As Hurricane Irma batters Florida, with Anguilla, Barbuda and Cuba clearing up and Houston drying out after Harvey, it is reasonable to ask whether such tropical cyclones are getting more frequent or fiercer.
The answer to the first question is easy: no. As the Intergovernmental Panel on Climate Change put it recently: “Current datasets indicate no significant observed trends in global tropical cyclone frequency over the past century.” The trend in numbers of major hurricanes making landfall in the United States has been slightly downward over the past century. Harvey and Irma have ended an unprecedented 12-year hurricane drought, in which not a single category 4 or 5 hurricane made American landfall. So whatever global warming is doing or will do, it is not so far increasing the frequency of such storms...
Let’s assume that there is a trend towards slightly fewer but slightly more intense hurricanes.
What does it mean for policy? Pause to notice one truly spectacular feature of Harvey and Irma: how few people they have killed so far. By stalling near the Texas coast, Harvey caused huge floods in HoustoN, not quite rivalling those of 1935 in the city but still devastating to many people. Yet they killed only about 60 people. Compare this relatively low number (given the huge population of Houston) with the 10,000 dead in Galveston in 1900, or the 138,000 who died in Cyclone Nargis in impoverished Burma in 2008.
What does it mean for policy? Pause to notice one truly spectacular feature of Harvey and Irma: how few people they have killed so far. By stalling near the Texas coast, Harvey caused huge floods in HoustoN, not quite rivalling those of 1935 in the city but still devastating to many people. Yet they killed only about 60 people. Compare this relatively low number (given the huge population of Houston) with the 10,000 dead in Galveston in 1900, or the 138,000 who died in Cyclone Nargis in impoverished Burma in 2008.
