Hurricane destruction powers global warming debate

By Jim Loney

MIAMI (Reuters) – For a brief time in October, the pressure
inside 185-mph (298 kph) Hurricane Wilma dropped to an
astonishing low, making it the most intense hurricane ever
recorded in the Atlantic and Caribbean.

That historic cyclone happened during a record-shattering
hurricane season that produced 28 storms and occurred only
weeks after Katrina swamped New Orleans, causing $80 billion in
damage.

The ferocity of last year’s season gave ammunition to a
growing chorus of voices that says humans and their greenhouse
gas-spewing cars and factories could be making hurricanes more
destructive.

But it did nothing to convince a hard core of hurricane
researchers who insist there’s no evidence that people are
responsible for the recent intensity, and growing numbers, of
tropical cyclones.

The stakes are high. An estimated 50 million people live
along the hurricane-vulnerable U.S. east and Gulf coasts.

Millions more live in flood-prone mountains in Haiti and
Central America, where hurricanes take thousands of lives.

The U.S. hurricane tab last year was more than $100
billion. Major storms in the 2004 season caused another $45
billion in damage.

“The coastal regions are in jeopardy. The Miami area and
the New Orleans area are very much at risk. We have a 10-year
window to do something about greenhouse gases,” said Prof.
Judith Curry, chair of the School of Earth and Atmospheric
Sciences at the Georgia Institute of Technology.

“STUNNING INCREASES”

Curry said leading scientists with published research have
compelling evidence that human-induced global warming is
heating the seas from which hurricanes draw their strength. In
the North Atlantic — as the Atlanic north of the equator is
called — that has increased both the number and intensity of
hurricanes in the last decade, she said.

“They are stunning increases that are way outside the
bounds of natural variability,” she said.

Tropical ocean temperatures have risen about 1 degree
Fahrenheit since 1970, said Curry. “This 1 degree is playing
havoc with hurricanes. It’s a lot of extra energy for these
storms.”

When Wilma’s internal pressure hit 882 millibars, beating a
record held by 1988′s Gilbert, climatologists took notice. It
was the first time a single season had produced four Category 5
hurricanes, the highest stage on the 5-step Saffir-Simpson
scale of storm intensity.

The 28 tropical storms and hurricanes crushed the old mark
of 21, set in 1933.

While some hurricane researchers accept that the sea is
warming, they believe it’s part of a natural cycle, rather than
human-caused.

They say the Atlantic entered a period of heightened
hurricane activity around 1995 and may not settle down for
another 20 or 30 years due to a cycle called the “Atlantic
multidecadal oscillation.”

With hurricane records for only 150 years, some say there
isn’t enough historical data to blame the greenhouse effect.

“We don’t have any facts because we don’t have any
long-term records,” said Neil Frank, a former director of the
U.S. National Hurricane Center.

The debate has taken center-stage among hurricane and
climate scientists in the United States, where President George
W. Bush’s rejection of the Kyoto agreement to cut greenhouse
gases enraged environmental groups and foreign nations.

Some U.S. scientists say Washington has stifled dissenters.
Others deny it. “No one has put any pressure on me, from the
White House or anywhere else,” U.S. National Hurricane Center
director Max Mayfield said.

GROWING EVIDENCE

After two of the worst seasons on record — 2004 produced
15 storms — U.S. researchers are speaking more boldly.

At an American Meteorological Society conference in
Monterey, California, last week, a U.S. government researcher
blamed last year’s record season on global warming.

On the web site of the government’s Geophysical Fluid
Dynamics Laboratory, the subject is broached frankly.

“The strongest hurricanes in the present climate may be
upstaged by even more intense hurricanes over the next century
as the earth’s climate is warmed by increasing levels of
greenhouse gases….,” it says.

Kerry Emanuel, a professor at the Massachusetts Institute
of Technology, wrote in Nature magazine last August that the
power dissipated by hurricanes in the North Atlantic has
doubled in the last 30 years, possibly because storms have been
more intense for longer periods of time.

“My results suggest that future warming may lead to an
upward trend in tropical cyclone destructive potential,” he
wrote.

A study by Curry and her colleagues published in Science
magazine last fall found the proportion of hurricanes reaching
Category 4 and 5 has nearly doubled in the last 35 years.

But Frank, the former hurricane center director who now is
a weatherman for KHOU television in Houston, said he does not
believe hurricanes are more frequent or more intense than they
were in the last warming period, in the 1930s, ’40s and ’50s.

Only since the 1970s have researchers had satellites that
allow them to look directly at hurricanes. As a result, he
believes, storms that might have escaped detection in mid-ocean
decades ago are now tracked from birth to death.

Scientists who believe human-induced global warming is
linked to hurricane formation and strength rely too heavily on
numerical models, Frank said.

“These same numerical models that I can’t put faith in for
a two-week forecast, we’re told can be accurate out 200 years,”
he said. “Ridiculous.”

Whatever the outcome of the debate, forecasters say the
damaging seasons of 2004 and 2005 could be just the beginning.

“I’m here to tell you it can get worse,” Mayfield said.