A group of meteorologists says global warming probably isn't responsible for an apparent dramatic increase in the strength of extreme storms during the past few decades. The group says that, until 1990, even the best satellite data tended to underestimate the wind speed of storms.
While weather experts agree on many things — that global warming is real, for instance; or that ocean temperatures are rising. And they agree that warmer oceans allow for more intense hurricanes.
But they disagree about whether global warming has produced a measurable change in the intensity of these storms. Some raw numbers suggest it has. For example, they show that the frequency of extreme storms — Category 4 or 5 — has doubled worldwide since the 1970s.
But Chris Landsea of the National Hurricane Center says those raw numbers may be misleading.
"The concern is that the data is so unreliable," Landsea says, "that this doubling in the number of category fours and fives may just be an artifact of monitoring things better."
Landsea says the problem is that before about 1990, satellite images were far less precise. And so were the techniques to analyze them.
Landsea led a team that reviewed satellite images of storms in the North Indian Ocean during the past 30 years.
Things may become clearer after a team at the University of Wisconsin re-analyzes satellite data from the 1980s. That result is a year or more away.
In the meantime, weather experts on both sides of the global warming debate have issued a joint statement. It says that whether or not global warming is a factor, the immediate question is this: What to do about the millions of people who have moved to vulnerable coasts?