Sun, Sep 25, 2005 - Page 7 News List

Who's right on global warming?

HUMAN-DRIVEN Experts agree that oceans have warmed up in a way that might be a cause of the buildup in greenhouse gases, and climate change

NY TIMES NEWS SERVICE , NEW YORK

An iceberg melts in Kulusuk, Greenland near the arctic circle last month. Scientists say that global warming has an increasing effect on the Arctic region with glaciers shrinking, temperatures of the arctic waters warming, and permafrost softening.

PHOTO: AP

With an American city swamped by one great hurricane and then by another one less than a month later, with federal forecasters ticking down the annual list of 21 names for tropical storms at a record clip, it is no surprise that debate has flared over the role of global warming.

After all, one of the clearest signals that human actions have pushed recent warming beyond natural cycles is a measured buildup of heat in the world's oceans, and oceanic heat is the fuel that powers hurricanes.

The issue has been addressed from starkly different vantage points. For example, former Vice President Al Gore has conducted a continuing speaking tour on the need to cut heat-trapping pollution, while Senator James Inhofe, a Republican from Oklahoma, has accused environmental campaigners of fomenting unfounded fears about human-driven warming.

So what is the state of the science behind the arguments over the message sent by Hurricanes Rita and Katrina?

What is clear is that an array of leading experts on oceans and climate agree that the tropical oceans have warmed in a way that is hard to attribute to anything other than overall warming of the climate from the buildup of carbon dioxide and other greenhouse-gas emissions.

It is also clear to many climate scientists and oceanographers that warmer oceans will eventually increase the intensity and rainfall of hurricanes, but not necessarily their frequency.

In fact, two recent studies of hurricanes, by different scientists using different methods, claimed to detect a big rise in hurricane intensity around the world over the last several decades.

But the authors of both analyses acknowledged that more data would be needed to confirm a link to human-caused warming.

The murkiness arises because the relationship between long-term warming of the climate and seas is only perceptible in statistical studies of dozens of storms, not in the origin or fate of any particular storm.

The growth and trajectory of any one storm is shaped by big natural vagaries in the atmosphere and oceans and chance occurrences, like the passage of both recent hurricanes over meandering eddies of unusually warm water in the Gulf of Mexico.

"It's a coincidence of ideal conditions," said Christopher Landsea, a hurricane expert at the Commerce Department's Atlantic Oceanographic and Meteorological Laboratory outside Miami.

Kerry Emanuel, the author of one of the recent studies showing rising intensity, echoed many colleagues in saying that the impact of global warming was unlikely ever to be manifested in a black and white way that could serve as a call to arms for those seeking curbs on emissions.

Instead, Emanuel, an atmospheric scientist at the Massachusetts Institute of Technology, said it would emerge as if someone had subtly, but progressively, loaded a pair of dice.

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