Anything else that could shield us from global warming?

Yes, volcanoes. When Mount Pinatubo erupted in June 1991, it threw a huge amount of debris into the stratosphere that partially shielded the surface of the Earth from incoming solar energy. Particularly effective was Pinatubo's emissions of large amounts of sulphate particles that scatter sunlight. 

Computer models successfully predicted that in the short term, the debris would cool the Earth's atmosphere. The models also predicted that as the volcanic debris cleared in 1992 and 1993, average temperatures would swiftly return first to the level of the 1980s, and then, by the middle of the 1990s, to the slightly higher levels that would be expected with the ongoing buildup of greenhouse gases. 

See "Blowing hot and cold" feature.