Background
The authors note that "the question of whether and to what extent global warming may be changing tropical cyclone (TC) activity is of great interest to decision makers."

What was done
In a study designed to explore this important question, Grossmann and Morgan of Carnegie Mellon University's (CMU's) Department of Engineering and Public Policy -- in a study supported by the Climate Decision Making Center that was created through a cooperative agreement between the U.S. National Science Foundation and CMU -- review the scientific literature related to the possible effects of climate-model projected consequences of continued atmospheric greenhouse gas enrichment on TC frequency and intensity.

What was learned
The two researchers report that "while Atlantic TCs have recently become more intense, evidence for changes in other basins is not persuasive, and changes in the Atlantic cannot be clearly attributed to either natural variability or climate change." More specifically, they say that "the presence of a possible climate change signal in TC activity is difficult to detect because inter-annual variability necessitates analysis over longer time periods than available data allow," and that "projections of future TC activity are hindered by computational limitations and uncertainties about changes in regional climate, large-scale patterns, and TC response."

What it means
Concluding that "scientific uncertainty about whether and how climate change will affect TCs in the future may not be resolved for decades," Grossmann and Morgan go on to suggest that even if climate change "does not result in any significant increase in the intensity or frequency of future tropical cyclones" nor "lead to significant sea-level rise," human vulnerability in areas prone to land-falling hurricanes "will likely continue to increase significantly due to the continuing growth of populations and capital stock in high risk areas," citing Pielke et al. (2008). Thus, they say it would be wise "to induce greater protective action," stating that "there is a need to act now to reducing the existing high vulnerability to these storms," which will continue to constitute a real and present danger to people and infrastructure in coastal areas whether or not the frequency and degree of that danger increases or decreases, as it takes only one severe TC to lay waste to the works of man and snuff out the lives of many.

Reference
Pielke Jr., R.A., Gratz, J., Landsea, C.W., Collins, D., Saunders, M.A. and Musulin, R. 2008. Normalized hurricane damage in the United States: 1900-2005. Natural Hazards Review 9: 29-42.