The 1991 eruption of the Mt. Pinatubo volcano caused a 1 degree Fahrenheit global cooling effect. The sulfur particles that were discharged from the volcano reflected sunlight away from the Earth's surface. Scientists inspired by the natural cooling effect of sulfur have proposed that an artificial sulfur haze could protect us from solar radiation in dire circumstances.
Scientists used computer models to test 11 different scenarios. They said the sulfur shield seems like it would work to protect the Earth in her last days, in an extreme case of global warming. But with a strong aversion to geo-engineering and a $400 million a year operating cost, the shield will likely remain a theory.