Al Gore’s An Inconvenient Truth did a lot of good for the awareness of environment, but in so doing it also created a few misconceptions. Probably the largest was the link between hurricanes and a warming planet, a link that Gore made clear when he tied Hurricane Katrina to global warming.
In reality, climatologists and scientists alike are all unanimous in reiterating their number one rule; single events do not prove anything.
However single events aside, it has appeared that over the past decades hurricanes in the North Atlantic have been growing stronger and more frequent. The majority of researchers agree that since the 1950’s hurricanes have increased over the Atlantic and since the 80’s they have subsequently become stronger.
Those attempting to link global warming to hurricanes via the increase in ocean surface temperature – a key factor in hurricanes – have failed to explain, however, why this seems only to be occurring in the North Atlantic, and not in any other ocean basins.
Now, a new study by way of Tom Knutson and colleagues at the US National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory in Princeton, US, has turned conventional theory on its head.
Knutson built a computer model to simulate the formation of storms and hurricanes in the North Atlantic, based on sea-surface temperatures and atmospheric conditions from the past 25 years. The model followed pretty closely the patterns observed over the time period the information had been gathered from, predicting 162 storms as opposed to the official 143 recorded.
However when it came time to plugging in predictions of how the surface temperature will rise, the model simulated fewer tropical storms and fewer hurricanes. By 2100 the computer model predicted that the Atlantic would see a drop of 27% in tropical storms and a drop of 18% in hurricanes.
“This study does not support the idea there is a large increasing trend [in hurricanes] due to greenhouse warming,” says Knutson.
The model also predicted that in the fewer hurricanes that do emerge, their intensity will increase on average. But Knutson is suitably cautions about his findings. “We don’t want to take it quantitatively too seriously because it’s not simulating stronger storms very well,” he says. Nonetheless, he adds, “it gives more support to the idea that in the tropics in general, hurricanes will be slightly more intense and have more rainfall.”
A rather large flaw however has emerged in the findings, which has led many to have major issues with Knutson’s findings. In the predicted 162 storms and in storms for the future century, not a single one was categorized over 3. When considering that we have seen many very strong storms lash the Atlantic these past decades, it seems hard to take the rest of Knutson’s work with any validity.
Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colorado, US, describes this as “a major shortcoming.” “In this study there is a suggestion that the strongest storms increase, but the model never simulates them in the first place,” Trenberth says. “It could be grossly in error for the strongest storms, which are the ones that do most damage.”
Image: view of the eyewall of Hurricane Katrina taken on Aug. 28, 2005, as seen from a NOAA P-3 hurricane hunter aircraft before the storm made landfall on the United States Gulf Coast. (Source: NOAA) via Flickr