Guest post by Dr. Richard Alan Keen
Although I’ve lived in Colorado for 40+ years, Philadelphia is my ancestral home and I keep track of the weather there. Of course, I’m excited about any event that sets records there, and last week’s heat wave set several. Apparently Michael Mann is excited, too, and in his “Victory and Vindication” interview, he said:
“Record heat wave in the US that’s part of a larger picture
of early summer temperatures that are the warmest on record,
which is part of a larger picture of a globe that is running warmer than ever before…”
So is Philadelphia getting more heat waves? Here’s a chart of annual maximum temperatures for Philadelphia since 1873, when the Weather Bureau installed self-registering max-min thermometers.
Earlier records are not comparable, since they are from hourly or 2 p.m. readings, which lead to lower extremes.
I think the graph speaks for itself – the trend line (plotted in red) is rather flat, with an upward trend of 0.2 degrees F per century. If that continues for another century, the old town will heat up another 0.2 degrees and turn into an inferno.
As for the question of more heat waves, before 1942, the mid-point of the data, Philadelphia enjoyed 9 years in which the maximum temperature exceeded 100 degrees. For the second half of the record, since 1942, there were, well, 9 years. Not much of an increase.
If that trend continues, I would expect another 9 years with 100+ degree temperatures by 2080.
Dr. Richard Keen
Co-op observer, climatologist, author, and teacher.