Effects of different emission inventories on tropospheric ozone and methane lifetime

Abstract. This study assesses the influence of anthropogenic emission inventories of ozone (O₃) precursor species (i.e., NO_x, CO and non-methane hydrocarbons (NMHCs)) prescribed in the simulations of the two phases of the Chemistry-Climate Model Initiative (CCMI) on tropospheric O₃, the 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.