"The bottoms of the clouds rise with warmer temperatures, while the top of the cloud stays the same so the clouds become thinner, " explained Del Genio.

CNN: Clouds' role in global warming studied

Del Genio studied more than 3, 000 individual cloud "snapshots" collected between 1994 and 1997 at the Department of Energy's Atmospheric Radiation Measurement Southern Great Plains field station.

CNN: Clouds' role in global warming studied

"The minimum amount of warming predicted by scientists - 3 degrees Fahrenheit - should be increased by at least 1 F as a result of the new findings, " said Del Genio.

CNN: Clouds' role in global warming studied