Reduction in Global Warming due to Fuel Economy Improvements and Emissions Control of Criteria Pollutants: New US. Light-Duty Vehicles (19684991)

Abstract

This paper explores the impact of US emission controls and fuel economy improvements on the global warming potential (GWP) of new light-duty vehicles. Fuel economy improvements have reduced the GWP of both passenger cars and light-duty trucks by lowering the per mile emissions of carbon dioxide (CO{sub 2}). Further GWP reductions have been achieved by emission standards for criteria pollutants: carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO{sub x}). The GWP of a criteria pollutant was calculated by multiplying the emission rate by a relative global warming factor to obtain a CO{sub 2} equivalent emission rate. Both CO{sub 2} and criteria pollutant emission rates per vehicle have decreased substantially for new light-duty vehicles over the period from 1968 to 1991. Over that period, the GWP from CO{sub 2} was reduced by almost 50% in new vehicles by improving fuel economy. In that same time period, the GWP from criteria pollutants from new vehicles was reduced with emission controls by from 80% to 90% depending on the global warming time frame of interest. Consequently, total reductions in the GWP of new passenger cars and light-duty trucks have been on the order of 55 to 75 percent compared to precontrol (before more » 1968) new vehicles. However, the reduction in GWP caused by emission control of criteria pollutants has been larger than the reduction caused by improved fuel economy (i.e., reduced CO{sub 2}). The contribution of criteria pollutants to the GWP of precontrol new vehicles was substantial, but their contribution has been reduced significantly due to US emission controls. As a result, the contribution of criteria pollutants to global warming is now much less than the contribution of CO{sub 2} from fuel consumption. « less