The Economist: Predicting the climatic future is riddled with uncertainty
"The world's climate scientists are charged with a difficult task: to create a crystal ball with which to skry a future that promises to be hotter than today. But exactly how much hotter depends on innumerable factors, both natural and human. Creating the crystal ball is thus a two-stage process. First, you have to build a simulacrum of how Earth’s climate works. Then, you try to perturb this simulacrum with plausible future human actions, to see what picture appears."