Effects of different emission inventories on tropospheric ozone and methane lifetime

This study assesses the influence of anthropogenic emission inventories of ozone (O3) precursor species (i.e. NOx, CO, and non-methane hydrocarbons (NMHCs)) prescribed in the simulations of the two phases of the Chemistry-Climate Model Initiative (CCMI) on tropospheric O3, hydroxyl radical (OH), and the methane (CH4) lifetime. We performed two transient simulations for the period 2000-2010 with the chemistry-climate model EMAC, one prescribing the emission inventory of CCMI-1 and the other that of CCMI-2022. Using the tagging approach, we attribute the differences of O3, OH, and the tropospheric CH4 lifetime to individual emission sectors. It is, to our knowledge, the first application of the tagging approach to attribute changes of the simulated CH4 lifetime to individual emission sectors. The emission inventory used for CCMI-2022 leads to a 3.7 % larger tropospheric O3 column and to a 3.2 % shorter tropospheric CH4 lifetime compared to CCMI-1 in the Northern Hemisphere. In the Southern Hemisphere, the tropospheric O3 column is 4.5 % larger, and the tropospheric CH4 lifetime 4.3 % shorter. Differences in tropospheric O3 are largely driven by changes of emissions from the anthropogenic non-traffic and land transport sectors in the Northern Hemisphere. In the Southern Hemisphere, the primary contributors are emissions from anthropogenic non-traffic, biomass burning, and shipping. These sectors also play a significant role in reducing the simulated tropospheric CH4 lifetime. However, the contribution of a particular sector to changes in O3 does not necessarily align with its impact on the CH4 lifetime.