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

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

1. 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.
2. 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.)
3. 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.