Brace for More Katrinas, Say Experts

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http://www.truthout.org/issues_05/083105EA.shtml

 

 

 

 

Brace for More Katrinas, Say Experts

Agence France Presse

 

Tuesday 30 August 2005

 

Paris - For all its numbing ferocity, Hurricane Katrina will not

be a unique event, say scientists, who say that global warming appears

to be pumping up the power of big Atlantic storms.

 

2005 is on track to be the worst-ever year for hurricanes,

according to experts measuring ocean temperatures and trade winds -

the two big factors that breed these storms in the Caribbean and

tropical North Atlantic.

 

Earlier this month, Tropical Storm Risk, a London-based consortium

of experts, predicted that the region would see 22 tropical storms

during the six-month June-November season, the most ever recorded and

more than twice the average annual tally since records began in 1851.

 

Seven of these storms would strike the United States, of which

three would be hurricanes, it said.

 

Already, 2004 and 2003 were exceptional years: they marked the

highest two-year totals ever recorded for overall hurricane activity

in the North Atlantic.

 

This increase has also coincided with a big rise in Earth's

surface temperature in recent years, driven by greenhouse gases that

cause the Sun's heat to be stored in the sea, land and air rather than

radiate back out to space.

 

But experts are cautious, also noting that hurricane numbers seem

to undergo swings, over decades.

 

About 90 tropical storms - a term that includes hurricanes and

their Asian counterparts, typhoons - occur each year.

 

The global total seems to be stable, although regional tallies

vary a lot, and in particular seem to be influenced by the El Nino

weather pattern in the Western Pacific.

 

" (Atlantic) cyclones have been increasing in numbers since 1995,

but one can't say with certainty that there is a link to global

warming, " says Patrick Galois with the French weather service

Meteo-France.

 

" There have been other high-frequency periods for storms, such as

in the 1950s and 60s, and it could be that what we are seeing now is

simply part of a cycle, with highs and lows. "

 

On the other hand, more and more scientists estimate that global

warming, while not necessarily making hurricanes more frequent or

likelier to make landfall, is making them more vicious.

 

Hurricanes derive from clusters of thunderstorms over tropical

waters that are warmer than 27.2 C (81 C).

 

A key factor in ferocity is the temperature differential between

the sea surface and the air above the storm. The warmer the sea, the

bigger the differential and the bigger the potential to " pump up " the

storm.

 

Just a tiny increase in surface temperature can have an

extraordinary effect, says researcher Kerry Emanuel of the

Massachusetts Institute of Technology (MIT).

 

In a study published in Nature in July, Emanuel found that the

destructive power of North Atlantic storms had doubled over the past

30 years, during which the sea-surface temperature rose by only 0.5 C

(0.9 F).

 

Emanuel's yardstick is storm duration and windpower: hurricanes

lasted longer and packed higher windspeeds than before.

 

Another factor in destructiveness is flooding. Kevin Trenberth of

the US National Center for Atmospheric Research suggests that

hurricanes are dumping more rainfall as warmer seas suck more moisture

into the air, swelling the stormclouds.

 

The indirect evidence for this is that water vapour over oceans

worldwide has increased by about two percent since 1988. But data is

sketchy for precipitation dropped by recent hurricanes.

 

" The intensity of and rainfalls from hurricanes are probably

increasing, even if this increase cannot yet be proven with a formal

statistical test, " Trenberth wrote in the US journal Science in June.

He said computer models " suggest a shift " toward the extreme in in

hurricane intensities.