It is always good to look at the raw data before our friends have had a chance to tamper with it.
State College Pennsylvania has had seven July days over 100 degrees. Four were in the 1930s, and six were below 350 ppm CO2. As you can see in the graph above, the 1930s was by far the hottest decade, and the 1970 passage of the Clean Air Act had no effect.
Would we expect Harvard researchers to actually do some research before publishing?