Monday, May 19, 2008

Climate change 'to make Atlantic hurricanes rarer'

Olive Heffernan in Nature: Hurricanes may become rarer in the Atlantic throughout the 21st century if the world continues to warm, suggests a new study. The research is the latest to address the question of how — and whether — global warming will affect the intensity and frequency of hurricanes.

Globally, the number of major hurricanes has shot up by 75% since 1970. And although rising ocean temperatures are generally accepted as the key culprit — hurricanes can only form where sea surface temperatures exceed 26ÂșC — the link to global warming has remained a contentious issue. In the new study, published today in Nature Geoscience , Thomas Knutson of the US National Oceanic and Atmospheric Administration (NOAA) and colleagues used a regional climate model of the Atlantic basin to simulate the observed increase in hurricane activity between 1980 and 2006, on the basis of observed sea-surface temperatures and atmospheric conditions. “The study does not support the notion that rising greenhouse gases are causing an increase in tropical storm frequency,” says Knutson…

Kevin Trenberth, a climatologist at the National Center for Atmospheric Research in Boulder, Colorado, who was not involved in the study, agrees to an extent with the findings. “The results suggest fewer tropical storms in the Atlantic, and this seems reasonable given everything else we know”. But he cautions that the authors may have underestimated increases in hurricanes and really severe storms, owing to the fact that their model was fairly low-resolution and could not account for changes in some of the largest of these events. “In this business it is not the numbers that matter, it is also the intensity, duration and size,” he says.

That's the eye of Hurricane Isabel, taken from the International Space Station in 2003, NASA, Wikimedia Commons

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