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How Global Warming Will Make Hurricanes Like Irene Worse

Climate science suggests that global warming may lead to more and more extreme weather events like Hurricane Irene.
 
 
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Climate science suggests that global warming will make hurricanes like Irene more destructive in three ways (all things being equal):

  1. Sea level rise makes storm surges more destructive.
  2. “Owing to higher SSTs [sea surface temperatures] from human activities, the increased water vapor in the atmosphere leads to 5 to 10% more rainfall and increases the risk of flooding,” as NCAR Senior Scientist Kevin Trenberth put it in an email.
  3. “However, because water vapor and higher ocean temperatures help fuel the storm, it is likely to be more intense and bigger as well,” as Trenberth writes

On the third point, warming also extends the range of warm SSTs, which can help sustain the strength of a hurricane as it steers on a northerly track. As meteorologist and former hurricane hunter Dr. Jeff Masters  has explained:

… this year sea surface temperatures 1 – 3°F warmer than average extend along the East Coast from North Carolina to New York. Waters of at least 26°C extend all the way to Southern New Jersey, which will make it easier for Irene to maintain its strength much farther to the north than a hurricane usually can. During the month of July, ocean temperature off the mid-Atlantic coast (35°N – 40°N, 75°W – 70°W) averaged 2.6°F (1.45°C) above average, the second highest July ocean temperatures since record keeping began over a century ago (the record was 3.8°F above average, set in 2010.) These warm ocean temperatures will also make Irene a much wetter hurricane than is typical, since much more water vapor can evaporate into the air from record-warm ocean surfaces.

Also, hurricanes tend to be self-limiting, in that they churn up deeper (usually cooler) water, that can stop them from gaining strength and also weaken them.  So since global warming also warms the deeper ocean, it further helps hurricanes stay stronger longer.

One says, “all things being equal,”  because, among other things, it is possible that global warming will increase wind shear, which can disrupt hurricanes.

The media prefer to ask the wrong question — as Politico did Friday with its  piece, “Was Hurricane Irene caused by global warming?”  But they do have a good quote from perhaps the leading expert on the subject:

I think the evidence is fairly compelling that we’re seeing a climate change signal in the Atlantic, ” said Kerry Emanuel,  a professor of atmospheric science at the Massachusetts Institute of Technology. Citing other recent trends of extreme weather, including hailstorms and catastrophic tornadoes, “one begins to wonder,  if you add all those up,  maybe you are seeing a global warming effect.”

Still, he adds, “I would be reluctant myself to say anything about global warming and Irene” — but again, that I think is a function of asking the wrong question.  That’s a point Climate Central makes in its post on this subject, “ Irene’s Potential for Destruction Made Worse by Global Warming, Sea Level Rise“:

 

At the moment, the immediate question for anyone in the path of the storm is — or should be —  “how can I keep myself and my loved ones safe?” But another question may be lingering in the background. It’s the same question that came up in April, when a series of killer tornadoes tore up the South in April, and in May, when floods ravaged the entire Mississippi River basin, and in July, when killer  heat waves seared the Midwest and Northeast, and in August, when Texas officially completed its worst one-year drought on record — a drought that isn’t over by a long shot.

 
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