# Pascal’s Wager And Global Climate Change: Hedging Your Bet When the Cost of Error is Too High

Pascal’s Wager And Global Climate Change: Hedging Your Bet When the Cost of Error is Too High
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Blaise Pascal was a brilliant 17th century French philosopher. Rather than try to prove the existence of God, he chose instead to prove to skeptics why they should believe in the existence of God and live their lives as if God existed, even without proof. He constructed the now-famous Pascal’s Wager, probably the first use of modern decision analysis. We can start with his argument, and apply it to the current debate about Global Warming and Global Climate Change. Like Pascal, I cannot prove the existence of Climate Change. But just like Pascal, I believe that I can prove that you should act as if it is real. Indeed, I show that the only reason for acting as if human-driven Climate Change is not real is if you believe we are doomed anyway; in that case, ignore Climate Change and enjoy civilization while it lasts.

Pascal’s argument is really simple:

If God exists and you bet that He does not, your penalty relative to betting correctly is enormous. If God does not exist and you bet that He does, your penalty relative to betting correctly is inconsequential. So, without additional information, you should always bet that God exists.

My argument is almost identical to his and just as simple.

If Climate Change exists and you bet that it does not, your penalty and the penalty of all of human civilization, relative to betting correctly, is enormous. If Climate Change does not exist and you bet that it does, your penalty relative to betting correctly is inconsequential. So, without additional information, you should always bet that Climate Change exists.[1]

Let’s start with Pascal’s original wager, on how to bet on the existence of God. Note that under the rules of Pascal’s Wager, you have to place your bet on whether God exists now, before you actually know. Note also that the payoffs are massively skewed. If God exists, you really want to bet correctly, to avoid an eternity of hellfire and damnation! If God does not exist, betting correctly is less important; if you bet incorrectly, you have lived a good life, admired by all around you. The only cost is a perhaps few missed opportunities for drinking, gambling, and fornication.

How does this analysis apply to Climate Change? Once again, we don’t need to know if Climate Change is occurring.[2] But once again, we need to place our bet on whether we believe it is occurring now, before we know if Climate Change truly exists. Pascal’s analysis can guide us here.

Following Pascal’s lead, we construct our wager and look at the payoffs. And once again, the payoffs are massively skewed. We reach the same conclusions that we reach in Pascal’s original framing of his Wager.

Climate Change Exists: If Climate Change does exist, the benefits of betting that it exists and believing, and living as if you believed, are truly massive. If we bet that Climate Change is real and it is, we incur the cost of self-restraint. We end up altering our driving habits, or setting the air conditioners to slightly higher temperatures until we figure out how to generate electricity with less carbon emissions. There is only a small change in the value of our lives. And we do get to continue human civilization much as we know it. In contrast, if Climate Change is real, and we bet against it, the cost of catastrophic floods of coastal regions, of droughts in the most fertile and most populous countries on earth, and of the resulting international armed conflicts over water, dry land, and food could potentially end civilization as we know it. That is an infinite loss, in some ways comparable to Pascal’s threat of eternal damnation. So if Climate Change is real and we bet correctly, the gains are infinite compared to betting incorrectly.

Climate Change Does Not Exist: If Climate Change is a hoax, but we bet incorrectly and act as if it were real, the cost to us is pretty small. We “wasted” a little bit of self-restraint.[3] The relative cost, compared to life as we live it now, is a small one. Alternatively, if Climate Change is a hoax and we ignore it and bet correctly, we avoid the wasted cost of self-restraint and continue our lives unchanged. That is, we preserve our base case, and there is no loss at all compared to life as we know it now. But the difference between the two payoffs in this case is quite small. So the cost of betting Climate Change is real is pretty small, even if Climate Change is actually not real; this is similar to the original Pascal’s Wager.

So the only way to really lose is to bet against the existence of Climate Change if it is real. None of the other combinations of “bet” and “truth” are really costly at all.

Why would you ever bet against the existence of Climate Change, when the rewards are so skewed? With even a tiny chance that Climate Change is real, that tiny chance, times the infinite loss of betting against it, has to outweigh the small cost of betting on Climate Change’s existence when there is no Climate Change.

To refuse to protect against Climate Change, one has to believe that the likelihood that Climate Change exists is truly zero.[4] Alternatively, to bet against Climate Change one has to believe that Climate Change would be truly benign. This year’s hurricane season suggests that, sadly, Climate Change is not going to be benign.[5]

What is the only logical choice here? If the cost of Climate Change is enormous, and the cost of remediation is manageable, there is only one choice. It’s not about being fair to America in some commercial struggle with China or India, especially when they have agreed that the cost of remediation is manageable. It’s about being fair to our children — American, Chinese, Indian, and everyone else’s — and betting that Climate Change could be real and must be addressed. If Climate Change turns out to be real, then the long-term cost of ignoring Climate Change is likely to be far higher than any short-term savings from ignoring it.

We are not proving that Climate Change exists, or that human-induced Climate Change exists, any more than Pascal proved the existence of God. But we are proving that with what we know now, we should act as if Climate Change exists. Pascal’s Wager has been around for more than three centuries. If we get the Climate Change Wager right, people will be around to worry about Pascal’s Wager for centuries to come.

[1] Not surprisingly, I am not the first person to compare Pascal’s Wager to the analysis of Climate Change. See How to bet on climate change for an early example.

[2] Increasingly, there is consensus that increased atmospheric carbon increases temperature and alters the climate, and increasingly there are statistical analyses that confirm that increased atmospheric carbon is already producing some of the predicted climate changes. It is not necessary that you understand the physics or wade through the statistical analyses to examine this Wager. This Wager represents the minimalist, “most conservative” framing of the argument for acting as if Climate Change is real, and the framing is equally valid whether or not you believe Climate Change has already begun. It is merely necessary that you assume that carbon-related Climate Change is at least possible, and that it would be painful.

[3] Of course, there may be benefits as well, like the development of profitable new technologies. But the framing of the Wager I am presenting here is once again as conservative as possible.

[4] The most sophisticated deniers accept that Climate Change is real, but deny any human responsibility. Their argument is, essentially, (1) Earth is in a period of interglacial warming. Earth has been warming since the Last Glacial Maximum (LGM) of about 16,500 years ago, and will continue to do so. (2) This warming has nothing to do with human activity of any kind, and (3) it will continue no matter what humans do. (4) The last century may have been the warmest since the LGM, but there have always been variations and this most recent variation has nothing to do with humans either. (5) The rate of warming has increased since the Industrial Revolution and the resulting release of atmospheric carbon, and has done so in precisely the way predicted by climate scientists, but this is coincidence and has nothing to do with human activity. (6) In short nothing humans do will make Climate Change more extreme or make it occur faster, and nothing that humans do will make it less extreme or make it occur more slowly. My response is maybe. That could indeed be possible. But refusing to believe that (2) through (5) could be false is quite a stretch. And as long as there is any ambiguity about (2) through (5) the Climate Change Wager remains unchanged. Of course, fully accepting (1) through (6) means that human civilization has a limited future, and we should enjoy what we have while we can.

[5] No professional meteorologist or climatologist can tell you which power plant caused which hurricane, just as no physician or epidemiologist can tell you which cigarette caused which cancer. But no physician or epidemiologist would deny the relationship between smoking and cancer. Likewise, no professional meteorologist or climatologist would deny the fact that warmer waters produce more frequent and more violent hurricanes. That does not imply that Climate Change is real, and that the oceans are truly getting warmer. But it does suggest that if Climate Change is real, the combination of higher sea levels and more violent hurricanes is going to be very costly.

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