Is the Tropical Cyclone Data Adequate to Assess Multi-decadal Trends in Intensity?

A July 28 2006 Science Perspective article entitled “Can We Detect Trends in Extreme Tropical Cyclones?” (subscription required) by Christopher W. Landsea, Bruce A. Harper, Karl Hoarau and John A. Knaff has appeared. It raises the very real issue of the temporal homogeneity of the hurricane intensity data.

Among their findings,

“the 1970 Bangladesh cyclone—the world’s worst tropical-cyclone disaster, with 300,000 to 500,000 people killed—does not even have an official intensity estimate, despite indications that it was extremely intense.”

This is a remarkable finding. It not only supports the Landsea et al conclusions on the change of intensity assessments over time, but that in terms of what actually matters to people, this tropical cyclone, regardless of its intensity, caused a massive loss of life. The reduction of this loss should be a priority. Clearly changes in energy policy, such as CO2 reduction, will have much less of an impact on future loss of life, than improved plans to reduce the vulnerability of the local population to this risk (e.g. see).

Also, during the early 1970s, I had the privilege to work in the same building in Coral Gables, Florida as the National Hurricane Center. The Directors at this time, Dr. Robert H. Simpson and Neal Frank had the vision to permit the other researchers in the NOAA center (including me) to observe the hurricane specialists as they prepared their forecasts. Except during an immediate landfall event, we had unfettered access. The availability of satellite and reconnaissance aircraft to assess intensity even in the Atlantic tropical cyclone basin was notably different than what became available later. Thus the Landsea et al report resonates with my experience with the changes over time in the intensity data even in the Atlantic basin.

In my books on hurricanes,

Pielke, R.A., Jr. and R.A. Pielke, Sr., 1997: Hurricanes: Their nature and impacts on society. John Wiley and Sons, England, 279 pp.

Pielke, R.A., 1990: The hurricane. Routledge Press, London, England, 228 pp.

the reduction of the loss of life in the USA during the 2oth century is documented. This reduction can be credited both to improved construction and coastal planning (such as hurricane evacuation routes), and, to the significant advances in hurricane track forecasting by the National Hurricane Center.

The allocation of research funds to the reduction of societal risk to hurricanes, including the further improvement of hurricane track and intensity forecasting for individual storms, as well as effective coastal planning, should be high priorities. Large spending on multi-decadal hurricane intensity forecasts, relative to these other issues in tropical cyclone research, is a poor choice to provide benefit to society.

As shown on the Climate Science weblog, these multi-decadal global climate forecast models have shown no skill on the regional scale (e.g. see). The recent papers that claim to find a trend in hurricane intensity have no basis with respect to the multi-decadal global model predictions. The Landsea et al paper indicates that the the conjecture of a strong human influence on trends in hurricane intensity are based on temporally inhomogeneous observational data.

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