Tuesday, June 23, 2015

New Study Links Global Warming to Hurricane Sandy and Other Extreme Weather Events

Linear sea-level trends from August 1993 to July 2013 are shown. The global mean is 3.3 mm yr−1, and the track of supertyphoon Haiyan from 3 to 11 November 2013 is indicated in green, with the most intense phase when it was a category 5… (Credit: ) Click to Enlarge.
One of the hottest areas of climate research these days is on the potential connections between human emissions, global warming, and extreme weather.  Will global warming make extreme weather more common or less common?  More severe or less severe?

New research, just published Monday in Nature Climate Change helps to answer that question by approaching the problem in a novel way.  In short yes, human emissions of greenhouse gases have made certain particular weather events more severe.  Let’s investigate how they arrived at this conclusion.

Lead author Kevin Trenberth and his team recognized that there are two potential ways a warming climate may lead to weather changes.  The first way is through something called thermodynamics.  We experience thermodynamics in our own lives.  Warm air can be more humid than cold air; we feel that difference throughout the year.  Also, warm air evaporates water more quickly.  That’s why hair blow dryers and restroom hand dryers usually use heated air.  It’s why puddles evaporate more quickly on hot days.

In short, the atmosphere can become either warmer and wetter or warmer and dryer, depending on where you are.  The general rule of thumb is that areas which are currently dry will become drier; areas that are currently wet will become wetter; and rains will occur in heavier downbursts.
In other words, the authors take for granted that an event has occurred and they ask, how did climate change affect its impact?

The authors use a few well-known cases studies.  “Snowmaggedon,” which occurred in Washington DC in 2010; superstorm Sandy; supertyphoon Haiyan; and the flooding in Boulder, Colorado.  They found that for Snowmaggedon and Sandy, unusually warm waters made those events worse.  In addition, for Sandy, the human-caused sea level rise added to the storm surge.  They report,
It is possible that subways and tunnels may not have been flooded without the warming-induced increases in sea level and storm intensity and size. Putting the potential price tag of human climate change on this storm in the tens of billions of dollars.
... Later, the authors make reference to the 2010 Russian heat wave and the current drought in California. This new study reconciles past conflicting studies where very little evidence of a climate link was found of general circulation changes, but evidence is clear of in the thermodynamics.

Without getting too deep in the weeds, the authors also explain why other teams have failed to make a connection between extreme weather and a warming planet.

Read more at New Study Links Global Warming to Hurricane Sandy and Other Extreme Weather Events

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