophysical science. 

o Conventional observations systems (e.g., weather stations, ocean buoys, long-term 

ecosystem monitoring instruments) must be maintained because satellite-based 

measurements need to be calibrated and remote sensing cannot observe all needed 

variables. 

o Observations are key to change detection, early warning, and understanding 

complex interactions within the climate system. 

• Social science- turning the tide on anti-science and promulgation of fake news. Research is 

needed to: 

1~9 Woodr Hole &ad· Falmouth, MA 02540-16# USA 

Telephone 508.540.9900 ·Fax 508.540-9700 · whrc.org 
159 

• . 

. 

WOODS HOLE RESEARCH CENTER 

o Understand why Americans have become more anti-science and how to reverse this 

trend. 

o Target education that will equip citizens with tools to detect misinformation and 

malicious/manipulative information sources 

b. What are the largest uncertainties in projecting future climate change and its impacts? 

Regarding projections for the future climate, the largest sources of uncertainty are: 

• the pace of ice-sheet melt: affects speed of sea-level rise 

• changes in cloud properties: affects sensitivity of global warming to increasing 

greenhouse gases. Current research suggests that cloud changes are likely to 

exacerbate global warming 

• complex responses of marine and terrestrial ecosystems: affects food security and 

health of natural systems 

• technological breakthroughs: types and pace of advances in technology affect 

carbon emissions, adaptation strategies, and disaster recovery 

• human behavior: responses to extreme events, food shortages, and lack of access to 

fresh water will affect stability of governments and our own national security. 

Acceptance of mitigation strategies will determine future carbon emissions and 

pace of climate change. Adoption of proactive adaption strategies will lessen 

impacts of climate change. 

2) During the hearing, many Members brought up the importance of research and 

development for climate change mitigation and adaptation. 

a. In addition to technological methods, are there other ways that carbon can be removed 

from the atmosphere? How can the research enterprise better support the development of these 

methods? 

A variety of natural solutions exist that have many additional benefits beyond carbon 

sequestration: 

• planting more trees 

• eliminate forest clear-cutting 

149 Wood> Hole Rnad ·Falmouth, iHA 02540-1644 USA 

Telephone 508.540.9900 ·Fax 508.540-9700 · whn.org 
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WOODS HOLE RESEARCH CENTER 

• improving soil quality in farming areas 

• reducing greenhouse gas emissions by the agricultural sector (e.g., less wasteful use 

of fertilizers, alternative animal feed that reduces methane production, improved 

animal waste management, more efficient irrigation, smarter matching of crops to 

local climate). 

b. Which approaches to adaptation should be prioritized by federal funding? 

There is no single approach to adaptation that will solve the problem. In my view, the 

suggestions highlighted above are the highest priority approaches that should be supported 

with federal funding. Many others are also worthy of funding. 

c. Which economic tools can be brought to bear to reduce carbon emissions? 

• Discontinuing subsidies for fossil-fuel-related enterprises (such as exploration, 

drilling, pipelines, power plants, and distribution systems) while increasing incentives 

for the development of renewable energy sources could spur the development of 

low carbon electricity generation. 

o From 1950-2010, fossil fuels received $5948 in subsidies (80%), nuclear $73B 

(10%), and renewables $74B (10%)1. 

• Recent implementation of carbon fee systems has shown that well-designed policies 

can reduce carbon emissions and have positive economic influences in the short 

term. The Tuft University's Climate Policy lab4 is systematically studying real word 

climate policies-- how well they work, and their economic consequences. 

o British Columbia has had a carbon fee program since 2008. Carbon fees are 

added to fossil fuels burned for transportation, home heating, and electricity, 

while personal income taxes and corporate taxes are reduced by a roughly equal 

amount. The fee is collected at the point of retail consumption. During the first 

five years of the program, fossil fuel consumption dropped 17.4% per capita and 

the tax shift enabled BC to have one of Canada's lowest income tax rates2• In 

October 2018, Canada as a whole adopted a similar program3. 

o Revenue from carbon fee could be invested in proactive adaptation. 

1. http://www.misi-net.com /publications/NEI-1011.pdf 

2. https://en.wikipedja.org/wiki/British Columbia carbon tax 

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Telephone 508.540.9900 · Fax 508.540-9700 · whrc.otg 
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WOODS HOLE RESEARCH CENTER 

3. https://www.theguardian.com/environment/climate-consensus-97-percent/2018/oct/26/canada-passed-a-carbon-tax-that-will-give-most-canadians-moremoney 

https://sites.tufts.edu/cierp/research/climate-policy-lab/ 

Thank-you again for the opportunity to testify at your hearing. If I can be of any further assistance 

to your committee, please don't hesitate to ask. 

Sincerely, 

Jennifer Francis, PhD 

Senior Scientist 

Woods Hole Research Center 

149 ll7oodr Hole Road· I'a!mouth, 2\1A 02540-1644 USA 

Telephone '!08.540.9900 ·Fax 508.540-9700 · whrc.org 
162 

Responses by Dr. Joseph Majkut 

Joseph Majkut- QFR- The State of Climate Science and Why it Matters 

Responses to Mr. Posey 

Q1: We make adjustments to solutions and objectives as we learn -all of the time being 

guided by a balancing of the benefits and costs. We have limited resources and money, 

so we must apply the best alternatives. Is that a reasonable strategy for dealing with 

climate challenges considering uncertainty and limited resources? 

Yes. We should keep our policy approaches to climate and reducing emissions open to new 

information and be willing to make adjustments along the way.' Although this problem is urgent, 

it will take decades to change the energy system to reduce greenhouse gas emissions and 

forestall the worst case warmings. 

Even over the next decade, we will likely learn a lot. We may learn that the hazards posed by 

global warming are more severe or less severe than scientists presently expect. We may learn 

that it is easier to cut greenhouse gas emissions than we had thought. We may also learn that it 

is harder. We may learn that it is easier to do so with one technology over another, or we may 

invent something altogether new. 

In any of these cases, we want to be in a position to keep learning, updating our expectations, 

and adjusting our plans. As such, I would recommend maintaining a robust earth science 

enterprise to monitor the changing climate, an advanced research enterprise to keep pushing 

the boundaries on low-carbon technology, and a healthy and transparent market in energy 

services, so that consumers, businesses, and the public can find the lowest cost-or highest 

benefit-options. 

Q2: Do we know the timing and future intensity of climate phenomena like temperature 

and more importantly, can we accurately predict how a policy change will affect the 

outcome? Can we really predict how the future climate will change if we, for example, 

reduce emissions by a given amount or are we just guessing/taking a stab in the dark? 

I wouldn't say that we are completely guessing, but I would say that climate predictions are 

uncertain. What that means is that we cannot say what the global temperature will be in 30, 50, 

or 100 years with absolute precision. However, we are not shooting in the dark, especially when 

comparing different future scenarios. If we reduce global emissions quickly, then the climate at 

the end of the century will look fairly similar to the one we have now, with maybe another degree 

of warming. If global emissions continue to grow rapidly, then the climate in 2100 will look quite 

different, with several more degrees of warming. 

As I discussed in my testimony-and as highlighted in the reports from the IPCC and US 

GCRP-the extent of climate change is related to the total amount of C02 emitted. So every ton 

1 For a good description learning in the policy response to climate change, see The National Academies 

Report America's Climate Choices, Chapter 4: A Framework for Making America's Climate Choices, 

available online at https://www.nap.edu/read/12781/chapter/6 
163 

Joseph Majkut- QFR- The State of Climate Science and Why it Matters 

of C02 emitted can be assigned an increment of warming. Similarly, every non-emission of 

C02 will prevent an increment of warming. The timescales, however, are long because the 

earth system is a little slow to respond to changes in emissions, and changes in policy do not 

immediately change emissions. So the benefits of changing policy and reducing emissions play 

out over time. 

The science indicates that policy changes which would reduce global emissions would prevent 

noticeable temperature increases on timescales of a few decades. Meaning that when scientists 

compare scenarios with high emissions to scenarios with low emissions, the global 

temperatures are noticeably different in the latter part of the 21st century-even though the 

emissions rates are quite different within a decade from now. 

The table below is from the Intergovernmental Panel on Climate Change's 5th Assessment 

report.' Each row depicts the average warming and likely range of warming for a different 

scenario (the total human perturbation increases from RCP2.6 to RCP8.5). In observing the 

table, you see that the average warming between these scenarios starts to diverge in the 

mid-century, and strongly diverges by the end of the century. 

Table SPM.2J Projected change in gtobal ~an surface air temperature and global mean sea level rise for the mid~ and !ate 21st century relative to the 

reference penod of 1986·2005. :12.4; Table 12.2, Table 13.51 

2046-2065 2081-2100 

Scenario Mean Likely range' Mean Likely range' 

RCP2.6 1,0 0.4to 1.6 1.0 03 to 1.7 

Global Mean Surface RCP4.5 1.4 0.9to 2.0 1.8 Uto2,6 

Temperature Change (•q• RCP6.0 l.l O.Sto 1.8 2.2 1.4toll 

RCP8.5 2.0 1.4to2.6 3.7 2.6104.8 

Mean Likely range• Mean 

RCP2.6 0.24 0.17 to 0.32 0.40 

Global Mean Sea Level RCP4.5 0.26 O.i9to0.33 0.47 0.32to 0.63 

Rise(m)' RCP6.0 0.21 0.18 to 032 0.48 0.33to0.63 

RCP8.5 0.30 0.22 to0.3S 0.63 0.45 to0.82 

Q3: [On Solar Radiation Management or Geoengineering] Can you please elaborate on 

[geoengineering] in your testimony and share with the committee your recommendations 

for legislation in this regard, as well as the potential role for geoengineering? 

In November 2018, the Niskanen Center included immediate policy recommendations for 

supporting geoengineering research, which is an presently only obliquely supported by the 

2 IPCC Fifth Assessment Report https://www.ipcc.ch/assessment-reportlar5/ 
164 

Joseph Majkut- QFR- The State of Climate Science and Why it Matters 

federal government, in a report on emerging technologies.' I include here an excerpt from that 

report (italicized). 

Geoengineering technologies are one prospective means of addressing climate change. As a 

class of technologies, they could potentially allow people to intervene in the Earth system at a 

large enough scale to deliberately alter the climate and decouple the total amount of warming 

from total emissions of greenhouse gases due to burning fossil fuels. Technological 

interventions to reduce the human influence on climate fall into two categories: Carbon dioxide 

(C02) removal and solar radiation management (SRM). 

C02 removal, or negative emissions, describes technologies that would artificially remove C02 

from the atmosphere and thereby limit the warming and chemical effects of excess C02. These 

are interesting technologies for research that are already aligned with much of what is done at 

the Department of Energy (DOE) and other agencies. SRM refers to interventions that would 

decrease the amount of solar radiation that reaches the surface of the Earth by increasing the 

planet's reflectivity. While there are technical nuances and regional variances, the amount of 

cooling we could expect to see is roughly proportional to the decrease in radiation. These 

technologies could therefore be tuned to partially or fully offset the warming effects of increased 

C02 with a large enough intervention, while very small experiments would have no globally 

detectable signal. 

For SRM, the research agenda is more novel, and governance requirements more pressing, 

than C02 removal. Not all of the considerations that will govern decisions to use or refrain from 

using SRM technologies are scientific. However, numerous scientific and engineering gaps 

prevent an informed understanding of the costs and benefits of potential unintended 

consequences. Reducing uncertainties and better characterizing those risks presents the 

scientific enterprise with the opportunity to add value for future po/icymakers. The potential 

scale of climate risks and the costs associated with transitioning to a low-carbon economy mean 

that the potential value of SRM could register in the trillions of dollars. 

Supporting this research, and a reasonable governance agenda, may not require a lot of 

authorizing legislation. Yet Congress could exercise its oversight role, and the power of the 

purse, to dedicate federal resources to a safe and well-managed research program. 

To that end, our policy recommendations are as follows: 

1. Affirm the Office of Science and Technology Policy's role and authority in overseeing 

climate engineering research efforts; 

3 Joseph Majkut, Ryan Hagemann, Adam Wong Geoengineering Responses to Climate Change Require 

Enhanced Research, COnsideration of Societal Impacts, and Policy Development 

https://niskanencenter.org/wp-content/uploads/2017/1 0/Niskanen-Center-Comments-Ciimate-Engineering 

-AGU-2.pdf 
165 

Joseph Majkut- QFR- The State of Climate Science and Why it Matters 

2. Convene an ongoing multistakeholder process under the purview of USGCRP that will 

prioritize the creation of voluntary, consensus-based policy guidelines and 

recommendations for future research priorities; and 

3. Apportion dedicated federal funding for climate engineering research and development. 

Responses to Mr. Olsen 

Q1: Are you familiar with the Parish Plant? What advances have we seen in CCS in recent 

years? 

The Parish Plant is notable because it is, to my knowledge, the only functioning power plant in 

the United States that has been modified to use carbon capture and storage (CCS). With about 

190 million dollars• in financial support from the DOE, the plant's operators installed a unit to 

capture 90 percent of the C02 in the exhaust of one of the coal units. That captured C02 is 

subsequently being used to increase production in a nearby oil field. 

CCS has been piloted or demonstrated at a few plants like the Parish Plant, but it is not in wide 

use-nor is it regularly deployed on new natural gas or coal plants. The technology is still in its 

infancy. A 2018 report from the Global CCS lnstitute5 found that there are 23 large-scale CCS 

facilities in operation or under construction around the world, capturing almost 40 Mt of C02 per 

year, with an additional 28 pilot and demonstration scale facilities in operation or under 

construction. Although further deployment of CCS technology will probably help to bring down 

costs, as of now they remain too expensive to scale into today's commercial markets. 

Q2: [In reference to carbon removal technology] Could you talk about some of the 

technologies you have seen on this front? 

There are a number of different carbon removal strategies, each in different stages of 

development. Land management practices that store C02 in agricultural soils and forests have 

proven to work, and are ready to be deployed today. The strategies that rely more on 

technology-such as direct air capture, which removes C02 from the atmosphere and stores 

it-are either at the demonstration or pilot stages. There are additional technologies that are on 

the horizon, including enhanced weathering of rocks and the genetic modification of 

phytoplankton to increase their ability to sequester carbon. 

As the IPCC SR1.5 report makes plain, in order to limit warming to 1.5 C, processes that 

remove carbon from the atmosphere will need to be deployed at a scale removing up to Y. of 

today's global emissions per year. This is quite a staggering number, given that the technology 

• Peter Folger Carbon Capture and Sequestration (CCS) In the United States 

ht1ps://fas.org/sgp/crs/misc/R44902.pdf 

5 Global CCS Institute 2018 Global Status Report 

htlps://www.globalccsinstitute.com/resources/global-status-report/ 
166 

Joseph Majkut- QFR- The State a_[ Climate Science and Why it Matters 

is still in its infancy. Direct air capture could cost as much as $400-1000 per ton." These costs 

render this technology still too expensive to commercialize on the scale required to mitigate 

dangerous global warming. 

Q3: What is the best way to target investments in this kind of technology? 

There has to be value associated with removing C02 from the atmosphere and using it to do 

something-keep it out of the air, or in a durable and useful product. Advanced research can look 

for new ways to make C02 useful. If you want to consider just the task of keeping it out of the 

air, then Congress might consider increasing the incentives for businesses to innovate these 

technologies. 

This can be done through financial support mechanisms and tax credits, such as the 

recently-reformed 450 tax credit for the deployment of carbon capture and storage projects in 

the U.S. That program will credit companies that capture and store C02. But given the cost of 

direct capture (see previous response), it is not clear that those credits will actually lead to 

deployment of C02 removal facilities. It might be reasonable for Congress to look at prize 

models that would reward companies that are able to capture C02 at lower prices. 

Another policy incentive for expanding CCS and CDR technology would be to set a nation-wide 

price for carbon emissions. Carbon pricing, either through a carbon tax or a national 

cap-and-trade program, incentivizes emissions reductions and can be designed to credit carbon 

removal. 

Response to Mr. Baird 

Q1: [Referring to climate impacts on Indiana agriculture] What can we do right now to 

mitigate these effects, and what do we need to do for the future? 

The Fourth National Climate Assessmene predicts that increases in temperatures during the 

growing season in the Midwest are projected to be the largest contributing factor to declines in 

the productivity of U.S. agriculture. Mitigating these effects requires that we reduce greenhouse 

gas emissions across the United States. Economy-wide emissions reductions would require 

national, regional, state, and/or local policy to reduce the dangerous impacts of climate change. 

However, as mentioned in the testimony, climate change is a chronic condition and we must 

prioritize reducing societal vulnerability through adaptation. In the agricultural sector, producers 

can adapt to climate change through changing planting decisions, farming practices, and the 

use of specific technology that can reduce its negative impact on production. Making sure that 

6 National Research Council, Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration. 

https:/lwww.nap.edu/read/18805/chapter/4#38 

7 U.S. Global Change Research Program Fourth National Climate Assessment 

https://nca2018.globalchange.gov/ 
167 

Joseph Majkut- QFR- The State of Climate Science and Why it Matters 

farmers, their suppliers and insurers, and our research enterprise can work together easily and 

smoothly to share information and best practices will be helpful. 

Further research into making crops and farming practices will also be helpful. This could involve 

more research and investment in genetically modified organisms that produce crops that are 

tolerant to heat, drought, pests and diseases. Current assessments• of genetically engineered 

crops have demonstrated economic benefits for producers, with no substantial evidence that 

these technologies harm human or animal health. Expanding this and other adaptation 

measures requires investment in research and development of these technologies, so that 

future generations can readily adopt these techniques. 

8 National Academy of Sciences Genetically Engineered Crops: Experiences and Prospects 

https:l/www.nap.edu/catalog/23395/genetically-engineered-crops-experiences-and-prospects 
168 

Responses by Dr. Kristie L. Ebi 

Responses to questions from Committee Members 

1) In your testimony, you discuss how most policies to mitigate emissions of greenhouse gases 

have associated health benefits such as reduced air pollution, reduced temperature-related 

morbidity and mortality, fewer harmful algal blooms, and reduced insect-borne disease. 

a. Can you please expand upon what the current research tells us about the health cobenefits of climate mitigation scenarios? 

b. What is the state of research science modeling the co-benefits of mitigation policies? 

c. Can you expand on how research on health co-benefits can serve policymakers that 

aim to implement climate mitigation policies? 

d. How can policymakers better communicate this information? 

Thank you for the opportunity to clarify the health co-benefits of mitigation policies and 

technologies. 

a) Co-benefits represent selected near-term, positive impacts of mitigation policies that can offset 

some portion of mitigation costs. Co-benefits arise from policy actions and are distinct from the 

avoided negative impacts of climate change that the policy action would forestall. Co-benefits 

are common in the health sector because many prominent sources of greenhouse gas emissions 

are linked with environmental exposures harmful to people's health. In general, the current 

research on health co-benefits of climate change mitigation shows that mitigation comes close 

to paying for itself if health co-benefits are included in cost-benefit analyses. 

Health co-benefits are rarely estimated in economic assessments of the cost of implementing 

mitigation policies, such as those that could achieve greenhouse gas emissions reductions 

agreed to in the Paris Agreement. This is despite the fact that mitigation policies and 

technologies can benefit health by, for example, modifying exposures to air pollutants, changing 

physical activity patterns, and affecting dietary choices. Ignoring cost savings due to health 

impacts provides an unbalanced underestimate of the net impacts of mitigation activities and 

the associated net costs and benefits. 

The figure below summarizes the pathways for health co-benefits. The three panels show the 

conceptual framework linking climate mitigation and health outcomes via air quality (top panel). 

transport (middle panel), and diet (bottom panel) from Chang et al. 20171• 

1 Chang et al. 2017. Environmental Research Letters 12:113001. 
169 

Change to energy system 

1' Low GHG emisalons. healthy foods. 

(e.g.fruffs.vegetab!es.~gre!M) 

-!-Food wast& 

+ High GFG emission, unhealthy foods 

{eg. md and pro<:e$&$d meat. dairy) 

j .,I.Produc!lon,p:n~,transportation,~e. 

waste, of high GHG emlsslcm foods 

1'R~tionofrange!and 

l 

.J... PM emissions 

"-03 formation 

H .J,Saturatedfat 

-,l.Cholesterol 

1'Plant-basednutrltlon 

~-----~-&_~ __ ~_-_"'-~-M ____ __ 

+Cardiopulmonary disease 

.J... Respiratory disease 

.J... Lung cancer 

Two recent evaluations of health co-benefits studies reviewed the health co-benefits of 

mitigation policy scenarios targeted at multiple sectors and domains, including air quality, 

transportation, diet, agriculture, housing, industry, and economyY The review authors 

2 Gao et al. 2018. Science of the Total Environment 627:388-402. 
170 

concluded that implementing a range of mitigation policies results in significant local health 

benefits that can occur within a few years of policy implementation. In nearly all cases, the 

economic value of avoided premature deaths and hospitalizations offset a significant proportion 

of the costs of implementation of the mitigation policies; in some cases, the health co-benefits 

nearly covered the cost of implementation. The health gains could be further multiplied by 

comprehensive measures that include more than one sector. In many instances, implementing 

mitigation policies makes sense because of improvements to population health even without 

considering the benefits for achieving climate policy. Both of these publications are attached. 

Further, the US EPA led an extensive effort to estimate the health impacts and health-related 

costs by 2100 under Representative Concentration Pathway 4.5 and Representative 

Concentration Pathway 8.5 (different greenhouse gas emissions trajectories). The results are 

summarized in the Traceable Account for the Human Health chapter of the 4th U.S. National 

Climate Assessment; a copy is attached. This literature supported the Key Message: 

Reducing greenhouse gas emissions would benefit the health of Americans in the near 

and long term (high confidence). By the end of this century, thousands of American lives 

could be saved and hundreds af billions of dollars in health-related economic benefits 

gained each year under a pathway of lower greenhouse gas emissions {likely, medium 

confidence). 

b) There is a growing body of research estimating the health co-benefits of mitigation policies. A 

challenge with the literature is that most studies are more suited to describing the interaction of 

climate policy and health than providing specific, accurate estimates of health co-benefits. 

Greater consistency in modeling choices across studies would facilitate evaluation of mitigation 

options and promote the aggregate benefits. 

To facilitate this, a workshop convened 5-7 March 2019 by the Wellcome Trust, the University of 

Washington, and the World Health Organization developed a consensus among health cobenefits experts on modeling approaches and inputs such that study outputs can be compared 

and assessed. A guidance document is being developed to increase the consistency of health 

co-benefits models such that results are more comparable. The University of Washington Center 

for Health and the Global Environment also is updating the recent reviews of the health cobenefits of mitigation policies, focusing on air pollution, transport, and diet. 

As will be discussed in response to question 2 below, the lack of funding of health co-benefits 

modeling is limiting rapid advances in estimating health co-benefits at local to national scales. As 

opposed to other sectors, there are no centers of excellence with long-term funding to develop 

models across the range of possible health co-benefits. 

Overall, methods are available for estimating health co-benefits, but the lack of sustained 

funding has limited the field's growth and ability to provide estimates of health co-benefits of 

specific policy proposals that might be under consideration at local to national scales. 

c) As mentioned in response to question la, research on health co-benefits can provide 

policymakers with more holistic and realistic information on the costs and benefits of climate 

mitigation policies. The financial costs of climate mitigation activities do not reflect any 
171 

beneficial benefits for human health. Mitigation health co-benefits studies can help identify the 

policies with the greatest benefit to health and to climate mitigation. 

Case study research can also complement modeling efforts to provide policy-makers with 

localized evidence of health co-benefits, as well as compelling narratives and examples of 

replicable actions. Further, research can provide insights into whether mitigation policies could 

have adverse health consequences (dysbenefits or harms) and identify. measures that could be 

taken to reduce those harms. 

d) There are several things that policy makers could do to leverage information on health cobenefits. First, they can consistently include health co-benefits in discussions of climate change 

mitigation. Second, they can work with health co-benefits modelers to explore estimates with 

particular policy relevance. Third, they can encourage funding for health co-benefits research so 

more information is available to inform policy debates. 

lessons from research on communication around mitigation action on climate change include 

that it is (1) important to frame policy solutions in terms of what can be gained from immediate 

action; (2) aspirational climate policy initiatives can tap into American's deeply held motivation 

for building a bettertomorrow3

; and (3) Americans find information about the potential health 

co-benefits of mitigation policy actions compelling•. Including information on health co-benefits 

can help the American public evaluate the value of mitigation policies under consideration. 

'Vander Linden 2015. Perspectives on Psychological Science 001:10.1177/1745691615598516 4 Maibach et al. 2010. BMC Public Health 10:299. 
172 

2) Your work has touched on the need for a more robust climate change and health research 

enterprise. 

a. What are the most pressing global research priorities related to public health impacts 

of climate change? 

The research priorities for the health risks of climate change can be categorized as ( 1) increasing 

understanding of the associations between weather I climate and health; (2) modeling how the 

burden of climate-sensitive health outcomes could change with additional climate change; {3) 

developing, implementing, and evaluating policies and measures to promote and protect 

population health today and in the future; and (4) estimating the health co-benefits of 

mitigation policies and technologies, to ensure mitigation strategies maximize environmental 

and health benefits. It is important to build resilience to multiple simultaneous stressors and to 

mounting damages from climate change across the country. 

The Future Earth Knowledge Action Network developed recommendations to the Belmont 

Forum on critical research areas at the nexus of climate change, environment, and health. The 

recommendations were identified through scoping meetings, consultative discussions, and an 

online global survey. Key research priorities are summarized below. 

1. Support is needed for implementation science; models ond scenarios to describe future 

vulnerabilities under orange of eli mote ond development futures; ond research ond 

monitoring of global environmental change ond health. 

Implementation science is needed to bridge from science to policy, including explicitly 

incorporating future risks of climate change into policymaking, understanding the process of 

promoting stakeholder engagement, making science relevant at the spatial, temporal, and 

administrative scales of interest, and improving monitoring and evaluation of decisions. 

Models ond scenarios to described future vulnerabilities to inform modeling of risks are needed 

under a range of climate change and development projections by extending the Shared 

Socioeconomic Pathways (SSPs) to strengthen the representation of drivers of health. Results 

will help inform modeling of future risks of climate change, to inform policy decisions at the 

country level. 

2. More effective disease control strategies require better understanding of the relative 

importance for health of land use change, biodiversity loss, ond other environmental drivers 

ond their interactions. 

Significant investments in the weather, water, and climate research enterprise have resulted in 

greater skill in seasonal and sub-seasonal forecasting of weather and climate events of 

relevance for human health. These forecasts, coupled with knowledge of exposure-response 

relationships, can identify conditions conducive to disease outbreaks weeks to months in 

advance of outbreaks. This information could then be used by public health professionals to 
173 

improve surveillance in the most likely areas for threats (Morin et al. 2018)5• Early warning 

systems are well established for drought and famine. And while weather- and climate-driven 

early warning systems for certain diseases, such as dengue fever and cholera, are employed in 

some regions, this area of research is underdeveloped. Developing and deploying early warning 

systems based on temperature, precipitation, and other environmental data provide an 

opportunity for early detection leading to early action and response to potential pathogen 

threats, thereby reducing the burden of infectious diseases today and as some diseases change 

their geographic range, seasonality, and intensity of transmission with climate change. 

In general, declining biodiversity is associated with increased disease risks, although the 

associations are complex and variable across settings, and mechanisms and pathways are often 

not fully understood. Climate change can accelerate biodiversity loss and lead to changes in the 

distribution and incidence of a range of infectious diseases including vector-borne, food- and 

water-related diseases. Also, environmentally-friendly public policies can result in health 

benefits through mechanisms such as reduced air pollution, clean water, reduced vector borne 

disease risk, and improving mental health, but the reported benefits need better quantification 

in a range of settings. 

3. Understanding the effects of multiple interacting social and environmental changes on the 

quality and quantity of food will help develop solutions to improve nutrition and health. 

Feeding the world's population remains a pressing challenge. Human populations are growing, 

while globalization is spurring a nutrition transition in many low- and middle-income countries 

to diets high in fat and sugar, with major effects on global health by increasing the risks of noncommunicable diseases. The growing demand for food is placing pressure on the world's food 

systems and the ecosystems that support them. Additionally, climate change and changes in 

water availability will impact the quality and quantity of food, with the most negative effects in 

tropical and sub-tropical regions. There are important health implications, directly via nutritional 

pathways, such as increased risks of stunting, and indirectly, for example by increasing the 

impoverishment of subsistence farmers. Increased exposure to heat stress will also threaten the 

livelihood of subsistence farmers and other outdoor workers in sub-tropical and tropical regions. 

Rising concentrations of carbon dioxide (C02) from the burning of fossil fuels and deforestation 

will also adversely affect nutritional outcomes through plant physiology mechanisms. Plants 

obtain the carbon necessary for their growth primarily from atmospheric co, and draw other 

required chemicals from the soil. co, concentrations are rising in the atmosphere, increasing 

from about 280 ppm during preindustrial times to 410 ppm today. Higher concentrations of C02 

are generally acknowledged to stimulate plant photosynthesis and growth, with potential 

benefits for the productivity ofthe cereal crops that remain the world's most important sources 

of food. However, concentrations of minerals critical for human health, particularly iron and 

zinc, do not change in unison with co, concentrations. The result is that major cereal crops, 

particularly rice and wheat, respond to higher co, by increasing synthesis of carbohydrates (e.g. 

starches and sugars) to the detriment of protein and by reducing the quantity of micronutrients 

'Morin et al2018 Current Environmental Health Reports doi.org/10.1007/s40572-018-0221-0 
174 

and B-vitamins critical for human health (e.g. Zhu et al. 2018)6

• This reduction in nutritional 

quality could affect hundreds of millions of people. 

Research is needed to analyze environmental and health consequences of the current and 

projected agri-food systems; develop innovative foods or production methods that optimize 

health and environment outcomes; identify and evaluate dietary changes that are culturally 

acceptable, economically feasible, healthy, and environmentally sustainable; and assess 

combinations of strategies that will enable effective behavioral change. A particular emphasis is 

needed on the vulnerability of subsistence agriculture to environmental change. 

4. Models and scenarios ore needed to assess future health risks from climate change, and the 

potentia/losses and damages to critical health infrastructure from extreme weather and 

climate events, including economic and societal costs of disaster preparedness and response. 

Research in this area will contribute to our understanding of the limits to adaptation. Research 

outputs, such as software tools for scenario analysis, can be used by local authorities, disaster 

management organizations, departments of health, private sector, NGOs and other civil society 

partners involved in efforts to increase resilience and reduce vulnerability. In particular, 

vulnerability considerations should identify and address gender, socio-economic status, and 

other determinants of health that may contribute to inequity. 

Global change is increasing the risks of a range of disasters at local to regional scales- some 

rapid and "kinetic" such as intense storms and floods; others such as heat waves and landscape 

fires; and still others that may persist over months and even multiple years, such as droughts 

and pandemics. Disasters cause acute injuries and deaths, and follow-on impacts, including 

infectious diseases, mental illness, hunger, conflict, and population migration. Often these 

effects are complex and inter-related. Research could help advance the science of disaster 

(impact based) event forecasting, the understanding of disaster impacts on disease dynamics, 

mental health, food systems, etc. as well as the practice of disaster preparedness and response, 

and the promotion of disaster resilience. This work could include evaluating the effectiveness of 

ecosystem-based strategies such as the protection of wetlands, coral reefs and mangroves, and 

the effectiveness of social safety nets, and preparedness efforts, particularly in urban contexts. 

Climate change is expected to accentuate vulnerability to a wide range of extreme weather and 

climate-related disasters and increase population exposure to harm. 

5. Research should utilize complex systems approaches and innovative tools such as in situ 

sensors and smartphone-based geocoded personal data collection to understand 

vulnerabilities and building resilience in urban areas. 

The majority of the global human population now lives in urban centers. Cities are responsible 

for 85% of global economic activities and about 75% of greenhouse gas emissions. The effects of 

urban lifestyles on health and wellbeing vary widely, and are affected by wealth, social status, 

and specific features of the urban environment. In high and middle-income countries, urban 

health threats include air pollution, noise, barriers to physical activity, absence of green space, 

and in some cases social exclusion and poverty. Cities in low income countries confront all these 

6 Zhu eta!. 2018 DOl: 10.1126/sciadv.aaq1012 
175 

problems, compounded by critical shortages of physical infrastructure (potable water supplies, 

sanitation, electricity, waste management, transport), uncertain land tenure, poor governance, 

and other challenges. Cities are subject to the urban heat island effect, resulting in higher 

temperatures (and associated elevated health risks). Green space can reduce the heat island 

effect and passive and active cooling of buildings may reduce the health effects of heat 

extremes, as well as have positive impacts on mental health and wellbeing. Many cities are 

susceptible to sudden climate disruptions; reasons range from being situated in coastal locations 

subject to storm surges and sea level rise to having poor quality and vulnerable infrastructure. 

6. Research at the interface of energy, climate change, air quality, and health could support 

analyses of the health, socio-economic and environmental effects of different energy sources 

(e.g. biomass, manufactured fossil fuels, and renewab/es); emerging technologies (e.g. 

hydraulic fracturing); and strategies to promote clean energy use. 

Energy production and use has brought enormous benefits for health and has created a host of 

negative health outcomes from indoor and ambient air pollution and other exposures; pollution 

causes about 7 million deaths annually. Eighty-five per cent of fine particulate air pollution is 

related to energy use. At the same time, many people in low- and middle-income countries lack 

sufficient energy, and available energy sources such as biomass (particularly when burned 

indoors in close quarters) bring many ill effects. Innovative energy strategies and technologies 

offer promise for health, equity, and sustainable development; well-crafted policies can reduce 

greenhouse gas emissions and short-lived climate pollutant emissions whilst yielding health 

benefits. 

7. Health impact assessment should be integrated into evaluations of technologies and policies 

to support progress towards the circular economy. 

Current patterns of economic development are inefficient and produce large amounts of waste 

including pollutants that can affect human health. Efficient use of natural resources and energy 

together with more effective regulation of the use and disposal of potentially toxic chemicals 

can result in substantial benefits to health and natural systems. However, the effects of 

widespread population exposure to many chemicals in the environment are still poorly 

understood. For example, electronic and other waste is exported to low income countries where 

regulations are lax and millions of people work in or live in close proximity to waste dumps. 

Contamination of freshwater from agricultural runoff and industrial chemicals is a serious threat 

to health in some parts of the world. The circular economy aims to promote greater resource 

productivity to reduce waste and avoid pollution including through reuse, recycling and 

increased durability of products, but little is known about the implications for health. Health 

benefits could accrue from reduced exposure to toxic pollutants but there are also risks to 

health for example from poorly regulated recycling and trade in waste products. 
176 

b. Can yau a/sa discuss the state af the research enterprise on climate change and health 

in the United States, and what specific investments should be prioritized? 

The research enterprise on climate change and health in the United States is quite small, ad hoc, 

and leveraged on investments in other areas of environmental health research, particularly the 

study of air pollution. Because funding is limited, research has focused most intently on 

exposures that are relatively easy to measure, such as ambient temperature. Other issues with 

more substantial health burdens, such as Lyme disease and wildfire impacts, have been 

relatively neglected. No funding agency has identified climate change and health as part of its 

portfolio, and the field's growth has been constrained by lack of investment in training, 

development of senior research mentors, and sustained funding upon which interested 

investigators might build their careers. 

A 2009 review estimated the extent of Federal funding to research on the health risks of climate 

change was less than $3 million annually; this was funding across the National Institutes of 

Health {NIH), the Centers for Disease Control and Prevention; and the Environmental Protection 

Agency7

• The review recommended funding of greater than $200 million annually to help the US 

prepare for, manage, and recover from the health risks posed by climate change. A separate 

review of the 2008 budget appropriations found that of the nearly 53,000 awards by NIH that 

year, approximately 0.17% were focused on or related to climate•. The National Institute of 

Environmental Health Sciences {NIEHS), an institute within the National Institutes of Health, 

announced in 2011 that it would launch a research program in climate change and health. Its 

Strategic Plan 2012-2017 mentioned climate change twice; one mentioned climate change as a 

driver of changes in environmental exposures that could contribute to the worldwide increase in 

chronic, non-communicable diseases9. The second mention was as an example of research to 

help inform policy responses. The annual budget reported by NIH to the US Global Change 

Research Program on climate change in 2015-2017 was $8 million per year, or about 0.025% of 

the overall NIH budget of US$32 billion in 2016 and 0.3% of the research budget of the US 

Global Change Research Program that coordinates federal research across agencies conducting 

research on climate change. A search of the NIEHS website in 2016 listed 13 ongoing projects 

that focused on some aspect of climate change and health. The NIH Research Portfolio Online 

Reporting Tools lists projects under the category "Climate-related exposures and conditions"; all 

were awarded in 2015 or 2016. A listing for the category "Climate change" identifies 30 projects 

funded in 2017, including funding for conferences. In comparison, research on antibiotic 

resistant bacteria received $774 million in 2016. 

Climate change is altering all aspects of life, with risks projected to increase substantially over 

this century even with proactive adaptation. Significant investments in research and technology 

development are needed that prioritize the needs of particularly vulnerable communities and 

locations. The methods and tools are available, as is a growing base of researchers and 

7 Ebi et al. 2009. Environmental Health Perspectives117:857-862 

8 Jessup et al. 2013. Environmental Health Perspectives 121:399-404 9 Ebi et al. 2016. Environmental Health 15:108 
177 

practitioners. Federal funding agencies need to acknowledge and fund the research and 

development that will help individuals and communities to prepare for a future that will differ in 

many aspects from today. Failure to do so will harm the health and well-being of Americans. 
178 

Science of the Total Environment 627 (2018) 388-402 

Review 

Public health co-benefits of greenhouse gas emissions reduction: A 

systematic review 

jinghong Gao a.b.c, Sari Kovats ct. Sotiris Vardoulakis ",Paul Wilkinson r, Alistair Woodward g. ]ing Li h, 

Shaohua Gu '. Xiaobo Liu '\ Haixia Wu ', Jun Wang a, Xiaoqin Song b.c. Yunkai Zhai b,cj,*. 

jie Zhao b,c;*, Qiyong Liu '·** 

HIGHLIGHTS 

• Comprehensive GHG mitigation measure$ across various sectors tend to proARTICLE INFO 

Editor: P.Kassornenos 

GRAPHICAL ABSTRACT 

Potential pathw,ws that greenhouse gas mitigation measures result ln public health co-benefits. 

ABSTRACT 
179 

]. Gao rtai./ Sdr.nce oftl!r Iota! r:nvironmenr627 (2018) 388-402 189 

Climatrchange 

Contents 

I. Introduction 

2. Methods. 

2.1. Relevant definitions 

2.2. Data sources and search strategy 

2.3. Inclusion criteria . 

2.4. Study selection 

2.5. Data extraction 

2.6. 

2.7. 

3. Results 

3.l. Energy generation sector . 

3.2. 

3.3. 

'3.4. 

35. Industrial and economic processes. 

3.6. Other. 

4. Discussion . 

389 

390 

390 

391 

391 

391 

391 

392 

392 

392 

392 

392 

396 

396 

397 

397 

397 

398 

400 

400 

400 

4()() 

4()() 

t.lntroduction (Watts et aL, 2017b ).ln 2016, the value of economic losses resulting 

more and intense he<ltwaves (WdttS et al.. Warts 

E't aL, ambient temperatures during this peroid 

have manual labour productivity worldwide 

from climate~related events were reach totally US$129 billion (Watts 

et al., 2017a). According to the report from World Health Organization 

{WHO), only the well understood impacts of climate 
180 

390 }. Gao etal./Saenteofthr Iota/ Environment 627 (2018) 388--402 

(Baer et al., 2008; Costa et al., 2011 ). Low~ and middle-income countries point out that they are only retracing the same development 

path taken in the past by present-day high-income countries. This 

highlights the worldwide challenge to find equitable low-carbon 

routes to achieve better health and prosperity. 

Studies published in The Lancet have shown that appropriate climate 

change mitigation strategies can have additional, independent, and 

largely beneficial effects on public health (Haines. 2012; Watts, 2009). 

For instance. GHG mitigation actions aimed at reducing fossil-fuel combustion can produce health benefits by decreasing local air pollution because, GHGs and air pollutants are-, to a large extent, emitted from the 

same sources (Fig. 2) (Aunan eta\., 2006; Chae and Park, 2011; 

Cifuentes et al., 200 ib; Watts et Jl.. 2017b). Win-win opportunities of 

this kind may make GHG mitigation strategies more attractive and encourage their implementation (Edenhofer et aL, 2014; Field et a!., 

2014; Shindell et at. 2012; Watts et aL. 2017b). At the very least, cobenefits can reduce or exceed the costs of taking actions against climate 

change and therefore, can strengthen the case for climate change mitigation policies in the face of scientific uncertainty (Kelly et al., 2017; 

Nemet ct al., 2010). 

Although the scientific literature has focused on the "health cobenefits" of GHG mitigation in recent years, to date, no comprehensive 

review has been conducted specifically assessing the relationship between GHG emissions reduction and ancillary health benefits. 

"' floods, storms, 

tl hurricanes, bushtlres; 

~ illness and deaths 

C' caused by thermal 

"' and posttraumatic 

"' z stress; populations 0 

u displacing; impaired 

food supply 

Summarizing and understanding these co-benefits on health can 

provide helpful information for policy makers in their decisionmaking processes to prioritize the development and implementation 

of win~win GHG mitigation measures that can help protect people 

from the impacts of climate change (Cheng and Berry, 2013; 

Pachauri et aL, 2014a; Watts eta!., 2015). Accordingly, the purpose 

of this review is to synthesize the current evidence of public health 

co-benefits of GHG emissions reduction in different economic sectors. We aim to summarize what is presently known about the pathGHG reductions can bring ancillary health benefits 

the relevant uncertainties associated with process of the health 

co-benefits assessment. 

2. Methods 

2.1. Relevant definitiom 

According to the Fifth Assessment Report of the lPCC, the term 

"co-benefits," also known as ancillary benefits, refers to the positive 

effects that a policy or measure aimed at a particular objective has on 

other objectives, irrespective of the net effects on overall social welfare (Pachauri et aL, 2014a: Smith et al., 2014). We define public 

health co-benefits as measures to reduce the emissions of climatewarming pollutants (mainly GHGs), which also hold the potential 

diseases because of 

water-bome infectious impaired tOod and 

dh'Cases; he~tt~related fresh water supply; 

diseases; malnutrition and physical risks and 

mness due to impaired mental ill-health 

crop yield and fresh water caused by unstable 

supply; exposure to social/political and 

environmental toxicants displacement, ~tc. 

Fig. 1. Sthemati< ~tlmmJry of clim.1te d1<1nge detrnninants ,1nd potenti.1! p.1ihw<tys through which rlim,tt!:' change affect:; human he,J!th. 
181 

j Gao eta/. I Saenn' of the 1om! f:nwonmrn/627 (2018) 388"402 391 

to improve human health, independent of the effects on climate 

defined under the Kyoto protocol, include C02, methane 

(N20), and three halocarbons, and the effects of 

mixtures are commonly in terms of C02 equivalents 

(CO:reqs) (Breidenich et aL. In order to limit rncan global 

warming to 2 ~c. it is necessary to reduce the emissions of not only 

the official GHGs but all climate-active pollutants with high positive radiative forcing (RF). These include, biJck carbon (BC) and 0 1 (Kopp and 

Mauzer,lll. 2010; Shindell et al., 2012; Thus, in the 

present study, we include 0 3 and 

pollutants). 

2.2. Data sources and search strategy 

A comprehensive literature search for peer-reviewed studies published up to March 2015 was conducted using the electronic databases 

PubMed, Em base, Web of Science and ScienceDirect (Elsevier), We subscribed to the email alert servlce of each selected database so that we 

uptodate information on related studies. In 

materials from the WHO, the !PCC. lhe 

!nternationJl Energy Agency (lEA), Global Change (http://www, 

globalchange.gov/), and the World Bank were also searched for further 

information. References in the retrieved articles were examined and 

then manual searches were conducted to recover relevant papers that 

were not included in the 

des were included 

search used the following Medical 

the US National Library of 

gas," "GHG," "carbon," "C02." 

"ozone," "capture," "cut," "low," "limit," 

dun:," "sequestration," "benr?fit," "co-benefit," 

"cost," "disease burden," and "health." The search 

2.3. Inclusion criteria 

Our inclusion criteria were based on the primary searches related to 

GHG emissions reduction and public health co-benefits. 

• Types of studies: only original, peer-reviewedjoumal articles were included. Reviews, reports. conference abstracts, books, and metaanalyses were excluded. 

~ Research factors: GHG emissions reduction was one of the exposure 

indicators of interest. 

at least one public health co-benefit indicator Wds 

• Effect measures: the quantitative association ofGHG abatement with 

ancillary health gJins was estimated. 

2A Study selectl'on 

Three of the present authors (JHG, JI~ and SHG) independently 

screened the results of the literature search for the potential relevance, 

based on the information presented in article titles and abstratts. The 

full text of each article identified as potentially relevant by either one 

or more review authors was retrievrd. The same three authors indepen~ 

dently assessed the eligibility of full text articles according to inclusion 

criteria. When the eligibility assessment varied among review authors, 

a discus~ion was held to reach consensus, 

2.5. Data extraction 

Two authors and JL) extracted data independently from the 

final selected using a pre-designed data extraction form. 

Studies that met the eligibility cJiteria were retrieved and the following 

key information was obtained: publication date, study region, sectors 

involved, measures, climate benefits, and health cobenefits. then cross-checked and any discrepancies or 

disagreem(~nts were discussed by thl' data extractors and resolved 

through consensus. 

Fig. 2. Potentia! pathways th,ll g~eenhou~e gas rmtig,1tmn meJ<;Urf'~ rt'$ult in IH:'<lllh m· beneftt~. 
182 

302 j. Gao er at I Science of the Total ErlV!roument 627 (20 18) 388-·402 

2.6. Quality assessment 

Two authors UHG and XBL) independently assessed the quality of all 

included studies. Ibe STROBE approach {Strengthening the Reporting of 

Observational Studies in Epidemiology} (Vandenbroucke eta!., 2007; 

von Elm eta!., 2007) was selected and adapted to describe the reporting 

quality of the final identified studies, As in previous systematic reviews. 

the adapted STROBE checklist (Appendix A} Wds employed to create a 

binomial scoring system (criterion met 1, criterion not met= 0) 

(Aimoneet al., 2013; Gao et al., 2014). The score percentage (reporting 

quality) of each included article was based on the numbers of reporting 

quality criteria met divided by the total numbers of criteria involved 

during the quality assessment. Studies that were adjusted tOr potential 

confounding factors, quantified health gains of different GHG reduction 

target:>, or monetized health co-benefits of reducing GHG emissions 

were given higher quality ratings. 

2.7. Data synthesis 

Because different methods, models. assumptions, GHG reductions 

policy scenarios, and exposure-response coefficients were applied, 

cross-study aggregate estimates (meta-analysis) could not be performed, Instead, data synthesis largely consistl':'d of reporting key findings from individual studies and narrative summaries were provided. 

3. Results 

A total of 10,319 records were identified from the databases and 

websites, and 94 additional articles were retrieved through references. 

expert advice, and email alerts ( uptodate notifications). After removing 

duplicates. the titles and abstracts were scanned for relevance. Based on 

the inclusion criteria, studies that dld not involve quantitative association bet\Neen GHG emissions reduction and health co-benefits were ex~ 

eluded. Then, 205 articles were screened for a full text examination and 

In genera!. the 36 

countries, seven developing 

countries, and seven globd! level The association between 

GHG reductions and health co-benefits was investigated almost entirely 

by modeling studies, located in one or more of the following sectors: en3.1. Energy generation sector 

(e.g. improving energy efficiency. expanding natural gas use, and wind 

Table 1 

Searchstrategyandprotoml. 

!n the TitiC'/Abstract for all fields:"(!)" AND ~q:" AND "lj)" 

electricity generation) could prevent 9870-23.100 deaths in 2020 due 

to the corresponding reductions in ambient PM10 (particulate matter 

{PMJ with an average derodynamic diameter of 10 ~un or less) (Chen 

et aL. 2007). He et al. modeled the benefits of an aggressive energy pol~ 

icy scenario that enhanced air pollution control along with improved 

energy efficiency and structure and projected that compared with the 

BAU, by 2030, 1469 million fewer metric tonnes (Mf) of C02 would 

be emitted and 135,811 deaths from aU causes would be avoided as aresponding reductions in PM25 and 0 1 (West et al., 2013). 

3.2. Transportation sector 
183 

.f. Gao et aLI Science of the Total fnwronment 627 (2018) 388-.-402 393 

reduction policy scenario that ramped up PM-oriented vehicle inspection and maintenance programs aimed at taking high-emitting vehicles 

off the road, targeting in particular diesel-fueled vehicles and motorcycles in the Bangkok area. Relative to the BAU scenario in 2015. it was estimated that the program could reclure GHG emissions by 

approximately 0.4 MT of C02 per person yearly, and prevent about 

913 premature deaths due to a 25% reduction in roadside PM. The authors estimated that the positive economic impacts would outweigh 

the cost of policy implementation (Li and Crawford-Brown. 2011 ). 

When Woodcock and colleagues chose two settings~ London, UK, and 

Delhi, India·- to estimate the health effects of urban !and transpmt by 

comparing alternative transport scenarios with BAU 2030 projections, 

they found that reductions in C02 emissions through the combination 

of active travel and lower-emission motorvehides had the largest benefits (7439 disability-adjusted life years [DAI.Ys] in London and 12,995 

in Delhi), greater than those obtained by an increase in active travel or 

use of lower-emission motor vehicles only (Woodcock et aL, 2009). 

The authors further argued that in order to reduce GHGs and simulta·· 

neously improve public health, transport policies should prioritize the 

needs of pedestrians and cyclists over those of motorists, and increase 

the acceptability, appeal. and safety of active urban travel. Similar health 

co-benefits of mitigation measure in transportation sector were also 

concluded in Basel, Switzerland and Kuala Lumpur, Malaysia, based on 

modeling investigations (Kwan eta!.. 2017; Perez et al., 2015 ). 

Several studies have attempted to quantify the benefits of substituting motor vehicle travel with active travel (e.g. walking and cycling). fn 

New Zealand, Lindsay and colleagues reported that despite an additional five cyclist fatalities from road crashes. shifting 5% of vehicle kilometers to cycling would decrease transport-related GHG emissions by 

Records identified through database 

searching 

(n '' 10319) 

l 

0.4%, and prevent about 122 premature deaths annually as a result of increased physical activity and reduced local air pollution. An impoitant 

finding in this paper is that the health benefits of moving from motor 

vehicles to bicycles largely accrue from increasing physical activity, 

and these outweigh by a large margin the losses resulting from road 

crash injury (Lindsay et a\., 2011 ). Rojas-Rueda et at conducted a 

study in Barcelona, Spain to assess the health impacts of travel by bicycle in an urban environment Compared with travel by car, an estimated 

9062 MT of C02 emissions were reduced and 12 premature deaths 

avoided each year by the shift to cycling (Rojas-Rueda et aL, 2011 ). 

Maizlish and colleagues quantified the health benefits of transportation 

strategies to reduce GHG emissions in the San Francisco Bay Area, Although increasing median daily walking and cycling from 4 to 22 min 

could increase the traffic injury burden by 39% (5907 DALYs), Maizlish 

et al. found the burden of cardiovascular disease and diabetes would dedine by 14% {32,466 DALYs) and the GHG emissions would decrease by 

14%. The authors concluded that increased physical activity associated 

with active transport could generate significant net improvements in 

public health (Maiz!ish et at, 2013 ). A study from Adelaide, South 

Australia modeled the effects of shifting vehicle kilometers of passenger 

vehicles to alternative transport (e.g. bicycle and public transport) on air 

quality, GHG emissions and public health, compared with the BAU 2030 

scenario. It concluded that road traffic-related C02 emissions would decline by 191,313-954,503 MT annually and that 160-542 premature 

deaths and 2113-7674 DALYs could be prevented per year due to im~ 

proved air quality, increased physical activity, and avoided traffic inju~ 

ries (Xia et al., 2015). David Rojas-Rueda et al. estimated the health 

impact of increased cycling and increased walking in Six European cities, the authors reported that the two scenarios produced health 

Additional records identified through 

references, expert advice, and email alert 

(n~94) 

! 

I 

RecQrds after duplicates removed 

(n ~"' 64!7) I 5995 were excluded 

1------->1 because of irrelevant titles 

and topics: 

I 

Records screened by examining I titles and abstracts 

(n--,422) 

217 did not meet inclusion 

1

1------->1 criteria according to 

1-- abstracts 

I 

Full-text articles assessed for I 

eligibility 

(n ccc205) 169 articles were excluded 

becau$e: 

• 25 not included the focal 

1------->1 problems 

I 

Afh:r re\'iewing hy full text for I tlna! eligibility 

(t1·'36) 

• 7 had no original data 

• 137 had no quantitative 

effect estimates 

Fig. 3. Flow char( of Str('{;ning proces_~ of the literJrure search, 
184 

]. Gao et aL 1 Saence oj the Total environment 621 (2018) 388-102 

Table2 

Summary of the 1demifi~d studies on public health co-benefits. of greenhouse gas mitigation (n = 36). 

Clfu('ntesetal. MCxico, 

(2001a) 

USA 

Aunanet a!. (2004) Shanxi. 

China 

ChenN.JI.(2007) Sh;mghai, 

China 

Heet a!.(2010) ChuM 

Rive-andAun,m China 

(2010} 

We~t et al. (2013) Global 

(2009) 

New 

Zealand 

BMretona, 

Spain 

Mait!hhet<ll. california, 

\2013) America 

Perezetal.(2015) Basel, 

Switzerland 

XiJt>l J! (2015) Adelaide, 

Australia 

Roja~·Ruedaet a!. Six 

se<:tors 

Transportation 

and energy 

sectors 

Industry, 

power, and 

rural 

households 

Energy 

Energy, 

economy. and 

forestty 

Transportation 

Transportation 

rranspOTtJtion 

Tr,msportation 

Tr.111SportatiOtl 

Transportation 

Mitigation measures 

Transportation tncreasesinbicyc!eand 

Benefit~fordim,1te 

GHGs f('duction is 15% below BAU 

scenatioby2020 

lower GHG ernlssions in 2020 by !3% 

with re~pect to the BAU case 

20% reduction in C02 emissions 

comparerltoreferencescenario 

2020 

65.38 

82.14 

73.08 

85.19 

65.38 

71.43 

82.14 

85.71 

77.78 

74.07 

8333 

noo 

8V4 
185 

(2016) 

Kwan 

f'ti\J 

(2017) 

Agriculture and food sector 

Frielet <1!.(7.009) UK and BrazH 

UK 

B1esbrot'ketaL Dutch 

(2014) 

Milneret<JL 

(2015) 

FJrd11etal 

(2017) 

UK 

Global 

Italy 

Residential and household sector 

W1!kmson et al UK. and lnd1a Household 

(/009) energy 

Venkataraman India Household 

etaL(2010) 

Industrial and economic process 

Dudrk-et aL Russia Industry, 

(20031 

WestetaL 

(2D06J 

Global 

Crawford-Brown Mexico 

et ~!. (2012; 

Others 

Cha;;rtndPark Seoul.Kflrl'<l 

(201!) 

wastewater 

treatment 

Economic 

activity, and 

J Gao etal. 1 So'enre ofthr Total Envmmment627 (2018} 388-402 

consumptionofsaturatedfat<md 

cholesterolfromanimJ.Isources, 

whkhcausedbythemitigati-on 

measuresfromagriculturPandfood 

benefits 

82,76 

69.23 

The modrlrd me<>t-substitution In the modeled meat~substitution 84.18 

Nopresf'nted 

scenario could reduce 4-11% GHG scenario, s .. 19% sumval rates Wf're 

emi~5ions, and 10-12% land use 

AninddeJltal reductionnf17%in 

GHGernissions 

Jnmitiativt'wereinplan·today 

Gwing Russ1a a GHG emission 

aliowanwssurplusofo.3bi!l!on 

MTofC07 

Forthedecarbonisationscenario 

in2050,Mexlroalonereduces 

CO; emi5slllflS by 77% 

yrarsd.ndinn!:'aseaveragf'ilfe 

PM under the GHG policy 

82.76 

86.2l 

57.69 

62.96 

78.57 
186 

395 

Westetal. 

(2012) 

Global 

Global 

Slnnde!letaL Globaf 

(2012) 

Jensen eta!. 

(2013) 

Sabf>leta! 

(2016) 

UK 

3.3. A.f,rriculture and food sector 

mdu~try 

VJ.rioussectors 

transportation. 

etc) 

Various sectors: 

energysraors 

energy 

J Gao eta/./ Sdomce of the Total EnvHonnwnt 627 (2018) 388 402 

l4ldentifiedml"asurestargeting 

methane <md BC em1ssions 

reductions 

Cleanervehidesand increase active 

travel, rl"duce livestock production, 

improveenergyeffidencyof 

household. etc 

(7326 kt of C02 emis>ions 

reduction) 

Themeasuresforcookstovrs Re!atwetothe2030r<i'ference 

could achicv<' a 2:,% dew.',J.>e in scenario. 0.6-4.4 and 0.04--0.52 

8Cand80-90%dencawslnothcr 

of reduced concentrations of PM~., 

andotone 

for the three sc<"nilnos (;\,B. and For the three scenJrios, 19.500, 

3.4. Residential and household sector 

81.48 

68.00 

8·~.62 
187 

}. Gao eta!./ Saence of the Total Environment 6?7 (2018) 388 402 397 

may provide a cost-effective means to achieve 

health and climate mitigation goals (Wilkinson et aL. 

India estimated the benefits of initiatives 

of traditional 

stoves. per yedr and 

approximdtely 570,000 fewer premature deaths of poor women and 

children due to improved air quality (Venkataraman et al., 2010). 

3.5. fnrlustriaf and economic processes 

Dudek ct al. estimated that market llbera!izatlon. market reforms, 

from 

in 2010 and sustaining the reductions through 

approximately 370,000 premature deaths 

would be prevented globally due to reductions in surface ozone concentrations. Methane mitigation, the authors concluded, be a costof climate change mitigation policies and concluded premature deaths could be avoided per year due to reduced ozone and PM 

concentrations (Crawford-Brown et al., 2012). 

3.6. Ot/Jer 

emission control measures on climate and outdoor concentration:. of 

measures could reduce global warming by approximately 0.5 by 2050, 

the authors concluded, and might prevent 0.7·-4.7 million premature 

death!i annually due to decreased air pollution (Shinde!l et al., 2012). 

West et al. examined the health co-benefits ofCH4 emissions reduction 

scenarios in energy produ(tion, waste treatment, industry and agriculture sectors from a global perspective. Between 19,500 and 57,200 

ozone-related premature deaths could be JVoided in 2030 depending 

on the scenarios, this study reported (West et aL, 2012). Cllve E. Sabel 

et al. modeled the impact of adopted urban climate change mitigation 

policy scenarios in transport, buildings and energy sectors, and concluded that by2020, with different extents, all policies modeled reduced 

C02 emissions, with additional health benefits (Sabel eta!., 2016). 

4. Discussion 

We have summarized what is known about health co-benefits associated with GHG mitigation in energy generation, transportation, agriculture and food, household, and industry sectors at global, national 

and regional levels. Mostly positive associations between GHG emissions reduction and ancillary health gains were reported in the 36 studies that were retained from the literature search. This was true in both 

high- and low-income countries, and comprehensive measures tended 

benefits than single-sector interventions. To 

this is the first time that current evidence 
188 

398 f, Gao er ai. I SMnceofthe 1ota/ Envtronnwm 621 (2018) ]88-402 

An array of tools to estimate the health co-benefits of climate change 

mitigation are currently available. Two types of risk evidence, epidemiological and toxicological, are routinely used for environmental health 

assessments {Mc!<inley et aL 2005; Smith and Haigler, 2008). Based primarily on the existing epidemiologic.:t! evidence, a variety of methods 

such as comparative risk assessments (Friel eta!., 2009; Marl<andya 

et al.. 2009; Woodcock et al., 2009}; complex mechanistic components 

(Wilkinson et al., 2009); and macroeconomic, technological, and behavioral models Uensen eta!., 2013; Rojas-Rueda eta!., 2011; Shindell et al., 

2012) were employed to model the co-benefits ofGHG mitigation strategies. ln general, studies of health co-benefits follow a path in which 

there are four key steps, including scoping!base!ine, impact assessment, 

valuation procedures, and sensitivity/uncertainty analyses (Fig. 4) (Bell 

et al., 2008; Patz et aL. 2008; Remais ct al., 2014; Smith and Haigler, 

2008). 

identical (Bell et al.. 2008; Haines 

2014 ). fn order to conduct the most robust 

evaluation of ancillary health benefits, studies have recommended relying on the most defensible and transparent methods, the application of 

multiple approaches, and extensive sensitivity analyses (Bell et a!., 

2008; Patz et al., 2008). Effort is now being applied by international 

agencies such as WHO and researchers in the field to improve the consistency and poJtabilityofmodels, so that assessments can be readily repeated, extended and modified to assist policy-makers (Kelly et aL, 

2017; Majid Ezzati ct al., 2004; Smith and Haigler, 2008; Watts eta\., 

2015; Watts et al., 2017a). Although uncertainties and ambiguities remain. these methods may represent the best possible compilation dnd 

practice of knowledge to date regarding how to carry out fair, balancrd. 

and meaningful evaluations of activities to mitigate climate change and 

human health 2008; Patz eta!., 2008; Smith and 

ally rt?port the 

considerable et al., 2009; Shinde!! E't a!., 2012; Wl?st et al., 

2012; West et al., 2013), 

4.1. Challenges and uncertainties in estimating health co-benefits 

(Bell 

et aL, Haines et al., 2009; et a!., Patz et a!., 

2008; Remais eta!., 2014; Smith and Haigler, 2008; Watts et al., 2015; 

Younger et a!., 2008). Simply obseiving long-term trends in GHG 

abatementMre!ated health outcomes and attributing these changes directly to mitigation measures are insufficient. Health professionals 

should work closely with those involved in strategic planning and performance appraisals in relevant sectors to ensure that the assumptions 

and scenarios on which they are based are transparent and founded 

on the best available evideno:~ (Bell eta!.. 2008; Haines eta!., 2009). 

Several important sources of uncertainty arise in relation to the key 

steps of health co-benefits assessment Given the nature of the information on which the co-benefits assessments must draw, the limitations in 

dard quality and availability and the debate over exposure-· response 

functions for health outcomes, estimating the total health gains from 

the decrease in air pollution associated with GHG emissions reductions 

remains a challenge et al., 2008; Chae and Park, 2011; Cifuentes 

et al., 2001a). 
189 

). (;aa rt (!/, 1 Sdrr1cr of rhe To WI Environm.Pnt 627 (2018) 388--402 399 

Fig. 4. Structure and key steps of approaches commonly used in heJ.lth t{l--benefits assessmmt ofGHG mitigation. 

Tab1e3 

l'Otfntia! reasons for the larger h(•alth gains ofGHG mitigation can be madf:' in developing 

repons 

Items 

orunenforred 

• PopuiJtions ,m;> vullwr,lbl<' b('tause of (HJines et dL 2009: Watts 

etaL2015;Whirnweetal.. 

2015) -----------'--------------
190 

400 ]. Gao etal., Scit'nce oj the Total Enviranmenr627 (2018) 388--402 

Table4 

«busmess~as-usua!" and ffilt!gation projectwns over relevant time 

rhrre are !arg<' number of health outcomes potentially affected hy GHG 

reductions 

Thrre are short- to medium~term as well as tht> long-t<>ml health 

Different economic valuation> of health outcomes bNw!.'en developed 

and non-industnaliu•d countrie~ 

kev o.mmetoc""'" 

4.2. Strengths and limitations 

The present study has some noteworthy strengths. Firstly, it is the 

first comprehensive review conducted specifically to assess the quantitative relationship between GHG emissions reduction and health co~ 

benefits in different economic sectors. The health co~benefits associated 

with GHG mitigation measures can provide policy makers with additional incentives, raising their willingness to go beyond curtailing eliand to reduce the emissions of both GHGs and alr 

5. Conclusion 

and local governments. non-governmental organizations, polity makers, 

and other relevant st<tkeholders concerned with the development and 

implementation of low carbon technologies and policies. Additionally, 

the potential health co-benefits and cost savings that offset or even outweigh the costs of implementing abatement measures can improve the 

acceptability of GHG mitigation strategies. This can help policy makers 

to identify the most cost-effective mitigation measures in achieving the 

reduction objectives and to prioritize the use of resources in the 

ln order to avert climate change, international negotiations are in 

progress regarding further GHG reductions and increasing the number 

of countries with binding commitments to reduce GHG emissions. During 

the 2015 UNFCCC COP21 (the 21st session of the Conference of the 

Parties), for the flrst time in over 20years of UN negotiations, universal 

agreement was achieved on both climate change and mitigation actions. 

The health co-benefits of GHG 

may gain support if 

are in cost-effective analyses. This 

would help bridge the development gap between low- and highincome countries and strengthen the rationale for mnverging GHG mitigation schedules. Thus. it appears likely that the health co-benefits may 

not only off.<>et the costs of GHG mitigation policies to some extent, but 

Acknowledgments 

Conflicts of interest 

The authors all dE>c!are they have no actual or potential competing financial interests. 

Authors' contributions 

studies were identified and publlcation bias cannot be completely JHG and 

eliminated. drafted the the 
191 

). Gao etaLJ Sdent<'ofrhr1om! Environment 627 (2018) 388-402 

literature search, study selection, data extraction, and quality assessment]HG, SK, SV, PW, AW, HXW,JW, XQS, YKZ,JZ and QYL involved 

in the development of methodology and discussion of article strutture, 

and reviewed and revised the rnanu~cript. All authors read and approved the final manuscript as submitted. 

Appendix A. Supplementary data 

Supplementary data to this article can be found online at https://doi. 

org/1 0.1 016/j.sdtotenv.2018.01, 193. 

References 

401 
192 

402 }. Goo eta!. 1 Soence ofthr:Towi Fnv1ronment62? (20!8) 388·402 
193 

TOPICAL REVIEW • OPEN ACCESS 

Ancillary health effects of climate mitigation 

scenarios as drivers of policy a review of 

air quality, transportation and diet co-benefits 

modeling studies 

To dte thls artlde: Kelly M Chang et af 2017 Environ 

Related content 

This content was downloaded from JP address 2·10.7.24.40 on 21/i-J/2017 at 00:51 
194 

lOP PubliShing F:nviron. Res, tett. 

Environmental Research Letters 

®_"' ___ """"""'__ ----------- TOPICAL REVIEW 

Ancillary health effects of climate mitigation scenarios as 

drivers of policy uptake: a review of air quality, 

transportation and diet co-benef1ts modeling studies 

oPEN ACCESS 

RECEIV!J.I 

JO/>.l"r<h2017 

14Sep!cmber2017 

ACCEI'lEDfOOPtiBl!CATION 

J7 ~cptcmber 20!7 

27(lcttJher20l7 

Kelly M Changl, Jeremy J Hess 1

, John M Balbus2

, Jonathan J Buonocore3

i:\ David A Cleveland4

, Maggie L 

Grabow5, Roni Ncff6 1:', Rebecca K Saare <\ Christopher \V T essumR, Paul Wilkinson 9

, Alistair \Voodward 10 

and Kristic L Ebi11 • 

12 · · 

----------~ 3 Center for Ikalth and the Global Environment, Harvard School of Public Health, Landmark Center 4th Floor, Suite4!5, 40! Park 

(:t<.\1\l\'ci:ommnn, 

\!tr'hlll!t>nJilliu;,l(<' 

Drive, Boston, MA02.2l5, United States of America 

11 LLC C!imr\dapt. 424 Tyndall Street, Los Ahos, CA 94022, United States of America 

ll Author to whom ,my correspondence should Oc addressed. 

E-mail: krisebi@csslk.org 

Key>vords: greenhouse gases, health co-bcndlt.s, dimate mitigation, modeling, diet, air quality, transportation 

Supplementary material for this article is av,\i!ablc online 

Abstract 

1 !0(} Delaplaine Ct. 

Background: Significant mitigation efforts beyond the Nationally Determined Commitments (NDCs) 

coming out of the 2015 Paris Climate required to avoid warming of2 oc above 

pre-industrial temperatures. Health represent selected near term, positive consequences 

of climate policies that can offset mitigation costs in the short term before the beneficial impacts of 

those policies on the magnitude of climate change are evident The diversity of approaches to 

modeling mitigation options and their health effects inhibits meta-analyses and syntheses of results 

useful in policy-making. 

Methods/Design: We evaluated the range of methods and choices in modeling health co-benefits 

of climate mitigation to identify opportunities for increased consistency and collaboration that could 

better inform policy-making. \Ve reviewed studies quantifying the health co-benefits of climate 

change mitigation related to air transportation, and diet published since the 2009 Lancet 

Commission '11anaging the change' through January 2017. We documented 

approaches, methods, .scenarios, health-related exposures, and health outcomes. 

Results/Synthesis: Forty·t\VO studies met the inclusion criteria. Air quality, transportation, and diet 

scenarios ranged from specific policy proposals to hypothetical scenarios, and from global 

recommendations to stakeholder-informed local guidance. Geographic and temporal st:ope as well as 

validity of scenarios determined policy relevance. !Vlore recent studies tended to use more 

sophisticated methods to address complexity in the relevant policy system. 

Discussion: Most studies indicated significant, nearer term, local ancillary health benefits 

providing impetus for policy uptake and net cost savings. However, studies were more suited to 

dcscrihing the interaction of climate policy and health and the of potential outcomes than 

to providing specific accurate estimates of health co-benefits. health co--benefits or 

climate policy provides policy-relevant infonnation when the scenarios are reasonable, relevant, and 

thorough, and the model adequately addresses complexitr. Greater consistency in selected modeling 
195 

IOPPublistMg 

choices across the health co-benefits of climate mitigation research would fJ.cilitatc evaluation of 

mitigation options particularly as they apply to the NDCs and promote policy uptake. 

Introduction 

The :.Jationally Determined Contributions (NDCs) 

underlying the 2015 Paris Agreement under the United 

Nations Framework Convention on Climate Change 

(L'NFCCC) committed countries to deep rrductions 

in global greenhouse gas (GHC) emissions to hold 

the global average temperature below a 2 °C increase 

above pre-industrial levels. The agreement is an important step fon.vard, but by 2030 significant emissions 

reductions beyond the current NDCs will be required 

to limit warming within the 2 °C threshold (fujimori 

et al2016), the range 

of climate their broader impacts. 

impiel11CJ1tir•g mitigation policies that 

could achieve CHG emissions reductions agreed to in 

the Paris Agreement is estimated to be seYera! percent 

of global gross domestic product by mid-century (Boyd 

et al 2013). Hmvever, economic assessments rarely 

include associated health co·hencfits even though mitigation policies and technologies influence health by 

modifying health-related exposures such as non-GtiG 

air pollutants, physical and diet. Conceptual 

frame\vorks demonstrating between air quality, transportation, and diet-related climate mitigation 

activities and health exposures and outcomes arc presented in figure l. Ignoring cost savings due to health 

impacts provides an unbalanced assessment of the net 

impacts of required mitigation activities. 

The health co-benefits literature has cxvanded significantly since publication of The Lancet series of 

of mitigation policies and activities. Since then, two 

papers 2012, Smith 

et al 2016) 

effe(:tS of mitigation activities on health outcom~s, 

and a third (Nt~met et al 20!0) reviewed valuations 

of air qualit}' co-benet its of mitigation and their relevance to policy cost -bendit analysis, but did not discuss 

quantification of health outcomes specifically. Hosking 

mH.l Can1pbell-Lendrum (2012) prodtKed a 

the match betvvccn the needs 

the aYailahle research relating to 

change and quantification of health-specific 

outcomes. Their review was limited to research published as of June 2010 and since the \Vorld Health 

Assembly CWHA) ~~stahlished five research priority 

areas related to climate change-related health threats in 

2008 (\VHA 200/i), Although climate change and health 

studies nearly doubled in the tvvo years investigated, 

the authors identified only 12 studies of co-benefits 

and co-harms associated with climate mitigation and a 

dearth of studies pertaining to co-benefits in devdoping regions. Smith et al (20 16) conducted a systematic, 

semi-quantitative review applying published estimates 

of health co-benefits to quantify the relative magnitude of health and environmental effCcts related 

to implementation of the LIK Committee on Climate Change (CCC) 2008 to 2027 carbon budget 

(Smith eta/2016). 

For co-benefits studks to support a case for or 

against a particular climate Jack and Kinney 

(2010) they must meaningful scenarios, of policy into behavior, inf1ucncc 

of behavior on emissions, relationship of emissions 

to health-determinant exposures, and quantification 

of health outcomes as a result of exposure. In the 

authors' words, 'the polic·y impact of the co-benefits 

literature will be proportional to its ability to link 

credible models of economic behavior, environmental processes, and health' (fack and Kinney 2010). 

Noting the persistent diversity in modeling choices 

among the health co-benefits of mitigation studies, 

Remais et ell (20 14) also recommended increased rigor 

in the treatment of uncertainty and discount rates. 

inclusion of the range health impacts (i.e. 

positive and negative effects), ·w·ith policy makers in analytical choices, and consideration of 

low-probability, high-impact events such as nuclear 

accidents.14ost recently, Liu et al (20 17) suggested that 

in order fora model to provide policy-relevant science it 

should {I) be uniwrsal so the outputs are comparable, 

(2) tUci!itate rapid-calculation for simulating multiple 

scenarios, ;;mel (3) utilize input data that is accessible 

and straightforward. 

\'\re rcvie\v studies published over the last eight 

years modeling the health co-benefits of mitigation 

policies and activities related to air quality, transporta 

tion, and diet. Our aim is to docnment the diversity 

of approaches, modeling methods, policy scenarios, 

assumptions, and time slices of the collected studies 

so that they may be considered with respect to their 

utility and evaluatitm. Climate mit 

igation may involve a range of strategies and 

interventions in many sectors such as building, industry, infrastructure, and agriculture, but to achieve <1 

scope whi!t· still representing the diver· 

modeling choices and approaches, '<Ve limited 

this review to air quality, transportation, and diet, for 

v.rhich there is substantial health co ·benefits modding 

in the !iteratm .. :. \Ve also identify research areas requiring consistency to inform policy decisions and promote 

policy uptake. 
196 

Methods since The Lancet series, specifically November 2009 

through Janumy 2017. 'We searched PubMed, M('{iWe conducted a comprehensive revie'.v of quantita- line, Embase, and \Vch of Science using the search 

tive estimates of health ..:o- benefits of climate change terms 'health co~ benefits' and 'climate mitigation' and 

tOr each sector (see supplementary table 1 

l,\0\)i/mmt.xli<'- l{x 
197 

a complete list of search tenns). Because our intent was 

to be comprehensive, the focus was on identifying all 

potentially relevant literature, For example, \vithin the 

timeframe of interest in PubMed, the ll combinations 

of search terms for air quality identified 496 potential citations; the 17 combinations of search terms for 

transportation identified 2818 potential cita1ions; and 

the 8 combinations of search terms for diet identified 99 potential citations. 

citations were identified 

ence, with large overlap. We also reviewed citations 

in articles uncovered in our searches and included 

publications brought to our attention by co-benefits 

researchers. 

The inclusion criteria \Vere that the abstract indicated the study was a modeling study that ( l) quantified 

population level health outcomes, (2) related to changes 

in cxposure(s), and (3) correlated with a specified climate mitigation scenario or policy. Studies 

these criteria and focusing on the primary sectors 

interest were induded tOr full review. A standardized 

information matri'{ (refer to supplementaty 

tables 2, 3 was developed a priori and used by 

the reviewers (KMC, KLE, )JH, RdB, RKS, MLG, and 

DAC). Studies were compared with regards to scenario 

baseline, health-related 

outcomes, geographic and temporal 

and, when reported, health co··henefit valuation 

and proportional emissions reduction. 

not med our inclusion criteria because they did not 

report a quantification of a he:1lth outcome. However, 

studies that calculated nwrtality estimates from valuations themselves, such as studies employing the I Iealth 

Economic Assessment Tool for 

which outputs monetary 

2012), were included report 

a health outcome as an step. Studies that 

calculated impacts on the Canadian Air Quality Health 

Index (AQHO (e.g. Kelly et al20!2) were also excluded 

because AQHI is not a specific health outcome. 

Rebound, dctlneJ as \vhen the savings (either in 

health outcomes or GHC emissions reductions) arc 

reinvested in other activities that generate GHG emissions or disease, has the potential to negate some or 

all of the savings from mitigation efforts (Font Vivanco 

et al20 16). Rebound has important policy implications, 

but is not vdthin the scope of this review. 

Results 

Forty·t\ro studies published fmm ?'\oYembc-r :2009 

through January 2017 met the inclusion criteria and 

'Krv!Changclal 

quantified health co-benefits of climate mitigation, 

including 24 addressing air quality exposures {supplementary tJble 2), 12 estimating exposures related to 

exposures 

of climate efforts to the scoping 

frarne\vork by Remais et al (2014} and specified: mitigation strategy, association with health drivers, 

population, time scale, and baseline trends in demohealth-related exposures, and health, and 

health impact assessment (i.e. change in health 

driver and health outcome). "Y1ost, but not all, studies 

conducted sensitivity or uncertainty analysis. Just over 

half reported the health co-benefits in monetary terms 

in addition to specific health outcomes. Studies utiof JOOc•ulatio;n-sJpccific data sources where 

in many cases employed standard sectorspecific economic, atmospheric, transportation, health 

impact, and climate modds. Studies relied on epidemiological literature to specify concentration response 

functions describing the relationship betvveen exposure 

and health outcome, often stratified by relevant population segments. In most instances, studies had to rely 

on epidemiological studies deri\n ... ·d from populations 

other than the study population. 

Studies took one of t\VO approaches to defining 

the modeled scenario; emissions-focused or behaviorfot:used (tlgure 2). An emissions-focused approach, 

of but not exclusive to air quality co·· benefits 

investigated the health outcomes associated 

with mitigation scenarios that impact GHG emissions and have a secondary but simultaneous effect 

on health-related 

Behavior-tOcused in a 

behavior at the population levd, such as a reduction 

in motor vehicle transport or reduced consumption of 

meat, that impacts hoth health-determining exposures 

and GHG emissions. The behavior-focused 

Theoretical framevwrks were used to elaborate 

the pathways between an intervention and its eli 

rnate and health effects, and could be used to specify 

whkh were and were not included in the 

scope the analysis (e.g. Liu ct al 20 17, Xia et a! 

2015, Woodcock et al 2009). Causal loop 

were used in one case to illustrate positive negative tCedbacks and complexity in the modeled system 

(Macmillan eta/2014). 

Air quality 

Combatting climate change can reduce air pollution 

through two main m~chanisms: (1) directly, by reducing tl1e climate petwltyon air quality (described below}, 

and (2) indirectly, by reducing co-emitted air pol 

!utants, In the: US, the bttcr rnechanism ,,·j!J ha\'C 

the greatest impact on air pollution and therefOre on 
198 

GHG"'grnenhoose{las 

Figure 2. Two approaches to defining modeling ,scenarios in health co"henefits of climate mitigation studies 

matter (PM} and ozon~ to cause 

nearly 45 million deaths worldwide in 2015 {Cohen 

et a/2017). Therefore, 

higher temperatures associated with climate change may increase 

health risks by increasing the secondary formation of 

PM and 0 3, a phenomenon dubbed the' climate change 

in 

analyzed, 

outcomes, Yaluation, and other t;tctors (supplemen· 

tary table 2). Although all report health 

from the mitigation policies investigated, the range 

of approaches makes it difficult to synthesize beyond 

general statements. 

Approaches 

Motivations for the studies ranged from estimating 

current co-benefits of a specific policy proposed for 

a city or country to estimating future co-benefits globTherefore, the 

The choices of 

and temporal scale further influenced the 

analyzed, with more detailed 

scenarios generally a·•;sessed at smaller scales. 

The len:! of detail in the analytic chain 

the resultant changes 

in air pollutants were then coupled with a limited 

number of health concentration-response functions to 

estimate co-benefits. These studies had more depth in 

exploring mitigation but less in the 

underestimate the extent of health co~benefits. Other 

studies started \vith detailed models of how a range 

of health outcomes can be affected to air 

pollutants. For example, \Vest et 

several causes of premature mortality. These models 

developed for other such as 

costs and benefits 

Policy scenarios 

Studies examint•d policies relevant at local, national, 

or international scales. The specificity of some policy 

scenarios, while useful tOr specific 

choices, restricted their to other 

no logics or contexts. For example, Gilmore etal (20 lO) 

examined a 500 J\1W sodium--sulfur battery 

during off. pc;Jk of the day zmd di~chargcd 

ing peak times to replace four hours of electricity 
199 

Lett. 

generation from two types of electricity 

peaking plants in New York, US. Eight St\1dics 

on national level policies aimed at overall reductions 

in C02 to achieve national mitigation energy 

efficiency measures. improvements in generation, inter alia; for example comparing the US Clean 

Energy Standard with cap and trade policies (Saari et al 

2015, Thompson et al 2014). Other studies focused 

on informing international negotiJtions on mitigation policies. One such study estimated the health 

co-bendits in the US of implementing a global carbon tax to achieve radiative fordng levels of 3. 7 or 4.5 

VV m~2 in 2100 (Garcia-Menendez et al 2015). Rao 

et al (2013) compared multiple possible air pollution, 

which 

Policy lmselines 

Baselines to the policy scenario are important for cobenefit estimates because they determine background 

air quality and the level of additional achievable reductions via (OUnterfactuals. Several near-term studies 

used current legislation (or a scenario of legislation) 

to ensure comparability in the baseline and estimated 

health co-henetit (e.g. West et a/2012). RCP 8.5 (Rep· 

resentative Concentration Pathway of GHG emissions 

that results in 8.5 \,V m-2 in 2!00, approximately the 

(Urrent emissions pathway), for example, was used 

as the baseline for several studies to represent future 

conditions under a no mitigation policy scenario (e.g. 

Schucht et al20l:)). There are limitt~d differences in 

global mean surface temperature across the RCPs until 

2050, so RCP 8.5 is often used as a baseline for projections later in the century. 

Temporal scales 

Sources of GHG emissions 

Studies varied in the sources and species of GHG covered by the policy scenario. Sources ranged from the 

fi.Jll economy to t()ssil-pO\vered electricity, buildings, 

agriculture, and transportation. As mentioned, these 

sources "vere targeted through spt•cific policies or more 

general scenarios. I3a!bus et al (2014) took a different 

account 

reductions amounting to 

cumu!ati\'e reduction oYer 50 years. Three 

on sources of methane and black carbon (S~1rofim ct al Anenhcrg ct a! ~n;~, \Vest 

et al20l2), while others focused on C02 or C02 e. 

Modeling considerations 

Studies varied in 

analyses to t:stimate the of policies on emissions 

(e.g. Crav~~{ord-Brown et al 2.013), and emis..~ions on 

concentrations (e.g. Shindcll et al 2012). The effects 

of on emissions were estimated by selecting 

reductions {e.g. et al 2009), using 

engineering calculations (e.g. et al 2014), or 

employing scenarios d~vclopcd with models of electricity, transpo1iation, or economic systems (e.g. An en berg 

et al2U12), or a combination thereof, e.g., within an 

integrated assessment model (e.g. Rao et al 2016). 

Atmospheric response to emissions was estimated by 

chemical transport modets to estimate co~bcnetits from 

co-emissions, or coupled \Vith climate inputs or feedbacks to capture direct benefits from reducing the 

climate change penalty. Such methodological variety 

is often deliberate and appropriate for a specific policy However, it introduces an additional 

Concentration "response function cons-iderations 

The studies considered a range of adverse health 

outcomes, including premature mortality from cardiseases, lung cancer, and acute 

respiratory Studies of rnorbidity estimates 

included hospital admissions, long-term health care, 

asthma admissions, and restricted activity days. 

'vVhen no-effects thresholds were applied, they 

ranged from 7.5-50 m~ 3 for Pi\12_5, although 

there is eYidence for below this range (Lepculc 

et al 2012). Thresholds were typically derived from 

studies conducted in high-income countries, so there 

the appropriateness of applyand thresholds in low- and 

ImllOIE,-mconw countries, 'Where concentrations of air 

pollutants can be much higher. Further, s~)mc stud 

ies assumed concentration-response relationships were 

linear and others used non-linear functions (e.g. Rao 

etal ::!0!3). Additionally, the health benefits of reductions in ambient air pollution can he difficult to 

mode! without knowing the background contribution 

of household air pollution or secondhand smoke to 

total exposures (Burnett et al20 14). 

Results 

I Iealth co-benefits were reported as reductions in dis 

life years (DAI.Ys), years of li{{:_ lost 

mortality. The broad range of policy scenarios limits more ddailed statements than mitigation 

policies \vould result in health co-benefit;;, 'With the 

extent of co-benefits varyi11g hy po!iq' specifics, air pol· 

!ut~~nts considcr:.'d, and :lld)1ic choice's of gcot;raphic 

and temporal scale, demographic and socioeconomic 
200 

lOP rub!ishmg 

over the study pt~riod, and health outcomes 

Fourteen of the included studies then monetized 

the estimated health co.-benefits to estimate the extent 

to which these benefits could offset the costs of impleAlthough all showed some degree 

the differences across 

the studies in how this was calculated make:> general 

statements challenging. 

Nonetheless, studies that compared the effects of 

co-emitted pollutants to that of the climate change 

penalty suggest that the first is the most significant, 

at least by mid-century, for ozone (Selin et a/2009) and 

fine particulate matter (Garcia<\Jenendez et al2015). 

In addition, several studies reported an estimate of the 

dollars of air quality co-benefits per ton of C02 avoided. 

The range across these studies was $2-380 ton-! of C02 

avoided, with a maximum nearly double that of earlier 

reviews yielding $2-196/ton C02 (Nemet el al20IO), 

to $700-5000 ton- 1 tor CII4 

eta/2012). 

Relevance and inclusion of co-harms 

While these studies prcflcnted overall air 

efits, several indicated the potential for 

of climate policy. For example, increased health risks 

occurred in localized areas due to ~Ox titration of 

et al20l4). In addition, 

ulation arc not constrained to area, and 

of health risks was observed in specific 

regions or sectors under specific policies (Thompson 

et al2016). Thw;, distributional considerations cou!d 

identify dis-benefits for certain stakeholders even if a 

policy yielded overall health co-benefits. 

Transportation 

Twelve studies modeling health outcomes related 

to emissions reductions scenarios targeting the 

transportation sector met our inclusion criteria (supplementary table 3). While transportation studies can 

also include air quality, they indudcd multiple other 

health impacts and focused on a sector that generates 

a significant fraction of GH<3 emissions. In the United 

States., transportation is the second largest contributor 

to GHG emissions, accounting for 26% of emissions 

by economic sector in 2014 (USFPA 2015). The proportion of emissions accounted for by transportation 

increases as more renewable energy is used in other 

sectors. For example, transportation contributes 36% 

of the C~HG emissions in the US state of CaJifornia, the 

Nevv Zeahmd, over RO% of electricity is generated by hydropower and geoth~'rmal and v.1nd sources, 

road transport is responsible for 40% of energy emissions (Ministry for the Environment 20 J 7). Therdore, 

rcdtJcing tr~msport~1tion C!lliss\nns wi!! lx· irnportant 

for achieving glDhal, national, and local targ.:ts. 

Transportation choices affect health in many ways. 

Car use, for example, increases risk of exposure to: 

traffic-related injmy, physical inactivity, air pollution, 

and noise, among others (0Jiemvenhui}s1.·n and Khreis 

.?.016). Traffic emissions may caust' 185000-330000 

a1Jnual premature deaths globally (Nicuwcnhuijscn 

and Khreis 20l6). However, the casualties of transportation related inactivity outweigh those due to air 

pollution. In Nc'"'' Zealand, for example, it is estimated 

that shifting So/o of vehicle kilometers to cycling would 

avoid about ll6 deGths a year due to increased physical 

and there would be 5--6 fewer deaths a year 

by pollution from vehicle emissions (Lindsay 

et al20 ll ). Conditions that arc linked to transportation 

include cardiovascular disease, diabetes, mental illness, 

some cancers, and obesity, and among children: low 

birth ·weight, reducC'd cognitive function, respiratory 

infectlon, and decreased function (Nieuwcnbuijsen and Khreis 2016). transportation 

policies offer powerful opportunities to reduce rdatcd 

morbidity and mortality and cut GI JG emissions at the 

same time. 

tion (Stevenson et al2016, Xia et 2015, Macmillan 

et al 2014, \-\'oodcock et nl1013, Roja.<>··Rueda et al 

201!, Grabow et al2012, Lindsay et a/2011). Three 

studies started from an emissions-focused premise 

evah1ating the required shifts in transportation modes 

Creutzig et al20I2, Woodcock et al2009, Shinet al20 t6). The remaining hvo studies eYaluated 

both types of scenarios (e.g. Sabel et al20l6, Maizlish 

et al 2013 ). Research design increased in 

tion over time, starting from simple models on 

assumptions of policy or behavior implementation and 

general distribution of benefits, lo more sophisticated 

approaches stratified that cKknmd-

(e.g. \Voodcock etal20l3). 

ment of Complete Streets policies, establishment of 

a bikeshare or introduction of congestion 

charges and prict~ interventions to reJnce use 

of motor Yehides. Complete Streets policies support 

active transportation through the routine design, maintenance, and operation of streets and communities that 

arc safe and accommodating for all people, regardless of 

age, or mode of transport (Carlson et a/2017). 

On tbc hand, some of the sccn;:~rios were pol 

icy packages deYeloped with stakeholder engagement 
201 

11300! 

kg. Creutzig et al 2012, \Voodcock et al 2009 and 

2013). ShindeU et al (2016) estimated the climate and 

health benefits of reducing US emissions consistenl 

\Vith a 2 oc increase in glohal mean surface temperature; these analyses assumed transportation reductions 

avoiding 0.03 °C warming in 2030 and 0.15 °C in 2100. 

settings varied widely, from cities to regions to 

national assessments, and there was little common~ 

ality in the interventions themselves, which consisted 

of various combinations of walking, cycling, and taking public tmnsport 

scenarios were measured \Vas 

Macmillan et a/2014, Sabel et a/2016), 

Temporal scales 

Studies focused on the health benefits of increasing 

active transportation either today or within next 

few decades. et al 2016) pro.iected 

health co-benefits to end of the but the 

majority presented results for a decade in half 

of the century. TI1e baselines were generally present day 

or a recent period. 

Sources of GHG emissions 

Burning fossil fuels is the primary source of transportation emissions; over 90% of the fuel used for 

tmnse>Orlaticlr is petroleum-based, including 

.commuter motor vehicles. 

Over studies employed 

c.1ted approaches to estimate the 

harms of increasing active transport and considered 

the benefits of increased physical the 

risks of injury and road traffic fatalities, exposure to air pollution, noise, well-being, and other 

factors. Increasing method sophistication included use 

of age, gender, and fitness stratification (Woodcock 

et al10U), consideration of social and cultural t~Ktors (e.g. the extent to which biking is considered 

normal or even favored), and inclusion of inhastructure parameters {e.g. the extent and safCty of 

bike lanes). More recent studies used system dynamics modeling to address the complexity inherent 

to transportation policy including system feedbacks, 

interacting variables as drivers of behavior, 

and time-dependency of relationthat may produce tradc··oftS bct\veen long· term 

short term policy effects (:V!acmi!!::u; ct nl 

2014). 

K 1\1 Chang et ol 

Concentration- and exposure-response fimctinn considquantificatic>ns of the adverse 

to air pollution. 

other 

chronic diseases, road traffic obesity, wellbeing (e.g. mental health), and other health outcomes, 

with mortality the most frequent endpoint considered. The studies were conducted predominantly in 

high income countries; it is uncertain the extent 

to which they ·would be applicable to low· and 

middle-income countries where infrastructure, density of settlement, traffic conditions, and vchid<: speeds 

greatly. Stevenson et al (2016) is an 

a transportation modding study that 

co-benefits in a range of lower and higher income 

countries. 

Transportation health co-benefits modeling studies 

focused on classic health outcomes such as cardiovascular disease, ovcnveight, and all-cause mortality. Other 

important health-related effects of reduction in motor 

vehicle transport may be included in future studies. For 

instance, with one exception O'vlaizlish et al20 I J ), these 

models have not yet incorporated social-emotional 

wellbeing and mental health outcomes affected by 

social severo.nce (e.g. diminished social interactions in ncighborhooJs divided by roads \vith high 

volumes of motor traffic). 

Results 

Significant reductions in DALYs, YLL, and/or mortality 

~vere from active transport even when potential were considered (see table 

3). i\ more detailed ls not possible 

of differences across studies in baselines and time 

slices. Detailed longitudinal assessments, such as those 

incorporated in the ITH!M tool (\Voodcock etal1013 ), 

the cumulative benefits of 

increased 

Lindsay et al (2011), Macmillan et al (2014), 

c;rJbow etal(2011),and Sbindell etal(2016) cstin1ated 

the ('co nomic benefits. Lindsay eta! (20! I) estimated 

J 000 commuter 

cyclists per year in New and Shinddl et al 

(1016) estimated near~tcrm benefits of about US$250 

billion annually in the 

policies promoting clean 

ing on assumptions and the discount rate 

benefits would likely exceed implementation costs. 

Crabow et al (2012) also estimated economic benefits 

of$8.7 billion annually over the course of the months 

\vhen itv·:ould be the most feasible for actiYetransportation in the II largest cities in the Upper :-vfidwest of the 

US. Macmillan et al (20!4) provided a detailed costbcneJlt analysis incorporating implementation costs of 

commuter cycling policies and their health-related s.1v 

ings due to reduced mortality, hospit::tliz,l!ions, :md 

disease incidence. 
202 

IOPPubl:shmg 

One concern of 

(e.g. cyclist, 

pedestrian, heavy vehicle, etc.), road type and severity 

of et al 2012, Xia et al 2015, Lindet al2009). Transportation 

connected such that the balance of benefits co-harms in a shift to more active 

depends on infrastructure. A 50°;0 increase 

in in a city with an extensive cycling infrastructure would make only a small ditri:rcncc in 

rates compared to cities \vhere bicycle lanes arc 

common. In cities in which is uncommon, the 

safety-in-numbers ctfect of injury incidence 

with increasing bicycling prevalence is likely to result 

principally from growing pressures to invest in safer 

bicycling infrastructure (~'lacmillan et al20 14, Jacobsen 

2003). 

Diet 

As globalization and related social, economic, and 

demographic shifts continue, populations 

undergo a nutrition transition marked 

high levels of noncommunicable disease ()!CD) and 

CHG emissions, and between diets containing mostly 

minimally processed plant foods, whole grains, and 

pulses and lower levels of NCD and CHG emissions 

(Jones et al 20 l h, Auestad and Fulgoni ].0 l 5, Hall· 

strOm et al 2015, Tilman and Clark 2014-). Among 

foods, red meat has the highest G H G emissions and has 

been associated 1-vith health conditions including cardiovascular disease (Pan et al2012, Sinha et al2009), 

stroke (Kaluza et a/2012), type 2 diabetes (Pan et al 

20ll, tv!icha et al20W), and some cancers (Cho et al 

co-benefits, 

However, relationships bt~tween overall diet healthfulness and reduced GHG emissions are somewhat 

inconsistent, in part bei.:ause sugar and snacks arc often 

found to have relatively low GI IG emissions compared 

to animal sourced foods and even compared to fresh 

produce, especially when it is air freighted or gm1,vn 

in heated greenhouses (Jones et al 201 (l, Pap1e et al 

2016, Aucstad and Fulgoni 2015, HaJlstri')m etal2015). 

The variation is also attributable to considerable heterogeneity in study designs and data sources. 

\Ve identified six model-based assessments of the 

health-climate co-benefits of diet scenarios. Two were 

global in scope and considered the relative health 

co· benefits of diet changes by (Sprfngnnnn 

et al 20!6, 201/L One study on the US 

K 1\.l Chang.;ral 

(HallstrOm et al20l7), and the three others provided 

estimates for the UK (Aston et al20 12, Friel ct al 2009, 

Scarborough et al10l2), with the latter also providing 

a SJo Paulo, Brazil case study. ~1ost focused on reducing 

meat consumption or livestock production in regions 

with high consumption patterns, although ~pringmann 

et afs model (Springmann et al 2016, 20 !7) included 

reduction of exposures related to meat intake, 1-vhich 

variously included saturated fat from animal sources, 

cholesterol, and red and processed meat products. 

et al (2016), 12017) and Hallstrom et al 

whole wrsus processed 

included coronary heart 

diet-related cancers, stroke, and type 2 diabetes. 

Approaches 

A!l six diet studies 

and health hencfits 

included hoth climate 

diets, but with diffcrent approaches. Three studies began with a 

simultaneous consideration ofboth climate and health 

impncts of diets (i.e. behavior-focused). Aston et al 

assumed that the food system accounted for one third 

of UK GHG emissions, and that animal products are 

on consumption of red and processed meat, then cal" 

culated the changes in GHG emissions and relative 

risk (RR) of NCDs if high consumers of animal foods 

had diets of low consumers. Springmann et al (2016) 

foods are 

a major source of GHG emissions and N"CDs, 

and that diet change could be 'more effective than 

climate 

and 

NCDs for t(mr dietary scenarios that progressivdy excluded more animal-sourced foods, Hallstr()m 

(2017) created counterfactual healthy alternatiYc diets 

stotisticallv a>iSO<:iated with changes in the RR for three 

the GHG emissions of producing 

these diets and even of the health care system related 

(;HG emission savings. 

The other three studies began '1-Vith climate change 

mitigation strategies (i.e. emissions focused). Friel 

et a/2009 modeled the effect of four strategies (technological and a 30% reduction in production in 

UK industJY) needed to reduce (;He; emission$ in the UK to meet official targets 

fiJr 2030. They then C$timated changes population 

level intake of saturated fat and cholesterol, ;md the 

<..>tTcct on prevalence of ischemic heart disease stroke. Scarborough eta! (2012} used the 

l

1

K CCC carbon budget diet -;;ccnarios, designed as 

a climate intervention, and then estimated population 
203 

IOPPublish1ng 

then calculated dietary and weight related RR of health 

outcomes. 

Policy scenarios 

Of the diet studies, only Springmann et al (~0 17) discussed specific for achieving the modeled diet 

and population level was not dealt with in these 

studies. In general, the objective was to 'explore a range 

of possible environmental [climate] and health outcomes .. to encourage researchers and policymakers to 

act' et al2016). Exploration of policies 

for diet change and their acceptability of 

criteria. 

Policy baselines 

The policy scenarios in the included diet studies ·were 

often compared with actual dietary patterns as the basedoubling of proportion of vegetarians, a wider 

adoption of eating habits approximating the diets of 

those in the existing lowest quintile of meat consumption, or observed vegetarian and vegan intakes (Aston 

et al20l2, Springmann et al2016). Another approach 

\Vas to consider published dietary guidelines or food 

exposures for which there \Vas strong evidence of a correlation with disease, or a combination of the above 

approaches (HallstrOm et al20l7). Baselines typically 

rdkcted existing dids or were based on UN Food and 

Agriculture Organization (FAO) forecasted diets. 

Temporal scales 

Diet modeling studies presented results for a single year 

(or in one case, two years) between 2010 and 2050. 

from other sources, but selected and adjusted values 

to some extent to make them more appropriate. The 

health benefits per C02e were highly dependent on the 

assumptions, methods, and data in the LCAs used as 

CO<Il1t<erf>1<ctnlal diets. The temporal, 

tura1 boundaries used in LCAs can large effects 

on C02e per unit of food, such as whether to include 

land use change or food \vast e. 

of the studies {Springm<lnn ct al2016, 2017, 

et a/ 2017) inonrnor<1ted 

10 

K MChangctal 

Modeling considerations 

There was considerable variation related to diet def 

initions, the relationship bcnvecn diet and health 

outcomes, and the influence of diet on GHG emissions 

de novo by using assumptions about health or climate benefits or both, or by modifying existing diets 

based on assumptions about effects on GHG emis~ 

sions, or health, or both. Some studies defined them 

prior to the study according to climate change miti~ 

gation policies. There was also diversity in the extent 

of actual food intake exposures included in the models regarding components of meat or of meat products 

and inclusion of refined sugars and pulses. The most 

extensive model used '.vas DIETRON; that is parame 

tcrized by total ener);,ry, fruit, vegetables, fiber, total f~1t, 

monounsaturated fatty acids, acids, 

saturated tatty acids, trans and 

salt (Scarborough et al20 l2). 

Effects of diets, component foods, food compounds, or diet-related proximal risk factors (e.g_ 

and on health were evaluated in 

terms change in the relative risk of 

non-communic:1ble diseases (most CHD, 

cancers, type 2 diabetes), or change in YLL, 

or l )ALYs. Climate impact was used to define dids 

alone or in combination with other parameters, and/or 

v.·as modeled in terms of c;HG emissions per diet, food 

unit, or production unit (e.g. livestock) . ..Vlo~t studies 

did not include indirect feedbacks from diet change 

on climate in their models, for example the effect of 

land usc change resulting from decreased consumption 

and production of anima! foods (see below: co-harms). 

HallstrClm et al (20 17) included the reduction in GI IG 

emissions due to reductions in health c;1re costs as a 

result of healthier diets. 

l'01JUI<11Ic<n-<<ttrt1mta1Jie fractions (PAfs)/population 

impact fractions (PIFS) are used to estimate changes 

in 

on diet or body weight factors from observational 

(correlational, cross-sectional) or experimental (randomized controlled trial) data from epidemiological 

studies, or meta-analyses of these data (Scarborough 

et al2011, Springmann et al2016, Springmann et al 

2017, HallstrOm et a/2017). 

Results 

There was great variability in populations, definitions 

of diet 

narios modeled in these studies }ielded considerable 

reductions in chronic disease aud mortality, and in 

GHG emissions. For example, Springmann et nl (20 16) 

estimated that a 25(li,-l90n,b increase in fruit ;md 

etable consumption, and 5Gl}-Q--78% reduction in meat 
204 

IOPP:1blishing Environ. Res. Lett. 12 (2017) 113001 

con•surnntion could result in 5.1 million global deaths 

coronary heart disease, stroke, c.mcers, 

2 diabetes, and a reduction of 11.4-8.1 Gt 

of food-related GHG emissions. They further 

estimated that shifting the glob.:ll population to vegetarian diets, and increasing produce consumption by 

54% would result in avoiding 8.1 million deaths and a 

reduction of ll.4-.J.4 Gt year-! of food-related GHG 

emissions by 2050. They estimated the economic benefits at $1-·31 trillion, or 0.4%-150·0 of global CDP in 

2050. 

Relevance and inclusion of co-harms 

It is important to note that while there are {:O-heneflts 

for many foods, and actual and model diets, this is 

not universal. There can be tradeoffs, or co-harms, 

between climate and health effects. 

and health vary greatly. for example, compared with 

the tlS diet, the 2010 diet recommended by 

the USDA improved nutrition increased GHG 

emissions 12% (Heller and Keo!cian 2015). The main 

reason vvas that reduced meat consumption was balanced by an increase in dairy consumption, and to 

a lesser extent by an increase in seafood, fruit, oils 

and However, the health benefits 

can be in foods without the potential 

costs of dairy (not considered by the USDA), and the 

USDA-recommended diet \vith excess caloric 

intake eliminated emissions from the current 

diet by 53%, suggesting that reducing or eliminating 

dairy may be critical for avoiding co-harms from some 

recommended diets. 

example, Payne et al(20 16) reviewed 16 studies, in dudThey 

containing nutrients (which they estimated) that arc bad for health (e.g. saturated fat, salt), 

and those that arc good for health (e.g. micronutri· 

cnts), and the GHG emissions of the diets. They found 

that the majority of diets with lo\vcr CHG emissions 

had higher and lmvcr micronutrients, and that 

these diets equal or higher lt:vds of mortality and 

non-communicable diseases. 

Of the studies included in this review, only the 

Springmann et at 2016 analysis considered co-harms 

of diet change directly. That study considered the ways 

that the projected dietary change might result in under~ 

nutrition among vulnerable populations, concluding 

that the health benefits outweigh these 

harms. there ·were disparitic~ in who 

would be iwrmcd. 

An important class of co-harm is rebound, an 

consider:ltions, 

of the studies 

ll 

reviewed. Rebound can result when savings in the food 

or health care systems due to diet change are invested in 

activities that generate GHG emissions or disease that 

take back some of the benefits of the modeled scenarios. Rebound can a!so be negative and function as a 

co-benefit by reinforcing the intended effect of the see· 

nario by investing ht:alth care savings from improved 

diets in improving access to fruits and or 

revegetation of rangeland no 

production, to increase carbon sequestration. \Vhile 

rebound is, as noted, outside the scope of this rcvie\v, 

it is an important consideration for future co-benefits 

studies. 

Discussion 

Overall, despite the diversity in methods, scenarios, 

exposures, temporal scales, and other considerations, 

t\-vo important conclusions can be drawn from our 

review of health co-benefits studies. First, these studies 

consistently demonstrated that the health co-benefits of 

technologies offset 

reducing GHG emissions. That is, in many instances, 

"f"tn>cm>n~ some mitigation policies appears to 

make sense of the improvements to population health even without considering the benefits for 

Cnfontunatelly, at stage, of the 

literature are not possible because of diversity 

of upproaches and assumptions. The pmver of this 

research to support policy change would be increased 

with greater consistency (Jack and Kinney 20 I 0, Remais 

et al 2014). This diversity reflects the 

mitigation policy choices. 

because local that compare a limited set 

of policy choices arc important for local decision makers to support choosing among specified 

options, and identifying those that maximize 

co-benefits and greenhouse gas emission reductions. 

These studies must focus on the specific question(s) 

of interest. Th<:~t the analyses might not have relevance 

else\vhcrc is a secondary and minor consideration. 

The policy relevance of studies focusing on larger 

tcnlporal and spatial scales, particularly those designed 

to explore tbc current or future health co-benefits associated with transportation, or 

agreeing on a limited set 

of population, health outcomes, scenarios, time slices, 

and discount rates. 

ies to a subset of the range 

recommend that studies at least model ~1 consistent set 

of choices; doing so would promote met<~-an<:~!yses and 
205 

IOPPublish•ng 

Modeling approaches determine modeling choices 

The inherently nature of health cobenefits analyses persists in the availability of 

studies that meet the so1t of rigor and credibility across 

physical and societal systems prescribed by authors \vho 

noted the apparent lack of policy traction (Ja;:k and 

Kinney 2010, Nemet et al 20l0, Rcmais et al 20H). 

VVhile some have attempted systems-level credibility 

(Thompwn et al 2014), the n~searcher's perspective 

continues to dictate assumptions, data sources, sophistication, and comprehensiveness, In the short term, 

initiating analrses from a climate policy perspective (as 

in integrated assessment models) ·will likely continue 

to focus on the drivers of costs and GHG emissions, 

while initiating analyses from a health perspective will 

likely continue to examine a broader range of risks and 

outcomes. 

Construction of scenarios determines policy relevance 

In the reviewed studies, scenarios were constructed 

from hyvothetical ideals, concrete policies (existing 

or proposed), future socio-·technological scenarios, 

expert opinion, global guidelines (e.g. WHOiFAO), or 

in collaboration 'with local stakeholders. Where spl'-

cifk policies (e.g. COP2l) or recognized scenarios 

exist RCPs), their use enhances relevance and 

cornp<lral,ility. Studies based on mitigation strategies 

dependent on individual level changes in health behaviors (e.g, some of the dietaty and active transportation 

studies) are limited in their to inform current 

climate change policy does 

not consider change or health. 

However, proposed policies may be more effective 

oqpnizatiortal support, and in achievdimate-health co-benefits. 

behavior change and encourage shifts in institutional 

policies, such as those related to f()od procurement. 

ln developing ne\v policies, stakeholder participation can be crucial. Participator>' system 

(Macmillan ct al 2014) involves 

ers in a supported 'dynamic causal theory' 

and addresses the interdisdplinary and interlinked 

nature of co-benefits research \\ith systems-ll'vel representations. For example, camal loop (e.g. 

t-.ifacmil!an et al 20 1-t) and conceptual 

describe the model scope and causal theoty assumed 

by the model and can assist 1vith determination of policy levers for int1uendng desired health and emissions 

outcomes. Due to inherent complexity and um::ertainty, 

modeling studies elucidate the complex interactions 

bctween policy, GHC; emissions, <md health rather 

than predict ;; p:lrticubr outcome at a point in time 

(Macmilbn etal20l+). 

12 

Treatment of data gaps 

Lack of data availability for some modd inputs means 

that certain co-benefits or co-harms cannot be fully 

quantified. Modelers used a variety of techniques to 

address these data gaps. For instance, in air quality studies when comprehensive representative data 

\\·ere not available for particular countries or regions, 

concentration-response functions from cpiderniolog 

ical studies conducted in the US or other 

countries were used (e.g. \Vest et al 2013} 

exan1ple, Springmann et al (2016) 

from FAO data covering 110 regions and 32 

commodities and aggregated it to 107 and 

16 commodities to match data availability environmental and health analyses, and omitted global 

recommendations for food groups (i.e. fat, salt, whole 

grains, pulses) for which there were not adequate health 

data or recommendations. HallstrOm et al (20 I 7) did 

not include diet-NCD links for which there was not 

quality data pertaining to the RRs, so their 

emissions reductions due to the health 

care effects of healthier diets was conservative. SensiLiu et al20l7, Xia eta! 2015). 

Treatment of time lag 

Jvlodeling studies must make assumptions related to 

the temporal dynamic.<> of emissions, exposures, and 

health outcomes. Policy implementation in reality 

can be gradual and incomplete. There is also n lag 

between policy implementation and resulting changes 

in exposure, and chnnges in exposure rarely result 

in immediate health impacts. For example, there is a 

temporal gap bdween changes in diet-related GHG 

emissions and associated health impacts. The former 

dietary 

change, as food production to accommodate 

demand, while health effects could be delayed by 

decades. 

Most studies did not attempt to address the tcmdynamics of policy, climate and health 

or incorporated no time because evidence 

the on quantified benefits is small 

ct 20!4). Taking diet as an example 

again, in most models the climate and health effects 

were assumed to be equivalent to the diets having been 

adopted for some time, or the effects of the diets happening all at once. Other models assumed the results 

\vould be obtained by a climate change mitigation target 

year. Some researchers addressed the lag by employing the concept of 'committed impact' {i.e. counting 

the long-term impact of a change in exposure). 

Creutzig etal(2012) modeled the 'transition dynamics' 

of transportation policies to address implementation rha-.ing. but still assumed in<>LH1ta:1cous effects 

on health. 
206 

Incorporating complexities in health exposures 

Estimates of health co-benefits arc sensitive to the 

source of relative risks applied, the age- and sexspecific granularity applied, and the range of exposure concentrations considered, especially when the 

""""'·"''·re;;nonse curve is uncertain at the high end 

For example, for some health risks there 

may be no safe level exposure, hut epidemiology data 

be incomplete at the extremes, so models may 

assume there is an exposure threshold belmv 

which there is no measurable health effect, or assume 

no threshold and test for sensitivity at the limits for 

which data are available (e.g. \\rest etal2013). Furthermore, baseline heahh status and likelihood of behavior 

modification can influence susceptibility to exposure 

and vary by population segment, "vhich impacts the 

distribution of health co-benefits. Many studies did 

not address these complexities. However, Maizlish et al 

(2013) considered age- and gender-specificity of physical activity and health outcomes, as ·well as decreased 

population level variability in commute speed and 

active travel participation with increased prevalence of 

cycling and walking (1\iiaizlish et a/2013). Relevance 

of these types of complexities is determined by the 

research and policy objectives, 

Interoperability between health models and integrative assessment models (lAMs) 

co-bendlts studies to expand on existing swndardized 

models of large scale interactions among population, 

technology, socioeconomic factors, and emissions and 

link them to health outcomes. There arct\\'O main IA:\1 

approaches: lAMs that incorporate their O\Vn estimate 

of emissions to impacts, and IAMs that couple with 

a more comprehensive health impacts tool (pathway 

of emissions to concentrations to health). The f(:1fmer often uses simplified relationships of emissions 

to health impacts that negkct, for complex 

chemical nonlincarities (Thompson There 

is increasing sophistication in the tools used to link 

emissions directly to outcomes; however, there remains 

considerable disagreement between th<?se approaches 

and caution is warranted in applying them beyond 

their context (Hco et a/20!6). For both approaches, 

it would be helpful to inuease the number and kind 

of health outcomes considered to more broadly reflect 

the rangeofhealth co-benetlts that could arise.lncrcas 

ing the interoperability between health and integrated 

assessment models would hcilitate this inclusion. 

Guidelines for accurate and transparent health estimates reporting (GATHER) 

The WHO GATHER (Stevens eta1201h) include definitions of technical lerms (health indicator, health 

estimates, data inputs, and coYariates) and a checkli.<.t pertaining to study population, data input<; :md 

analyses, results, and discussion. CATt-IER maint<~ins 

K' M Chang ct m' 

that items on this checklist should be specified alongside published health estimates to facilitate reasonable 

comparisons across time and between different po~nilato define best practices reporting of studies that 

synthesize information from multiple sources to quandcscribe past and current population health 

;!Hielc·•·m;n<>nt<.' similar to what health co-benefits 

modeling studies do, althot1gh co-benefits studies often 

project future impacts. 

0/lodds of health co-benefits of climate mitigation span a global range in populations and data 

sources and are often constrained by data availability. 

Utility, comparability and synthesis of these models 

therefore depends on interpretation of their results 

and limitations. GATHER provides a best practice 

and standard method of documenting population-level 

health-related indicators and determinants, 

OveralL the studies rcviev-.'ed, while they do not 

mention GATHER, for the most part comply with guidelines. One area in \·'>'hich co·· benefits 

studies do not always ad hen.' to the GATHER guidelines 

is in the treatment of uncertainty. GATHER requires 

a quantitative measure of uncertainty, including meth · 

ods for calculating uncertainty and articulation of 

which sources of uncertainty arc and are not accounted 

foL Sensitivity analyses are prevalent but not ubiquitous among health co-benefits of dimate mitigation 

studies. 

Valuation of health co-benefits 

The role- of valuation of health co-benefits in the policy 

Jiscourseand methods for estimating monetized health 

benefits have been described and discussed (Bell et al 

2008, Springmann etal20t6a, Nemet et al2010). Valuation approaches include: value of statistical life (used 

in cost/benefit analyses), value of life lost \vith 

mortality analysis transfer approach, cost 

morbidity), and v,ri!!ingness to pay (to reduce mortalrisk}, among others. Valuation approaches range 

only avoided health costs 

to very 

Equity considerations 

Equity is a major pillar of the causes, impacts, and 

solutions to climate change, yet few studies hnve considered the social distribution of health co-bcneflts, "f'he 

study by Springmann er al (2016) on diet co-bendlts is 

an exception. \Vhile some air quality moJds consider 

r<~gional equity, tht:'re is a de<:wth of studies addressing 

socioeconomic dimensions, and \•.:c found no transpo!"tation stlldics th~1t modelkd ~he effects on he~1lth of 

climate mitigation through an equity lens. 
207 

lOP Publishing 

The direct effects of climate mitigations arc not 

experienced evenly, and the co-benefits and CO··fmms 

of climate mitigation policies may not be distributed 

equitably. Specifically, there is a pattern of inequity 

between the production of total and food 

the former for some increased consumption 

in the later, improving health in both. This vms expli(> 

it!y addressed only by Springmann eta{ (20 !0), whose 

scenarios reduced or diminatt.:d (vegan diet) the food~ 

related GHG emissions gap between high per capita 

emissions in the Global North and low per capita emissions in the Global South. to shift 

regressive outcomes. authors suggest complementary policy strategies to improve equity, such as 

excluding foods from taxation and 

providing compensation most affected. 

Conclusions 

As noted throughout this rcvic\V, while the studies of 

the benefits of air quality, transportation, and diet mitigation policies consistently report health co-benefits, 

meta-analyses and syntheses of results are by 

the diversity of approaches, modeling policy 

scenarios, assumptions, time slices, and evaluation 

metrics. fncreasing consistency across the air quality, 

transportation, and diet studies would begin to provide 

cornor·eh<msive estimates of health co-benefits 

options. 

To a large extent, the revic\ved literature achieved 

many of the recommendations of Jack and Kinney 

(2010) in thar the studies reported scenarios and rdationships of emissions to health-determinants, and 

quantified health outcomes. However, reporting is 

clearly insufficient if the literature is to fulfill its potential for htJving a significant polic-y impact, particularly 

at larger geographic and political scales; greater cons isnations arc developing 

nl ·~"'""'Inn options to achieve their NDC:s to 

the Paris Agreement. As choices arc made, policymakers will he ill informed \Vithout a holistic vie'v of the 

costs and benefits of the options. Incorporating a larger 

basket of health outcomes would provide more accurate estimates of tlw magnitude of possible benefits. 

Further, as noted by Remais et al (2014), considering dis-benefits also m_)Uid increase understanding of 

positive and policic<>. 

This is not to s:ly th~1t L nowlcdgc i~ 

the only or even the primary driver of poliq'm<lking 

14 

(Verboom et al20I6). The processes by which policyand decision-makers assess and usc information is 

complex. Polices need to take into consideration not 

only scientific evidence, but also competing priorities, interests. and values, and perceptions of equity, 

fairness, and ethics (Bmvcn and Zwi 2005), among 

other considerations. Iterative engagemt:nt between 

rcsearcht:rs and policymakers increases the capacity of 

policymakers to assess, evaluate, and use tbta in support 

of complex-policy interventions, and the capacity of 

(Langlois 

and use of simpli~ 

fied, universal models that facilitate rapid calculation, 

such as the greenhouse gas policy assessment model 

(GHG-PAM) developed by Liu et al (2017), could 

hdp align scientific insight to polii..-y~making needs and 

realities. 

The literature can he roughly divided into studies that focus on quantifying the health co-bcneftts 

of a specific, local mitigation policy, which gt~neral!y 

are concerned \'lrith short· term benefits; and those that 

focus on larger geographic and temporal scales. Local 

scale studies will increasingly be needed to inform 

policT-makers of the benefits associated with specific policy recommendations, to provide balanced 

estimates of the net cost of these policies and to 

help policymakers choose among sets of mitigation 

options. Because the scenarios used are in response to 

policy-maker needs, diversity vvill and must continue. 

Hmvever, agreeing on comparable health outcomes, the 

concentration-response relationships, and approaches 

to estimating the economic benefits would increase the 

policy relevance of health co ·benefits research. 

There is also a significant opportunity for national 

and regional studies to use comparable choices to 

enable synthesis and more robust quantifications of 

health co-benefits. Again, increased consistency in 

the health co-benefits considered, the concentrationrelationships 

improve com 

and bring together emissions· focused and 

bd>avior-tiJCusc·d approaches (figure 2). ln addition, 

modelers can develop a limited set of scenarios and 

time slices to explore as part of their of 

est to address the study questions. \Ve recommend that 

a few scenarios be included in all studies V>ith a view 

toward synthesis and meta-analysis. 

jections done thrOLlgh 2020 should focus at on 

2030 and projections done through 2040 should focus 

at least on 2050, and all projections should include 

a normativc scenario that combines marker scenarios 

RCP 2.6 and the sustainability pathway in the Shared 

Socio-economic Pathways (SSPI) (O'Neil! eta/2017), 

as this Vl"ill be the closest to achieving the Paris 

underlying driYers (e.g. SRES Bland SRES A2, respecti-,.rJy). :\high cmi:-sion:: ::ccnJrin such as RCP 0 0 or 

8.5 and Regional RiYalry in the SSPs (SSP3) would he a 
208 

llJOOt 

scenario with population :md high emission 

growth that used as a counterfactual for projections past 2050. Using similar temporal and spatial 

scales as employed in integrated assessment models 

with the health co -benefits 

Achieving this could be 

by partncring vvith the integrated assessment model·· 

ers. Doing so would increase the complexity of health 

co-benefits analyses and their potential usefulness. 

Another increasing area ofinterest is to understand 

the equity dimensions of mitigation policies ;md to 

whom the health co-benefit"iaccruc.ltis easy to imagine 

omllit11 miti2ati<m policies could provide 

to communities duwnwind of coalif vehiculartraffic is reduced. ReducingYehicleemission 

standards would further benefit these communities. 

igation also \Vottld have positive (or negative) 

equity din1ensions. 

These recommendations are within the context that 

model diversity itself has benefits (Ebi and Rocklov 

20 14). There is broad diversity across integrated assessconclusions of the NIH, its component Jnstitutcs and 

financial interests. 

ORCIDiDS 

Jonathan J Buonocore https://orcid.org/OOOO·OOOl 

/'27(H~92X 

Kristie L Ebi ' https:/ iorcid.orgiOOOO 0003 ·~7 46· H236 

Roni \\eff 'https://orcid.org/0000 0002·0010-2635 

Rebecca Saari '-' https:/ /orcid.org/0000-000 t -7g9SJ7558 

References 

ment models used to estimate the costs of mitigation, Balbus I l\L Greenblatt J B, Chari R, :-..'lil!stein D and Ebi K L 20H 

but also sufficient consistency that model results can be 

compared and summed in some instances. 

As the literature demonstrates, mitigation policies 

are Ye!J' likely a 'win ·'i.rin," improving health in the 

shmter term while dccn'asing the magnitude of climate 

health risks later in the century. Takhca.lth co-benefits into account provides more 

comprehensive estimates of mitigation policy costs and 

benefits, and mayincrea~c the political feasibility of mitigation policies because these health benefits arc often 

local, and immediate, before 

Leverestimates of nearer-term, more proximal health 

of climate mitigation policies and technologies is an opportunity to support policy uptake and Hmv<:'n Sand Zwi A B 2005 Pathways L11 eviJencc·illfonncJ policy 

implementation. 

Acknowledgments 

\Nc \'muld like to thank Rcbeca de Buen and Grace 

Sheeran for their help with the literature reviews. \Ve 

also want to thank the in the University 

Health Benefits of 

ments and suggestions from two anonymous re\'iewers. 

This article is the work product of an employee of the 

National fnstitutesofHcalth (NIH), however, the statement:., opinions or condusio1s contai;1cd therein do 

not necessarily represent the statements, opinions or 

t5 

200) Pr.:m,·nopausal !~ulntak<.' 

and risk of breast ancer }. Natl Canrcr l11st, 95 lll/9··8:; 

(;ollen A J ct a/2017 Estimate~ and 25 ycm 

Crawfmd-Hrown D, <~hen P ( , Shi H C and Chao C \\' 2013 
209 

IOPPublish1ng Environ.Rr5. Lett. 12(?017) 113001 

transport in European cities: 

co-benefits Environ. Res. Lett. 7 0-f~lH:'. 

Cross/\ J, Lcitzmann :vr F, Gai! M H, Ho!lcnlwck A R, Schat7kin A 

and Sinha R 2007 A nn>'n•octi" ""d' 

meat intake in relation 

context oflong·tcrm climate mitigation goals Springaplus 5 

](}20 

(;arcia-Mcncnde7 F, Saari R K, Monier Eand Selin~ E 2015 t.TS 

- K;\!Changetal 

Kaluza J, \Yolk A Jnd r arsson SC 2012 Red mC'at consumption 

and risk of stroke Stroke 43 ~JS(r-6{) 

Kelly J, Makar P A and Plummer D A 2012 

Nutr.Diet.22lil7-99 

731\0-B :Vbcmillan 1\, Connor J, Witten K, Kearns R, Rees D and \\'oodward 

A 2014 The societal costs and bendlts of commuter bicycling 

Environmental impact of dietary change: a systematic rrviC\v 

f. Clean. Prod. 91 l- ll Inventory 1991J.-2015 (\Vdlington) (11"\\W mfc.gm t.m/nock/ 

23J~H/) 

!99-212 

J')l 401 

Hco J, Adams P j and (~ao H 0 2016 Reduced-form modeling of 

O'Neil! B C et al2017 The roads ahead: narratin·s tOr shared 

Pan A, Sun Q, Bernstein A ,\4, Schulze M B, Mamon j E Willett \V 

C and Hu F B 2011 Rdme<<t co';omnptioP 

Adv. 1\'ulr. 70-ll r...: 

!6 
210 

IOPPubl:shing !UOOJ 

Rao S ct a/20 16 :\ multi-model assessment of the co· hcndits of 

climate mitigation for globill airqtwlity Environ. Res. Lett. 11 

12-WD 

Saari R 1\:, Selin N E, Rausch S and Thompson T ?vl 201 S A 

stlf-consi~tent method to a~~<.:s~ air quality en-benefits 

from l ·s climate policies]. Air H'aste l'vfanage. Assoc. 65 

7HN 

Sabel C E et al2016 

Clin. Nutr. 66/'JO. j 

232 6\) 

:'>62 ·71 

17 

!.:: !\I Chanp;rtal 

.j\.((1-:'i] 

Springrnann \.L :\hson D'Croz D, Robinson S, W1dw K, c;odfray 

p 2017 

Mal. 13..:100.~1!6 

Thompson T \.l, Hausch S, Saari R K and Selin~ E 2016 Air 

~ustainability ;md human hca!th Nature 515 ::>li\-22 

US EPA 20!5 Sources ofGrcenhou~c Gas Emis;,ion;, 

\'aboom B.l'dontgomcry P and BennettS 20\6 What factors 

cmi~sion reductions to 20JO: abatement costs and co bcncfib 

to ozone air quality and human mortality Clim. Change 114 

-ill·()] 

'We~ I J. Srnith S f,Sih:a R i\, Naik \ 

9 

\'I'Hc\ (World Health Assembly) 2008 Climate change hca!th 

S1xty-{nst \Vor!d l-Jealrh Assembly \'\'HA6!.19 (\I'W\1. 

who, ln!lm"~li.Kcntr.cil·rc'nl~/ 100i\rwlp6! /..::n/) ( Access,•& 5 

alternative transport in Adelaide, South "\ustraha Environ_ Int. 

74.281· ')() 
211 

Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II 

Human Health 

Federal Coordinating Lead Authors 

John M. Balbus 

National institute of Environmental Health Sciences 

George Luber 

Centers for Disease Control and Prevention 

Chapter Lead 

Kristie L Ebi 

University of Washington 

Chapter Authors 

Aparna Bole 

University Hospitals Rainbow Babies 

& Children's Hospital, Ohio 

Allison Crimmins 

US Environmental Protection Agency 

Gregory Glass 

University of Florida 

Shubhayu Saha 

Centers for Disease Control and Prevention 

Review Editor 

David D'Onofrio 

Atlanta Regional Commission 

Technical Contributors are listed at the end of the chapter. 

Recommended Citation for Chapter 

Mark M. Shimamoto 

American Geophysical Union 

Juli Trtanj 

National Oceanic and 

Atmospheric Administration 

Jalonne L White-Newsome 

The Kresge Foundation 

Ebi, K.L., J.M. Balbus, G. Luber, A. Bole, A. Crimmins, G. Glass, S. Saba, M.M. Shimamoto, J. Trtanj, and J.L. 

White->lcwsome, 2018: Human Ileal lb. In Impacts. Risks, and Adaptation in the United States: Fow1h National 

CllmuteAssessment, Volume II [Reidmillcr, D.R., C.W.Avcry, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 572-603. 

doi: 10.7930/NCA4.20J8.Cf!14 

On the Web: ~_:;1nca20!8.globalchangc.gov /chapter/health 
212 

Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II 

The health and well-being of Americans are already affected by climate change, with 

the adverse health consequences projected to worsen with additional climate change. 

Climate change affects human health by altering exposures to heat waves, floods, 

droughts, and other extreme events; vector-, food- and waterborne infectious diseases: 

changes in the quality and safety of air, food, and water; and stresses to mental health 

and well-being. 

People and communities are differentially exposed to hazards and disproportionately 

affected by climate-related health risks. Populations experiencing greater health risks 

include children, older adults, low-income communities, and some communities of color. 

Proactive adaptation policies and programs reduce the risks and impacts from 

climate-sensitive health outcomes and from disruptions in healthcare services. 

Additional benefits to health arise from explicitly accounting for climate change risks in 

infrastructure planning and urban design. 
213 

Executive 

imatf,-nclated changes in weather patterns 

and associated changes in air, water, food, and 

environment are affecting the health and 

well--being of the American people, causing 

injuries, illnesses, and death. lnCl·casing 

temperatures, increases in the frequency 

intensity of heat waves (since the 1960s), 

changes in precipitation patterns (especially 

in heavy precipitation), and sea 

can affect our health through multiple 

Changes in weather and climate 

can air and water quality; affect the 

geographic range, seasonality, and intensity 

of transmission of infectious diseases through 

food, water, and disease-carrying vectors (such 

mosquitoes and ticks); and 

that affect mental health and well-being. 

Changing weather patterns also interact with 

demographic and socioeconomic factors, as 

well underlying health trends, to influence 

of the consequences of climate 

for individuals and communities. 

While all Americans are at risk of experiencing 

adverse dimate·~related health outcomes) some 

populations are dispropori.ionately vulnerable. 

The risks of climate for human health 

expected to increase in the future, with the 

of the resulting impacts dependent on 

the effectiveness of adaptation efforts and on 

the magnitude and pattern of future climate 

change. lnclividuals, communities, public health 

US_ Glob<ll Cllenge flesNlrch Prog1am 541 

14 I Human Health 

clr<nortrnn'o't" health-related organizations 

and facilities, and others taking action to 

reduce health vulnerability to current 

change and to increase resilience to the 

projected in coming decades. 

The health benefits of reducing greenhouse gas 

emissions could result in economic benefits 

of hundreds of billions of dollars each year by 

the end of the century. Annual health impacts 

and health-related costs are projected to he 

approximately 50% lower a lower 

nario (RCP4.5) compared to higher scenario 

(RCP8.5). These estimates would be even 

larger if they included the benefits of health 

outcomes are difficult to quantify, snch 

avoided mental health impacts or long-term 

physica I health impacts. 
214 

14 I Human Health 

Vulnerable Populations 

to adverse climate~related health threats are shown along with adaptation 

d;"""''nrlionote impacts. When the full range of threats from climate change 

these groups are most sensitive, and have the least 

respond to text indicates the risks faced by those 

be taken to reduce those risks. From Figure 14.2 (Source: EPA). 

U.S. Global Change Research Prograrn 542 fourth National Climate Assessmf>nt 
215 

A comprehensive assessment of the impacts of 

climate change on human health in the United 

States concluded that climate change exacerbates existing climate-sensitive health threats 

and creates new challenges, exposing more 

people in more places to hazardous weather 

and climate conditions.' This chapter builds 

on that assessment and considers the extent 

to which modifying current, or implementing 

new, health system responses could prepare 

for and manage these risks. Please see Chapter 

13: Air Quality for a discussion of the health 

impacts associated with air quality, including 

ozone, wildfires, and aeroallergens. 

14 1 Human Health 

The health and well-being of Americans 

are already affected by climate change, 

with the adverse health consequences 

projected to worsen with additional climate 

change. Climate change affects human 

health by altering exposures to heat 

waves, floods, droughts, and other extreme 

events; vector-, food- and waterborne 

infectious diseases; changes in the quality 

and safety of air, food, and water; and 

stresses to mental health and well-being. 

Climate Change and Health 

lLS. Global Change Research Program 543 Fourth National Climate Assessm~nt 
216 

The first paragraph in each of the following 

sections summarizes findings of the 2016 

U.S. Climate and Health Assessment,' and the 

remainder of each section assesses findings 

from newly published research. 

Extreme Events 

More frequent andjor more intense extreme 

events, including drought, wildfires, heavy 

rainfall, floods, storms, and storm surge, are 

expected to adversely affect population health.3 

These events can exacerbate underlying 

medical conditions, increase stress, and lead 

to adverse mental health effects." Further, 

extreme weather and climate events can 

disrupt critical public health, healthcare, and 

related systems in ways that can adversely 

affect health long after the event." 

Recent research improves identification of 

vulnerable population groups during and after 

an extreme event,5 including their geographic 

location and needs (e.g. Bathi and Das 2016, 

Gotanda et al. 2015, Greenstein et al. 20166

·

7

·

8

). 

U.S. Global Change Hesearch Progrum 544 

14 I Human Health 

For example. the 2017 hurricane season 

highlighted the unique vulnerabilities of populations residing in Puerto Rico, the U.S. Virgin 

Islands, and other Caribhean islands (Ch. 20: 

U.S. Caribbean, Box 20.1)." 

Temperature Extremes 

High temperatures in the summer are conclusively linked to an increased risk of a range 

of illnesses and death, particularly among 

older adults, pregnant women, and children'' 

People living in urban areas may experience 

higher ambient temperatures because of the 

additional heat associated with urban heat 

islands, exacerbating heat-related risks. 19 With 

continued warming, increases in heat-related 

deaths are projected to outweigh reductions in 

cold-related deaths in most regions. 18 

Analyses of hospital admissions, emergency 

room visits, or emergency medical services 

calls show that hot days are associated with an 

increase in heat-related illnesses,20•

21 inclnding 

cardiovascular and respiratory complications," 

Fourth Nat]onn! Climate As!:>essment 
217 

renal failure, 23 electrolyte imbalance, kidney 

stones,24 negative impacts on fetal healtb, 25 

and preterm birth.20 Risks vary across rq,>ions 

(Cb. 18: Northeast, Box 18.3)." Health risks 

may be higher earlier in the summer season 

when populations are less accustomed to 

experiencing elevated temperatures, and 

different outcomes are observed at different 

levels of high temperature. 28·

29 See Chapter 13: 

Air Quality for a discussion of the associations 

between temperature, air quality, and adverse 

health outcomes. 

Vector-Borne Diseases 

Climate change is expected to alter the 

geographic range, seasonal distribution, and 

abundance of disease vectors, exposing more 

people in North America to ticks that carry 

Lyme disease or other bacterial and viral 

agents, and to mosquitoes that transmit West 

Nile, chikungunya, dengue, and Zika viruses30-'''·32 Changing weather patterns interact 

with other factors, including bow pathogens 

adapt and change, changing ecosystems and 

land use, demographics, human behavior, and 

the status of public health infrastructure and 

management.33•

34 

El Nino events and other episodes of variable 

weather patterns may indicate the extent to 

which the risk of infectious disease transmission could increase with additional climate 

change.3::l,35,36 

Increased temperatures and more frequent 

and intense extreme precipitation events can 

create conditions that favor the movement of 

vector-borne diseases into new geographic 

regions (e.g., Belova et al. 2017, Monaghan 

et al. 2016, Ogden and Lindsay 201631•

37-38). At 

the same time, very high temperatures may 

reduce transmission risk for some diseases.39•

40 

Economic development also may substantially 

reduce transmission risk by reducing contacts 

with vector populations:" In the absence of 

U.S. Global Change Research Program 545 

14 I Human Health 

adaptation, exposure to the mosquito Aedes 

aegypti, which can transmit dengue, Zika, chikungunya, and yellow fever viruses, is projected 

to increase by the end of the century due to 

climatic, demographic, and socioeconomic 

changes, with some of the largest increases 

projected to occur in North America.31-'12 Similarly, changes in temperature may influence 

the distribution and abundance of tick species 

that transmit common patbogens.38·

42•43 

Water-Related Illnesses and Death 

Increasing water temperatures associated 

with climate change are projected to alter the 

seasonality of growth and the geographic range 

of harmful algae and coastal pathogens, and 

runoff from more frequent and intense rainfall 

is projected to increasingly compromise recreational waters and sources of drinking water 

through increased introductions of pathogens 

and toxic algal blooms.49,so,sJ,sz,s3.s4 

Projected increases in extreme precipitation 

and flooding, combined with inadequate water 

and sewer infrastructure, can contribute 

to viral and bacterial contamination from 

f"ourth National Cllmflte Assessment 
218 

combined sewage overflows and a lack of 

access to potable drinking water, increasing 

exposure to pathogens that lead to gastrointestinal illness. 55·

56•

57·

58·

59 The relationship 

between precipitation and temperature-driven 

transmission of waterborne diseases is 

complex and site-specific, with, for example, 

some areas finding increased numbers of 

cases associated with excessive rainfall and 

others finding stronger associations with 

drought."""·62·

63·

64•

65 Heavy rainfall, flooding, and 

high temperatures have heen linked to increases in diarrheal disease62·

64·

66·

67 and can increase 

other bacterial and parasitic infections such 

as leptospirosis and cryptosporidiosis.'5

·" 

Increases in air temperatures and heat waves 

are expected to increase temperature-sensitive 

marine pathogens such as Vibrio.oo,69,70,71 

Food Safety and Nutrition 

Climate change, including rising temperatures 

and changes in weather extremes, is projected 

to adversely affect food security by altering 

exposures to certain pathogens and toxins (for 

example, Salmonella, CampyLohacter, Vibrio 

parahaemolytic11s in raw oysters, and mycotoxigenic fungi)72 

Climate change, including changes in some 

extreme weather and climate events, can 

adversely affect global and U.S. food security 

by, for example, threatening food safety,"'""4

·

75 

disrupting food availability, decreasing access to 

food~ and increasing food prices?6·77.78·

79,

80·

81·

82 Food 

quality also is expected to be affected by rising 

C02 concentrations that decrease dietary iron," 

zinc,84 protein,85 and other macro- and micronutrients in crops86P 88 and seafood. ss,go Projected 

changes in carbon dioxide concentrations and 

climate change could diminish expected gains in 

global nutrition; however, any impact on human 

health will depend on the many other drivers 

of global food security and factors such as food 

chain management, human hehavior, and food 

safety governance.91•

92·

93,r14 

U_S, Global Change Research Program 546 

14 I Human Health 

Mental Health 

Mental health consequences, ranging from 

minimal stress and distress symptoms to 

clinical disorders, such as anxiety, depression, 

post-traumatic stress, and suicidality, can res111t 

from exposures to short-lived or prolonged 

climate- or weather-related events and their 

health consequences.' These mental health 

impacts can interact with other health, social, 

and environmental stressors to diminish an 

individual's well-being. Some groups are more 

vulnerable than others, including the elderly, 

pregnant women, people with preexisting mental 

illness, the economically disadvantaged, tribal and 

Indigenous communities, and first responders.' 

Individuals whose households experienced a 

flood or risk of flood report higher levels of 

depression and anxiety, and these impacts can 

persist several years after the event. 95,

96,

97,

98 Disasters present a heavy burden on the mental health 

of children when there is forced displacement 

from their home or a loss of family and community stability.99 lncreascd use of alcohol and 

tobacco are common following disasters as well 

as droughts. 15•

16·

100·

101 Higher temperatures can lead 

to an increase in aggressive behaviors, including 

homicide.102•

103 Social cohesion, good coping skills, 

and preemptive disaster planning are examples of 

adaptive measures that can help reduce the risk 

of prolonged psychological impacts.102•

1

o4.ws 

Key Message 2 

People and communities are differentially exposed to hazards and disproportionately affected by climate-related 

health risks. Populations experiencing 

greater health risks include children, 

older adults, low-income communities, 

and some communities of color. 

Fourth National C!imnte Assessment 
219 

The health impacts of climate change are not 

felt equally, and some populations are at higher 

risk than others.w6 Low-income communities 

and some communities of color are often 

already overburdened with poor environmental 

conditions and are disproportionately affected 

by, and less resilient to, tbc health impacts of 

climate change-"'6,

107,108,109.110 The health risks 

of climate change are expected to compound 

existing health issues in Native American and 

Alaska Native communities, in part due to the 

loss of traditional foods and practices, the 

mental stress from permanent community 

displacement, increased injuries from lack of 

permafrost, storm damage and flooding, smoke 

inhalation, damage to water and sanitation 

systems, decreased food security, and new 

14 I Human Health 

infectious diseases (Ch, 15: Tribes; Ch, 26: 

Alaska). m,112 

Across all climate risks, children, older adults, 

low-income communities, some communities 

of color, and those experiencing discrimination 

are disproportionately affected by extreme 

weather and climate events, partially because 

they are often excluded in planning processesY3 Other populations might experience 

increased climate risks due to a combination 

of exposure and sensitivity, such as outdoor 

workers, communities disproportionately 

burdened by poor environmental quality, and 

some communities in the rural Southeastern 

United States (Ch, !9: Southeast).'"''l5JI6 

Vulnerable Populations 

sensitive, and have the 

threats. text indicates the risks faced by 

those communities, to reduce those risks. Source: EPA 

U,S. G1oba1 Change Research Program 547 Fourth National Chmate Assr;s!'>ment 
220 

Additional populations with increased health 

and social vulnerability typically have less 

access to information, resources, institutions, 

and other factors to prepare for and avoid 

the health risks of climate change. Some of 

these communities include poor people in 

high-income regions, minority groups, women, 

pregnant women, those experiencing discrimination, children under five, persons with physical and mental illness, persons with physical 

and cognitive disabilities, the homeless, 

those living alone, Indigenous people, people 

displaced because of weather and climate, the 

socially isolated, poorly planned communities, 

the disenfranchised, those with less access to 

healthcare, the uninsured and underinsured, 

those living in inadequate housing, and those 

with limited financial resources to rebound 

from disasters.107•

10"·117•

118 Figure 14.2 depicts 

some of the populations vulnerable to weather, 

climate, and climate change. 

Building Resilient Communities 

Projections of climate change-related changes 

in the incidence of adverse health outcomes, 

associated treatment costs, and health 

disparities can promote understanding of 

the ethical and human rights dimensions of 

climate change, including the disproportionate 

share of climate-related risk experienced by 

socially marginalized and poor popnlations. 

Such projections can also highlight options 

to increase population resilience. H9J

20•

121 The 

ability of a community to anticipate, plan for, 

and reduce impacts is enhanced when these 

efforts build on other environmental and 

social programs directed at sustainably and 

equitably addressing human needs. 122 Resilience 

is enhanced by community-driven planning 

processes where residents of vnlnerahle and 

impacted communities define for themselves 

the complex climate challenges they face and 

the climate solutions most relevant to their 

unique vulncrabilitics.110•

12"·1

".l25 A flood-related 

disaster in central Appalachia in spring 2013 

lLS. Global Change Research Program 548 

14 I Human Health 

highlighted how community-based coping 

strategies related to faith and spirituality, 

cultural values and heritage, and social support 

can enhance resilience post-disaster.126 

Communities in Louisiana and New Jersey, 

for example, are already experiencing a host 

of negative environmental exposures coupled 

with extreme coastal and inland flooding. Language-appropriate educational campaigns can 

highlight the effectiveness of ecological protective measures (such as restoring marshes 

and dunes to prevent or reduce surge flooding) 

for increasing resilience. Resilience also can he 

built by creating institutional readiness, recognizing the importance of resident mobility 

(geographic movements at various scales such 

as commuting, migration, and evacuation), 

acknowledging the importance and support 

of social networks (such as family, church, and 

community), and facilitating adaptation to 

changing conditions. 127J28 

Key Message 3 

' ~l:laetafi!lfll Be(:luces Risl<s an(:( 

lm!;lrov:es lflealtl'i 

Proactive adaptation policies and pro· 

grams reduce the risks and impacts 

from climate-sensitive health outcomes 

and from disruptions in healthcare services. Additional benefits to health arise 

from explicitly accounting for climate 

change risks in infrastructure planning 

and urban design. 

Adapting to the Health Risks of 

Climate Change 

Individuals, communities, public health departments, healthcare facilities, organizations, and 

others are taking action to rcdLrcc health and 

social vulnerabilities to current climate change 

and to increase resilience to the risks projected 

in coming cleeades.129 

Fourth National Climate Assessment 
221 

Examples of state-level adaptation actions 

include conducting vulnerability and adaptation assessments, developing comprehensive 

response plans (for example, extreme heat),110·

130 

climate-proofing healthcare infrastructure, 

and implementing integrated surveillance of 

climate-sensitive infectious disease (for example, 

Lyme disease), Incorporating short-term to 

seasonal forecasts into public health programs 

and activities can protect population health today 

and under a warming climate.'" Over decades or 

longer, emergency preparedness and disaster risk 

reduction planning can hencfit from incorporating climate projections to ensure communities 

are prepared for changing weather patterns."" 

Local efforts include altering urban design (for 

example, by using cool roofs, tree shades, and 

green walkways) and improving water management (for example, via desalination plants or 

watershed protection). These can provide healt11 

and social justice benefits, elicit neighborhood 

participation, and increase resilience for specific 

populations, such as outdoor workers, wwz,m 

Adaptation options at multiple scales are 

needed to prepare for and manage health risks 

in a changing climate, For example, options to 

manage heat-related mortality include individual 

acclimatization (the process of adjusting to higher 

temperatures) as well as protective measures, 

such as heat wave early wamings,134 air conditioning at home, cooling sheltcrs,135 green space 

in the neighborhood,"15·'"' and resilient power 

U.S. Global Change Research Pronram 549 

14 I Human Health 

grids to avoid power outages during extreme 

weather cvcnts.138 

Early warning and response systems can protect 

population health now and provide a basis for 

more effective adaptation to future climate.m1J

40,H! 

Improvement~ in forecasting weather and climate 

conditions and in environmental observation 

systems, in combination with social factors, can 

provide inforn1ation on when and where changing weather pattems could result in increasing 

numbers of eases of, for example, heat stress or 

an infectious disease.31A5,

142.143J44 Such early warning 

systems can provide more time to pre-position 

resources and implement control programs, 

thereby preventing adverse health outcomes. 

For example, to help communities prepare for 

extreme heat, federal agencies are partnering 

with local entities to bring together stakeholders 

across the fields of public health, meteorology, 

emergency management, and policy to develop 

useful infonnation systems that can prevent 

heat-related illnesses and deaths,145 Adaptation 

efforts outside the health sector can have health 

benefits when, tor example, infrastructure 

planning is designed to cool ambient tempera, 

tures and attenuate storm water nmoff46•

147 and 

when interagency planning initiatives involve 

transportation, ecosystem management, urban 

planning, and water management148 Adaptation 

measures developed and deployed in other 

sectors can harm population health if they arc 

developed and implemented without taking 

health into consideration, 

fourth National Climate Assessment 
222 

14 I Human Health 

Hurricane Flooding 

1111 Category 1 11!111 Category 2 a Category 3 Cl:l Category 4 D Category 5 

U.S. Global Change Research Progr<un 550 Fourth Nation-a! C!!mnte Assessment 
223 

Key Message 4 

~e<Ju~ing 6ree£tftouse ~as il!Emissi!iln 

ftesults itt :l§l~ltll an~ BcQnomm 

Selilefits 

Reducing greenhouse gas emissions 

would benefit the health of Americans 

in the near and long term. By the end 

of this century, thousands of American 

lives could be saved and hundreds 

of billions of dollars in health-related 

economic benefits gained each year 

under a pathway of lower greenhouse 

gas emissions. 

Reducing greenhouse gas emissions (Ch. 29: 

Mitigation) would benefit the health of Americans in the near and long term. 1

·

155 Adverse 

health effects attributed to climate change 

have many potential economic and social 

costs, including medical expenses, caregiving 

services, or lost prodnctivity, as well as costs 

that are harder to quantify, such as those 

associated with pain, suffering, inconvenience, 

or reduced enjoyment of leisure activities."" 

These health burdens are typically horne by 

the affected individual as well as family, friends, 

employers, communities, and insurance or 

assistance programs. 

Under a lower scenario (RCP4.5) by the end 

of this century, thousands of lives could be 

U.S. Global Change Research Program 551 

14 1 Human Health 

saved and hundreds of billions of dollars of 

health-related costs could be avoided compared to a higher scenario (RCP8.5).157 Annual 

health impacts (including from temperature 

extremes, poor air quality, and vector-borne 

diseases) and health-related costs are projected to he approximately 50% less under a 

lower scenario (RCP4.5) than under a higher 

scenario (RCPS.S) (methods are summarized in 

Traceable Accounts) (see also Ch. 13: Air Quality). :l7J:>7,15s,159,t6o,Jel,ltl2.!n3,164,165,16ti,l67 'l'hc projected 

lives saved and economic benefits are likely to 

underestimate the true value because they do 

not include benefits of impacts that arc difficult to quantify, such as mental health or longterm health impacts (see the Scenario Products 

Section in App. 3 for more on scenarios). 

Temperature-Related Mortality 

The pr~jccted increase in the annual number of 

heat wave days is substantially reduced under 

a lower scenario (RCP4.5) compared to a higher 

scenario (RCP8.5), reducing heat wave intensities16l.108 and resulting in fewer high-mortality heat 

wavesw2

·

166 without considering adaptation (Figure 

14.4). In 49 large cities in the United States, changes in extreme hot and extreme cold temperatures 

are projected to result in more than 9,000 additional premature deaths per year under a higher 

scenario by the end of the century, although 

this numher would be lower if considering 

acclimatization or other adaptations (for example, 

increased use of air conditioning). Under a lower 

Fourth National Climate Assessnwnt 
224 

14 I Human Health 

Projected Change in Annual Extreme Temperature Mortality 

Lower Scenario 

(RCP4.5) 

Higher Scenario 

(RCP8.5) 

Change in Mortality Rate 

(deaths per 100,000 people) 

.10.1-12.0 

.8.1-10.0 

G6.1-8.0 

®4.1-8.0 

0 2.1-4.0 

0 0.0-2.0 

Figure 14.4: The maps show estimated changes In annual net mortality due to extremely hot and cold days In 49 U.S. cities for 

2080-2099 as compared to 1989-2000. Across these cities, the change in mortality is projected to be an additiona19,300 deaths 

each year under a higher scenario (RCP8.5) and 3,900 deaths each year under a lower scenario {RCP4.5). Assuming a future 

in which the human health response to extreme temperatures in all 49 cities was equal to that of Dallas today (for example, as 

a result of availability of air conditioning or physiological adaptation) results in an approximate 50% reduction in these mortality 

estimates. For example, in Atlanta, an additional 349 people are projected to die from extreme temperatures each year by the 

end of centuty under RCP8.5. Assuming residents of Atlanta in 2090 have the adaptive capacity of Dallas residents today, this 

number is reduced to 128 additional deaths per year. Cities without circles should not be interpreted as having no extreme 

temperature impact. Data not available for the U.S. Caribbean, Alaska, or Hawai'i & U.S.-Affi!iated Pacific Islands regions. 

Source: adapted from EPA2017. 151 

scenario, more than half of these deaths could be 

avoided each year. Annual damages associated 

with the additional extreme temperature-related 

deaths in 2090 were projected to be $140 billion 

(in 2015 dollars) under a higher scenario (RCP8.5) 

and $60 billion under a lower scenario (RCP4.5). 157 

labor Productivity 

Under a higher scenario (RCP8.5), almost 

two billion labor hours are projected to be 

lost annually hy 2090 from the impacts of 

temperature extremes, costing an estimated 

$160 billion in lost wages (in 2015 dollars) (Cit 

1: Overview, Figure 121).157·

157•

169 States within the 

Southeast and Southern Great Plains regions 

are projected to experience higher impacts, 

with labor productivity in jobs with greater 

exposure to heat projected to decline hy 3% 

(Ch. 19: Southcast).164•

170 Some counties in Texas 

and Florida are projected to experience more 

than 6% losses in annual labor hours by the 

end of the century. 137,

160 

Infectious Diseases 

Annual national cases of West Nile ncuroinvasive disease are projected to more than double 

U_$_ Global Change Research Progrmn 552 

by 2050 due to increasing temperatures, 

among other factors, 30·

171 resulting in approximately $1 billion per year in hospitalization 

costs and premature deaths under a higher 

scenario (RCP8.5; in 2015 dollars)." In this same 

scenario, an additional 3,300 cases and $3.3 

billion in costs (in 2015 dollars) are projected 

each year by the end of the century. Approximately half of these cases and costs would be 

avoided under a lower scenario (RCP4.5)."·1

57 

Water Quality 

By the end of the century, warming under 

a higher scenario (RCP8.5) is projected to 

increase the length of time recreational waters 

have concentrations of harmful algal blooms 

(cyanobacteria) above the recommended public 

health threshold by one month annually; these 

bacteria can produce a range of toxins that 

can cause gastrointestinal illness, neurological 

disorders, and other illnesses. 157•

165 The increase 

in the number of days where recreational 

waters pose this health risk is almost halved 

under a lower scenario (RCP4.5). 

Fourth National Climate Assessment 
225 

Acknowledgments 

Technical Contributor 

Stasia Widerynski 

Centers for Disease Control and Prevention 

USGCRP Coordinators 

Ashley Bieniek-Tobasco 

Health Program Coordinator 

Sarah Zerbonne 

Adaptation and Decision Science Coordinator 

Natalie Bennett 

Adaptation and Assessment Analyst 

Christopher W. Avery 

Senior Manager 

Opening Image Credit 

Algal bloom: NOAA Great Lakes Environmental 

Research Laboratory. 

U.S Global Change Research Program 

14 I Human Health 

553 Fourth National Climate Assessment 
226 

141 Human Health Traceable Accounts 

Traceable Accounts 

Process Description 

The chapter evaluated the scientific evidence of the health risks of climate change, focusing 

primarily on the literature published since the cutoff date (approximately fall 2015) of the U.S. 

Climate and Health Assessment.' A comprehensive literature search was performed by federal 

contractors in December 2016 for studies published since January 1, 2014, using PubMcd, Scopus, 

and Wch of Science. An Excel file containing 2,477 peer-reviewed studies was provided to the 

author team for it to consider in this assessment. In addition to the literature review, the authors 

considered recommended studies submitted in comments by the public, the National Academics 

of Sciences, Engineering, and Medicine, and federal agencies. The focus of the literature was on 

health risks in the United States, with limited citations from other countries providing insights 

into risks Americans are or will likely face with climate change. A full description of the search 

strategy can be found at https://www.nichs.nih.gov /CCHH .Search~ Strategy NCA4 508.pdf. 

The chapter authors were chosen based on their expertise in the health risks of climate change. 

Teleconferences were held with interested researchers and practitioners in climate change and 

health and with authors in other chapters of this Fourth National Climate Assessment (NCA4). 

The U.S. Climate and Health Assessment' did not consider adaptation or mitigation, including 

ecooomic costs and benefits, so the literature cited includes research from earlier years where 

additional information was relevant to this assessment. 

For NCA4, Air Quality was added as a report chapter. Therefore, while Key Messages in this Health 

chapter include consideration of threats to human health from worsened air quality, the assessment of these risks and impacts are covered in Chapter 13: Air Quality. Similarly, co-benefits of 

reducing greenhouse gas emissions are covered in the Air Quality chapter. 

Key Message 1 

Climate Change Affects the Health of All Americans 

The health and well~being of Americans are already affected by climate change (very high 

confidence), with the adverse health consequences projected to worsen with additional climate 

change (likely, high confidence). Climate change affects human health by altering exposures to 

heat waves, floods, droughts, and other extreme events; vector~, food~ and waterborne infectious 

diseases; changes in the quality and safety of air, food, and water; and stresses to mental health 

and well~being. 

Description of evidence base 

Multiple lines of evidence demonstrate statistically significant associations between temperature, 

precipitation, and other variahles and adverse climate-sensitive health outcomes, indicating 

sensitivity to weather patterns-' These lines of evidence also demonstrate that vulnerability varies 

across sub-populations and geographic areas; populations with higher vulnerability include poor 

people in high-income regions, minority groups, women, children, the disabled, those living alone, 

those with poor health status, Indigenous people, older adults, outdoor workers, people displaced 

because of weather and climate, low-income residents that lack a social network, poorly planned 

US. Global Change Research Program 554 Fourth National Climate Assessment 
227 

14 1 Human Health - Traceable Accounts 

communities, communities disproportionately burdened by poor environmental quality, the 

disenfranchised, those with less access to healthcare, and those with limited financial resources to 

rebound fron1 disasters. 108.1°9·

110,1lUliun Recent research confirms projections that the magnitude and 

pattern of risks are expected to increase as climate change continues across the century.m 

Major uncertainties 

The role of non-climate factors, including socioeconomic conditions, population characteristics, 

and human behavior, as well as health sector policies and practices, will continue to make it challenging to attribute injuries, illnesses, and deaths to climate change. Inadequate consideration of 

these factors creates uncertainties in projections of the magnitude and pattern of health risks over 

coming decades. Certainty is higher in near-term projections where there is greater understanding of future trends. 

Description of confidence and likelihood 

There is very high confidence that climate change is affecting the health of Americans. There is 

high confidence that climate-related health risks, without additional adaptation and mitigation, will 

likely increase with additional climate change. 

Key Message 2 

Exposure and Resilience Vary Across Populations and Communities 

People and communities are differentially exposed to hazards and disproportionately affected 

by climate-related health risks (high confidence). Populations experiencing greater health risks 

include children, older adults, low-income communities, and some communities of color (high 

confidence). 

Description of evidence base 

Multiple Jines of evidence demonstrate that low-income communities and some communities of 

color are experiencing higher rates of exposure to adverse environmental conditions and social 

conditions that can reduce their resilience to the impacts of climate changewu.w7

·'0 '·'0

'·110 Populations with increased health and social vulnerability typically have Jess access to information, 

resources, institutions, and other factors to prepare for and avoid the health risks of climate 

change.'07.m.rn Across all climate-related health risks, children, older adults, low-income commu-· 

nities, and some communities of color are disproportionately impacted. There is high agreement 

among experts but fewer analyses demonstrating that other populations with increased vulnerability include outdoor workers, communities disproportionately burdened by poor environmental 

quality, communities in the rural southeastern United States, women, pregnant women, those 

experiencing gender discrimination, persons with chronic physical and mental illness, persons 

with various disabilities (such as those affecting mobility, long-term health, sensory perception, 

cognition), the homeless, those living alone, Indigenous people, people displaced because of 

weather and climate, low-income residents who lack a social network, poorly planned communitics, the disenfranchised, those with Jess access to healthcare, the uninsured and underinsured, 

US Global Change Research Program 555 Fourth National Climate Assessment 
228 

14 I Human Health - Traceable Accounts 

those living in inadequate housing, and those with limited financial resources to rebound from 

disasters.1os,w7JOSJ10,1l8 

Adaptation can increase the climate resilience of populations when the process of developing and 

implementing policies and measures includes understanding the ethical and human rights dimensions of climate change, meeting human needs in a sustainable and equitahle way, and engaging 

with representatives of the most impacted communities to assess the challenges they face and to 

define the climate solutions.124 '

25 

Major uncertainties 

The role of non-climate factors, including socioeconomic conditions, discrimination (racial and 

ethnic, gender, persons with disabilities), psychosocial stressors, and the continued challenge to 

measure the cumulative effects of past, present, and future environmental exposures on certain 

people and communities will continue to make it challenging to attribute injuries, illnesses, and 

deaths to climate change. While there is no universal framework for building more resilient 

communities that can address the unique situations across the United States, factors integral to 

community resilience include the importance of social networks, the value of including community voice in the planning and execution of solutions, and the co-benefits of institutional readiness 

to address the physical, health, and social needs of impacted communities. These remain hard to 

quantify.127-"' 

Description of confidence and likelihood 

There is high confidence that climate change is disproportionately affecting the health of children, 

older adults, low-income communities, communities of color, tribal and Indigenous communities, 

and many other distinct populations. And there is higl1 confidence that some of the most vulnerable populations experience greater barriers to accessing resources, information, and tools to 

build resilience, 

Key Message 3 

Adaptation Reduces Risks and Improves Health 

Proactive adaptation policies and programs reduce the risks and impacts from climate-sensitive 

health outcomes and from disruptions in healthcare services (medium confidence). Additional 

benefits to health arise from explicitly accounting for climate change risks in infrastructure 

planning and urban design (/ow confidence). 

Description of evidence base 

Health adaptation is taking place from local to national scalcsY',l"J" Because most of the health 

risks of climate change are also current public health problems, strengthening standard health 

system policies and programs, such as monitoring and surveillance, are expected to be effective in 

the short term in addressing the additional health risks of climate change, Modifications to explicitly incorporate climate change are important to ensure effectiveness as the climate continues to 

change. Incorporating environmentally friendly practices into healthcare and infrastructure can 

promote resilience.'"' 

US. Glob<1l Change Research Program 555 Fourth National Climate Assessment 
229 

141 Human Health- Traceable Accounts 

Major uncertainties 

Overall, while there is considerable evidence of the effectiveness of public health programs, HO,I2<J,>:m 

the effectiveness of policies and programs to reduce future burdens of climate-sensitive health 

outcomes in a changing climate can only be determined over coming decades. The relatively 

short time period of implementing health adaptation programs means uncertainties remain 

about how to best incorporate climate change into existing policies and programs to manage 

climate-sensitive health outcomes and about which interventions will likely be most effective as 

the climate continues to change."'"" For example, heat wave early warning and response systems 

save lives, but it is not clear which components most effectively contribute to morbidity and 

mortality reduction. 

Description of confidence and likelihood 

There is medium confidence that with sufficient human and financial resources, adaptation policies 

and programs can reduce the current burden of climate-sensitive health outcomes."0•

151•

170•

177 There 

is low confidence that the incorporation of health risks into infrastructure and urban planning and 

design will likely decrease climate-sensitive health impacts. 

Key Message 4 

Reducing Greenhouse Gas Emissions Results in Health and Economic Benefits 

Reducing greenhouse gas emissions would benefit the health of Americans in the near and long 

term (high confidence). By the end of this century, thousands of American lives could be saved 

and hundreds of billions of dollars in health-related economic benefits gained each year under a 

pathway of lower greenhouse gas emissions (likely. medium confidence). 

Description of evidence base 

Benefits of mitigation associated with air quality, including co-benefits of reducing greenhouse 

gas emissions, can be found in Chapter 13: Air Quality. This Key Message is consistent with and 

inclusive of those findings. 

Multiple individual lines of evidence across several health topic areas demonstrate significant benefits of greenhouse gas emission reductions, with health impacts and health-related costs reduced 

by approximately half under RCP4.5 compared to RCP8.5 by the end of the century, based on 

comprehensive multisector quantitative analyses of economic impacts projected under consistent 

scenarios (Ch. 13: Air Quality).:nJSIT>SJ'>9J 60·

161·

162·w:untiB:SJil(di"' The economic benefits of greenhouse gas 

emissions reductions to the health sector could be on the order of hundreds of billions of dollars 

annually by the end of the century. 

Hwt: Greenhouse gas emission reductions under RCP4.5 could substantially reduce the annual 

number of heat wave days (for example, by 21 in the Northwest and by 43 in the Southeast by the 

end of the century);'"' the number of high-mortality heat waves; 162-'68 and heat wave intensities."11" 

The EPA (2017)157 estimated city-specific relationships between daily deaths (from all causes) and 

extreme temperatures based on historical observations that were combined with the projections 

of extremely hot and cold days (average of three years centered on 2050 and 2090) using cityspecific extreme temperature thresholds to project future deaths from extreme heat and cold 

U.S. Global Change Research Program 557 Fourth National Climate Assessment 
230 

141 Human Health- Traceable Accounts 

under RCP8.5 and RCP4.5 in five global climate models (GCMs). In 49large U.S. cities, changes 

in extreme temperatures are projected to result in over 9,000 premature deaths per year under 

RCP8.5 by the end of the century without adaptation ($140 billion each year); under RCP4.5, more 

than half these deaths could be avoided annually ($60 billion each year)-"' 

Labor productivity: r !siang et a!. (2017)187 and the EPA (2017)157 estimated the number of labor 

hours from changes in extreme temperatures using dose-response functions for the relationship 

between temperature and labor from GraffZivin and Neidell (2014). 169 Under RCP8.5, almost 2 

billion labor hours are projected to be lost annually by 2090 from the impacts of extreme heat. 

and cold, costing an estimated $160 billion in lost wages. The Southeast16·'·'70 and Southern Plains 

are projected to experience high impacts, with labor productivity in high-risk sectors projected 

to decline by 3%. Some counties in Texas and Florida are projected to experience more than 6% 

losses in annual labor hours by the end of the century.'57.1'0 

Vector-borne d.isease: Belova eta!. (2017)37 and the EPA (2017)137 define health impact functions 

from regional associations between temperatures and the probability of above-average West Nile 

neuroinvasive disease (WNND) incidence to estimate county-level expected WNND incidence 

rates for a 1995 reference period (1986-2005) and two future years (2050: 2040-2059 and 2090: 

2080-2099) using temperature data from five GCMs. Annual national cases of WNND are projected to more than double by 2050 due to increasing temperatures, resulting in approximately $1 

billion per year in hospitalization costs and premature deaths. In 2090, an additional 3,300 annual 

cases are projected under RCP8.5, with $3.3 billion per year in costs. Greenhouse gas emission 

reductions under RCP4.5 could avoid approximately half these cases and costs. 

Water quaUty: Chapra eta!. (2017)"" and the EPA (2017)'57 evaluate the biophysical impacts of climate change on the occurrence of cyanobacterial harmful algal blooms in the contiguous United 

States using models that project rainfall runoff, water demand, water resources systems, water 

quality, and algal growth. In 2090, warming under RCP8.5 is projected to increase the length of 

time that recreational waters have concentrations of harmful algal blooms (cyanobacteria) above 

the recommended public health threshold by one month annually; greenhouse gas emissions 

under RCP4.5 could reduce this by two weeks. 

Food safety and nutrition: There is limited evidence quantifying specific health outcomes or economic impacts of reduced food safety and nutrition. 

Major uncertainties 

While projections consistently indicate that changes in climate are expected to have negative 

hcaltb consequences, quantifying specific health outcomes (for example, number of cases, number 

of premature deaths) remains challenging, as noted in Key Message 1. Economic estimates only 

partially capture and monetize impacts across each health topic area, which means that damage 

costs are likely to be an undervaluation of the actual health impacts that would occur under any 

given scenario. Economic estimates in this chapter do not inclnde costs to the healthcarc system. 

Description of confidence and likelihood 

There is a high confidence t.hat a reduction in greenhouse gas emissions would benefit the health 

of Americans. There is med.ittm confidence that reduced greenhouse gas emissions under RCP4.5 

U.S. Global Change Research Program 558 Fourth National Climate Assessment 
231 

14 I Human Health Traceable Accounts 

compared to RCP8.5 will Likely reduce lost labor hours by almost half and avoid thousands of 

premature deaths and illnesses projected each year from climate impacts on extreme heat, ozone 

and aeroallergen levels (Ch. 13: Air Quality), and West Nile neuroinvasive disease. There is medium 

confidence that the economic henefits of greenhouse gas emissions reductions in the health sector 

could likely he on the order of hundreds of billions of dollars each year by the end of the century. 

Including avoided or reduced benefits of risks that are difficult to quantify, such as mental health 

or long-term health consequences, would increase these estimates. 

US. Global Change Research Program 559 Fourth National Climate Assessment 
232 

References 

tJSGCRP, 2016: The Impacts 

Human Heatth in the 

Assessment. U.S. 

2. Balbus, A. Crimmins, J.L. Gamble. D.R. Easterling, 

KE. Kunkel. S. Saha, and t'.-1.C. Sarofim, 2016: Ch. 1: 

Introduction: Climate change and human health. The 

CLimate on Human Health in the 

A U.S. Global 

wasn11noton. DC, 25-42. 

3. L. Jantarasami, C. Adrianopoli, 

V. Escobar, J. Hess, J. Luvall, 

CP. Garda-Pando, D. Quattrochi, J. Runkle, and 

C.J. Schreck, IlL 2016: Ch. 4: Impacts of extreme 

C\'ents on human health. The Climate 

4. Dodgen, D., D. Donato, N. 

Morganstein, J. Reser, J. Ruzek, 

Shimamoto, K Tart, and R 

Ch. 8: Mental and 

5. Mills, D., R Jones, C. Wobus, J. Ekstrom. L.Jantarasami, 

A. St. Juliana, and A. Crimmins, 2018: 

stratified risk of 

6. 

7. Gotanda, B., J. Fogel, G. Husk, J.M. Levine, r..t 

Peterson, K Baurnlin, and J. llabboushe, 2015: 

U.S. Global Change Research Program 560 

8. 

14 1 Human Health - References 

Department. 

(3), 335-339. 

~t Shultz, J.M., lP. Kossin, J.M. Shepherd, J.M. Ransdell, 

R. Walshe. !. Kelman, and S. Galea, 2018: Risks. health 

corrscrlucne<cs, and response challenges for small11. 

Observations from the 

season. Disaster Medicine 

Prevaredn.ess. 1-13. http:b'dx.doi. 

2014: How unusual 

12. Gorris, M.E., L.A. Cat, C.S. Zender, K.K. Tresedcr, 

and J.T. Randerson, 2018: Coccidioidomycosis 

dynamics in relation to climate in the southwestern 

United States. GeoHeaWt., 2 (1), 6-24. http://dx.doi. 

org/10.1002/2017GH000095 

13. Coopersmith, E.J., J.K Bell, K. Benedict, l Shriber, 

0. McCotter, and M.H. Cosh, 2017: 

14. 

15. FrieL S., H. Berry, H. Dinh, L. O'Brien, and I I.L. Walls, 

2014: The of drought on the association 

and mental health in a 

Fourth National Climate Assessment 
233 

16. 

17. Yusa, A., P. Berry, JJ. B, Bonsai, 

R. Stewart, and R. change, 

drought and human health in Canada. International 

Journal oJ EnLJironmentai Research and Public 

Health, 12 (7). 8359. http://dLCJgi,Q[gL'10.3390/ 

ijerph12Q1983Ci_f) 

18. Sarofim. M.C., S. Saha, M.D. Hawkins, D.M. Mills, 

J. Hess, R. Horton. P. Kinney, J. Schwartz, and A. St. 

19. 

20. 

21. 

Juliana, 2016: Ch. 2: death and 

admissions during heat waves in 1,916 US counties 

for the period from 1999 to 2010 and their effect 

modifiers. Enviromnental Health, 15 (1), 83. _!1~ 

dx.doi.org/ljl.1186/s12940·_016-0l67·3 

22. Gronlund, C.J., A. Zanobetti, G.A. Wellcnius, J.D. 

23. 

Schwartz, and MS O'Neill, 2016: Vulnerability 

to renal, heat and 

during extreme heat 

Change, 136 (3), 631·64S. IJ.l!~~11'.g212!lll.!SL!'l\Lif.. 

sl0584·01§_::.1638·9 

U.S. Global Change Research Program 

14 1 Human Health - References 

24. Ross, M.E., A.M. Vicedo-Cabrera, R.E. Kopp, L 

D.S. Goldfarb, l Pulido, S. Warner, S.L. Furth, 

G.E. Tasian, 2018: Assessment of the combination of 

25. ~go, N.S. and R.M. Horton, 2016: Climate change and 

fetal health: The impacts of exposure to extreme 

temperatures in New York Environmental 

Research, 144, 158-164. '!'ll':L'!:!!',Q212!lll.!!Ll.'!!."~ 

envres.2015.11.016 

26. Ha, S., D. Liu, Y. Zhu, S.S. Kim, S. Sherman, and P. 

Mendola, 2017: Ambient temperature and 

of pregnancies. 

125, 433·459. ~x.doi. 

27. Saha, S., J.W. Brock, A. Vaidyanathan, D.R. 

28. 

and G. Luber, 2015: Spatial variation in hvu•erthermia 

Chowell, 2016: Multiple 

heat-health impacts: New a 

climate. Environmental HeaLth Perspectives, 124, 176-

183. h1~!'://dx.doi.org/10.1289/ehp.1409J.!Q 

29. Sheridan, S.C. and S. Lin, 2014: A.'>scssing variability 

in the impacts of heat on health outcomes in New 

and heat-wave duration. 

11 (4), 512·525. !:!!IRJL92'A>2l,Qlti1()JQQ1L s10393·014 .. 0970:1 

30. Beard, C.R., RJ. Eisen, C.M. 

Hahn, M. Hayden, A.J. 

P.l Schramm, 2016: Ch. 5: Vec"or·bc>rne 

The Impacts of CLimate Change on Human HeaLth in 

the United States: A Scientific Assessment. U.S. Global 

wasntngton, DC, 129·156. 

3t Monaghan, AJ., K.M. Sampson, D.F. Steinhoff, K.C. 

Ernst, K.L. Ebi, R. jones, and M.H. 2016: 

The and 

561 Fourth National Climate Assessment 
234 

32. 40. 

33. 

weather extremes, and vector-borne disease 

14 I Human Health - References 

the impact of temperature on transmission of 

mechtmi;;tic models. 

eOOOSS68. 

outbreaks. Global Health Impacts of Vector-Bonte 4L 

34. 

35. 

Diseases: Workshop Summary. Mack, A, Ed. National 

Academies Press, DC, 202-220. h.~ 

Kitron, 

and their impact 

and control. Trends 

356-367. http://dx.doL 

l Small, S. Britch, J.L. 

2015: Global climate anon1aliesand potential infectious 

42. Springer, Y.P., C.S. Jarnevich, D:T. Barnett, A.J. 

Monaghan, and R.J. 

and future geographic distribution 

tkk, Amblyomma ame1icanum 

the continental United States. American Journal 

Medicine and Hygiene, 93 (4), 875-890. 

disease risks: 2014-2015, PLOS Currents Outbreaks. 43. 

2015. Edition 1. 

36. Fisman, D.N., AR Tuite, and K.A. Brown, 2016: Impact 

of El Nifio Southern Oscillation on infectious disease 

37. Be1ova, A., D. Milts, R. I faJl, AS. Juliana, A Crimmins, 

C Barker, and R. Jones, 2017: of 

44. 

temperature on the future 45. Mui'toz, A.G .. M.C Thomson, A.M. Stewart-lbarra, 

38. 

39. 

neuroinvasive disease in t.he United States. American 

Joumal 6 (1), 75278. h\tp://dx.doh 

U.S. Global Change Research Program 562 

46. Bogoch, U., OJ. Brady, M.U.G. Kraemer, M. German, 

M.I. Creatorc, M.A. Kulkarni, J.S. Brownstein, S.R. 

Mekaru, S.L Hay, E. Groot, A Watts, and K. Khan. 

20lG: 

Fourth National C!imate Assessment 
235 

47. Carninade, C., J. Turner, S. Metelmann, J.C. Hesson, 

M.S.C. T. Solomon, A.P. Morse, and ~t 

Baylis, Global risk model for vector-borne 

transmission of Zika virus reveals the role of El Nifio 

2015. Proceedings of the 

48. 

49. J., L. Jantarasami, J. Brunkard, Collier, J. 

E. Lipp, S. McLellan, S. Moore, H. Paerl, J. 

Ravenscroft, M. Scngco, and J. Thurston, 2016: Ch. 6: 

Climate impacts on water-related illness. The Impacts 

of Climate on Human Health in the United 

States: A U.S. Global 

DC, 157-188. 

50. Jacobs. J., S.K. Moore, K.E. Kunkel, and L. Sun, 

2015: A framework for examining climate-driven 

51. 

and geographic:al 

P. Hoagland. and G. Moschonas, 

nutrients and harmful algae in coastaJ·waters. Journal 

EmJirc>nrrtemtal Management, 146, 206-216. ~ 

52. Glibert, P.M., J. Icarus Allen, Y. Artioli, A. Bensen, 

L. Bouwman, J. Harle, R. Holmes, and J. Holt, 2014: 

53. 

54. J.M., LT. Cousins, C. llalsall, A. Rautio, J. 

E.G. Pacyna, K. Sundseth, S. Wilson, and J. 

Munthe, 2015: Impacts on human health in the Arctic 

to climate-induced changes in contaminant 

rvrHn<f-1C'he EU ArcRisk 

U.S. Global Change Research Program 563 

14 I Human Health - References 

55. Guzman Herrador, B.R., B.F. de Blasio, MacDonald, 

Nichols, B. Sudre, L Vold, J.C. Semenza, and 

2015: Analytical studies 

or 

wMer-c<'l'<tecl waterborne 

infections: A review. Heait.h, 14 (1), 29. 

)>Jlp://dx.doi.org/10.118G/sl2940-015-0014-v 

56. Jagai, J.S .. Q. Li, S. Wade, 

and E.D. Hilborn, 2015: 

gao;trc,intestinal illness 

sewer systems: 

data, 2003-2007. 

Persvec;tw<os, 123 (9), 87:l-879. 

57. Aziz, RK., M.M. Khalifa, and R.R Sharaf, 2015: 

Contaminated water as a source of HeUcobacter 

Advanced 

58. 

59. 

60. Baker-Austin, C., J. Trinancs, N. Gonzalez-Escalona, 

and J. Martinez-Urtaza, 2017: Non-cholera vibrios: 

The microbial 

61. Brooks. KW., J.M. Lazorchak, M.D.A. Howard, M.-V.V. 

Johnson, S.L Morton. D.A.K. Perkins, E.D. Rcavie, G.I. 

Scott, SA Smith, and J.A. Stecvens, 2016: Are harmful 

algal blooms the 

6-13. 

G2, Carlton, LT., A.P. \11/ostcr, P. DeWitt, R.S. Goldstein, 

and K. 2016: A systematic review and mcLaFourth National Climate Assessment 
236 

63. Froelich, B.A. and R.T. 

64. K., A.P. Woster, R.S. Goldstein, and E.J. 

65. 

66. 

2016: Untangling the impacts of climate 

change on waterborne diseases: 1\ 

review of relationships between 

and temperature, rainfaH, flooding, and 

Environmental Science & Technology, 50 

Eisenberg, R. Guerrant, D. 

K. Nelson, 2016: Planning for 

14 1 Human Health - References 

71. Semenza, .T.C., J. Trinancs, W. Lohr, B. Sudrc, M. 

L6fdahl, l Martinez-Urtaza, G.L Nichols, and J. 

of Vibrio 

72. Ziska, L., A. Crimmins, A Auclair, S. DeGrasse, J.F. 

Garofalo, A.S. Khan, r. Loladze, A.A Perez de Le6n, 

A. Showier, J. Thurston, and I. YValls, 2016: Ch, 

Food safety, nutrition, and distribution. The 

Cli.mate on Human HeaLth in the 

A U.S. Global 

wasnll!l~VlHl. DC, 189-216. 

73. Hellberg, R.S. and E. Chu, 2016: Effects of climate 

change on the persistence and dispersal offoodborne 

bacterial in the outdoor environment: A 

Mic:roh•io[cwv. 42 548· 

74. Lake, I.R., 2017: Food-borne disease and climate 

in the United 

need for mechanistic systems-based to 16 (1), 117. 

67. 

68. 

69. 

70. 

study climate 

the 

disease and 

Disaster Medicine and Pubhc 

(6). 797·804. http://dx.doi.orgL\O.JOI7/dmp.2016.73 

B.A., CF. Gaitan, C.A. Stock. V:S. Saba, D. 

and K.W. Dixon, 2017: Potential salinity 

and temperature futures for the Chesapeake Bay 

using a statistical do,,vm;calling 

framework. Estuaries and 

~Q7 /s12237_·017·0280·8 

A.K., R. Hood, R. 

densities in 

Res-ea.rch, 89, 

~~ttres.?Ql-'2.:)19_~ 

U.S. Global Change Research Program 564 

75. 

s12940·017·0327·0 

C. HOller, U. Messelh3usser, A. 

Klein, 2016: Association between 

tenmerature and the occurrence of 

76. Akil, H.A. Ahmad, and R.S. Reddy, 2014: Effects of 

climate on Salmonella infections. Foodborne 

974-980. http://dx.d_o.i 

·n Jiang, C., K.S. Shaw, C.R. 

78. 

C. MitchelL R Murtu:01udde. 

Sapkota, 2015: Climate 

increased risk of sal!norrell•osis 

Evidence for coastal 

A. 

International, 83, 58-62. """-"""""'"""·'···"'l'<L"'c'."-"'LC f_llY!.ll!::.?.QJ~.:..Q§.:QQ~ 

Fourth National Climate Assessment 
237 

79. 

80. 

81. Battilani, P., P, Toscano, I-Ll. Van dcr Fels-Klerx, A. 

14 1 Human Health - References 

87. Martins, L.D., MA Tomaz, F.C Lidon, F.M. DaMatta. 

and lC Ramalho, 2014: Combined effects of elevated 

88. 

Moretti, M. Camardo C. Brera, A. Rortais, 89. 

T. Goumperis, and T. 2016: Aflatoxin B1 

contamination in maize in Europe increases due to 

climate Scientific Reports, 6, 24328. ~ 

82. Brown, M.E., J.M. Antle, P. Backlund, E.R. Carr, W.E. 

Easterling, M.K. Walsh, C. Ammann, W. Attavanich, 

C.R Barrett, M.F. Bellemare, V. Dancheck, C. Funk, K. 90. Climate 

J.S.I. lngram, H. H. Maletta, T. Mata, A. 

M. D. 0 jima, Tebaldi, 

Global Food Security, and 

U.S. Global Research 

91. M., D. Mason-IYCroz, S. Robinson, 

H.C.J. Godfray, D. Gollin, M. Rayner, 

83. P. Bailon, and P. Scarborough, 2016: Global and 

84. 

85. Medek, D.E., l Schwartz, and S.S. 

86. 

Estimated effects of future "'"'A'nht'd" 

concentrations on 

of 

Perspectives, 

b.<.\Q:ij dx.doi.org/ 10.1289 /EHP41 

human nutrition: 

plant stc,ichion·tetry1 

17 (10), 457-461. 

U.S. Global Change Research Program 

health effects of future food 

92. 

93. Ishida, H., S. Kobayashi, S. Kanae, T. Hasegawa, S. 

Y. Shin, K. TakahaBhi, T. Masui, A. Tanaka, 

Y. Honda, 2014: Global-scale and its 

of the health 

undernutrition under the latest 

565 Fourth National Climate Assessment 
238 

14 1 Human Health - References 

95. Lamond, J.E., R.D. Joseph, and D.G. Proverbs, 2015: 103. Mares, D.M. and K.W. Moffett, 2016: Climate 

of factors affecting the long term and intf•rnr•rscmal 

96. 

and deterioration of mental 

households. Environmental 

Research, 140, 325-334. http:b'Jx.doi.org/10.1016/j. 

envres2015.04.008 

97. Munro, A., R.S. Kovats, GJ. Rubin, T.D. Waite, A. Bone, 

and B. Armstrong, 2017: Effect of evacuation and 

displacement on the association between 

and mental health outcomes: A cross-:>ecl:ion•al 

of liK survey data. 

104. How 

New 

105. 0. Gruebner, and S. Galea, 

1 e134-e141. 106. 

98. Waite, T.D., K. Chaintarli, C.R. Beck, A. Bone, R. AmiOt, 

S. Kovats, M. Reacher, B. Armstrong, G. Leonardi, 

G.J. Rubin, and L Oliver, 2017: The 

99. 

health: Crc>Ss-·scc:tional 

on Environmental 

and children's 

http:J/dx.doi. 

B. Flanagan, 

C. Gonzale;,:-Maddux, Hallisey, S. Hutchins, L. 

Jantarasami, S. M. Kiefer, 1 Kolling, K. Lynn, 

R. Morello-Frosch, M.H. 

Watson, K.P. 

Populations of 

107. Forman, F., G. Solomon, R. Morello-Frosch, and K. 

Pezzoli, 2016: 8. Bending the curve and 

the justice and public health. 

hl.tJYLdxd.QiQI1\LlQJ2~L 

100. Fullerton, C.S., J.B.A. McKibben, D.B. Reissman, T. co11abra.67 

Scharf, K.M. Kowalski-Trakofler, J.M. Shultz, and 

R.J. Ursano, 2013: Posttraumatic stress disorder, 108. 

101. Overstreet, S., A. Salloum, and C. Badour, 2010: A 109. Perera, F.P., 2017: Multiple thre-ats to child health from 

school-based assessment of secondary strcssors and fossil fuel combustion: Impacts of air and 

102. 

US Global Change Research Program 

climate Environmental 

hl'ELL 125, 

110. Rudolph, L., S. Gould, and J. Berko, 2015: Climate 

and M. Change, Health, and Equity: Opportunities For 

566 

Action. Public Health Institute, Oakland, CA, 56 pp. 

https:ijbit.ly/2MJllBUg 

rourth National Climate Assessment 
239 

111. Baussan, D., 2015: When You Can't Go Home: 

The Gulf Coast 10 Years after 

112. 

Forest Service, Pacific 

Northwest Station, Portland, OR, 136 pp. 

~://ww~:1~-.:!:g;.Q_~gg.Y/Jieeseerch/pub~.§lllif? 

113. 

114. Kiefer, M., .L Rodriguez-Guzm3.n, J. Watson, B. van 

Wendel de Joode, D. and AS. da Silva, 

2016: Worker health and 

115. 

141 Human Health- References 

120. McDonald, YJ., S.E. Grineski, T.W. Collins, and Y.A. 

121. 

122. Island Press, 2015: Bounce Forvvard; Urban Resilience 

in the Era of Climate Change. Island Press and the 

123. Gonzalez, R. and Other contributors. 2017: 

Community-Driven Climate Resilience Planning: 

A Framework, Version 2.0. James, T. and J. Ross, 

Eds. National Association of Climate Resilience 

Planners, National Association of Climate Resilience 

124. Schrock, G., E.M. Bassett, and J. Green, 2015: 

116. Gutierrez, K. and C. LePrevost, 2016: Climate justice 125. 

in rural southeastern United States: A review of 

117. Sheffield. P., S. J. Stewart, and M. Galvez, 

2017: Climate and schools: Environmental 

hazards and International Journa[ of 

Environmental and PubLic HeaLth, 14 (11), 

1397. ]1ttp://dx.d.Qi.org/10.31~QLijerphl411J397 

U.S. Global Change Research Program 567 

126. Banks, L.H., L.A. Davenport, M.H. 

McArthur, S.N. Toro, C.E. King, and 

2016: Disaster impact on impoverished area of US: An 

inter-professional mixed method Prehospita[ 

and Disaster Medicine, 31 (6), 583-592. '.!'OJLL0o'c~""~" 

Qrg/10.1017 /.§lQ1H023XHi00090X 

127. Burger. J. and M. Gochfeld. 2017: Perceptions of 

severe storms, climate change, ecological structures 

and resiliency three years post-hurricane Sandy 

in New Urban 20 (6), 1261-1275. 

128. 

Fourth National Climate Assessment 
240 

129. Anderson, H., C Brown. L.L. Cameron, M. 

Christenson, K.C Conlon, S. Dorevitch, J. Dumas. 

M. Eidson, A. Ferguson, E. Grossman, A. Hanson, 

J.J. Hess, B. Hoppe, J. I lorton, M. S. Krueger, 

T.W. Largo, G.M. Losurdo, S.R. C. Moran, 

C. K. Raab, S. Saha, P.J. Schramm, A. 

Shipp-Hi!ts, Smith, M. Thelen. L. Thie, and 

R. Walker. 2017: Climate and Health Intervention 

Assessment: Evidence on Public J Iealth Interventions 

to Prevent the Negative Health Effects of Climate 

Change. Climate and Health Technical 

Series. Centers for Disease Control and 

Climate and Health Atlanta, GA, 92 

14 1 Human Health - References 

135. Berisha, V.. D. Hondula. M. Roach, J.R. White, B. 

D. Rentz, A. Mohamed, J. Uebelherr, and 

K. 2017: Assessing adaptation for 

extreme heat: A public hcBlth evaluation cooling 

centers in Maricopa County, Arizona. Weather, 

CLimate, and Society. 9 71-80. http://dx.doi. 

136. Gronlund, C.J., V.J. Berrocal, J.L. White-Newsomc. 

K.C. Conlon, and M.S. O'Neill, 2015: Vulnerability to 

soc:io-dcrnOJlf2Jlhic characteristics 

elderly in 

136, 

hllp:U'dx.dQ[c2J:U19JOJEi/i~'lvres.2014.0§jl_'!_? 

137. Klein Rosenthal, J., P.L. Kinney, and K.B. Metzger, 2014: 

130. Alduncc. P., R. Beilin, J. Handrner, and M. Howden, Intra-urban vulnerability to heat-related 

131. Ebi, K.L., JJ. Hess, and T.B. lsaksen, 2016: 

de,•elooment information 

Environmental 

b.!illJLdx.dQl 

New York City, 1997-2006. Hectlth E~ Pface, 30, 

http:lj'dx.doi.org/10.1016/j.healthplace.?Ql4.07.014 

138. Executive Office of the President, 2013: Fact Sheet: 

Executive Order on Climate Preparedness. The 

[Obama] White House, Office of the Press 

DC.~~~~~~~~~ 

139. Lowe, R., C.A. Coelho. C. Barcellos, M.S. Carvalho, 

132. Kabisch, N., H. Korn, J. Stadler, and A Bonn, 2017: R.D.C. Catiio, G.E. Coelho, W.M. Ramalho, T.C. Bailey, 

l:l3. 

134. 

lvL Kiefer, J. Lincoln, 

S. Pendergrass, J. Shire, J. Watson. and G.R. Wagner, 

2016: Advancing the framework for considering 

the effects of climate on worker safety and 

health. and Environmental 

U.S. Global Change Research Program 568 

D.B. Stephenson, and X. Rod6, 2016: Evaluating 

probabilistic dengue risk forecasts from a 

for BraziL eLIFE, 

140. Semenza. J., 2015: Prototype early warning systems 

for vector-borne diseases in Europe. Internationa[ 

JournaL of EnvironmentaL Research and. Public 

Health, 12 (6), 6333-6351. http://dx.doi.org/10.33B.QL 

!l~_i}!_?_Q§Q633} 

141. Worrall, E., S.J. Connor, and M.C. Thomson, 2008: 

142. Lee, J.-S,, M. Carabali, J.K. Lim, V.M. Herrera, 1.-Y, 

F-ourth National Climate Assessment 
241 

143. Lessler, J., LH. Chaisson, L.M. Kucirka, Q. Bi, K. 

Grantz, H. Salje, A. C. Carcelen, C.T. Ott, J.S. Sheffield, 

N.:--1. Ferguson, D.A.T. C.J.E. Metcalf, and 

!. Rodrigutez-13arraqu•er 

144. Lowe, D., K.L. Ebi, and B. Forsberg, 2011: Heatwave 

and adaptation advice to 

consequences of heatwaves. 

Emoircmrrrerutal Research and 

145. Garfin, G.M., S. LeRoy, and H. Jones, 2017: Developing 

an Integrated Heat Health Information 

146. 

147. 

148. 

149. 

for Long-Term Resilience to Climate and 

Extremes in the El Paso-Ju3rez-Las Cruces 

Institute of the Environment, Tucson, AZ, 

http:;/dx.;J.Qiorg/10.7289/V5930R6Q 

Carney, J.B. Smith, C. Herrick, M. 

A.S. Juliana, H. f losterman, and 

Adaptation-The State of 

Communities. Foundation. 

150. Kaplan, S., B. Sadler, K. Little, C. Franz, and P. Orris, 

14 1 Human Health - References 

151. Guenther, R. and J. Balbus, 2014: Primary Protection: 

Health Care Resilience for a Changing 

of Health and Human 

152. National Hurricane Center, 2018: National Storm 

153. DHS, 2018: 

2. NOAA National 

Department of 

washington, DC. !n.~ff 

154. Adelaine, SA, M. Sa to, Y. Jin, and H. Godwin, 2017: An 

155. Smith, K.R., A. Woodward, D. Campbel!-Lendrum, 

D.D. Chadee, Y. Honda, Q. Liu, J.M. Olwoch, B. 

Revich, and R. Sauerborn, 2014: Human health: 

Impacts, adaptation, and co-benefits. Climate 

Change 2014: Impacts, Adaptation, and Vulnerability. 

Part A: Glohai and Sectoral Contribution 

Working Grou.p II to the 

the Intergoven1mentat 

C.B., V:R. Barros, D.J. 

Mastrandrea, T.E. Bilir, M. 

Estrada. R.C. Genova, B. Girma. 

S. MacCrackcn, P.R. Mastrandrea. 

Eds. University Press, 

Kingdom New York, NY, USA, 

www.ip§..:£h.L!TI2QD:Lar5/wg2/ 

156. Knowlton, K., M. Rotkin-Ellman, L. Geballe, W. Max, 

and G.M. Solomon, 2011: Six climate ch<mge-related 

events in the United States accounted about 

$14 bil1ion in lost lives and health costs. HeaLth 

30 (11), 2167-2176. http://dx.doi.org/10.!37]L 

2012: Can Sustainable f lospitals Help Bend the Health 157. EPA, 2017: Multi-model Framework for Quantitative 

Care Cost Curve? Commonwealth Fund Pub. 1641. The Sectoral A Technical Report 

for the Climate Assessment. EPA 

430-R-17-001. U.S. 

U.S. Global Change Research Program 569 Fourth National Climate Assessment 
242 

158. O'Neill, B.C., J. M. 

Fix, and S. Levis, 2017: The 

159. Tebaldi, C. and M.F. Wehner, 2016: Benefits of 

160. Business Project, 2014: The 

Economic Risks of Change in the United 

States: A Climate Risk Assessment for the United 

161. Oleson, K.W., G.B. Anderson, B. Jones, S.A. McGinnis, 

and B. Sanderson. 2015: Avoided climate of 

urban and rural heat and cold waves over U.S. 

climate model ensembles for RCP8.5 and 

14 I Human Health - References 

166. Fann, N., C.G. Nolte, P. Uolwick, T.L. Spero, A. 

Curry Brown, S. Phillips, and S. Anenberg, 2015: 

The distribution and economic value of 

climate ozone health impacts in the 

United States in 2030. Journal the Air & Waste 

rmM 

167. Hsiang, S., R. Kopp, A Jina, l. Rising, M. Delgado, S. 

Mohan, DJ. Rasmussen, R. Muir-Wood, P. Wilson, 

M. Oppenheimer, K Larsen, and T. Houser, 2017: 

Estimating economic damage from climate 

in the United States. Science, 356 (6345), 

~/dx.doi.org/10.1126/scicnce.aal4369 

168, Anderson, G.B., K.W. Oleson, B. Jones, and RD. Peng, 

2016: trends in heatwaves 

and 

169. Graff Zivin, J. and M. Neidell, 2014: Temperature 

and the allocation of time: lmplications for climate 

Journal Labor Economics, 32 (1), 1-26. 

162. Jones, B., C. Tcbaldi, B.C. O'Neill, K. Oleson, and J. 170. Dunne, J.P., R.J. Stouffer, and J.G. John, 2013: 

Gao, 2018: Avoiding population to heatrelated extremes: Demographic vs climate 

146 (3), http:(/ 

171. Paull, S.H., U.E. 

163. Marsha, A., S.R. Sain. M.J. Heaton, AJ. Monaghan, 

and O.V. Wilhelmi, 2016: Influences of climatic and 

population 

Houston, Climatic 

()XgLl\).1007M92.1l_4.::9_l!i .. !77S-) 

164. Houser, T., R. Kopp, S. Hsiang, M. Delgado, A. Jina, 

K. Larsen, M. Mastrandrea, S. Mohan, R. Muir- 172. 

Wood, D. Rasmussen, J. Rising, and P. Wilson, 2014: 

Economic Risks in 

New York, NY, 

165. Chapra, S.C., R. Bochlcrt, C. Fant, VJ. Bierman, l 

Henderson, D. Mills, D.M.L. Mas, L. Rennels, L. 

Jantarasami, J. Martinich, K.M. Strzcpek, and H.W. 173. 

Paerl, 2017: Climate change impacts on harmful 

algal blooms in U.S. frcshwatcrs: A scrcer1inrHe·vcl 

assessment. Envlronmenlal Science 

51 (16), 8933-8943. 

£§L7Q.Ql@~ 

U.S. Global Change Research Program 570 

USGCRP, 2017: Climate Science Special Report: Fourth 

National Climate Assessment, Volume I. Wucbbles, 

D.l.. D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. 

Sle.,vart, and T.K. Maycock, Eds. U.S. Global 

Research DC, 470 pp. 

rourth National Climate Assessment 
243 

174. Roscr-Renouf, C., E.W. Maibach, and J. Li, 2016: 

Adapting to the changing climate: An assessment 

of local health department preparations for climate 

change-related health threats, 2008-2012. PLOS 

ONE, 11 (:l), e0151558. http:/!dx.doi.org/10,1371/ 

journal.pq_ne.0151558 

175. Cheng, J.J. and P. 

risks of public 

change: A review of current literature. lntr:m"ticmut 

Health, 305-311. ]lt!J2:L:dx.doi. 

176. Clarke, K ... L. and P. Berry, 2012: From to 

177. 

practice: A Canadian case study of the of 

climate change adaptation frameworks to address 

health lntenwtionat Journal Public 

167-174. 

U.S. Global Change Research Program 

14 1 Human Health - References 

571 Fourth National Climate Assessment 

(245) 

Appendix II 

ADDITIONAL MATERIAL FOR THE RECORD
246 

LETTER SUBMITTED BY REPRESENTATIVE LIZZIE FLETCHER

June 28, 2016 

Dear Members of Congress, 

We, as leaders of major scientific organizations, write to remind you of tbe consensus scientific 

view of climate change. 

Observations throughout the world make it clear that climate change is occurring, and rigorous 

scientific research concludes that tbe greenhouse gases emitted by human activities are the 

primary driver. This conclusion is based on multiple independent lines of evidence and the vast 

body of peer-reviewed science. 

There is strong evidence that ongoing climate change is having broad negative impacts on 

society, including tbe global economy, natural resources, and human health. For tbe United 

States, climate change impacts include greater threats of extreme weather events, sea level rise, 

and increased risk of regional water scarcity, heat waves, wildfires, and the disturbance of 

biological systems. The severity of climate change impacts is increasing and is expected to 

increase substantially in the coming decades. 1 

To reduce the risk of the most severe impacts of climate change, greenhouse gas emissions must 

be substantially reduced. In addition, adaptation is necessary to address unavoidable 

consequences for human health and safety, food security, water availability, and national 

security, among otbers. 

We, in tbe scientific community, are prepared to work witb you on tbe scientific issues important 

to your deliberations as you seek to address the challenges of our changing climate. 

American Association for the Advancement of Science 

American Chemical Society 

American Geophysical Union 

American Institute of Biological Sciences 

American Meteorological Society 

American Public Health Association 

American Society of Agronomy 

American Society of Ichthyologists and Herpetologists 

American Society of Naturalists 

1 The conclusions in this and the preceding paragraph reflect the scientific consensus represented by, for 

example, the U.S. Global Change Research Program, the U.S. National Academies. and Intergovernmental 

Panel on Climate Change. Many scientific societies have endorsed these findings in their own statements, 

including the American Association for the Advancement of Science, American Chemical Society. 

American Geophysical Union, American Meteorological Society, American Statistical Association, 

Ecological Society of America, and Geological Societv of America. 
247 

American Society of Plant Biologists 

American Statistical Association 

Association for the Sciences of Limnology and Oceanography 

Association for Tropical Biology and Conservation 

Association of Ecosystem Research Centers 

BioQUEST Curriculum Consortium 

Botanical Society of America 

Consortium for Ocean Leadership 

Crop Science Society of America 

Ecological Society of America 

Entomological Society of America 

Geological Society of America 

National Association of Marine Laboratories 

Natural Science Collections Alliance 

Organization of Biological Field Stations 

Society for Industrial and Applied Mathematics 

Society for Mathematical Biology 

Society for the Study of Amphibians and Reptiles 

Society of Nematologists 

Society of Systematic Biologists 

Soil Science Society of America 

University Corporation for Atmospheric Research 
248 

REPORT SUBMITTED BY REPRESENTATIVE BILL FOSTER
249 

·Jxb·-- ·'!xf· ._., 

Foreword 

We are pleased to submit our report, "Advancing the 

Landscape of Clean Energy Innovation." In this report 

we describe today's U.S. ecosystem of clean energy 

innovation from the perspectives of technological 

potential, investment patterns, institutional roles, 

and public policy. 

The report identifies critical strengths and weaknesses of this ecosystem and 

offers recommendations for making that ecosystem more effective. It examines 

the different technology readiness stages through which innovation passes and 

the importance of feedback among those stages. It also discusses the significant 

opportunities to accelerate the pace of dean energy innovation that ore 

presented by rapid advances occurring today across a myriad of technologies 

originating outside the energy sector. 

We would like to emphasize three observations from our report. 

First, the U.S. has shown over many decades an unparalleled capacity to nurture 

energy innovation. This capacity reflects a rich and durable collaboration among 

government, universities, research institutions, industry, and entrepreneurs. This 

collaboration is grounded in the belief that energy innovation contributes 

importantly to economic growth, energy security, and environmental stewardship. 

Second, even with our capacity to innovate, and even with the emergence of 

innumerable technological opportunities, there are significant challenges in moving 

forward with dean energy technology, These challenges arise from the sheer size 

and complexity of existing systems, the degree to which these systems ore 

embedded in our economy, and the high public expectations of safety and reliability 

they must meet. Energy systems traditionally hove evolved incremento!!y. 

• Third, these challenges can be met only by building on the collaborative strengths 

that our ecosystem has already demonstrated. Clean energy innovation depends on 

a national commitment to technological research; private-sector efforts to develop, 

apply, and commercialize products incorporating that research; and public policy. 

Advancing the Landscape of C!eon Energy Innovation, February 2019 
250 

•Jxb• B"*-tlv"ough 

·w·-

In this report we convey the need for a comprehensive approach involving both 

public and private sectors in order to expand the current landscape of clean 

energy innovation and accelerate its processes. We hope that our report 

contributes to on understanding of the challenges presented and the approaches 

needed to address those challenges effectively. There is no final word on the 

subject. We see this report as a contribution to a continuing national dialogue and 

hope that it will stimulate further discussion, understanding, and action. 

We ore grateful for the opportunity that Breakthrough Energy and its partners 

have provided to explore this topic and recognize their commitment to 

advancing a meaningful and timely national dialogue. We hope that our report 

informs an appreciation of the complexity, reach, inherent dynamism, and promise 

of the U.S. clean energy innovation landscape and of the leadership that the 

United States con continue to provide. 

Ernest .J. Moniz 

Former U.S. Secretory of Energy 

Project Co-Chairman 

DanieiYergin 

Vice Chairman IHS Mark it 

Project Co-Chairman 

Advancing the landscape of Clean Energy Innovation. February 2019 3 
251 

·&%·~kthrough ·w· Energy 

Project Team 

Co-Chairmen 

Ernest J. Moniz 

Former U.S. Secretory of Energy 

Project Directors 

Melanie Kenderdine 

Principal, Energy Futures Initiative 

(EFI) Associates 

Contributing Authors 

Energy Futures Initiative 

(EFI) Associates 

Joe Hezir, Principal 

Mike Knotek, Distinguished Associate 

Jeanette Pablo, Senior Associate 

Alex Kizer, Director 

Tim Bushman, Senior Analyst 

Daniel Yergin 

Vice Chairman, fHS Markit 

Tim Gardner 

Vice President, JHS Morkit 

IHSMarkit 

Atu! Arya, Senior Vice President 

Jamey Rosenfield, Senior Vice President 

Carolyn Seta, Director 

James Coon, Associate Director 

Advancing the Landscape of Clean Energy Innovation, February 2019 4 
252 

·dxb·- ·'lxf·""-

Advisory Committee 

Breakthrough Energy, JHS Markit, and Energy Futures Initiative would like to thank 

these individuals for their invaluable contributions and guidance throughout the 

course of this project. 

Matt Boker 

Program Officer- Environment 

Wiffiam and Flora Hewlett Foundation 

Drew Bond 

Senior Fellow & Director of Energy 

Innovation Programs, American 

Council on Capitol Formation Center 

for Policy Research 

Josh Freed 

Senior Vice President for the Clean 

Energy Program, Third Way 

Kelly Sims Gallagher 

Professor of Energy and 

Environmental Policy at The Fletcher 

School, Tufts University 

Director of the Center for 

International Environment & 

Resource Policy, Tufts University 

Jason Grumet 

Founder and President, 

Bipartisan Policy Center 

Hal Harvey 

Chief Executive Officer, 

Energy Innovation LLC 

Jan Mazurek 

Program Director for Clean Power, 

CfimateWorks Foundation 

Charlotte Pera 

President and Chief Executive Officer, 

CfimateWorks Foundation 

Jonathan Pershing 

Program Director Environment, 

Wflfiam and Flora Hewlett Foundation 

Brook Porter 

Partner and Co-Founder, G2VP 

Jeffrey Rissman 

Industry Program Director & Head of 

Modeling, Energy Innovation LLC 

Ellen Williams 

Distinguished University Professor, 

University of Nary/and 

Former Director, Department of 

Energy, Advanced Research Projects 

Agency Energy 

JettoWong 

President, JLW Advising 

Former Director; Deportment of Energy, 

Office ofTechnologyTransitions 

Advancing the landscape of Cl0an Energy Innovation, February 2019 5 
253 

.g. Breakthrough ·W· energy 

Contents 

Executive Summary . . 14 

Chapter 1: Framing the Clean Energy Innovation Discussion 22 

Findings: Framing the Clean Energy Innovation Discussion . 23 

Focus on the Future: Opportunities in Clean Energy Innovation 24 

The Changing Energy Landscape 24 

Challenges Facing Clean Energy Innovation 35 

Aligning the Components of the Clean Energy Innovation Ecosystem. 39 

Chapter 2: The Private-Sector Role in Clean Energy Innovation . . 41 

Findings: The Private-Sector Role in Clean Energy Innovation. 42 

Private-Sector Challenges in Clean-Energy innovation 43 

Investment Patterns 45 

Navigating the Private-sector Innovation Pathway. 55 

Institutional Support . 64 

Strengthening the Private-sector Role in Clean Energy Innovation .71 

Recommendations: The Private-Sector Role in Clean Energy Innovation . 76 

Chapter 3: Focusing the Energy Innovation _Portfolio on Breakthrough Potential . 77 

Findings: Focusing the Energy Innovation Portfolio on 

Breakthrough Potential 78 

Clean Energy Innovation: the Need for a Focused Portfolio . 79 

Drivers of Clean Energy Technology Breakthroughs. 80 

Identifying Technology Breakthrough Priorities 84 

Storage and Battery Technologies. 88 

Advanced and Small Modular Nuclear Reactors as Sources of 

Carbon-free Electriclty and Process Heat for Industry 92 

Hydrogen as Clean Energy Carrier, Storage Medium, and Enabler of 

Decarbonized Industrial and Transportation Sectors 96 

Advanced Manufacturing Technologies . 99 

New Energy Technologies for BuHdlngs . 103 

Systems: Electricity and Smart Cities. 105 

Deep Decarbonization: Large-Scale Carbon Management . . 108 

Next Steps in Portfolio Development 112 

Recommendations: Reshaping the Energy Innovation Portfolio for 

Breakthrough Potentia! . 116 

Advancing the Landscape of Clean Energy Innovation, February 2019 6 
254 

•Jxb• Bteokthrough 

·w·Enersv 

Chapter 4: The Role of the Federal Government in the Energy 

Innovation Ecosystem . . . . . 121 

Findings: The Ro!e of the Federal Government in the Energy 

Innovation Ecosystem 122 

Setting the Scope and Scale of the Federal Clean Energy 

Innovation Portfolio 123 

The Centra! Role of the Dept. of Energy in Clean Energy Innovation. 125 

Energy-Related Innovation Support at Other Federal Agencies 142 

Refocusing Future Federal Tax Policy to Spur Innovation. 152 

The Looming Impact of Discretionary Spending Caps. . 155 

Seeking Federal Funding Certainty for Direct Federal Investment 

in Innovation 

Recommendations: Regarding the Role of the Federal Government 

in the Energy Innovation Ecosystem 

Chapter 5: The Role of State, Loco~ and Tribal Governments in Clean 

Energy Innovation . . . . . . 

Findings: The Role of State, Local, and Tribal Governments 

in Clean Energy Innovation. 

The Role of States in Creating Clean Energy Markets. 

The Role of Cities, Tribal, and Rural Communities in Clean 

Energy Innovation . 

Federal Initiatives that Support State, Local, Tribal and Government 

Leadership in Clean Energy Innovation 

Recommendations: The Role of State, Local, and Tribal 

159 

. 162 

• 163 

164 

. 165 

181 

. 189 

Governments in Clean Energy Innovation 193 

Chapter 6: Fostering Regional Clean Energy Innovation Ecosystems . 194 

Findings: Fostering Regional Clean Energy Innovation Ecosystems . 195 

The Growth of Regional Innovation Ecosystems . 196 

Energy Innovation Ecosystems: Features, Players, Trends 200 

Creating Regional Innovation Opportunities Where Innovation 

Clustering Does Not Exist , 206 

Recommendations: Fostering Regional Clean Energy 

Innovation Ecosystems . 208 

Chapter 7: Mobilizing Increased Private Sector Investment in Energy Innovation 209 

Findings: Mobilizing Increased Private Sector Investment in 

Energy Innovation . 210 

Landscape of Private Sector Investment in Energy Innovation. 211 

Conclusion: Enhancing Private Sector Options Con Help 

Meet National Goals 

Key Recommendations: Mobilizing Increased Private Sector 

Investment in Clean Energy Innovation 

Advancing the landscape of Ciean Energy Innovation, Febrvary 2019 

227 

. 228 
255 

.Jxb. Br4<Jkthrough ·w· Enetgy 

Table of Figures 

Chapter l: Framing the Clean Energy Innovation Discussion . . . . . . 22 

Figure 1-1. 

U.S. C02 Emissions Reductions in Electricity Generation, 2006-2014 25 

Figure 1-2. 

Emerging Clean Energy Innovation Spaces: Examples of 

Incumbents and New Players . 26 

Figure 1-3 

Projected Number of Digital Devices Deployed Worldwide . 27 

Figure 1-4. 

Residential Smart Meter Deployment, 2017. 28 

Figure 1-5. 

Comparison of EV Sates and Penetration by Leading 

Ten Countries, 2017 29 

Figure 1-6. 

Population Growth Projections for both Rural and Urban Areas 30 

Figure 1-7. 

Sub-national Commitments to Meeting U.S. NDCs 

under Paris Agreement . 31 

Figure 1-8. 

Global Oil and Gas Companies in the Oil and Gas Climate Initiative 32 

Figure 1-9. 

Meeting Deep Decarbonization Goals Will Require Significant 

Investments in Innovation 

Figure 1-10. 

Energy Investments by Resource and Country, 2017 

Figure 1-11. 

Share of US. Energy Consumption, 1850-2014 

Figure 1-12. 

Moving Innovations to the Marketplace . 

Figure 1-13. 

Global Energy Investment Totaled $1.8 Trilhon, 2017 

Figure 1-lt+. 

Aligning Players, Policies and Programs to Accelerate 

Clean Energy Innovation (!!!ustrotive). 

Advancing the Landscape of Clean Energy Innovation. Fobruary 2019 

33 

35 

36 

37 

38 

40 

8 
256 

.Jxb. Breakthrough 

·w·-

Chapter 2: The Private· Sector Role in Clean Energy Innovation . . . . 41 

Figure 2-1. 

Global Industry Private R&D and R&D as Percentage of Sales, 2015 43 

Figure 2-2. 

Technology Readiness Stages of the Innovation Process. 4Lt 

Figure 2-3. 

Investment Sources Across the Technology Readiness 

Stages of Clean Energy Innovation, 2016 46 

Figure 2-4. 

Share of Clean Energy Innovation Investments by Application 

and Technology Readiness Stage, 2016 . 46 

Figure 2-S. 

Clean Energy End-use Investment at the Demonstration Stage, 2016. 50 

Figure 2-6. 

Sources of Private Capitol for Clean Energy Deployment, 2016 54 

Figure 2-7. 

Venture Capital Investment in Clean Energy by Category, 2002-2016. 56 

Figure 2-8. 

Changes in Venture Capita! Investment by Technology 

Category, 2012 vs. 2016 57 

Figure 2-9. 

U.S. Investor-owned Utilities Direct R&D Investment, 2016 62 

Figure 2-10. 

EPRI R&D Expenditure by Program, 2004-2016 63 

Figure 2-11. 

Startup Technology Portfolio by lncubator Type . 66 

Figure 2-12. 

Three Pillars of Energy Innovation 71 

Advoncmg the Lend scope of Clean Energy InnovatiOn, February 2019 9 
257 

Chapter 3: Focusing the Energy Innovation Portfolio on 

Breakthrough Potential . . . . . . . . . . . . . . . 77 

Figure 3-1. 

The Basic Innovation Technology Readiness Stages 79 

Figure 3-2. 

Sankey Diagram of the Clean Energy Technology Supply Chain . 83 

Figure 3-3. 

Applications of Energy Storage in Electricity Value Chain 89 

Figure 3-4. 

Lithtum Demand by End-use Application, 2013-2025 90 

Figure 3-5. 

Select Battery and Storage Technologies by 

Application and Capability. 91 

Figure 3-6. 

Continuing Evolution of Nuclear. 93 

Figure 3-7. 

Hydrogen is a Clean Energy Carrier 

Figure 3-R 

96 

Example Hydrogen Production Pathway . 98 

Figure 3-9. 

Sankey Diagrams of Process Energy Flow in the U.S. Manufacturing 

Sector (Tbtu, 2010) . 100 

Figure 3-10. 

Shore of Energy Consumption by Industrial Manufacturing Sector 

and Sub-sector, 2015. . 101 

Figure 3-lL 

Bandwidth Diagrams l!!ustrating Energy Savings Opportunities in 

Four Energy-Intensive U.S. Manufacturing Industries . 102 

Figure 3-12. 

Energy Savings Potentia! of Energy Star Technologies . 104 

Figure 3-13. 

Drivers and Supportive Policies are Essential 

Figure 3-14. 

Generalized Technology Roadmap . 

Advancing the Landscape of Clean Energy !nnovotton, February 2019 

. 109 

114 

10 
258 

Chapter 4: The Role of the Federo1 Government in the 

Energy Innovation Ecosystem . . . . . . . . . . . . . . . . . 121 

Figure 4-1. 

Federal and Nonfederal Funding of Academic R&D 

Expenditures, FY 1997-2016 123 

Figure 4-2. 

DOD, DOE Obligations for Research by Major S&E Field, FY 2015 125 

Figure 4-3. 

Comparison of DOE Budget Structures by Organization 

and Application. . 128 

Figure 4-4. 

Questions Raised by Current DOE Organizational Alignment . . 130 

Figure 4-5. 

Current DOE Fuels-Based Organization and Budget . 131 

Figure 4-6. 

ARRA Funds for DOE RD&D and Deployment Activities 135 

Figure 4-7. 

ARRA Funding for Select State-level Energy Innovation Projects . 136 

Figure 4-R 

ARPA-E Key Facts. 137 

Figure 4-9. 

DOE's Loon Programs Office Portfolio: Diverse, Regional, 

High Impact, Late Stage lnnovation . 143 

Figure 4-10. 

Agriculture and Energy . 147 

Figure 4-11. 

Savings from DOT's NextGen Program ([nc!uding Efficiency) . 151 

Figure 4-12. 

Discretionary Spending Cops, . 156 

Figure 4-13. 

Range of Potential Changes in the Non-Defense Discretionary 

Spending Cops 157 

Figure 4-14, 

Volatility in Funding for Select DOE Programs 

(Annual Percent Change) . 160 

•Jxb• Breok:thl'<~ugh 

·w·- Advancing the Landscape of Clean Energy Innovation. February 2019 11 
259 

•Jxb• Breokl:hrough •1xf· Energy 

Chapter 5: The Role of State, Local, and Tribal Governments in 

Clean Energy Innovation . . . . . . . . . 163 

Figure 5-1. 

Renewable Portfolio Standard Policies . 166 

Figure 5-2, 

Impact & Benefits of State Policies . 168 

Figure 5-3. 

Solar Industry Data by State, 2016 and 

Wind Industry Data by State, 2017. . 169 

Figure 5-4. 

Building Energy Codes by State & Year, Residential Buildings 172 

Figure 5-5. 

State Clean Energy Funds Investment in Renewable Energy 173 

Figure S-6. 

States with Green Banks or Energy Investment Partnerships 174 

Figure 5-Z 

States with PACE Programs 175 

Figure S-8. 

Commercia! and Residential PACE Program Financing, 2010-2016. 176 

Figure 5-9. 

California Public Benefits Funds for Renewab!es & Efficiency 

Funding Levels, 2015 (in millions) 178 

Figure 5-10. 

The Growth of New York City's Tech Sector from 2003-2013 183 

Figure 5-11. 

Conceptual Framework for Smart Cities. . 184 

Figure S-12. 

Current and Identified Clean Energy Projects in 

Alaska's Rural Energy Initiative . . 188 

Figure 5-13. 

Federal Ro\e fn the Promotion of Smart Cities. 192 

Advancing the Landscape of Clean Enorgy !Pnovctlon, February 2019 12 
260 

.Jxb. Br410kthr0Uijh •'1xf• EMtSY 

Chapter 6: Fostering Regional Clean Energy Innovation Ecosystems . 194 

Figure 6-1. 

From CMAP, "Benefits of Clustering" . 196 

Figure 6-2. 

Shale Ploys and Wind Speeds: The Regional Nature of Energy Resources 197 

Figure 6-3. 

Mops of Solar and Wind Energy Innovation lndicotors. 

Figure 6-4. 

Top Eight States in Terms of Total Manufacturing Output, 

and Share of Gross State Product, 2014. 

Figure 6-5. 

Regional Clean Energy Innovation Index . 

Figure 6-6. 

198 

. 199 

. 200 

Principal Elements of o Regional Clean Energy Innovation Ecosystem. . 201 

Figure 6-Z 

Select Energy Innovation Ecosystem Players by Region 

and Role in Process 

Figure 6-8. 

Map of Broadband Internet Access and Map of 

Electric Cooperative Service Territories 

. 202 

207 

Chapter 7: Mobilizing Increased Private Sector Investment in Energy Innovation . 209 

Figure 7-1. 

U.S. R&D Investments by Sector, 1953-2015 211 

Figure 7-2. 

Later-stage Private Investment in Sustainable Energy 

Technologies by Selected Region or Country, 2006-2016 212 

Figure 7-3. 

Patent Activity/Activity Index for a Range of Sustainable 

Energy Technologies for the US., EU, and Japan . 213 

Figure 7-4. 

Current Landscape of Private Sector in Clean Energy Innovation . 215 

Figure 7-5. 

Potential to Mobilize Additional Private Sector Capital for 

Clean Energy Innovation from Tax Reform 217 

Figure 7-6. 

Moody's Climate Change and Sovereign Credit Risk . 225 

Figure 7-7. 

Tax Credit Available for Different Sources and Uses of C02 . 226 

Advancing the Landscape of Clean Energy Innovation. February 2019 13 
261 

.Jxb. Breakthrough 

·9xf· Energy 

----------------

Executive Summary 

The United States has been at the forefront of 

energy innovation for many decades. One of the 

most important reasons is the unique and extensive 

collaboration along the entire chain of innovation, 

from basic research to deployment, that engages 

the federal government, national labs and research 

institutes, universities, private sector, and state and 

local governments. This system has given the US. a 

global advantage for many decades. 

The increasing focus on clean energy technology solutions and the potential for 

disruptive changes ln energy systems points to the need for an objective review 

of the current clean energy innovation ecosystem. How does the clean energy 

innovation system work? What are its strengths and weaknesses? Is it up to the 

challenges? And how can it be improved and accelerated? 

These are the questions that this study seeks to answer. Signif1cont 

opportunities for clean energy innovation ore presented by the changing 

U.S energy supply profile; by advances in platform technologies such as 

digitalization and big data onolytics: by expansion of electrification in the 

transportation and industrial sectors of the U.S. economy and the resulting 

electricity dependence of these sectors; by increases in urbanization and the 

emergence of smart cities; and by broad social and economic forces pushing to 

decarbonize energy systems in response to the risks posed by global warming 

and associated climate change. 

Clean energy innovation supports multiple national goats: economic 

competitiveness, environmental responsibility, energy security, and national 

security. In serving these goals the need to address climate change is the 

challenge that calls most urgently for accelerating the pace of clean energy 

innovation. 

Key features of energy systems, however, impede accelerated innovation. Energy 

is a highly capitalized commodity business, with complex supply chains and 

established customer bases, providing essential services at a!! levels of society. 

These features lead to systems with considerable inertia, focus on reliability 

and safety, aversion to risk, extensive regulation, and complex politics. Existing 

Innovation processes face challenges as they work within these boundary 

conditions. The rapid pace of international energy investment, the commitments 

of most countries to Paris climate goals, and the ability of some countries such 

as China to rapidly increase clean energy investments challenge the preeminent 

position of the U.S. in clean energy innovation. 

Successful clean energy innovation on a large scale in the U.S. requires 

alignment of key players, policies, and programs among the private sector, the 

federal government, and state and local governments. This report considers 

Advancing the Landscape of Ck)an Energy lnr1ovobon, Februo1y 20J9 14 
262 

. Jxb. Breokthrough ·w· Energy 

these alignment needs through an assessment of the roles of these various 

groups. It also identifies critical clean energy technologies. It further suggests 

the value of regional efforts to advance innovation, and discusses ways 

in which federal tax policy could accelerate innovation. The report offers 

recommendations in each of these areas. 

The Role of the Private Sector 

The private sector is central to clean energy innovation, providing entrepreneurial 

vision, channeling financial resources, and connecting innovation to the rest of 

the energy system and the economy. At the some time, fundamental dynamics 

of the energy sector present significant challenges to clean energy innovation, 

stemming from basic industry characteristics and from the difficulty of capturing 

the full value of clean energy through market transactions alone. Innovators in 

clean energy face significant challenges in securing -financial support and in 

demonstrating the compatibility of new technologies with existing systems. Over 

the post several years, venture capital has reduced its engagement in clean 

energy innovation, and traditional energy companies ore exploring new models and 

mechanisms for innovation and investment. 

While the initial stages of clean energy innovation are supported by a diverse, 

world-class set of U.S. research institutions, the innovation support system 

weakens as inventions move toward commercia!!zation. The clean energy 

incubators that have emerged in recent years have so far tended to support 

software solutions. The availability of testing facilities for product demonstration 

is limited by the small number of facilities suitable for sustained testing and by 

their specialization. 

Because of the energy system's long cycles of adoption, a brood range of 

approaches should be deployed to make it easier for adopters to understand, 

anticipate, and support the innovations that ore being generated at the early 

stages of the innovation process. These efforts include, on the part of energy 

companies, open innovation, standardization of procurement requirements, 

encouragement of innovation testing either through dedicated evaluation staffs 

or through performance metrics, and active outreach to become familiar with 

innovations at the development stage or earlier. They include, on the port of 

innovators, early attention to the needs of adopters as indicated by expressed 

needs and by the past performance of innovation efforts. 

Investments are needed from foundations and from federal, state, and local 

governments to expand the availability of open-access testbeds and strengthen 

the effectiveness of incubators in accelerating commercialization of innovative 

technologies. Some of these investments could fund research into best practices 

and performance results of incubators and testbeds and of state and local 

programs supporting innovation. 

Because clean energy Innovation incentivizes only modest fmonciol investments 

at precommercial stages, and because strategic corporate investment is focused 

primarily on those innovations recognized as useful to business objectives, 

strategic philanthropic investors and coalitions of industry investors with longterm horizons could play an important role in identifying and supporting promising 

technology ventures that are otherwise not commercially viable in the near term . 

Advancing the landscape of Clean Energy !nnovat•on, February 2019 15 
263 

techno!ogles (e.g. Cycf6tron Rbodl 

A shared agenda of primary technology objectives con help ensure that programs 

pursued by multiple stakeholders in the clean energy space are timely, durable, 

and It can give and creative Innovators a 

particular area of initiative and the 

steps needed to sustain critical innovations over long time spans, and it can 

give corporate adopterR, flnanciol investors, and policymakers visibility into the 

evolving future of clean energy 

A four-step methodology is suggested for identifying breakthrough technologies 

to address national and global challenges and help meet near, mid- and long-term 

clean energy needs and goals. These steps consider technical merit, potentia! 

other elements of the and 

technology candidates yields a key technology shortlist: 

Storage and battery 

technologies 

Advanced nuclear reactors 

Technology applications for 

industry and buildings as sectors 

that are difficult to decarbonize 

Hydrogen 

Advanced manufacturing 

technologies 

Building energy technologies 

Systems: electric grid 

modernization and smart cities 

Deep decarbonization/largescale carbon management 

Carbon capture, use, and 

storage at scale 

Sunlight to fuels 

Biological sequestration 
264 

The Federal government has long played a centra! role 1n supporting energy 

innovation. Through research gronts, loon programs, tax incentives, laboratory 

facilities, programs, and public-private partnerships, it has set the direction 

and pace R&D, with profound impact on the notional economy. 

The principal agency funding clean energy innovation is the Deportment of Energy 

(DOE), which administers about 75 percent of all Fedoral energy R&D spending. 

DOE performs its role in pmtnership with its 17 notional laboratories, academia, 

states, regions, other agencies, and the private sector. There ore, however, several 

other F·edero! agencies with significant clean energy innovation budgets, including: 

the Department of Defense (DOD), the (DOT), and 

the Department of Agricutture (USDA) at lhese agencies are missionfocused, however, as opposed to being broadly based across all energy sectors_ 

As the primary Federal funder of energy R&D, DOE has played a critical role 

in changing the u_s_ energy londscape over several decodes, Shortly after its 

establishment in 1977, DOE characterized U.S. shale basins and supported the 

development of key drilling technologies that enabled horizontal drilling. It has 

hod an ongoing and central role in developing supercomputing, an enabling 

technology for digitalization, ortiflcial intelligence, smart systems, and subsurface 

characterization. Its investment in phasors and sensors support the smart grid_ 

The Advonced Research Projects Agency Energy (ARPA-E)- a DOE program 
265 

has led to the creation of dozens of clean 

raised more them $2_6 billion in private-sector 

However, DOE's performance in advancing dean energy innovation would 

benefit from several institutional moddlcations. F-or example, the fuels-based 

organizational structure of the DOE, which has been in existence since 1979, is 

not optimized for modern energy systems and needs. It tends to lead to budget 

allocations by fuel, rather than prioritization by innovation potentiaL 

The stable and predictable funding is also a concern for 

Federal clean energy RD&D 

significant (approximately $6.4 in FY 2016 if expenditures 

agencies and by DOE on basic science research ore included), some prominent 

governm0nt and industry leaders have recommended the need for funding levels 

at two to three times the current levels based on the energy industry's current 

value to the economy BipartiCJan 8udget Act 

of 2018 (GBA) set are os much as 

25 percent higher than the Administration's providing considerable 

headroom for near-term increases in energy innovation -this 

agreement extends through FY 2019 highly uncertain budget outlook for 

FY 20?0 makes it difficult to plan on energy innovation portfolio focused 

on technologies with high breakthrough potential 

- Instituting o multi-·veo> 011d n>un,~aamlcv 

process 'with brc•ad··bas(\d in••olvemeni: fr<>m 

privqt€1 sector a:nd academia. 

-'Expanding use of pr!ze authority to foster competition ond 

PUI1Hc~prrvoto partnerships witb flexible fino:ncla! 

Investment Agreements. 
266 

State and city governments have regulatory outhority over most of the myriad 

consumer, commercial, and industrial activities that co!!ectively shape the 

country's patterns of energy central roles in advancing clean energy 

innovation, above all application of clean energy 

of those technologies through supportive 

Cities are crucial clean energy innovation testbeds. Urbanization trends 

make "smart cities" especially important as technology platforms for a clean 

energy future. Enhanced federal·· state-city, private-private 

partnerships can help unleash smart urban services, 

mobility, and improvements in the 21st century. "Smarr 

improvements could a!so signif1cant value to rural communities 

enabling decentralized generation and manufacturing, improving 

and supporting economic development 

The contribution of state. local. and tribal governments to clean energy innovation 

could be further strengthened by development of program 

standardization, capacity and resource enhancement, 

modernization of ratemaking and business models. Programs that support and 

promote clean energy and energy innovation require state and loco! 

administrative resources ond expertise; offices ond that run thern often 

have limited resources. Also, traditional ratemaking policies and methodologies 

at the state and local level can act as barriers to deployment of innovative 

energy technologies due to their reliance on proven track records associated with 

reliability and cost savings 
267 

Many of the innovation opportunities and risks faced 

regional in nature and are appropriately managed 

region's specific needs. Strong regional observable 

among innovation, job creation, and technology deployment in the solar and wind 

energy industries. 

Many energy innovation clusters in the U.S. are in the process of evolving into fully 

integrated innovation ecosystems. While federa!!y funded RDD&D historically has 

not been wei! connected to state and regional economic development, activating 

these regional clusters to break down the barriers among federal, state, and loco! 

resources wi!! create new synergies. National labs could serve as anchors for these 

efforts. While Federal support is important, regional leadership is critical. State 

and local governments, the private sector, universities, and philanthropies a!! have 

important roles in particular strengths and shaping the particular 

contributions 

innovption options. 

For U.S.- based entities, budget caps, reduced discretionary spending, and the Tax 

Cuts and Jobs Act (TCJA) will put downward pressure on Federal spending but will 

incentivi:zc corporations to increase signif1Contly business investments overthe next 

decade (with estimates of up to $1.5 trillion in incremental new investment, some of 

which could be targeted to energy innovation and infrastructure. Attracting these 

funds into clean energy innovation wi!! depend on success in aligning the vorious 

clements of the innovation ecosystem discussed in this report: public 

that encourage o robust pipeline of research and that create 

energy applications, combined with private-sector institutions that facilitate the 

cornrnerciolization of innovations. 

The TCJA left unchanged the existing tax credits for renewable 

and geothermal), but did not extend the so-called "orphan" tax 

combined heat and power projects, geothermal heat 

plants. Most of these credits had expired at the end 
268 

Full report can be found at: http://www.b-t.energy/reports/advancing-the-landscape/ 

PTC; other credits were 

and processes in both 

private sector. 
269 

ARTICLE SUBMITTED BY REPRESENTATIVE SEAN CASTEN

Jagai e11 ai.Envlronmertta!Health (2017) 16o38 

10.1186/s12940·017·0245-1 Environmental Health 

Hospitalizations for heat-stress illness varies 

between rural and urban areas: an analysis 

of Illinois data, 1987-2014 

Jyotsna S. Jagai", Elena Grossman', Livia Navon2

, Apostolis Sambanis' and Samuel Dorevitch1 

Abstract 

<J)crossMark 

Background: The disease burden due to heat-stress illness (HSI), which can result in sig1nific:an1: morbidity ar<d 

is expected to increase as the climate continues to warm. In the United States (U.S.) 

epidemiology is from of urban heat waves. There is limited research adcJre•;sino \\thethel' HSI hos.p'tl•lization 

varies between urban 

Methods: HOSIPitalizations 

stra1ta). A C)ne-degree Celsius increase in maximum mumrrv 11veraqe ten1peran2rewas 

100,000 population in the thinly pO[)UII>tecl cc•unl:ies cor11p,3red 

most common additional diagnc,se1; of pa:tien.ts 

were cJehydr.3\ic•n, E'lectrolyte al,nc•rm.aliti·es, .and acute renal disorders. Total 

were $167.7 million and (in 2014 US dollars). 

Conclusion: Elevated temperatures appear to have different on HSI rates as function of 

urbanization. 1he most rural and the most urbanized counties Illinois had largest increases in monthly 

hospitalization rates for HSI per unit Increase in the monthly maximum temperature. This 

that of communities to heat is complex strategies to reduce HSI may need to be to 

the degree of of a county. 

Keywords: Heat stress illness, Temperature, Climate change, Temperature-heat stress ;!!ness relationship, 

Urban-rural differences 

BlaMed Central 
270 

Jagai eta/. Environmental Health (2017} 16:38 

Background 

Illness associated with heat is the most common cause 

of weather-related deaths in the United States [1]. Heatstress illness (HSI) ranges in severity from relatively mild 

heat cramps to life-threatening heat stroke [2, 3]. HSI 

was the primary cause of environmental exposurerelated injuries treated in emergency departments in the 

U.S. from 2001 to 2004 [4]. Estimates of total health care 

costs based on Medicare claims data associated with 

hyperthermia were more than $36 million for 2004-

2005 [5]. The observed rise in temperature over the past 

fifty years in the U.S. [6] and globally [7] is expected to 

continue this century. Consequently, the HSI disease 

burden is expected to increase. 

High ambient temperature is associated with mortality 

[8], though most of the studies that describe that association focus on urban areas [9, 10] or urban heat waves 

[11-18]. Studies have typically described a non-linear relationship between temperature and mortality rate however, 

there is much variation based on location [10, 19]. This 

spatial heterogeneity suggests that populations may adapt 

to regional norms. Areas unaccustomed to heat, such as 

cities in the north, are more vulnerable and demonstrate 

higher mortality rates at lower absolute temperatures 

[10, 20]. These relationships also vary by confounding 

factors such as population density, socioeconomic status. 

and access to air conditioning [21]. The elderly, very 

young, and those with underlying medical conditions are 

the most vulnerable to heat-related mortality [22-24]. 

Similar to findings with mortality, studies have shown a 

non-linear relationship between temperature and morbidity 

[17, 23, 25-27], These studies have focused on a variety of 

outcomes impacted by heat, including cardiovascular disease, respiratory diseases, and asthma [25, 27-29]. Recent 

studies utilizing emergency dispatch data demonstrated 

that morbidity rates are strongly associated with 

temperature increases [30-32]. Among the elderly, emergency department visits and hospitalizations tOr a variety of 

health conditions are more frequent during extreme heat 

events [25, 33-35]. Less research has focused on morbidity 

due to HSI itself, as opposed to morbidity due to other conditions impacted by heat [33, 36]. 

While research on heat-related morbidity has focused 

on urban areas, agricultural workers appear to be 

vulnerable to heat-related mortality [37] and morbidity 

[38, 39] due to their increased exposure to high temperatures, and perhaps the physical exertion that is required 

by their jobs. The rate of heat-related occupational fatalities is approximately 20 times higher for crop production workers than for U.S. workers overall (0.39 vs. 0.02 

per 100,000 workers) [37]. Nevertheless, there has been 

limited research focusing on the variability in HSI between urban and rural areas. A study looking at HSI in 

North Carolina found the highest rates of morbidity and 

Page 2 of 10 

strongest associations with increasing temperature in the 

most rural areas studied [40]. Similarly, a study using 

Environmental Public Health Tracking Data found 

higher rates of emergency department visits for HS1 in 

rural areas in all 14 states considered [41]. Limited research on heat morbidity in rural areas may be due to 

lack of adequate data in rural areas and also due to an 

interest in the urban heat island effect [23]. 

In this study, we use health, weather, and urbanization 

data from the state of Illinois to assess differences in associations between summer temperatures and hospitalizations 

for HSI as a function of urbanization. We also characterize 

clinical and economic aspects of HSI hospitalizations. Characterizing the relationship behN"een temperature and 

urbanization on HSI rates will improve our understanding 

of the ambient temperature-HSI morbidity relationship and 

it can he useful for public health preparedness efforts. 

Methods 

Hospitalization data 

We utilized hospital discharge data from the Illinois 

Department of Public Health (IDPH) Hospital Discharge 

Database. The database includes discharge data from 97% 

of Illinois hospitals; the remaining non-member hospitals 

are located in Cook County, a primarily urban area encompassing the city of Chicago, and account for 7% of all Cook 

County hospitalizations [42]. Each record includes patient 

demographics, county of residence, and up to nine diagnoses codes. Diagnoses were coded using the International 

Oassification of Diseases, 9th Revision, Oinical Modification (ICD-9-CM). Heat-related illness was defined as 

including diagnosis of ICD-9-CM 992.x, effect of heat or 

light, that includes heat stroke, heat syncope, and heat 

exhaustion, or ICD-9-CM E900, accidents due to heat as 

any one of the diagnoses (up to nine per case) recorded. 

Due to the low number of cases 'With relevant diagnoses, 

data were provided aggregated monthly. Cases were limited 

to the summer months, May through September, for the 

28-year period from 1987 to 2014. 

Age-adjusted mean summer monthly HSI hospitalization 

rates were calculated per 100,000 population for each 

county by year using direct standardization methods. To 

account for changes in the population over the 28-year 

study period, the study period was divided into three time 

periods and corresponding population data were used to 

calculate rates. For the years 1987-1994, the 1990 Census 

data [43] was used as the denominator, for years 1995-

2004, the 2000 Census data [43] was as the denominator, 

and for the years 2005-2014, the 2010 Census data [43] 

was used as the denominator. Nine age categories were 

created, 0-9 years, 10-19 years, 20-29 years, 30-39 years, 

40-49 years, 50-59 years, 60-69 years, 70-79 years, 

and ~80 years of age. Average summer monthly HSI 

hospitalization rates by county are shown in Fig. 1. 
271 

Jagai eta/. Environmental Health (2017) 16:38 

Average Monthly Summer 

Age-Adjusted Hospitalization 

Rate (per 100,000 population) 

RUCC Category 

t metropohtan urbanized 

2 me!ropo!~an urt>aniZe<l (< 1 m!!) 

3 non-metropolitan urbanized 

4 less urbanize<! 

5 !hln!y populated 

Page 3 of lO 

N 

A 

rate for heaHtress mness (per 
272 

Jagai et a!. Environmental Health (20 17) 16:38 

Urban/rural stratification 

Counties were categorized into five urban/rural strata 

using Rural Urban Continuum Codes (RUCC) [44]. The 

original nine continuum codes were aggregated into five 

strata for this analysis: RUCCI (original RUCCI), metropolitan urbanized, (>1 million population); RUCC2 (original RUCC2 and RUCC3), metropolitan urbanized(< 1 

million population); RUCC3 (original RUCC4 and 

RUCCS), non-metropolitan urbanized; RUCC 4 (original 

RUCC6 and RUCC7), less urbanized; RUCC5 (original 

RUCC8 and RUCC9), thinly populated. 

Temperature data 

Daily weather data for the 28-year study period were obtained from the Midwest Regional Climate Center [45]. 

These data were collected from 235 weather stations located throughout the state of Illinois. Of these, 81 stations only provided data on precipitation and were not 

used for this analysis. The remaining 154 stations provided data on temperature for some or all of the 28-year 

study period. Most counties had at least one station that 

provided data and several had more than one station 

(Fig. 2). Counties without a monitoring station were 

assigned temperature from the nearest monitoring station. Data collected at each station included daily maximum, minimum, and mean temperature. Utilizing aU 

available data for the county, we calculated average 

monthly maximum temperature, minimum temperature, 

and mean temperature, in degrees Celsius, for each summer month, May-September, in the study period. 

Covariate data 

For each Illinois county, we complied the percent of 

population below the poverty level, percent of population that was non-Hispanic Black, and percent of population that was Hispanic [43]. Covariate data for the 

years 1987-1994, 1995-2004, and 2005-2014 were obtained from the 1990, 2000, and 2010 Census, 

respectively. 

Statistical analysis 

We assessed associations between monthly average maximurn temperature and age-adjusted monthly rates of hospitalizations for HSI at the county-level. All analyses were 

stratified by the five urbanization strata. The association between monthly mean temperature -with monthly county 

hospitalization rates for HSI were assessed using random 

slope, random intercept multi-level linear regression 

models. County of residence was considered a fixed effect 

and temperature as the random effect (Eq. 1 ). In addition, 

analyses were adjusted for county level covariates including, 

percent of population below the poverty level, percent of 

the county population that was non-Hispanic Black, and 

percent of population that was Hispanic. 

Page 4 of 10 

(1) 

Where: 

yt1 = outcome rates (HSI hospitalization) for the ith 

county and the lh month, 

X1 ~indicator variable for the ith county (fixed effect), 

xii =exposure measurement (mean temperature) for 

the i'h county and the fh month (random effect). 

In this model X1 represents a fixed effect for each 

county and Xti• the mean temperature, accounts for a 

random effect. Models were also adjusting for countylevel population below the poverty level, percent of the 

county population that was non-Hispanic Black, and 

percent of population that was Hispanic. 

Results are reported as a change in hospitalization rate 

per 1 "C change in maximum monthly average 

temperature and 95% confidence intervals (Cis). To 

evaluate whether urban/rural differences in HSI rates 

might be attributable to a severe heat wave in 1995 that 

impacted much of the Midwest, including Illinois, and 

resulted in an estimated 739 fatalities [18] in the most 

populous urban county in lllinois (Cook County), analyses were conducted with and without 1995 data. Analyses were conducted using R version 3.3.1 (R 

Foundation for Statistical Computing) and SAS (SAS Institute, Cary, NC), version 9.4. 

This work, that involved the analysis of a dataset that 

had personal identifiers removed or grouped into categories (such as age) was determined not to involve human research subjects by the UIC Institutional Review 

Board (Protocol 2013-0172). 

Clinical and economic analyses 

Comorbidities of individuals hospitalized for HSI were 

identified using the nine additional!CD-9-CM diagnosis 

codes. Conditions that are clearly chronic (essential 

hypertension, diabetes) were not considered. Those that 

are acute (syncope or fainting; dehydration with electrolyte abnormality), chronic but potentially worsened by 

heat stress, or acute due to heat stress (renal insufficiency, atrial fibrillation) were considered. Furthermore, 

some conditions (urinary tract infection) may have 

developed after the patient had been admitted to the 

hospital. The hospital discharge dataset contained information about length of stay and charges for each admission that we tabulated. We used the U.S. Bureau of 

Labor Statistics data to convert hospital charges to 2014 

dollars [46]. 

Results 

From 1987 to 2014, 8856 hospitalizations for HS! occurred in Illinois in the months of May through September. Of those, 136 were not residents of Illinois 

(primarily these individuals were residents of Missouri 
273 

Jagai et at. Environmental Health {2017) 16:38 

Average Summer Monthly 

Maximum Temperature 

In degrees Celsius 

• Stat•on Locauon 

-2451-2550 

25.51. 26 50 

26.51. 27 50 

27.51 • 28.50 

- 28.51 • 29 50 0 15 30 

Pages of 10 

N 

A 60 90 
274 

Jagai eta!. Environmental Health (2017) 16:38 

or Indiana) and 148 were residents of Illinois with an 

unknown county of residence, leaving 8667 residents of 

Illinois whose county of residence was known. All analyses described herein are limited to these 8667 cases. 

The annual mean number of HSI hospitalizations was 

308 cases (range: 69-1511). Excluding 1995, the annual 

mean was 254 cases (range: 69-508). Males accounted 

for 5322 (61.7%) of cases. The largest number of HSI 

hospitalizations and highest rate was seen in those aged 

~80 years (Table 1). Within each age category, rates of 

hospitalizations generally increased within decreasing 

urbanicity. However, in the older age category, 80+ 

years, the highest rates were seen in the metropolitan 

(> 1 million population) counties. 

HSI hospitalization rates varied substantially across 

counties (Fig. 1). The mean summer age-adjusted rate 

per county ranged from 4.46 cases/100,000 population 

(Pope County) to <1 case/100,000 population (16 counties). Cook County, that contains the City of Chicago, 

accounted for 3731 (44.6%) of all cases over the 28-year 

period, but the lowest age-adjusted rate (0.13/100,000 

population). Nearly half (49.1%) of HSI hospitalizations 

among Illinois residents occurred during the month of 

july; excluding data from 1995 that percent was 42.6%. 

In general, the highest summer temperatures are seen in 

the southern part of the state, which is also the least urbanized area of Illinois (Fig. 2). 

A significant association between mean monthly maximum temperature and HSI hospitalization rates by 

county was observed for Illinois overall (Fig. 3). For 

Illinois counties overall, a 1 ac increase in maximum 

monthly average temperature was associated with a 0.12 

increase in rate of hospitalizations per 100,000 population (95% Confidence Interval (Cl): 0.07, 0.17). The 

strongest association, though not significant at a p = 0.05 

level, was seen in the most thinly populated stratum, 

Page 6 of 10 

where a 1 °C increase in maximum monthly average 

temperature was associated with a 0.34 (95% CI: -0.10, 

0.78) increase in HSI hospitalization rate per 100,000 

population. By comparison, a 1 °C increase in maximum monthly average temperature was associated 

with a 0.02 (95% Cl: -0.003, 0.04) increase in HSI 

hospitalization rate per 100,000 population in the 

metropolitan urban (> 1 million population) stratum. 

Excluding the 1995 data had minimal impact on the 

monthly temperature-monthly hospitalization association, with the exception of the thinly populated strata, 

that demonstrated a large decrease in the effect estimate (Fig. 3). 

Sensitivity analysis included an evaluation of associations with monthly minimum temperature and mean 

monthly temperature. Due to the high correlation 

between maximum, minimum and mean temperature, 

there was minimal change in effect estimates and the 

overall trends demonstrated remained the same (data 

not shown). 

The mean and median length of an HSI hospital stay 

was 3.7 and 2.0 days, respectively (range: 1-122 days). 

Total and mean per person hospital charges in 2014 

dollars were $167.7 million and $20,050, respectively. 

The most common concurrent diagnoses among HSI 

cases were dehydration, electrolytes/acid-base abnormalities, and acute renal failure (Table 2). Other 

concurrent conditions known to be associated with 

heat stress include syncope and rhabdomyolysis. 

Rhabdomyolysis, that can lead to multisystem organ 

failure, was more common in the younger age categories (chi square p < 0.0001). While individuals <50 years 

of age accounted for 26.2% of HSI hospitalizations 

overall, they accounted for 50.3% of HSI cases complicated by rhabdomyolysis. In addition, several chronic 

conditions were common among cases of HSI, 

Table 1 Number and overall rate of summer hospitalizations of heat-stress illness {per 100,000 population) over the 28-year study period by 

ruraVurban stratification (RUCC1-metropolitan urbanized (> 1 million population); RUCC2-metropolitan urbanized ( < 1 million population); 

RUCC3-non-metropolitan urbanized; RUCC 4-less urbanized; RUCCS-thin~ populated) and by age categories 

RUCC 3()-39y 50-59y All 

Count Count 

RUCC2- metropolitan {< 1 19 26 79 53 78 123 157 151 176 187 1029 

million pop.) (009) (0.25) (0.17) (0.25) (0.39) (0.60) (0.78) (1.30) (218) (0458) 

RUCC3 non-metropolitan 15 7 61 38 68 82 111 74 124 141 706 

urbanized (0.05) (0.37) (0.24) (043) (0.50) (0.80) (0.67) (1.51) (2.61) (0.594) 

RUCC4 - less urbanized 42 16 121 58 155 155 178 181 194 268 1325 

(0.08) (0.57) (0.31) (0.74) (0.70) (0.96) (1.20) (1.71) (3.61) (0.850) 

RUCCS - thlnly populated 0 8 11 11 12 11 15 17 11 98 

(0.00) (0.71) (1.26) (1.08) (1.04) (1.07) (1.61) (2.48) (2.86) (1.158) 

All 102 128 539 298 721 986 1164 1146 8667 

(0.05) (0.221 (0.12) (0.28) (041) (0.60) (0.83) (0.503) 
275 

Jagai et of. Environmental Health (2017) 16:38 Page 7 of 10 

Fig. 3 Estimated change in heat-stress illness per 1 "C change in maximum monthly average temperature (after adjustment for county percent below 

poverty level, percent population Black. and percent population Hispanic) and 95% confidence intwals for ail counties and by ruraVurban stratification 

(RUCCl-metropolitan urbanized(> 1 million population); RUCC2-metropolitan urbanized(< 1 million population); RUCC3-non-metropolitan urbanized; 

RUCC 4-less urbanized; RUCC5-thin!y populated) for all study years, 1987-2014, and excluding 1995, the year of the heatwave 

hypertension (27%), diabetes (8.8%), congestive heart 

failure (7.4%), and chronic obstructive pulmonary 

disease (5.1%). 

Discussion 

We assessed the association between the average 

maximum monthly temperature and rates of HSI 

hospitalization among Illinois counties. We utilized data 

for at 28-year study period, 1987-2014 focusing on the 

summer seasons (May to September). Previous epidemiological literature has focused on urban areas. Our 

study covers the entire state of Illinois and therefore we 

were able to assess differences by urban/rural strata. 

We collapsed the nine rural urban continuum codes 

[44] into five strata to assess the relationship between 

Table 2 Most common co-morbid diagnoses listed with 

hospitalizations for heat-stress illness in l!linois, 1984-2014. Note that 

not sum to 100% as hospitalized patients typically 

276.1. 276.2. 276.3. 2764, 1445 (16.7) 

276.7, 276.8. 276.9 

Acute renal failure 584, 584.5, 584.6. 584.7, 584.8, 1021 (11.8) 

594.9 

Urinary tract ·Infection 599.0 808 (9.3) 

Syncope {fainting} 780.2 781 (9.0) 

Rhabdomyolysis 728.88 549 (6.3) 

Atrial fibrillation 427.31 514 (5.9) 

Respiratory failure 518.81 299 (3.5) 

Altered mental status 293.0. 780.02 92 (11) 

mean monthly maximum temperature and hospitalizations for HSI along the continuum of urban metropolitan to thinly populated areas. In Illinois, we found that 

HSI hospitalization rates and the temperaturehospitalization response function was the strongest in 

the thinly populated strata. This stratum is the most 

isolated strata from the urban and suburban centers in 

the state. These results are consistent with recent studies 

that demonstrated elevated risk in rural areas for emergency room visits for HSI across the U.S. [41, 47] and in 

North Carolina [40], though those studies did address 

hospitalization. 

There are several possible factors contributing to susceptibility of the most rural areas to heat-stress illness. 

Studies of urban heat waves have demonstrated that living alone, lack of air conditioning, and underlying medical conditions are risk factors for mortality {13, 15]; 

these same factors may affect residents in rural areas. 

Particularly in Illinois, following the 1995 heat wave, 

several prevention measures were put in place in the 

City of Chicago, including heat warning systems, community outreach initiatives, and cooling centers [13]. 

Similar efforts may not have been implemented to a 

comparable extent in rural areas. 

In Illinois, the counties identified as thinly populated 

are also agricultural counties. The relatively high proportion of the population engaged in physically-demanding, 

outdoor work in those counties may account for the 

steeper slope of the temperature-HSI association (Fig. 3). 

Our data demonstrated a more pronounced difference in 

rates by urban/rural strata in those less than 60 years of 

age, suggesting that occupational factors might place 

workers at risk for HSI that is consistent with previous 

literature [37, 38]. Previous literature regarding the use 
276 

Jagai eta!. Environmental Health (2017} 16:38 

of hospitalization data has suggested that hospitalizations 

in rural areas may be underreported compared \-Vith urban 

areas [40]; therefore, the effect demonstrated in rural areas 

may be an underestimate of the true effect of heat in rural 

areas of Illinois. 

Exposure to extreme heat is known to have a complex 

set of physiological effects on multiple organ systems. We 

found tluid and electrolyte balance and acute failure to be 

the two most common comorbidities associated with HSI 

in Illinois that is consistent with pr€\ious studies [48, 49]. 

Increased risk of hospitalization among the elderly for fluid 

and electrolyte disorders, renal failure, urinary tract infection, septicemia, and heat stroke heat wave days compared 

with non-heat wave days has been documented [50]. The 

costs associated with heat events can also have significant 

impacts. Previous analyses of the California heat wave, 

which lasted about 15 days, estimated the total costs to be 

$5.4 billion dollars (in 2008 dollars) of which $2.8 billion 

was the cost of hospitalizations [25, 51]. While our results 

are not directly comparable, since we are not evaluating a 

specific heat wave, we found that total hospitalizations in 

Illinois for HSI cost $167.7 million dollars (2014 dollars) for 

the 28-year study period. Additionally, the $167.7 million in 

hospital costs is only a portion of the total economic burden. The total of 32,564 days spent in hospitals by those 

with HSI represents a substantial burden of indirect costs. 

Improved and targeted awareness campaigns regarding the 

health impacts of heat may reduce the burden of associated 

healthcare costs. 

Our analysis is limited in a few ways. First, the number of 

HSI hospitalizations is likely to be underestimated. Prior 

studies have identified HSl hospitalizations as we have, 

based on either an ICD-9-CM code of 992 or E900 or both 

[12, 52]. However, a limitation of this approach is that 

health care providers must recognize that an individual's 

symptoms that can be non-specific - are due to heat in 

order for the condition to be coded as being heat~related. 

Morbidity due to a variety of health conditions, including 

renal, cardiac, and respiratory diagnoses can increase with 

heat. A study of Medicare beneficiaries found that only a 

small subset of excess heat~related hospitalizations were 

coded with ICD-9 codes 992 or £900 [53]. Thus, although 

these ICD-9 codes may be relatively specific for HSI they 

may have limited sensitivity for the broad range of illness 

exacerbated or caused by heat exposure when the role of 

ambient heat is not recognized by clinicians. Therefore, the 

estimated 8667 cases of HSI hospitalizations described here 

are likely an underestimate of the burden of disease attributable to ambient heat in Illinois during 1987-2014. Due to 

the low number of hospitalizations, we were provided 

monthly aggregated data that limited the types of analyses 

possible. We were could not consider a case-crossover analysis which would have been appropriate for this acute and 

rare outcome. In addition, we did not have the statistical 

Page 8 of 10 

power required to consider daily associations but needed to 

aggregate by month. Therefore, we were not able to assess 

lagged associations between temperature and hospitaliza~ 

tions for HSI but rather, were only able to assess monthly 

assodations. Second, maximum temperature exposure was 

based on county of residence identified in the 

hospitalization dataset It is possible that heat exposure 

may have occurred in a different county. However, this 

would bias our results to the null and we expect this error 

to be minimal in Hlinois as neighboring counties do not experience significantly different temperature patterns. A 

third limitation is the use of hospital charges to estimate 

the direct medical costs of HSI hospitalizations. Billed hospital charges are inflated above cost, and thus, do not ac~ 

curately capture the direct medical costs of HSl 

hospitalizations in Illinois. Fourth, it is not known to what 

degree general disparities in access to hospital care in rural 

vs. urban areas may contribute to the differences in HSI 

hospitalizations among Illinois counties. 

Reduction of HSI risk in thinly population rural areas 

may require different strategies than in urban areas, given 

the low population density and high prevalence of agricultural work Input from emergency preparedness specialists 

would be useful in identifYing effective methods for alerting people, particularly those working in agriculture, with 

timely updates from local offices of the National Weather 

Service. Such alerts might include reminders for rest, 

water, and shade breaks, County health departments in 

rural areas, organizations that address health and social 

needs in rural areas, and agricultural extension offices 

could identify cooling centers and promote their use if 

such initiatives would be shown to be acceptable to local 

communities. Educational initiatives for rural health care 

providers could include methods to increase awareness 

among residents, to increase fluid intake during hot weather. Given the high frequency of acute renal failure and 

rhabdomyolysis, promoting fluid intake is critical, particularly for those who engage in exertional activities. Prevention efforts should account for U.S. National Climate 

Assessment [54] projections of more frequent and extreme 

heat events. 

Conclusion 

Our findings suggest that elevated temperatures may have a 

differential impact in rural counties compared with urban 

counties. Future research should be conducted at the individual level to understand specific pathways of exposure, 

such as occupational, that result in higher rates of HSI in 

rural communities. Prevention of heat-related illness in 

rural areas will require different strategies than urban areas, 

given lower population densities and higher prevalence of 

agricultural work Collaboration among emergency management, community organizations, and local health 

departments is needed to reduce HSI risk in rural counties. 
277 

Jagai et al. Environmental Health (2017) 16:38 

Abbreviations 

Acknowledgements 

The authors would like to thank the Centers for Disease Control and 

Prevention for funding which made this study possible. 

Availability of data and materials 

Authors' contributions 

JSJ 

Competing interests 

All authors declare that they have no competing interests. 

Consent for publication 

Not applicable. 

Ethics approval and consent to partkipate 

This work that involved the analysis of a dataset that had personal identifiers 

8. 

10. 

12. 

13. 

14. 

15. 

16. 

17. 

18. 

removed or grouped into categories (such as age) was determined not to 19. 

involve human research subjects by the U!C Institutional Review Board 

(Protocol 2013-0172). 

Publisher's Note to jurisdictional daims in 

Received: 3 August 2016 Accepted: 30 March 2017 

Published online: 07 April20 17 

4. 

5. 

6. 

20. 

21. 

22 

23. 

24. 

26. 

27. 

28. 

29. 

30. 

Page 9 of 10 

Biometeorot 2cn:!;52(6):471-80. 
278 

Æ 

Jagai eta!. Environmental Health (2017) 16:38 

2C07-2012. reiat;ve r'sk a'!d time series a0aiyses of ba$·c ar'ld 3dvanfed ~:!e 

s"pport. E0won Hea:lh. 2016,15(1):13 

terrperature and hea:-re:ateo illress across Nor~f-t C0ro::na. USA i'!t J 

Siorr'eteoro· /016,60(5):663-7) 

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