So PhysicsWorld has done a nice article on some of the 'engineering' solutions that might be available for tackling global warming.
Generally they are pretty ambitious global-scale plans to turn down the thermostat a bit, given the premise that either carbon dioxide emissions will not fall sufficiently or that, even if they did, the earth would still be too hot and something else will be needed. They fall into a few categories. First, there is the CO2-vac. Suck up that excess carbon dioxide using whatever technology you can make work. Secondly there is control of the earth's surface. This might mean things like planting crops / forests that are a little more reflective to sunlight than current crops. And thirdly, there is control of the amount of sunlight that hits earth.
I'll comment specifically on the third one, which, in my opinion, is the most ridiculous. Controlling sunlight might be done, for example, by putting dust into the upper atmosphere, just like the effect from a large volcanic eruption. Less sunlight gets through, which means less heating. Or there is control of the whiteness (reflectiveness) of clouds. Apparently, if we add sea-salt to clouds it makes them whiter (I wonder whether washing powders do the same thing...) And for those that really want to push the boundaries of plausibility, we could launch a spacecraft that unfurls a three million square kilometre sunshade about a thousand kilometres above the earth.
What concerns me with some of these approaches is that we need to be very very very sure we get it right. Do we understand the earth's climate and associated processes sufficiently? What if the sunshade in space results in some unanticipated and very undesired effect? Can we undo this meddling on an astrophysical scale? I can't help thinking it's like introducing stoats into New Zealand to control the growth in rabbits. An immediate and devastating effect on the kiwi population.
Moreover, to put up a giant sunshade is surely going to require worldwide political agreement on a unprecedented scale. Surely if two hundred and something countries can all agree on that, getting them to act to actually reduce substantially the amount of carbon dioxide that is pumped out should be a piece of cake.
Anyway, have a read of the article and decide for yourself. What I find very interesting is the reader-submitted comments that follow it.