Climate modeler admits to being often wrong

by William Yeatman on June 22, 2004

Two years after beginning a $20 million study of the effects of cirrus thunderhead clouds on the climate, NASA researchers have discovered that they play a significant part in determining how much sunlight is reflected back into space.

The studies directly contradict assumptions inherent in climate models, meaning that the role of cirrus formations in predicting climate will have to be reconsidered.

Weve got some amazing results that no one anticipated, says Anthony Del Genio, a climate modeler with NASA’s Goddard Institute for Space Studies at Columbia University in New York, told the Christian Science Monitor (June 24). It’s humbling to find out how often you’re wrong.

The Monitor summarized, One of the most fundamental questions surrounds the size of the ice crystals that make up tropical cirrus clouds. A team led by Timothy Garrett at the University of Utah found that the ice crystals in anvil cirrus over south Florida are smaller and reflect light more effectively than most models assume. The results suggest that when the clouds are thick as they first form over the top of a thunderhead, they reflect substantially more light back into space than models currently show.

The researchers also found, however, that the ice crystals carried nitric acid, which acted as antifreeze, so therefore allowing more water present as vapor.  Water vapor is the principal greenhouse gas.  In one case, the ice crystals were formed around dust from a plume that blew across the North Atlantic.  Again, this effect had not been accounted for in climate models.

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