The European Commission has a helpful article on the benefits of geoengineering. It can help buy time for society to reduce CO2 emissions, but it's not a panacea. This article is based on the Lenton and Vaughn paper, which ranks geoengineering techniques -- however it's important to note that the paper is an open-access article that is still undergoing peer review. The rankings may change, and they also don't take into account all of the factors needed to decide between techniques (such as cost and environmental efffects).