An interesting statistic I’ve found: according to Digiconomist’s Bitcoin energy consumption page, the average carbon footprint of each transaction made is 162.48kg of CO2.

Based on Carbon Independent’s aviation emissions estimates of 26.6g of CO2 per passenger km, we can come up with a rough estimate of each bitcoin transaction being the equivalent of a 6,108km (3,795mi) flight. This is more or less the distance of a flight from New York City to Copenhagen, Denmark (calculated using DistanceFromTo).