New Climate Report Foresees Big Changes

By ANDREW C. REVKIN

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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