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This is Scientific American's 60-second Science, I'm Julia Rosen.
How much colder was it at the peak of the last ice age? That's a question scientists have been trying to answer for decades. And now they have a new best guess: 11 degrees Fahrenheit.
That's a lot, especially considering it's a global average. Parts of North America were much colder.
"First of all, large areas of the northeast were completely under ice. So that would have been pretty chilly; you wouldn't be living there. But even here in the west, right, where we weren't covered by an ice sheet, it would have been something like 20 degrees Fahrenheit lower."
Jessica Tierney, a paleoclimatologist at the University of Arizona. Tierney and her colleagues spent years compiling information about Earth's climate at the height of the last glacial period, about 20,000 years ago.
"We obviously don't have thermometers in the glacial period, so we have to instead look for these kinds of stand-in indicators."
One kind of stand-in is plankton that lived in the ocean and got preserved in marine sediments. Scientists use these fossils to infer past ocean temperatures by studying changes in the chemistry of their shells and in the kinds of fats and other compounds they produced.
Tierney and her team then combined these data with a climate model to give a full picture of glacial conditions.
"It's actually a technique used every day in weather forecasting. What's new is we're using it for the past, not the future. So we are actually, you know, hindcasting, if you will, rather than forecasting."
The study is in the journal Nature.

The findings suggest that the last ice age was significantly colder than scientists thought. And that matters today.
"The reason that we want to know how cold the last ice age is, beyond the fact that it's just a cool thing to know, is that we can actually use it to understand a quantity called climate sensitivity."
Climate sensitivity is a measure of how much the planet warms in response to rising greenhouse gases. In this long-ago case, we know how much carbon dioxide concentrations increased between the last ice age and preindustrial period from air bubbles trapped in ancient ice. And now we have Tierney's new results on the temperature difference between glacial and interglacial conditions. Together, these data suggest that low-end estimates of climate sensitivity—in which greenhouse gases don't cause much warming—are unlikely to be correct.
"If we had low climate sensitivity, then we would be less worried, you know, about what all the CO2 emissions are going to do. And so we can kind of rule that possibility out—you know, I suppose that's not great news."
Thanks for listening for Scientific American's 60-second Science, I'm Julia Rosen.

参考译文

这里是科学美国人——60秒科学系列，我是朱莉娅·罗森1n6,cChAdUd.EcO5Y。
在上一个冰河世纪的顶峰时期，气温比现在低多少？这是科学家数十年来一直试图回答的问题S;k.VX|7HO5E。现在他们有了新的最佳猜测：11华氏度6@u5-*mv1|I1A。
温度相差很多，尤其是考虑到这是全球平均水平OFz&ex7d9%afrYk&4。北美部分地区要冷得多PytJlP=mMDm3e。
“首先，东北部大片地区完全被冰覆盖IOXW2%[aP2p;ZJ%#)zi。所以会相当寒冷；人们不会住在那里.E(-~Ay3CM+2。但即使在未被冰层覆盖的西部，气温也会低20华氏度左右RYiCPt8QT5wj。”
亚利桑那大学的古气候学家杰西卡·蒂尔尼说到f9oyrn_fiSPQV9iP0zn。蒂尔尼和同事花费数年汇编了大约2万年前最后一次冰河时期高峰时的地球气候信息SZD2*0U]F+~V350ts3I。
“显然，在冰川时期我们没有温度计，因此我们必须寻找这些替代指示器Vegwnz3x)plI6YK_。”
其中一种替代物是生活在海洋中并保存在海洋沉积物中的浮游生物k%teL6hPfK,h0I_oZpL。科学家利用这些化石，通过研究它们外壳中化学物质、脂肪类型以及它们产生的其他合物的变化，来推断过去海洋的温度r,5RjMW;dP&y。
随后，蒂尔尼和团队将这些数据与气候模型结合起来，提供了冰川环境的全貌fN1l%QAvPSEdL@。
“这实际上是一种每天都在天气预报中使用的技术]t9ird[L~NJ+jvrTL-T&。不同的是，我们用它来推断过去，而不是预测未来qn0=|O0Iw4z~bS9oIT。可以说，我们实际上是在后报，而不是预测cj,vOp5fjY。“
这项研究发表在《自然》期刊上,6q82mWb^9。
研究结果表明，上一个冰河时期比科学家想象的要冷得多k)q_;PBRUN[。这在今天很重要.F,4Uh@Xg*4o(q11c。
“我们想知道上一个冰河期有多冷，除了知道这点会很酷以外，还因为我们可以用它来理解一个被称为气候敏感性的量ew,Eo|0~N%u。”
气候敏感性是衡量地球因温室气体增加而变暖程度的指标Ct.AxUSgx(4Bd_@。在这个很久以前的例子中，通过冻在古代冰块中的气泡，我们知道在最后一个冰河时期和前工业化时期之间，二氧化碳的浓度增加了多少+-m8rlMQhWw。现在我们还掌握了蒂尔尼关于冰期和间冰期之间的温差研究的新结果G~p,apzI18Yx|@)0VSn。总之，这些数据表明，对气候敏感性的低端估计——即温室气体不会导致严重变暖——不太可能是正确的NJW-%oK31;*GYdF(。
“如果我们对气候的敏感性较低，那我们就不会那么担心所有二氧化碳排放会造成什么后果-xD3c].-!0Qzwl4。因此，我们基本上可以排除这种可能性，这不是什么好消息;;~lI#mFQ#k%o0njG~mS。”
谢谢大家收听科学美国人——60秒科学系列，我是朱莉娅·罗森lNyvj(!E]XC)EYxn1。

译文为可可英语翻译，未经授权请勿转载！

重点讲解

重点讲解：
1. rather than 而非；胜于；而不是；
The decision was based on emotion rather than rational thought.
这个决定不是基于理性的思考而是基于感情作出的-%dY0m3s##PBA]6)moY5。
2. in response to 回复；回答；回应；
Sudan even threatened to mobilize in response to the ultimatums.
作为对最后通牒的回应，苏丹甚至威胁说要动员军队P!mEm1_K1^E^.j-mln。
3. be unlikely to do sth. 不太可能的；未必会发生的；
The job is unlikely to be finished inside a year.
这项工作不大可能在一年之内完成5_GF#Mv7]0。
4. rule out 排除；不予考虑；
They didn't rule out coalition with the Social Democrats.
他们不排除与社会民主党人结盟的可能性UZ_;kf;cZ,,。

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