Environment: Cloudy Crystal Balls

Climatologists regularly issue confident warnings about impending atmospheric disasters. The secret of their wizardry: sophisticated computer models, which are no more than mathematical representations of the world's climate and the conditions that scientists think may contribute to a specific phenomenon like, say, ozone depletion. Unfortunately, when all the variables are fed into the computer, the predictions can fail miserably to match reality.

Take the Antarctic ozone hole, for example. Before it was discovered, climate modelers trying to simulate ozone loss in the atmosphere had not yet factored in the presence of ice clouds in the Antarctic stratosphere. Thus their models failed...