(C) Social cost of carbon is usually computed from an IAM, a practice which has been described as such:
“IAMs can be misleading – and are inappropriate – as guides for policy, and yet they have been used by the government to estimate the social cost of carbon (SCC) and evaluate tax and abatement policies.” [Pindyck, 2017, The Use and Misuse of Models for Climate Policy]
In any case I think that picking a threshold (based on what exactly??) and doing whatever it takes to get there will have more problems than IAMs do.
I see that you use GWWC’s estimate of tonnes of CO2 per life saved. I critiqued GWWC’s approach in this previous post.
Nice, that looks like a good noteworthy post. I will look at it in more detail (would take a while). Until then I’m revising from 258,000 tons down to 40,000 (geometric mean of their estimate and your 15,620 but biased a little towards you).
“40% of Earth’s population lives in the tropics, with 50% projected by 2050 (State of the Tropics 2014) so we estimate 6 billion people affected (climate impacts will last for multiple generations).”—The world population is expected to be ~10 billion by 2050, so 50% would be 5 billion. How are you accounting for multiple generations?
I figured many people will be wealthy and industrialized enough to generally avoid serious direct impacts, so it wasn’t an estimate of how many people will live in warming tropical conditions. But looking at it now, I think that’s the wrong way to estimate it because of the ambiguity that you raise. I’m switching to all people potentially affected (12 billion), with a lower average QALY loss.
“We discount this to 2 billion to account for the meat eater problem”—What is the meat eater problem?
Described in “short-run, robust welfare” section of “issue weight metrics,” it’s the fact that increases in wealth for middle-income consumers may be net neutral or harmful in the short run because they increase their meat consumption.
“If each of them suffers −1 QALY over their lifetime from climate change on average”—why did you choose −1 QALY?
Subjective guess. Do you think it is too high or too low? Severely too high, severely too low?
Why did you choose to multiply 550 by ~3.9?
Arbitrary guess based on the quoted factors. Do you feel that is too low or too high.
I agree that this is a plausible possibility, but not one which I’d like to have to rely on.
I’m not saying to rely on it. I’m saying your estimates of climate damages cannot rely on geoengineering not happening. The chance that we see “full” geoengineering by 2100 (restoring the globe to optimal or preindustrial temperature levels) is, hmm 25%? Higher probability for less ambitious measures.
If we were in in the 1980s it would be improper to write a model which assumed that cheap renewable energy would never be developed.
Based on these changes I’ve increased the weight of air pollution from 15.2 to 16. (It’s not much because most of the weight comes from the long run damage, not the short run robust impacts. I’ve increased short run impact from 2.15 million QALYs to 3 million.)
You can also use economists’ subjective estimates ( https://policyintegrity.org/files/publications/ExpertConsensusReport.pdf ) or model cross validation ( https://www.rff.org/publications/working-papers/the-gdp-temperature-relationship-implications-for-climate-change-damages/ ) and the results are not dissimilar to the IAMs by Nordhaus and Howard & Sterner. (it’s 2-10% of GWP for about three degrees of warming regardless.)
In any case I think that picking a threshold (based on what exactly??) and doing whatever it takes to get there will have more problems than IAMs do.
Nice, that looks like a good noteworthy post. I will look at it in more detail (would take a while). Until then I’m revising from 258,000 tons down to 40,000 (geometric mean of their estimate and your 15,620 but biased a little towards you).
“40% of Earth’s population lives in the tropics, with 50% projected by 2050 (State of the Tropics 2014) so we estimate 6 billion people affected (climate impacts will last for multiple generations).”—The world population is expected to be ~10 billion by 2050, so 50% would be 5 billion. How are you accounting for multiple generations?
I figured many people will be wealthy and industrialized enough to generally avoid serious direct impacts, so it wasn’t an estimate of how many people will live in warming tropical conditions. But looking at it now, I think that’s the wrong way to estimate it because of the ambiguity that you raise. I’m switching to all people potentially affected (12 billion), with a lower average QALY loss.
Described in “short-run, robust welfare” section of “issue weight metrics,” it’s the fact that increases in wealth for middle-income consumers may be net neutral or harmful in the short run because they increase their meat consumption.
Subjective guess. Do you think it is too high or too low? Severely too high, severely too low?
Arbitrary guess based on the quoted factors. Do you feel that is too low or too high.
I’m not saying to rely on it. I’m saying your estimates of climate damages cannot rely on geoengineering not happening. The chance that we see “full” geoengineering by 2100 (restoring the globe to optimal or preindustrial temperature levels) is, hmm 25%? Higher probability for less ambitious measures.
If we were in in the 1980s it would be improper to write a model which assumed that cheap renewable energy would never be developed.
Based on these changes I’ve increased the weight of air pollution from 15.2 to 16. (It’s not much because most of the weight comes from the long run damage, not the short run robust impacts. I’ve increased short run impact from 2.15 million QALYs to 3 million.)
Yes I will look into that and update things accordingly.