by Robert W. Endlich, December 18, 2018 in CAtmSciForum

In describing the errors in the Fourth National Climate Assessment, ‘NCA4’, I’ll use the words from the Executive Summary which purport to link climate changes in the USA to global climate change.

The first claim, “The last few years have also seen record-breaking, climate-related weather extremes,“ is shown to be false, simply by examining climate records, some from the National Climate Data Center.

Tornadoes have been decreasing over the past six decades as temperatures moderate from the significant cooling of the 1940s to 1970s.  As a basic knowledge of meteorology teaches, it is the pole to equator temperature difference that drives the intensity of cold season storms and especially the spring-season storms which bring the extremely strong tornado outbreaks.

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Figure 1.  Annual count of strong to violent tornadoes from 1954-2014, showing a significant decrease of tornado activity the past 60 years, based on data from NOAAs Storm Prediction Center. [Note: This graphic replaces the original graphic that showed all tornadoes EF1 and stronger. Correction made 1/25/2019].

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