What was done
Defining an extreme temperature day as a day that exceeds by one standard deviation the long-term average temperature for a given day, the authors analyzed trends in both warm and cold extreme temperature days for the four seasons of the year - winter, spring, summer and fall - for six states in the south-central United States over the period 1901-1987.

What was learned
For the six states (Texas, Oklahoma, Arkansas, Louisiana, Mississippi and Tennessee) comprising the territory served by the Southern Regional Climate Center, by whom the authors are employed, the authors determined that "since 1901 the overall temperature trend appears to be downward with more frequent cold days and less frequent warm days at most stations in all seasons."  In the winter, in fact, all stations studied showed an increase in the frequency of cold days through the study period, while over half of them displayed a decrease in the frequency of warm days.  In the spring, the majority of stations also showed an increasing number of cold days and a decreasing number of warm days; and summer results were similar, with even higher significance levels.  The authors also note, however, that "although there has been a change in the frequency of extreme temperature days at many stations, the magnitude of the temperature departures has not changed."

What it means
For this specific region of the United States, the 20th century was a time of decreasing frequency of extreme warm days and increasing frequency of extreme cold days, both of which trends are not exactly the type one would expect to find if the climate alarmists were right.  As we always seem to say in our Temperature Record of the Week report, "Not much global warming here!"