Does using the mortality cost of carbon make reducing emissions comparable with health interventions?

Ben

Context

A while back Hauke compared the effectiveness of work on climate compared to global development interventions, and wrote this post. After realising an error in the first version of the model, he reversed his initial conclusions and wrote the title that global development is generally more effective. But as he recognises in the updated introduction, some commenters identify that it's more that the confidence intervals are overlapping. Then I found this interesting paper with a different take on mortality and emissions, so I thought I'd play with the figures to see what happens.

Summary, limitations, and implications

In the workings below, I find that under baseline and realistic assumptions, it costs around $1,200 to save a life by averting carbon emissions versus $3,400 through GiveWell's health interventions. This means some work on climate change could be more effective than GiveWell's top health interventions.

Workings

I just came across this paper The Mortality Cost of Carbon by Danny Bressler,

In a baseline emissions scenario, the 2020 MCC is 2.35x10^-4 excess deaths per metric ton of 2020 emissions.

This implies that 1/0.000235 = 4,255 tons of carbon produce harm enough to reduce global health by one life in expectations. GiveWell estimates that it costs $3,373 to save a life.

Comparing this with Founders Pledge's report, if we take their lower-ranked charity (because the uncertainty range is narrower), the expected cost benefit of future projects is given below, along with the cost to avert 4,255 tonnes.

Future pessimistic - $5.50 per tonne, so $23,400 to avert 4,255 tons
Future realistic - $0.29 per tonne, so $1,234 to avert 4,255 tons
Future optimistic - $0.03 per tonnes, so $127 to avert 4,255 tons

So if this is correct, it costs $3,373 to save a life via Malaria Consortium, as recommended by GiveWell, but $1,234 to save a life through abating emissions under their realistic scenario. Am I missing something here?

Limitations and implications

I realise one limitation here is that Danny's paper looks at 2020-2100, which may be a different time period to GiveWell which I expect to be benefiting people within the next decade.

But I think this is useful in expanding a broader conversation about climate change as a bridging cause, which links up both present-concern global development and also longtermism.

This also excludes the harms of air pollution, energy poverty, and ignores broader effects, e.g. astronomical stakes.

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DannyBresslerSep 24 202011

FYI, I gave a presentation on my Mortality Cost of Carbon paper at the UCLA Climate Adaptation conference two days ago, available here: https://event.on24.com/wcc/r/2688287/118B1E2E57B33A902FDE6CE95202DB34 This is a brief (~20 minutes) less technical overview of the paper. My presentation starts at 53:20.

Also, the other two speakers on the panel (Tamma Carleton and Ishan Nath) were both authors on the Climate Impact Lab paper that Louis had posted about earlier: https://forum.effectivealtruism.org/posts/PATHShQoxQLHoZ7rE/linkpost-global-death-rate-from-rising-temperatures-to

My Mortality Cost of Carbon working paper is here: https://ceep.columbia.edu/sites/default/files/content/papers/n11.pdf

ShayBenMosheSep 26 20207

At some point I tried to estimate this too and got similar results. This raised several of points:

I am not sure what the mortality cost of carbon actually measures:
1. I believe that the cost of additional ton of carbon depends on the amount of total carbon released already (for example in a 1C warming scenario, it is probably very different than in a 3.5C warming scenario).
2. The carbon and its effect will stay there and affect people for some unknown time (could be indefinitely, could be until we capture it, or until we got extinct, or some other option). This could highly alter the result, depending on the time span you use.
The solutions offered by top charities of GiveWell are highly scalable. I think the same can not be said about CATF, and perhaps about CfRN as well. Therefore, if you want to compare global dev to climate change, it might be better to compare to something which can absorb at least hundreds of millions of dollars yearly. (That said, it is of course still a fair comparison to compare CATF to a specific GiveWell recommended charity.)
The confidence interval you get (and that I got) is big. In your case it spans 2 order of magnitude, and this does not take into account the uncertainty in the mortality cost of carbon. I imagine that if we followed the previous point and used something larger for comparison, the $/carbon will have higher confidence. However, I believe that the first point at least indicates that the mortality cost of carbon will have a very large confidence interval.
This is in contrast with the confidence interval in GiveWell's estimates, which is (if I recall correctly) much narrower.

I would love to hear any responses to these points (in particular, I guess there are some concrete answers to the first point, which will also shed light on the confidence interval of mortality cost of carbon).

To conclude, I personally believe that climate change interventions could save lives at a cost similar to that of global dev interventions, but I also believe that the confidence interval for those will be much much higher.