Will the record heat of the 1930s undermine the science of human-caused climate change?

TAMPA, FL (WFLA) – A popular talking point aimed at disproving 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. This was far from true for the planet as a whole.

What’s more, it might surprise you to hear that the sweltering summers in the United States in that decade were partly man-made, and the reason is astonishing.

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

The graph compares the average temperature for all months from 1930 to 1939 with the average temperature for all months from 2010 to June 2023. Red shows where the warmest places are at present, and blue shows which places are cooler at present.

It is clear that global warming is a global phenomenon. The image shows that the current climate is warmer globally. But there are some small regional exceptions such as the Atlantic Ocean south of Greenland and the central United States where the weather was much warmer in the 30s.

Credit: Brian Brettschneider

The year 1936 in particular really stands out in the heart of the nation. The summer heatwave was so intense in the United States that it is considered a once-in-100-year event, with 25% of all daily heat records in the United States set during that summer, and half of those records set during the 1930s.

The graphic below compares the summer of 1936 to the summer of 2022. It does show how hot it was in North America, but it also shows that it wasn’t very warm in most parts of the world. The summer of 2022 was easily hotter.

Credit: Scott Duncan

To visualize a different approach, look at the line chart below. This shows, on a global scale, that the 1930s has been cooler than every decade since, and much cooler than it has been in the last few decades.

Credit: Brian Brettschneider

The line chart clearly shows the long-term trend, which has been rising rapidly since the 1970s. The main cause is human-caused climate change due to the burning of fossil fuels and the release of greenhouse gases.

So, if the 1930s were so cold globally, why were they so warm in the United States? There are two notable reasons. One is normal and the other is not. First, let’s discuss the natural part.

According to Dr. Tim Cowan, a climate researcher who has studied the Dust Age extensively, during the 1920s and 1930s the Bermuda Rise shifted eastward into the Atlantic Ocean, and patterns shifted over the eastern Pacific Ocean as well.

This shift in pressure and wind patterns shifted the Gulf of Mexico moisture plume eastward away from the central United States, creating drought in the heart of the country. Dry weather helps promote heat waves because it is easier to heat dry air than it is to heat moist air.

But natural transformation explains only part of the problem. The rest of human error shows the extent of the impact humans can have on the climate, even for a relatively small population. This human error was poor farming practices throughout the Plain States.

In the 1920s and 1930s, vast tracts of land in the middle of the country were converted from native prairie grasses to barren fields and then corn crops. Prairie grass has long roots and can absorb groundwater even in times of drought. Grass also holds the soil in place.

On the other hand, corn has shallow roots that don’t pull much moisture from the ground and don’t hold the soil in place.

The shift of the Plains states from prairie grass to corn dried and warmed the regional climate. Credit: WFLA

This shift had a major impact on the regional climate by amplifying the natural drought that existed and increasing heat. It ended up causing dust storms, famine and hardship for the people living there.

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

As a result of this mutual blow from Mother Nature and poor agricultural practices, the region experienced one of its driest regions on record. The map below shows that it was the driest year on record for the Plains and Midwest.

Image: NOAA

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

Image: NOAA

The 1930s taught us a valuable lesson about the impact that humans can have on the climate. Midcountry had a very small population, but it had such a great influence on the climate that the era became known as the Dust Bowl.

In 1936 the population of the United States was 125 million. Today it is almost three times larger. On Earth today we have eight billion people.

The bottom line is that humans are capable of having a very large impact on our planet in many ways. Perhaps the most important impact is the speed at which we are transforming the climate by burning fossil fuels and releasing carbon pollution.

In contrast to those who are skeptical about the science of climate change, the 1930s do not disprove climate science, but rather help reveal the significant impact humans have on our planet’s climate.

In fact, a recent study by Dr. Tim Cowan showed that extreme heat waves in the US heartland, like the one that occurred in the Dust Bowl, are now two to three times more likely due to human-caused climate change.

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