Short-lived greenhouse gases (GHG), including methane (CH4) and ozone (O3), are important contributors to global warming. Unlike long-lived GHGs, their tropospheric abundance is strongly influenced by reactive processes and depends on complex photochemical formation and removal pathways and the availability of precursors and reactants. Additionally, CH4 and O3 are photochemically coupled in the troposphere: the hydroxyl (OH) radical, whose production is largely driven by sunlight, is the dominant atmospheric sink of CH4, while CH4 oxidation contributes to O3 formation and impacts atmospheric oxidation capacity.

This session focuses on the photochemical sources, sinks and mechanisms governing short-lived GHGs in the troposphere, with a particular emphasis on CH4 and O3, their precursors and key reactants. Relevant topics include, but are not limited to: the chemistry of CH4 and O3 and their interactions with nitrogen oxides (NOx), volatile organic compounds (VOC), hydroxyl (OH) and peroxy (HO2, RO2) radicals, carbon monoxide (CO), and halogen species (Cl, Br, I).

The goal of this session is to discuss how photochemical pathways affect the abundance and spatio-temporal distribution of short-lived GHGs, associated uncertainties and challenges, and their future climate implications. We welcome contributions from observational, laboratory, and modeling studies across the entire troposphere, including innovative measurement technologies, advances in global modeling and other novel methodological approaches. Submissions may address photochemical mechanisms and reaction pathways, tropospheric oxidation capacity, ozone formation sensitivity, methane lifetime, regional and global long-term trends, precursor emission changes, and the broader impacts of short-lived GHGs on climate and human health, both now and in the future.