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.
Edit, it became reality:
Even if the US and EU pony up the not insignificant amount of cash to do it, there’s still nothing that can put 1000t into orbit, let alone L1. And splitting it up into 100t segments isn’t a solution, since L1 is unstable. The segments will need power, thrusters, gyros, propellant and guidance for station-keeping, so there goes a large chunk of your mass budget. To compensate for that, you need more mirrors. And they need to be continuously replaced as they break down or run out of propellant.
actually solar wind and electric charging of the rotating foil should do the trick. The gravitational effects around L1 are miniscule. If you are e.g. 1km away from L1 then it is less than 0,001% of earths gravity. The touch of a butterfly could literaly move the mirror.