When it comes to predicting climate change, the forecasts are usually grim. But a report published in the March issue of the Bulletin of the American Meteorological Society offers a glimmer of hope. According to the new findings, Earth may be able to significantly reduce global warming by releasing some of the heat through a "vent" in the cloud cover over the Pacific Ocean.

Analyzing data collected over a 20-month period, scientists from NASA's Goddard Space Flight center in Greenbelt, Md., and the Massachusetts Institute of Technology found that the number of cirrus clouds above the Pacific Ocean declines with warmer sea surface temperatures. "With warmer sea surface temperatures beneath the cloud, the coalescence process that produces precipitation becomes more efficient," team member Richard S. Lindsen of M.I.T. explains. "More of the cloud droplets form raindrops and fewer are left in the cloud to form ice crystals. As a result, the area of cirrus cloud is reduced." These thin, icy clouds do little to block solar radiation, but they effectively trap heat. In the long term, reduction of the cloud cover could allow the heat to escape, thus cooling the planet.

So far the team has looked only at data from the Pacific Ocean region, but if other tropical oceans have the same effect, Earth may be well equipped to handle global warming. Indeed, the team estimates that this cooling effect could reduce by two-thirds the predicted increase in global temperatures initiated by a doubling of atmospheric carbon dioxide.