As ash continues to belch into the atmosphere from Iceland's now world-famous Eyjafjallajokull volcano, stranding thousands of travelers around the globe, two main questions are: How long will the eruption last, and could it eventually affect the world's climate?
Unfortunately, scientists appear uniform in their uncertainty.
"We don't know how long this eruption will go on," says Stefan Wastegard, a geologist who studies ancient ash falls from Icelandic volcanoes at Stockholm University in Sweden. "That's the problem with volcanic eruptions, you really don't know how they're going to go."
One Smithsonian Institution volcano expert, Sally Sennert, says that the eruption could last for months, just as Eyjafjallajokull's previous one did back in 1821-23. But even she said, "there's no telling how long the eruptions could last."
Depending on the weather, the ash that's already in the atmosphere could hang around for weeks -- though its location will depend on the wind, says Einar Kjartansson of the Icelandic Meteorological Office.
(Click here for a map of the current ash zone over Europe).
As for its effect on global weather, "we'll see what happens, it all depends on the volcano," says climate scientist Caspar Ammann of the National Center for Atmospheric Research in Boulder, Colo. "Right now, the magnitude and explosiveness of the Icelandic eruption is not enough to have significant climate effects."
Eyjafjallajokull's current eruption of ash doesn't contain much sulfur, which is needed to generate tiny sulfuric acid droplets that could linger in the upper atmosphere and have a cooling effect, Ammann says. Further, its explosive bursts lack the pop to carry much ash above 30,000 feet, where it would need to reside lodged in the atmosphere for the next few years. "Unless the eruption changes, the climate effects don't look significant," he says.
"It's not a very big eruption. Iceland just sits almost right under the jet stream so the ash is being carried into the heart of Europe," Amman says.
If, however, Eyjafjallajokull's more potent volcanic neighbor Katla gets into the eruption act, all bets are off.
In 1991, the eruption of Mount Pinatubo in the Philippines, the second-largest eruption of the 20th century (much larger than Eyjafjallajokull), sent a sulfuric acid haze into the stratosphere, reducing global average temperatures about 0.9 degrees Fahrenheit over the next year.
Contributing: Associated Press
By Dan Vergano, Elizabeth Weise, and Doyle Rice
Visit Science Fair for your daily dose of scientific news, from dinosaurs to distant galaxies. Science Fair is written by science reporters Dan Vergano and Elizabeth Weise and weather reporter Doyle Rice. Their subjects are often controversial -- and always fascinating -- be they stem-cell research, slime mold, or underground slush on Mars. More about the team