Geoengineering is such a dangerous (both morally and in terms of its possible consequences) approach that it shouldn't seriously be considered as an option.

Cfr. [1] for its possible consequences in Asia and Africa:

   Both tropical and Arctic SO2 injection would disrupt the Asian and African
   summer monsoons, reducing precipitation to the food supply for billions of people.
   These regional climate anomalies are but one of many
   reasons that argue against the implementation of this kind of geoengineering.

[1]: http://climate.envsci.rutgers.edu/pdf/GeoengineeringJGR9inPr...