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

By Howard Lee
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NO

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.

See a full discussion of this at Skeptical Science
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Sources
Earth and Planetary Science Letters Late Paleozoic Ice Age glaciers shaped East Antarctica landscape
Nature Climate, p CO2 and terrestrial carbon cycle linkages during late Palaeozoic glacial–interglacial cycles
Annual Reviews Extra An Atlas of Phanerozoic Paleogeographic Maps: Plate Tectonics Pgeog & Ice
Nature Future climate forcing potentially without precedent in the last 420 million years
Science An astronomically dated record of Earth’s climate and its predictability over the last 66 million years
Annual Reviews Atmospheric CO2 over the Past 66 Million Years from Marine Archives
Palaeo-CO2 CO2 in the geological past
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Skeptical Science
Skeptical Science is a non-profit science education organization. Our goal is to remove a roadblock to climate action by building public resilience against climate misinformation. We achieve this by publishing debunking of climate myths as well as providing resources for educators, communicators, scientists, and the general public. Skeptical Science was founded and is led by John Cook, a Senior Research Fellow with the Melbourne Centre for Behaviour Change at the University of Melbourne.
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