Wildfires dominate inter-annual variability in atmospheric methane growth

Atmospheric methane, a key greenhouse gas, has continued to grow in recent years, jeopardizing the Paris Agreement's climate goals. Atmospheric methane growth rate (MGR) shows pronounced inter-annual variability (IAV), which provides a "natural laboratory" to unravel climatic controls on methane dynamics, thereby improving future projections critical to climate mitigation. While multiple processes are known to influence methane sources and sinks, the drivers remain actively debate and their interplay is unquantified systematically. Here, we integrate state-of-the-art emission inventories, observation constraints, and model simulations to resolve and evaluate systematacially these contributions. Challenging the prevailing wetland-centric consensus, we demonstrate that wildfires dominate the IAV in MGR through near-equivalent dual mechanisms: direct methane emissions and indirect atmospheric sink, followed with wetland emissions and lightning-induced sink effects. These drivers are orchestrated by the El Niño-Southern Oscillation (ENSO) through distinct phase-specific contrasts: during El Niño, disproportionately escalating wildfire impacts are partially offset by suppressed wetland emissions and enhanced lightning sink, whereas La Niña amplifies wetland emissions and inhibits lightning-induced sink. This framework largely explains observed MGR variability. Our study implies that under future warming, the nonlinear intensification of fire-climate feedbacks may accelerate atmospheric methane growth, posing a greater threat than previously anticipated.