Tuesday, July 9, 2013

Bigger and more frequent storms ahead

Jennifer Chu in MIT News: ... [A]ccording to a report by MIT’s Kerry Emanuel, the coming century may whip up stronger and more frequent storms as the planet warms. Emanuel found that rising greenhouse-gas emissions may contribute to a 10 to 40 percent increase in the frequency of tropical cyclones by the year 2100. These storms may produce 45 percent more power, Emanuel predicts, generating stronger winds, rain and storm surges around the world. This ramped-up storm activity will likely be felt most acutely in the North Pacific, as well as the North Atlantic and the southern Indian Ocean.

Emanuel, the Cecil and Ida Green Professor of Atmospheric Science in MIT’s Department of Earth, Atmospheric and Planetary Sciences, says that increases of this magnitude might pose significant risks to some coastal locations around the world.

...To simulate tropical cyclones at both the global and local scales, Emanuel embedded a high-resolution, local storm model within six global climate models from the IPCC. The local storm model, developed by Emanuel, simulates the development of tropical cyclones, based on regional temperatures and large-scale atmospheric flow, at a resolution that increases as a storm intensifies. One key advantage over other models is the simulation’s ability to resolve a storm’s eyewall — a ring of thunderstorms circling the eye of a storm, where the most severe weather occurs.

....The simulations indicate that the frequency of tropical cyclones will increase by 10 to 40 percent by 2100, given a rise in greenhouse-gas emissions. They predict that this more frequent storm activity will be felt most strongly in the North Pacific, with substantial increases in the North Atlantic and southern Indian Ocean as well.

Emanuel also simulated the intensity of tropical cyclones as measured by what’s called a “power dissipation index,” which describes the total kinetic energy dissipated by a tropical cyclone. From his calculations, Emanuel found that the intensity of tropical cyclones could increase by 45 percent by 2100. Those storms that make landfall would be 55 percent more intense — a substantial increase, Emanuel says.

Emanuel adds that while it seems likely that storms will become more intense in the future, these predictions are far from definitive: Other global and regional models have had mixed results in simulating storm scenarios with global warming....

Hurricane Isabel (2003) from the International Space Station

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