Researchers predict a less stormy Atlantic on the horizon

For countries lying around the edge of the Atlantic Ocean, the coming century may be less stormy than expected, according to a new study. A team of researchers has created a model to forecast the frequency of Atlantic hurricanes and tropical storms, and predicted that they are likely to decrease during the 21st century as temperatures increase with climate change.

Atlantic hurricane frequency, over the past fifty years, has been strongly correlated with increasing sea surface temperature. As the Atlantic is predicted to warm throughout the 21st century due to continued carbon dioxide emissions, the assumption has been that the regularity of such storms would increase. However, new research has projected fewer tropical storms (21 per cent less) and hurricanes (18 per cent less) by the late 21st century. However, the storms that do occur are predicted to have higher wind speeds and greater rainfall rates.

The researchers developed a model to simulate hurricane activity in response to various environmental conditions. To simulate hurricanes in response to climate change, they used temperature and other atmospheric projections from a number of global climate change models developed by the World Climate Research Program. A projection for late 21st century hurricane activity was then generated. Under the warmer climate conditions in the model, fewer storms were simulated compared with present day conditions. However, the projection was not entirely positive. The model also projected a slight increase in the intensity of storms as well as the number of the most intense storms. A significant increase in rainfall rate was also associated with the storms.

The team tested the new model against conditions from 1980-2006, and showed that its simulations matched the incidence of actual hurricanes over that period very accurately. For those tests, the model used data on past changes in sea surface temperatures and large-scale atmospheric conditions.

The future projections also reinforced previous research that says areas at high risk of hurricanes and tropical storms are not likely to change dramatically. The storms form when the sea surface reaches a certain temperature, relative to the surrounding environment. However, because the warming associated with climate change will be relatively uniform, this threshold temperature will also increase as the sea surface warms. Therefore storms are likely to stay confined to the tropical region, where they are presently most common.

These new projections do not conflict with the accepted premise that tropical storms and hurricanes are strongly influenced by sea surface temperature. The increase in the frequency of storms in the Atlantic over recent decades can be explained by the fact that the North Atlantic Ocean has warmed much faster than other areas.

However, the authors warn that their model is a work in progress and needs some refinement using improved climate models. For example, they found it had a tendency to predict hurricanes and tropical storms that were less severe than those that actually occurred.