ScienceDaily: Nearly 34 million years ago, Earth underwent a transformation from a warm, high-carbon dioxide "greenhouse" state to a lower-CO2, variable climate similar to the modern "icehouse" world. Massive ice sheets grew across the Antarctic continent, major animal groups shifted, and ocean temperatures decreased by as much as 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...