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A Combined Observational History- and Model-Based Projection of Western North Pacific Tropical Cyclones
Li, Y., Wang, X., Yu, R. and Qin, Z. 2007. Analysis and prognosis of tropical cyclone genesis over the western North Pacific on the background of global warming. Acta Oceanologica Sinica 26: 23-34.

What was done
Noting that "it is controversial whether climate models are able to be used to simulate the tropical cyclone's activities directly [our italics]," the authors analyzed real-world tropical cyclone data pertaining to the western North Pacific basin archived in the Yearbook of Typhoon published by the China Meteorological Administration for the period 1949-2003, together with contemporaneous atmospheric information obtained from the National Center for Environmental Protection reanalysis dataset for the period 1951-2003. Following this endeavor, they used their empirical findings to infer future tropical cyclone activity in the region based upon climate-model simulations of the state of the general circulation of the atmosphere over the next half-century.

What was learned
Li et al. report there were "more tropical cyclones generated over the western North Pacific from the early 1950s to the early 1970s in the 20th century and less tropical cyclones from the mid-1970s to the present." They further found that "the decadal changes of tropical cyclone activities are closely related to the decadal changes of atmospheric general circulation in the troposphere, which provide favorable or unfavorable conditions for the formation of tropical cyclones." Based on simulations of future occurrences of these favorable and unfavorable conditions derived from "a coupled climate model under the [A2 and B2] schemes of the Intergovernmental Panel on Climate Change special report on emission scenarios," they then determined that "the general circulation of the atmosphere would become unfavorable for the formation of tropical cyclones as a whole and the frequency of tropical cyclone formation would likely decrease by 5% within the next half century, although more tropical cyclones would appear during a short period of it."

What it means
The Chinese researchers' analysis provides further evidence for the decadal cycling of tropical cyclone activity, its potential imminent enhancement, and its possible longer-term (50-year) slight decline, all of which seems rather reasonable.

Reviewed 17 October 2007