A report released by McAfee, an antivirus software company, and prepared by the firm ICF estimates over 62 trillion spam emails are sent annually around the world, consuming about 33 billion kWh of electricity. The report estimates this as 17 million metric tons of carbon dioxide emissions annually. “When you look at it from an individual user perspective you’re only talking about 0.3 grams of carbon dioxide per spam message,” said Dave Marcus, director of security research and communications at McAfee’s Avert Labs when interviewed with PC World. “When you extrapolate the math out to the larger numbers, it definitely is significant.” 17 million metric tons would be equivalent to the greenhouse gas emissions of over 3.1 million passenger vehicles annually or over 1.9 billion (yes, billion) gallons of gas consumed. Moreover, 17 mil. would be more than the annual carbon footprint of the populations living in some major U.S. cities, based on 24 metric tons of emissions per person. The study can be found here.