July 9, 2013
Climate Changes Could Increase Hurricane Frequency This Century
Brett Smith for redOrbit.com - Your Universe Online
Using a unique combination of computer models, MIT atmospheric scientist Kerry Emanuel has made the contested prediction the 21st century will see an uptick in the number of hurricanes and tropical storms as a result of the forces of climate change."Studies using the same technique applied to the previous generation of global climate models showed very little change in global frequency, but an increase in intensity," Emanuel told Doyle Rice of USA Today. "Our study suggests that the largest increases might occur in the western North Pacific region, but with noticeable increases in the South Indian Ocean and in the North Atlantic region.
"Our study has not established a cause," he continued, "but we suspect that the projected decrease in man-made aerosol particles may be at least partly responsible."
Aerosol particles can work to block out the sun's rays, cooling the planet and potentially lowering the ferocity of storms. Despite pollution being considered a preventative measure in this context, Emanuel emphasized, "I am not advocating going back to aerosol pollution!"
"The conclusions from this study rely on a large number of assumptions, many of which only have limited support from theory and observations and hence are associated with substantial uncertainties," she said. "Personally, I take studies that project future tropical cyclone activity from climate models with a grain of salt."
Roger Pielke, Jr., an environmental studies professor at the University of Colorado, gave the paper a more measured reaction to the study.
"Kerry Emanuel is a smart scientist; I'll trust that he has done good work here," he said, adding his own research suggests the capability to predict the impacts of future hurricanes is at least decades away.
In his simulations, Emanuel combined his own local storm model with six global climate models from the Intergovernmental Panel on Climate Change (IPCC), considered to be some of the most advanced models for greenhouse gases. According to Emanuel, his model's improvement on other models is its ability to highly resolve a massive storm's eyewall.
Using the six combination models and historical data, Emanuel modeled 600 storms every year from 1950 to 2005. He also ran the models through 2100, using an IPCC projection that today's carbon dioxide emissions will triple by the end of this century.
According to the scientist, the models reveal the incidence of tropical cyclones will increase by 10 to 40 percent by the end of the century. They also predicted the North Pacific will sustain the greatest increase in activity, along with sizeable increases in the North Atlantic and southern Indian Ocean.
Kevin Trenbert, a scientist at the National Center for Atmospheric Research, said Emanuel's models could be reliable, but they still left open the question of how big the future storms will be, or their duration.
He added if Emanuel's predictions are true, the South Pacific will see more monsoons and El Nino activity.
"Having a warmer tropical Pacific, especially in the central Pacific, makes the overall atmosphere more like those in El Nino events," Trenbert said. "Places like Hawaii and Tahiti and Fiji would likely be more in jeopardy under these scenarios."