Foreboding environmental milestones abounded again this year in the Arctic, where experts say dramatic climate shifts are fundamentally altering the ecosystem and how it operates. One recent turning ...

Arctic tundra, which has stored carbon for thousands of years, has now become a source of planet-warming pollution. As wildfires increase and hotter temperatures melt long-frozen ground, the region is ...

The news that the frigid Arctic tundra ringing the polar region has switched from being a net absorber, or "sink," of planet-warming greenhouse gases to a net emitter, or "source," indicates the ...

Add Yahoo as a preferred source to see more of our stories on Google. A polar bear (Ursus maritimus) swimming beside a melting iceberg in Naujaat, Nunavut. (Paul Souders/Getty Images) The Arctic is a ...