Driving a car can be as bad as doing the same long-distance journey by air if you're worried about raising global temperatures, a new study has declared.
However, in the short run traveling by air has a larger adverse climate impact because airplanes strongly affect short-lived warming processes at high altitudes.
In the study, Jens Borken-Kleefeld and colleagues compared the impacts on global warming of different means of transport. The researchers uses, for the first time, a suite of climate chemistry models to consider the climate effects of all long and short-lived gases, aerosols and cloud effects, not just carbon dioxide, resulting from transport worldwide.
However, in the first years after the journey, air travel increases global temperatures four times more than car travel. Passenger trains and buses cause four to five times less impact than automobile travel for every mile a passenger travels.
The findings prove robust despite the scientific uncertainties in understanding the earth's climate system.
"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," explains Dr. Jens Borken-Kleefeld, lead author of the study.
"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."
The study appears in ACS' Environmental Science and Technology, a semi-weekly journal.