Gabriel Vecchi

The potential threat from more frequent and stronger hurricanes is a favorite scare scenario of climate alarmists. They point to disasters like Hurricane Katrina as examples. However, such anecdotal evidence, while dramatic, says little about overall cyclonic activity. A greater document of documented storms does not necessarily mean that more storms have occurred, only that more have been recorded. As Gabriel Vecchi and Thomas Knutson of NOAA state:

Two recent papers (Vecchi and Knutson; and Landsea et al) suggest that, based on careful examination of the Atlantic tropical storm database (HURDAT) and on estimates of how many storms were likely missed in the past, it is likely that the increase in Atlantic tropical storm frequency in HURDAT since the late-1800s is primarily due to improved monitoring.

Vecchi and Knutson find this increase among moderate-duration storms (storms lasting longer than two days). Their adjustment for “missing” storms is shown in the chart above . They go on:

Existing records of past Atlantic tropical storm numbers (1878 to present) in fact do show a pronounced upward trend, correlated with rising SSTs (see Figs. 1 and 9 of Vecchi and Knutson 2008). However, the density of reporting ship traffic over the Atlantic was relatively sparse during the early decades of this record, such that if storms from the modern era (post 1965) had hypothetically occurred during those earlier decades, a substantial number would likely not have been directly observed by the ship-based “observing network of opportunity.” We find that, after adjusting for such an estimated number of missing storms, there is a small nominally positive upward trend in tropical storm occurrence from 1878-2006. But statistical tests reveal that this trend is so small, relative to the variability in the series, that it is not significantly distinguishable from zero (Figure 2). Thus the historical tropical storm count record does not provide compelling evidence for a greenhouse warming induced long-term increase.

As for greater economic losses from storms, there are simply more people living on the coasts than ever before, which means more buildings along the coasts than ever before.

For more on hurricanes, see the segment and comments on the topic from Marlo Lewis’s film, Policy Peril. (Thanks to Margaret Griffis for the tip.)