Tuesday, May 29, 2007

Will Global Warming Increase Hurricanes?

Here is another article linking global warming with the intensity and frequency of hurricanes. Two things are apparent to me. First, scientists greatly disagree with each other and admit their climate models are lacking. Second, and most importantly, if mankind is not causing and cannot control global warming, then our best course of action is simply to prepare for hurricanes as we always have. There is nothing we can do to prevent or control them.



Will Warming Lead to a Rise in Hurricanes?

Published: May 29, 2007
When people worry about the effects of global warming, they worry more about hurricanes than anything else. In surveys, almost three-quarters of Americans say there will be more and stronger hurricanes in a warming world. By contrast, fewer than one-quarter worry about increased coastal flooding.

Erik S. Lesser for The New York Times

Researchers hope to better predict storms like Katrina.
But as far as the scientific consensus is concerned, people have things just about backward.
There is no doubt that as the world warms, seas will rise, increasing the flood risk, simply because warmer water occupies more space. (And if the Greenland or Antarctic ice sheets melt, the rise will be far greater.)

It seems similarly logical that as the world warms, hurricanes will be more frequent or more powerful or both. After all, they draw their strength from warm ocean waters. But while many scientists hold this view, there is far less consensus, in part because of new findings on other factors that may work against stronger, more frequent storms.

“Global warming is as real as it gets,” Richard A. Anthes, president of the University Corporation for Atmospheric Research, said last month at a weather conference in the Bahamas, where most of the conversation focused on hurricanes. But as for its link to hurricanes, Mr. Anthes said, “I don’t think it’s been proved conclusively.”
In a consensus statement issued last year, the World Meteorological Organization said it was likely that there would be some increase in hurricane wind speeds in a warmer world. But the organization, which is the United Nations weather agency, noted that decades-long periods of high and low hurricane activity, unconnected to any climate change, had been recorded before. (Climate experts say a period of high activity began in 1995.)
Also, measurement techniques have greatly improved in recent decades, making it difficult to compare data and detect trends.

So as the annual hurricane season begins on June 1, scientists are pressing on a number of fronts to learn how hurricanes form and move, what factors limit or expand their lethal potential and how to tell with greater precision when and where they will strike.

Perhaps the best known proponent of the idea that warming and hurricanes may be connected is Kerry A. Emanuel, an atmospheric scientist at the Massachusetts Institute of Technology. His conclusion that the total power released in Atlantic and western Pacific hurricanes had increased perhaps by half in recent decades, reported in 2005 in the journal Nature, is one of the most discussed ideas in the debate.

He is not alone. Last year, researchers led by Carlos D. Hoyos of the Georgia Institute of Technology analyzed the frequency of Category 4 and 5 storms, the most powerful, and concluded that their increased frequency since 1970 was “directly linked to the trend in sea-surface temperature,” which is increasing. They reported their findings in the journal Science.
Other experts challenge the idea that a warmer world means more and stronger storms.
For example, researchers at the National Oceanic and Atmospheric Administration and the University of Miami have been studying how vertical wind shear — the differences in wind direction or speed at different altitudes — can inhibit hurricane formation.

In work reported last month in Geophysical Research Letters, the researchers said that in a warming world, wind shear in the Atlantic would increase, possibly enough to cancel out the hurricane-forcing effects of warmer water.
Last week, researchers at the Woods Hole Oceanographic Institution in Massachusetts reported in the journal Nature that periods of frequent storminess had occurred in the past, even though things were cooler than they are now. They also concluded that wind currents were a crucial factor.

But even these researchers call the question open. “This doesn’t settle the issue,” said Gabriel Vecchi, the lead author of the wind shear study and a research scientist at the NOAA Geophysical Fluid Dynamics Laboratory, in Princeton, N.J.
In February, researchers led by James Kossin, an atmospheric scientist at the University of Wisconsin, recalibrated recent and early satellite data on hurricanes using information from the National Climatic Data Center, a NOAA archive in Asheville, N.C. They concluded that hurricane frequency had increased, but only in the Atlantic, possibly because temperatures there are chronically just about warm enough for storms; so even modest warming makes hurricanes more likely.

But when Christopher W. Landsea analyzed historical records of hurricane activity, he concluded that satellite observations and other new techniques had increased scientists’ ability to detect major storms, skewing the frequency data. Dr. Landsea, a meteorologist at the National Hurricane Center, reported this conclusion this month in EOS, an electronic publication of the American Geophysical Union.

This kind of he-said-he-said debate often leads people to dismiss a subject as one about which nothing will ever be known with confidence. In fact, the give and take is an example of the way scientists tug and haul at their own and others’ findings until a consensus takes shape.
In the current debate over global warming and hurricanes, the problem is relatively new and the data are hard to obtain and analyze. (original article continued)

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