For the upcoming issue, I got to interview Michael E Mann, the director of the Earth System Science Center at Pennsylvania State University and one of the researchers behind the famed hockey stick graph.  I asked him if there’s a new piece of evidence for climate change that he finds particularly compelling. He said he couldn’t pick just one because he sees new, compelling evidence almost every day.

And as it happens, I’m looking through the science news last night, and sure enough, I come across a story about how almost all of Greenland’s surface ice vanished over four days in July.


From the NASA website:

For several days this month, Greenland’s surface ice cover melted over a larger area than at any time in more than 30 years of satellite observations. Nearly the entire ice cover of Greenland, from its thin, low-lying coastal edges to its two-mile-thick center, experienced some degree of melting at its surface, according to measurements from three independent satellites analyzed by NASA and university scientists.

On average in the summer, about half of the surface of Greenland’s ice sheet naturally melts. At high elevations, most of that melt water quickly refreezes in place. Near the coast, some of the melt water is retained by the ice sheet and the rest is lost to the ocean. But this year the extent of ice melting at or near the surface jumped dramatically. According to satellite data, an estimated 97 percent of the ice sheet surface thawed at some point in mid-July.

And here’s a pic of that melt. On the left, a July 8, 2012 satellite image. On the right, one from July 12, 2012. White is surface ice, light pink is probable melt, dark pink is actual melt.

And in case you think this is just some kind of data error, the melt has been confirmed by three satellites.