Global warming is a funny thing. Whenever we experience a heat wave the press proclaims it is the face of global warming, but when we have an unusual cold snap, it is merely natural variation.
The Arizona Daily Star had an interesting article today concerning the number of days in Tucson with maximum temperatures over 100° F. The story says the record was set in 1994 with 99 days over 100° F and speculates upon our chances of breaking that record this year. The “normal” number of days over 100° F is 62 according to the National Weather Service.
Also interesting is the statistic that July 4, 2012, had the coolest maximum temperature on record, 86°F.
Looking at a larger picture and a slightly different statistic, we see that the greatest number of maximum temperature records in the U.S. were set in the 1930s. Below is a graph compiled by Steven Goddard from U.S. Historical Climatology Network (USHCN) records:
Getting back to Tucson, we see from the graphics in the Star article that we have had more years, with more days over 100° F than “normal” within the last 25 years or so. That could be a reflection of the urban heat island effect. Our asphalt and concrete absorbs more heat and reflects it back at night. I discuss that in my post Warmer nights no proof of global warming.
A graphic from that post demonstrates the problem by comparing the temperature trend in urban Tucson with that from rural Tombstone:
You can see that Tucson temperatures have been rising but there is no trend in the rural Tombstone station. Carbon dioxide works in mysterious ways.
So, the big news from the Arizona Daily Star is: Summers in Tucson are hot.