Scientists Debunk 'Global Warming' Effect on Hurricanes

By Melanie Arter | July 7, 2008 | 8:22 PM EDT

( - The recent onslaught of hurricanes has prompted some media outlets to mention "global warming" as a possible cause, but a team of climate researchers set the record straight.

A group of climatologists, scientists, professors and other experts in climate change on Tuesday pointed out two "misconceptions" reported in the press about hurricanes and their relation to climate change, in a letter to Sen. John McCain (R-Ariz.), who chaired a Commerce Committee hearing examining recent scientific research concerning climate change impacts.

"First is the erroneous claim that hurricane intensity or frequency has risen significantly in recent decades in response to the warming trend seen in surface temperature. Second is the claim that a future surface warming trend would lead to more frequent and stronger storms. We believe that both of these are demonstrably false," the scientists wrote.

They noted the National Hurricane Center reports in the last century the decade with the largest number of hurricanes to hit the U.S. was the 1940s, and the frequency of hurricanes has gone down since then.

According to the United Nations Environment Programme of the World Meteorological Organization, "Reliable data ... since the 1940s indicate that the peak strength of the strongest hurricanes has not changed, and the mean maximum intensity of all hurricanes has decreased."

"Recent history tells us that hurricanes are not becoming more frequent," the climate researchers wrote in the letter to McCain.

The second claim in news stories about hurricanes and "global warming," they pointed out, involves the question "if surface warming trends continue, are more or fewer severe storms likely?"

"Computer simulations suggest that in a warmer world most of the warming would occur in the Polar Regions. Atmospheric circulation, which crucially affects storms, is driven primarily by the temperature difference, or gradient, between the tropics and the poles," the experts wrote.

"Warmer polar regions would reduce this gradient and thus lessen the overall intensity or frequency or both of storms - not just tropical storms but mid-latitude winter storms as well (such as blizzards and northeasters)," the climatologists added.

"Again, longer periods of history bear this out. In the past, warmer periods have seen a decline in the number and severity of storms. This is well-documented in scientific journals for data extending back centuries or even millennia. If the surface temperature of the planet rises further in the future, it is likely that these declines will continue," they wrote.

The experts noted that the hurricane season has not yet ended and said the frequency of hurricanes varies.

"We suggest that natural variability of storminess is the cause of Florida's recent hurricane disasters. In such times there is an emotional tendency to pin blame somewhere," they wrote.

"But rather than blaming global warming - for which there is little supporting meteorological evidence - emphasis on emergency preparedness and further storm research would be a constructive response," they added.

The experts include Dr. James O'Brien, professor of meteorology & oceanography at the Center for Ocean-Atmospheric Prediction Studies at Florida State University; Dr. Gary Sharp, scientific director at the Center for Climate/Ocean Resources Study; Dr. Anthony Lupo, professor of atmospheric science at the University of Missouri - Columbia; Dr. David Legates, associate professor of climatology at the University of Delaware; and George Taylor, Oregon State climatologist.

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