Impact of Future Methane Emission Trajectories on Atmospheric Composition and Climate in a Future Hydrogen Economy

Abstract Hydrogen () is projected to have an increasingly important role in a future low‐carbon economy. In a future economy, emissions could increase across the supply chain. When , a radiatively inert gas, is emitted, it undergoes similar chemical reactions to methane (C) in the atmosphere, leading to detrimental climate as well as air quality effects. Here, we study the interactions between hypothetical future increases in emissions and possible future C emission trajectories, utilizing the GFDL AM4.1 atmospheric chemistry‐climate model (CCM) driven by and C emissions to more fully simulate their chemical feedbacks. Due to their chemical coupling, the effects of on atmospheric composition are dependent on background C emission levels. However, despite this dependency, the climate impact of remains largely independent of background C emission levels, because of offsetting changes in the forcing from radiatively active gases as well as model rapid adjustments. Next, we find that an ambitious 45% anthropogenic C emission reduction not only delivers greater surface cooling than the surface warming caused from a hypothetical high‐end 480% emission increase, but also effectively counteracts the atmospheric composition impacts from the increase in emissions as well. Increased adoption in an economy, replacing fossil fuels, could contribute to reductions in other short‐lived climate forcer emissions, such as ozone precursors and aerosols. When these additional reductions are considered, C mitigation is increasingly important so as to maximize the climate and air quality benefits of an economy.