GlobalM

Process-level investigation of revised global methane budget based on in situ and remote sensing of atmospheric composition and the land surface

Duration:07/1/2017- 06/30/2020
Award Amount:$490,679 out of $1,282,569

Participants
PI in collaboration with Stefan Schwietzke, Sourish Basu; Lori Bruhwiler; Owen Sherwood; John Miller; Gabrielle Petron; Sylvia Englund Michel; Ed Dlugokencky; Pieter Tans; Giuseppe Etiope; Martin Schoell; Bell, Jennifer

Project Objectives

The objectives of the proposed research are to identify the spatial patterns that would be consistent with these revisions (including the upward correction from the oil, gas, and coal industries and geological seepage), and to better understand the individual factors influencing wetland methanogenesis and their contribution to global microbial CH4 emissions and their trends. This will be achieved in a global inverse model study based on a combination of available data from in situ measured and remotely sensed trace gases, remote sensing of inundation area, and our large database of over 9,000 δ13C-CH4 source signatures. The isotopic database will provide source- and region-specific signatures not available in previous studies. Generating revised fossil fuel and geologic CH4 and δ13C-CH4 source signature maps will improve our ability to discriminate between natural microbial and anthropogenic microbial emissions. That is, the spatial footprint of the revised fossil and geological CH4 emissions may provide spatial information that suggests reductions in microbial emissions in spatially distinct ways since the global spatial pattern of wetlands is different from ruminants and landfills. This results in a tighter constraint for attributing emissions to natural microbial and anthropogenic microbial processes. We will investigate CH4 emissions from wetlands in more detail because globally they are among the largest single CH4 sources, they have a strong impact on the observed CH4 isotopic composition in the atmosphere, and they are the most likely emission category to be impacted by climate change. Wetland CH4 emission estimates will be based on a combination of remote sensing of inundation area and process-based biosphere models. Using the resulting range of scenarios as inputs to our global inverse model (above, including isotopic constraints), we expect an improved understanding of the mechanisms driving the spatial and temporal variations in wetland CH4 emissions. This improved understanding of the driving forces behind wetland CH4 sources will help us improve predictions of future emissions from this source, allowing a better understanding of potential CH4–climate feedbacks. The optimized gridded emissions and associated isotopic signatures resulting from this work will also provide the ground work for further research, e.g., including additional observational constraints that will be available in the future.