Climate change could lengthen the flight times of some air travel, which in turn could have a "feedback" effect resulting in even more atmospheric pollution, a study suggests.
As changing wind patterns in the jet stream cause some long-haul air flights to take longer, the longer time in the air would mean jet airliners are pumping ever more greenhouse gases into the atmosphere from their engine exhaust, the researchers say.
Scientists at the Woods Hole Oceanographic Institution and University of Wisconsin Madison analyzed flight data for four major airlines on routes between Honolulu and Los Angeles, San Francisco and Seattle-Tacoma.
A database maintained by the Department of Transportation allowed them to analyze departure and arrival times by each airline for every single flight on those routes over the past 20 years.
They then used climate models to assess the possible effect on flight times due to increasing variations of the jet stream, the current of high-altitude winds that blow in the Northern Hemisphere from west to east.
Even small increases in round-trip flight times as a result of changes in wind speed and direction could see major increases in fuel consumption and thus emission for airlines, they say in their study being published in Nature Climate Change.
The airline industry already is responsible for 3.5 percent of all greenhouse gas emission, according to the International Panel on Climate Change.
Any increase in airline travel times could result in a feedback loop between the carbon emissions of airplanes and our changing climate, Woods Hole geologists and geophysicist Kris Karnauskas says.
"Upper-level wind circulation patterns are the major factor in influencing flight times," he explains. "Longer flight times mean increased fuel consumption by airliners. The consequent additional input of CO2 into the atmosphere can feed back and amplify emerging changes in atmospheric circulation."
There are about 30,000 commercial flights daily in the United States, and if total round-trip flying time increased by one minute, commercial airliners would be aloft some 300,000 additional hours per year, the researchers say.
That would result in around a billion additional gallons of jet fuel being burned each year at a cost of $3 billion, which would put another 22 billion pounds of CO2 into the atmosphere.
"We already know that as you add CO2 to the atmosphere and the global mean temperature rises, the wind circulation changes as well - and in less obvious ways," says Karnauskas.