Advancing Scientific Understanding of the Global Methane Budget in Support of the Paris Agreement
Advancing Scientific Understanding of the Global Methane Budget in Support of the Paris Agreement
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DOI：
10.1029/2018gb006065
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发表时间：
2019-12-23
影响因子：
5.2
通讯作者：
Manning, Martin
中科院分区：
文献类型：
--
作者：
Ganesan, Anita L.;Schwietzke, Stefan;Manning, Martin
2015年《联合国气候变化框架公约巴黎协定》旨在2100年将全球平均气温升幅控制在远低于工业化前水平2摄氏度的水平。其成功的关键是减少大气甲烷(CH4)的丰度，甲烷是第二大最重要的人为温室气体。如果要实现这一减排目标，个别国家必须在其国家决定的捐款中制定和实现减排目标，并定期进行可独立核查的全球评估。《巴黎协定》的目标已经设定，现在必须有能力确定甲烷排放量是否真的在减少。然而，目前，科学家在全球和国家范围内准确量化甲烷排放并诊断过去几十年来大气摩尔分数趋势发生变化的机制方面存在重大限制。例如，在2007年，摩尔分数在十年几乎没有增长之后，突然开始在全球范围内上升。十多年过去了，科学家们仍在争论这种增长背后的机制。这项研究回顾了我们目前诊断大气CH4变化驱动因素的主要方法和局限性，并提出了在未来十年改进这一能力的方法。建议包括：(1)改进甲烷排放主要部门的基于过程的模型--拟议的发展呼吁扩大热带湿地通量测量，将遥感产品用于改进湿地面积和动态的测量，扩大对设施和区域一级化石燃料排放的测量，扩大送往垃圾填埋场的废物成分和所实施的废水处理系统类型的国别数据，描述和说明作物生长季节的时间概况，实施与反刍动物排放有关的参数，例如动物饲料，以及改进对与农业和砍伐森林有关的小火的探测；改进甲烷摩尔分数及其同位素变化的测量--发展包括在背景地点扩大垂直剖面，扩大密集的城市测量网络，更加侧重于相对贫穷的国家，提高(CH4)-C-13、CH3D、(CH4)-C-14和成团同位素的同位素比率测量的精度，为国际规模的开发创建同位素参考材料，以及扩大同位素来源特征的空间和时间特征；以及(3)改进从大气测量得出排放的反向模拟系统--在羟基自由基量化、通过验证化学运输模型对系统不确定性进行量化、使用来源示踪剂估计部门一级排放以及编制时间和空间分辨的国家清单方面提出了进展。这些建议和其他建议都是针对甲烷科学的主要领域提出的，目的是在今后十年提高按气候政策取得成功所需的规模量化大气甲烷预算的能力。
The 2015 Paris Agreement of the United Nations Framework Convention on Climate Change aims to keep global average temperature increases well below 2 degrees C of preindustrial levels in the Year 2100. Vital to its success is achieving a decrease in the abundance of atmospheric methane (CH4), the second most important anthropogenic greenhouse gas. If this reduction is to be achieved, individual nations must make and meet reduction goals in their nationally determined contributions, with regular and independently verifiable global stock taking. Targets for the Paris Agreement have been set, and now the capability must follow to determine whether CH4 reductions are actually occurring. At present, however, there are significant limitations in the ability of scientists to quantify CH4 emissions accurately at global and national scales and to diagnose what mechanisms have altered trends in atmospheric mole fractions in the past decades. For example, in 2007, mole fractions suddenly started rising globally after a decade of almost no growth. More than a decade later, scientists are still debating the mechanisms behind this increase. This study reviews the main approaches and limitations in our current capability to diagnose the drivers of changes in atmospheric CH4 and, crucially, proposes ways to improve this capability in the coming decade. Recommendations include the following: (i) improvements to process-based models of the main sectors of CH4 emissions-proposed developments call for the expansion of tropical wetland flux measurements, bridging remote sensing products for improved measurement of wetland area and dynamics, expanding measurements of fossil fuel emissions at the facility and regional levels, expanding country-specific data on the composition of waste sent to landfill and the types of wastewater treatment systems implemented, characterizing and representing temporal profiles of crop growing seasons, implementing parameters related to ruminant emissions such as animal feed, and improving the detection of small fires associated with agriculture and deforestation; (ii) improvements to measurements of CH4 mole fraction and its isotopic variations-developments include greater vertical profiling at background sites, expanding networks of dense urban measurements with a greater focus on relatively poor countries, improving the precision of isotopic ratio measurements of (CH4)-C-13, CH3D, (CH4)-C-14, and clumped isotopes, creating isotopic reference materials for international-scale development, and expanding spatial and temporal characterization of isotopic source signatures; and (iii) improvements to inverse modeling systems to derive emissions from atmospheric measurements-advances are proposed in the areas of hydroxyl radical quantification, in systematic uncertainty quantification through validation of chemical transport models, in the use of source tracers for estimating sector-level emissions, and in the development of time and space resolved national inventories. These and other recommendations are proposed for the major areas of CH4 science with the aim of improving capability in the coming decade to quantify atmospheric CH4 budgets on the scales necessary for the success of climate policies.