Paedar Kirby: Amid the widespread welcome for the Paris Agreement, what is striking is the lack of consensus on just how significant it all is. James Hansen, former head of the NASA Goddard Institute for Space Studies in New York and regarded as one of the world’s most eminent climate scientists, went so far as to call it “a fraud, a fake, worthless words” while Cara Augustenborg, chair of Friends of the Earth Ireland, said in Paris that “the gap between ambition and action in the deal is too big.” So should we welcome or denounce this long-awaited global treaty?