"Some of the world’s richest nations are lagging behind on their climate protection pledges. Most often, these commitments follow the formula: “We aim to reduce greenhouse gas emissions X percent below year Y levels by year Z. It seems like a straightforward proposition, but have you ever wondered where those numbers come from? The answer is a scientific concept known as the carbon budget. In the video above, Kelly Levin, a climate policy expert at the World Resources Institute, explains what our carbon budget is, how much we’ve already “spent,” and why it matters. (Quoted from article)