美国西部将面临气候变化引发的“特大干旱”

研究显示，美国西部将面临气候变化引发的“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.

一项新的研究发现，美国西部长达20年的干旱期，正在变成1200多年来该地区最严重的一次大干旱。

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

根据周四出版的《科学》杂志上的一项研究，这次历史性的干旱大约有一半可以归咎于人为的全球变暖。

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.

科学家们观察了从俄勒冈州和怀俄明州到加利福尼亚州和新墨西哥州的九个州，以及蒙大拿州西南部的一小部分地区和墨西哥北部的部分地区。他们使用了数千个树的年轮来比较2000年开始的干旱和自800年以来持续了4次的特大干旱，尽管2019年阴雨连绵。

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.

以土壤湿度为主要测量指标，他们只发现了另一场同样严重的干旱，而且可能更严重一些。这场旱灾始于1575年，也就是美国第一个欧洲城市圣奥古斯丁(St. Augustine)建立10年后。1620年，清教徒在普利茅斯石(Plymouth Rock)登陆之前，旱灾就结束了。

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.

现在发生的是“一场现代社会从未见过的干旱”，该研究的主要作者a . Park Williams说，他是哥伦比亚大学的生物气象学家。

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.”

没有参与这项研究的加州大学洛杉矶分校气候科学家丹尼尔·斯温(Daniel Swain)称这项研究很重要，因为它提供了证据，证明“人类造成的气候变化将原本可能是一场温和的长期干旱变成了一场堪比过去几个世纪‘特大干旱’的严重事件。”

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说，目前的情况是，由于气温比过去高2.9华氏度(1.6摄氏度)，并从地下吸走水分，一场自然但温和的干旱正在加剧。他说，这就像衣服和植物在温暖的室内比在室外干得更快一样。

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.

为了量化全球变暖的影响，研究人员使用了31个计算机模型，来比较现在的情况和一个没有燃烧化石燃料的虚构世界的情况。化石燃料会释放出数十亿吨的温室气体。他们发现，平均47%的干旱可以归咎于人类造成的气候变化。

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

威廉姆斯说:“我们正日益滑向一个越来越干燥的世界。”