According to an article published in the November 19, 1999, issue of the journal Science, a massive release of methane gas (CH4) may have caused global warming during the Paleocene Epoch 55 million years ago. The process began with a gradual atmospheric warming which sent warm currents of surface water down to the ocean floor. Solid methane, called methane hydrate, warmed and became gaseous. The gas escaped from the sediment, and reacted with oxygen to create carbon dioxide which subsequently rose into the atmosphere where it trapped heat. It is thought that this historic global warming, which caused sea temperatures to rise, killed off many deep sea creatures. At the same time, the rise in atmospheric temperature may have created conditions conducive for the evolution of mammals. The evidence for these findings came from close analysis of ocean floor sediment cores. The hypothesis may have profound implications for the current rise in atmospheric carbon dioxide and the potential for further release of trapped methane beneath the ocean floor. This week's In the News explores the current findings and the relevance of methane hydrate to global warming.