Understanding the Science of Climate Change

Talking Points – Impacts to the Great Lakes

Natural Resource Report NPS/NRPC/CCRP/NRR—2010/247

National Park Service

U.S. Department of the Interior

Natural Resource Program Center
ON THE COVER

Sunset over Lake Superior in Apostle Islands National Lakeshore; NPS photo.
Understanding the Science of Climate Change

Talking Points – Impacts to the Great Lakes

Natural Resource Report NPS/NRPC/CCRP/NRR—2010/247

Amanda Schramm

National Park Service Pacific West Region

909 First Avenue

Seattle, WA 98104

Rachel Loehman

Rocky Mountain Research Station

Fire Sciences Laboratory

5775 West US Hwy 10

Missoula, MT 59808-9361

With special thanks to the US Forest Service’s Rocky Mountain Research Station and contributions from (in alphabetical order): 

Jay Austin, Gregg Bruff, Hannah Campbell, Maria Caffrey, Louise Hose, Bob Krumenaker, Brent Lofgren, Mark Lynott, Joy Marburger, Jerrilyn Thompson and Leigh Welling. Layout and design: Sara Melena, Angie Richman, Caitlin Shenk, and Katherine 

Stehli.

September 2010

U.S. Department of the Interior

National Park Service

Natural Resource Program Center

Fort Collins, Colorado
The Natural Resource Publication series addresses natural resource topics of interest and applicability to a broad 

readership in the National Park Service and to others in the management of natural resources, including the scientific 

community, the public, and the NPS conservation and environmental constituencies. Manuscripts are peer-reviewed 

to ensure the information is scientifically credible, technically accurate, appropriately written for the intended audience, and is designed and published in a professional manner.

Natural Resource Reports are the designated medium for disseminating high priority, current natural resource management information with managerial application. The series targets a general, diverse audience, and may contain 

NPS policy considerations or address sensitive issues of management applicability. Examples of the diverse array 

of reports published in this series include vital signs monitoring plans; monitoring protocols; “how to” resource 

management papers; proceedings of resource management workshops or conferences; annual reports of resource 

programs or divisions of the Natural Resource Program Center; resource action plans; fact sheets; and regularly-published newsletters.

Views, statements, findings, conclusions, recommendations and data in this report are solely those of the author(s) 

and do not necessarily reflect views and policies of the U.S. Department of the Interior, National Park Service. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the U.S. 

Government.

This report is available from the Natural Resource Publications Management website:

( http://www.nature.nps.gov/publications/NRPM )

Please cite this publication as:

Schramm, A and R. Loehman. 2010. Understanding the science of climate change: talking points - impacts to the 

Great Lakes. Natural Resource Report NPS/NRPC/CCRP/NRR—2010/247. National Park Service, Fort Collins, 

Colorado.

NRInfo Reference URL: http://nrinfo/Reference.mvc/Profile?code=2165147

Climate Change Response Program webpage: http://www.nps.gov/climatechange/docs/GreatLakesTP.pdf

NPS 920/105620, September 2010

National Park Service ii
Contents 

Introduction ............................................................................................................................................................1

Climate Change Impacts to the Great Lakes ............................................................................................................ 2

Summary.........................................................................................................................................................................................2

List of Parks and Refuges .............................................................................................................................................................3

Sectors:

 Temperature............................................................................................................................................................................4

 The Water Cycle .....................................................................................................................................................................5

 Vegetation................................................................................................................................................................................7

 Wildlife ....................................................................................................................................................................................9

 Disturbance........................................................................................................................................................................... 10

 Cultural Resources................................................................................................................................................................12

 Visitor Experience.................................................................................................................................................................13

No Regrets Actions .................................................................................................................................................15

Global Climate Change...........................................................................................................................................18

Sectors:

 Temperature and greenhouse gases................................................................................................................................... 18

 Water, Snow, and Ice.............................................................................................................................................................21

 Vegetation and Wildlife .......................................................................................................................................................23

 Disturbance...........................................................................................................................................................................26

References ........................................................................................................................................................... 27

iii Climate Change Talking Points NPS/FWS—2010
National Park Service 1

Purpose

Climate change presents significant risks to our nation’s natural and cultural resources. Although climate change was once 

believed to be a future problem, there is now unequivocal 

scientific evidence that our planet’s climate system is warming (IPCC 2007a). While many people understand that human 

emissions of greenhouse gases have significantly contributed 

to recent observed climate changes, fewer are aware of the 

specific impacts these changes will bring. This document is part 

of a series of bio-regional summaries that provide key scientific 

findings about climate change and impacts to protected areas. 

The information is intended to provide a basic understanding of 

the science of climate change, known and expected impacts to 

resources and visitor experience, and actions that can be taken 

to mitigate and adapt to change. The statements may be used to 

communicate with managers, frame interpretive programs, and 

answer general questions from the public and the media. They 

also provide helpful information to consider in developing sustainability strategies and long-term management plans. 

Audience

The Talking Points documents are primarily intended to provide 

park and refuge area managers and staff with accessible, up-todate information about climate change and climate change impacts to the resources they protect. 

Organizational Structure

Following the Introduction are three major sections of the document: a Regional Section that provides information on changes 

to the Great Lakes, a section outlining No Regrets Actions that 

can be taken now to mitigate and adapt to climate changes, and 

a general section on Global Climate Change. The Regional 

Section is organized around seven types of changes or impacts, 

while the Global Section is arranged around four topics.

Regional Section

•	 Temperature 

•	 The Water Cycle (including precipitation, snow, ice, and lake 

levels)

•	 Vegetation (plant cover, species range shifts, and phenology)

•	 Wildlife (aquatic and terrestrial animals, range shifts, invasive 

species, migration, and phenology)

•	 Disturbance (including range shifts, plant cover, plant pests 

and pathogens, fire, flooding, and erosion)

•	 Cultural Resources

•	 Visitor Experience

Global Section

•	 Temperature and Greenhouse Gases

•	 Water, Snow, and Ice

•	 Vegetation and Wildlife

•	 Disturbance

Information contained in this document is derived from the 

published results of a range of scientific research including 

historical data, empirical (observed) evidence, and model projections (which may use observed or theoretical relationships). 

While all of the statements are informed by science, not all statements carry the same level of confidence or scientific certainty. 

Identifying uncertainty is an important part of science but can 

be a major source of confusion for decision makers and the 

public. In the strictest sense, all scientific results carry some 

level of uncertainty because the scientific method can only 

“prove” a hypothesis to be false. However, in a practical world, 

society routinely elects to make choices and select options for 

actions that carry an array of uncertain outcomes. 

The statements in this document have been organized to help 

managers and their staffs differentiate among current levels 

of uncertainty in climate change science. In doing so, the 

document aims to be consistent with the language and approach 

taken in the Fourth Assessment on Climate Change reports by 

the Intergovernmental Panel on Climate Change. However, this 

document discriminates among only three different levels of 

uncertainty and does not attempt to ascribe a specific probability to any particular level. These are qualitative rather than 

quantitative categories, ranked from greatest to least certainty, 

and are based on the following: 

•	 “What scientists know” are statements based on measurable 

data and historical records. These are statements for which 

scientists generally have high confidence and agreement 

because they are based on actual measurements and observations. Events under this category have already happened or 

are very likely to happen in the future.

•	 “What scientists think is likely” represents statements beyond 

simple facts; these are derived from some level of reasoning 

or critical thinking. They result from projected trends, well 

tested climate or ecosystem models, or empirically observed 

relationships (statistical comparisons using existing data). 

•	 “What scientists think is possible” are statements that use a 

higher degree of inference or deduction than the previous 

categories. These are based on research about processes that 

are less well understood, often involving dynamic interactions among climate and complex ecosystems. However, 

in some cases, these statements represent potential future 

conditions of greatest concern, because they may carry the 

greatest risk to protected area resources. 

I. Introduction 
2 Climate Change Talking Points NPS/FWS—2010

II. Climate Change Impacts to the Great Lakes

The Great Lakes bioregion 

that is discussed in this section is shown in the map to 

the right. A list of parks and 

refuges for which this analysis is most useful is included 

on the next page. To help the 

reader navigate this section, 

each category is designated 

by color-coded tabs on the 

outside edge of the document.

Summary

The Great Lakes region is experiencing climatic changes including increased air and water temperatures, changes in precipitation patterns, and a reduction in winter ice. These changes have resultant effects on the natural ecosystems and cultural 

resources within and surrounding the lakes, as well as area recreational opportunities. Warmer lake waters are leading to extended periods of lake stratification, which in turn can reduce the water’s suitability for native coldwater fish species and the 

species they rely on for food. As surface water temperatures warm, some fish species are expected to migrate northward toward 

colder waters, or else suffer population declines. Invasive species from outside the Great Lakes may increasingly find suitable 

conditions within the Lakes as conditions change, further threatening the livelihood of native species. Lake-effect snow may 

see a reduction as both air and water temperatures warm. Less snow in general is likely to impact the winter recreational season, which may also be reduced overall as the cold season shortens. Warmer temperatures and reduced ice are expected to 

increase evaporation, leading to lower lake levels and associated impacts on recreational boating. Changes in the precipitation 

and flooding cycle may lead to significant increases in water contamination from flooded sewage systems. Lower lake levels as 

well as changes in moisture, wind, soil chemistry and storm frequency may expose archeological resources or negatively affect 

their preservation.

Voyagers 

National 

Park

Grand Portage 

National Monument

Isle Royale 

National Park

Huron NWR

Pictured Rocks 

National Lakeshore

Apostle Islands 

National Lakeshore

Whittlesey Creek 

NWR

Hamden 

Slough 

NWR

Crane 

Meadows NWR Saint Croix National 

Scenic Riverway

Rice Lake 

NWR

Big Stone NWR & WMD

Minnesota Valley 

NWR & WMD

Fox River 

NWR

Leopold 

WMD

Green Bay 

NWR

Cedar Point 

NWR

James A. Garfield 

National Historic Site

Iroquois 

NWR

Missisquoi 

NWR

Lincoln Home 

National 

Historic Site

Upper 

Mississippi 

NWR

Chautauqua 

NWR

Indiana Dunes 

National Lakeshore

Theodore 

Roosevelt 

Inaugural National 

Historic Site

Women’s Rights 

National Historic 

Site

Fort Stanwix 

National 

Monument

Saratoga 

National 

Historical 

Park

Eleanor 

Roosevelt 

National Historic Site

Shiawassee 

NWR

Michigan 

Islands 

NWR Fergus 

Falls WMD Sleeping Bear 

Dunes National 

Lakeshore

NPS

FWS

Federal lands

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
National Park Service 3

U.S. National Park Service Units

•	 Apostle Islands NL

•	 Delaware Water Gap NRA

•	 Eleanor Roosevelt NHS

•	 Fort Stanwix NM

•	 Grand Portage NM

•	 Home of Frankiln D Roosevelt NHS

•	 Hopewell Furnace NHS

•	Indiana Dunes NL

•	Isle Royale NP

•	James A. Garfield NHS

•	 Keweenaw NHP

•	 Lincoln Home NHS

•	 Martin Van Buren NHS

•	 Mississippi National River & Recreation 

Area

•	 Perry’s Victory and International Peace 

Memorial NME

•	 Pictured Rocks NL

•	 Saint Croix NSR

•	 Saratoga NHP

•	 Sleeping Bear Dunes NL

•	 Steamtown NHS

•	 Theodore Roosevelt Inaugural NHS

•	Thomas Cole NHS

•	 Vanderbilt Mansion NHS

•	 Voyageurs NP

•	 Women’s Rights NHP

U.S. Fish & Wildlife Service Units

•	 Agassiz NWR

•	 Big Stone NWR & WMD

•	 Cedar Point NWR

•	 Chautauqua NWR

•	 Crane Meadows NWR

•	 Detroit Lakes WMD

•	 Detroit River NWR

•	 Emiquon NWR

•	 Erie NWR

•	 Fergus Falls WMD

•	 Fox River NWR

•	 Glacial Ridge NWR

•	 Gravel Island NWR

•	 Green Bay NWR

•	 Hamden Slough NWR

•	 Harbor Island NWR

•	 Horicon NWR

•	 Huron NWR

•	Iroquois NWR

•	 Leopold WMD

•	 Litchfield WMD

•	 Michigan WMD

•	 Michigan Islands NWR

•	 Mille Lacs NWR

•	 Minnesota Valley NWR & WMD

•	 Missisquoi NWR

•	 Montezuma NWR

NHP National Historic Park

NHS National Historic Site

NL National Lakeshore

NM National Monument

NME National Memorial 

NP National Park 

NRA National Recreation Area 

NSR National Scenic Riverway

NWFR National Wildlife and Fish Refuge 

NWR National Wildlife Refuge

WMD Wetland Management District 

List of Parks and Refuges

Acronym Unit Type

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience

•	 Morris WMD

•	 Necedah NWR

•	 Northern Tallgrass Prairie NWR

•	 Ottawa NWR

•	 Rice Lake NWR

•	 Rydell NWR

•	 Seney NWR

•	 Sherburne NWR

•	 Shiawassee NWR

•	 St. Croix WMD

•	 Tamarac NWR

•	Trempealeau NWR

•	 Upper Mississipi NWFR

•	 West Sister Island NWR

•	 Whittlesey Creek NWR
4 Climate Change Talking Points NPS/FWS—2010

A. Temperature 

What scientists know....

•	 The northern Midwest, including the upper Great Lakes region, warmed by almost 

4°F (2°C) in the 20th century (NAST 2000). 

•	 Based on historical records, extreme heat 

events are occurring more frequently 

in the Great Lakes region (NAST 2000, 

Wuebbles et al. 2003). 

•	 Data for Lakes Michigan, Huron and Superior show that summer water temperatures are rising. Lake Superior’s summer 

surface water temperatures increased by 

4.5°F (2.5°C) between 1979 and 2006, a 

rate approximately double the rate of air 

temperature rise during the same period. 

An earlier start of the stratified season 

significantly increases the period over 

which the lake warms during the summer months, leading to a stronger mean 

summer temperature trend than would be 

expected from changes in summer air temperature alone (Austin and Colman 2007).

•	 Over 15 years leading up to 2002, twothirds of the winters in the Midwest had 

temperatures above the long-term historical winter average. The last spring frost is 

coming earlier and the first autumn frost is 

coming later (Kling et al. 2003, Wuebbles 

and Hayhoe 2003). 

•	 Between 1968 and 2002, mean annual air 

temperature increased at an average rate 

of 0.037 °C (0.067°F) per year at lakes Huron, Erie and Ontario, resulting in an overall 1.3 °C (2.3°F) increase for the 34-year 

period. August surface water temperature 

has risen 0.084 °C annually at Lake Huron 

and 0.048 °C (0.086°F) annually at Lake 

Ontario, resulting in overall increases of 

2.9 °C (5.22°F) and 1.6 °C (2.88°F), respectively, for the same time period. Temperatures at Lake Erie rose a small, but not 

significant, amount over the 34-year span 

(Dobiesz and Lester 2009).

What scientists think is likely... 

•	 Climatic model predictions consistently 

indicate warming in the region (Kling et al. 

2003, Wuebbles et al. 2003).

What scientists think is possible... 

•	 Warming is expected to vary across the 

Midwest. Different models and scenarios 

show different patterns of warming, with 

one model showing an increased warming 

at higher latitudes, and another showing 

more warming at lower latitudes (Wuebbles et al. 2003). 

•	 Based on climate model predictions, summer temperatures in the Great Lakes region are projected to rise by at least 5°F 

(3°C), and as much as 20° F (11°C) by 2100. 

Depending on the model and the scenario 

(high, mid-range or low carbon emission 

predictions), the projected temperature 

changes vary (Kling et al. 2003, Wuebbles 

et al. 2003). 

•	 Summer temperature changes are likely to 

show the greatest increase in the southern 

and western part of the Midwest (Wuebbles et al. 2003). 

•	 Models project that by 2071–2100, modeling suggests that annual water temperature may increase in all of the Great Lakes, 

with the most change in Lake Superior and 

the least in Lake Erie. Summer surface water temperatures are expected to increase 

by up to 6°C (10.8°F) on average (Trumpickas et al. 2009). 

This graphic demonstrates the 

shift in average minimum temperatures in the great lakes 

from 1990-2006. Photo courtesy 

of the National Arbor Day Foundation.

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
National Park Service 5

cantly contribute to lake level changes for 

the first time on record. Increasing summer water surface temperatures, which 

correlate with decreasing winter ice cover, 

have caused evaporation rates to more 

than double since 1980 (Hanrahan et al. 

2010). 

•	 Based on historical data, Lakes Huron, 

Erie, Michigan, and Ontario experienced 

a statistically significant trend toward increased precipitation between the years 

1930 and 2000. During the same time period, streamflows increased in three connecting channels of the Great Lakes: the 

St. Clair, Niagara and St. Lawrence rivers 

(McBean and Motiee 2008).

•	 In Bayfield Wisconsin between 1857 and 

2007, the onset of ice cover occurred an 

average of 1.6 days later per decade, and 

break-up of ice cover has occurred an average of 1.7 days earlier per decade due to 

rising air and water temperatures. Taken 

together, these changes have resulted in an 

approximately 3-day per decade (45 days 

over 150 years) reduction in the ice cover 

period. The most significant changes influencing this average occurred since 1975, 

with the ice season beginning an average 

of 11.7 days later and ending 3.0 days earlier every decade (Howk 2009).

Lake level fluctuations in 

the great lakes prior to 1980 

were predominantly driven by 

changes in precipitation; however, evaporation has begun to 

significantly contribute to lake 

level changes for the first time 

on record. Decrease in lake levels on Lake Superior in Apostle 

Islands National Lakeshore; NPS 

photo.

•	 The average date when spring temperatures warm to 10°C (50°F) in the Great 

Lakes region is projected to advance 24 to 

47 days, while the date when fall temperatures drop to 10°C (50°F) is also projected 

to advance 18 to 51 days by 2071-2100 

(Trumpickas et al. 2009).

B. THE WATER CYCLE

What scientists know....

•	 Ice around the Great Lakes and tributary streams is declining and melting earlier (Robertson et al. 1992, Anderson et 

al. 1996, Magnuson et al. 2000, Austin and 

Colman 2007). 

•	 The timing of Lake Superior’s summer 

overturn advanced two weeks between 

1979 and 2006. On average the date of the 

summer overturn has been half a day earlier each year (Austin and Colman 2007). 

•	 Based on historical records, winter precipitation is becoming more variable than 

summer precipitation (Wuebbles et al. 

2003). 

•	 Lake level fluctuations in Lakes Michigan 

and Huron prior to 1980 were predominantly driven by changes in precipitation; 

however, evaporation has begun to signifiTemperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
6 Climate Change Talking Points NPS/FWS—2010

•	 In Minnesota, measurements of streamflow based on 53 to 101 years of historical 

records in the years leading up to 2002 

show increase in peak flows due to summer rainfall events. The number of high 

flow days also increased. Summer and 

winter base flow increased significantly, 

likely due to wetter summers and more 

frequent snow melt events due to warmer 

winters. Mean annual flow rates changed 

at a rate of 2% per year over the last 50 

years of record, increasing to 8% per year 

over the last 15 years (Novotny and Stefan 

2007).

What scientists think is likely... 

•	 Declines in lake winter ice are expected to 

continue (Wuebbles et al. 2003). 

•	 Warmer temperatures and reduced lake 

ice cover and duration of cover could 

cause an increase in evaporation (Lofgren 

et al. 2002, Wuebbles et al. 2003).

•	 Lake-effect snowfall, which relies on frigid 

winter air temperatures and warmer water 

temperatures, is an important factor for 

the vitality of mesic vegetation. Reductions in snowfall due to higher air temperatures predicted as a result of climate 

change may result in a major decrease in 

the abundance of ecologically and economically important species such as Sugar maple (Acer Saccharum) (Henne et al. 

2007).

•	 The duration of winter ice may become 

shorter in the Great Lakes. Warming temperatures could cause earlier ice melt and 

change stream peak flow, potentially increasing flood risk from spring rainfall 

(Kling et al. 2003, Austin and Colman 

2007). 

•	 Based on historical records, a 2007 study 

found that at the current rate of winter ice 

decline, Lake Superior could have periods 

of little to no open-lake ice during a typical 

winter within three decades (Austin and 

Colman 2007).

•	 A reduction in ice cover coupled with 

warmer temperatures is likely to lead to 

higher levels of evaporation, which could 

result in up to a 2-foot lowering of lake 

levels (USGCRP 2009).

•	 The Great Lakes region will likely grow 

drier overall. Any increases in precipitation will likely be counterbalanced by 

increased evaporation due to temperature increases (Kling et al. 2003). Intense 

short-duration rain storms are projected 

to occasionally break periods of drought 

(UCS 2003).

What scientists think is possible... 

•	 Winter precipitation is expected to increase in the Midwest. Summer precipitation is expected to stay the same or 

decrease (Wuebbles et al. 2003). 

•	 Groundwater levels may decrease. Models 

show some decreases in aquifers and an 

expansion of dewatered areas (Lofgren et 

al. 2002). 

•	 The maximum duration of lake stratification in the Great Lakes could increase 

by as much as 90 days as summer temperatures warm. Such an effect could reduce suitability for coldwater fish species 

(Lehman 2002, Kling et al. 2003, Trumpickas et al. 2009).

This is an image of Lake Superior in Apostle Islands National 

Lakeshore, whose record low 

water occurred in 2007 when 

the lake was 22 inches below 

full. Photo courtesy of NASA 

LandSat and prepared by Neil 

Howk.

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
National Park Service 7

C. VEGETATION

What scientists know....

•	 The growing season has been expanding as spring arrives sooner. The average 

length of winter freeze has been decreasing, with frost days declining in the U.S. 

The first freeze occurring later and last 

freeze occurring earlier has expanded the 

growing season (Wuebbles et al. 2003). 

•	 Increasing levels of carbon dioxide affect 

the physiology of vegetation (Watson et 

al. 1997). 

•	 Cool adapted tree species, such as sugar 

maple and birch, are projected to have 

smaller habitat in the northeastern U.S., 

shifting largely to Canada. Oaks, hickories, 

and pines may see an expansion of potential habitats, although expansion may be 

limited by soil and seed dispersal (Watson 

et al. 1997, USDA 2001, Parmesan 2006). 

What scientists think is likely... 

•	 Increasing carbon dioxide levels could increase the productivity of trees and the 

efficiency with which they use nitrogen 

(Watson et al. 1997). 

•	 Warming temperatures can increase problems related to insects and disease. Because insects and pathogens have shorter 

life spans than most forest vegetation, 

they can respond more rapidly to climate change. A longer growing season 

may mean that more generations of pests 

can attack vegetation, while a shorter and 

warmer winter will mean more successful 

over-wintering for pests. If vegetation has 

been stressed by drought or fire, it is also 

more susceptible to disease and infestation (Watson et al. 1996, Winnett 1998, 

USDA 2001, Hayhoe et al. 2007). 

•	 Wild rice is likely to be adversely affected. 

Deep or flooding waters in the early spring 

could delay germination of seed, leading 

to crop failures. Lower water levels late 

in summer could cause wild rice stalks to 

break under the weight of the fruithead 

or could make rice beds inaccessible to 

These images show current forest types (top) compared to projected forest shift (bottom) due to climate change. Images courtesy of USFS.

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
8 Climate Change Talking Points NPS/FWS—2010

harvesters. Extended droughts could lead 

to more competition with other shallow 

water species (NAST 2000). 

•	 Increased variability of temperature and 

precipitation could be harmful to vegetation and could cause diebacks. Climate 

change models predict higher temperature maxima and more extreme precipitation events. As plants rely on specific 

ranges of temperature and precipitation, 

longer droughts, more flooding events and 

heat waves outside of their normal range 

would stress them. In addition, winters 

with warm snaps may cause trees and 

other vegetation to come out of dormancy, 

which would increase their vulnerability 

to further cold temperatures (Winnett 

1998, USDA 2001). 

•	 Future species migrations may differ from 

the past due to habitat loss and fragmentation, reducing the natural system’s ability 

to respond to global change. In the past, 

species have migrated through intact forests. With human development, there are 

fewer forested sites and individuals within 

a population. This will likely make migration of species adapting to temperature 

and precipitation changes more difficult 

(Iverson et al. 2004).

•	 Increased water temperatures enhance 

biological productivity, which decreases 

dissolved oxygen, and could increase the 

growth of undesirable species, such as 

algae blooms (Poff et al. 2002). 

What scientists think is possible... 

•	 Shorter winters and warming temperatures may lead to invasive species, pests, 

and pathogens and cause redistribution 

of tree species and significant alteration 

of ecosystems (Iverson and Prasad 2002, 

Wuebbles et al. 2003). 

•	 Forest species composition is projected 

to change. Bayfield Peninsula (Wisconsin, 

near Apostle Islands NL) forest composition is modeled to respond to a 5°C (9°F) 

increase in annual temperature by changing from a northern hardwood/boreal mix 

to more southern species (He et al. 2002). 

Paper birch habitat is modeled to virtually disappear from the area under some 

greenhouse gas scenarios (Prasad 1999). 

•	 Predicting the rate of forest composition 

change has proven difficult, although 

some species may not easily adapt if climate change occurs as rapidly as predicted 

(Thompson et al. 1998, Wuebbles et al. 

2003). 

•	 Warmer temperatures may exacerbate the 

effects of ozone on forest growth, including reduced growth, reduced seed production and increased vulnerability to disease 

(Watson et al. 1997, USDA 2001). 

•	 Boreal forests in the Boundary Waters Canoe Area Wilderness of Minnesota, many 

of which exist at the edge of their ranges, 

are expected to give way to grassland/

savanna or temperate hardwood forest in 

the next century (Frelich and Reich 2009).

(Top) Spraying for invasive spotted knapweed at Pictured Rocks 

NL, NPS photo.

(Bottom) Decreased water levels have already begun to affect 

vegetation in the great lakes. 

Image courtesy of Northern 

Wisconsin Daily Press.

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
National Park Service 9

D. WILDLIFE

What scientists know....

•	 Under either forest expansion or contraction, relative mixtures of species in forest 

communities will change. This may cause 

some animal species to be at risk. Greater 

rates of change are associated with greater 

disequilibrium between the habitat needs 

of the species and the habitat realities (i.e., 

temperature and precipitation) (Watson et 

al. 1997, Parmesan and Yohe 2003). 

•	 Changes in climate are having significant 

effects on breeding and winter distribution of birds in North America (Watson 

et al. 1997). 

What scientists think is likely... 

•	 Distribution of fish may change according 

to the temperature of water. Warm water 

fish populations are projected to expand 

northward, while cold water fish populations could decrease (Wuebbles et al. 2003, 

Sharma et al. 2007). 

•	 Warmer temperatures may increase the 

length of summer stratification in lakes 

in the Great Lakes region, creating deep 

water, oxygen-depleted areas. This change 

would negatively impact cold water fish in 

the lakes (Lehman 2002, Kling et al. 2003). 

•	 As spring arrives earlier, mosquitoes and 

black flies could begin hatching earlier in 

the season and may take longer to die off 

as winters become shorter (Reither 2001). 

•	 Earlier springs and later winters may disrupt the timing between lifecycles of predators and prey (Parmesan 2006). 

•	 In Michigan, one study has shown that 

some species of migratory birds are arriving significantly earlier than in the past. 

Although these species appear capable of 

adapting, they rely heavily on specific vegetation. If the vegetation cannot respond 

to climatic changes, the appropriate vegetation may not be available when the birds 

arrive (USGCRP 1996). 

•	 Increasing temperatures and potential 

storminess could disrupt the shallow waters where many fish spawn. These changes would threaten population levels of 

native fish (Poff et al. 2002). 

•	 In 2002, western Lake Erie became temporarily stratified due to an unusually warm 

summer. The affected area was a region 

with maximum depth of 10m in which 

stratification is very rare, but did occur 

during a period (about a week) of very low 

wind. The resulting low dissolved oxygen 

levels near the lake floor were linked to a 

failure of fall recruitment for Burrowing 

mayflies (Hexagenia spp.), an important 

food resource for yellow perch and a major indicator species of the ecological condition of the lake. A trend toward more 

frequent hot summers in the Great Lakes 

(Top) American Badger was first 

recorded at Pictured Rocks NL 

in 2004. Photo of tranquilized 

badger undergoing radio collaring; NPS photo. 

(Bottom) Henry Quinlan, Fish 

and Wildlife Service Fisheries 

biologist weighs a lake sturgeon along the Bad River in 

Wisconsin. This fish species is 

an important biological component of the Great Lakes fish 

community and is listed as either threatened or endangered. 

The lake sturgeon may have a 

hard time coping with climate 

change. FWS photo.

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
10 Climate Change Talking Points NPS/FWS—2010

•	 As lake temperatures increase and the ecosystem is stressed by changing climatic 

conditions, the number of exotic species, 

such as zebra mussels and sea lamprey, are 

projected to increase. Zebra mussels add 

to increased productivity in lakes by outcompeting native species and increasing 

water clarity that leads to accelerated algae 

growth (Poff et al. 2002). 

•	 Warming temperatures and vegetation 

changes may result in increased deer populations at Minnesota’s Boundary Waters Canoe Area Wilderness (Frelich and 

Reich 2009).

E. DISTURBANCE

What scientists know....

•	 Changing runoff patterns result in changing stream channel erosion and deposition 

patterns (Pruski and Nearing 2002). 

•	 Increasing summer air and surface water 

temperatures coupled with a reduction in 

the temperature gradient between air and 

water are destabilizing the atmospheric 

surface layer above Lake Superior, resulting in a 5% per decade increase in surface 

wind speeds above the lake (Desai et al. 

2009). 

•	 In Minnesota, recent mild winters have 

led to a rapid population growth of eastern larch beetle (Dendroctonus simplex 

LeConte), which has resulted in significant mortality for Minnesota Larch stands 

(Frelich and Reich 2009).

•	 A model based on historical voltinism 

(number of generations bred per year) 

for grape berry moth (Paralobesia viteana 

Clemens) under varying scenarios of climate change in Lake Erie and other large 

lakes shows that increases in mean surface 

temperatures >2°C can significantly affect 

insect voltinism (Tobin et al. 2008).

•	 A coastal vulnerability assessment of 22 

coastal national parks found that Great 

Lakes shorelines are considered moderately vulnerable (Pendleton et al. 2010). 

region could lead to recurrent loss of mayfly larvae in shallow areas in this and other 

Great Lakes (Bridgeman et al. 2006).

What scientists think is possible... 

•	 National parks may not be able to meet 

their mandate of protecting current biodiversity within park boundaries for mammals. Park wildlife, able to move northward or to higher elevation to avoid global 

warming impacts, may be forced out of 

the parks and into unprotected habitats 

(Burns et al. 2003). 

•	 Due to vegetation shifts, and thus habitat 

shifts, parks may experience a shift in 

mammalian species greater than anything 

documented in the geologic record. This 

prediction is based on the idea that species will change location as a group. Several researchers have concluded that rapid 

changes on the order of 20 to 50 years are 

possible (Burns et al. 2003). 

•	 Specific changes in mammal populations 

and movements may be hard to predict 

due to the complexity of their interactions with the environment and the rapid 

pace of change that is expected (Burns et 

al. 2003). 

Several Great Lakes may be 

vulnerable to aquatic invasive 

species from the Caspian Sea 

like the Zebra Mussel found in 

Sleeping Bear Dunes National 

Lakeshore; NPS photo. 

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
National Park Service 11

What scientists think is likely... 

•	 Changing precipitation patterns and accompanying lowering of groundwater 

tables may result in alterations to the 

drainage pattern, including renewed or 

accelerated stream bed incision and channel wall erosion, increased sediment transportation and deposition, and drying out 

of wetlands (Tucker and Slingerland 1997, 

Winter 2000). 

•	 Modeling suggests that the increasing 

wind speeds on Lake Superior may lead 

to increases in water current speeds, and 

long-term warming can lengthen the season of stratification and cause the surface 

mixed layer to become shallower. Such 

changes may have significant implications 

for the biogeochemical cycles of large 

lakes, atmospheric circulation along lake 

shores, and the transport of airborne pollutants in regions with many lakes (Desai 

et al. 2009).

•	 A study conducted in Lake Erie showed 

that external phosphorus levels could increase due to increased runoff, excretion 

from invasive dreissenid mussels, and other effects associated with climate change, 

resulting in substantial effects on freshwater ecosystem services (Roy et al. 2010). 

•	 Near shore areas of several Great Lakes 

and most of Lake Erie may be vulnerable 

to aquatic invasive species from the Caspian Sea (Fitzpatrick and Hargrove 2009). 

•	 Rising temperatures and earlier springs 

are likely to increase forest fire hazards, 

lengthen the fire season, and create larger 

fires. These changes could increase atmospheric carbon contributions from forests 

(Watson et al. 1997, Winnett 1998, USDA 

2001, Westerling et al. 2006).

What scientists think is possible... 

•	 Models predict an earlier spring growth 

and marginal increase in peak biomass of 

Cladophora, a form of nuisance algae, in 

Lake Ontario (Malkin et al. 2008).

•	 In southern Wisconsin, model projections 

of 10% to 40% increases in the strength 

of extreme precipitation could result in 

greater potential for flooding. Such flooding could be accompanied by combined 

sewer overflow into the Great Lakes, including a potential by 50% to 120% increase in sewer overflow into Lake Michigan by 2100 (Patz et al. 2008). 

•	 Some resource management strategies 

that could lessen ecosystem disturbances 

(i.e., prescribed fires, assisted migrations, 

restoring species to wilderness) may be 

difficult to enact or limited in effectiveness 

under changed conditions, and may even 

be in conflict with existing policy (Frelich 

and Reich 2009).

(Top) Decreasing lake levels will 

have an impact on park or refuge buildings and facilities, like 

these sunken docks at Apostle 

Islands National Lakeshore; NPS 

photo. 

(Bottom) A coastal vulnerability assessment of 22 coastal national parks found that Great 

Lakes shorelines are considered 

moderately vulnerable. Erosion 

along sand banks on Lake Michigan in Indiana Dunes National 

Lakeshore; NPS photo.

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
12 Climate Change Talking Points NPS/FWS—2010

F. CULTURAL RESOURCES

What scientists know....

•	 Historic structures are vulnerable to 

changes in temperature, wind, and moisture as well as infestation of pests (UNESCO 2007). 

•	 Preservation of archeological resources in 

the earth depends on a delicate balance of 

conditions. Changes to these conditions 

may reduce the change of artifacts’ survival (UNESCO 2007).

•	 Benefits of using local knowledge and traditional practices in resource management 

can help facilitate adaptation to climate 

change (Finucane 2009, IPCC 2008). 

•	 Land use areas that are fixed in place, like 

national parks and Native American reservations, are particularly vulnerable to 

the effects of climate change because they 

cannot adapt by relocating in response to 

changes in natural conditions (Smith et al. 

2001). 

What scientists think is possible....

•	 Increasing frequency and intensity of severe storms and floods may pose threats 

to historic structures ethnographic and 

archeological sites. 

•	 Warmer water may result in accelerated 

biological activity and speed deterioration of submerged cultural resources or 

expanded anoxic conditions and help preserve the resources, such as sunken ships. 

The one certainty is that climate change 

will produce challenges to the preservation of cultural resources that have not 

been faced previously (Nicholls and Klein 

2005).

Historic structures, like the 

Quincy Dry House at Keweenaw National Historical Park are 

vulnerable to changes in temperature, wind, and moisture 

as well as infestation of pests; 

NPS photo.

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
National Park Service 13

G. VISITOR EXPERIENCE

What scientists know....

•	 The winter recreation season in the region 

is becoming shorter and less reliable overall, although some areas have experienced 

an increase in seasonal snowfall over the 

past few decades.

What scientists think is likely....

•	 Reduction in snowpack could significantly reduce opportunities for winter recreational activities such as skiing and snowmobiling (Scott et al. 2008). 

•	 Shoulder seasons will likely begin and end 

earlier in the spring and start and continue 

later in the fall. Opportunities for summer 

activities may extend longer. 

•	 Changes in wildlife composition could 

impact activities in the parks and refuges, 

such as fishing and bird watching.

What scientists think is possible....

•	 Recreational beaches may face closure under climate change due to increased pollution and waterborne pathogens. Heavier 

rainfall, warmer lake waters, and lowered 

lake levels associated with climate change 

could all contribute to beach contamination (Patz et al. 2008). 

•	 There may be increased public health risk 

by the likely expansion of the prevalence 

and range of Lyme and West Nile Virus 

(IPCC 2007b). Infections in foods (e.g., 

fish) could also increase (Patz et al. 2000). 

•	 Longer mosquito and black fly seasons 

could be a nuisance to visitors and may increase the risk of mosquito-borne diseases, 

such as dengue, yellow fever, and West 

Nile virus (Patz et al. 2000, Reither 2001, 

IPCC 2007b).

•	 Lake level fluctuations may affect the viability of recreational marine boating as 

marina operators struggle with the expense and logistics of providing appropriate infrastructure for boaters (Wall 2008).

•	 Park and refuge facilities may be inadequate for new conditions. Recreational 

infrastructure such as fixed docks and 

boat ramps may be too high as lake levels 

decline. Shallow water at docks and anchorages may limit access by deeper-draft 

boats. Navigational hazards and new sand 

bars may be exposed. There may be pressure on managers to lengthen or lower 

docks or dredge shallow areas, and to 

mark navigational water hazards. 

•	 Warmer waters and longer open water 

(non-ice) seasons may “open” boating to 

more people and different kinds of boats. 

Coupled with the increasing frequency 

and intensity of severe storms, however, 

this may lead to increasing issues of visitor 

safety (e.g., groundings, capsizings, etc.) 

and the need for more rescues by the managing agencies. 

(Top) Changes in wildlife composition due to climate change 

will impact activities in the 

parks, such as fishing and bird 

watching; NPS photo.

(Bottom) Reduction in snowpack could significantly reduce 

opportunities for winter recreational activities such as skiing 

and snowmobiling; NPS photo.

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
14 Climate Change Talking Points NPS/FWS—2010

that supports sport fish communities, as 

well as the spawning areas fish depend 

upon for reproduction. Migratory birds 

and other wetland-dependent organisms 

will also likely be impacted. 

•	 Reduced groundwater and stream flows 

may affect the availability of high quality water to support both park and refuge 

ecosystems and facilities. 

•	 Increased temperatures could hinder 

physical activities in parks and refuges, resulting in increased heat exhaustion. 

•	 Increased summer temperatures could 

lead to increased utility expenditures in 

parks and refuges in the summer and, potentially, decreases in the winter. 

•	 Storms on land could create hazardous 

conditions and visitor injuries from falling 

debris, flooding, vehicle accidents, and 

mass wasting (i.e., landslides, mud flows, 

rock falls). 

•	 Increasing frequency and intensity of severe storms and floods may pose threats 

to roads and trails, administrative facilities, 

and other park and refuge resources and 

infrastructure. 

•	 Shallow lake margins could expose new 

land which, depending on local conditions, may become new beaches or mud 

flats. 

•	 Drying of ephemeral wetlands on lake 

margins may adversely affect the food web 

Changes in wildlife composition due to climate 

change will impact activities in the parks, such as 

fishing and bird watching. NPS photo.

Temperature Water Cycle Vegetation Wildlife Disturbance Cultural Resources Visitor Experience
National Park Service 15

III. No Regrets Actions: How Individuals, Parks, Refuges, and 

Their Partners Can Do Their Part

Individuals, businesses, and agencies release carbon dioxide (CO2), the principal greenhouse gas, through burning of fossil 

fuels for electricity, heating, transportation, food production, and other day-to-day activities. Increasing levels of atmospheric 

CO2 have measurably increased global average temperatures, and are projected to cause further changes in global climate, with 

severe implications for vegetation, wildlife, oceans, water resources, and human populations. Emissions reduction – limiting 

production of CO2 and other greenhouse gases - is an important step in addressing climate change. It is the responsibility of 

agencies and individuals to find ways to reduce greenhouse gas emissions and to educate about the causes and consequences 

of climate change, and ways in which we can reduce our impacts on natural resources. There are many simple actions that each 

of us can take to reduce our daily carbon emissions, some of which will even save money.

Agencies Can...

Improve sustainability and 

energy efficiency

•	 Use energy efficient products, such as 

ENERGY STAR® approved office equipment and light bulbs.

•	 Initiate an energy efficiency program to 

monitor energy use in buildings. Provide 

guidelines for reducing energy consumption. Conserve water.

•	 Convert to renewable energy sources 

such as solar or wind generated power.

•	 Specify “green” designs for construction 

of new or remodeled buildings.

•	 Include discussions of climate change in 

the park Environmental Management 

System. 

•	 Conduct an emmisions inventory and set 

goals for CO2 reduction.

•	 Provide alternative transportation options such as employee bicycles and shuttles for within-unit commuting. 

•	 Provide hybrid electric or propane-fueled 

vehicles for official use, and impose fuel 

standards for park vehicles. Reduce the 

number and/or size of park vehicles and 

boats to maximize efficiency.

•	 Provide a shuttle service or another form 

of alternate transportation for visitor and 

employee travel to and within the unit. 

•	 Provide incentives for use of alternative 

transportation methods.

•	 Use teleconferences and webinars or other 

forms of modern technology in place of 

travel to conferences and meetings.

Implement Management Actions

•	 Engage and enlist collaborator support 

(e.g., tribes, nearby agencies, private landholders) in climate change discussions, responses, adaptation and mitigation. 

•	 Develop strategies and identify priorities 

for managing uncertainty surrounding climate change effects in parks and refuges.

•	 Dedicate funds not only to sustainable 

actions but also to understanding the impacts to the natural and cultural resources.

•	 Build a strong partnership-based foundation for future conservation efforts.

•	 Identify strategic priorities for climate 

change efforts when working with partners.

•	 Incorporate anticipated climate change 

impacts, such as decreases in lake levels 

or changes in vegetation and wildlife, into 

management plans.

An interpretive brochure about 

climate change impacts to National Parks was created in 2006 

and was distributed widely. This 

brochure was updated in 2008.
16 Climate Change Talking Points NPS/FWS—2010

•	 Encourage climate change research and 

scientific study in park units and refuges. 

•	 Design long-term monitoring projects and 

management activities that do not rely 

solely on fossil fuel-based transportation 

and infrastructure.

•	 Incorporate products and services that address climate change in the development 

of all interpretive and management plans. 

•	 Take inventory of the facilities/boundaries/species within your park or refuge that 

may benefit from climate change mitigation or adaptation activities.

•	 Participate in gateway community sustainability efforts.

•	 Recognize the value of ecosystem services 

that an area can provide, and manage the 

area to sustain these services. Conservation is more cost-effective than restoration 

and helps maintain ecosystem integrity.

•	 Provide recycling options for solid waste 

and trash generated within the park.

Restore damaged landscapes

•	 Strategically focus restoration efforts, both 

in terms of the types of restoration undertaken and their national, regional, and 

local scale and focus, to help maximize 

resilience.

•	 Restore and conserve connectivity within 

habitats, protect and enhance instream 

flows for fish, and maintain and develop 

access corridors to climate change refugia. 

•	 Restoration efforts are important as a 

means for enhancing species’ ability to 

cope with stresses and adapt to climatic 

and environmental changes. Through restoration of natural areas, we can lessen climate change impacts on species and their 

habitats. These efforts will help preserve 

biodiversity, natural resources, and recreational opportunities.

•	 Address climate change impacts to cultural 

resources by taking actions to document, 

preserve, and recover them. 

Educate staff and the public

•	 Post climate change information in easily accessible locations such as on bulletin 

boards and websites.

•	 Provide training for park and refuge employees and partners on effects of climate 

change on resources, and on dissemination of climate change knowledge to the 

public.

•	 Support the development of region, park, 

or refuge-specific interpretive products on 

the impacts of climate change. 

•	 Incorporate climate change research and 

information in interpretive and education 

outreach programming.

•	 Distribute up-to-date interpretive products (e.g., the National Park Service-wide 

Climate Change in National Parks brochure).

•	 Develop climate change presentations for 

local civic organizations, user and partner 

conferences, national meetings, etc.

•	 Incorporate climate change questions and 

answers into Junior Ranger programs.

•	 Help visitors make the connection between reducing greenhouse gas emissions 

and resource stewardship.

•	 Encourage visitors to use public or nonmotorized transportation to and around 

parks.

Park Service employees install 

solar panels at San Francisco 

Maritime National Historical 

Park (Top); At the National Mall, 

Park Service employees use 

clean-energy transportation to 

lead tours; NPS photos. 
National Park Service 17

The Climate Friendly Parks 

Program is a joint partnership 

between the U.S. Environmental Protection Agency and the 

National Park Service. Climate 

Friendly Parks from around the 

country are leading the way in 

the effort to protect our parks’ 

natural and cultural resources 

and ensure their preservation 

for future generations; NPS image. 

•	 Encourage visitors to reduce their carbon 

footprint in their daily lives and as part of 

their tourism experience.

Individuals can...

•	 In the park or refuge park their car and 

walk or bike. Use shuttles where available. 

Recycle and use refillable water bottles. 

Stay on marked trails to help further ecosystem restoration efforts.

•	 At home, walk, carpool, bike or use public transportation if possible. A full bus 

equates to 40 fewer cars on the road. 

When driving, use a fuel-efficient vehicle.

•	 Do not let cars or boats idle - letting a car 

idle for just 20 seconds burns more gasoline than turning it off and on again.

•	 Replace incandescent bulbs in five most 

frequently used light fixtures in the home 

with bulbs that have the ENERGY STAR® 

rating. If every household in the U.S. takes 

this one action we will prevent greenhouse 

gas emissions equivalent to the emissions 

from nearly 10 million cars, in addition to 

saving money on energy costs.

Reduce, Reuse, Recycle, Refuse

•	 Use products made from recycled paper, 

plastics and aluminum - these use 55-95% 

less energy than products made from 

scratch. 

•	 Purchase a travel coffee mug and a reusable water bottle to reduce use of disposable products (Starbucks uses more than 1 

billion paper cups a year). 

•	 Carry reusable bags instead of using paper 

or plastic bags. 

•	 Recycle drink containers, paper, newspapers, electronics, and other materials. Bring recyclables home for proper 

disposal when recycle bins are not available. Rather than taking old furniture and 

clothes to the dump, consider “recycling” 

them at a thrift store. 

•	 Keep an energy efficient home. Purchase 

ENERGY STAR® appliances, properly 

insulate windows, doors and attics, and 

lower the thermostat in the winter and 

raise it in the summer (even 1-2 degrees 

makes a big difference). Switch to green 

power generated from renewable energy 

sources such as wind, solar, or geothermal.

•	 Buy local goods and services that minimize 

emissions associated with transportation.

•	 Encourage others to participate in the actions listed above.

•	 Conserve water.

For more information on how you can reduce carbon emissions and engage in climatefriendly activities, check out these websites:

EPA- What you can do: http://www.epa.gov/

climatechange/wycd/index.html

NPS- Climate Change Response Program: 

http://www.nps.gov/climatechange

NPS- Do Your Part! Program: http://www.

nps.gov/climatefriendlyparks/doyourpart.

html 

US Forest Service Climate Change Program: 

http://www.fs.fed.us/climatechange/

United States Global Change Research Program: http://www.globalchange.gov/

U.S. Fish and Wildlife Service Climate change: 

http://www.fws.gov/home/climatechange/

“Humankind has not 

woven the web of life. 

We are but one thread 

within it. Whatever we 

do to the web, we do 

to ourselves. All things 

are bound together. 

All things connect.”

 —Chief Seattle
18 Climate Change Talking Points NPS/FWS—2010

IV. Global Climate Change

The IPCC is a scientific intergovernmental, international body established by the World Meteorological Organization (WMO) 

and by the United Nations Environment Programme (UNEP). The information the IPCC provides in its reports is based on 

scientific evidence and reflects existing consensus viewpoints within the scientific community. The comprehensiveness of the 

scientific content is achieved through contributions from experts in all regions of the world and all relevant disciplines including, where appropriately documented, industry literature and traditional practices, and a two stage review process by experts 

and governments.

Definition of climate change: The IPCC defines climate change as a change in the state of the climate that can be identified (e.g. 

using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, 

typically decades or longer. All statements in this section are synthesized from the IPCC report unless otherwise noted.

A. Temperature and 

Greenhouse Gases

What scientists know...

•	 Warming of the Earth’s climate system is 

unequivocal, as evidenced from increased 

air and ocean temperatures, widespread 

melting of snow and ice, and rising global 

average sea level (Figure 1).

•	 In the last 100 years, global average surface 

temperature has risen about 0.74°C over 

the previous 100-year period, and the rate 

of warming has doubled from the previous 

century. Eleven of the 12 warmest years in 

the instrumental record of global surface 

temperature since 1850 have occurred 

since 1995 (Figure 1).

•	 Although most regions over the globe have 

experienced warming, there are regional 

variations: land regions have warmed faster than oceans and high northern latitudes 

have warmed faster than the tropics. Average Arctic temperatures have increased 

at almost twice the global rate in the past 

100 years, primarily because loss of snow 

and ice results in a positive feedback via 

increased absorption of sunlight by ocean 

waters (Figure 2).

•	 Over the past 50 years widespread changes 

in extreme temperatures have been observed, including a decrease in cold days 

and nights and an increase in the frequency of hot days, hot nights, and heat waves.

•	 Winter temperatures are increasing more 

rapidly than summer temperatures, particularly in the northern hemisphere, and 

Figure 1. Observed changes in (a) global average surface temperature; (b) 

global average sea level from tide gauge (blue) and satellite (red) data and (c) 

Northern Hemisphere snow cover for March-April. All differences are relative 

to corresponding averages for the period 1961-1990. Smoothed curves represent decadal averaged values while circles show yearly values. The shaded 

areas are the uncertainty intervals estimated from a comprehensive analysis of 

known uncertainties (a and b) and from the time series (c) (IPCC 2007a).
National Park Service 19

there has been an increase in the length 

of the frost-free period in mid- and highlatitude regions of both hemispheres.

•	 Climate change is caused by alterations in 

the energy balance within the atmosphere 

and at the Earth’s surface. Factors that 

affect Earth’s energy balance are the atmospheric concentrations of greenhouse 

gases and aerosols, land surface properties, 

and solar radiation. 

•	 Global atmospheric concentrations of 

greenhouse gases have increased significantly since 1750 as the result of human 

activities. The principal greenhouse gases 

are carbon dioxide (CO2), primarily from 

fossil fuel use and land-use change; methane (CH4) and nitrous oxide (N2O), primarily from agriculture; and halocarbons 

(a group of gases containing fluorine, chlorine or bromine), principally engineered 

chemicals that do not occur naturally.

•	 Direct measurements of gases trapped in 

ice cores demonstrate that current CO2 

and CH4 concentrations far exceed the 

natural range over the last 650,000 years 

and have increased markedly (35% and 

148% respectively), since the beginning of 

the industrial era in 1750.

•	 Both past and future anthropogenic CO2 

emissions will continue to contribute to 

warming and sea level rise for more than 

a millennium, due to the time scales required for the removal of the gas from the 

atmosphere. 

Figure 2. Comparison of observed continental- and globalscale changes in surface temperature with results simulated 

by climate models using either 

natural or both natural and anthropogenic forcings. Decadal 

averages of observations are 

shown for the period 1906-2005 

(black line) plotted against the 

centre of the decade and relative to the corresponding average for the period 1901-1950. 

Lines are dashed where spatial 

coverage is less than 50%. Blue 

shaded bands show the 5 to 

95% range for 19 simulations 

from five climate models using 

only the natural forcings due 

to solar activity and volcanoes. 

Red shaded bands show the 5 

to 95% range for 58 simulations 

from 14 climate models using 

both natural and anthropogenic 

forcings (IPCC 2007a).
20 Climate Change Talking Points NPS/FWS—2010

•	 Warming temperatures reduce oceanic uptake of atmospheric CO2, increasing the 

fraction of anthropogenic emissions remaining in the atmosphere. This positive 

carbon cycle feedback results in increasingly greater accumulation of atmospheric 

CO2 and subsequently greater warming 

trends than would otherwise be present in 

the absence of a feedback relationship.

•	 There is very high confidence that the 

global average net effect of human activities since 1750 has been one of warming.

•	 Scientific evidence shows that major and 

widespread climate changes have occurred with startling speed. For example, 

roughly half the north Atlantic warming 

during the last 20,000 years was achieved 

in only a decade, and it was accompanied 

by significant climatic changes across most 

of the globe (NRC 2008).

What scientists think is likely...

•	 Anthropogenic warming over the last 

three decades has likely had a discernible 

influence at the global scale on observed 

changes in many physical and biological 

systems. 

•	 Average temperatures in the Northern 

Hemisphere during the second half of the 

20th century were very likely higher than 

during any other 50-year period in the last 

500 years and likely the highest in at least 

the past 1300 years. 

•	 Most of the warming that has occurred 

since the mid-20th century is very likely 

due to increases in anthropogenic greenhouse gas concentrations. Furthermore, 

it is extremely likely that global changes 

observed in the past 50 years can only be 

explained with external (anthropogenic) 

forcings (influences) (Figure 2). 

•	 There is much evidence and scientific consensus that greenhouse gas emissions will 

continue to grow under current climate 

change mitigation policies and development practices. For the next two decades 

a warming of about 0.2oC per decade is 

projected for a range of emissions scenarios; afterwards, temperature projections 

increasingly depend on specific emissions 

scenarios (Table 1). 

•	 It is very likely that continued greenhouse 

gas emissions at or above the current rate 

will cause further warming and result in 

changes in the global climate system that 

will be larger than those observed during 

the 20th century.

•	 It is very likely that hot extremes, heat 

waves and heavy precipitation events will 

become more frequent. As with current 

trends, warming is expected to be greatest 

over land and at most high northern latitudes, and least over the Southern Ocean 

(near Antarctica) and the northern North 

Atlantic Ocean.

What scientists think is possible...

•	 Global temperatures are projected to increase in the future, and the magnitude of 

temperature change depends on specific 

emissions scenarios, and ranges from a 

1.1oC to 6.4oC increase by 2100 (Table 1). 

Table 1. Projected global average surface warming at the 

end of the 21st century, adapted 

from (IPCC 2007b).

Notes: a) Temperatures are 

assessed best estimates and 

likely uncertainty ranges 

from a hierarchy of models of 

varying complexity as well as 

observational constraints. b) 

Temperature changes are expressed as the difference from 

the period 1980-1999. To express the change relative to the 

period 1850-1899 add 0.5°C. c) 

Year 2000 constant composition 

is derived from AtmosphereOcean General Circulation Models (AOGCMs) only. 

Temperature Change (°C at 2090 – 2099 relative to 

1980 – 1999)a,b

Emissions Scenario Best Estimate Likely Range

Constant Year 2000 

Concentrationsa 0.6 0.3 – 0.9

B1 Scenario 1.8 1.1 – 2.9

B2 Scenario 2.4 1.4 – 3.8

A1B Scenario 2.8 1.7 – 4.4

A2 Scenario 3.4 2.0 – 5.4

A1F1 Scenario 4.0 2.4 – 6.4
National Park Service 21

Figure 3. Sea ice concentrations 

(the amount of ice in a given 

area) simulated by the GFDL 

CM2.1 global coupled climate 

model averaged over August, 

September and October (the 

months when Arctic sea ice concentrations generally are at a 

minimum). Three years (1885, 

1985 & 2085) are shown to illustrate the model-simulated 

trend. A dramatic reduction of 

summertime sea ice is projected, 

with the rate of decrease being 

greatest during the 21st century 

portion. The colors range from 

dark blue (ice free) to white 

(100% sea ice covered); Image 

courtesy of NOAA GFDL.

•	 Anthropogenic warming could lead to 

changes in the global system that are 

abrupt and irreversible, depending on the 

rate and magnitude of climate change.

•	 Roughly 20-30% of species around the 

globe could become extinct if global average temperatures increase by 2 to 3oC over 

pre-industrial levels.

B. Water, Snow, and Ice

What scientists know...

•	 Many natural systems are already being affected by increased temperatures, particularly those related to snow, ice, and frozen 

ground. Examples are decreases in snow 

and ice extent, especially of mountain glaciers; enlargement and increased numbers 

of glacial lakes; decreased permafrost extent; increasing ground instability in permafrost regions and rock avalanches in 

mountain regions; and thinner sea ice and 

shorter freezing seasons of lake and river 

ice (Figure 3).

•	 Annual average Arctic sea ice extent hasshrunk by 2.7% per decade since 1978, and 

the summer ice extent has decreased by 

7.4% per decade. Sea ice extent during the 

2007 melt season plummeted to the lowest 

levels since satellite measurements began 

in 1979, and at the end of the melt season 

September 2007 sea ice was 39% below 

the long-term (1979-2000) average (NSIDC 

2008)(Figure 4).

•	 Global average sea level rose at an average 

rate of 1.8 mm per year from 1961 to 2003 

and at an average rate of 3.1 mm per year 

from 1993 to 2003. Increases in sea level 

since 1993 are the result of the following 

contributions: thermal expansion, 57%; 

melting glaciers and ice caps, 28%, melting 

polar ice sheets, 15%. 

•	 The CO2 content of the oceans increased 

by 118 ± 19 Gt (1 Gt = 109 tons) between 

A.D. 1750 (the end of the pre-industrial 

period) and 1994 as the result of uptake 

of anthropogenic CO2 emissions from the 

atmosphere, and continues to increase 

by about 2 Gt each year (Sabine et al. 

2004; Hoegh-Guldberg et al. 2007). This 

Figure 4. Arctic sea ice in September 2007 (blue line) is far below the previous low 

record year of 2005 (dashed line), and was 39% below where we would expect to be 

in an average year (solid gray line). Average September sea ice extent from 1979 to 

2000 was 7.04 million square kilometers. The climatological minimum from 1979 to 

2000 was 6.74 million square kilometers (NSIDC 2008).
22 Climate Change Talking Points NPS/FWS—2010

increase in oceanic CO2 has resulted in 

a 30% increase in acidity (a decrease in 

surface ocean pH by an average of 0.1 

units), with observed and potential severe 

negative consequences for marine organisms and coral reef formations (Orr et al. 

2005: McNeil and Matear 2007; Riebesell 

et al. 2009).

•	 Oceans are noisier due to ocean acidification reducing the ability of seawater 

to absorb low frequency sounds (noise 

from ship traffic and military activities). 

Low-frequency sound absorption has decreased over 10% in both the Pacific and 

Atlantic over the past 200 years. An assumed additional pH drop of 0.3 (due 

to anthropogenic CO2 emissions) accompanied with warming will lead to sound 

absorption below 1 kHz being reduced by 

almost half of current values (Hester et. al. 

2008).

•	 Even if greenhouse gas concentrations are 

stabilized at current levels thermal expansion of ocean waters (and resulting sea 

level rise) will continue for many centuries, 

due to the time required to transport heat 

into the deep ocean.

•	 Observations since 1961 show that the 

average global ocean temperature has increased to depths of at least 3000 meters, 

and that the ocean has been taking up 

over 80% of the heat added to the climate 

system.

•	 Hydrologic effects of climate change include increased runoff and earlier spring 

peak discharge in many glacier- and snowfed rivers, and warming of lakes and rivers. 

•	 Runoff is projected to increase by 10 to 

40% by mid-century at higher latitudes 

and in some wet tropical areas, and to decrease by 10 to 30% over some dry regions 

at mid-latitudes and dry tropics. Areas in 

which runoff is projected to decline face a 

reduction in the value of the services provided by water resources. 

•	 Precipitation increased significantly from 

1900 to 2005 in eastern parts of North 

and South America, northern Europe, and 

northern and central Asia. Conversely, 

precipitation declined in the Sahel, the 

Mediterranean, southern Africa, and parts 

of southern Asia (Figure 5).

What scientists think is likely....

•	 Widespread mass losses from glaciers and 

reductions in snow cover are projected 

to accelerate throughout the 21st century, 

reducing water availability and changing 

seasonality of flow patterns.

•	 Model projections include contraction of 

snow cover area, widespread increases 

in depth to frost in permafrost areas, and 

Arctic and Antarctic sea ice shrinkage.

•	 The incidence of extreme high sea level 

has likely increased at a broad range of 

sites worldwide since 1975. 

•	 Based on current model simulations it is 

very likely that the meridional overturning 

circulation (MOC) of the Atlantic Ocean 

will slow down during the 21st century; 

nevertheless regional temperatures are 

predicted to increase. Large-scale and 

persistent changes in the MOC may result 

in changes in marine ecosystem producFigure 5. Relative changes in 

precipitation (in percent) for 

the period 2090-2099, relative 

to 1980-1999. Values are multimodel averages based on the 

SRES A1B scenario for December 

to February (left) and June to 

August (right). White areas are 

where less than 66% of the 

models agree in the sign of the 

change and stippled areas are 

where more than 90% of the 

models agree in the sign of the 

change (IPCC 2007a).

December to February June to August
National Park Service 23

tivity, fisheries, ocean CO2 uptake, and 

terrestrial vegetation.

•	 Globally the area affected by drought has 

likely increased since the 1970s and the 

frequency of extreme precipitation events 

has increased over most areas.

•	 Future tropical cyclones (typhoons and 

hurricanes) are likely to become more 

intense, with larger peak wind speeds and 

increased heavy precipitation. Extra-tropical storm tracks are projected to move 

poleward, with consequent shifts in wind, 

precipitation, and temperature patterns.

•	 Increases in the amount of precipitation 

are very likely in high latitudes and decreases are likely in most subtropical land 

regions, continuing observed patterns 

(Figure 5).

•	 Increases in the frequency of heavy precipitation events in the coming century are 

very likely, resulting in potential damage 

to crops and property, soil erosion, surface and groundwater contamination, and 

increased risk of human death and injury.

What scientists think is possible...

•	 Arctic late-summer sea ice may disappear 

almost entirely by the end of the 21st century (Figure 3).

•	 Current global model studies project that 

the Antarctic ice sheet will remain too cold 

for widespread surface melting and gain 

mass due to increased snowfall. However, 

net loss of ice mass could occur if dynamical ice discharge dominates the ice sheet 

mass balance.

•	 Model-based projections of global average sea level rise at the end of the 21st 

century range from 0.18 to 0.59 meters, 

depending on specific emissions scenarios 

(Table 2). These projections may actually 

underestimate future sea level rise because 

they do not include potential feedbacks or 

full effects of changes in ice sheet flow. 

•	 Partial loss of ice sheets and/or the thermal 

expansion of seawater over very long time 

scales could result in meters of sea level 

rise, major changes in coastlines and inundation of low-lying areas, with greatest 

effects in river deltas and low-lying islands.

C. Vegetation and Wildlife

What scientists know...

•	 Temperature increases have affected Arctic and Antarctic ecosystems and predator 

species at high levels of the food web.

•	 Changes in water temperature, salinity, 

oxygen levels, circulation, and ice cover 

in marine and freshwater ecosystems have 

resulted in shifts in ranges and changes 

in algal, plankton, and fish abundance in 

high-latitude oceans; increases in algal and 

zooplankton abundance in high-latitude 

and high-altitude lakes; and range shifts 

and earlier fish migrations in rivers. 

•	 High-latitude (cooler) ocean waters are 

currently acidified enough to start dissolving pteropods; open water marine snails 

Table 2. Projected global average sea level rise at the end of 

the 21st century, adapted from 

IPCC 2007b.

Notes: a) Temperatures are assessed best estimates and likely 

uncertainty ranges from a hierarchy of models of varying complexity as well as observational 

constraints.

Emissions Scenario

Sea level rise 

(m at 2090 – 2099 relative to 1980 – 1999)

Model-based range (excluding future rapid 

dynamical changes in ice flow)

Constant Year 2000 

Concentrationsa 0.3 – 0.9

B1 Scenario 1.1 – 2.9

B2 Scenario 1.4 – 3.8

A1B Scenario 1.7 – 4.4

A2 Scenario 2.0 – 5.4

A1F1 Scenario 2.4 – 6.4
24 Climate Change Talking Points NPS/FWS—2010

which are one of the primary food sources 

of young salmon and mackerel (Fabry et al. 

2008, Feely et al. 2008). In lower latitude 

(warmer) waters, by the end of this century Humboldt squid’s metabolic rate will 

be reduced by 31% and activity levels by 

45% due to reduced pH, leading to squid 

retreating at night to shallower waters to 

feed and replenish oxygen levels (Rosa 

and Seibel 2008). 

•	 A meta-analysis of climate change effects 

on range boundaries in Northern Hemisphere species of birds, butterflies, and 

alpine herbs shows an average shift of 6.1 

kilometers per decade northward (or 6.1 

meters per decade upward), and a mean 

shift toward earlier onset of spring events 

(frog breeding, bird nesting, first flowering, 

tree budburst, and arrival of migrant butterflies and birds) of 2.3 days per decade 

(Parmesan and Yohe 2003).

•	 Poleward range shifts of individual species 

and expansions of warm-adapted communities have been documented on all continents and in most of the major oceans of 

the world (Parmesan 2006).

•	 Satellite observations since 1980 indicate 

a trend in many regions toward earlier 

greening of vegetation in the spring linked 

to longer thermal growing seasons resulting from recent warming.

•	 Over the past 50 years humans have 

changed ecosystems more rapidly and extensively than in any previous period of 

human history, primarily as the result of 

growing demands for food, fresh water, 

timber, fiber, and fuel. This has resulted in 

a substantial and largely irreversible loss of 

Earth’s biodiversity 

•	 Although the relationships have not been 

quantified, it is known that loss of intact ecosystems results in a reduction in 

ecosystem services (clean water, carbon 

sequestration, waste decomposition, crop 

pollination, etc.).

What scientists think is likely...

•	 The resilience of many ecosystems is likely 

to be exceeded this century by an unprecedented combination of climate change, 

associated disturbance (flooding, drought, 

wildfire, insects, ocean acidification) and 

other global change drivers (land use 

change, pollution, habitat fragmentation, 

invasive species, resource over-exploitation) (Figure 6). 

•	 Exceedance of ecosystem resilience may 

be characterized by threshold-type responses such as extinctions, disruption of 

ecological interactions, and major changes 

in ecosystem structure and disturbance 

regimes.

•	 Net carbon uptake by terrestrial ecosystems is likely to peak before mid-century 

and then weaken or reverse, amplifying 

climate changes. By 2100 the terrestrial 

biosphere is likely to become a carbon 

source.

•	 Increases in global average temperature 

above 1.5 to 2.5°C and concurrent atmospheric CO2 concentrations are projected 

to result in major changes in ecosystem 

structure and function, species’ ecological interactions, and species’ geographical 

ranges. Negative consequences are projected for species biodiversity and ecosystem goods and services.

•	 Model projections for increased atmospheric CO2 concentration and global 

temperatures significantly exceed values 

for at least the past 420,000 years, the 

period during which more extant marine 

organisms evolved. Under expected 21st

century conditions it is likely that global 

warming and ocean acidification will compromise carbonate accretion, resulting in 

less diverse reef communities and failure 

of some existing carbonate reef structures. 

Climate changes will likely exacerbate local stresses from declining water quality and overexploitation of key species 

(Hoegh-Guldberg et al. 2007).

•	 Ecosystems likely to be significantly impacted by changing climatic conditions 

include:

i. Terrestrial – tundra, boreal forest, and 

mountain regions (sensitivity to warming); Mediterranean-type ecosystems 

and tropical rainforests (decreased 

rainfall)
National Park Service 25

Figure 6. Examples of impacts associated with projected global average surface warming. Upper panel: Illustrative examples of global 

impacts projected for climate changes (and sea level and atmospheric CO2 where relevant) associated with different amounts of increase 

in global average surface temperature in the 21st century. The black lines link impacts; broken-line arrows indicate impacts continuing with 

increasing temperature. Entries are placed so that the left-hand side of text indicates the approximate level of warming that is associated 

with the onset of a given impact. Quantitative entries for water scarcity and flooding represent the additional impacts of climate change 

relative to the conditions projected across the range of SRES scenarios A1FI, A2, B1 and B2. Adaptation to climate change is not included 

in these estimations. Confidence levels for all statements are high. Lower panel: Dots and bars indicate the best estimate and likely ranges 

of warming assessed for the six SRES marker scenarios for 2090-2099 relative to 1980-1999 (IPCC 2007a).
26 Climate Change Talking Points NPS/FWS—2010

ii. Coastal – mangroves and salt marshes 

(multiple stresses) 

iii. Marine – coral reefs (multiple stresses); 

sea-ice biomes (sensitivity to warming)

What scientists think is possible...

•	 Approximately 20% to 30% of plant and 

animal species assessed to date are at increased risk of extinction with increases in 

global average temperature in excess of 1.5 

to 2.5°C.

•	 Endemic species may be more vulnerable 

to climate changes, and therefore at higher 

risk for extinction, because they may have 

evolved in locations where paleo-climatic 

conditions have been stable.

•	 Although there is great uncertainty about 

how forests will respond to changing 

climate and increasing levels of atmospheric CO2, the factors that are most 

typically predicted to influence forests 

are increased fire, increased drought, and 

greater vulnerability to insects and disease 

(Brown 2008).

•	 If atmospheric CO2 levels reach 450 ppm 

(projected to occur by 2030–2040 at the 

current emissions rates), reefs may experience rapid and terminal decline worldwide from multiple climate change-related 

direct and indirect effects including mass 

bleaching, ocean acidification, damage to 

shallow reef communities,reduction of 

biodiversity, and extinctions. (Veron et al. 

2009). At atmospheric CO2 levels of 560 

ppmv, calcification of tropical corals is expected to decline by 30%, and loss of coral 

structure in areas of high erosion may 

outpace coral growth. With unabated CO2

emissions, 70% of the presently known 

reef locations (including cold-water corals) will be in corrosive waters by the end 

of this century (Riebesell, et al. 2009).

D. Disturbance

What scientists know...

•	 Climate change currently contributes to 

the global burden of disease and premature death through exposure to extreme 

events and changes in water and air quality, food quality and quantity, ecosystems, 

agriculture, and economy (Parry et al. 

2007).

•	 The most vulnerable industries, settlements, and societies are generally those 

in coastal and river flood plains, those 

whose economies are closely linked with 

climate-sensitive resources, and those in 

areas prone to extreme weather events. 

•	 By 2080-2090 millions more people than 

today are projected to experience flooding 

due to sea level rise, especially those in the 

low-lying megadeltas of Asia and Africa 

and on small islands.

•	 Climate change affects the function and 

operation of existing water infrastructure 

and water management practices, aggravating the impacts of population growth, 

changing economic activity, land-use 

change, and urbanization.

What scientists think is likely...

•	 Up to 20% of the world’s population will 

live in areas where river flood potential 

could increase by 2080-2090, with major 

consequences for human health, physical 

infrastructure, water quality, and resource 

availability.

•	 The health status of millions of people is 

projected to be affected by climate change, 

through increases in malnutrition; increased deaths, disease, and injury due to 

extreme weather events; increased burden 

of diarrheal diseases; increased cardiorespiratory disease due to higher concentrations of ground-level ozone in urban 

areas; and altered spatial distribution of 

vector-borne diseases.

•	 Risk of hunger is projected to increase at 

lower latitudes, especially in seasonally 

dry and tropical regions.

What scientists think is possible...

•	 Although many diseases are projected to 

increase in scope and incidence as the 

result of climate changes, lack of appropriate longitudinal data on climate changerelated health impacts precludes definitive 

assessment.
National Park Service 27

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