Climate Change

Scientists have figured out just how cold the last Ice Age was. Here's why it matters

Fossilized bones of mammoths, one of the large mammals that roamed North America in extremely low ice age temperature, are displayed at the Mammoth Site where numerous mammoth fossils have been excavated in Hot Springs, South Dakota, U.S. August 31, 2018. Picture taken August 31, 2018.  REUTERS/Will Dunham - RC2TLI9RYMXZ

The Last Glacial Maximum ended around 19,000 years ago. Image: Reuters/Will Dunham

Will Dunham
Journalist, Reuters
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  • Scientists have predicted that the global ice age temperature was around 46 degrees Fahrenheit (7.8 degrees Celsius), on average.
  • However, the polar regions were far colder, around 25 degrees Fahrenheit (14 degree Celsius) colder than the global average.
  • Studying past ice ages could help us understand our climate in the future.

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 skeleton of a mammoth, one of the large mammals that roamed North America during the last Ice Age, is displayed at the Mammoth Site where numerous mammoth fossils have been excavated in Hot Springs, South Dakota, U.S. August 31, 2018.
The skeleton of a mammoth, one of the large mammals that roamed North America during the last Ice Age. Image: REUTERS/Will Dunham

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.

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.

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