Way back in 2006, the Guardian's green scold George Monbiot headlined an article, "We Are All Killers: Until we stop flying." More recently, the New York Times in 2013 declared that air travel might "your biggest carbon sin." In Monbiot's terms, flying is a mortal, not a venial sin against Gaia. Perhaps not.
In a new analysis reported in R&D Magazine, University of Michigan transportation research Michael Sivak found that it takes twice as much energy to drive than to fly. From R&D Magazine:
He examined recent trends in energy intensity — the amount of energy needed to transport a person a given distance — in light-duty vehicles (cars, SUVs, pickups and vans) versus domestic airline flights. His analysis measured BTU per person mile from 1970 to 2012.
Sivak found that the energy intensity of driving is 2.07 times that of flying. In 2012, BTU per person mile was 4,211 for driving compared to 2,033 for flying. Consequently, the entire fleet of light-duty vehicles would have to improve from the current on-road fuel economy of 21.6 mpg to 44.7 mpg for driving to be as energy intensive as flying.
So if some frequent flyers were ever worried about their carbon sinning, they can now think of it as more of a venial rather than a mortal one. Of course, those especially worried about their carbon sins can always buy carbon indulgences.