Scientists are Split over Hurricane Trends

PARIS: A year after Hurricane Katrina wrecked New Orleans, a storm of a different kind is buffeting climate scientists: are hurricanes becoming more vicious or more frequent? The raw fuel for tropical storms is a warm sea, so experts have long speculated that global warming, by driving up ocean surface temperatures, is bound to intensify hurricanes and their Asian cousins, typhoons.

That debate was largely framed on what might happen 30 or 40 years from now or even longer. After the shock of Katrina and a series of new studies, the focus shifted abruptly from the middle distance to the present. Has the feared link between warming and storms alreadykicked in? Many scientists urge caution. They say hurricane hyperactivity, as was the case in 2004 and 2005, occurs in what appears to be cycles and they say the meteorological data is just too recent and too sketchy to venture a firm conclusion.

Though, offer long-term evidence for saying Atlantic storms have become progressively worse in the last few decades. And, they note, this increase also tracks a rise in emissions of carbondioxide gas from fossil fuels, which traps solar heat and thus warms the seas. "We have known since 1987 that the intensity of hurricanes is related to surface sea temperature, and we know that over the last 15 to 20 years surface sea temperatures in these regions have increased by half a degree Celsius, (0.9 degrees Fahrenheit)," said the British government's chief scientist, David King. "So it is easy to conclude that the increased intensity of hurricanes is associated with global warming." Kerry Emanuel, a professor at theMassachusetts Institute of Technology, began to warn of a link between hurricane intensity and global warming way back in 1987.

According to Emanuel's calculations, the power of tropical cyclones has roughly doubled since the 1950s. His measurement, a power dissipation index, is based on storm intensity and duration.He notes a significant rise over the last 30 decades - when Earth's surface temperatures began to rise significantly - but especially since 1995, when global mean temperatures began to scale ever-higher annual peaks.

"The large upswing in the last decade is unprecedented and probably reflects the effects of global warming,"Emanuel said. Peter Webster of the Georgia Institute of Technology and the National Center for Atmospheric Research in Boulder, Colorado, calculates that category 4 and 5 hurricanes - the two most powerful storm ratings - have nearly doubled in number over the past three decades.

Critics point to what they say is the weakness of historical data. Philip Klotzbach, a meteorologist at Colorado State University, says satellite records prior to 1984 are unreliable. He sees an increase in post-1984 hurricane frequency but says it has been prompted by the simple fact that better measuring tools have become available. For other experts, the question of whether hurricanes are worse today is less urgent than the fate of coastal cities that are already badly exposed to storms- and could become more vulnerable.

To be continue in other article...

(Jakarta, Senin 25 February 2008)

Re-publish by Jacob Paradox from link (www.routers.com),(www.iht.com), (www.routers.com), (www.nytimes.com)

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