The word "uncertainty" has become a bit of a bugaboo in green circles, since it’s typically used by skeptics to muddy the waters on climate science. But uncertainty around climate science is not the only relevant kind when it comes to global warming.

There’s also uncertainty with regard to how much it will cost to do something about it.

It seems to me this is woefully under-discussed. Virtually all public discussion of climate change has to do with the science — whether global warming is real, how fast it’s happening, the effects on sea levels, weather patterns, species, etc. The assumption seems to be that if we can nail down the science, policy will automatically follow.

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Not so.

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Consider: Steve Hayward cited an allegedly widely-held estimate that stabilizing global CO2 emissions at current levels will cost $37 trillion.

That’s huge. It’s enormous. Not global economic suicide, but not pretty either. We’re not just talking about people giving up luxury SUVs. A figure like that represents widespread human suffering. If it was a choice between the globe warming by 1.4 degrees (the low-end estimate) and taking a $37 trillion hit, well … it’s certainly not an easy or obvious decision.

Other more optimistic folks think developing energy efficiency, clean energy, smart grids, and greener cities would, in the aggregate, boost the world economy, once you factor in better health, stabilized or lowered populations, saner weather, and a decrease in resource conflicts. If that’s true — if slowing or stopping global warming would be a net benefit to the world’s economies — then who the hell cares about lingering uncertainty in the science, right? It’s worth doing on its own merits.

And here’s the rub: It could be argued that the economics are harder to nail down than the science.

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There’s plenty of complexity involved with global climate, but at least there are some basic patterns following some basic physical laws. There are lots of known knowns and known unknowns, to use Rumsfeldian language. Predicting the economic impact of fundamentally changing the way human societies power themselves … you’ve got to consider technological innovation, exact resource levels (peak oil, etc.), domestic politics in dozens of countries, international geopolitics, sociology, psychology, the exact effect of various forcings, the interplay of adaptation and mitigation … it’s endless. There are many, many unknown unknowns. I basically don’t trust any prediction of the total cost.

But without a way to judge how much it will cost, how can we make a rational decision about how to proceed?

I suspect, in the end, we can’t, and won’t. Events will play out according to chance and contingency, like usual. We’re just along for the ride. Hang on!