https://www.econlib.org/library/Columns/y2018/MurphyNordhaus.html
This is an old post about ways to estimate the economic impact of climate change and the ways it can fought. It's mostly about trying to find the 'price of carbon dioxide' that is optimal, that is, to internalize the externalities and make everyone pay it to the government (go figure).
The interesting part here is that one of the most respected (and used) models sees the difference between doing nothing at all and enacting the optimal tax over the next hundred years at around 3 trillion dollar, which is also about the size of the market capitalization of the largest companies in the world (apple, nvidia, msft).
I was reminded of this when I saw the price of the wars in Iraq and Afghanistan: At least according to the following link, it's in the same ballpark at around 4 to 6 trillion dollars.
No "conclusion" here, but I find it interesting to get a perspective on these things.
