WHY IT MATTERS: Issues at stake in election - Article Photos 1/40

FILE - This Sept. 16, 2012, image released by NASA shows the amount of summer sea ice in the Arctic, at center in white, and the 1979 to 2000 average extent for the day shown, with the yellow line. Scientists say sea ice in the Arctic shrank to an all-time low of 1.32 million square miles on Sept. 16, smashing old records for the critical climate indicator. Yet there are two people who aren’t talking about it, and they both happen to be running for president. (AP Photo/U.S. National Snow and Ice Data Center, File)