Future trends in Atlantic storms may not mirror the patterns of recent decades.NASA / Univ. Wisconsin-MadisonHurricanes may become rarer in the Atlantic throughout the 21st century if the world continues to warm, suggests a new study.
The research is the latest to address the question of how — and whether — global warming will affect the intensity and frequency of hurricanes.
Globally, the number of major hurricanes has shot up by 75% since 1970. And although rising ocean temperatures are generally accepted as the key culprit — hurricanes can only form where sea surface temperatures exceed 26ºC — the link to global warming has remained a contentious issue.
In the new study, published today in Nature Geoscience 1, Thomas Knutson of the US National Oceanic and Atmospheric Administration (NOAA) and colleagues used a regional climate model of the Atlantic basin to simulate the observed increase in hurricane activity between 1980 and 2006, on the basis of observed sea-surface temperatures and atmospheric conditions.
“The study does not support the notion that rising greenhouse gases are causing an increase in tropical storm frequency,” says Knutson.
Storm warning
They then used two versions of the model, one assuming climate warming of 2.8ºC by 2100, and one without warming, to estimate whether hurricane activity will continue to increase in the region as a result of human-induced climate change.
Overall, the number of hurricanes will decrease, with weaker storms feeling the greatest impacts. Knutson and his team predict a 27% drop in tropical storms, 18% fewer hurricanes and 8% fewer 'major hurricanes'.
“We can’t simply extrapolate the trend from the last 25 years into the future.”
Isaac Held
NOAA
So, despite the fact that hurricane activity has increased dramatically in the Atlantic over the past 25 years, this trend will not continue until the end of the century under warmer conditions. “We can’t simply extrapolate the trend from the past 25 years into the future,” says co-author Issac Held, also at NOAA.
The study focused primarily on changes in the number of hurricanes, but also projected a shift towards more intense storms and heavier rainfall events. This largely concurs with recent work by Kerry Emanuel, a hurricane expert at the Massachusetts Institute of Technology in Cambridge. Using a different type of model, Emanuel projected that global warming will result in fewer hurricanes globally, but that they will become more intense in some locations.
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Size matters
Kevin Trenberth, a climatologist at the National Center for Atmospheric Research in Boulder, Colorado, who was not involved in the study, agrees to an extent with the findings. “The results suggest fewer tropical storms in the Atlantic, and this seems reasonable given everything else we know”.
But he cautions that the authors may have underestimated increases in hurricanes and really severe storms, owing to the fact that their model was fairly low-resolution and could not account for changes in some of the largest of these events.
“In this business it is not the numbers that matter, it is also the intensity, duration and size,” he says.
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References
- et al. Nature Geosci. doi:10.1038/ngeo202 (2008).
Well I guess if mother nature isn't going to cooperate with Al Gore and the global warming scam you just have to write some new computer models to get the results you want. Clearly, global warming is anthropogenic (man-made). It exists mainly in the human mind and is manufactured from two sources – careless data acquisition and dubious data processing.
Sounds logical. Higher temperature will cause ice to melt. This relative cold water will decrease the temperature of the seawater. Thereby decreasing the the prerequisite for hurricans for the next 25 to 50 years.
Seems to me that the global warming folks were all worked up a couple of years ago because global warming would increase the number of hurricanes along with their strengh. Now all of a sudden we have a study that states the number of hurrices will decrease. The story about tempuratures is the same as the story about hurricanes. I think its time the glboal warming crowd come clean and just admit, they haven't a clue.
Uncertainties in weather forecasting are normal. Still, broad facts like disappearing arctic ice and glaciers are pretty well established. Since water vapor (the number one greenhouse gas) is rare in cold places, the higher CO2 has a bigger impact in high mountain and polar regions. That's what we'd expect- and what we observe- case closed. Any reasonable person expects future rising sea levels, while other changes, such as shutdown of the mid-Atlantic current and subsequent frigid European climate, are reasonable projections but somewhat speculative until they happen. It's like waiting for a 2 pack a day smoker with chronic cough to develop new health problems.