Slowdown in Warming Linked to Water Vapor

Climatologists have puzzled over why global average temperatures have stayed roughly flat in the past decade, despite a long-term warming trend. New research suggests that lower levels of water vapor in the stratosphere may partly explain the anomaly. The study, appearing in the journal Science, points out that the concentration of water vapor in the stratosphere has dropped about 10% in the past decade, triggered by unexplained cooler temperatures at certain high altitudes above the tropics. The study concludes that in the last decade the decline in water vapor slowed the rate of rising temperatures by about 25%, thus partly negating the heat-trapping effect of increasing greenhouse gases such as carbon dioxide and methane. The recent fluctuation—the flattening of temperatures since the year 2000—isn't merely of academic interest. Those skeptical of man-made global warming say the temperature anomaly supports their case. Others say it is merely a blip, and that warming remains the long-term trend...read more