Xueying Yu

1 Introduction Methane (CH4) is an important climate forcer on decadal timescales, with a 9-year lifetime and a 20-year global warming potential more than 80 times greater than that of carbon dioxide (IPCC, 2021). This importance motivated the Global Methane Pledge at the 2021 United Nations Climate Change Conference (COP26), whereby >150 countries have committed to collective actions targeting a >30% global methane emission reduction by 2030 (GMP, 2021).

1 Introduction Anion exchange membrane water electrolysis (AEMWE) has emerged as a promising technology for sustainable hydrogen production by integrating moderate operational costs, high energy efficiency, and compatibility with non-precious metal catalysts in alkaline media [1, 2]. However, the kinetics of the alkaline hydrogen evolution reaction (HER) are intrinsically sluggish due to the involvement of the water dissociation step (Volmer step: H2O + e− → H* + OH−) [3, 4].

Abstract Annual increases in atmospheric methane have reached record highs over the past five years, yet the underlying processes and regional sources remain uncertain. Here we quantify the average 2019-2021 global methane budget using Bayesian 4D-Var inversions that assimilate satellite methane retrievals and in-situ δ13C-CH4 and δD-CH4 measurements. The methane-isotopic inversion yields total emissions of 623 [585–643] Tg/y, slightly higher than the methane-only inversion.