The Oil Drum

While this is quite a serious issue, there are a few amusing points. Firstly, this study does present some awkward reading for some who hold that natural cyclical changes in the thermohaline circulation (rather than, say, anthropogenic influences), are responsible for the anomalous increase in Atlantic Hurricane activity in recent decades. Hurricane prognosticator William Gray (whose public statements we have commented on previously), has, in his recent senate testimony, confidently asserted that a putative increase in the intensity of the Atlantic Thermohaline circulation over recent decades was entirely responsible for this increase:

[quoting Gray here]
The Atlantic has large multi-decadal variations in major (category 3-4-5) hurricane activity. These variations are observed to result from multi-decadal variations in the North Atlantic Thermohaline Circulation (THC) - Fig. 4. When the THC is strong, it causes the North Atlantic to have warm or positive Sea Surface Temperature Anomalies (SSTA) and when the THC is weak, cold SSTAs prevail. Figure 5 shows these North Atlantic SSTAs over the last century with a projection for the next 15 years.
[end quote]

By Gray's very clearly articulated reasoning, there should have been a downturn, not the observed upturn in major Atlantic hurricane activity over the past several decades (in the absence of other---including anthropogenic--influences on tropical Atlantic climate) if Bryden et al.'s results are correct. It will be interesting to see if Gray, and others, will change their line of argument in the face of this new study. Today, the last day of the official 2005 Atlantic Hurricane season, might be a fitting opportunity for them to do so.