Global Warming and Hurricanes
January 23rd, 2006It is very irritating as an Atmospheric Scientist to watch newscasts. Global warming is blamed for everything from the shrinking of the Pika’s habitat to the recent increased hurricane activity. Granted, industrialization has and will continue to cause changes in the world’s atmosphere. The question is whether every change is related to industrialization or the natural long-term cycle of warming and cooling of the earth. Some changes are related; the ozone hole over the poles, increased carbon dioxide levels in the troposphere. Some changes are not, in my opinion, related. One of these is the increased hurricane activity over the past two years.
The increased hurricane activity is related to the natural cycle of the earth. Hurricane paths and formation are correlated to the location of upper tropospheric systems in the tropics. For a tropical depression to form, ideal conditions are required. Very limited vertical wind shear and warm ocean temperatures are two of these conditions. Vertical wind shear is defined as the difference in wind direction and speed as you go from the surface up into the atmosphere. For instance, if you have winds coming from the east at the surface and winds from the west above the surface, you are in a sheared environment.
Where do you find limited amounts of vertical wind shear? It is highly dependant on the locations of the upper tropospheric high and low pressure systems over the Atlantic Ocean. If there is a pattern that moves the upper level high pressure over 500 miles west, then (theoretically) you will move the ideal formation zone for hurricanes 500 miles west. So that helps to explain one aspect of the recent hurricanes; the tracks.
Now for the increased number. The Director of the National Hurricane Center, Max Mayfield, says it better than I can:
“The increased activity since 1995 is due to natural fluctuations (and) cycles of hurricane activity driven by the Atlantic Ocean itself along with the atmosphere above it and not enhanced substantially by global warming.” This was part of Max Mayfield’s testimony in front of Congress.
Basically it boils down to this. We have had satellite technology since roughly the 1960s. That’s 40 years of observing the weather over the oceans (where hurricanes come from). The natural cycles of the earth operate on much more than 40 year cycles. Prior to satellite technology, reports of hurricanes relied upon ships intersecting the storms, surviving through them to get the report out, and accurately relaying the information. We have very little data on hurricanes, their frequency and intensity prior to 1960.
It may seem like we are suddenly being besieged by hurricanes, but in reality we are observing a natural cycle.