Increase in Frequency of Intense Hurricanes due to Climate Variability in Latter 21st Century

Many recent models of climate change and weather events suggest that the frequency of tropical cyclones will decrease, but the intensity will increase alongside the upward trend in rising climate. The models, however, are flawed and unable to project hurricanes with an intensity rating of category 3 or higher. Bender et al. (2010) examined the future of global warming on Atlantic hurricanes, using a method of downscaling that allowed for a more realistic distributional projection of hurricane intensity. The model depicts a significant increase in frequency of category 4 and 5 storms in the latter half of the 21st century, with the number of storms doubling, although the overall frequency of tropical cyclones globally is expected to decrease. The results were similar in two different operational models, indicating a high degree of certainty in the findings. Such data are also dependent on the global climate models used for determining environmental conditions, so future studies should reexamine the findings using updated climate models as well as improved hurricane simulation models, if they exist.—Brian Nadler
Bender, M.A., Knutson, T.R., Tuleya, R.E., Sirutis, J.J., Vecchi, G.A., Garner, S.T., and Held, I.M. Modeled Impact of Anthropogenic Warming on the Frequency of Intense Atlantic Hurricanes. Science 237, 454 – 460.

Due to rising sea surface temperatures and a possible increase in hurricane activity in the Atlantic, concerns have been raised that a positive correlation between the two events might exist. There is a great deal of variation among studies, however, a large portion suggest an increase to some degree of hurricane intensity. These models were unable to simulate major hurricanes of category 3 or higher, translating to winds exceeding 50 m/s. Bender et al. improved the simulations of the hurricane intensities by downscaling the models from a previous study, and applying a similar method to two hurricane models that yielded similar results.
M.A. Bender and colleagues conducted the studies while at the National Oceanic and Atmospheric Administration and Geophysical Fluid Dynamics Laboratory (GFDL). Comparisons were made between observed and control storm counts from the GFDL, downscaled, and categorized from 1980 to 2007. The results were used in the storm averages for the two hurricane models used in the study. The results do not take into effect the mix of aerosol effects. The rescale of the hurricane model shows a growing trend in hurricane activity that, although not devastating at the present time, could pose a significant threat in the latter half of the 21st century. The largest increase of intense hurricane activity is projected to occur in the western Atlantic, which was demonstrated in three of the four models run.
The authors found a significant relationship between climate change and hurricane frequency. In the downscaled models, in 80 years the number of category 4 and 5 hurricanes increased by a cumulative 81%. The hurricane season is predicted to shorten, as well as there being a decrease in the number of hurricanes in other areas around the globe, such as in the Caribbean. The authors suspected the data might be slightly skewed to increase in the latter half of the data due to more capable hurricane monitoring tools being more readily available.
An increase in hurricane intensity due to climate change will have potentially enormous economic and global consequences. Being able to determine intensity and locations of increase in hurricane frequency,  we can further determine how climate change affects tropical storms, as well as provide incentive to  limit climate change and to plan ahead in areas that are often in the path of hurricanes and major tropical storms. 

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