November 21, 2008

Hurricane History Lessons

Filed under: Climate Extremes, Hurricanes

Here we go again – hurricane season has come to an end and yet another year has failed to produce the widespread pain and suffering that can reinforce the claim that the buildup of greenhouse gases is the root cause of all the damage. We have covered this topic dozens of times in the past, but the literature on the subject never seems to stop oozing right through the distortion of the greenhouse crusaders. We get tired of writing about this subject over and over and we suspect you see this as another in a very long line of essays on the topic…we feel each other’s pain. The hurricane story should have been destroyed a decade ago, but for whatever reason, the global warmers continue to insist that hurricanes are increasing in frequency, intensity, and/or duration and the blame should sit squarely on carbon dioxide emissions from the United States. If you want more on the subject, visit literally FIVE million websites on the subject!

One of many recent articles on this subject was produced by a pair of prolific scientists with the Department of Atmospheric Science at Colorado State University who “acknowledge funding provided by NSF Grant ATM-0346895 and by the Research Foundation of Lexington Insurance Company (a member of the American International Group).” Sounds like “Big Insurance” is involved here, so be aware! Of course, never mind that these guys also secured research dollars from the incredibly competitive National Science Foundation.

Klotzbach and Gray begin by noting “There has been a considerable increase in Atlantic basin tropical cyclone (TC) activity since 1995. Also, the very active seasons of 2004 and 2005 produced record amounts of damage in the United States. This increase in both Atlantic basin activity as a whole as well as U.S. landfalling activity had been anticipated by as early as the late 1980s. Considerable debate has ensued over the past few years as to the causes of this increase.” Once again, we wonder how a major professional scientific outlet like the Journal of Climate can allow anyone to suggest “Considerable debate” continues on anything related to global warming – isn’t the debate over?

Before any of you skeptics get into high gear, be aware that Klotzbach and Gray state “Regardless of global trends, there is a general consensus that Atlantic basin TC activity has increased dramatically since 1995, similar to amounts of activity observed from the late 1940s through the mid-1960s”. We see where this is going – hurricane activity has increased in the Atlantic since 1995, the activity is similar to what was observed in the past, and scientists were predicting this increase three decades ago before the global warming debate ever got off to first base.

The authors state that “Information on basin wide TC activity for the North Atlantic as well as U.S. landfalling TCs was calculated from the best-track dataset produced by the NHC from 1878 to 2006” (NHC = National Hurricane Center). In gathering hurricane data back to 1878, they note “There are likely considerable underestimates in the early portion of the best-track dataset.” Obviously, these underestimates in the early period would provide an illusion of an increase through time. However, Klotzback and Gray add “The U.S. landfalling tropical cyclone record should be quite good, especially since the start of the twentieth century, as the Gulf Coast and East Coast have been fairly densely populated since 1900.”

We could debate the quality of these datasets all day, so let’s see what this article adds to the debate (a debate still alive here at World Climate Report). The Table below shows the annualized number of Atlantic basin hurricanes, hurricane days, major hurricanes, and major hurricane days for periods from 1878 to 2006. The global warmers are rejoicing given the numbers for the 1995-2006 period – is Gore right?

Table 1. Observed annually averaged Atlantic basin hurricanes (H), hurricane days (HD), major hurricanes (MH), and major hurricane days (MHD) during the multidecadal periods of 1878–99, 1900–25, 1926–69, 1970–94, and 1995–2006 (from Klotzbach and Gray, 2008)

Don’t look now, but Klotzbach and Gray have an answer, and it involves the Atlantic Multidecadal Oscillation (AMO), which is like an El Niño – La Niña oscillation in the North Atlantic – as seen In Figure 1, the AMO seems rather important in dictating hurricane activity in the Atlantic. The authors inconveniently note regarding major hurricanes (MH) “When the AMO is in its positive phase, TC activity in the Atlantic basin is heightened, especially for MH activity. Landfalling hurricanes along the U.S. coastline also become more frequent, with the most dramatic increases in a positive AMO phase being seen for the U.S. East Coast and the Florida Peninsula.”

Figure 1. Annually averaged Atlantic basin H, HD, MH, and MHD for the top 20 AMO years (blue bar) and the bottom 20 AMO years (red bar)(from Klotzbach and Gray, 2008)

Before any claim can be made that the 1995 to near-present period is all that unusual, the pair notes “This dramatic multidecadal landfall variability is even more pronounced when considering MH landfalls along the Florida Peninsula. During the 33-yr period from 1933 to 1965, 11 MH made landfall, while during the following 38-yr period (1966–2003), only one MH made landfall (Hurricane Andrew in 1992).” So much of a great increase in hurricane activity thanks to the buildup of greenhouse gases!

Klotzbach and Gray are seasoned players, and they end with the sentence “Additional research involving potential physical drivers of the AMO should be conducted.” Send your millions of tax dollars to World Climate Report, and we’ll look into it?

The bottom line is that claims that hurricanes are increasing due to global warming are questionable, if not laughable given the enormous amount of evidence that at the very least suggests this is a very complex question.


Klotzbach, P.J. and W.M. Gray. 2008. Multidecadal variability in North Atlantic tropical cyclone activity. Journal of Climate, 21, 3929-3935.

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