March 21, 2013 | Over the past decade, the climate has not warmed as swiftly as global climate models predicted, but it hasn’t been clear what factors might be tamping down the warming. Some experts point to increased industrial emissions of sulfur dioxide from coal burning over China and India. Others have wondered whether sulfur emissions from volcanic activity could also play a role. However, it’s long been thought that only colossal volcanic events such as the 1991 Mt.