Burlington Free Press: Ripton environmentalist Bill McKibben delivered the keynote address at the March 16 Global Warming Conference in Montpelier. Excerpts: Last summer was very scary. By the time the summer was over, the Arctic had, in essence, melted. Eighty percent of the ice that was there 40 years ago is gone. Weve taken one of the largest physical features on Earth, and weve broken it. And thats not a good sign, when you start breaking your major physical features. Thats the pace at which things are happening....