Not saying it's a good idea, but geoengineering is currently both technically and economically feasible. It would be easy for e.g. the United States to reduce t

Not saying it's a good idea, but geoengineering is currently both technically and economically feasible. It would be easy for e.g. the United States to reduce the total incoming sunlight by enough to counteract global warming. The issue is that doing so will have widespread unknown issues on the planet. For example- launching enough thin, reflective mylar film to the Earth-Sun L1 Lagrange point to reduce incoming solar radiation by ~0.1% would take about 500 Falcon Heavy launches (highest capacity rocket currently available). This would take several years and around $100 billion. Once Starship is ready and in use, this would go way down. $100 billion and several years is practically nothing for the US, China, or one of several other countries with the capability to do this. Obvious downsides include denying the use of the L1 Lagrange point to human use permanently, eventual degradation of the sun shield as solar wind pushes pieces of film out of place, and of course possible mass famine and plant die-off due to lower solar radiation.