We estimate the causal contributions of spatiotemporal changes in temperature (T) and precipitation (Pr) to changes in Earth’s atmospheric methane concentration (C_CH4) and its isotope ratio δ¹³CH₄ over the last four decades. We identify oscillations between positive and negative feedbacks, showing that both contribute to increasing C_CH4. Interannually, increased emissions via positive feedbacks (e.g. wetland emissions and wildfires) with higher land surface air temperature (LSAT) are often followed by increasing C_CH4 due to weakened methane sink via atmospheric ^•OH, via negative feedbacks with lowered sea surface temperatures (SST), especially in the tropics. Over decadal time scales, we find alternating rate-limiting factors for methane oxidation: when C_CH4 is limiting, positive methane-climate feedback via direct oceanic emissions dominates; when ^•OH is limiting, negative feedback is favoured. Incorporating the interannually increasing C_CH4 via negative feedbacks gives historical methane-climate feedback sensitivity ≈ 0.08 W m⁻² °C⁻¹, much higher than the IPCC AR6 estimate.

我们估计了过去 40 年间温度 ( T ) 和降水量 ( Pr ) 的时空变化对地球大气甲烷浓度 ( C _CH4 ) 及其同位素比δ 13 ^CH 4_变化的因果贡献。我们确定了正反馈和负反馈之间的振荡，表明两者都有助于增加C _CH4。年际而言，随着地表气温 ( LSAT ) 的升高，通过正反馈（例如湿地排放和野火）增加排放量通常会随着大气中的甲烷汇减弱而导致C _CH4增加^• OH，通过降低海面温度 ( SST ) 的负反馈，特别是在热带地区。在十年的时间尺度上，我们发现甲烷氧化的交替速率限制因素：当C _CH4受到限制时，通过直接海洋排放的甲烷-气候正反馈占主导地位；当^• OH 受到限制时，负反馈是有利的。通过负反馈结合年际增加的C _CH4得出历史甲烷-气候反馈灵敏度 ≈ 0.08 W m ^-2  °C ^-1，远高于 IPCC AR6 的估计值。