The best bet at present is that polar oceans warmed to the point where methane clathrates (frozen balls of methane, which look like ice but ignite if you put a match to them) suddenly melted, releasing large amounts of methane, a greenhouse gas even more powerful than carbon dioxide. That would have heated things up very fast. If this story is correct, we need to keep a very wary eye on methane clathrates in today’s polar oceans. After a climatic spike lasting perhaps two hundred thousand
