Driving a car helps hike global temperatures in the long run more than making the same long-distance journey by air, the American Chemical Society says.
However, in the short run, travelling by air is worse, because planes strongly affect short-lived warming processes at high altitudes. The answer seems to be to take the bus or train, as this causes a quarter the impact of automobile travel for every mile a passenger travels.
Jens Borken-Kleefeld and his ACS colleagues used a suite of climate chemistry models to consider the climate effects of all long- and short-lived gases, aerosols and cloud effects resulting from transport worldwide.
They concluded that in the long run the global temperature increase from a car trip will be on average higher than from a plane journey of the same distance. However, for the first few years after the journey, air travel increases global temperatures four times more than car travel.
"As planes fly at high altitudes, their impact on ozone and clouds is disproportionately high, though short lived. Although the exact magnitude is uncertain, the net effect is a strong, short-term, temperature increase," says Borken-Kleefeld.
"Car travel emits more carbon dioxide than air travel per passenger mile. As carbon dioxide remains in the atmosphere longer than the other gases, cars have a more harmful impact on climate change in the long term."