The Unforgiving Math For Staying Under 2 Degrees

In the Paris accord, 195 countries agreed that they would collectively keep average global temperatures from rising more than 2 degrees. But what does science have to say on actually keeping that goal? And how fast, and by how much, will we have to cut our emissions to get there? Professor Kevin Anderson of the Tyndall Centre is a climate scientist who looks at exactly this question. And the math he comes away with, isn't pretty.