Hurricanes are very costly to human beings in terms of both loss of life and economic damages. If
it could be shown that greenhouse gas-induced warming would make the frequency or intensity of
these storms greater, it would seem only logical that this situation would give us one more reason
to reduce emissions of these gases into our atmosphere.
The authors of this article were concerned with analyzing how greenhouse gas-induced warming would affect hurricanes in the future. Previous research had indicated that tropical storms tend to form only in places where the sea surface temperature is more than 26 degrees C. Hence, it would seem likely that warming of the Earth’s surface would increase the number of hurricanes by increasing the number of warm areas where hurricanes could form. The researchers who wrote this article decided to use a climate model to determine the validity of this possible cause and effect relationship.
Their model was based on two previously developed models. The first model was developed for a previous climate change experiment. It was a coupled ocean-atmosphere model formed from a low-resolution atmospheric model coupled with a ocean model in a transient climate run. This model assumed an annual CO2 increase of approximately 1%, which lead to a doubling of the CO2 concentration in the atmosphere after about 60 years. The second model had been developed to simulate hurricane type vortices. When this model was used at high resolution, it did a very good job of simulating hurricane distributions for our current climate. The model used for this research was developed in the following way. The difference in the surface temperatures of the Earth from the beginning of the simulation until the CO2 concentration was doubled was taken as data from the first model. These temperature differences were added to the present climate initial temperature conditions for the second model. The new temperature distribution that resulted was used in a 5 year simulation run with the second model. The resulting distribution of hurricanes was compared to the original distribution that resulted from using the present climate’s temperature distribution. This comparison was used to analyze how an increase in CO2 concentrations could affect the intensity and frequency of hurricanes.
Despite the original premise that an increase in greenhouse gases would lead to an increase in the frequency of hurricanes, the model showed that the number of hurricanes would actually be reduced by greenhouse gas-induced warming. The model also showed that the intensity of these storms would generally remain about the same. The results of this modeling were assessed for statistical significance. The results were generally found to be within a 99% confidence limit, with the exception of some of the results for the individual ocean basins. Given the fact that the hurricane model did such a good job of predicting the hurricane distribution of the current atmosphere, it seems that these results probably have some validity. Also, a few other lower- resolution modeling simulations have shown some similar results in the past with certain parameters. The biggest problem with these results may be that the simulation was run for a short time (only 5 years) due to lack of computing power. Further insight could probably be gained by running the simulation longer.
Given the results of their modeling, the researchers proposed some different ideas for why the number of hurricanes might be reduced by global warming. In particular, the increase of CO2 in the atmosphere seems not to warm the temperature of the oceans to a great extent. The heat capacity of the oceans may play an important part in delaying the effects of global warming on the temperature of the oceans. Other possibilities include the effect of global warming on circulation patterns and various winds. Certain circulation patterns and winds are very important to the development of hurricanes. Changing these patterns may adversely affect hurricane formation.
Overall, this research seems to point out that it is very important to consider many factors when trying to determine how one change in the Earth’s atmosphere will affect other parts of the environment. Clearly, looking at just how the surface temperature change associated with global warming might affect hurricane development in the future does not paint a good picture of how hurricane development will change with this warming. Global warming may cause many other side effects, such as changing circulation patterns, which will in turn also affect hurricane formation. There are many positive and negative feedbacks to consider before the whole system and all the possible changes can be understood. Because it is so difficult, and perhaps impossible, for us to completely predict all that will change if the surface temperature of the Earth changes, the complexity of our atmosphere alone is perhaps a very compelling reason for us to be concerned with global warming.
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