TAMPA, Fla. (WFLA) — A common talking point aimed at refuting human-caused climate change is that the 1930s was the hottest decade in recorded history. This is true, but only for the United States during the era known as the Dust Bowl. It was far from true for the planet as a whole.

What’s more, it may surprise you to hear that the super hot U.S. summers of that decade were partially man-made, and the reason why is fascinating.

First, let’s directly address the question of whether the heat of the 1930s undermines the science of human-caused climate change. The answer is no. The science remains rock solid. You can see why in the graphic below.

The graphic compares the average temperature of all months from 1930 to 1939 to the average temperature of all months from 2010 to June 2023. The red shows where it is warmer present day and the blue shows where is colder present day.

Global warming is obviously a global phenomenon. The visual makes clear that on a global scale, the present climate is much warmer. But there are some small regional exceptions such as the Atlantic Ocean south of Greenland and the Central U.S. where it was warmer in the 1930s.

Credit: Brian Brettschneider

The year 1936 in particular really stands out in the Nation’s Heartland. The summer heat wave was so extreme in the U.S. that it is considered a once-in-100-year event, with 25% of all U.S. daily heat records set during that summer and half of such records set during the 1930s. 

The below graphic compares the summer of 1936 to the summer of 2022. It indeed shows how hot it was in North America, but it also shows it was not that warm across much of the globe. The summer of 2022 was easily hotter.

Credit: Scott Duncan

To visualize a different way, look at the below line graph. This makes clear on a global scale that the 1930s were cooler than every decade that followed and much cooler than in the recent few decades.

Credit: Brian Brettschneider

The line graph vividly illustrates the long-term trend which has been quickly warming since the 1970s. The main reason is human-caused climate change due to the burning of fossil fuels and the release of heat-trapping greenhouse gases.

So if the 1930s were so cool globally, then why were they so warm in the U.S.? There are two notable reasons. One is natural and the other is not. First, let’s discuss the natural part.

According to Dr. Tim Cowan, a climate researcher who studied the Dust Bowl Era extensively, during the 1920s and 1930s, the Bermuda high shifted east into the Atlantic, and patterns also shifted over the eastern Pacific.

This shift in pressure and wind patterns shifted the plume of Gulf of Mexico moisture eastward away from the central U.S., bringing drought to the Nation’s Heartland. Dry weather helps to enhance heatwaves because it is easier to heat dry air than it is to heat humid air.

But the natural shift only explains part of the problem. The rest of human error shows just how much of an impact humans can have on the climate, even just a relatively small population. That human error was bad farming practices across the Plain States.

In the 1920s and 30s, huge swaths of the land in the nation’s middle was transformed from native prairie grass to barren fields and then corn crops. Prairie grass has long roots and can suck up groundwater even in dry times. The grass also holds the soil in place.

Corn on the other hand has shallow roots which do not pull much moisture from the ground and do not hold the soil in place.

Transformation of Plains States from Prairie Grass to Corn dried and heated the regional climate. Credit: WFLA

This transformation had a huge impact on the regional climate by amplifying the natural drought that was in place and spiking the heating. This ended up causing dust storms, famine, and hardship to the people living there.

A man walks past a farmhouse in a dust storm at the height of the Dust Bowl in Oklahoma. Credit: Getty Images

As a result of this one-two punch from Mather Nature and bad farming practices, the area experienced one of its driest stretches ever. The below map shows that it was the driest year on record in the Plains and Midwest.

Image: NOAA

Dry weather patterns tend to also go hand in hand with hot weather patterns. The map below shows the temperature rankings in July of 1936. Most of the central U.S. had the hottest or one of the hottest months on record.

Image: NOAA

The 1930s taught us a valuable lesson about the impact man can have on climate. The population of the nation’s middle was very small yet it had an outsized impact on the climate to the degree that the era became known as the Dust Bowl.

In 1936 the U.S. had a population of 125 million people. Today it’s nearly three times larger. And on Earth today we have eight billion people.

The bottom line is that humans can and are having a very significant impact on our planet in many ways. Perhaps the most significant impact is the speed at which we are transforming the climate through the burning of fossil fuels and the release of carbon pollution.

So contrary to those who doubt the science of climate change, the 1930s does not disprove climate science, rather it helps reveal the substantial impact humans have on our planet’s climate.

In fact, a recent study by Dr. Tim Cowan shows that extreme heatwaves in the U.S. Heartland, like those of the Dust Bowl, have now been made two to three times more likely due to human-caused climate change.