最後一個冰期的氣溫到底有多低？ zt

華盛頓（路透社）-在海洋浮遊生物化石和氣候模型的指導下，科學家們計算出在上一個冰河世紀的深度期間，地球上的冰冷程度，當時冰蓋覆蓋了北美，南美，歐洲和亞洲的大部分地區。

研究人員在周三表示，在大約23,000至19,000年前的最後一次冰河最高時期，全球平均溫度約為46華氏度（7.8攝氏度），比2019年低13華氏度（7攝氏度）。

他們發現，某些地區比全球平均溫度低很多。極地地區的冷卻遠遠超過熱帶地區，北極地區的華氏溫度比全球平均水平低25華氏度（14攝氏度）。

研究人員借助化學測量對浮遊動物的微小化石和其他類型的浮遊生物中保存的脂肪結構進行了計算，這些浮遊生物的脂肪會隨著水溫的變化而變化-他們稱之為“溫度代理”。

然後將此信息插入氣候模型模擬中，以計算全球平均溫度。

亞利桑那大學古氣候學家傑西卡·蒂爾尼（Jessica Tierney）表示：“過去的氣候是我們掌握的有關地球在很大程度上變冷或變暖時真正發生的情況的唯一信息。因此，通過研究它們，我們可以更好地約束未來的期望。”該研究的作者發表在《自然》雜誌上。

在大約115,000至11,000年前的冰河時期，大型哺乳動物非常適應寒冷的氣候，例如猛ma象，乳齒蜥蜴，羊毛犀牛和劍齒貓在周圍漫遊。

人類在冰河時期首次進入北美，穿過一座陸橋，該橋曾經將西伯利亞與阿拉斯加連接起來，海平麵比今天低得多。

人們認為，在冰河時代末期，人類狩獵已導致全球許多物種的大規模滅絕。

蒂爾尼說：“有趣的是，阿拉斯加並未完全被冰覆蓋。” “有一條無冰的走廊，使人類能夠穿越白令海峽進入阿拉斯加。阿拉斯加中部實際上並不比今天冷得多，因此對於冰河世紀的人類來說，這可能是一個相對不錯的住所。”

 

WASHINGTON (Reuters) - Guided by ocean plankton fossils and climate models, scientists have calculated just how cold it got on Earth during the depths of the last Ice Age, when immense ice sheets covered large parts of North America, South America, Europe and Asia.

The average global temperature during the period known as the Last Glacial Maximum from roughly 23,000 to 19,000 years ago was about 46 degrees Fahrenheit (7.8 degrees Celsius), some 13 degrees Fahrenheit (7 Celsius) colder than 2019, the researchers said on Wednesday.

Certain regions were much cooler than the global average, they found. The polar regions cooled far more than the tropics, with the Arctic region 25 degrees Fahrenheit (14 degree Celsius) colder than the global average.

 

The researchers made their calculations with the aid of chemical measurements on tiny fossils of zooplankton and the preserved structures of fats from other types of plankton that change in response to water temperature - what they called a "temperature proxy."

This information was then plugged into climate model simulations to calculate average global temperatures.

"Past climates are the only information we have about what really happens when the Earth cools or warms to a large degree. So by studying them, we can better constrain what to expect in the future," said University of Arizona paleoclimatologist Jessica Tierney, lead author of the research published in the journal Nature.

During the Ice Age, which lasted from about 115,000 to 11,000 years ago, large mammals well adapted to a cold climate such as the mammoths, mastodons, woolly rhinos and saber-toothed cats roamed the landscape.

Humans entered North America for the first time during the Ice Age, crossing a land bridge that once connected Siberia to Alaska with sea levels much lower than they are today.

Human hunting is believed to have contributed to mass extinctions globally of many species at the end of the Ice Age.

"What is interesting is that Alaska was not entirely covered with ice," Tierney said. "There was an ice-free corridor that allowed humans to travel across the Bering Strait, into Alaska. Central Alaska was actually not that much colder than today, so for Ice Age humans it might have been a relatively nice place to settle."