Last night, Phoenix suffered a massive dust storm. Videos show a wall of dust moving across the city. The dust was a nearly a mile high and about 100 miles wide, and even more storms are forecast for tonight. While this individual storm clearly differed in magnitude, the images were not unlike those of the “Dust Bowl” storms that swept across the Midwest from 1930 to 1936. After seeing the videos and photographs from last night, one has to wonder: what causes these monster dust storms?

Texas, 1935

Weather Service officials said the latest storm was particularly dense because of a recent drought. Droughts played a major role in the Dust Bowl storms of the 1930s, but they weren't the only factor. Those storms may have also been caused by degradation of the Great Plains, according to Benjamin I. Cook and Ron L. Miller, who published a study on the topic, “Amplification of the ‘Dust Bowl’ drought through human-induced land degradation,” in the Proceedings of the National Academy of Sciences. Looking at La Nina, the authors speculated that the effects of sea-surface temperature on temperature and precipitation patterns did not fully explain the drought patterns of the Dust Bowl storms. Instead, they found that when wheat crops failed, it left the ground barren, so wind could easily pick up the dry soil. This exacerbated the existing La Nina drought conditions. They conclude, “Human-induced land degradation is likely to have not only contributed to the dust storms of the 1930s but also amplified the drought, and these together turned a modest [sea surface temperature]-forced drought into one of the worst environmental disasters the U.S. has experienced.” Today, meteorologists have a new fear: because of the impact of climate change, the current storm could precede “quasi-permanent drought conditions,” also known as a mega drought.