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.

Keywords

• black carbon aerosols
• global-scale aerosol model
• large-scale atmospheric transport
• radiative forcing
• snow-albedo forcing