The Science of Violent Weather in a Warmer World
As a consequence of global warming, there tend to be FEWER violent storms, to include tornadoes and hurricanes, because the USEFUL energy for driving such events is reduced. This is well supported by both the historical record and fundamental and well understood theoretical considerations.
Violent weather is reduced primarily because it is not higher temperatures which drive global weather, but rather temperature differences. And in a warmer world, temperature differences are reduced on a global scale, as for example between the tropics and the poles as well as between the surface and the troposphere . That is to say, both the poles and troposphere tend to warm earlier and to a greater extent.
Also while it is true that warmer air can support exponentially more water vapor, the thermodynamic irreversibility of the evaporation-condensation cycle tends to dissipate energy into unusable forms not available for the work of driving the weather and especially violent storms . This is the entropy component of the free energy. More water vapor thus reduces the number and intensity of storms.
A WARMER WORLD MEANS FEWER TORNADOS
Even as our instrumentation to detect and thus count tornados has improved, the historical trend, in spite of rising CO2, has been for FEWER tornados of all categories for the last 60-70 years .
A WARMER WORLD MEANS FEWER HURRICANES
Note that hurricanes require a minimum sea surface temperature to initially form but that warming of the sea surface also causes wind shear which overwhelms this effect. The net trend of a warmer world is thus for fewer and less intense hurricanes .
In a warmer world, El Nino events (which are periods of exceptionally warm sea surface temperatures in the Pacific) are more frequent and each one of these eliminates all Atlantic hurricanes also because of the resultant wind shear at high altitudes.
Indeed the historical record indicates a DECLINING trend in number of hurricanes in a warming world since the peak of the Little Ice Age in the 1600’s .
And the total energy available for hurricanes likewise DOES NOT track either the rising CO2 or the sea surface temperature; almost as if it was the temperature differences that really mattered (decreasing) as all elementary science textbooks claim, rather than absolute temperatures .
What a warmer world means for the United States which is subject to Atlantic hurricanes is that a warmer world means FEWER hurricanes as actually measured and as theoretical considerations would require. This is obvious when plotting the hurricane tracks as shown below:
And there is a reduction in hurricanes striking the USA from 0.56/year (colder sea surface) to 0.16/year (warmer sea surface even though there is MUCH more CO2) as shown below:
In the above picture, a colder world on the left is observed to have many more hurricane landfalls for the east coast than a warmer world on the right.
Another telling factor is that hurricane frequency peaks in September which is entirely disconnected from the month in which sea surface temperatures are highest indicating that other factors are dominant .
Greater property damage does not mean worse weather but rather a larger population especially in marginal costal areas.
Dim Coumou, Jascha Lehmann, and Johanna Beckmann, “The Weakening Summer Circulation in the Northern Hemisphere Mid-latitudes”, Science, Vol. 348, Issue 6232 (17 April 2015).
as referenced in Gabriel A. Vecchi and Brian J. Soden, “Increased tropical Atlantic wind shear in model projections of global warming”,
Geophysical Research Letters, Vol. 34, L08702, doi:10.1029/2006GL028905, 2007.
as referenced in
J. Lighthill, G. Holland, and W. Ray, “Global Climate Change and Tropical Cyclones,” Bulletin of the American Meteorological Society, 75 (1994), pp. 2147–2157.
L. Bengtsson, et al., “Will Greenhouse Gas-induced Warming over the Next 50 Years Lead to a Higher Frequency and Greater Intensity of Hurricanes?” Tellus, 48A (1996), pp. 57–73.
C.W. Landsea, et al., “Downward Trends in the Frequency of Intense Atlantic Hurricanes During the Past Five Decades,” Geophysical Research Letters, 23 (1996), pp. 1697–1700.
William Gray (Professor Emeritus of Atmospheric Science, Department
of Atmospheric Science, Colorado State University) in a paper called
Hurricanes and Climate Change(Oct. 2006)