While storms rage across the planet, climatologists debate the
reasons why, and insurers raise their rates.
Hurricane-weary coastal residents battening down for the '06 season
don't have much cause for optimism. Scientists agree the Atlantic
basin is undergoing a normal surge in hurricanes. And some say
global warming will worsen the outlook.
But hurricane climatology remains a less precise science than
conveyed by cable television's drumbeat of doom. Seasonal forecasts
are rarely accurate, and sometimes they are way off. Meanwhile,
climatologists who worry about longer-range trends admit they
grapple with huge gaps in data and chaotic, little-understood
Known: The Atlantic basin is in a cyclical upswing
in hurricane landfalls dating back 150 years in human records and
500 years in natural indicators such as tree rings.
Unknown: How long this upswing will persist. Past
cycles have lasted from 10 to more than 30 years. "These cycles
that we talk about are not like night and day; they're irregular,"
explains Florida state climatologist James O'Brien.
Known: Warming of the eastern Pacific known as El
Niño reduces Atlantic hurricanes. La Niña, when the
Pacific cools, has the opposite effect.
Unknown: Whether this year's weak La Niña
will persist long enough into the fall season to punch up the '06
Known: Hurricanes have been forming farther south, nearer the
equator, which climatologist say is why so many storms have
targeted Florida and the Gulf Coast in recent years. Unknown: Why
this is happening and whether the pattern will continue. O'Brien
says hurricanes more often strike Florida and the Gulf Coast in El
Niño and normal years, and the East Coast in La Niña
Known: Tropical ocean temperatures have increased,
in some places by as much as one degree, in the past 35
In dispute: Whether this worsens hurricane
intensity. Judy Curry, a climatologist at the Georgia Institute of
Technology, co-authored a paper in Science last fall contending
that the number of Category 4 and 5 hurricanes worldwide nearly
doubled during the past 35 years. The scientists tried to find
other causes, but the only commonality across the world's oceans
was rising sea-surface temperatures. "There's no other explanation
that works," she says.
Skeptics, however, question the reliability of the early satellite
data. O'Brien also notes that the study's earliest year, 1970,
coincides with one of the Atlantic cycle's historical lows. In
response, Curry emphasizes that she found a similar upswing in all
oceans "and the Atlantic in terms of intensity is by no means the
Known: High-altitude winds break the tops off
hurricanes and dampen the storms, a phenomenon known as wind
Unknown: A way to predict seasonal shear
long-term. "If you look for trends in wind shear, you don't see
them," Curry says.
While the science remains uncertain, insurers, at least, are
hedging their bets. Stung by a reported $3.4 billion hurricane loss
in 2005, Warren Buffett announced in his annual letter to investors
this year that Berkshire Hathaway is raising the price of hurricane
re-insurance, in part because of unknowns about global climate
change. — Aaron Hoover