Joe Romm claims that September didn’t used to be hot in the US, and that CO2 is making it hotter.
This is blatant straight up fraud. By every measure, US September heatwaves were much worse prior to 1960.
The year 1913 brought the hottest temperature ever recorded on Earth, the longest stretch of days over 100 degrees on record in the Midwest, and 100 degree temperatures in September to Chicago.
Every single climate indicator shows that September heatwaves used to be much worse.