Fossil plants and global warming at the Triassic-Jurassic boundary

The Triassic-Jurassic boundary marks a major faunal mass extinction, but re cords of accompanying environmental changes are Limited. Paleobotanical evi dence indicates a fourfold increase in atmospheric carbon dioxide concentra tion and suggests an associated 3 degrees to 4 degrees C "greenhouse" warmi ng across the boundary. These environmental conditions are calculated to ha ve raised leaf temperatures above a highly conserved Lethal Limit, perhaps contributing to the >95 percent species-level turnover of Triassic-Jurassic megaflora.