Stormy weather

Stormy weather

Bjørn Lomborg in his book The Skeptical Environmentalist repeatedly makes the claim that environmentalists are promoting what he calls the Litany, and overemphasising "gloom and doom." Here he criticizes a statement from Our Angry Earth, a book by Isaac Asimov and Frederik Pohl (pages 8-9):

Isaac Asimov, worrying about more hurricanes from global warming (something we will look into in Part V) cites some seemingly worrying statistics: "The twenty-three years from 1947 to 1969 averaged about 8.5 days of very violent Atlantic hurricanes, while in the period from 1970 to 1987 that dropped by three-quarters, to only 2.1 days per year ...and in 1988-1989 rose again to 9.4 days a year." [page 45] This seems threatening. Now the hurricane rate is higher than ever. But notice the time-spans: 23 years, 17 years, and then just two years at the end. Maybe the two years have been singled out just because they can be made spectacular? Well, at least the two years immediately preceding have 0 and 0.6 violent Atlantic hurricane days. And yes, the two years just after had only 1 and 1.2 days. [Landsea 1993] Documenting these trends, the original researcher points out that Atlantic violent hurricane days "show a substantial decrease in activity with time." [Landsea 1993] Since then, only hurricane days have been documented, and they too show a decline of 1.63 days/decade. [Landsea et al. 1999 page 108]

When we look at Lomborg's statement in detail, a number of problems and errors stand out.

Isaac Asimov,

The book was written by Asimov and Frederik Pohl, not just Asimov. While this is a minor error, there are numerous minor errors in the book which show a carelessness with the facts. It is also not clear how a book written by two men known primarily as authors of science fiction is representative of the environmental movement.

worrying about more hurricanes from global warming

In fact, the authors note that the number of hurricanes stays relatively constant. They were worried about the severity of hurricanes.

(something we will look into in Part V) cites some seemingly worrying statistics: "The twenty-three years from 1947 to 1969 averaged about 8.5 days of very violent Atlantic hurricanes, while in the period from 1970 to 1987 that dropped by three-quarters, to only 2.1 days per year ...and in 1988-1989 rose again to 9.4 days a year." [page 45] This seems threatening. Now the hurricane rate is higher than ever.

Lomborg simply misses the whole point of the paragraph. which is that hurricanes appear to run in cycles. To put the paragraph in context I have included the paragraph preceding it, and also part of the one following it. (page 45, an obvious repeat has been left out.):

These Atlantic hurricanes do terrible damage, particularly to the barrier islands and coastlines of the United States from Florida north. Will the damage increase?
It looks that way for two reasons. First, there appears to be a cycle of hurricane violence, with a period of fifteen to twenty-five years. Studies just published by William Gray at Colorado State University showed that, although the total number of hurricanes is fairly steady year after year, the number of the most damaging storms is not. The twenty-three years from 1947 to 1969 averaged about 8.5 days of very violent Atlantic hurricanes, while in the period from 1970 to 1987 that dropped by three-quarters, to only 2.1 days per year ...and in 1988-1989 rose again to 9.4 days a year.
That suggests that the Atlantic is now entering another period of a couple of decades of violent storms, which the global warming can only make worse. All the strength and destructive power of hurricanes come directly from the warmth of the oceans where they develop, and one scientist has predicted that the global warming may produce future hurricanes as much as 25% stronger than those of the recent past.

But notice the time-spans: 23 years, 17 years, and then just two years at the end. Maybe the two years have been singled out just because they can be made spectacular?

If we check Lomborg's notes (page 354) we find that Our Angry Earth was published in 1991. The two years were not "singled out" because they were "spectacular" but because they were the the most recent data when the book was published.

Well, at least the two years immediately preceding have 0 and 0.6 violent Atlantic hurricane days. And yes, the two years just after had only 1 and 1.2 days. [Landsea 1993] Documenting these trends, the original researcher points out that Atlantic violent hurricane days "show a substantial decrease in activity with time." [Landsea 1993] Since then, only hurricane days have been documented, and they too show a decline of 1.63 days/decade. [Landsea et al. 1999 page 108]

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References

Asimov, I. and F. Pohl, Our Angry Earth, Tom Doherty Associates, 1991

Landsea, C. W. 1993 "A climatology of intense (or major) Atlantic hurricanes" Monthly Weather Review121 pages 703-13

Landsea et al. 1999 "Atlantic basin hurricanes: indices of climate changes" Climatic Change 42 pages 89-129

Written by Jim Norton