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METHANE (CH4) IS AN IMPORTANT LONG-LIVED GREENHOUSE GAS WHOSE GLOBAL SOURCES AND SINKS REQUIRE MORE INVESTIGATION TO BETTER UNDERSTAND THEIR ANTHROPOGENIC AND NATURAL CONTRIBUTIONS TO PAST, CURRENT, AND FUTURE RADIATIVE FORCING. RECENT WORK BY THIS T
Other Administrative Action $0 4/15/22 6
METHANE (CH4) IS AN IMPORTANT LONG-LIVED GREENHOUSE GAS WHOSE GLOBAL SOURCES AND SINKS REQUIRE MORE INVESTIGATION TO BETTER UNDERSTAND THEIR ANTHROPOGENIC AND NATURAL CONTRIBUTIONS TO PAST, CURRENT, AND FUTURE RADIATIVE FORCING. RECENT WORK BY THIS TEAM (SCHWIETZKE ET AL., PUBLISHED IN NATURE ON OCTOBER 6, 2016) SUGGESTS A REVISION OF THE 1985-2013 GLOBAL CH4 BUDGET BY USING THE MOST EXTENSIVE ISOTOPIC (DELTA13C-CH4) SOURCE SIGNATURE DATABASE TO-DATE. THE CONSISTENCY REQUIREMENT BETWEEN THIS DATABASE AND ATMOSPHERIC DELTA13C-CH4 DATA HAS INCREASED GLOBAL FOSSIL FUEL CH4 EMISSIONS BY 60-110 PERCENT COMPARED TO PREVIOUS TOP-DOWN ESTIMATES, WHICH IS OFFSET BY LOWER MICROBIAL EMISSIONS. HOWEVER, WE ALSO FOUND THAT GLOBAL FOSSIL FUEL CH4 EMISSIONS HAVE NOT INCREASED OVER THE PAST THREE DECADES, CONSISTENT WITH SCHAEFER ET AL. (2016, SCIENCE), BUT IN DISAGREEMENT WITH OTHER STUDIES (E.G., BOUSQUET ET AL. 2006, RICE ET AL. 2016). 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 DELTA13C-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 DELTA13C-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. THIS PROJECT ADDRESSES THE ROSES A.28 (INTERDISCIPLINARY SCIENCE) PROGRAM'S AIM OF (I) BETTER UNDERSTANDING THE GLOBAL SOURCES AND SINKS OF CH4, (II) DRAWING ON REMOTE SENSING DATA, (III) INVESTIGATING THE CAUSALITIES OF BIOLOGICAL PROCESSES AND OBSERVATIONS, (IV) AND BEING TRULY INTERDISCIPLINARY IN SCOPE. USING REMOTE SENSING DATA IN COMBINATION WITH IN SITU DATA OF BOTH CH4 AND ISOTOPES WILL PROVIDE STRONG CONSTRAINTS ON THE CURRENT AND FUTURE GLOBAL CH4 BUDGET.
Other Administrative Action $0 3/19/20