Tuesday, November 27, 2012

Damaging Katrina-level storm surges are twice as likely in warm years


Dr. Jeff Masters, 5:22 PM GMT on November 26, 2012

Perhaps the most stunning images in the wake of Hurricane Sandy were the sight of the roller coaster from the Casino Pier in Seaside Heights, New Jersey lying in the Atlantic Ocean. The images reminded us that hurricane storm surges are capable of causing tremendous destruction along the coast, and one of the main concerns on how global warming might affect hurricanes is the potential for stronger hurricanes to create larger storm surges. We expect that global warming should make the strongest hurricanes stronger, since hurricanes are heat engines that take heat energy out of the ocean and converts it to wind energy. These stronger winds will be capable of piling up higher storm surges. However, it is controversial whether or not we have observed an increase in the strongest hurricanes, since hurricane winds are hard to observe. Our long-term hurricane data base is generally too low in quality and covers too short a period of time to make very good estimates of how climate change may be affecting hurricane winds. However, a new 2012 paper, "Homogeneous record of Atlantic hurricane surge threat since 1923" by Grinsted et al., looked at storm surge data from six tide gauges along the U.S. coast from Texas to New Jersey, and concluded that the number of moderately large hurricane and tropical storm surge events has increased since 1923. Moderately large storm surge events are on pace to nearly double by the year 2100, compared to 20th century levels. Moreover, 1-in-9 year to 1-in-30 year Katrina-level storm surge events are twice as likely to occur in warm years compared to cool years, and thus global warming may be able to dramatically increase the frequency of highly damaging extreme storm surge events. Since sea level is steadily rising due to global warming, these future storm surges will also be riding in on top of an elevated ocean surface, and will thus be able to do even greater damage than in the past. Expect to see many more shocking storm surge damage photos in the coming decades, unless we wise up, retreat from areas highly vulnerable to storm surge, and invest in increased shoreline protection measures.

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