Department of Earth Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK.
NCAS, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
Philos Trans A Math Phys Eng Sci. 2021 Nov 15;379(2210):20200457. doi: 10.1098/rsta.2020.0457. Epub 2021 Sep 27.
The causes of methane's renewed rise since 2007, accelerated growth from 2014 and record rise in 2020, concurrent with an isotopic shift to values more depleted in C, remain poorly understood. This rise is the dominant departure from greenhouse gas scenarios that limit global heating to less than 2°C. Thus a comprehensive understanding of methane sources and sinks, their trends and inter-annual variations are becoming more urgent. Efforts to quantify both sources and sinks and understand latitudinal and seasonal variations will improve our understanding of the methane cycle and its anthropogenic component. Nationally declared emissions inventories under the UN Framework Convention on Climate Change (UNFCCC) and promised contributions to emissions reductions under the UNFCCC Paris Agreement need to be verified independently by top-down observation. Furthermore, indirect effects on natural emissions, such as changes in aquatic ecosystems, also need to be quantified. Nitrous oxide is even more poorly understood. Despite this, options for mitigating methane and nitrous oxide emissions are improving rapidly, both in cutting emissions from gas, oil and coal extraction and use, and also from agricultural and waste sources. Reductions in methane and nitrous oxide emission are arguably among the most attractive immediate options for climate action. This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 1)'.
自 2007 年以来，甲烷排放量再次上升、2014 年以来加速增长以及 2020 年创纪录增长的原因，以及与碳同位素分馏值降低有关的协同变化，仍然知之甚少。这种增长是对温室气体情景的主要偏离，温室气体情景将全球升温限制在 2°C 以下。因此，对甲烷源汇及其趋势和年际变化的综合理解变得更加紧迫。量化源汇并理解纬度和季节性变化的努力将提高我们对甲烷循环及其人为成分的理解。《联合国气候变化框架公约》（UNFCCC）下国家申报的排放清单以及《巴黎协定》下承诺的减排贡献需要通过自上而下的观测进行独立验证。此外，还需要量化水生生态系统变化等对自然排放的间接影响。一氧化二氮的了解甚至更少。尽管如此，无论是从天然气、石油和煤炭开采和利用，还是从农业和废物来源减排的角度来看，减少甲烷和一氧化二氮排放的选择都在迅速增加。减少甲烷和一氧化二氮排放可以说是最有吸引力的气候行动即时选择之一。本文是关于“甲烷上升：变暖正在助长变暖吗？（第 1 部分）”讨论的一部分。
