Essay by Jim Steele, Director emeritus, Sierra Nevada Field Campus, San Francisco State University
The heat wave and near record-breaking temperatures in Death Valley provides a superb teaching moment to show why CO2 has nothing to do with heat waves whether the record is ever broken or not.
- Most heat waves are associated with dry conditions. Water vapor contributes between 80 and 94% of the greenhouse effect. But during a dry heat wave, greenhouse gases are reduced, and that fact should alert people that other more critical factors are governing heat waves. The dryness lowers the soil’s heat capacity and allows temperatures to rise more rapidly. The dryness also creates clear skies that increases incoming solar radiation. The winter drought set the stage for this west coast heat wave as well as Europe 2003 and Russia 2010.
- All heat waves are caused by stationary high pressure systems. Always! High pressure systems are driven dry descending air currents. In addition to the dryness amplification mentioned above, Highs cause two other critical weather events.
2.1 High pressure systems force the jet stream northward and prevent cooling air from moving southward.
2.2 Most importantly descending air currents adiabatically generate a thermal ceiling that prevents rising convection currents from carrying away surface heat. Models have demonstrated that if convection stops the global temperature could rise by 100° F. Adiabatic heating means no heat is added. Temperatures rise because the air is compressed and the constrained molecular motion releases heat. Many cultures in southeast Asia used fire pistons to start fires by simply squeezing air in a tube. When that adiabatically heated air reaches the ground we get foehn storms, when it hovers a few hundred feet above the ground we get heat waves. Air only rises if it is warmer than its surroundings. When rising air reaches a layer of adiabatically heated air the rising convection currents stop and the surface heat is trapped just like the raised windows in your car trap the heat.
Descending air currents of High pressure systems are also the reason we have deserts and why the world’s records for hottest temperatures on each continent are not at the equator but about 32 to 36° North.
The reason for this pattern is the Hadley Cells. At the equator despite the greatest heating by the sun, convection currents carry away the heat. Those rising currents are balanced by descending currents that are most powerfully focused in the regions that hold the world’s records. Those dry descending currents also cause the pattern of the world deserts. Those descending currents also create the quasi permanent high pressure system in the Pacific and the Bermuda High in the Atlantic.
Finally heat waves are caused by stationary blocking highs and all research shows that blocking highs are most common during the cool phase of the Pacific Decadal Oscillation or North Atlantic Oscillation. The PDO cool phase occurred from about 1900 to 1920, again from 1946 to 1976, and we have currently been in the cool phase since about 2003. I bet most heat wave records for the western half of the USA occurred during those time periods. Death Valley’s record was 1913. However nearly every single model driven by CO2 failed to predict the cooling in the eastern Pacific Ocean
The CO2 advocates simply predicted heat waves in the future, but anyone can do that and be right eventually. However, the mechanisms of every heat wave contradict nearly every aspect of the global warming theory. They cannot even argue that it is more likely because its warmer. Death Valleys maximum temperatures have not exceeded the 1930s. These heat waves are good examples of how weather dynamics cause extreme heat independently of the sun or CO2.
This article is adapted from Landscapes & Cycles: An Environmentalist’s Journey to Climate Skepticism