Snakes Tell A Torrid Tale

摘要

The discovery in Colombia of a giant species of fossil snake is news in itself. But a wider, more controversial inference to be drawn is that tropical climate in the past was not buffered from global warming. As the world uneasily eyes a warmer future, a large community of researchers is investigating the past for the insights it might provide into the likely magnitude of climatic and ecological change. Time intervals in Earth's past, such as the early Palaeogene (between 65 million and 40 million years ago), are known to have been much warmer than today. The presence of fossil crocodiles and palm trees ringing the Arctic and in the hinterlands of Wyoming and Siberia, combined with quantitative records of palaeoclimate, indicate above-freezing winter conditions and annual average temperatures in these regions that were often at least 15 ℃. But if the extratropics were this warm, how hot were the tropics? Head et al. (page 715 of this issue) provide tantalizing clues from an unusual source.