Diesel boom, emissions bust

Atmos. Environ. 198, 122–132 (2019)

Transport is a significant contributor to global GHG emissions, and following the Kyoto Protocols in 1997 many European governments encouraged fuel-efficient diesel car sales as an emissions reduction strategy. Whether this was efficacious and led to appreciable climate benefits remains an open question.

Vincenzo Lombardo/Photographer’s Choice RF/Getty

Eckard Helmers of the University of Applies Sciences Trier, Germany, and colleagues report real-world CO₂ emissions from passenger cars in Europe between 1995 and 2015 and evaluate the potential emissions reduction benefits during this period of diesel growth. From 1995 to 2001, diesel cars emitted less CO₂ per kilometre than petrol cars, but the additional black carbon emissions resulted in higher climate-relevant emissions overall. From 2001 to 2015, diesel and petrol cars were indistinguishable with respect to emissions. An evaluation of vehicle lifetime emissions under different scenarios suggests that the historic diesel boom was ineffective at reducing total emissions relative to a scenario in which the ratio of diesel to petrol cars remained constant. Larger emissions reductions would have been realized by promoting alternative CO₂-efficient fuels and reducing the overall size of the passenger vehicle fleet.