Because our world is warming rapidly all sorts of crazy ideas are coming out of the woodwork, even if the feasibility of them is dubious. The latest one is called the space umbrella. Basically, a giant space-based sunshade would cool our world as it would reduce the amount of sunlight reaching our planet. Only diverting 2 to 4% of the sun’s rays would turn back the clock to a pre-industrial age. At least, that is the theory.
Now, before you the reader scoff at this idea, it bears to understand that this scheme has high level support from the Royal Society to Nasa and the European Union.
If the concept is now mainstream, how to achieve this is still the stuff of fantasy. The shade would have to be deployed far in outer space, at a point called the L1 point, situated between the earth and the sun. The original design was a vast 2000 km-wide glass structure that would have been constructed on the moon. Other proposals include clouds of Moon dust, wire-mesh mirrors or tiny umbrellas. Of course, just getting the sunshade in space would be expensive. Or you could design something so lightweight that moving it into space would cost next to nothing.
Nevertheless, unforeseen events could mar this fantasy project. For one thing, the cooling effect would not be uniform everywhere as the tropics would be cooler and the high latitudes warmer. As well, the world would be drier, with 5% less rainfall on average.
One should add that this setting up of the sunshade would force countries to collaborate together, but this means that as some countries would experience more rainfall others would be more dry. This means a lot of political wrangling around those issues. In short, it could be that at some point, especially if the climate changes drastically, trying to set up a sun shade may be the lesser of two evils. At its best, it could force countries to cooperate more to achieve the end result. But determining which countries would suffer more and how to alleviate this would be hard to achieve. Major world bodies would have to get involve, with cash payments to those countries who would suffer the brunt of this sun-shade. Not for tomorrow is my guess, but perhaps in 100 years from now.