Abstract
Road traffic emits not only carbon dioxide (CO2), but also other pollutants such as nitrogen oxides (NOx), volatile organic compounds (VOC) and carbon monoxide (CO). These chemical species influence the atmospheric chemistry and produce ozone (O3) in the troposphere. Ozone acts as a greenhouse gas and thus contributes to anthropogenic global warming. Technological trends and political decisions can help to reduce the O3 effect of road traffic emissions on climate. In order to assess the O3 response of such mitigation options on climate, we developed a chemistry-climate response model called TransClim (Modelling the effect of surface Transportation on Climate). It considers road traffic emissions of NOx, VOC and CO and determines the O3 change and its corresponding stratospheric-adjusted radiative forcing. Using a tagging method, TransClim is further able to quantify the contribution of road traffic emissions to the O3 concentration. The response model bases on lookup-tables which are generated by a set of emission variation simulations performed with the global chemistry climate model EMAC (ECHAM5 v5.3.02, MESSy v2.53.0). Evaluating TransClim against independent EMAC simulations reveals very low deviations of all considered species (0.01–7 %). Hence, TransClim is able to reproduce the results of an EMAC simulation very well. Moreover, TransClim is about 6000 times faster in computing the climate effect of an emission scenario than the complex chemistry-climate model. This makes TransClim a suitable tool to efficiently assess the climate effect of a broad range of mitigation options for road traffic or to analyse uncertainty ranges by employing Monte-Carlo simulations.
Highlights
Ozone acts as a greenhouse gas and contributes to anthropogenic global warming
90 The aim of TransClim is to assess the effect of road traffic emissions of nitrogen oxides (NOx), volatile organic compounds (VOC) and carbon monoxide (CO) on tropospheric O3 and its respective effect on climate
Each output variable has its own LUT. 120 To obtain the desired variable xnew for a given road traffic emission scenario, the corresponding emission scaling factors for each emission region i are used as input and the change ∆x(i) for each emission region is calculated by linearly interpolating within the respective LUT
Summary
Mobility is getting more and more important in today’s society. As residences, workplaces, schools and recreation areas are often spatially separated, there is an increasing demand on our transportation system. The perturbation method does not take non-linear relations, such as the tropospheric O3 chemistry, into account (Grewe et al, 2010) It quantifies only the impact of road traffic emissions on O3. Grewe et al (2010) propose to apply the so-called tagging method It follows the most important reaction pathways for the formation and destruction of O3 and determines the contribution of road traffic emissions to the O3 concentration. 60 Typically, complex chemistry-climate models are applied to assess the climate effect of traffic emissions These simulations are computational expensive and require a substantial amount of time. We developed a new tool called TransClim (Modelling the effect of surface Transportation on Climate) It is a chemistry-climate response model which efficiently determines the O3 effect of a broad range of road traffic emission scenarios on climate. Significant parts of the text already appeared in Rieger (2018)
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