| Summary: | Wetland methane (CH 4 ) 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) ofBoreal-ArcticwetlandCH 4 emissions, representingan unprecedented compilation of eddy covariance and chambers observations. We found a robust increasing trend of CH 4 emissions (+8.9%) with strong inter-annual variability. The majority of emission increasesoccurred in early summer (June and July) andwere mainly driven by warming (52.3%) and ecosystem productivity (40.7%). Moreover, a 2 °C temperature anomaly in 2016 led to the largest recorded annualCH 4 emissions (22.3 TgCH 4 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 CH 4 emission driven by amplified Boreal-Arctic warming and greening.
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