There is an idea that is keeping me up at night. What if we could launch large sails to the L1 Lagrange Point to reduce the amount of radiation that reach the earth by only 2% ?
The L1 between earth and the sun is only 1% of the way to the sun. So the sail would need to be 99% of the cross sectional area of the earth. If it was opaque (reflective) and you only wanted to block 2%, you'd need a 2.23 million square km sail (0.020.99Pi*6000^2)
Aluminium foil is about 2g/cm2. That's 3e-3 g/cm2. 3e-2 kg/m2. 30,000kg/km2.
You'd need 66 million tonnes of aluminium.
Maybe you can make it 100 times lighter with better materials? So only 600,000 tonnes.
I think about this often too. There are a ton of articles out there about it. It seems like it would require a pretty colossal amount of mass to get lifted into orbit, and then maintenance of a giant fleet of objects flying close together. Flock dynamics writ large. I've wondered if it would be easier to find an asteroid you can turn into sails (handwaving here about the difficulty of finding one, developing the technology to mine it & also spin up a space manufactory...) than it would be to make them all on earth. Who knows.
EDIT: I've sort of come to the conclusion that this is the only solution that a single-party could take on that would meaningfully decrease the amount of heat in the atmosphere. Everything else is dependent on a ton of other people doing what they need to do, too.
Thank you for the problems I am looking for them! I keep thinking we could manufacture and send the sails from the moon. This would require a semi-automated production line and I have no idea if this is even remotely possible with current technology.
I also think it is the only possible controllable way to control global warming. I am very happy to learn I am not the only one that thought of this.
Aluminium foil is about 2g/cm2. That's 3e-3 g/cm2. 3e-2 kg/m2. 30,000kg/km2.
You'd need 66 million tonnes of aluminium.
Maybe you can make it 100 times lighter with better materials? So only 600,000 tonnes.
https://en.wikipedia.org/wiki/Lagrange_point
Maybe if we'd gotten into asteroid mining 100 years earlier...