Climate change could lead to decades of megadroughts in the U.S., study says. Global warming has increased the risk of such extreme events, researchers led by Mohammad Reza Alizadeh of McGill University and Mojtaba Sadegh of Boise State University explain in the scientific journal Science Advances. Such long periods of drought also occurred in the USA in the 12. and 13. century.
Since the middle of August some fires rage at the US west coast. In California alone, some 19,000.000 firefighters against more than 20 large fires. The flames destroyed more than 5800 buildings since mid-August.
Heat waves and drought
As climate change progresses, extreme events such as heat waves and droughts are occurring more frequently at the same time, the researchers explain. Their study focuses on this co-occurrence of drought and heat over the past 122 years. "Episodes of extreme drought and heat are the recipe for major forest fires", explained Mojtaba Sadegh. "These extremes are intensifying and expanding on an unprecedented spatial scale, enabling the current wildfires along the entire U.S. West Coast."
Even shorter durrephases that lasted less than a decade, such as those known as the "Dust Bowl" known as the U.S. drought in the 1930s, could have devastating effects if they occurred simultaneously with heat. Among other things, climatic events in the atmosphere and on the ground could lead to such extremes in their interaction, it says in the study.
Scientists suspect that the driving factor for simultaneous heat-duration periods in the recent past is primarily excessive heat. In the "Dust Bowl"-period, the lack of precipitation was the main culprit.
Heat wave in Russia
A megadrought is usually preceded by a prolonged high-prere area, which created cloudless conditions that allowed a supply of hot air. Dry soil increases the amount of warmth in the incoming sunlight, which affects the ambient temperature, the article says. The result is that heat waves become more intense.
The researchers cite the heat wave in Russia in 2010 as an example. There, the interaction of durre and heat had increased the probability of a mega-heat wave by 13 times. The combination of dry soil and clear air prevents the formation of clouds, which results in less rain and, as a result, increases drought, the researchers explain.