by Anthony Watts, August 6, 2018 in WUWT

During the 1930s, when the atmospheric CO2 concentration was about 100 ppm lower than today (310 ppm vs. 410 ppm), United States heat waves were just as if not more common than recent decades.

Recently there has been much ado about heat waves and the hottest-ever-recorded-temperatures making their rounds in Northern Hemisphere summer.

Yet scientists have determined that heat waves are largely driven by natural variability, not anthropogenic CO2 emissions.

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