You don't need to have spent four nights in a European airport to know just how disruptive last week's eruption of the Icelandic volcano Eyjafjallajökull has been. Despite the global headache, there's a hint of good news. Climatologists who shudder whenever anything is expelled into the atmosphere can rest easy knowing that the atmospheric effects of Eyjafjallajökull won't linger, nor will the belching volcano have a sizable impact on global climate.
Initially, the environmental consequences will be severe. The contents of eruptions depend on location and geologic conditions, but all volcanoes spew skyward a mix of pulverized rock and glass, both of which can devastate ecosystems in the short term. The floating ash that has limited air travel will soon settle on Europe's fields and water systems and may have deadly consequences when ingested by livestock. The glass-and-rock mixture is fatal to most plant species since it prevents photosynthesis; as a result, greenery in Iceland and parts of northern Europe will have to fight to survive. But the effects don't last long. Within several months, the ash will simply blow away into the atmospheric background or fossilize to form new rock.
Then there's the gases. As the world scrambles to assess its output of greenhouse gases that contribute to climate change, could an unplanned eruption that lets loose carbon dioxide and other heat-trapping compounds derail the effort? The answer, in short, is no. "Volcanoes don't emit that much carbon," says Cindy Werner, an analyst with the U.S. Geological Survey. "And there won't be global effects of this particular eruption." Compared to other volcanic events, Eyjafjallajökull is small potatoes and lingered in the news cycle only because of its location and effect on global economies. Each year in Alaska, as many as four eruptions of the same size or bigger occur. But with little human impact, attention to those blasts—if there is any—fades quickly.
That's because the planet is mostly equipped to deal with the gases that come out of volcanoes and has been for millions of years. It's the addition of skyrocketing emissions from human industrialization that normally concern climate scientists. On-the-ground estimates are still hazy in Iceland, but satellite images indicate that Eyjafjallajökull has emitted about 10,000 tons of carbon dioxide per day over the past week, a number roughly equal to the emissions of 2,000 cars per year. That's not insignificant, but compared to a bigger eruption, like Mt. Pinatubo in the Philippines in 1991, which spewed out 42 million tons over several months, Eyjafjallajökull is like a Tonka truck in a world of big rigs.
The bigger concern for climate researchers is sulfur dioxide, one of the prominent byproducts of volcanic eruptions. Because of its molecular structure, significant quantities of the compound can lead not to global warming but to global cooling. USGS researchers last year who analyzed the effects of three different Indonesian volcanoes over the past 200 years found that long after the ash and other particulate matter settle, which usually happens within days or weeks, increased levels of SO2 aerosols that migrate into the upper stratosphere actually deflect sunlight and heat rather than locking them in. Long term, serious global cooling could be even worse than warming, decimating the availability and quality of seeds worldwide and influencing mass extinctions. Eyjafjallajökull's aerosols will likely be rained out in the troposphere before they make it that high, but even output from the strongest eruptions settles within a few years, limiting lasting environmental impact.
Still, even without the threat of permanent harm, some environmentalists think Iceland could hold clues of similar and more frequent events to come. But in at least one way, Eyjafjallajökull may have been more helpful than harmful in the fight against climate change. "There was more reduction in CO2 from airplanes not flying all week than in the amount that came from the volcano," says Alan Robock, an environmental scientist and volcanologist at Rutgers University. As it turns out, it wasn't a bad week for the environment after all.