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Impact of interannual and multidecadal trends on methane-climate feedbacks and sensitivity
Nature Communications ( IF 14.7 ) Pub Date : 2022-06-23 , DOI: 10.1038/s41467-022-31345-w
Chin-Hsien Cheng 1, 2 , Simon A T Redfern 2, 3
Affiliation  

We estimate the causal contributions of spatiotemporal changes in temperature (T) and precipitation (Pr) to changes in Earth’s atmospheric methane concentration (CCH4) and its isotope ratio δ13CH4 over the last four decades. We identify oscillations between positive and negative feedbacks, showing that both contribute to increasing CCH4. Interannually, increased emissions via positive feedbacks (e.g. wetland emissions and wildfires) with higher land surface air temperature (LSAT) are often followed by increasing CCH4 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 CCH4 is limiting, positive methane-climate feedback via direct oceanic emissions dominates; when OH is limiting, negative feedback is favoured. Incorporating the interannually increasing CCH4 via negative feedbacks gives historical methane-climate feedback sensitivity ≈ 0.08 W m−2 °C−1, much higher than the IPCC AR6 estimate.



中文翻译:

年际和多年代际趋势对甲烷气候反馈和敏感性的影响

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。

更新日期:2022-06-23
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