Proposal: Spraying sulfur particles into the atmosphere, either by large balloons or aircraft, would reduce the Earth's absorption of sunlight. The sulfur dioxide has the ability to essentially block sunlight, thus cooling down the planet. This phenomenon is seen naturally after a large volcanic eruption.

Risk: Results would be completely unpredictable and hard to control. Rainfall and weather patterns could be affected drastically. One study even suggests it would alter the color of our skylines.