Dr. Jeff Masters, the co-founder of the Weather Underground website is the voice of climate sanity in the meteorologist world. He has consistently noted, as he did in this post from last March, how the models used by climate scientists make predictions about how winter storms are going to change in a warming world that are deeply consistent with what we are seeing unfold before us:
General Circulation Models (GCMs) like the ones used in the 2007 IPCC Assessment Report do a very good job simulating how winter storms behave in the current climate, and we can run simulations of the atmosphere with extra greenhouse gases to see how winter storms will behave in the future. The results are very interesting. Global warming is expected to warm the poles more than the equatorial regions. This reduces the difference in temperature between the pole and Equator. Since winter storms form in response to the atmosphere’s need to transport heat from the Equator to the poles, this reduced temperature difference reduces the need for winter storms, and thus the models predict fewer storms will form. However, since a warmer world increases the amount of evaporation from the surface and puts more moisture in the air, these future storms drop more precipitation. During the process of creating that precipitation, the water vapor in the storm must condense into liquid or frozen water, liberating “latent heat”–the extra heat that was originally added to the water vapor to evaporate it in the first place. This latent heat intensifies the winter storm, lowering the central pressure and making the winds increase. So, the modeling studies predict a future with fewer total winter storms, but a greater number of intense storms. These intense storms will have more lift, and will thus tend to drop more precipitation–including snow, when we get areas of strong lift in the -15°C preferred snowflake formation region.
We’ve now had two remarkable extratropical storms this year in the U.S. that have smashed all-time low pressure records across a large portion of the country. Is this a sign that these type of storms may be getting stronger? Well, there is evidence that wintertime extratropical storms have grown in intensity in the Pacific, Arctic, and Great Lakes in recent decades.
And as always, Masters is tracking storms in the parts of the world more accustomed to this kind of activity. However, he notes that it is “unprecedented” to have a hurricane of the magnitude of Tomas appear this late in the season.
The climate is changing. The effects are real. The need for action is urgent – and the zombie armies of climate denial are approaching.