> Y is better than X, because we end up with a more verdant Earth, cheaper food, better weather, less war (insert reason here). The problem is that while it's

> Y is better than X, because we end up with a more verdant Earth, cheaper food, better weather, less war (insert reason here). The problem is that while it's easy to calculate exactly how much less CO2 car A emits than car B, it is close to impossible to use science to predict to any useful degree of accuracy how much cheaper the food, better the weather, or less of the war we will get. It's often hard to even predict the sign, not even trying to determine the magnitude. This means that when scientists or politicians tell you that "we need to do X, so that we get Y", they're very often fooling you, because they have no good idea how much (if any) Y you get for each unit of X.