Monday, November 11, 2013

Will global warming make major typhoons more probable? - Yes

Did Climate change cause Typhoon Haiyan? No
     Haiyan was caused, just like any other tropical storm, by warm sea surface, humid air, and low wind shear (change in wind characteristics at different altitudes).
     The fact is that global warming causes warmer sea surface and more humid air, so:

Does a warmer sea and more humid atmosphere make typhoons like Haiyan more probable? Yes indeed.

     Regarding warmer seas, take a look at this map from NOAA, showing a tract of warm sea along the path of Haiyan, not just warm on the surface, but warm deep down. This means that as heat is passed from sea surface to the air, to power the storm, more heat can well up to replace the hear that was lost. This may prove, after further analysis, to be a factor in the unusual strength of Haiyan.

     Regarding more humid atmospheres, there is now 4% more water vapour in the atmosphere compared to the 1970s.

Denialists are doing what denialists do. Denying. Anthony Watts tries to minimise the strength of the storm, its wind speed, and the number killed (he puts it at 1,000). Others quote "The Data" showing that hurricane numbers have not increased in line with global surface temperatures. Well of course not. It is not global surface temperature that is operative, but regional sea surface temperatures, together with other factors.

There is a reasonable correlation between major hurricane incidence and the Pacific Decadal Oscillation trace, as I show here.

So in conclusion, the question "Did global warming cause Haiyan" is a dumb question. The right question is "Will global warming make further Haiyans more probable?" and the answer to that is a resounding Yes.

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