The net-present-value of 3.7C warming by 2100 has been estimated at $551 trillion:
I don’t know anything about that study, or how they arrived at their conclusions, but here is a survey of economists who specialize in this area.
When asked about the impact of a 3 degree increase by 2090, the median estimate was 5.5% and the mean estimate was 10.2% of GDP compared to a baseline scenario. In any case, the vast majority of estimates still imply substantially positive economic growth.
(1) the cost over millennial time scales isn’t predictable in any meaningful sense
Not that relevant, under any moderate discount rate means the cost over the next few decades is most important.
(2) the cost probably far exceeds our ability or willingness to pay
Like I said, most SCC estimates fall within $20-$200 or so. I don’t think that does or should exceed our willingness to pay. Whatever the true cost of climate change is, we should be willing to pay.
(3) whatever carbon price we do pay will just be paid to ourselves, not to the nations and future generations who will be most affected by climate change
Again though, a carbon price is not designed to make reparations; that isn’t the point. The point is to correct a negative externality so the market functions efficiently again.
(4) the cost of decarbonization — which should be our policy focus — is surely much lower than the cost of future damages from carbon emissions.
Well, decarbonization on what time-frame? William Nordhaus has made some estimates. For example, to keep warming at 2 degrees would take a carbon tax of around $130 — which is roughly in line with many SCC estimates (which vary widely)!
Do you really believe that the most optimal use of carbon pricing revenue is to return it to U.S. consumers whose per-capita emissions rate is three times the global average
Optimal from what perspective? I prefer a rebate/dividend structure, but mainly because I feel that will make a carbon tax more palatable to the general public. Whatever the economic merits of a carbon tax, we still have to find a way to get most people to accept it, or it will never be enacted.
In an ideal world, we could send funds to the areas of the world most affected by climate change, but running on a platform of “Tax Americans and send the money to Malaysia” isn’t likely to poll well.