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Intense Tropical Cyclones in a Warming World
Chan, J.C.L. 2009. Thermodynamic control on the climate of intense tropical cyclones. Proceedings of the Royal Society A 465: 3011-3021.

Climate alarmists have long claimed that global warming will lead to the more frequent occurrence of stronger tropical cyclones, but this contention has not been proven to be correct. Consequently, yet another researcher has attempted to see what he could learn about the issue.

What was done
Focusing on five ocean basins - the Atlantic (1960-2007), the Western North Pacific (1960-2007), the Eastern North Pacific (1960-2007), the South Indian Ocean (1981-2007), and the South Pacific (1981-2007) - the author examined the relationship between the seasonally averaged maximum potential intensity (MPI, an index of thermodynamic forcing) over each basin where tropical cyclones (TCs) typically form and the seasonal frequency of occurrence of intense TCs.

What was learned
Chan determined that "only in the Atlantic does the MPI have a statistically significant relationship with the number of intense TCs, explaining about 40% of the [observed] variance," while "in other ocean basins, there is either no correlation or the correlation is not significant."

What it means
The People's Republic of China's researcher states that "even in the Atlantic, where a significant correlation between the thermodynamic [temperature related] factors and the frequency of intense TCs exists, it is not clear whether global warming will produce a net increase in such a frequency, because model projections suggest an increase in vertical wind shear associated with an increase in sea surface temperature," which phenomenon tends to work against intense TC development. Hence, he concludes that "it remains uncertain whether the frequency of occurrence of intense TCs will increase under a global warming scenario."

Reviewed 23 December 2009