CNN: Four months and 1,300 miles ago, Erlend Moster Knudsen started running. Starting line: Arctic Norway. Destination: a U.N. climate change summit in Paris. I met the aerobically inclined climate scientist on the road last week in northern France. He ran (he is on his fourth pair of shoes) while I biked behind him, struggling to keep up. Freezing rain and snow pelted our faces as we traveled past misty fields, tile-roofed villages and Edward Scissorhands shrubbery. The whole thing was exhausting,...