Many types of geo-engineering could in theory work to cool the planet. But none of the proposals I'm aware of will decrease the CO2 in the atmosphere. Without fixing that, we'll still have ocean acidification, which will dramatically change how the oceans support life. It's possible that most forms of seafood we know today will become extinct. http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidificati...