Ice age climate analysis reduces worst-case warming expected from rising CO₂

[Jim__]

From phys.org

The left panel shows the sea surface temperature map during the most recent ice age, 21,000 years ago, compared to modern preindustrial temperatures. This new, more detailed analysis shows that the strong cooling over the northern oceans, caused by the North American ice sheet, contributed substantially to total global cooling. The right panel shows that the warming of the ocean's surface expected under future doubling of atmospheric CO2 displays a different pattern of temperature change, with a lower expectation for globally averaged warming than previous worst-case estimates. Credit: Science Advances (2024). DOI: 10.1126/sciadv.adk9461
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As carbon dioxide accumulates in the atmosphere, the Earth will get hotter. But exactly how much warming will result from a certain increase in CO2 is under study. The relationship between CO2 and warming, known as climate sensitivity, determines what future we should expect as CO2 levels continue to climb.

New research led by the University of Washington analyzes the most recent ice age, when a large swath of North America was covered in ice, to better understand the relationship between CO2 and global temperature. It finds that while most future warming estimates remain unchanged, the absolute worst-case scenario is unlikely.

The open-access study was published April 17 in Science Advances.

"The main contribution from our study is narrowing the estimate of climate sensitivity, improving our ability to make future warming projections," said lead author Vince Cooper, a UW doctoral student in atmospheric sciences. "By looking at how much colder Earth was in the ancient past with lower levels of greenhouse gases, we can estimate how much warmer the current climate will get with higher levels of greenhouse gases."

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