‘…500 gigatons is a lot, but we\u2019re producing more than 30 gigatons a year as a planet, and that number has been growing about 3 percent a year. Which gives us, oh, about 15 years before we go soaring past the two-degree threshold. If we are to avoid doing that, computer modeling shows that the world\u2019s carbon emissions have to peak in 2015 and then come hurtling down.’<\/p>\n