VOA慢速英语2020--研究人员计算出了上一次冰河时期地球表面的温度

Researchers Estimate Earth’s Temperatures During Ice Age

Scientists say they have calculated temperatures on Earth's surface during the last Ice Age.

The researchers made their calculations with the help of fossilized remains¹ of ocean plankton² and models of climates tens of thousands of years ago in different parts of the world.

The researchers reported their findings in the British scientific publication Nature.

The most recent Ice Age lasted from about 115,000 to 11,000 years ago. During this time, huge sheets of ice covered much of North America, South America, Europe and Asia.

The researchers said the average temperature worldwide during the height of this period, known as the Last Glacial Maximum, was about 7.8 degrees Celsius³. That average Ice Age temperature was about 6 degrees Celsius colder than the average today. The average world temperature during the 20th century was 14 Celsius, the scientists noted⁴.

Some areas were much colder than the average, they found. Extreme northern and southern regions cooled far more than other areas, with the Arctic region 14 degrees Celsius colder than the world average.

"We have a lot of data about this time period because it has been studied for so long," said Jessica Tierney in a statement. "But one question science has long wanted answers to is simple: How cold was the Ice Age?"

Tierney helped lead the study. She is a paleoclimatologist with the University of Arizona.

Tierney said that looking at information from past climates is the only way to find out what truly happens when the Earth experiences long cold or warm periods. "So, by studying them, we can better constrain⁵ what to expect in the future," she said.

During the Ice Age, our planet was home to large mammals such as mammoths, mastodons, woolly rhinoceros⁶ and saber-toothed cats. These animals were able to survive in a cold climate.

Early 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.

"What is interesting is that Alaska was not entirely⁷ 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 relatively⁸ nice place to settle."

Human hunting is believed to have been partly responsible for many Earth species disappearing at the end of the Ice Age.

Atmospheric⁹ carbon dioxide levels during the Ice Age were about 180 parts per million, which is very low, the researchers said. Before the Industrial Revolution of the 1800s, levels rose to about 280 parts per million. Today they are about 415 parts per million.

The researchers announced plans to use their temperature calculation methods to recreate warm periods in Earth's history.

"If we can reconstruct past warm climates, then we can start to answer important questions about how the Earth reacts to really high carbon dioxide levels..." Tierney said. This can help scientists expand their understanding of what future climate change might bring.

I'm Bryan Lynn.

Words in This Story

calculate – v. to discover an amount or number using mathematics

constrain – v. to control something by limiting it

mammal – n. an animal that feeds its babies on milk from its body

corridor – n. a passageway between two points

allow – v. to permit

species – n. a group of animals or plants that are similar and can produce young animals or plants

1 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

2 plankton   

n.浮游生物

参考例句：

• Plankton is at the bottom of the marine food chain.浮游生物处于海洋食物链的最底层。
• The plankton in the sea feeds many kinds of animals. 海的浮游生物成为很多种动物的食物。

3 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

4 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

5 constrain   

vt.限制，约束；克制，抑制

参考例句：

• She tried to constrain herself from a cough in class.上课时她竭力忍住不咳嗽。
• The study will examine the factors which constrain local economic growth.这项研究将考查抑制当地经济发展的因素。

6 rhinoceros   

n.犀牛

参考例句：

• The rhinoceros has one horn on its nose.犀牛鼻子上有一个角。
• The body of the rhinoceros likes a cattle and the head likes a triangle.犀牛的形体像牛，头呈三角形。

7 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。

8 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

9 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。