Thanks to shrinking sea ice, National Geographic puts global warming on the map

arctic-sea-ice-ponds-flickr-nasa7Every once in awhile, we reach a moment in history that so radically changes our concept of the world it forces us to redraw our maps — events like Columbus rediscovering America or the Soviet Union collapsing. Now we can add global warming to the list.

For the upcoming 10th edition of the National Geographic Atlas of the World, its cartographers say they have made one of the most visible changes in the publication’s history: it’ll show a lot less Arctic ice.

The loss of Arctic sea ice has been a glaring sign of climate change for the last thirty-some years. Rising temperatures have caused the ice to retreat by 12 percent per decade since the 1970s, with particularly notable setbacks in 2007 and 2012. Arctic sea ice is so responsive to climate change because of a positive feedback loop: As the ice melts it gets thinner, and because thin ice reflects less sun than thick ice, the ocean absorbs more of that heat – which weakens the ice even more.

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