Humans have caused 1.5 °C of long-term global warming according to new estimates

Then we'll only have just eliminated air pollution that kills millions of people per year and established independent energy security

Air pollution and CO2 emissions are different things. One causes cancer and heart issues, the other causes global warming.

Large amounts of particulate in the air (for example from a volcano) would probably cause global cooling since it blocks out the sun.

Right, fossil fuels cause around 8 million deaths a year from air pollution [1], so regardless of climate change it'd be worth making a dent in those numbers.

And no, air pollution isn't just a problem in places like India and China, it kills over 100,000 Americans a year and costs society $886 billion. [2]

The evidence of anthropogenic global warming existing is extraordinarily strong [3] [4], but you're right, even if somehow 97% of climate scientists with studies published on the matter from 1991 to 2011 and 99% of them from 2012 to 2020 were wrong (in addition to NASA, The European Space Agency, NOAA, the World Meteorological Organization, and the national academy of science (or equivalent organization) of basically every country that has one), it'd still be worth avoiding millions of deaths a year and having established independent energy security.

1. https://www.bmj.com/content/383/bmj-2023-077784

2. https://www.pnas.org/doi/10.1073/pnas.1816102116

3. https://dx.doi.org/10.1088/1748-9326/8/2/024024

4. https://doi.org/10.1088%2F1748-9326%2Fac2966

What you're saying is correct, but I can't think of many scenarios where it's relevant to human actions in the present, with the exception of freight ships' sulfur emissions. [1]

For the most part, burning fossil fuels is leading to both air pollution and GHG emissions. Sometimes you can in theory choose an option that leads to less global warming than the status quo but is worse for human health (e.g. burning biomass for energy instead of natural gas, or using diesel instead of gasoline engines), but usually there's an another option where you can reduce both undesirable outcomes (wind, solar, hydro or nuclear energy, electric vehicles, etc.)

Even from an economic standpoint I can't think of too many scenarios where clean energy isn't the better option long-term. An EV will have a higher up-front cost but definitely will be cheaper than a diesel vehicle across it's lifetime, and most areas I imagine solar or wind would be cheaper than biomass. Freight ships are the only thing in 2024 where I think we don't have an option that's better in both regards and cheaper -- there we do have to choose between more global warming or more particulate matter harmful for human health. But I think that's the exception more than the rule for human activities.

1. https://www.scientificamerican.com/article/cleaned-up-shippi...

Would spending 100 trillion dollars that we don't have cause more deaths than it prevents, due to increased poverty and rising cost of living? That's all I'm really asking here. Has anyone bothered to run the numbers?

Subsidies for oil, coal and natural gas currently cost us about 7.1% of global GDP. [1]

I imagine if we were willing to spend 2 to 5% of global GDP on fighting climate change, we'd also be cutting those subsidies. So in that scenario we'd be reducing government deficits and reducing the rate at which we print money, not increasing it.

1. https://www.imf.org/en/Blogs/Articles/2023/08/24/fossil-fuel...

I agree on ending the subsidies, that's fine. But the US alone spends over $2T more each year than it earns. Oil/gas subsidies in the US are a tiny fraction of that sum.