By Dan Shapley
Travelers on some trans-Atlantic forays can feel better about the hundreds of pounds of carbon emitted per passenger as passenger jets streak across the sky. Two European airlines that connect to some U.S. cities now offer passengers the option of purchasing carbon offsets when they purchase tickets. While accounting for an overall small percentage of carbon emissions, airline traffic can have a disproportionately large impact because the pollution occurs so high in the atmosphere. Add contrails, those streaming clouds left in the wake of jets, and a forecast for increased air traffic in the coming years, and you have three big ingredients in the recipe for climate change. Anyone who has used a carbon calculator has seen how much air travel adds to one's personal impact on the climate. Carbon offsets don't go as far as restraint when it comes to emissions, but they ease the conscience and at least mitigate the impact with some carbon-hungry trees or wind-tilting turbines.