Yes, billions.

Via Paul R. Ehrlich (Standford.edu):

Is it ironic or predictable that Harvard’s President, Drew Faust, would enter into a Faustian bargain over climate change and the University’s investments in carbon-intensive companies?

Let’s suppose that, by pure chance, it turns out that there is a 90% probability that the climate denier campaign paid for or organized by those companies is correct – that human caused climate disruption is not occurring (or if it is it is inconsequential). History shows that the consensus of several thousand honest scientists working in any area can be dead wrong (near universal opposition to Wegener’s idea of continental drift was an example in my lifetime).

Suppose there were only a 10% probability that business as usual would bring about global climate disruption sufficient to cause the deaths of billions and misery for survivors. What, if anything, should or would society do about it?

Looking at how other risks are handled can give us a clue. Your odds of having a house fire are way under 1%, and those of having your house burn down entirely are less than one in a hundred thousand. Yet most people choose to have fire insurance. The lifetime odds of dying in an airplane accident are about one in five thousand, yet many people are afraid of flying and/or take out trip life insurance.