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Global climate change impacts in the United States

18 June 2009

Climate change is already having visible impacts in the United States, and the choices made now will determine the severity of its impacts in the future, according to a new and authoritative federal study assessing the current and anticipated domestic impacts of climate change.

The report, ‘Global Climate Change Impacts in the United States,’ compiles years of scientific research and takes into account new data not available during the preparation of previous large national and global assessments. It was produced by a consortium of experts from 13 U.S. government science agencies and from several major universities and research institutes. With its production and review spanning Republican and Democratic administrations, it offers a valuable, objective scientific consensus on how climate change is affecting—and may further affect—the United States.

“This new report integrates the most up-to-date scientific findings into a comprehensive picture of the ongoing as well as expected future impacts of heat-trapping pollution on the climate experienced by Americans, region by region and sector by sector,” said John P. Holdren, Assistant to the President for Science and Technology and director of the White House Office of Science and Technology Policy. “It tells us why remedial action is needed sooner rather than later, as well as showing why that action must include both global emissions reductions to reduce the extent of climate change and local adaptation measures to reduce the damage from the changes that are no longer avoidable.”

The report, which confirms previous evidence that global temperature increases in recent decades have been primarily human-induced, incorporates the latest information on rising temperatures and sea levels; increases in extreme weather events; and other climate-related phenomena.

“This report stresses that climate change has immediate and local impacts – it literally affects people in their backyards,” said Jane Lubchenco, under secretary of commerce for oceans and atmosphere and administrator of the National Oceanic and Atmospheric Administration. “In keeping with our goals, the information in it is accessible and useful to everyone from city planners and national legislators to citizens who want to better understand what climate change means to them. This is an issue that clearly affects everyone.”

A product of the interagency U.S. Global Change Research Program, the definitive 190-page report, produced under NOAA’s leadership, is written in plain language to better inform members of the public and policymakers. Commissioned in 2007 and completed this spring, the science-based report is a consensus product spanning two Presidential administrations and transcends political leanings or biases. It underwent intensive review by scientists inside and outside of government and includes information more recent than that incorporated into the last major report on global climate change released by the Intergovernmental Panel on Climate Change.

The report is not intended to direct policy makers to take any one approach over another to mitigate climate change or adapt to it. But it emphasizes that the choices we make now will determine the severity of climate change impacts in the future. Implementing sizable and sustained reductions in carbon dioxide emissions as soon as possible would significantly reduce the pace and the overall amount of climate change,” the report states, “and would be more effective than reductions of the same size initiated later.”

The study finds that Americans are already being affected by climate change through extreme weather, drought and wildfire trends and details how the nation’s transportation, agriculture, health, water and energy sectors will be affected in the future. The study also finds that the current trend in the emission of greenhouse gas pollution is significantly above the worst-case scenario that this and other reports have considered.

Among the key findings are:

1. Global warming is unequivocal and primarily human-induced.

2. Climate changes are underway in the United States and are projected to grow.

3. Widespread climate-related impacts are occurring now and are expected to increase.

4. Climate change will stress water resources.

5. Crop and livestock production will be increasingly challenged

6. Coastal areas are at increasing risk from sea-level rise and storm surge.

7. Threats to human health will increase.

8. Climate change will interact with many social and environmental stresses.

9.Thresholds will be crossed, leading to large changes in climate and ecosystems.

10. Future climate change and its impacts depend on choices made today.

Key findings, regional factsheets and the full report are available online from the Global Change Research Program.