Sunday, August 30, 2009

Global Warming: Tropical Storm Effects

The claim that global warming will cause more violent weather, including more violent ocean storms, has been used repeatedly to scare the public into supporting political action to stop global warming. The lack of substance to this claim has not deterred to prophets of global doom from trying to prove the opposite. And Michael Mann is one of them.

You may remember him as the scientist who was the lead author of a study resulting in the infamous “hockey stick” graph. This graph (included in the report of the Intergovernmental Panel on Climate Change) purported to show a dramatic rise in global temperature since 1900, compared to an essentially flat trend for many prior centuries. Supposedly, the earth was heating up in the past century because of industrial growth. But this work has been thoroughly discredited. It was the product of multiple inaccuracies from errors, omissions, obsolete data, and manipulations in “reconstructing” data, all of which was then processed through an invalid statistical procedure. (See our three-part series “Global Warming, Global Myth.”)

Chris Landsea, Science and Operations Officer at the National Oceanic and Atmospheric Administration's National Hurricane Center, was one of the peer reviewers to whom the journal Nature sent a copy of Mann's recent paper. In a subsequent letter to Mann, Landsea wrote “some very large concerns about the paper were not addressed....The first point is that the paper disregarded (and not even discussed) crucial new work by Vecchi and Knutson (Journal of Climate, 2008) and Landsea, Vecchi, Bengtsson and Knutson (Journal of Climate, 2009). The first paper showed that about 3-4 tropical storms per year were likely "missed" in the late 19th Century down to less than 1 per year by the 1960s. The second paper... shows that two-thirds of the massive doubling trend is simply due to very short-lived (< 2 days duration) tropical storms. Taking out these "shorties" (very likely due just to our vastly improved observational capabilities) from the record and adding in the estimated number of "missed" medium to long-lived tropical storms causes the long-term trend to completely disappear.

“Your paper starts with a premise that 'Atlantic TC [tropical cyclone] activity, as measured by annual storm counts, reached anomalous levels over the past decade', which is simply not correct based upon the new research...This isn't a small quibble: it's the difference between a massive trend with doubling in the last 100 years, versus no trend with only multidecadal variability remaining.”

Landsea's second major point is a more involved discussion of “merging of the paleo record with the historical all basin tropical storm counts.” We shall not go into that here, but you can view Landsea's complete letter at .

It contains a press release that quotes Mann's views, which are opposite to Landsea's: "It seems that the paleodata support the contention that greenhouse warming may increase the frequency of Atlantic tropical storms," said Mann. "It may not be just that the storms are stronger, but that there may be more of them as well."

Landsea concludes: “The bottom line is that the [Mann] paper comes to very erroneous conclusions because of using improper data and illogical techniques. In my opinion, this work is, unfortunately, a step backwards in helping climate researchers understand how hurricanes have changed over the last several centuries.”

Recall that Mann's “hockey stick” study included omitting data and utilizing invalid techniques, types of errors which are also evident in his latest paper. Evidently he hasn't learned from that previous experience, but maybe the rest of the world--including the news media--will learn not to pay any attention to him.

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