As New Yorkers take to shelters from the heat emergency and Governor Schwarzenegger cuts his deal on carbon emissions with Prime Minister Blair, we found ourselves contemplating the latest issue of Science magazine. It has looked into what seems to be received as a given, that the big hurricanes are somehow tied to global warming. Four scientists, one from the National Hurricane Center, have finally thought to ask whether it’s even possible to track changes in the intensity of hurricanes over the decades and have concluded that the available data are too unreliable. Turns out many hurricanes have been violent all along. Only in the wacky world of global warming campaigning could that come as news.

Hurricanes are categorized based on the maximum sustained wind speed at surface level, which means at sea- or ground-level at the wall of the hurricane’s eye. Measuring that intensity is tricky. Airplanes flying through the storm can do the job, but planes can’t always make it to storms, especially when the hurricane is too far from land, and the planes don’t fly through constantly, meaning they might miss the period of greatest intensity. For about 30 years, scientists have been making estimates based on satellite images. However, the technique is subjective and accurate estimates depend on clear images.

As scientists have developed satellites capable of producing higher-resolution images and more such satellites have been launched, it has become easier to distinguish severe hurricanes from less serious storms. That does not mean, however, that the number of severe storms has been increasing.

The authors of the Science article have now reviewed available evidence of historical storms and concluded that imperfect technology led scientists to underestimate those hurricanes’ strengths. At least five storms in the North Indian Ocean between 1977 and 1989 were classed as relatively mild Category 3 storms at the time but were most likely severe storms. So it turns out that the frequency of severe storms in that area is no different now than it was 30 years ago.The authors of the article have found at least 70 storms worldwide between 1978 and 1990 that were actually severe but were thought at the time to be much weaker.

In respect of hurricanes and global warming, the New YorkTimes started editorializing on the connection last September. Yet level-headed observers have long recognized that what scientists don’t know about climate change is more extensive than what they do know. Now we also know that we don’t know as much as we thought we did about the effects of climate change.