Report links global warming, storms

[kurth]

Report links global warming, storms
- Keay Davidson, Chronicle Science Writer
Tuesday, September 12, 2006

Scientists say they have found what could be the key to ending a yearlong debate about what is making hurricanes more violent and common -- evidence that human-caused global warming is heating the ocean and providing more fuel for the world's deadliest storms. For the past 13 months, researchers have debated whether humanity is to blame for a surge in hurricanes since the mid-1990s or whether the increased activity is merely a natural cycle that occurs every several decades.

Employing 80 computer simulations, scientists from Lawrence Livermore National Laboratory and other institutions concluded that there is only one answer: that the burning of fossil fuels, which warms the climate, is also heating the oceans. Humans, Ben Santer, the report's lead author, told The Chronicle, are making hurricanes globally more violent "and violent hurricanes more common" -- at least, in the latter case, in the northern Atlantic Ocean. The findings were published Monday in the latest issue of the Proceedings of the National Academy of Sciences.

Hurricanes are born from tropical storms fueled by rising warm, moist air in the tropics. The Earth's rotation puts a spin on the storms, causing them to suck in more and more warm, moist air -- thus making them bigger and more ferocious. In that regard, the report says, since 1906, sea-surface temperatures have warmed by between one-third and two-thirds of a degree Celsius -- or between 0.6 and 1.2 degrees Fahrenheit -- in the tropical parts of the Atlantic and Pacific oceans, which are hurricane breeding grounds....

Researchers report in the Proceedings paper an 84 percent chance that at least two-thirds of the rise in ocean temperatures in these so-called hurricane breeding grounds is caused by human activities -- and primarily by the production of greenhouse gases. Tom Wigley, one of the world's top climate modelers and a co-author of the paper, said in a teleconference last week that the scientists tried to figure out what caused the oceans to warm by running many different computer models based on possible single causes. Those causes ranged from human production of greenhouse gases to natural variations in solar intensity. Wigley said that when the researchers reviewed the results, they found that only one model was best able to explain changing ocean temperatures, and it pointed to greenhouse gases in the atmosphere. The most infamous greenhouse gas is carbon dioxide, a product of human burning of fossil fuels in cars and factories...

http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/09/12/MNG5HL3S611.DTL