A recent United Nations report on climate change painted a grim vision of the future. Even if countries manage to cut emissions sharply in coming years, global warming will likely still reach a critical limit, 1.5°C, leading to increasingly extreme weather patterns and droughts.The United States reached a troubling milestone this year with the hottest year on record, tying 1936 in the period known as the Dust Bowl, when severe dust storms swept the southwestern Great Plains, damaging the ecology and agriculture. While there is a widespread belief that that the Dust Bowl resulted from human activity, the facts are a bit more complicated.

According to eco-geomorphologist Kasey Bolles, “tree-ring records show that 1934 was the worst drought year in the last millennium, and buried soils across the Great Plains reveal that drought is a common feature of the region.”

In other words, the primary cause of the Dust Bowl was the location itself: The southwestern Great Plains states have always been prone to drought and dust storms. “Agricultural census data indicates that the most heavily cultivated areas were at the eastern edge of the Great Plains, far from the core of the Dust Bowl,” Bolles said in an interview.

Farming techniques of the early 20th century certainly exacerbated Dust Bowl conditions across the Southwest. Some farmers practiced a technique called listing, a type of plowing that was thought to reduce erosion. But instead, Bolles said, listing “broke up soil surface crusts and churned up silt-size particles, which are easily picked up by wind.”So how did the Dust Bowl end? The answer is a combination of human effort and luck. “The rains returned in the early 1940s to break the drought,” Bolles said, while environmental research and public effort “led to better understanding of an important ecosystem that we still benefit from.”

Today, many of the natural conditions that triggered Dust Bowl storms in the 1930s are back, threatening to bring similar problems: record-high temperatures, severe droughts and a significant increase in airborne dust. Beyond concerns about agricultural harm, scientists are worried about the effects of airborne dust on public health. Dust storms decrease visibility and contain tiny particles that can cause heart and lung problems over time. Human activity is the main driver of these new environmental changes.

Droughts and heat waves are inevitable, and they can be devastating even when human activity does not exacerbate them. Without corrective action, scientists warn, the next Dust Bowl era could be even worse.

ALEX REMNICK is a writer and social media producer at Retro Report. This article first appeared in Retro Report’s free weekly newsletter. Stay up to date. Subscribe to our newsletters.