Donald Trump and Al Gore would no doubt cringe at the thought that politically speaking, they are brothers from different mothers. After all, what do the Republican president and the Democratic presidential wannabe have in common besides the fact that they are both old, white, pompous dudes who live in mansions and hate Hillary Clinton? Whether they realize it or not, they both believe in the precautionary principle — the notion that even a small chance of a catastrophic event requires sweeping measures to avert it.