I don’t think human psychology will allow a united approach to global warming. Too man people are too stupid, to egoistic or just in such a tight spot they can not afford being “climate-friendly”.
So I wonder if there are Mega-Projects available to stop global warming?
Some coming to mind:
Reflector mirror at Lagrange1 between Sun and Earth - even a 1.000.000km² mirror from ultrathin film would weigh 1000 tonnes at most.
Giant Air Scrubers and I mean giant. They would dwarf the pyramids and remove pullutants and CO² from the athmosphere.
In addition I think a originator principle should become common: Any nation not really trying to act clean should simply be burdened with massive tariff measures. Using modern technology it shouldn’t be too hard to find nations who polute the ocean unnececerrally.
I can comment on air scrubbers.
You don’t need those to be massive. In fact, a diminishing returns effects kicks in at about the size of a large building. You just need a lot of those. Preferably several in every somewhat large city, plus some more on the periphery.
But the current problem with this tech is it’s really energy intensive. So much so, that if you run it using fossil fuels, you’re scrubbing less CO2 than you release, and if you run it using renewable energy, you’re taking it away from other uses, and still end up with net positive CO2.
So the only reasonable way to do it at this stage is to run it using unexportable surplus clean energy, which none of the countries have at this point.