I've been wondering about that. There's many options. What we call global warming is a 0.015% change in albedo for the planet, due to what is effectively a color change of the atmosphere. But we can change the planet's albedo artificially easily enough. In fact, nature has been doing that for at least 4 billion years. How much do we need to change?
Forests have an albedo of 13%.
Grasslands have an albedo of 20%.
Deserts have an albedo of 36%.
Ocean surface: 6%.
We can artificially create surfaces with an albedo north of 99.9% (99% reflective in visible and UV light). In fact we could create solar panels with an albedo of 83%, which would actually be more efficient than current solar panels.
Makes sense, doesn't it? The whole point of grass, trees, ... is to absorb as much visible and UV light as possible, without becoming too impractical. So forests REALLY pull in heat, almost as much as asphalt.
Cutting down forests, to replace them with nothing, undoes Global warming for (20%-13%)/0.015% or 500 times the area deforested. All 150 years of global warming. If you cut down all plants, 1500 times.
So we could simply destroy cut down 1 million sq. km of forest, about 2.5% of all forests (or simply prevent global warming from forming new huge forests, undoing the last 20 years of forest growth, which would be a lot gentler). Or, we could REALLY cut it down and only do 0.8% (changing forests into deserts) or we could cover 100.000 sq km with a real reflective material.
If we cover Iceland in an artificial white surface, or Iceland and change in those better solar panels that would not just stop, but undo climate change. Hell, we'd have to be very careful about how quickly we do that, or it would hit us like a bomb.
We could cut down 20% of the forests (everything BUT the rainforest for example) of Brazil.
But this seems to me the best way:
1) get people to make 83% reflective solar panels
2) install them slowly. Mandate new solar panel installations to have 80% or more albedo. Ideally cutting down new forests created by global warming to install them.
Even if we just waste the electricity they generate. At the current rates of solar installations that would undo global warming in 3 or so years, and would spread things out, which seems like it would be a good thing. 3 years seems much too fast though, it would have to be slowed down a lot.
And covering water, especially ocean, surfaces in solar panels should have an incredible effect on global warming.
