## Hydrof luorocarbons and Climate Change

Summaries of Recent Scientific and Policy Papers

Nancy H. Akerman , Ph.D. AAAS Science & Technology Policy Fellow , hosted by the Stratospheric Protection Division , U.S. Environmental Protection Agency1 

### Hydrofluorocarbons and Climate Change : Summaries of Recent Scientific and Policy Papers

This memo summarizes recent scientific reports, articles, books, and policy papers covering the us e of hydrofluorocarbons (HFCs) and their role in climate change. Hydrofluorocarbons are intentionally made greenhouse gases that have no known natural source. They are used in air conditioning, refrigeration, fire retardants, aerosols, solvents, and as blowing agents in the foam sector

. They have widely been adopted as replacements for ch lorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), two classes of ozone

depleting substances (ODS) that are being phased out under the Montreal Protocol on Substances that Deplete the Ozone Layer. A lth ough HFCs currently represent a very small portion of the total greenhouse gas (GHG) emissions , t he studies and papers included here , in addition to other studies, indicate that the usage of HFCs is growing steeply, primaril y due to increases in the air conditioning and refrigeration sectors and as a direct result of the phase out of ozone

- depleting substances

. Because most ODS are also potent GHGs , the actions taken under the Montreal Protocol and its a mendments and a djustments significantly reduced the contributions these gases would have made to global warming by 13 .3 billion tons of carbon dioxide equivalent (CO 2 eq )

. However, i f the use of HFCs is left unchecked, the se emissions reductions gained under the Montreal Protocol may be lost. Hydrofluorocarbons , with the exception of HFC

- 23 , are short

- lived climate pollutants (SLCPs) . T heir atmospheric lifetimes are on the order of a few days to 50 years , with an average around 15 years, as compared to CO 2 which can stay in the atmosphere for t housands of years

. Many of the papers summarized here outline a path forward for the United States and other countries to move away from the use of HFCs, and the benefits that decreased use of HFCs would have for the climate system. Several papers discuss how SLCPs, which include HFCs as well as methane, black carbon, and tropospheric ozone, have impacts on the climate which can be mitigated through international collaborative treaties o r voluntary initiatives. Because of the more immediate climate benefit s that can be made by reductions in SLCP emissions, many authors advocate for two separate climate treaties, one that would address short

- lived pollutants and one that would address the long

- lived pollutant CO 2 . Recent studies have shown that by using read ily available low

- global warming potential (GWP) alternatives to high

- GWP HFCs, as much as 0.5

- degrees Celsius warming can be avoided by the end of the century.
This memo gives one

- to

- two paragraph summaries of fourteen papers and reports that discuss HFCs and climate change, listed in reverse chronological order

. This list is not meant to be an exhaustive list of all documents related to HFCs and climate change, but instead is a starting point from which to consider HFCs and potential policy options to address their role in climate change. The scientific findings generally focus on the rapid increases in use and emissions of HFCs that are projected to continue. For example, measured atmospheric abundances for the commonly used HFCs are on the rise (UNEP , 2011). The policy papers suggest that by acting now, we have the opportunity to stem th e growth of HFC use and avoid an increase in emissions that in three decades could eclipse other climate protection efforts.2

List of Papers Summarized in This Document
Scien tific Papers Xu, Y., D. Zaelke, G. J. M. Velders, V. Ramanathan (2013) The role of HFCs in mitigating 21 st century climate change. Atmospheric Chemistry and Physics 13: 6083

– 6089. [doi:10.5194/acp

- 13

- 6083

- 2013] Hu, A., Y. Xu, C. Tebaldi, W. M. Washington, V. Ramanathan (2013) Mitigation of short

- lived climate pollutants slows sea

- level rise. Nature Climate Change. [doi:10.1038/nclimate1869] Gschrey B., W. Shwartz, C. Elsner, R. Engelhardt (2011) High increase of global F

- gas emissions until 2050. Greenhouse Gas Measurement & Management 1: 85

– 92. Montzka, S. A., E. J. Dlugokencky, J. H. Butler (2011) Non

- CO2 greenhouse gases and climate change. Nature 476: 43

– 50. [doi:10.1038/nature10322] WMO

– World Meteorological Organization (2011) Science Assessment of Ozone Depletion: 2010, Global Ozone Resear ch and Monitoring Project

- Report No. 52, Geneva, Switzerland. Miller, B. R., M. Rigby, L. J. M. Kuijpers, P. B. Krummel, L. P. Steele, M. Leist, P. J. Fraser, A. McCulloch, C. Harth, P. Slameh, J. Mühle, R. F. Weiss, R. G. Prinn, R. H. J. Wang, S. O’Dohe rty, B. R. Greally, P. G. Simmonds (2010) HFC

- 23 (CHF3) emission trend response to HCFC

- 22 (CHClF2) production and recent HFC

- 23 abatement measures. Atmospheric Chemistry and Physics 10: 7875

– 7890. [doi:10.5194/acp

- 10

- 7875

- 2010] National Research Council ( 2010) Climate Stabilization Targets: Emissions, Concentrations, and Impacts Over Decades to Millennia. 298pp. Velders, G. J. M., D. W. Fahey, J. S. Daniel, M. McFarland, S. O. Andersen (2009) The large contribution of projected HFC emissions to future clim ate forcing. Proceedings of the National Academy of Sciences USA 106: 10949

– 10954. IPCC (2007) Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Ch ange
. Core Writing Team, R. K. Pachauri and A. Reisinger, eds. ) IPCC, Geneva, Switzerland, 1 04 pp.
Policy Papers Bianco, N., K. Meek, R. Gasper, F. Litz (2013) Can the U.S. get there from here? Using existing federal laws and state action to reduce greenhouse gas emissions. World Resources Institute. Seidel, S., and J. Bachmann (2013) Domestic policies to reduce the near

- term risks of climate change. C2ES Center for Climate and Energy Solutions. Velders, G. J. M., A. R. Ravishankara, M. K. Miller, M. J. Molina, J. Alcamo, J. S. Daniel, D. W. Fahey, S. A. Montzka, S. Reimann (2012) Preserving Montreal Protocol climate benefits by limiting HFCs. Science 335 (6071), 922

- 923. [doi:10.1126/science.1216414] Victor, D. G., C. F. Kennel, V. Ramanathan (2012) The climate threat we can beat. Foreign Affairs. UNEP

– United Nations Environment Programme (2011) HFCs: A Critical Link in Protecting Climate and the Ozone Layer. 36pp. Jackson, S.C. (2009) Parallel pursu it of near

- term and long

- term climate mitigation. Science 326: 526

– 527. Molina, M. J., D. Zaelke, K. M. Sarma, S. O. Andersen, V. R. Ramanathan, D. Kaniaru (2009) Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions. Proceedings of the National Academies of Science USA 106: 20616

– 20621. [doi: 10.1073/pnas.0902568106]3

Scien tific Papers Xu, Y., D. Zaelke, G. J. M. Velders, V. Ramanathan (2013) The role of HFCs in mitigating 21 st century climate change. Atmospheric Chemistry and Physics 13: 6083

– 6089. [doi:10.5194/acp
- 13
- 6083
- 2013] This paper discusses how the use of low

- GWP substitutes that are as energy efficient as the HFC s they are replacing can avoid as much as 0.5

- degrees Ce lsius (°C) of warming of the global climate system by 2100. By decreasing the use and emissions of high

- GWP HFCs, the radiative forcing (RF) of these SLCP s decreases significantly, in a matter of weeks to decades. T h is paper models the impacts of HFCs on radiative forcing, including recently developed projections of HFC emissions towards the end of the century. It shows that replacing high

- GWP HFCs with already available low

- GWP substitutes that have atmospheric lifetimes of one month or less , or with othe r materials or technologies, can provide 0.35

– 0.5°C of avoided warming. This avoided warming can be in addition to the potential 1°C avoided warming from other SLCP reductions.
Hu, A., Y. Xu, C. Tebaldi, W. M. Washington, V. Ramanathan (2013) Mitigation of short
lived climate pollutants slows sea
- level rise. Nature Climate Change
. [ doi:10.1038/nclimate1869 ] This study investigated the impact of mitigating short

- lived climate pollutants, including HFCs, on global sea

- level rise. Models showed that reducing both CO 2 and SLCP emissions beginning in 2015 would help global temperatures stay below a 2 °C rise from pre

- industrial temperatures, half of which would be due to SLCP reductions. HFCs have the smallest impact on sea level rise behind methane, CO 2 , and black carbon, but reducing SLCPs has a significant impact on sea

level rise, with the rate of sea

- level rise being reduced 24

– 50%, or up to 35 c entimeters

. However, by delaying SLCP mitigation by 25 years, the global temperature will rise more than 2°C above pre

- industrial temperatures and the rate of sea

- level rise will be three to six times higher.
Gschrey B., W. Shwartz, C. Elsner , R. Engelhardt (2011) High increase of global F
- gas emissions until 2050. Greenhouse Gas Measurement & Management 1: 85

– 9 2. This paper presents tables showing the amounts of fluorinated GHGs, or F

- gases, emitted and in banks through 2050, based on data and projections from the Intergovernmental Panel on Climate Change (IPCC) and the United Nations Environment Programme (UNE P) Technology and Economic Assessment Panel (TEAP). Emissions of F

- gases , which include HFCs, perfluorocarbons ( PFCs ) , and sulfur hexafluoride, have increased significantly in recent years and are estimated to rise further. Steep increases in emissions are mostly due to the refrigeration and air conditioning sectors where HFCs are being deployed to replace ozone

- depleting refrigerants. By 2050, total global emissions of F

- gases will amount to 4 gigatons (Gt) CO 2 eq if no mitig ation measures are taken. F

- gases will comprise 7.9% of projected total anthropogenic CO 2 emissions in 2050, up from ~1.3% in 2004. For significant reductions in future emissions of F

- gases, additional efforts from both developed and developing countries a re needed.

Montzka , S
. A
. , E. J. Dlugokencky , J. H. Butler (2011) Non
- CO2 greenhouse gases and climate change. Nature 476:43

– 50. [doi: 10.1038/nature10322]4

This review paper summarizes human activities and natural processes that emit non

- CO 2 GHGs, and explores the impact of these chemicals on radiative forcing and climate change. In 2008, the 15 Gt CO 2 eq per year contribution from non

- CO 2 GHGs accounted for 30% of all human

related, long

- lived GHG emissions, with HFCs contributing 0.5 Gt CO 2 e q per year
. L arge cuts in anthropogenic emissions of both long

- and short

- lived GHGs could stabilize climate forcing fairly rapidly, because non

- CO 2 GHGs account for about one

- third of total CO 2 eq emissions and 35

– 45% of total climate forcing from all long

- lived GHGs. Mitigating non

- CO 2 GHG emissions could also reduce costs for overall climate mitigation, improve air and water quality, reduce acid deposition, and decrease eutrophication of aquatic ecosystems.

WMO

– World Meteorological Organization (20 11) Science Assessment of Ozone Depletion: 2010, Global Ozone Research and Monitoring Project
- Report No. 52, Geneva, Switzerland
. This report contains the most up

- to

- date understanding of ozone depletion, including in

- depth information on HFCs and their effect on the climate system. It reflects the thinking of hundreds of international scientific experts who contributed to its preparation and review. Tropospheric abundances and emissions of HFCs increased from 2006 levels. HFC emissions wer e mainly from Europe, Asia, and North America. HFCs contribute d about 0.4 gigatonnes of CO 2 eq per year to total global CO 2 eq emissions , and the CO 2 eq emissions of HFCs are increasing by about 8% per year and are expected to continue to grow.
Miller, B. R., M. Rigby, L. J. M. Kuijpers, P. B. Krummel, L. P. Steele, M. Leist, P. J. Fraser, A. McCulloch, C. Harth, P. Slameh, J. Mühle, R. F. Weiss, R. G. Prinn, R. H. J. Wang, S. O’Doherty, B. R. Greally, P. G. Simmonds (2010) HFC
- 23 (CHF 3 ) emission trend response to HCFC
- 22 (CHClF 2 ) production and recent HFC
- 23 abatement measures. A tmospheric Chemistry and Physics 10:7875

– 7890. [doi:10.5194/acp
- 10
- 7875
- 2010] This paper reports observed atmospheric concentrations of HFC

- 23, based on global measurements and air samples taken from 1978

– 2009 . By using these observations in models, an emission history for HFC

- 23 was produced and compared with emissions data reported to the United Nations Framework Convention on Climate Change (UNFCCC) and UNEP . Both the models and the reported d ata agree that HFC

- 23 emissions from developed countries dominated all other sources in the 1990s, then began to decline and became constant from 2003

– 2008. Developing countries use of HCFC

- 22 peaked in 2007, along with HFC

- 23 emissions. From 2007

– 2009, HF C

- 23 emissions were reduced largely due to incineration through projects of the Clean Development Mechanism (CDM) of the UNFCCC.
National Research Council (2010) Climate Stabilization Targets: Emissions, Concentrations, and Impacts Over Decades to Millen nia. 298pp. This report quantifies the outcomes of different stabilization targets for greenhouse gas concentrations using scientific analyses, and provides important scientific insights into the relationships between emissions, greenhouse gas concentratio ns, temperatures, and impacts. Under a business

- as
- usual scenario, emissions of HFCs could reach about 6 Gt CO 2 eq in 2050, representing as much as one

- third of the emissions of CO 2 itself required for a stabilization target of 450 parts per million of CO 2 . The authors note that the emission of HFCs from all uses,5

sectors, and nations should be seriously considered when outlining future strategies and for climate stabilization.
Velders, G. J. M., D. W. Fahey, J. S. Daniel, M. McFarland, S. O. Andersen (200 9) The large contribution of projected HFC emissions to future climate forcing
. Proceedings of the National Academy of Sciences USA 1 06 : 10949

– 10954
. [ Accessible at: http://www.pnas.org/content/early/2009/06/19/0902817106.full.pdf+html ] This paper presents baseline scenarios for HFC consumption and emissions to 2050, based on existing policies. These scenarios show that gl obal HFC emissions significantly exceed previous estimates after 2025, with developing country emissions as much as 800% greater than in developed countries in 2050. Global HFC emissions in 2050 are equivalent to 9

– 19% of projected global CO 2 emissions, and contribute a n RF equivalent to that from 6

– 13 years of CO 2 emissions near 2050. In a hypothetical scenario based on a global cap followed by 4% annual reductions in consumption, HFC RF is shown to peak and begin to decline before 2050.
IPCC (2007) Climate Change 2007: Synthesis Report. Contribution of Working Gr oups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R. K. Pachauri and A. Reisinger (eds.)]. IPCC, Geneva, Switzerland, 104 pp. This Synthesis Report, commonly known as AR4, is the most re cent report from the IPCC on climate change. The 100

- year time horizon GWP values in this report for HFCs and other substances are used by EPA. This report provide d a scientific assessment o f climate change, its effects, and options for mitigating and adap ting to climate change. It includes citations of over 6,000 peer

- reviewed scientific documents. The report found that the warming of the climate system is unequivocal, based on observations of increases in global average air and ocean temperatures, as well as widespread melting of snow and ice and rising of the global average sea level. These changes were found to be very likely due to the observed increases in anthropogenic greenhouse gas concentrations, including HFCs, which have increased above a near

- ze ro pre
industrial background concentration.

Policy Papers Bianco, N., K. Meek, R. Gasper, F. Litz (2013) Can the U.S. get there from here? Using existing federal laws and state action to reduce greenhouse gas emissions. World Resources Institute. This report discusses greenhouse gas (GHG) emissions in the United States and the projected future emissions to 2035. I t surmises that the U nited S tates will not reach its target to reduce GHG emissions in the range of 17% below 2005 levels by the year 202 0 without taking additional actions

. It considers what legal and policy tools exist under the current U. S. federal laws that could be used to achieve emissions reductions and what actions could be taken by states. Among the different scenarios explored fo r meeting the U. S. reduction target are specific recommend ation s that the U nited S tates pursue HFC reductions under both the Montreal6

Protocol and under the domestic Clean Air Act. World Resources Institute indicates that HFCs represent the second largest opportunity for GHG emissions reductions in the United States. Seidel, S., and J. Bachmann (2013) Domestic policies to reduce the near
- term risks of climate change. C2ES Center for Climate and Energy Solutions. This paper discusses a domestic policy agenda that the United States could implement to cut domestic emissions of SLCPs (HFCs, methane, and black carbon). The paper advocates U. S. federal government leadership through directed actions by federal agencies to reduce their emissions of SLCPs in addition to new regulatory actions and programs. Federal leadership on HFCs would take the form of a Presidential Executive Order directing agency procurement practices to avoid products with HFCs.
A utomobile air con ditioning is currently the largest source of HFC emissions in the United States , and HFC

- 134a currently is the predominately used coolant for motor vehicle air conditioning

. T h e authors suggest that the U. S. Environmental Protection Agency (EPA) should mo ve forward immediately with the removal of HFC

- 134a f rom the list of acceptable alternatives in the motor vehicle air

- conditioning sector under the EPA’s Significant New Alternatives Policy (SNAP) program, because HFC

- 134a has a GWP of 1430, and other alte rnatives that have lower GWPs are now available in this sector. The removal of HFC

- 134a from acceptable use in motor vehicle air conditioning, and from other sectors such as refrigerants and foams as new alternatives become available, would have environmen tally beneficial impacts. The authors also suggest the EPA should evaluate the costs and benefits of implementing mandatory recycling and other HFC management practices under the domestic Clean Air Act.
Velders, G.J.M., A. R. Ravishankara, M.K. Miller, M. J. Molina, J. Alcamo, J. S. Daniel, D. W. Fahey, S. A. Montzka, S. Reimann (2012) Preserving Montreal Protocol Climate Benefits by Limiting HFCs. Science 335 (6071), 922
- 923. [DOI:10.1126/science.1216414 ] This article proposes using the Montreal Protocol to regulate HFCs in order to preserve the climate benefits already gained from phasing out ODS under the Montreal Protocol. Atmospheric abundances of major HFCs have increased 10 to 15% per year in recent years, and could increase substantially due to demand, particularly in developing countries, if no regulations are put in place. In an upper

- range business

- as
- usual scenario, global RF from HFCs increases from approximately 0.012 W/m 2 in 2010 to 0.25

– 0. 40 W/m 2 in 2050, which corresponds to 14 to 27% of the increase in CO 2 forcing. However, if the current mix of HFCs (average lifetime of 15 years and average GWP of 1600) were replaced by HFOs and other alternatives with lifetimes less than 1 month and GW P less than approximately 20, the total HFC RF contribution in 2050, even under the high

- emission scenario, would be less than the current forcing from HFCs. The two main areas where HFC use can be reduced are (a) through the use of alternative technolo gies and lower

- GWP alternatives to HFCs, and (b) the reduction of HFC emissions through better containment and end

- of

- life practices. The authors suggest that t he Montreal Protocol, with its infrastructure such as the Multilateral Fund, is an ideal institu tion through which HFCs can be regulated.7

Victor, D. G., Kennel, C. F., Ramanathan, V. (2012) The Climate Threat We Can Beat. Foreign Affairs. This essay discusses the climate benefits of addressing SLCPs , such as methane, black carbon, and HFCs. It includes a few brief examples of adopting existing technology, regulation, and market

- based incentives that have led to decreases in emissions in various sectors. The authors also stress the importance of how i nternational organizations can fund networks so that local authorities and experts around the world can share information with each other about how to assess and best respond to growing climate change.
United Nations Environment Programme (UNEP), HFCs: A Critical Link in Protecting Climate and the Ozone Layer, 2011. 36pp. This Synthesis Report discusses the current contribution to climate forcing by HFCs and the linkages to the ODS phaseout. From 2004 to 2008, HFC emissions (excluding HFC

- 23) increased by approximately 8% per year . The consumption of HFCs is projected to exceed by 2050 the peak consumption level of CFCs in the 1980s and will offset much of the climate benefits gained by the phase

- out of CFCs and other ODS under the Montreal Protocol

. The au thors note the importance of the projected HFC emissions growth, which would be equivalent to 7 to 19% of the CO 2 emissions in 2050 based on the IPCC’s Special Report on Emissions Scenarios (SRES) and equivalent to 18

- 45% of the CO 2 emissions based on the IPCC’s 450 ppm CO 2 emissions scenario. This report also notes that there are options available to minimize climate impacts from HFCs including the use of alternative methods and processes, and use of more climate

- friendly alternatives. Jackson, S.C. (2009 ) Parallel pursuit of near
- term and long
- term climate mitigation. Science 326: 526

– 527. This paper advocates two separate treaties to deal with climate pollutants: one treaty for short

and medium

- lived climate pollutants, and one treaty to focus exclusive ly on reduction of long

term climate pollutants. Short

- lived pollutants , such as HFCs, black carbon, and tropospheric ozone, and medium

- lived pollutants such as methane will account for 57 to 60% of the positive RF generated in the next 20 years, and 7 of the top 10 pollution

- generating activities create short

or medium

- lived pollutants that would be overlooked by mitigation strategies that focus solely on long

- lived pollutants.

Molina , M. J., D. Zaelke , K. M. Sarma , S. O. Andersen, V. R. Ramanathan, D. K aniaru (2009) Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions
. Proceedings of the National Academies of Science USA 106 : 20616

– 20621
. [ doi: 10.1073/pnas.0902568106 ] This arti cle urges “fast action” regulatory measures that can begin within 2

– 3 years, be implemented in 5

– 10 years, and produce a climate response within decades. These fast actions would mostly cover SLCPs , and be enacted in addition to long

- term CO 2 policies. HFCs, black carbon, tropospheric ozone, and other SLCPs can be addressed through existing treaties and local air pollution policies, along with funding and technology transfer through existing institutions.