Summit Voice: Some of the most compelling signs of global warming impacts continued to come from the Arctic in 2012, where sea ice extent reached a record low and Greenland experienced record surface melting last summer. Another worrying sign is the warming in permafrost regions, where significant thawing could release a new surge of heat-trapping greenhouse gases that would intensify warming. The average global temperature for the year was among the top-10 warmest on record, and other climate observations also...