Scientists Calculate the Contribution of Air Travel to Climate Change

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Climate sci­en­tists quan­ti­fied the impact of avi­a­tion on cli­mate change, find­ing that pas­sen­ger and com­mer­cial flights around the globe account for approx­i­mately 4 per­cent of the anthro­pogenic over­heat­ing of the planet to date.

Air travel is also respon­si­ble for 2.4 per­cent (around 1 bil­lion tons) of the annual human-gen­er­ated CO2 emis­sions and is expected to increase global tem­per­a­ture by 0.1 ºC by 2050, the sci­en­tists said, pro­vided that global avi­a­tion will con­tinue to grow at pre-pan­demic rates.

“These num­bers don’t seem high, but again, remem­ber that is more than most coun­tries emit,” Milan Klöwer, a post­doc­toral researcher at the University of Oxford and one of the study authors, told Mongabay con­ser­va­tion news ser­vice.

To assess the avi­a­tion indus­try’s impact on cli­mate change, the researchers used flight his­tory data obtained from inter­na­tional avi­a­tion orga­ni­za­tions and data­bases, in com­bi­na­tion with the annual fuel con­sump­tion and dis­tance cov­ered by global air travel derived from var­i­ous stud­ies and sci­en­tific papers.

Their study, pub­lished in Environmental Research Letters, is among the few attempt­ing to cal­cu­late how much human-caused global warm­ing may be attrib­uted to air travel.

“Most peo­ple think of warm­ing in terms of degrees, not tons of car­bon emit­ted, so we wanted to cal­cu­late that,” Klöwer said.

The researchers acknowl­edged that fly­ing can be the only avail­able means of travel, albeit with a heavy car­bon foot­print.

“Flying often pro­vides the only pos­si­bil­ity to reach remote loca­tions within an accept­able time frame,” they noted. ​“However, fly­ing is also one of the most car­bon-inten­sive ways to travel, emit­ting up to 100 times more per hour than train, bus or shared car rides.”

Apart from CO2 emis­sions, the researchers explained that another rea­son for avi­a­tion’s high con­tri­bu­tion to Earth’s over­heat­ing is the mix of cli­mate pol­lu­tants jet fuels gen­er­ates when burn­ing.

“Nitrogen oxides [gasses emit­ted from air­craft exhaust] react in the atmos­phere alter­ing the radia­tive bal­ance of other gasses, includ­ing methane, ozone and stratos­pheric water vapor and there­fore indi­rectly impact the cli­mate,” they wrote. ​“These non-CO2 emis­sions cause an addi­tional net warm­ing effect.”

Aircraft also con­tribute to cli­mate change through con­den­sa­tion trails (con­trails), a sig­nif­i­cant fac­tor in aviation’s impact on the planet’s cli­mate.

These evanes­cent line-shaped clouds of ice form when soot from the engine exhaust mixes with the cold air are high alti­tudes, increas­ing the sky’s cloudi­ness and trap­ping the heat radi­at­ing from Earth at night.

The study sug­gested that a decrease in flights by 2.5 per­cent per year or a tran­si­tion to a 90 per­cent car­bon-neu­tral fuel mix by 2050 would effec­tively curb the avi­a­tion-related warm­ing of the planet.

“I’ll just stick to the ones [flights] that are really impor­tant, and replace the other ones with vir­tual meet­ings or hol­i­days closer to home,” said Klöwer, urg­ing fre­quent air trav­el­ers to recon­sider board­ing a plane if not nec­es­sary.

Klöwer finally acknowl­edged that the power to decar­bonize air travel lies chiefly with the indus­try and gov­ern­ments. However, indi­vid­u­als can pro­mote change if they mind their car­bon foot­print and engage in the dis­cus­sion.

“If every­one talks about it, that can cre­ate polit­i­cal change,” he said.

• Mongabay
• Environmental Research Letters