Storms’ Fury Linked to Warming
Hurricanes are becoming more destructive in part due to the effects of global warming, according to research published online Sunday in the journal Nature.
Kerry A. Emanuel, an MIT professor of meteorology, reviewed about five decades of hurricane and typhoon data, and found that both the duration and wind speeds of the storms had increased by 50%.
“When hurricanes do strike in the future, they will, on average, have much greater intensity, hitting harder and lasting longer,” Emanuel noted.
The increased intensity will “substantially increase hurricane-related losses along populated coastlines, hitting people hardest not as previously thought in the tropics but in the middle and high latitudes,” he said.
Hurricanes form over tropical waters and gain strength from heat released when evaporated water falls back to Earth in pounding tropical rains.
Emanuel found a “high correlation” between the growth in hurricane power and sea surface temperatures, whose rise he attributed to both human-induced global warming and natural oscillations in ocean temperature.
The surface temperature of tropical oceans has increased by about 0.9 degree over the last 50 years.
Previous theories have not given much credence to the power of this temperature rise to increase the intensity of hurricanes.
Hurricane prediction models have proposed that the peak wind speed should rise by only 5% for each 1.8-degree rise in ocean temperature.
Emanuel’s research suggests that there must be other forces at work to create the 50% increase in hurricane duration and wind speed.
“We’re trying to ... close that yawning theoretical gap by identifying all the natural forces that might be contributing to the rise, from vertical wind shear to atmospheric temperature,” Emanuel said.
Emanuel noted that his study found no evidence that global warming had increased the frequency of hurricanes.
Last year’s hurricane season caused billions of dollars in damage in the Caribbean and United States. There were nine storms officially designated as hurricanes, which are defined as tropical storms with wind speeds of 74 mph or more.
This year, the National Oceanic and Atmospheric Administration is predicting 12 to 15 tropical storms, with seven to nine becoming hurricanes. The agency estimates that three to five could become major hurricanes.
So far this season, there have been six tropical storms, of which two have been classified as hurricanes. Hurricane season runs from June to November.
