I read through all the comments in this post:
https://forum.effectivealtruism.org/posts/nBN6NENeudd2uJBCQ
including Halstead's. And I found the counterarguments to Halstead's to be more persuasive. If I have time I can go back and highlight the specific ones, but I'd be interested in his response to the the responses to his comment.
You could ask him about the most concerning tipping points. He wrote: "some models suggest that if CO2 concentrations pass 1,200ppm (compared to 415ppm today), cloud feedbacks could cause 8ºC of additional warming over the course of years to decades, on top of the 5ºC we would already have experienced." Carbon Brief covered this topic: https://www.carbonbrief.org/extreme-co2-levels-could-trigger-clouds-tipping-point-and-8c-of-global-warming/
Thanks. Tipping points is a good question.
I asked climate Scientist, Zeke Hausfather - who Halstead cites in his work - on this too:
https://www.thendobetter.com/investing/2021/11/22/zeke-hausfather-state-of-climate-science-energy-systems-post-cop26-tipping-points-tail-risks-podcast
If you are interested.