HURRICANES: GLOBAL WARMING HAS NOTHING TO DO WITH IT
By James O'Brien
There is some disagreement among climate scientists on the potential impact of
global climate change on future hurricanes in the Atlantic Ocean. Last year,
claims were made that the frequency of hurricanes will increase due to global
climate change.
For example, after Hurricane Bonnie, Charley and Frances hit Florida in 2004,
the prime minister of England (sic), Tony Blair, and many other prominent
American scientists told the world that the hurricanes were due to global
warming.
Luckily scientists who actually regularly study hurricanes quickly responded
with the facts, and, for once, the misinformation was curbed quickly and
effectively.
But now the alarmists are at it again, claiming that global warming will
increase the intensity of hurricanes. Don't worry, readers; there is absolutely
no scientific support or correlation of hurricane intensity or hurricane
frequency with global warming.
Hurricane scientists and experts actually believe that variations in the
Atlantic Ocean Conveyer, not global temperatures, determine the frequency of
hurricanes. It is predicted that we will see an increase in the number of
Atlantic hurricanes for the next 10-15 years compared to recent years. This is
nothing new -- the last peak occurred between 1930 and 1970.
What is the Atlantic Ocean Conveyer and why does it affect hurricanes?
In the North Atlantic in the Labrador and Gin Sea, water is cooled and sinks to
the bottom in winter. The sinking water is replaced by warm Gulf Stream water
that leaves the North Carolina coast and proceeds toward the Northeast to
Ireland and Norway. The Gulf Stream draws water from the South Atlantic. The
rest of the conveyer belt is in the other oceans, but the Atlantic portion is
the dominant feature.
This oceanic phenomenon varies and changes the sea-surface temperatures. When
it is strong -- 1930-1970; 1995-2000-now -- there are more Atlantic hurricanes.
When it is weak -- 1905-1925; 1975-1994 -- the hurricane season is mild.
And what about intensity?
Hurricanes have to keep moving or they die by upwelling the cold water below
the warmer sea-surface temperatures. Hurricane Mitch, 1998, is a textbook
example of this. Mitch stalled off Honduras when it lost its upper atmospheric
steering currents. This caused it to die and drop over 6 feet of rain on the
poor folks in Honduras and Nicaragua!
A hurricane will also grow stronger as it moves over water warmer than 80
degrees F (26.5 C). This is why some people believe that global warming will
increase hurricane intensity, but there are no scientific calculations that
show the areas of water this warm increasing in size.
However, if one graphs the ocean environment for Category 3, 4 and 5 storms,
there is no difference in ocean-surface temperatures for tropical storms and
Category 1 and 2 storms. What's more, the scientific literature documents that
the western Atlantic off Africa is the prime breeding ground for the stronger
storms -- and many of those stronger storms never make it to landfall.
While it is tempting to blame the frequency or intensity of hurricanes on man,
we all must remember how variable nature is -- and specifically in this case,
the effect of natural variations on hurricanes' intensity and frequency is
extremely higher than the possibility of man's interference.
Dr. James O'Brien is the Florida state climatologist and a professor of
meteorology and oceanography at Florida State University in Tallahassee.