New York Times: When President Obama barged into a meeting of leaders from China, India, Brazil and other major emerging economies at a climate-change summit in Copenhagen in December 2009, he managed to extract a last-minute agreement to set a goal to limit the rise in global temperatures. It was the high-water mark of Mr. Obamas leadership on climate change even if the deal was less than the Americans or Europeans wanted and it has been downhill ever since. Preoccupied with other problems, the president...