This morning I have been engaged in a Twitter debate with Jeff Sachs, of Columbia Earth Institute, motivated by his tweet as follows.
Jeffrey D. Sachs @JeffDSachs
“Increasing Intensity of the Strongest Tropical Cyclones,” published 2008, demonstrated that disasters like Haiyan becoming more common.
The reference is to a paper by Elsner et al. (2008) in Nature which shows an increase in the strongest tropical cyclones in some basins over the sub-climate time period of 1981-2005. Unfortunately for Sachs that paper does not show trends significant at the >90% level for the strongest cyclones in the western North Pacific basin (the world’s most active and where Haiyan occurred). The lesson here is that if you are going to pick cherries, make sure that the fruit is not a lemon.
Fortunately, there is a more relevant study (Weinkle et al. 2012, here in PDF) which looks specifically at landfalls in the western North Pacific basin. Landfalls are of course what cause disasters. The data from that paper for the major landfalling tropical cyclones (i.e., Category 3+) is shown at the top of this post. The trend line is added by Excel, and shows a decline. However, the western North Pacific basin has been shown to exhibit very large variability, so I wouldn’t put much weight into any claims of trends up or down (but don’t believe me, check IPCC). That said, recent research has looked at the recent decline in activity in that basin.
Given this data, substantial research on it and a strong IPCC consensus does anyone really want to debate that typhoon disasters have become more common?