Andrew C. Revkin | Washington | May 28

NYT - The rise in concentrations of carbon dioxide in the atmosphere from human activities is influencing climate patterns and vegetation across the United States and will significantly disrupt water supplies, agriculture, forestry and ecosystems for decades, a new federal report says.

The changes are unfolding in ways that are likely to produce an uneven national map of harms and benefits, according to the report, released Tuesday and posted online at climatescience.gov.

The authors of the report and some independent experts said the main value of its projections was the level of detail and the high confidence in some conclusions. That confidence comes in part from the report’s emphasis on the next 25 to 50 years, when shifts in emissions are unlikely to make much of a difference in climate trends.

The report also reflects a recent, significant shift by the Bush administration on climate science. During Mr. Bush’s first term, administration officials worked to play down a national assessment of climate effects conducted mainly during the Clinton administration, but released in 2000.

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Report Details Effects of Climate Change Across U.S.

Washington Post, By Juliet Eilperin, May 28

Global warming is already affecting the nation's forests, water resources, farmland and wildlife, and will have serious negative consequences over the next 25 to 50 years, according to a report issued yesterday by the federal government.

The scientific assessment by the U.S. Climate Change Science Program, which was commissioned by the Agriculture Department and carried out by 38 scientists inside and outside the government, provides the most detailed look in nearly eight years at how climate change is reshaping the American landscape. The report, which runs 193 pages and synthesizes a thousand scientific papers, highlights how human-generated carbon dioxide emissions from burning fossil fuels have already translated into more frequent forest fires, reduced snowpack and increased drought, especially in the West.

Anthony C. Janetos, director of the Joint Global Change Research Institute of the University of Maryland and the Pacific Northwest National Laboratory, said the document aims to inform federal resource managers and dispel the public's perception that global warming will not be felt until years from now.

"They imagine all these ecological impacts are in some distant future," said Janetos, one of the lead authors, who noted that many animals and plants have shifted their migratory and blooming patterns to reflect recent changes in temperature. "They're not in some distant future. We're experiencing them now."

The document concludes that Americans must face the fact that many of these changes are locked in even if the country takes significant steps to cut emissions in the coming decades.

"Climate change is currently impacting the nation's ecosystems and services in significant ways, and those alterations are very likely to accelerate in the future, in some cases dramatically," the report says. "Even under the most optimistic CO2emission scenarios, important changes in sea level, regional and super-regional temperatures and precipitation patterns will have profound effects."