Boreal-Arctic wetland methane emissions modulated by warming and vegetation activity

Wetland methane (CH₄) emissions over the Boreal-Arctic region are vulnerable to climate change and linked to climate feedbacks, yet understanding of their long-term dynamics remains uncertain. Here, we upscaled and analyzed two decades (2002-2021) of Boreal-Arctic wetland CH₄ emissions, representing an unprecedented compilation of eddy covariance and chambers observations. We found a robust increasing trend of CH₄ emissions (+8.9%) with strong inter-annual variability. The majority of emission increases occurred in early summer (June and July) and were mainly driven by warming (52.3%) and ecosystem productivity (40.7%). Moreover, a 2 °C temperature anomaly in 2016 led to the largest recorded annual CH₄ emissions (22.3 TgCH₄ yr^-1) over this region, driven primarily by high emissions over Western Siberian lowlands. However, current generation models from Global Carbon Project failed to capture the emission magnitude and trend, and may bias the estimates in future wetland CH₄ emission driven by amplified Boreal-Arctic warming and greening.