A modelling study of the impact of on-road diesel emissions on arctic black carbon and solar radiation transfer

Abstract

Market strategies have greatly incentivized the use of diesel engines for land transportation. These engines are responsible for a large fraction of black carbon (BC) emissions in the extra-tropical Northern Hemisphere, with significant effects on both air quality and global climate. In addition to direct radiative forcing, planetary-scale transport of BC to the Arctic region may significantly impact the surface albedo of this region through wet and dry deposition on ice and snow. A sensitivity study is made with the University of L'Aquila climate-chemistry-aerosol model by eliminating on-road diesel emissions of BC (which represent approximately 50% of BC emissions from land transportation). According to the model and using emission scenarios for the year 2000, this would imply an average change in tropopause direct radiative forcing (RF) of -0.054 W·m-2 (globally) and -0.074 W·m-2 over the Arctic region, with a peak of -0.22 W·m-2 during Arctic springtime months. These RF values increase to -0.064, -0.16 and -0.50 W·m-2, respectively, when also taking into account the BC snow-albedo forcing. The calculated BC optical thickness decrease (at λ = 0.55 μm) is 0.48 × 10-3 (globally) and 0.74 × 10-3 over the Arctic (i.e., 10.5% and 16.5%, respectively), with a peak of 1.3 × 10-3 during the Arctic springtime.