FACT BRIEF

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

Friday, July 30, 2021

By Howard Lee

Copy link

Copy featured image

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

This fact brief is responsive to conversations such as this one.

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

ABOUT THE CONTRIBUTOR

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.

FACT BRIEF BY

Latest fact briefs

About fact briefs published on Gigafact

Fact briefs are short, credibly sourced summaries that offer “yes/no” answers in response to claims found online. They rely on publicly available, often primary source data and documents. Fact briefs are created by contributors to Gigafact —a nonprofit project looking to expand participation in fact-checking and protect the democratic process. See all fact briefs here.