Press Release: New Study Shows Higher Rate of Warming and Sea Level Rise Than Previously Expected

For Immediate Release:
June 29, 1999

Contact: Kelly Sullivan/Heather Fass

New Study Shows Higher Rate of Warming and Sea Level Rise Than Previously Expected: U.S. Temperature Rise Expected to be Greater Than Global Average

WASHINGTON, D.C. — A new report released by the Pew Center on Global Climate Change reveals slightly higher rates of warming and sea level rise than predicted in 1995 by an international group of scientists on the Intergovernmental Panel on Climate Change (IPCC). The new estimates are based on preliminary versions of four new emissions scenarios identified by the IPCC Special Report on Emissions Scenarios (SRES).

The projected changes are 1.3 - 4.0°C (2.3 - 7.2°F) for global-mean temperature (previous IPCC projections were 0.8 - 3.5°C; 1.4 - 6.3°F), and 17 to 99 cm. (7 to 39 in.) for sea level rise by 2100 (versus 13 to 94 cm.; 5 to 37 in. from the IPCC). These high projected increases in temperature and sea level rise are due to lower levels of sulfur dioxide emissions than previous projections (efforts to reduce sulfur dioxide - another pollutant - could result in increased warming since sulfate particles cool the atmosphere).

For temperature, these values mean that future changes in global-mean temperatures will be 2 to 7 times more rapid than those of the 20th century and that rises in sea level will occur at rates 1 to 7 times those of the 20th century.

"As policymakers, industry and the public tackle the challenges of climate change, understanding the seriousness and complexity of the issue is critical to crafting the most effective responses," said Eileen Claussen, Executive Director, Pew Center on Global Climate Change. "The data and likely impacts outlined in this study should encourage concrete steps to reduce greenhouse gas emissions."

The study, "The Science of Climate Change: Global and U.S. Perspectives," was conducted and written by Tom M.L. Wigley of the National Center for Atmospheric Research for the Pew Center on Global Climate Change.

Based on results from a number of climate models, the rate of future warming for the United States is expected to be noticeably faster than the global-mean rate. While the Southeast and Southwest tend to show warming slightly below the global-mean, the northernmost states from North Dakota eastward to Maine show enhanced warming by a factor of up to two during the winter months. Future regional-scale precipitation changes are highly uncertain. The only result that is common to all climate models is an increase in winter precipitation in northern latitudes, from the northern Great Plains to the northeastern states.

The study also found that changes in climate extremes were likely.

  • Warm temperature extremes will almost certainly become more frequent;
  • Cold temperature extremes will almost certainly become less frequent;
  • The frequency of high precipitation events is likely to increase;
  • It is likely that rainfall amounts associated with hurricanes will increase; and
  • An increase in the frequency and intensity of hurricanes in the North Atlantic region is possible.

F or all extreme events, however, it is unlikely that the projected changes will become evident in a statistically convincing way for many decades, with the exception of temperature extremes, which should become evident sooner.

This most recent research also strengthens the IPCC statement that "the balance of evidence suggests a discernible human influence on global climate." First, climate model estimates of global-mean temperature changes over the 20th Century, and of the patterns of temperature change, are consistent with observations. Second, the effects of solar changes on the climate have been better quantified. They show that the sun can only account for about one-third of the observed global-mean warming. Third, scientists are beginning to understand why recent trends in the temperature of the lower to mid-troposphere derived from satellite data differ from those at the surface.

"This research provides valuable information that should move the climate change debate beyond questions about the science and towards realistic solutions," said Claussen.

The findings in the study will be highlighted in a print advertisement supported by the Pew Center, which is scheduled to appear in The New York Times, The Washington Post, National Journal, Roll Call and Newsweek.

The Pew Center was established in May 1998 by the Pew Charitable Trusts, one of the nation's largest philanthropies and an influential voice in efforts to improve the quality of America's environment. The Pew Center is conducting studies, launching public education efforts, promoting climate change solutions globally and working with businesses to develop marketplace solutions to reduce greenhouse gases. The Pew Center is led by Eileen Claussen the former U.S. Assistant Secretary of State for Oceans and International Environmental and Scientific Affairs.

The Pew Center includes the Business Environmental Leadership Council, which is composed of 21 major, largely Fortune 500 corporations all working with the Pew Center to address issues related to climate change. The companies do not contribute financially to the Pew Center - it is solely supported by contributions from charitable foundations.

Agriculture & Global Climate Change: A Review of Impacts to U.S. Agricultural Resources

Agriculture & Global Climate Change: A Review of Impacts to U.S. Agricultural Resources

Prepared for the Pew Center on Global Climate Change
February 1999

Richard M. Adams, Oregon State University
Brian H. Hurd, Stratus Consulting Inc.
John Reilly, Massachusetts Institute of Technology

Press Release

Download Entire Report (pdf)


Eileen Claussen, Executive Director, Pew Center on Global Climate Change

In order to intelligently respond to climate change, we must first understand the likely consequences on our environment and health. This report, the first in a series of environmental impact reports, will explore anticipated effects of climate change on U.S. agriculture. Other reports in this series will assess what is known about the impact of climate change on weather and include analyses of its impact on water resources, coastal areas, human health, ecosystems, and forests. In evaluating the current state of scientific knowledge regarding the anticipated effects of climate change on U.S. agriculture, this report yields several key observations:

Climate change will result in agricultural shifts and changes across the United States. Given the requisite time and resources to adapt, the United States is likely to continue to be able to feed itself; however, there will clearly be regional winners and losers.

If the rate of greenhouse gas emissions exceeds projected levels or if unanticipated or more frequent extreme events accompany this change, the outlook for the United States would likely worsen. The projections in this report, for example, are based on a doubling of carbon dioxide (CO2) in the atmosphere which could understate the severity of climate change impacts over the long-term.

Some countries will experience more negative effects on agriculture associated with climate change. The situation will be particularly acute in developing nations that do not have the same resources as the United States to respond to the agricultural changes projected.

This report broadly outlines projected effects on U.S. agricultural regions. The complexity of the climate system itself and its relationship to agricultural resources make it difficult to project specific effects on individual states or communities. More research is needed to better understand this complex system and to incorporate relevant factors into future climate models and assessments. The report does, however, provide an objective foundation upon which to build and clearly demonstrates the impact climate change will have, both direct and indirect, on U.S. agricultural systems.

In addition to reporting on the environmental impacts of climate change, the Pew Center undertakes analyses on domestic and international policy matters and economics. The Center was established in 1998 by the Pew Charitable Trusts to bring a new, cooperative approach and critical scientific, economic and technological expertise to the global climate change debate.

A number of major corporations have taken a bold and historic step in joining the Center's Business Environmental Leadership Council. In doing so, they have accepted "the views of most scientists that enough is known about the science and environmental impacts of climate change for us to take actions to address its consequences." Understanding the potential environmental impacts of climate change, as this report illustrates, is an important step toward promoting informed action.

Executive Summary

This paper analyzes the current state of knowledge about the effects of climate change on U.S. food production and agricultural resources. The paper also considers regional changes in agricultural production, including distributional impacts.

The linkages between agriculture and climate are pronounced, often complex, and not always well understood. Temperature increases can have both positive and negative effects on crop yields, with the difference depending in part on location and on the magnitude of the increase. Crop yields in the northern United States and Canada may increase, but yields in the already warm, low-latitude regions of the southern United States are likely to decline. Evidence also suggests positive crop yield effects for mild to moderate temperature increases such as 2°C to 3°C (3.6°F to 5.4°F). However, once average global temperatures rise beyond about 4°C (7.2°F), yields begin to fall. Increases in precipitation level, timing, and variability may benefit semi-arid and other water-short areas by increasing soil moisture, but could aggravate problems in regions with excess water. Although most climate models predict precipitation increases, some regions will experience decreased precipitation, which could exacerbate water shortages and droughts. Higher carbon dioxide (CO2) levels in controlled experiments increase crop growth and decrease water use. However, these experiments often have demonstrated a more positive response than observed under actual field conditions.

Agricultural systems are most sensitive to extreme climatic events such as floods, wind storms, and droughts, and to seasonal variability such as periods of frost, cold temperatures, and changing rainfall patterns. Climate change could alter the frequency and magnitude of extreme events and could change seasonal patterns in both favorable and unfavorable ways, depending on regional conditions. Increases in rainfall intensity pose a threat to agriculture and the environment because heavy rainfall is primarily responsible for soil erosion, leaching of agricultural chemicals, and run off that carries livestock waste and nutrients into water bodies. Currently available climate forecasts cannot resolve how extreme events and variability will change; however, both are potential risks to agriculture. The rate of change is also uncertain. Adjustment costs are likely to be higher with greater rates of change.

Agricultural systems are managed. Farmers have a number of adaptation options open to them, such as changing planting and harvest dates, rotating crops, selecting crops and crop varieties for cultivation, consuming water for irrigation, using fertilizers, and choosing tillage practices. These adaptation strategies can lessen potential yield losses from climate change and improve yields in regions where climate change has beneficial effects. At the market level, price and other changes can signal further opportunities to adapt as farmers make decisions about land use and which crops to grow. Thus, patterns of food production respond not only to biophysical changes in crop and livestock productivity brought about by climate change or technological change, but also to changes in agricultural management practices, crop and livestock prices, the cost and availability of inputs, and government policies. In the longer term, adaptations include the development and use of new crop varieties that offer advantages under changed climates, or investments in new irrigation infrastructure as insurance against potentially less reliable rainfall. The extent to which opportunities for adaptation are realized depends upon a variety of factors such as information flow, access to capital, and the flexibility of government programs and policies.

Climate change can also have a number of negative indirect effects on agro-environmental systems effects that have been largely ignored in climate change assessments. These indirect effects include changes in the incidence and distribution of pests and pathogens, increased rates of soil erosion and degradation, and increased tropospheric ozone levels from rising temperatures. Regional shifts in crop production and expansion of irrigated acreage may stress environmental and natural resources, including water quantity and quality, wetlands, soil, fish, and wildlife.

The focus of this paper is on the impacts of climate change on agriculture. However, agriculture is also a potential source of greenhouse gas (GHG) emissions, and it can play an important role in mitigating these emissions. Methane from rice paddies and livestock, nitrous oxide (N2O) from cultivated soils and feedlots, and CO2 from the cultivation of virgin agricultural lands and intensive production methods contribute to global warming. Changes in management can reduce emissions from these sources. Agriculture can reduce atmospheric CO2 through tree-planting and similar programs that sequester significant amounts of carbon and through increased planting of biofuel crops that could replace fossil fuels.

The following describes the current understanding regarding the potential impacts of climate change on U.S. agriculture:

CROPS AND LIVESTOCK ARE SENSITIVE TO CLIMATE CHANGES IN BOTH POSITIVE AND NEGATIVE WAYS. Understanding the direct biophysical and economic responses to these changes is complicated and requires more research. In addition, indirect effects - such as changes in pests and water quality and changes in extreme climate events - are not well understood.


THE IMPACT OF CLIMATE CHANGE ON U.S. AGRICULTURE IS MIXED. Climate change is not expected to threaten the ability of the United States to produce enough food to feed itself through the next century; however, regional patterns of production are likely to change. Regions such as the Northern Great Plains and Great Lakes may have increased productivity while the Southern Plains, Delta states, and possibly the Southeast and portions of the Corn Belt could see agricultural productivity fall. However, the form and pattern of change are uncertain because changes in regional climate cannot be predicted with a high degree of confidence.

CONSIDERATION OF ADAPTATION AND HUMAN RESPONSE IS CRITICAL TO THE ACCURATE AND CREDIBLE ASSESSMENT OF CLIMATE CHANGE IMPACTS.However, because of the long time horizons involved in climate change assessments and uncertainties concerning the rate at which climate will change, it is difficult to predict accurately what adaptations people will make. This is particularly challenging since adaptations are influenced by many factors, including government policy, prices, technology research and development, and agricultural extension services.

BETTER CLIMATE CHANGE FORECASTS ARE KEY TO IMPROVE DASSESSMENTS OF THE IMPACTS OF CLIMATE CHANGE. In the meantime, farmers and the agricultural community must consider strategies that are economically and environmentally viable in the face of uncertainty about the course of climate change.

AGRICULTURE IS A SECTOR THAT CAN ADAPT, BUT THERE ARE SOME FACTORS NOT INCLUDED IN ASSESSMENTS THAT COULD CHANGE THIS CONCLUSION.Changes in the incidence and severity of agricultural pests, diseases, soil erosion, and tropospheric ozone levels, as well as changes in extreme events such as droughts and floods, are largely unmeasured or uncertain and have not been incorporated into estimates of impacts. These omitted effects could result in a very different assessment of the true impacts of climate change on agriculture. If the rate or magnitude of climate change is much greater than anticipated, adaptation could be more difficult and impacts could be greater than currently expected.
Overall, the consensus of economic assessments is that global climate change of the magnitudes currently being discussed by the Intergovernmental Panel on Climate Change (IPCC) and other organizations (i.e., +0.8°C to +4.5°C or +1.4°F to +8.1°F) could result in some lowering of global production but will have only a small overall effect on U.S. agriculture and its ability to provide sufficient food and fiber to both domestic and global customers over the next 100 years. However, distributional effects within the United States can be significant because consumers, producers, and local economies will gain in some regions and lose in others.

Warming beyond that reflected in current studies (i.e., associated with a continued rise in CO2 beyond the doubling that has been commonly investigated) is expected to impose greater costs, decreasing agricultural production in most areas of the United States and substantially limiting global production. This reinforces the need to determine the magnitude and rate of warming that may accompany the CO2 and greenhouse gas build-up currently underway in the atmosphere.

About the Authors

Richard M. Adams
Oregon State University, Corvallis, OR

Richard M. Adams received his Ph.D. in Agricultural Economics from the University of California, Davis, in 1975. He is currently a professor of Agricultural and Resource Economics at Oregon State University, a position he has held since 1983. His research interests include the economic analysis of resource and environmental issues, with emphasis on the consequences of environmental change. Professor Adams has served on numerous governmental advisory and research committees dealing with environmental issues. He has published over 160 journal articles, book chapters and research reports, including 20 on the effects of climate change on agriculture and agricultural resources. He has served on the editorial boards of five journals and w as editor of the American Journal of Agricultural Economics from 1992 to 1994.

Brian H. Hurd
Stratus Consulting Inc., Boulder, CO

Brian H. Hurd is a Senior Associate in the climate change group at Stratus Consulting, a Boulder-based environment and energy research firm. He received his Ph.D. in agricultural economics from the University of California, Davis in 1992, where he analyzed technology changes in production agriculture. His passion for interdisciplinary research and for contributing to public decision-making regarding natural resources has led to his current focus on climate change. He has developed regional and national models of water resource impacts, analyzed land use changes in forestry and agriculture, and investigated adaptation and mitigation strategies, while serving a variety of public- and private-sector clients such as U.S. EPA, U.S. Department of Energy, National Science Foundation, National Institute for Global Environmental Change, and the Electric Power Research Institute.

John Reilly
Massachusetts Institute of Technology, Cambridge, MA

Dr. Reilly is the Associate Director for Research in the Joint Program on the Science and Policy of Global Change at the Massachusetts Institute of Technology. He spent 12 years with the Economic Research Service of USDA, most recently as the Acting Director and Deputy Director for Research of the Resource Economics Division. He has been a scientist with Battelle's Pacific Northwest National Laboratory and with the Institute for Energy Analysis, Oak Ridge Associated Universities. He received his Ph.D. in economics from the University of Pennsylvania in 1983 and holds a BS in economics and political science from the University of Wisconsin. He has conducted research on the economics of climate change for 19 years. He was a principal author for the Intergovernmental Panel on Climate Change's Second Assessment Report and has served on many Federal government and international committees on climate change and agricultural research.



Brian Hurd
John M. Reilly
Richard M. Adams

Press Release: New Study Details Effects of Climate Change On U.S. Agriculture

For Immediate Release:
February 10, 1999

Contact: Shannon Hunt / Kelly Sullivan
             (202) 289-5900

New Study Details Effects of Climate Change On U.S. Agriculture

Projected Regional Impacts on Agriculture Outlined: New Report is First in Series Examining Environmental Impacts of Climate Change

WASHINGTON, D.C. — Climate change has the potential to affect livestock and crops, local agricultural economies and crop production trends according to a new report by the Pew Center on Global Climate Change, which examines the effects of climate change on agriculture. The report finds that while climate change is not expected to threaten the ability of the U.S. to produce enough food to feed itself through the next century, some U.S. agricultural regions, particularly in the north, are expected to benefit, while others, primarily in the south, could face adverse impacts.

The report, released today at a press conference on Capitol Hill, notes that the resiliency and adaptability of the U.S. agricultural sector has made it one of the country's most productive industries and gives the sector the ability to adapt to the changes associated with climate change. However, the report also finds that there remains a potential for negative effects, and particular regions, especially those in the south, will face greater obstacles in adapting to the challenges posed by climate change.

"Anyone with a stake in agriculture should be interested in the findings of this report, which shows that the farming industry we know today will not be the same in the future under the effects of climate change," said Eileen Claussen, Pew Center Executive Director.

At Wednesday's press conference, Agriculture Committee Chairman Richard Lugar (R-IN) and Senator Bob Kerrey (D-NE) both issued statements supporting the Pew Center's efforts to inform American agricultural producers about the potential impacts of climate change.

According to the report, climate change could cause grain yields to fall significantly in southern states, while in the north, longer growing seasons could increase yields of grains such as wheat. Changes in grain production and foraging regions could also cause shifts in the locations of livestock production. Uncertainty in the models does not allow precision in identifying localized effects.

The study finds that in order to develop the most accurate and credible assessment of the possible impacts of climate change, it is important to consider adaptation and human response, as well as to continue to develop improved climate change forecasts. But, given the potential impacts, farmers and the agricultural community must consider new strategies in the face of uncertainty.

The report states that the emerging consensus from modeling studies is that the net effects on U.S. agriculture, with a doubling of carbon dioxide in the atmosphere, may be small. But, these models may understate long-range impacts if the rate or magnitude of greenhouse gas emissions exceed projected levels. For example, extreme events - such as storms, droughts and early and late frosts caused by climate change - also could play a role in determining the ultimate impact of climate change on agriculture.

Additionally, secondary impacts of climate change, such as the potential for higher ozone levels, impacts on water resources and pest populations, contribute to the uncertainty and pose additional challenges not only to individual producers, but also larger agricultural economies.

The value of U.S. agricultural commodities exceeds $165 billion at the farm level and over $500 billion after processing and marketing. "The role of the U.S. agricultural sector is too important for us to ignore these findings," said Claussen. "The agricultural community can adapt to climate change, but adaptation takes time and resources, and with uncertainties related to the timing and magnitude of temperature changes, not all opportunities for adaptation are likely to be realized."

This report is the first in a series of environmental impact reports slated to be released by the Pew Center this year. Other reports in this series will assess what is known about the impact of climate change on weather and includes analyses of its impact on water resources, coastal areas, human health, ecosystems, and forests.

A copy of the report, "A Review of Impacts to U.S. Agricultural Resources," is available on the Pew Center web site at

The Pew Center was established in May 1998 by the Pew Charitable Trusts, one of the nation's largest philanthropies and an influential voice in efforts to improve the quality of America's environment. The Pew Center is conducting studies, launching public education efforts, promoting climate change solutions globally and working with businesses to develop marketplace solutions to reduce greenhouse gases. The Pew Center is led by Eileen Claussen the former U.S. Assistant Secretary of State for Oceans and International Environmental and Scientific Affairs.

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