Environmental impact of aviation
Like other emissions resulting from fossil fuel combustion, aircraft engines produce gases, noise, and particulates, raising environmental concerns over their global impact and their local air quality effect.
Jet airliners contribute to climate change by emitting carbon dioxide (CO
2), the best understood greenhouse gas, and, with less scientific understanding, nitrogen oxides, contrails and particulates. Their radiative forcing is estimated at 1.3–1.4 that of CO
2 alone, excluding induced cirrus cloud with a very low level of scientific understanding. In 2018, global commercial operations generated 2.4% of all CO
Jet airliners have become 70% more fuel efficient between 1967 and 2007, and CO
2 emissions per Revenue Ton-kilometer (RTK) in 2018 were 47% of those in 1990. In 2018, CO
2 emissions averaged 88 grams of CO
2 per revenue passenger per km. While the aviation industry is more fuel efficient, overall emissions have risen as the volume of air travel has increased. By 2020, aviation emissions were 70% higher than in 2005 and they could grow by 300% by 2050.