FACT BRIEF

Do record US heat waves in the 1930s disprove global warming?

Friday, September 4, 2020

By Claire Zimmerman

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The most severe heat waves in the U.S. did occur in the 1930s, but overall temperatures today are higher than they were then, both domestically and globally.

Climate is a measure of weather overtime. Global average temperatures have trended upward since the industrial revolution. There is a scientific consensus that human activities which emit heat-trapping gases into the atmosphere are the primary cause. Globally, July 2023 was the hottest month on record.

During the Dust Bowl, drought, combined with poor land use practices, eroded the soil, depriving it of its temperature-moderating moisture. Land heats up more quickly than water, which enabled already hot temperatures to soar even higher.

The EPA’s U.S. Annual Heat Wave Index is a combined measure of how many times there was a period of four or more days of unusually high temperatures in a given percentage of the country.

This brief has been updated to reflect the most up-to-date information as of July 31, 2023.

This fact brief is responsive to conversations such as this one.

Sources

US Environmental Protection Agency Climate Change Indicators: Heat Waves (Figure 3)

National Oceanic and Atmospheric Administration Climate Change: Global Temperature

Environmental Research Letters Consensus on consensus: a synthesis of consensus estimates on human-caused global warming

World Meteorological Association July 2023 is set to be the hottest month on record

National Weather Service Heat wave of July 1936

National Oceanic and Atmospheric Administration Radiative Heating of Land and Water

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