Comment on acp-2022-776

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> The TM5-FASST tool was used to study the influence of abatement policies within and outside the UNECE region on the exposure to O₃ and PM_2.5 and associated mortality in the UNECE countries. To that end, the impacts of pollutants deriving from different geographical areas and activity sectors were evaluated using ECLIPSE V6 air pollutant and greenhouse gases emission reduction scenarios. The mortalities were attributed to O₃ and PM_2.5 following the Global Burden of Disease approach and allocated to geographic areas (UNECE and non-UNECE) and activity sectors, including natural sources. In addition, a combination of runs designed for the purpose led to allocating exposure to O₃ and related mortality to two families of precursors: NO_X-VOC and CH₄. In this study the baseline scenario (CLE), that assumes that all air quality and greenhouse gas abatement measures adopted by 2018 are fully implemented, is compared with more ambitious scenarios (maximum feasible reduction, (MFR)). The conclusion from this comparison is that O₃ exposure within the UNECE area is more sensitive to measures outside the UNECE region, than PM_2.5 exposure even though the latter leads to higher mortality than the former. In the current legislation scenario (CLE), the mortality associated with O₃ exposure in the UNECE region grows steadily from 2020 to 2050. The upward trend is mainly associated with the growing impact of CH₄ emissions from areas outside UNECE. Also, the mortality related to NO_X-VOC emissions outside UNECE increases in the same period. By comparison, a measurable decrease is observed in the mortality attributable to NO_x-VOC emissions from UNECE. In the same time window, the mortality associated with PM_2.5 exposure in the UNECE region at first decreases between 2020 and 2040 and then rises until 2050. The PM_2.5 related mortality in UNECE is mainly due to anthropogenic emissions within this region followed by natural sources (sea salt and dust) mainly located outside the UNECE region. Between 2020 and 2050, the impact of some UNECE anthropogenic sources on PM_2.5-related mortality decreases progressively, in particular road transport, energy production and domestic combustion while others, namely agriculture and industry, show an upward trend. Finally, the analysis of MFR scenarios confirms that abatement measures in line with UN SDGs and the Paris Agreement can lead to significant co-benefits between air quality and climate policies.