Cool blast.

When a volcano pops its top, it ejects masses of gases that can alter Earth's weather for years. Now, research shows that a volcano's climate-changing power depends on its location on the planet.

How does a volcanic blast affect the climate? During explosive eruptions, volcanoes spew sulfur dioxide gas sky-high. The gas soars to the stratosphere, or the layer of the atmosphere from 12 to 50 kilometers (7 to 31 miles) above Earth's surface. There, the gas transforms into liquid droplets called aerosols. These droplets reflect light from the sun--bouncing many of the warming rays back into space. "It has a cooling effect on the planet," says Luke Oman, an environmental scientist at Rutgers University in New Jersey.

When a volcano erupts near Earth's equator, its cooling effect can be felt worldwide. That's because air circulation in the stratosphere causes gases from the tropics to circle around Earth and move toward the poles. "The aerosols spread out over the entire globe," says Oman. But when a volcano explodes near Earth's poles, the stratospheric circulation simply swirls around the pole, keeping the gases--and resulting cooling--at high latitudes.

Oman says his research could help scientists predict climate changes after a big eruption: "It will help people prepare better for the effects."