Saturday, September 23, 2017

Kerry Emanuel:  This Year’s Hurricanes Are a Taste of the Future

Climate scientist describes physics behind expected increase in storm strength due to climate change.

Kerry Emanuel, the Cecil and Ida Green Professor of Atmospheric Science and co-director of the Lorenz Center at MIT (Photo Credit: Helen Hill) Click to Enlarge.
In a detailed talk about the history and the underlying physics of hurricanes and tropical cyclones, MIT Professor Kerry Emanuel Wednesday explained why climate change will cause such storms to become much stronger and reach peak intensity further north, heightening their potential impacts on human lives in coming years.

“Climate change, if unimpeded, will greatly increase the probability of extreme events,” such as the three record-breaking hurricanes of recent weeks, he said.

In Houston Hurricane Harvey, which devastated parts of the Texas coastline and produced more total rainfall than any U.S. hurricane on record, would have been considered a one-in-2,000-years event during the 20th century, according to the best available reconstructions of the past record of such storms, Emanuel said.  But in the 21st century, that probability could drop to one in 100 years, given the likely trajectory of climate change conditions.  Hurricane Irma, with its record-breaking duration as a Category 5 storm, will go from being a one-in-800-years event in the area of the Caribbean that suffered a direct hit, to a one-in-80-years event by the end of this century, he said.
Although his talk had been titled “What Do Hurricanes Harvey and Irma Portend?” Emanuel pointed out that now there was “a tragic irony in presenting this lecture just hours after another hurricane [Maria] has devastated Puerto Rico.”  At such a time, he said, “it is natural to ask if these are just natural events.”  Referring to Environmental Protection Agency Administrator Scott Pruitt’s recent comments that it was inappropriate to talk about climate change in relation to hurricanes Harvey and Irma, Emanuel wondered aloud “if after 9/11 he would have said that now is not a good time to talk about terrorism?”

Already, over the last four decades, he said, hurricanes and cyclones globally have caused an average of $700 billion in damages annually since 1971.  Meanwhile, thanks to population growth and the development of oceanfront property, “the global population exposed to hurricanes has tripled since 1970,” he said.

While hurricanes, like earthquakes and volcanoes, “are part of nature,” Emanuel said, “what we’re talking about are unnatural disasters — disasters we cause by building structures” in places that are inherently vulnerable to such devastating forces.

Because of policies, including the current system of federally provided flood insurance that gives private insurers little motivation to study countermeasures, he said, “we’re going to be having Harveys, Irmas, and Marias as far as the eye can see.”

While much of the news coverage of hurricanes focuses on the powerful winds, which have indeed been a major cause of damage and loss of life in the islands pummeled by Irma and Maria, Emanuel said that overall it is water, not wind, that causes the vast majority of damage from such storms, though most people underestimate the severity of the water impact.  To illustrate the point, he showed a short, dramatic video of a hurricane-produced storm surge striking a building.  “It is hydrodynamically the same thing as a tsunami,” he explained, as the clip showed water rushing steadily in and quickly engulfing an entire house.

“I wish everyone who lives in zones subject to these storms could see films like this,” he said, adding that the scene depicted was clearly not survivable.  “Water is the big killer.”

Read more at Kerry Emanuel:  This Year’s Hurricanes Are a Taste of the Future

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