Potential Impacts of Climate Change in the United States
May 2009
The cover image was provided courtesy of the National Aeronautics and Space Administration’s Visible Earth team.
Preface
Human activities are yielding rising atmospheric concentrations of greenhouse gases and other gases and particulates and are also greatly altering the Earth’s land cover. A scientific consensus has emerged that those activities, if allowed to continue unabated, will have extensive, highly uncertain, but potentially serious and costly impacts on regional climates and ocean conditions throughout the world.
This Congressional Budget Office (CBO) paper—prepared at the request of the Chairman of the Senate Committee on Energy and Natural Resources—presents an overview of the current understanding of the impacts of climate change in the United States, emphasizing the wide range of uncertainty about the magnitude and timing of those impacts and the implications of that uncertainty for the formulation of effective policy responses. The analysis draws from numerous published sources to summarize the current state of climate science and provide a conceptual framework for addressing climate change as an economic concern. In keeping with CBO’s mandate to provide objective, impartial analysis, the paper makes no recommendations.
Robert Shackleton of CBO’s Macroeconomic Analysis Division wrote the paper under the general supervision of Robert Dennis, Douglas Hamilton (formerly of CBO), and William Randolph. CBO staff members James Baumgardner, Juan Contreras, Terry Dinan, Rob Johansson, Joseph Kile, David Torregrosa, Christopher Williams, and Thomas Woodward provided valuable comments and assistance, and Holly Battelle and Adam Weber provided research assistance.
Reviews were kindly provided by Henry Jacoby and John Reilly of the Joint Program on the Science and Policy of Global Change at the Massachusetts Institute of Technology; Anthony Janetos of the Joint Global Change Research Institute at the University of Maryland in College Park; Donald Kennedy of Leland Stanford University; and Roger Pielke, Sr., of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado in Boulder. As always, the assistance of external reviewers implies no responsibility for the final product, which rests solely with CBO.
Christine Bogusz edited the paper, and John Skeen proofread it. Maureen Costantino prepared the paper for publication and designed the cover. Linda Schimmel coordinated the print distribution, and Simone Thomas prepared the electronic versions for CBO’s Web site.
Contents
The Link Between Emissions and Climate
Potential Impacts of Climate Change
Effects on the Physical Environment
Consequences for Biological Systems
Impacts on the Economy and Human Health
Policy Implications of Uncertainty
1. Historical and Projected Climate Change
2. Illustration of Changes in Averages and Extremes in Temperature and Precipitation
3. Historical Climate Patterns in the Continental United States, 1971 to 2000
4. Historical and Projected Climate Change, With and Without an IllustrativePolicy Applied
5. Uncertainty in the Climate’s Response to Rising Atmospheric Concentrations of Carbon Dioxide
