Half a Degree Makes a Big Difference for Global Climate

More than 150 countries are expected to sign the Paris Agreement, an accord reached last December designed to keep global warming “well below” 2 degrees Celsius by the end of the century, with some nations arguing that the world should rally around a more stringent threshold of 1.5 C. And the difference between the two goals might be significant: A new study shows that the world would look substantially different if mean global temperatures rise by 2 C, rather than 1.5 C.