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Record year for hurricanes part of a
natural cycle
By Tom Vanden Brook, USA TODAY
Natural climate conditions, not global warming, created the
record-breaking 2005 tropical storm season, the nation's top
hurricane experts said Tuesday.
Three ingredients combined to generate
more and stronger hurricanes in 2005, said Gerry Bell, lead
meteorologist for the National Oceanic and Atmospheric
Administration's Climate Prediction Center. Warm ocean water
helps fuel storms, and Atlantic water temperatures were 2 to 3
degrees above average this year, he said. There was an absence
of winds high in the atmosphere that can tear hurricanes apart.
And winds blowing east from Africa steered developing storms
toward warmer waters where they incubated into tropical storms
and hurricanes.
That combination of factors has occurred
periodically through history, Bell said. Meteorologists refer to
such an active hurricane cycle as the "multi-decadal signal." It
can last for 30 years. The current period began in 1995. A
record 26 tropical storms formed this season, which began June 1
and ends today.
"It's not related" to global warming,
Bell said. The same conditions occurred in the 1950s and 1960s,
the last period of above-normal hurricane activity. Many records
set in 2005, including most hurricanes in a season — 13 —
surpassed marks set then. (Related story:
'06 forecast: More stormy weather)
The opposite conditions occurred between
1970 and 1994 and coincided with below-average hurricane
seasons. "The climate patterns that we're seeing now didn't
exist in the 1970s, '80s and most of the 1990s," Bell said.
William Gray, head of Colorado State
University's Tropical Meteorology Project, also says on his
website that there's no evidence that global warming has caused
more hurricanes.
Despite a rise in ocean temperatures
worldwide in recent decades, there has not been a worldwide
increase in the number or intensity of tropical storms. Only the
Atlantic Ocean has had an increase, which Gray attributes to
natural cycles.
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