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Historical data on volcanic activity gathered from ice cores in Greenland show that sulfur dioxide emissions play a more important role in global climate change than carbon dioxide, a Jackson Hole geologist says.

Peter Ward, a member of Geologists of Jackson Hole and a former researcher with the U.S. Geological Survey, is presenting a research paper in Chicago today as the city hosts the annual American Association for the Advancement of Science conference. The paper appears in the journal Thin Solid Films.

Ward says volcanos have historically dumped large amounts of sulfur dioxide into the atmosphere, resulting in global temperature changes. Ward looked at Web-based data on the concentrations of atmospheric sulfur and other pollutants in the layers of Greenland ice cores and correlated those with historic volcanic eruptions and estimated global temperatures.

Scientists already know that sulfur at lower concentrations, such as those that result from a single large volcanic eruption, reflects heat from the sun. If eruptions occur every few years, it can push the Earth incrementally into an ice age.

A recent example of this effect was the eruption of Mount Pinatubo, a volcano in the Philippines that erupted in 1991, dumping 20 million tons of sulfur dioxide into the atmosphere. Researchers say the resulting sulfuric acid haze reduced global temperatures by 0.9 degrees. The event also caused substantial ozone depletion.

However, data from the ice cores show that more frequent eruptions result in global warming, Ward says. If large eruptions occur more than once a year for several decades, he says, the highly reactive sulfur dioxide gas reduces the atmosphere’s capacity to oxidize greenhouse gases and, therefore, prevents them from precipitating out of the atmosphere. Instead, the sulfur dioxide binds with oxidizing molecules in the atmosphere, resulting in acid rain and leaving greenhouse gases in the air.

By 1962, human fossil-fuel emissions added sulfur dioxide to the atmosphere at a rate equivalent to one large volcanic eruption every 1.7 years, fast enough to result in a rapid heating of the atmosphere, Ward says. While recent efforts to reduce acid rain have resulted in less sulfur dioxide in the atmosphere, Ward says climatologists and politicians need to pay more attention to the pollutant.

“We’re about to make huge decisions in Congress [based on the notion that carbon dioxide drives global climate change],” he said. “Sulfur dioxide is more important than carbon dioxide, but we can’t rule out carbon dioxide.”

Ward admits that his theory goes against popular ideas about climate change, and he says he’s already met resistance from a number of renowned climatologists. His paper was also rejected by a number of climatology journals, as well as Science and Nature. Ward acknowledges that his paper lacks statistical analysis and doesn’t include ice cores from other locations such as the Antarctic.

Still, he says the Greenland ice core data speak for themselves.

“I’m coming out of left field,” he said. “I’m an earth scientist, and I discovered something in earth science with huge implications.”

“[Scientists] over time develop rules of thumb,” Ward said. “That’s where we are right now. My explanation may not be totally correct. I expect significant issues to be raised.”

Dr. Stephen Schneider, a climatologist and professor of biology at Stanford University and a senior fellow at the Woods Institute for the Environment, expressed skepticism about certain aspects of the paper, including the lack of statistical analysis, but said the research could still prove important.

“New, iconoclastic ideas take time to generate enthusiasm in the scientific community,” he said. “Everybody has to be welcomed. Science is all about new thinking. [Ward’s research] does seem to raise some interesting ideas.”

Schneider raised issues with Ward’s premise that current climatic conditions mimic history.

“Just because you find associations in ancient climate history that operate over millions of years doesn’t mean that those processes would work the same way in the short term.”

Schneider also said the current theory that carbon dioxide drives global climate change is hard to refute.

“The models have been very extensively tested on the observed data over the time period of the past century,” he said. 

“I appreciate people who look carefully at the record and try to come up with new ideas,” Schneider said. “Most iconoclastic ideas drive the field forward but don’t necessarily survive intact. I think it will generate healthy debate as long as some special interests don’t misinterpret [the research] as refuting the well-established connection between greenhouse gas increases and global warming over the last decades.”