Scientists: Pace of Climate Change Exceeds Estimates

The pace of global warming is likely to be much faster than recent predictions, because industrial greenhouse gas emissions have increased more quickly than expected and higher temperatures are triggering self-reinforcing feedback mechanisms in global ecosystems, scientists said Saturday.

"We are basically looking now at a future climate that's beyond anything we've considered seriously in climate model simulations," Christopher Field, founding director of the Carnegie Institution's Department of Global Ecology at Stanford University, said at the annual meeting of the American Association for the Advancement of Science.

Field, a member of the United Nations' Intergovernmental Panel on Climate Change, said emissions from burning fossil fuels since 2000 have largely outpaced the estimates used in the U.N. panel's 2007 reports. The higher emissions are largely the result of the increased burning of coal in developing countries, he said.

Unexpectedly large amounts of carbon dioxide are being released into the atmosphere as the result of "feedback loops" that are speeding up natural processes. Prominent among these, evidence indicates, is a cycle in which higher temperatures are beginning to melt the arctic permafrost, which could release hundreds of billions of tons of carbon and methane into the atmosphere, said several scientists on a panel at the meeting.

The permafrost holds 1 trillion tons of carbon, and as much as 10 percent of that could be released this century, Field said. Melting permafrost also releases methane, which is 25 times more potent a greenhouse gas than carbon dioxide.

"It's a vicious cycle of feedback where warming causes the release of carbon from permafrost, which causes more warming, which causes more release from permafrost," Field said.

Evidence is also accumulating that terrestrial and marine ecosystems cannot remove as much carbon from the atmosphere as earlier estimates suggested, Field said.


http://www.washingtonpost.com/wp-dyn/content/article/2009/02/14/AR2009021401757.html