World to be even hotter by century's end

By Robert Sanders, Media Relations | 22 May 2006

BERKELEY – If Earth's past cycles of warming and cooling are any indication, temperatures by the end of the century will be even hotter than current climate models predict, according to a report by University of California, Berkeley, researchers.

The scientists based their conclusion on a study of Antarctic ice cores containing a 360,000-year record of global temperature and levels of carbon dioxide and methane - two of the major greenhouse gases implicated in global warming. They found that during periods of warming, greenhouse gas levels rose and created significantly higher temperatures than would be expected solely from the increased intensity of sunlight that triggered these warm periods.

Climate researchers Margaret Torn and John Harte. (LBNL photo)

Though the ice core data do not point to specific processes that amplify the warming, the researchers suspect that it is due to warmer soils and oceans giving off more CO2 and methane, which add to the greenhouse effect of CO2 from fossil fuel burning and other human activities.

Harte has been conducting studies on experimental plots in the Rocky Mountains that would quantify the effect of warmer temperatures on soil carbon. He and his colleagues found that artificially heated plots lost significant soil carbon to the atmosphere as CO2, compared to control plots. Thus, he said, the effect of heating on the carbon cycle in his plots is to generate a positive feedback, though he noted that this might be a short-term effect. The long term effect, however, is unknown, as is the effect of warming in other habitats.

"We need to know the effect of warmer temperatures in all different habitats, not just temperate Rocky Mountain forests but also the tropics and European boreal forests and Eastern U.S. deciduous forests and savanna and prairie. There are huge data gaps," he said.

Torn noted, however, that humans are the biggest unknown.

"To predict the future, you have to guess how much CO2 levels will go up. That depends on the biggest uncertainty of all - what humans decide to do. Do we get smart and prevent CO2 emissions? Do we continue with business as usual? Or will we end up somewhere in between?"

The work was supported by the U.S. Department of Energy's Climate Change Research Division and by the National Science Foundation.

Posted by Greg Watson on Yahoo Group ClimateConcern