Date:  May 12, 2011






WASHINGTON — Warning that the risk of dangerous climate change impacts is growing with every ton of greenhouse gases emitted into the atmosphere, a National Research Council committee today reiterated the pressing need for substantial action to limit the magnitude of climate change and to prepare to adapt to its impacts.  The nation's options for responding to the risks posed by climate change are analyzed in a new report and the final volume in America's Climate Choices, a series of studies requested by Congress.  The committee that authored the report included not only renowned scientists and engineers but also economists, business leaders, an ex-governor, a former congressman, and other policy experts.


"The goal of the America's Climate Choices studies is to ensure that climate decisions are informed by the best possible scientific knowledge, analysis, and advice, both now and in the future," said committee chair Albert Carnesale, chancellor emeritus and professor, University of California, Los Angeles.


The new report reaffirms that the preponderance of scientific evidence points to human activities -- especially the release of carbon dioxide and other greenhouse gases into the atmosphere -- as the most likely cause for most of the global warming that has occurred over the last several decades.  This trend cannot be explained by natural factors such as internal climate variability or changes in incoming energy from the sun.  The report adds that the impacts of climate change on human and natural systems can generally be expected to intensify with warming.


While it recognized that climate change is inherently a global issue requiring an international response, the committee focused on the charge from Congress to identify steps and strategies that U.S. decision makers could adopt now.  A coordinated national response to climate change, which the country currently lacks, is needed and should be guided by an iterative risk management framework in which actions taken can be revised as new knowledge is gained.


"America's response to climate change is ultimately about making choices in the face of risk," noted committee vice chair William L. Chameides, dean of the Nicholas School of the Environment, Duke University, Durham, N.C.  "Risk management strategies must be durable enough to promote sustained progress yet sufficiently flexible to take advantage of new knowledge and technologies."


Substantial reductions of greenhouse gas emissions should be among the highest priorities in the national response, the committee said.  Although the exact magnitude and speed of reductions will depend on how much risk society deems acceptable, it would be imprudent to delay taking action.  The committee cited many reasons for not waiting, including that the faster emissions are reduced, the lower the risks.  And because the effects of greenhouse gases can take decades to manifest and then persist for hundreds or even thousands of years, waiting for impacts to occur before taking action will likely be too late for meaningful mitigation.  Beginning emissions reductions soon will also lower the pressure to make steeper and costlier cuts later.  "It is our judgment that the most effective strategy is to begin ramping down emissions as soon as possible," Carnesale said.


State and local efforts currently under way or being initiated to reduce greenhouse gas emissions are potentially quite significant but unlikely to yield outcomes comparable to what could be achieved with a strong federal effort, according to the committee.  It said the most efficient way to accelerate emissions reductions is through a nationally uniform price on greenhouse gas emissions with a price trajectory sufficient to spur investments in energy efficiency and low-carbon technologies.  Having such policies in place is crucial to guide investments in energy infrastructure that will largely determine the direction of greenhouse gas emissions for decades to come.


The committee deemed the risks of sticking to "business as usual" to be a much greater concern than the risks associated with a strong response.  Most policy responses could be reversed if they prove to be more stringent than is needed, but adverse changes to the climate system are difficult or impossible to undo.  It also said that uncertainty in projecting the severity, location, or time of climate change impacts is not a reason for inaction.  On the contrary, uncertainty about future risks could be a compelling reason for taking action given that abrupt, unanticipated, or more severe impacts could occur.


Aggressive cuts in greenhouse gas emissions would reduce the need for adaptation but not eliminate it, the committee emphasized, urging the nation to mobilize now to reduce vulnerability to climate change impacts.  While adaptation planning largely occurs at the state and local level, the federal government should help coordinate these efforts and develop a national adaptation strategy.


In addition, the federal government should maintain an integrated portfolio of research programs aimed at increasing understanding of the causes and consequences of climate change and developing tools to limit climate change and adapt to its impacts.  The government also needs to take the lead in collecting and sharing climate change information to ensure that pertinent knowledge is used to inform decisions.  Public and private sector engagement through broad-based deliberative processes is essential as well.  These processes should include transparent analyses of climate change information, an explicit discussion of uncertainties, and consideration of how decisions will be affected by differing personal values.


Because emissions reductions in the U.S. alone will not be adequate to avert dangerous climate change risks, U.S. leadership needs to remain actively engaged in international climate change response efforts, the committee emphasized.  If the U.S. pursues strong emission reduction efforts, it will be better positioned to influence other countries to do the same.  Given that climate change impacts elsewhere in the world may affect U.S. interests, it would also be prudent to help enhance the adaptive capacity of other nations, particularly developing countries.


The new report builds upon the four previous America's Climate Choices panel reports:  Advancing the Science of Climate Change; Limiting the Magnitude of Future Climate Change; Adapting to the Impacts of Climate Change; and Informing an Effective Response to Climate Change.


The America's Climate Choices studies were sponsored by NOAA.  The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies.  They are independent, nonprofit institutions that provide science, technology, and health policy advice under an 1863 congressional charter.  Committee members, who serve pro bono as volunteers, are chosen by the Academies for each study based on their expertise and experience and must satisfy the Academies' conflict-of-interest standards.  The resulting consensus reports undergo external peer review before completion.  For more information, visit  A committee roster follows.



William Kearney, Director of Media Relations

Luwam Yeibio, Media Relations Assistant

Office of News and Public Information

202-334-2138; e-mail


Additional resources:

Report in Brief

Full Report

Project Website

Event Video

Copies of America's Climate Choices are available from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at  Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).


#       #       #


Division on Earth and Life Studies

Board on Atmospheric Sciences and Climate


Committee on America's Climate Choices


Albert Carnesale1 (chair)

Chancellor Emeritus and Professor

University of California

Los Angeles


William L. Chameides 2 (vice  chair)


Nicholas School of the Environment

Duke University

Durham, N.C.


Donald F. Boesch

Professor of Marine Science and President

University of Maryland Center for Environmental Science



Marilyn A. Brown

Professor of Energy Policy

School of Public Policy

Georgia Institute of Technology



Jonathan Cannon

Distinguished Professor of Environmental Law and Director

Environmental and Land Use Law Program

University of Virginia



Thomas Dietz

Assistant Vice President for Environmental Research, and 


Department of Sociology

Environmental Science and Policy Program

Michigan State University

East Lansing


George C. Eads

Senior Adviser

Charles Rivers Associates International

Washington, D.C.


Robert W. Fri

Visiting Scholar and Senior Fellow Emeritus

Resources for the Future

Washington, D.C.


James E. Geringer

Former Governor of Wyoming; and

Director of Policy and Public Sector Strategies

Environmental Systems Research Institute Inc.



Dennis L. Hartmann


Department of Atmospheric Sciences, and

Senior Fellow

Joint Institute for the Study of the Atmosphere and Ocean

University of Washington



Charles O. Holliday Jr.1

Chairman of the Board and Chief Executive Officer

E.I. du Pont de Nemours and Co. (retired)

Nashville, Tenn.


Diana M. Liverman


School of Geography and Environment

Environmental Change Institute

University of Oxford, and


Institute for Environment and Society

University of Arizona



Pamela A. Matson 2


School of Earth Sciences

Stanford University

Stanford, Calif.


Peter H. Raven 2

President Emeritus

Missouri Botanical Garden

St. Louis


Richard L. Schmalensee

Professor of Economics and Management

Sloan School of Management

Massachusetts Institute of Technology



Philip R. Sharp

Former  Congressman; and 


Resources for the Future

Washington, D.C.


Peggy M. Shepard

Executive Director

WE ACT for Environmental Justice

New York City


Robert H. Socolow

Professor of Mechanical and Aerospace Engineering

Environmental Institute

Princeton University

Princeton, N.J.


Susan Solomon 2

Senior Scientist

National Oceanic and Atmospheric Administration

Boulder, Colo. 


Bjorn Stigson


World Business Council for Sustainable Development



Thomas J. Wilbanks


Global Change and Developing Countries Program

Oak Ridge National Laboratory

Oak Ridge, Tenn. 


Peter Zandan

Senior Adviser

Public Strategies Inc.

Austin, Texas




Laurie Geller

Study Director


 1 Member, National Academy of Engineering

 2 Member, National Academy of Sciences