CAREER: Methane emissions from the US and Canada -- novel insights from an expanding observation network

就其对气候的影响而言，甲烷是仅次于二氧化碳的第二大温室气体。与二氧化碳(CO2)相比，甲烷(CH4)在大气中的停留时间要短得多，约为9-12年，而二氧化碳为300-1000年。然而，在100年的时间里，甲烷的全球变暖潜力是二氧化碳的28倍。在美国，几个联邦和州机构已经制定了减少甲烷排放的目标。然而，目前关于甲烷排放的知识和核算以及这些排放如何随时间变化存在很大的不确定性。这个职业项目的首要目标是量化美国、加拿大和墨西哥在2007-2026年间近20年来甲烷排放量的变化。为了推进这一目标，首席调查员(PI)建议利用不断扩大的大气甲烷观测网络(从飞机、电视塔和卫星收集)和最近在反向建模(算法和软件)方面的进展，这些进展使得能够使用大规模卫星数据集估计北美以前未解释的CH4排放源。该项目的成功完成将通过产生新的数据和基础知识造福社会，这些数据和基础知识可用于(1)更好地了解和量化北美的CH4排放，以及(2)指导旨在减少甲烷等强有力温室气体全球排放的政策和解决方案的实施和评估。通过学生教育和培训，包括指导约翰霍普金斯大学的一名研究生，将进一步造福社会。北美(美国、加拿大和墨西哥)的甲烷(CH4)排放在过去20年中发生了显著变化，这在很大程度上是由于石油和天然气产量的大幅增加。这一职业项目将解决北美目前对甲烷排放的理解和量化方面的关键知识差距。这项研究的具体目标是：(1)利用地面观测和卫星观测相结合的方法，量化北美人为甲烷排放量在20年(2007-2026年)期间的变化；(2)利用对流层监测仪(Tropomi)的卫星观测，评估北美甲烷大排放国和超排放国的变化贡献；(3)估计美国、加拿大和墨西哥湿地甲烷通量的分布和年际变化，4)量化湿地甲烷排放通量与主要环境驱动因素之间的关系，目的是建立更准确、更稳健的湿地甲烷排放过程模型。这项研究的成功完成有可能通过利用扩大的大气甲烷观测网络和新的反向建模方法产生变革性影响，从而能够利用大规模卫星数据集查明和量化北美以前下落不明的甲烷排放源。为了实施这一职业项目的教育和外展活动，首席调查员(PI)建议利用约翰·霍普金斯大学(JHU)现有的计划和资源，开发和提供两项以温室气体(GHG)排放和气候变化(CC)为重点的综合教育活动。对于第一个教育活动，PI将与JHU教育外联中心合作，为巴克莱暑期学院注册的巴尔的摩市中学生创建关于温室气体排放和CC的动手活动。对于第二个教育活动，PI建议在JHU开发一个关于温室气体排放和气候政策的跨学科本科课程，其中将包括与科学家、工程师和政策专家的讨论。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Methane is the second-most important greenhouse gas (GHG) after carbon dioxide in terms of its climate impact. Compared to carbon dioxide (CO2), methane (CH4) has a much shorter residence time in the atmosphere approximately 9-12 years compared to 300-1000 years for CO2. However, the global warming potential of methane is 28 times larger than that of carbon dioxide over a 100-year period. In the United States, several federal and state agencies have set goals for reducing methane emissions. However, there are large uncertainties in the current knowledge and accounting of CH4 emissions and how these emissions are changing over time. The overarching goal of this CAREER project is to quantify how methane emissions in the United States, Canada, and Mexico have changed over nearly two decades from 2007-2026. To advance this goal, the Principal Investigator (PI) proposes to leverage an expanding network of atmospheric methane observations (collected from airplanes, atop TV towers, and satellites) and recent advances in inverse modeling (algorithms and software) that enable the estimations of previously unaccounted sources of CH4 emissions in North America using massive satellite datasets. The successful completion of this project will benefit society through the generation of new data and fundamental knowledge that could be used to (1) better understand and quantify CH4 emissions in North America, and (2) guide the implementation and evaluation of policies and solutions designed to reduce the global emissions of a potent GHG such as methane. Further benefits to society will be achieved through student education and training including the mentoring of a graduate student at Johns Hopkins University.Methane (CH4) emissions in North America (United States, Canada, and Mexico) have changed significantly during the past twenty years driven to a large extent by a substantial increase in oil and gas production. This CAREER project will address critical knowledge gaps in the current level of understanding and quantification of CH4 emissions in North America. The specific objectives of the research are to: (1) quantify how anthropogenic methane emissions in North America have changed over two decades (2007-2026) using a combination of ground-based and satellite observations, (2) evaluate the changing contribution of large and super-emitters of methane in North America using satellite observations from the TROPOspheric Monitoring Instrument (TROPOMI), (3) estimate the distribution and year-to-year variability of CH4 fluxes from wetlands in the United States, Canada, and Mexico, and 4) quantify the relationships between CH4 fluxes from wetlands and key environmental drivers with the goal of developing more accurate and robust process models of methane emissions by wetlands. The successful completion of this research has the potential for transformative impact through the leveraging of an expanded network of atmospheric methane observations and new approaches to inverse modeling that could enable the identification and quantification of previously unaccounted sources of CH4 emissions in North America using massive satellite datasets. To implement the educational and outreach activities of this CAREER project, the Principal Investigator (PI) proposes to leverage existing programs and resources at Johns Hopkins University (JHU) to develop and deliver two integrated educational activities focused on greenhouse gas (GHG) emissions and climate change (CC). For the first educational activity, the PI will work with the JHU Center for Educational Outreach to create hands-on activities about GHG emissions and CC for Baltimore City middle school students enrolled in the Barclay Summer Academy. For the second educational activity, the PI proposes to develop an interdisciplinary undergraduate course on GHG emissions and climate policy at JHU that will include discussions with scientists, engineers, and policy experts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.