美國西部將面臨氣候變化引發(fā)的“特大干旱”

研究顯示，美國西部將面臨氣候變化引發(fā)的“特大干旱”

A two-decade-long dry spell that has parched much of the western United States is turning into one of the deepest megadroughts in the region in more than 1,200 years, a new study found.

一項新的研究發(fā)現，美國西部長達20年的干旱期，正在變成1200多年來該地區(qū)最嚴重的一次大干旱。

And about half of this historic drought can be blamed on man-made global warming, according to a study in Thursday’s journal Science.

根據周四出版的《科學》雜志上的一項研究，這次歷史性的干旱大約有一半可以歸咎于人為的全球變暖。

Scientists looked at a nine-state area from Oregon and Wyoming down through California and New Mexico, plus a sliver of southwestern Montana and parts of northern Mexico. They used thousands of tree rings to compare a drought that started in 2000 and is still going — despite a wet 2019 — to four past megadroughts since the year 800.

科學家們觀察了從俄勒岡州和懷俄明州到加利福尼亞州和新墨西哥州的九個州，以及蒙大拿州西南部的一小部分地區(qū)和墨西哥北部的部分地區(qū)。他們使用了數千個樹的年輪來比較2000年開始的干旱和自800年以來持續(xù)了4次的特大干旱，盡管2019年陰雨連綿。

With soil moisture as the key measurement, they found only one other drought that was as big and was likely slightly bigger. That one started in 1575, just 10 years after St. Augustine, the first European city in the United States, was founded and that drought ended before the Pilgrims landed on Plymouth Rock in 1620.

以土壤濕度為主要測量指標，他們只發(fā)現了另一場同樣嚴重的干旱，而且可能更嚴重一些。這場旱災始于1575年，也就是美國第一個歐洲城市圣奧古斯丁(St. Augustine)建立10年后。1620年，清教徒在普利茅斯石(Plymouth Rock)登陸之前，旱災就結束了。

What’s happening now is “a drought bigger than what modern society has seen,” said study lead author A. Park Williams, a bioclimatologist at Columbia University.

現在發(fā)生的是“一場現代社會從未見過的干旱”，該研究的主要作者a . Park Williams說，他是哥倫比亞大學的生物氣象學家。

Daniel Swain, a UCLA climate scientist who wasn’t part of the study, called the research important because it provides evidence “that human-caused climate change transformed what might have otherwise been a moderate long-term drought into a severe event comparable to the ‘megadroughts’ of centuries past.”

沒有參與這項研究的加州大學洛杉磯分校氣候科學家丹尼爾·斯溫(Daniel Swain)稱這項研究很重要，因為它提供了證據，證明“人類造成的氣候變化將原本可能是一場溫和的長期干旱變成了一場堪比過去幾個世紀‘特大干旱’的嚴重事件。”

What’s happening is that a natural but moderate drought is being worsened by temperatures that are 2.9 degrees Fahrenheit (1.6 degrees Celsius) hotter than the past and that suck moisture out of the ground, Williams said. It’s much like how clothes and plants dry faster in the warmth of indoors than they do outside, he said.

Williams說，目前的情況是，由于氣溫比過去高2.9華氏度(1.6攝氏度)，并從地下吸走水分，一場自然但溫和的干旱正在加劇。他說，這就像衣服和植物在溫暖的室內比在室外干得更快一樣。

To quantify the role of global warming, researchers used 31 computer models to compare what’s happening now to what would happen in a mythical world without the burning of fossil fuels that spews billions of tons of heat-trapping gases. They found on average that 47 percent of the drought could be blamed on human-caused climate change.

為了量化全球變暖的影響，研究人員使用了31個計算機模型，來比較現在的情況和一個沒有燃燒化石燃料的虛構世界的情況?；剂蠒尫懦鰯凳畠|噸的溫室氣體。他們發(fā)現，平均47%的干旱可以歸咎于人類造成的氣候變化。

“We’ve been increasingly drifting into a world that’s getting dryer,” Williams said.

威廉姆斯說:“我們正日益滑向一個越來越干燥的世界。”