rather than their severity. They are extremely dry spells that can last for a decade or longer, according to the National Oceanic and Atmosphere Service.
They dry the West, including the present California, long before Europeans settled the region in the 1800s. Most US droughts of the last century, even the scandalous bowl of the 1930s, which forced Oklahoma and other plains to migrate, "have been exceeded in severity and duration several times since Sushi in the past 2000 years, "The National Climate The difference now, of course, is that the western United States is home to more than 70 million people who were not here for the previous medieval megadons. The consequences are much more frightening.
How do scientists know how wet or dry it was centuries ago? Although there is no evidence of the time before the end of the 18th century, scientists can explore paleo-climatic "proxies", such as tree rings and lake sediments, to find out how much or little rain fell hundreds or even thousands of years ago. Scientists can understand why megadroughts happened in the past could help better predict if, how and where it can happen in the future, according to the new study. "In our article, we present the first comprehensive theory of what caused historic megadons that happened during the medieval period, but not around 1600," says lead study author Nathan Sieger of the Lamon- Doherty from Columbia University. "We find that they were caused by heavy and frequent La Nynes, a warm Atlantic ocean and a net increase in solar energy."
The study also shows that the risk of future megadons in the American Southwest is increasing due to climate change. Why is this? During the medieval megadons, the increased energy from the sun, of course, was caused by the natural climate variability. Today, however, the world is experiencing increased dryness in many places due to man-made climate change, which sets the foundations for increasing the probability of intermediate raw materials in the future by greater dryness, researchers say. (dryness), in the future when you have a large La Nina, or several of them in a row, this could lead to intermediate plains in the American West, "said Steiger.
An expert who does not participate in the study praises the work: "The new thing here is that they really put the pieces in a way that was not done before," said Connie Woodhouse, a University of Arizona climatologist for National Geographic.
The study was published on Wednesday in
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