科学美国人60秒 SSS "绿色撒哈拉"的终结可能导致东南亚出现特大干旱（在线收听）

This is Scientific American's 60-second Science, I'm Christopher Intagliata.

这里是科学美国人——60秒科学系列，我是克里斯托弗·因塔格里塔。

Ten thousand years ago, the Sahara had extensive grasslands and was dotted with lakes and trees.

一万年前，撒哈拉拥有广阔的草原，遍布湖泊和树木。

But some 5,000 years ago, that "Green Sahara" dried up to become the enormous desert we know today.

但大约5000年前，“绿色撒哈拉”干涸成我们今天所知的巨大沙漠。

And scientists now think that this climate shift had effects far away—including causing a megadrought in Southeast Asia.

科学家现在认为，这种气候变化产生了深远的影响，包括在东南亚造成特大干旱。

Kathleen R. Johnson, a paleoclimatologist and geochemist at the University of California, Irvine,

凯瑟琳·R·约翰逊是加州大学欧文分校的古气候学家和地球化学家，

says the key to that discovery were stalagmites collected in a cave in northern Laos.

他表示，这一发现的关键是在老挝北部洞穴中收集的石笋。

"Stalagmites are really amazing archives of past climate variability.

“石笋非常神奇，它保留着过去气候变化的记录。

People are more familiar with things like tree rings and ice cores or ocean sediment cores.

人们更熟悉树木年轮、冰核或海洋沉积物核等东西。

Well, stalagmites work in a similar way, in that they're deposited over time."

石笋也以类似的方式工作，即随时间的推移而沉积。”

Johnson's team analyzed trace elements and carbon and oxygen isotopes in the hardened cave drippings.

约翰逊的团队分析了硬化洞穴水滴中的微量元素和碳氧同位素。

That information enables researchers to determine rainfall patterns over the millennia.

这些信息使研究人员能够确定几千年来的降雨模式。

And Johnson and colleagues discovered signs of a 1,000-year-long drought in Laos, which began around the same time the Sahara dried up—about 5,000 years ago.

约翰逊和同事发现了老挝长达1000的干旱迹象，这场干旱大约始于5000年前，与撒哈拉沙漠干涸的时间差不多。

As for why the two events might be connected?

至于为何这两个事件可能有关联？

The researchers simulated the drying out of the Sahara using climate models—

研究人员用气候模型模拟了撒哈拉干旱的过程，

and they included a couple things we know happened, including the subsequent disappearance of vegetation and a connected increase in airborne dust—

他们纳入了我们知道已经发生的两件事情，随后植被的消失和与之相关的空气中灰尘的增加，

and found those variables would have been capable of cooling down the Indian Ocean.

他们发现这些变量能使印度洋降温。

"And so those cooler ocean temperatures led to less moisture being brought by monsoon circulation in the summertime, when that region gets most of its rainfall."

“因此，海洋温度降低导致夏季季风环流带来的水分减少，而夏季正是该地区降雨量最多的时候。”

The details are in the journal Nature Communications.

研究详细信息发布在《自然通讯》期刊上。

One of Johnson's co-authors is Joyce White, a consulting scholar at the Penn Museum.

约翰逊的合著者之一是宾夕法尼亚博物馆的咨询学者乔伊斯·怀特。

She studies the human history of Southeast Asia. And her reaction when she first heard about the drought:

她研究东南亚人类史。她第一次听说这场干旱时的反应是：

"I said, 'Oh my God, that's the missing millennia.'"

“我说，‘哦，我的天哪，这是缺失的千年。'”

The "missing millennia" because she says archaeological data is scant in that part of Southeast Asia, from 4,000 to 6,000 years ago.

她称之为“缺失的千年”是因为，东南亚该地区4000至6000年前的考古资料缺失。

White says it's a critical period in which hunter-gatherers gave way to farmers.

怀特表示，那是狩猎-采集者让位给农民的关键时期。

"And there are a lot of debates about how the two periods related to each other,

“关于这两个时期相互关联的方式存在很多争论，

but we lacked the evidence in the area I'm most interested in, which is the Mekong Valley."

但在我最感兴趣的地区，即湄公河流域，我们缺乏证据。”

White says this study doesn't answer that question directly—

怀特表示，这项研究并没有直接回答这个问题，

but the megadrought is a tantalizing new clue for archaeologists as they continue to investigate those "missing millennia."

但对于考古学家来说，在他们继续调查“缺失的千年”时，这场特大干旱是诱人的新线索。

Thanks for listening for Scientific American's 60-second Science. I'm Christopher Intagliata.

谢谢大家收听科学美国人——60秒科学。我是克里斯托弗·因塔利亚塔。