How much money do you think the United States has spent since 1945 on the Cold War? Sometimes they ask this question then from the back of the audience comes in answer ‘billions and billions‘. A huge underestimate – billions and billions. The amount of money that the United States has spent on the Cold War since 1945 is approximately 10 trillion dollars. Trillion, that’s the big one with the ‘T’. What could you buy with 10 trillion dollars? The answer is: You could buy everything in the United States except the land. Everything. Every building, truck, bus, car, boat, plane, pencil, baby’s diaper. Everything in the United States except the land, that’s what we have spent on the Cold War.

So, now let me ask: How certain was it that the Russians were going to invade? Was it 100% certain? Guess not since they never invaded. What if it was only let say 10% certain? What would advocates of big military buildup have said? We must be prudent. It’s not enough to count on only the most likely circumstance. If the worst happens and it’s really extremely dangerous for us we have to prepare for that. Remote contingencies if there is serious enough have the prepared for. It’s classic military thinking – you prepare for the worst case.

And so now, I ask my friends who are comfortable with that argument, including the editorial page of the Wall Street Journal, why doesn’t that same argument apply to Global Warming. You don’t think it’s 100% likely? Fine. You are entitled to think that. If it’s only a small probability of it happening since the consequences are so serious, don’t you have to make some serious investment to prevent it or mitigate it? I think there’s a double standard of argument working and I don’t think we should permit it.

— Carl Sagan, An excerpt of a speech given on the 2nd of September in 1990 at the 5th Emerging Issues Forum at NCSU