Sulfur dioxide is a bad thing, right? Indeed, it's been linked to acid rain, crop failures, and respiratory problems—but scrubbing it from the atmosphere has also apparently caused Arctic sea ice to melt, the Anchorage Daily News reports. According to a new study from Environment Canada, recent reductions in sulfur-dioxide and other aerosols have enabled more solar heat to reach the ice. Study authors say that should cause roughly 400,000 square miles of sea-ice melt, which is about 25% to 40% of the seasonal total, depending on the extent of future greenhouse gas emissions. But that shouldn't stop us from keeping our air clean, says study author Nathan Gillett: "We want to avoid that interpretation," he says.
"We’re really just pointing out that it’s part of the picture and should be considered," adds Gillett. "We’re not trying to weigh costs and benefits of sulfur dioxide here." Human-caused sulfur dioxide emissions—which come from burning fossil fuels like coal—have fallen dramatically in the US and the European Union. Even China has been cutting back on emissions with clean-air plans, technological changes to power plants, and a new cap-and-trade program. But humans aren't entirely to blame: Volcanic eruptions are among the natural sources of sulfur dioxide and have at times been blamed for mass extinctions in Earth's past. A new study, however, finds that while volcanoes may have been involved in such catastrophes, "sulfur gases were not the main agent," a study co-author tells Berkeley News.