Today, rising carbon dioxide in the atmosphere is a cause for concern, but 2.7 billion years ago, high levels of CO2 probably kept our planet warm enough for life even though the sun was about 20% fainter than it is today.
A newly published study, based on analyses of ancient micrometeorites and a fresh round of computer modeling, estimates just how high those CO2 levels were. The likeliest level is somewhere in excess of 70% CO2, scientists from the University of Washington report today in the open-access journal Science Advances.
Based on the modeling, global mean temperatures would have been in the mid-80s Fahrenheit (roughly 30 degrees Celsius).
All that is good news for astrobiologists, because such an environment matches up well with the picture that scientists have of Earth during what’s known as the Archean Eon. The high CO2 levels wouldn’t be livable for us humans, but they’d be fine for the early organisms that ruled the Earth before oxygen levels rose.
The findings “could also inform our understanding of Earth-like exoplanets and their potential habitability,” said the study team, led by UW researcher Owen Lehmer.