How low did it go? Scientists calculate Earth's Ice Age temperatures
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[August 27, 2020]
By Will Dunham
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.
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Fossilized bones of mammoths, one of the large mammals that roamed
North America during the last Ice Age, are displayed at the Mammoth
Site where numerous mammoth fossils have been excavated in Hot
Springs, South Dakota, U.S. August 31, 2018. REUTERS/Will Dunham
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."
(Reporting by Will Dunham; Editing by Sandra Maler)
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