Avoiding global warming impacts is a game of chance. And the dice are increasingly loaded for nasty outcomes as the stock of warming gases accumulates in the atmosphere. Already the planet has warmed, on average, about 0.8 degrees Celsius since the onset of the industrial revolution. Another 0.3–0.6 degrees of warming is already built-in to the planet but not yet measured by thermometers because the planet's big oceans are slow to warm. Because human and technological systems are slow to change, even a crash program to regulate emissions probably wouldn't prevent another 0.5–0.7 degrees of warming on top of the warming already built into the planet. I'll call this total – 1.6–2.1 degrees – the inevitable warming. That's bad news not just for the planet but also for the posse of diplomats that trot the globe signing communiqués claiming their goal is to stop warming at 2 degrees. The hard truth is that after two decades of dithering, the 2 degree goal is probably already history.

This chapter is about how to brace for the large impacts that will accompany large changes in climate. I look at two kinds of impacts: those that are easy to predict and highly likely and those that are a lot harder to pin down. In my view, the really big dangers with warming lie in the latter variety. They lie way out in the “tails” of the probability distributions.