Wired has an interesting article about how it is theoretically possible to reverse global warming on a short term basis, but the solution likely isn't worth it.

Two professors claim that increasing temperature change could be counteracted by blocking sunlight by introducing small particles into the atmosphere, but as soon as this Band-Aid is ripped off, the temperature would rise must faster.

It is nice to know that we might be able to avert a global emergency using technology, but avoiding the crisis altogether through sustainable living is a much wiser course of action.

However, the idea of atmospheric engineering could be adapter to more local needs, such as trying to prevent glaciers from melting or spurring rainstorms for areas that are in drought.