Global warming predictions are too conservative, researchers at Yale say. Current models fail to account for the importance of changing cloud composition. Photo by NASA/UPI | License Photo

NEW HAVEN, Conn., April 7 (UPI) -- New research suggests current global warming prediction models aren't accounting for cloud composition.

"Clouds and aerosol particles strongly influence the amount of radiation, and thus heating, that occurs in the atmosphere, yet clouds and aerosol particles are currently the leading cause of uncertainty in climate projections," researchers with the American Association for the Advancement of Science announced in a press release.


In a new study published in the journal Nature, researchers from Yale and the Lawrence Livermore National Laboratory, argue that clouds increasingly have less ice and more water in them. As this trend continues, they say, clouds will trap more heat and reflect less solar energy.

Current models endorsed by the United Nations predict a rise of 2 to 4.7 degrees Celsius in global average temperature if CO2 levels continue to rise as expected. The new research predicts an increase between 5 and 5.3 degrees Celsius.

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Prolonged cloud cover is often associated with cooling periods. But ice particles in the upper atmosphere play an important role in blocking the sun's rays from warming the Earth's surface. Researchers expect that role to be diminished as upper atmospheric clouds host more liquid water molecules.

"We saw that all of the models started with far too much ice," Trude Storelvmo, a Yale assistant professor of geology and geophysics, said in a news release. "When we ran our own simulations, which were designed to better match what we found in satellite observations, we came up with more warming."

"The overestimate of ice in mixed-phase clouds relative to the observations is something that many climate modelers are starting to realize," added Ivy Tan, a Yale graduate student and lead author of the new study.