Was there an ice age in the Earth’s past when CO2 was 3000ppm?

Friday, July 30, 2021
By Howard Lee

There was an ice age around 290 to 340 million years ago during the Paleozoic, but CO2 was relatively low, at about 390ppm. A supercontinent at the South Pole, major mountain building, massive carbon burial in sediments (forming coal), along with a 3% dimmer sun back then, contributed to the low CO2 and cold climate.

Data spanning more than 400 million years show that climate and CO2 levels vary together. During ice ages, CO2 levels were low, and during warm periods, CO2 was higher. For example, in the hot Eocene around 40 to 56 million years ago, there were no polar ice caps, temperatures were about 10ºC hotter than in the 20th century, and CO2 was about 1,500ppm. In contrast, during the last Ice Age, CO2 varied between about 180 and 300ppm, close to Paleozoic Ice Age levels, as ice sheets waxed and waned with orbital wobbles.

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