BBR may not be reading this now, but another story: this time, burning hot ground.
I was on Bondi Beach (Sydney, Australia) one very hot summer day (Christmas, +/- a day or two) in 1972. I was on the beach because a shark had been spotted and we were not allowed to even have our toes on wet sand. The dry sand was so hot I had to dig a few inches down so that I could stand and not burn my feet. (Most people had flip-flops that insulated them from the hot sand.) After a few minutes, I had to dig down again. (After a half-hour we gave up and opened the one-use-per-payment storage locker to fetch clothes and shoes and did something else.)
Unlike snow, sand is not a good insulator, so after the sun goes down, much of the accumulated heat will quickly radiate into the air (and, ultimately, space).
As the article I referenced indicated, they did not identify an annual soil temperature drift; I suspect, however, over a longer period of time, they will identify a long term warming trend. With Global Warming, permafrost soils will warm to be seasonally ice-free (i.e., will warm - as BBR admits); seasonally frozen soils will freeze less deeply; other soils will get slightly less cold in the winter.