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The year 2005 has been the hottest year on record for the planet, hotter than 1998, 2002, 2004, and 2003. More importantly, perhaps, this has been the autumn when the planet has shown more clearly than before just what that extra heat means. Consider just a few of the findings published in the major scientific journals during the last three months:
—Arctic sea ice is melting fast. There was 20 percent less of it than normal this summer, and as Dr. Mark Serreze, one of the researchers from Colorado's National Snow and Ice Data Center, told reporters, "the feeling is we are reaching a tipping point or threshold beyond which sea ice will not recover." That is particularly bad news because it creates a potent feedback effect: instead of blinding white ice that bounces sunlight back into space, there is now open blue water that soaks up the sun's heat, amplifying the melting process.
—In the tundra of Siberia, other researchers report that permafrost has begun to melt rapidly, and, as it does, formerly frozen methane—which, like the more prevalent carbon dioxide, acts as a heat-trapping "greenhouse gas"—is escaping into the atmosphere. In some places last winter, the methane bubbled up so steadily that puddles of standing water couldn't freeze even in the depths of the Russian winter.
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