For all the fear of global warming, all it takes is one good volcano to put a temporary chill on the earth. After Mt. Pinatubo's eruption in the Philippines on June 16, 1991, scientists predicted that the planet's temperature would drop. Now, researchers at the National Oceanic & Atmospheric Administration have shown that the predictions were correct. Measurements made by NOAA observatories in Hawaii reveal that the amount of light and heat from the sun reaching the ground has dropped nearly 4%. Satellite readings show that air temperatures over the globe have fallen by 1F--and continue to drop. The cooling may eventually reach 2F.

The culprit in this big chill is 20 megatons of sulfur dioxide spewed skyward by Pinatubo. Some 15 miles above the earth, the gas combined with water to form tiny sulphuric acid droplets. The droplets reflect solar radiation, reducing the amount of heat from the sun, and will remain in the atmosphere for up to three years. Because the planet takes a long time to warm or cool, says NOAA meteorologist Ellsworth Dutton, "the cooling effect could last for five years."

Before it's here, it's on the Bloomberg Terminal. LEARN MORE