Greenhouse gas emissions, particularly those from carbon dioxide, are on the rise. They have been for a while, to the alarm of governments, activist groups, and just about anyone vaguely concerned with environmental issues around the world. Greenhouse gases get their name because they have properties that make them act like glass in a greenhouse, keeping energy from the sun concentrated in our atmosphere, causing temperatures to rise. But until now, that particular effect hadn't been observed and documented in the scientific literature. Now, it has.