" Declining emissions and rising atmospheric concentrations point to a stubborn fact about carbon dioxide: once it’s in the air, it stays there. How long, exactly, is a complicated question; for all intents and purposes, though, CO2 emissions are cumulative. The comparison that’s often made is to a bathtub. So long as the tap is running, a stoppered tub will continue to fill. Turn the tap down, and the tub will still keep filling, just more slowly. To "

― Elizabeth Kolbert , Under a White Sky: The Nature of the Future