From Watts Up With That?

Guest Post by Willis Eschenbach

This is an extension of my previous post entitled “February Fantasy Versus Reality“. Please read that to get the basic ideas. To recap, a study in Science magazine said

Despite the rapid warming that is the cardinal signature of global climate change, especially in the Arctic, where temperatures are rising much more than elsewhere in the world, the United States and other regions of the Northern Hemisphere have experienced a conspicuous and increasingly frequent number of episodes of extremely cold winter weather over the past four decades.

…

The Arctic is warming at a rate twice the global average and severe winter weather is reported to be increasing across many heavily populated mid-latitude regions, but there is no agreement on whether a physical link exists between the two phenomena.”

To test this claim of increasing “severe winter weather”, in my previous post I looked at the average February temperature of the continental US to see if it was cooling. It hasn’t been cooling.

However, a couple of commenters correctly pointed out that the issue discussed in the study was not average temperature. Instead, the authors were talking about “episodes of extremely cold winter weather” such as those Texas experienced in February of 2011 and 2021.

Looking for a more accurate measure of extremely cold winter weather, I got the daily temperature data for the Southern Great Plains from NOAA. Here’s a map of the area in question.

Figure 1. Map of the National Climate Assessment regions.

Then I calculated the standard deviation (a measure of how widely spread out the temperatures are) of the February temperatures. I reasoned that if there were short sharp cold spells, the standard deviation would be larger.

Figure 2. Standard deviations of February minimum daily temperature for the Southern Great Plains. Cold spells are indicated by an increase in the standard deviation.

In Figure 2, we can clearly see the Texas cold spells of 2011 and 2021. But is there a “conspicuous and increasingly frequent number of episodes of extremely cold winter weather over the past four decades”?

Well … in a word, no. Figure 2 shows there was a serious cold spell in 1951. And the Texas State Climatologist agrees, saying:

Jan.–Feb. 1951: Freeze. On Jan. 31.–Feb. 3 and again on Feb. 13–17, cold waves swept over the entire state, bringing snow and sleet. Heavy damage was done in the Lower Rio Grande Valley to truck and citrus crops, notably in the earlier of these northers. During the norther of Jan. 31–Feb. 3, the temperature went to –19°F in Dalhart.

However, during the thirty years after 1951, there was little in the way of “episodes of extremely cold winter weather” until the decade and a half from 1981 to 1996. During that time there were a number of cold episodes, although not as intense as in February 1951. In the coldest of these, in February of 1985, San Antonio got a rare snowfall, and they saw the coldest day ever recorded in Midland, Texas.

However, in the quarter century since 1996, there have only been the two extremely cold spells mentioned above, in 2011 and 2021.

If we divide the 72 years of the record into three 24-year periods, we have only one “episode of extremely cold winter weather” in the first period; six somewhat warmer episodes in the second period; and only two episodes in the most recent 24 years.

So no, in the Southern Great Plains, there is not a “conspicuous and increasingly frequent number of episodes of extremely cold winter weather. Nor is “severe winter weather … increasing” as they claimed. Neither of those statements is true.

Then I thought, “Well, maybe I’m looking too far south. Maybe the claimed effect is visible in the Northern Great Plains”. So it was back to the drawing board, and here’s what I found.

Figure 3. Standard deviations of February minimum daily temperature for the Northern Great Plains. Cold spells are indicated by an increase in the standard deviation

Although there is greater variation in the February minimum temperatures in the Northern Great Plains NCA region, the same situation prevails as in the Southern Great Plains—one February “episode of extremely cold winter weather” in the first 24 years, a half-dozen or so in the middle 24 years, and the two cold Februarys in 2011 and 2021 in the final 24 years. And there is no trend in the data.

Another beautiful theory runs hard aground on a reef of ugly facts.

Best to all,

w.

Data Access—I’ve put the 72 years (1951-2022) of daily Southern Great Plains temperatures, both maximums and minimums, in my Dropbox for download. It’s a fairly small file entitled Great Plains South nClimDiv.csv, 588 KB, in CSV format so it can be opened in Excel or other programs.

My Usual—I can defend my own words. I choose them very carefully. I cannot defend your (mis)understanding of my words. So please, when you comment, quote the exact words you are discussing.