title: Climate forcing from the transport sectors.
abstract: Although the transport sector is responsible for a large and growing share of global emissions affecting climate, its overall contribution has not been quantified. We provide a comprehensive analysis of radiative forcing from the road transport, shipping, aviation, and rail subsectors, using both past- and forward-looking perspectives. We find that, since preindustrial times, transport has contributed approximately 15% and 31% of the total man-made CO2 and O3 forcing, respectively. A forward-looking perspective shows that the current emissions from transport are responsible for approximately 16% of the integrated net forcing over 100 years from all current man-made emissions. The dominating contributor to positive forcing (warming) is CO2, followed by tropospheric O3. By subsector, road transport is the largest contributor to warming. The transport sector also exerts cooling through reduced methane lifetime and atmospheric aerosol effects. Shipping causes net cooling, except on future time scales of several centuries. Much of the forcing from transport comes from emissions not covered by the Kyoto Protocol.
authors.affiliation: Center for International Climate and Environmental Research-Oslo, P.O. Box 1129 Blindern, N-0318 Oslo, Norway. j.s.fuglestvedt@cicero.uio.no
authors.forename: Jan
authors.initials: J
authors.lastname: Fuglestvedt
authors.forename: Terje
authors.initials: T
authors.lastname: Berntsen
authors.forename: Gunnar
authors.initials: G
authors.lastname: Myhre
authors.forename: Kristin
authors.initials: K
authors.lastname: Rypdal
authors.forename: Ragnhild Bieltvedt
authors.initials: RB
authors.lastname: Skeie
mesh_terms: D000336:Aerosols; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000191:economics / Q000331:legislation & jurisprudence* / Q000517:prevention & control*; D001272:Atmosphere; D002245:Carbon Dioxide / Q000032:analysis* / Q000737:chemistry / Q000191:economics; D002980:Climate; D003246:Conservation of Energy Resources / Q000191:economics / Q000331:legislation & jurisprudence* / Q000379:methods*; D017752:Greenhouse Effect; D008962:Models, Theoretical; D010126:Ozone / Q000737:chemistry; D012016:Reference Values; D014186:Transportation; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D001335:Vehicle Emissions; D002245:Carbon Dioxide; D010126:Ozone