Ya I think that we'll fail to make any measurable impact on global warming in our lifetimes, because it's much easier to sabotage movements than to invest in th

Ya I think that we'll fail to make any measurable impact on global warming in our lifetimes, because it's much easier to sabotage movements than to invest in them. So we'll inevitably reach for a solution that's a sure thing, and the only one I know of that's scalable is a 1-10 atom thick sunshield at the L1 Lagrange point. It's a problem similar in scope to a light sail, so there's no mystery to it other than trying to grow the dang thing in space. So if Earth gets a sunshield, it's no more difficult to grow one for Venus. Then eclipsing it and getting it to room temperature would only take a matter of weeks maybe? That would reduce the atmospheric pressure too. Seems like an orders of magnitude easier problem than waiting around for Mars to warm up and pressurize. Although on that note, we could build a giant reflector at the L2 point behind Mars to have room temperature immediately there too. Looks like a solar sail can be as light as 0.00002 kg/m2, the Earth has a cross section of about 125 million km2, or 1.25e14 m2, so that's 2.5 billion kg or 2.5 million metric tons. Of course there's always a way to make a thinner sail, and we may not need to block all of the light, so I think a million metric tons is a reasonable estimate. Sounds like a lot, but a locomotive is 1000 metric tons, so 1000 train engines or 10,000 heavy launches to save Earth doesn't seem unreasonable. Also we probably only need 1% of that area to have a measurable effect on climate, and that way we wouldn't have to see the shadow either. So we're talking 10 train engines or 100 heavy launches. https://en.wikipedia.org/wiki/Solar_sail#Materials https://en.wikipedia.org/wiki/Solar_sail#Materials