I actually think this could work with one important adjustment.
We should probably start with the people who think that killing off large portions of the population is a great idea and stop once we run out of those people.
Thanos was fucking stupid and no amount of "cold logic" bullshit will justify the fact that unlimited cosmic power could have just doubled the universe.
Or just the fact that achieving space farring tech in effect makes you a post scarcity civilization.
Thanos wasn't called Mad because his people deemed his ideas too radical, it was because even the premise of his plan was based on him being as dumb as a sack of rocks.
Neither addresses the problem, they just both push it into the future. Half the population/double the resources isn't even a reasonable amount to give much more time. It's better for drama though, because disappearing 99% or more of the universe would have really set back the Avengers, if any of them made the cut at all.
Good answer! Nuking ruins valuable resources, like plants that help reduce greenhouse gases, and animals that help ecosystems thrive.
What we need is some sort of pandemic, that targets the especially stupid (refusing to take protectionary precautions, idiotically increasing their risk of exposure). It's hard to go without also catching people with comorbidities in the net, but acceptable losses, I guess.
(attempting to answer the question instead of shaming the questioner)
It might have helped solve the problem if we did it 50 or 60 years ago, along with global EMP strikes to disable all the vehicles and industrial equipment, and a global commitment to return to an agrarian low-energy lifestyle. And if you prioritized the most highly industrialized cities that produce the greatest carbon per capita. But the sad truth is that, right now, it's already too late. We have already released so much carbon into the atmosphere that we are more or less guaranteed to see 4 degrees C above pre-industrial. And if you aren't already retired you will probably see it in your lifetime. Along the way that triggers a series of cascading feedback loops which, all-told, will likely take the planet to about 10C above pre-industrial. We continue to release something like 40 billion metric tons per year. And the best CCS facility we have, in Iceland, can sequester about 4,000 tons per year. We are racing toward the cliff with the throttle at full speed and no corrupt government scientist is going to take away my truck or make me eat bugs.
And questions about who should die, who should be killed, and such don't even really matter now. They sound immoral, but if the projections are right it looks like all of us who aren't already old are going to die from climate change anyways. So pontificating on things that aren't ever going to happen is just academic onanism.
Logically, killing humans would be way down on the list of potential Global Warming solutions. We would have to exhaust all other methods first. Just banning private vehicles would save a few billion from extermination. Green energy tech and Nuclear power would save more. Vegetarian diets even more. Reducing organic waste, involuntary birth control, carbon sequestration - it's a long list of better incremental solutions. They may be more costly than extermination, but they're infinitely more ethical. It's only logical if that's the sole solution that ensures some of the population survives. We're a long way from that condition.
I almost hesitate to bring up the other problems with your plan since, obviously the total monstrosity of it. But that's anyway pretty well covered so I'll just throw in that blowing enough nukes to kill that many people would create considerably worse environmental disaster
I mean, nuking? That ain't exactly going to fix anything.
Like, the whole idea is bad, but dropping nukes is it's own environmental disaster as bad or worse than global warming.
Even using conventional munitions is going to cause fires and literal megatons of debris to be released into the atmosphere and water. This ain't going to fix anything.
It also assumes that population control is the fix in the first place, and it isn't. The population levels would only shift the speed of change, not the fact of it. To stop or reverse the changes, you have to change the underlying cause of the change, which is pretty much down to industrial processes across multiple areas, including agriculture.
Yeah, you kill off enough people, industrial efforts might cease, but it's more likely that the remaining people are going to have to rely on the most effective methods to stay alive and functional, rather than the methods that are environmentally best.