With 2005 shaping up to become the worst hurricane season in U.S. history,
scientists are speculating if global warming is a factor behind the explosion of
deadly storms.
Scientists generally agree that burning fossil fuels – coal, gas and oil – has
contributed to global warming. Global temperatures have risen by about 1 degree
F in the last half-century, and is even more evident in the arctic where
temperatures have risen by as much as 7 degrees F.
While no conclusive research has drawn a decisive link between global warming
and the increase in hurricanes, warming ocean temperatures may improve
conditions for hurricane formation.
David Phillips, an Order of Canada recipient and senior climatologist with
Environment Canada, likens nature’s formation of hurricanes to making a soufflé.
“Everything must come together in a perfect way or you have a failure.”
A hurricane is baked over the ocean, and like a delicate soufflé, there cannot
be any disturbances in its formation process. If there is a snap of cold air, it
will break the hurricane.
Hurricanes form when powerful thunderstorms blow over large pools of warm water
at the surface of the ocean. As the warm air rises, trade winds blowing in
opposite directions cause the storm to begin rotating. As more warm air from the
ocean rises through the chimney—also referred to as the eye—of the storm, cold
air is drawn in from above. Every year there are hundreds of thunderstorms
brewing over the Atlantic, yet only about 6 form into full-blown hurricanes
annually.
Like any good baker, when the ingredients are there, nature likes to make
hurricanes in bulk. Hurricanes tend to come in 30 year cycles. From the 1930s to
the 1960s, the Southeastern coast of the United States was hit by waves of
hurricanes. The 70s through 90s was a relatively quiet period for
hurricanes—thanks partially to El Nino winds that shear the tops off of the
hurricane chimney. In the last decade, climate experts generally agree that the
frequency, intensity and precipitation rates of hurricanes have increased
dramatically.
For example, of the ten costliest hurricanes to strike the United States, five
of them have occurred since 2004.
In a recent article published in the journal Nature, it was reported that the
intensity and duration of hurricanes has increased by 50 percent since the
1970s. Although some experts argue that this is part of earth’s natural cycles,
the article suggests there may be a link between global warming and hurricane
formation, pointing out that in the same period since the 1970s, global
temperatures have been rising along with carbon-dioxide emissions—a powerful
greenhouse gas that contributes to global warming.
Some scientists believe that global warming may contribute to a gradual increase
in ocean temperatures, and warm oceans waters is exactly what hurricanes need to
form.
Phillips, however, is not so quick to draw a link between rising global
temperatures and this year’s unusually active hurricane season.
“Hundred years ago people blamed an increase in tornadoes on trains and steam
coming out of locomotives. Then, it became radio antennas… It is somewhat
comforting to think that it is the result of human activities and we can somehow
control it.”
And although Katrina appears on track to be the costliest natural disaster ever
in the United States, it was not the most powerful. In the hours before it hit
land, it dropped down from a class 5 to a class 4 Hurricane. Hurricane Andrew
(1992) was the most recent class five, preceded by Camille (1969) and an unnamed
storm that hit Florida in 1935.
What made Katrina especially costly was the fact that it struck heavily
populated areas. Had it struck several decades ago, when coastal Louisiana and
Mississippi were still covered in swampy wetlands—which serve as natural buffers
to storms—the effects would not have been so catastrophic.
Phillips points out that one third of the world’s population lives within 100 km
of the ocean – thirteen of the eighteen ‘mega cities’ in the world are by the
sea. When that concentration of humanity is faced with rising sea levels (caused
in part by global warming melting arctic snow and ice), the potential for
flooding disasters goes up.
The New Orleans disaster was not hard to see coming. Mark Fischetti veritably
predicted it in his 2001 Scientific America article, “Drowning in New Orleans.”
"New Orleans is a disaster waiting to happen. The city lies below sea level, in
a bowl bordered by levees that fend off Lake Pontchartrain to the north and
Mississippi River to the south and west. And because of a damning confluence of
factors the city is sinking further, putting it at an increasing flood risk
after even minor storms. The low-lying Mississippi Delta, which buffers the city
from the gulf, is also rapidly disappearing. A year from now another 25 to 30
square miles delta marsh-an area the size of Manhattan-will has vanished. An
acre disappears every 24 minutes. Each loss gives a storm surge a clearer path
to wash over the delta and pour into the bowl, trapping one million people
inside and another million in surrounding communities."
Although the jury is still out on whether or not global warming is strengthening
hurricanes, with sea levels on the rise and no sign that humans intend to seek
refuge further inland, we can bet the worst is yet to come.