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PDI, Power Dissipation Index; w.r.t., with respect to. Contributions of the observed typhoon case number (N), duration () and intensity (I) to the western North Pacific annual PDI, based on the method from Emanuel 2007 ref. 18. The top 4 rows are changes in each pentad w.r.t. the long-term mean (1993–2012). The last row is the change in the most-recent pentad (2008–2012) w.r.t. the 1st pentad in the early 1990s (1993–1997).