Acceleration of the global methane growth rate over two decades: comparison with shared socioeconomic pathways and implications for future modeling

The Shared Socioeconomic Pathways (SSPs) are a set of harmonized greenhouse gas emission and concentration trajectories, representative of scenarios from the literature. The SSPs show a particularly large range of methane (CH 4 ) trajectories early in the first half of the century, with vastly different implications for near-future climate warming. Using global concentration estimates from NOAA’s Global Monitoring Laboratory and observation-constrained global atmospheric methane estimates from NASA’s Goddard Earth Observing System (GEOS) model, we show that atmospheric methane has been accelerating from 2001 through 2025 with oscillating variability, and that both the trend and variability are driven by microbial emissions. Based on the current trend, we expect average CH 4 concentrations to align most closely with those of the SSPs associated with severe warming by midcentury. Continued atmospheric monitoring and further investigation of the microbial processes that may be causing this increase, including both agriculture and wetland climate feedbacks, are necessary to produce realistic predictions and mitigation scenarios.