Settled science: When CO2 levels dropped around 34 million years ago, temperatures on land didn't change, or they cooled by eight degrees, or something

Terrestrial climate change linked to shift in atmospheric CO2

Nearly thirty-four million years ago, the Earth underwent a transformation from a warm and high-carbon dioxide "greenhouse" state to a lower-CO2, variable climate of the modern "icehouse" world.

Massive ice sheets grew across the Antarctic continent, major animal groups shifted, and ocean temperatures decreased by up to 5 degrees.

But studies of how this drastic change affected temperatures on land have had mixed results. Some show no appreciable terrestrial climate change; others find cooling of up to 8 degrees and large changes in seasonality.