Explosive volcanic eruptions might be attention grabbing, but a new review of research finds that their environmental impact pales in comparison to human activities. According to the research, humans put out the same amount of carbon dioxide in three to five days that all of the volcanoes on Earth put out in one year. "Anthropogenic carbon dioxide emissions dwarf global volcanic carbon dioxide emissions," study researcher Terrance Gerlach, of the U.S. Geological Survey, said in a statement. Carbon dioxide, or CO2, is the main greenhouse gas responsible for climate change. Gerlach crunched the carbon dioxide numbers from earlier studies of...