Yesterday, Neil deGrasse Tyson shared the following tweet:
Earth needs a virtual country: #Rationalia, with a one-line Constitution: All policy shall be based on the weight of evidence— Neil deGrasse Tyson (@neiltyson) June 29, 2016
This tweet raises many questions, such as, WTF? However, I want to focus on one area of policy that Tyson surely has in mind, namely climate change.
I think we can all agree that the weight of evidence shows that climate change is real, underway, and dangerous.
Just kidding, we can’t agree on that. A bunch of us don’t agree on that at all.
But let’s say the types of people who don’t believe it are denied citizenship in Rationalia. Let’s say all Rationalians accept the basic scientific consensus on climate change.
Here are some questions for Tyson about climate policy in Rationalia.
1) How much does Rationalia care about future generations?
The models widely used to project damages from climate change determine the present value of future climate damages (the "social cost of carbon") by applying a discount rate.
Some models, like that of UK economist Nicholas Stern, apply a very low discount rate, implying that future damages are almost as important to us as present-day damages — and thus that we should take immediate, aggressive steps to prevent future climate change.
Other models, like that of Yale’s William Nordhaus, apply a higher discount rate, implying that future damages are worth much less to us than present-day damages — and thus that climate policy should start slow and gradually ramp up.
Which discount rate will Rationalia use in determining policy? And who will decide?
2) How much does Rationalia care about equity?
Cumulatively, developed nations like the US and the EU have emitted more carbon into the atmosphere than developing nations, and thus bear a greater share of responsibility for climate change. Yet it is the citizens of poorer and low-lying nations who stand to suffer first and worst from the impacts of climate change.
Some people say that this is a great historical injustice, that justice and equity should be at the heart of all future global climate policy — we should prioritize the welfare of developing nations, to compensate for the suffering that will be imposed on them by climate change.
Some people say that the potential welfare impacts of future climate change are so severe that speed and efficiency are the only morally acceptable guiding principles — we should prioritize reducing emissions as fast as possible, even if it means developing nations have to bear more of the cost than is fair.
Which will be prioritized in Rationalia, equity or efficiency? And who will decide?
3) How does Rationalia prioritize risks?
Scientists and policymakers broadly agree that humanity ought to avoid global warming of any more than 2 degrees Celsius over preindustrial levels.
We are currently on track to blow past that target. But even if we decide in earnest to hit it, we still need to decide how much risk to accept, and what kind of risk.
An emissions scenario that gives us a 25 percent chance of avoiding 2 degrees looks very, very different than an emissions scenario that gives us a 75 percent chance of avoiding 2 degrees.
Some people say the dislocations that would be entailed by the latter scenario, possibly including economic contraction, are too much to risk for an uncertain climate target.
Some people say that even 2 degrees of warming is too dreadful to contemplate, that it may trigger unstoppable, civilization-threatening additional warming, and that it’s worth literally any cost to avoid it.
How will Rationalia weigh the risks of socioeconomic dislocation against the risks of severe climate damages? And who will decide?
I look forward to hearing what the weight of evidence has to say on these matters.