U.S. scientists say if greenhouse gases levels are not reduced soon, significantly warmer global conditions are nearly a certainty during the next century.

Texas A&M University scientists Zhibo Zhan and Ping Yang, and Professor Andrew Dessler conducted a study of the Earth's temperature variations from 2003 to 2008. They discovered changes in the humidity of the atmosphere amplify warming due to greenhouse gas emissions alone. That, they said, confirms it is highly likely the Earth will experience several degrees of warming during the next century if nothing is done to reduce emissions of greenhouse gases.

Using measurements of water vapor from NASA's Atmospheric Infrared Sounder aboard the Aqua satellite, the researchers confirmed that from 2003 to 2008, the humidity in the atmosphere followed temperatures during that five-year period.

Enhanced humidity resulting from more greenhouse gases is viewed as a major factor in projected warmer global temperatures, according to their research.

"This new data shows that as surface temperature increases, so does atmospheric humidity," Dessler said. "Thus, if we dump greenhouse gases into the atmosphere, we'll be making the atmosphere more humid. And since water vapor is itself a greenhouse gas, the increase in humidity amplifies the initial warming."

The study appeared recently in the journal Geophysical Research Letters.