Scientific American: The Arctic wasn't always covered in ice. Samples of sediment layers beneath a frozen lake show this region used to be a lot warmerand may thaw out again in the future. The work is in the journal Science. El'gygytgyn, a Russian lake 100 kilometers north of the Arctic Circle, contains layers of sediment that date back to the lake's formation 3.6 million years ago. Analyses of sediment cores have revealed that back then summers reached about 15 to 16 degrees Celsius, a good 8 degrees warmer than modern...