Feb 7, 2010

brake in the storm

While assessing the risks and pace of climate change remains a difficult task, our core understanding of the physics and chemistry of the atmosphere grows ever more complete. Last month a new study was published that helps explain why surface air temperatures have not increased as rapidly over the past decade as have ocean temperatures. According to NOAA researcher Susan Solomon and colleagues, the stratosphere has dried by about 10 percent since 2000, resulting in a 25 percent decline in surface temperature relative to what would have been without the drying effect. The Economist published a good review of the paper.

This research is largely observational. The authors are not sure why less water vapor passed through the tropopause into the stratosphere, and this will surely become an object of study. Climate scientists suspect that increased thunderstorm activity in the tropics caused the drying, with more water vapor exiting the troposphere as rain rather than rising into the stratosphere. Why there were more thunderstorms is not known, but increased variability in weather is one of the basic predictions of global warming.

Atmospheric heat can either dissipate into the oceans and land or it can get converted to entropy. Storms are weather patterns that become organized, thus they represent energy becoming organized into entropy. The most persistent and destructive effect of global warming is thermal expansion of the oceans. Most of the heat that has accumulated in the past century has wound up in the oceans, not the atmosphere, and sea level rise threatens people and economies more than storms. More frequent and powerful storms are a bad thing, but this new study shows there may be a silver lining in those storm clouds. They consume energy and act as a buffer against warming.

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