At $35/kg, that would cost about $750 billion. More than Musk could do on his own anytime soon, but definitely feasible as a global effort. Each pound of metha

At $35/kg, that would cost about $750 billion. More than Musk could do on his own anytime soon, but definitely feasible as a global effort. Each pound of methane would produce 2.75 pounds of CO2: https://www.engineeringtoolbox.com/co2-emission-fuels-d_1085.html https://www.engineeringtoolbox.com/co2-emission-fuels-d_1085... And each launch burns 240 tonnes of methane (launch mass minus rocket mass is 1200 but that's 4/5 oxygen): https://en.wikipedia.org/wiki/SpaceX_Starship https://en.wikipedia.org/wiki/SpaceX_Starship So that's 660 tonnes CO2 per launch times about 150,000 launches, or about a hundred megatons CO2. Given that we're emitting 36GT annually, that seems a good trade. That's just launch to LEO, we need extra delta-v to L1, but potentially that could be from a fleet of solar-powered ion drive tugs. My quick google didn't turn up Starship payload capacity to L1. If the shades can be manufactured on the moon from local materials, potentially this could be a lot cheaper, with almost zero emissions. It'd take longer to get started, but it'll take a long time before people agree on something like this anyway; if we're setting up lunar manufacturing anyway, this would be something to keep in mind.