Climate Projections Underestimate CO2 Impact

http://www.usgs.gov/newsroom/article.asp?ID=2358

Released: 12/7/2009 1:50:12 PM
Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192

The climate may be 30–50 percent more sensitive to atmospheric carbon dioxide in the long term than previously thought, according to a study published in Nature Geoscience yesterday.

Projections over the next hundreds of years of climate conditions, including global temperatures, may need to be adjusted to reflect this higher sensitivity.

“Climate change is affecting water supplies for cities and farms; leading to more severe droughts, hurricanes, and floods; contributing to more intense forest fires; and putting coastal communities at risk,” said Secretary of the Interior Ken Salazar, who is on his way to the global climate change conference convening this week in Copenhagen. “This study and the ongoing work of our USGS scientists will help us continue to build more precise long-term projections and to prepare for the impacts of climate change on our world.”

A team of scientists, led by the University of Bristol and including the U.S. Geological Survey, studied global temperatures 3.3 to 3 million years ago, finding that the averages were significantly higher than expected from the atmospheric carbon dioxide levels at the time.

These underestimates occurred because the long-term sensitivity of the Earth system was not accurately taken into account. In these earlier periods, Earth had more time to adjust to some of the slower impacts of climate change. For example, as the climate warms and ice sheets melt, Earth will absorb more sunlight and continue to warm in the future since less ice is present to reflect the sun.

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