Let's re-evaluate the role of CO2....

Some new scientific evidence on the role of CO2...

Its the strongest evidence for the Greenhouse Gas theory of global warming -- that warm periods in the earth's past were typically accompanied by rises in atmospheric carbon dioxide. But that evidence is under serious attack, from new research funded by the U.S. National Science Foundation.

The research team, led by Paleoclimatologist Lowell Stott, demonstrated CO2 levels after the last Ice Age started to rise some 1,300 years after the warming began. According to Stott, earlier researchers had cause and effect reversed -- CO2 increases were the result of warming, and not the original cause. Stott's paper is not the first to show CO2 rises followed warming trends, but it is one of the most detailed and thorough rebuttals of the linkage.

The work comes hot on the heels of other research downgrading CO2's importance in climate change. Earlier this year, the Belgian Royal Meteorological Institute issued a study saying CO2 effects had been "grossly overstated." Dr. Steven Schwartz of Brookhaven National Labs concluded that CO2-based warming had been overstated by some 400%, and a pair of Chinese researchers used mathematical modeling to demonstrate the majority of current warming was natural in origin.

Stott's findings are important for two reasons. First, they directly challenge the correlation between CO2 and warming. As Stott himself points out, CO2 is still likely a contributor to climate change, but its role needs to be reevaluated.

The results also weaken the belief that present-day atmospheric CO2 increases must be anthromorphic -- human-induced. Stott's model showed how the warming generated changed ocean conditions, which then generated massive releases of CO2 from the ocean into the atmosphere. As natural CO2 sources still constitutes more than 97% of all emissions, this may not come as much of a surprise.

But if CO2 didn't cause the warming, what did? Stott's model links the forcing to periodic changes in the Earth's orbit which increase solar radiation over Antarctica. This eventually causes ice sheet retreat, which lowers ocean albedo, reflectivity. Additional warming is generated, a feedback effect which over 1,000 or more years, transports heat via deep-sea currents to the Northern Hemisphere. The model also explains why surface measurements of solar insolation fail to correlate with warming ... the heat transport process is very slow, and thus surface warming lags centuries behind changes in solar output.

Stott is a professor at the University of Southern California, and a reviewer for the United Nations' Intergovernmental Panel on Climate Change.