Drier Atmosphere Slows Global Warming

A decrease in water vapor in the stratosphere may be the reason global warming hasn't increased as fast as expected over the last 10 years. The planet warmed .18 degree from 2000 to 2009, below the forecast .25 degree. A 10% drop in stratospheric water vapor “very likely made substantial contributions to the flattening of the global warming trend,” says the lead author of a new study in Science.

“We call this the 10/10/10 paper,” Susan Solomon tells USA Today. “Ten miles above your head, there is 10% less water vapor than there was 10 years ago.” The reason for the decline is unclear. Still, Solomon, who was a key player in establishing that climate change exists, says the findings don’t refute the theory. “This doesn't mean there isn't global warming. There's no significant debate that it is warmer now than it was 100 years ago.” (More global warming stories.)