IT is a journalistic principle that the answer to a headline written in the form of a question is almost always “no,” but in this case, the answer, sadly, may very well be “yes.” That is the impression, at least, left by a new report released last week by the United Nations Environment Program (UNEP), which concluded that the world now has no chance of keeping global warming below 1.5 degrees Celsius over pre-industrial levels, and that this “climate overshoot”