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1. California dominates U.S. emissions of the pesticide and potent greenhouse gas sulfuryl fluoride

   https://doi.org/10.1038/s43247-024-01294-x  

   Gaeta, Dylan C.; Mühle, Jens; Vimont, Isaac J.; Crotwell, Molly; Hu, Lei; Miller, John B.; McKain, Kathryn; Baier, Bianca C.; Zhang, Mingyang; Bao, Jianing; et al (April 2024, Communications Earth & Environment)

   Abstract Sulfuryl fluoride (SO₂F₂) is a synthetic pesticide and a potent greenhouse gas that is accumulating in the global atmosphere. Rising emissions are a concern since SO₂F₂has a relatively long atmospheric lifetime and a high global warming potential. The U.S. is thought to contribute substantially to global SO₂F₂emissions, but there is a paucity of information on how emissions of SO₂F₂are distributed across the U.S., and there is currently no inventory of SO₂F₂emissions for the U.S. or individual states. Here we provide an atmospheric measurement-based estimate of U.S. SO₂F₂emissions using high-precision SO₂F₂measurements from the NOAA Global Greenhouse Gas Reference Network (GGGRN) and a geostatistical inverse model. We find that California has the largest SO₂F₂emissions among all U.S. states, with the highest emissions from southern coastal California (Los Angeles, Orange, and San Diego counties). Outside of California, only very small and infrequent SO₂F₂emissions are detected by our analysis of GGGRN data. We find that California emits 60-85% of U.S. SO₂F₂emissions, at a rate of 0.26 ( ± 0.10) Gg yr⁻¹. We estimate that emissions of SO₂F₂from California are equal to 5.5–12% of global SO₂F₂emissions. 

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2. Constraining U.S. Sulfuryl Fluoride Emissions With Atmospheric Measurements and a Geostatistical Inverse Model

   Gaeta, Dylan C; Muhle, Jens; Vimont, Isaac J; Crotwell, Molly; McKain, Kathryn; Baier, Bianca; Miller, John B; Zhang, Mingyang; Bao, Jianing; Miller, Benjamin R; et al (December 2022, American Geophysical Union 2022 Fall Meeting Abstracs)

   The mean abundance of sulfuryl fluoride (SO2F2) in the global atmosphere has been increasing since at least the 1970s, with ambient air mole fractions exceeding 2.5 parts per trillion (ppt) today. SO2F2 is a synthetic pesticide and a potent greenhouse gas (GHG) used for fumigation - predominantly of wooden structures, and increasingly for agricultural and commodity products as well. Worldwide use of SO2F2 has surged since the use of methyl bromide (CH3Br) for fumigation was largely phased out under the Montreal Protocol. Recent atmospheric measurements and modeling work from the Advanced Global Atmospheric Gases Experiment (AGAGE) indicates that global emissions of SO2F2 have reached a historic high in recent years at roughly 3.0 Gg SO2F2 yr-1. However, under the current UNFCCC emissions reporting guidelines, countries are not required to report their emissions of SO2F2, and thus SO2F2 is not included in most national GHG emissions inventories, leading to a scarcity of information on the global distribution and magnitude of SO2F2 emissions. In the U.S., California is the only state that keeps a public record of statewide SO2F2 use, despite the gas being used for termite fumigation in other warm-climate coastal states such as Florida. To fill this information gap, we use flask-sample measurements of SO2F2 from the NOAA Global Greenhouse Gas Reference Network (GGGRN) and a geostatistical inverse model (GIM) to provide a measurement-based top-down constraint on the magnitude and spatial distribution of SO2F2 emissions across the continental U.S. We find that California emits the vast majority (>90%) of U.S. SO2F2 emissions, with the largest emissions coming from the California South Coast (Los Angeles, Orange, and San Diego Counties), and the second largest from the San Francisco Bay Area. Outside of California, SO2F2 emissions are rarely detected by the NOAA GGGRN. However, despite California's oversized contribution to U.S. SO2F2 emissions, a significantly large fraction (>50%) of the 3.0 Gg yr-1 global emissions budget is still emitted elsewhere. We will present insights gained from the NOAA GGGRN measurements and our inverse modeling work, including a case study on California's SO2F2 emissions and reconciliation with California state SO2F2 usage records. 

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3. A comprehensive and synthetic dataset for global, regional, and national greenhouse gas emissions by sector 1970–2018 with an extension to 2019

   https://doi.org/10.5194/essd-13-5213-2021  

   Minx, Jan C.; Lamb, William F.; Andrew, Robbie M.; Canadell, Josep G.; Crippa, Monica; Döbbeling, Niklas; Forster, Piers M.; Guizzardi, Diego; Olivier, Jos; Peters, Glen P.; et al (January 2021, Earth System Science Data)

   Abstract. To track progress towards keeping global warming well below 2 ∘C or even 1.5 ∘C, as agreed in the Paris Agreement, comprehensiveup-to-date and reliable information on anthropogenic emissions and removalsof greenhouse gas (GHG) emissions is required. Here we compile a new synthetic dataset on anthropogenic GHG emissions for 1970–2018 with afast-track extension to 2019. Our dataset is global in coverage and includesCO2 emissions, CH4 emissions, N2O emissions, as well as those from fluorinated gases (F-gases: HFCs, PFCs, SF6, NF3) andprovides country and sector details. We build this dataset from the version 6 release of the Emissions Database for Global Atmospheric Research (EDGAR v6) and three bookkeeping models for CO2 emissions from land use,land-use change, and forestry (LULUCF). We assess the uncertainties of global greenhouse gases at the 90 % confidence interval (5th–95thpercentile range) by combining statistical analysis and comparisons ofglobal emissions inventories and top-down atmospheric measurements with anexpert judgement informed by the relevant scientific literature. We identifyimportant data gaps for F-gas emissions. The agreement between our bottom-up inventory estimates and top-downatmospheric-based emissions estimates is relatively close for some F-gasspecies (∼ 10 % or less), but estimates can differ by an order of magnitude or more for others. Our aggregated F-gas estimate is about 10 % lower than top-down estimates in recent years. However, emissions from excluded F-gas species such aschlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs) arecumulatively larger than the sum of the reported species. Using globalwarming potential values with a 100-year time horizon from the Sixth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC),global GHG emissions in 2018 amounted to 58 ± 6.1 GtCO2 eq.consisting of CO2 from fossil fuel combustion and industry (FFI) 38 ± 3.0 GtCO2, CO2-LULUCF 5.7 ± 4.0 GtCO2, CH4 10 ± 3.1 GtCO2 eq., N2O2.6 ± 1.6 GtCO2 eq., and F-gases 1.3 ± 0.40 GtCO2 eq. Initial estimates suggest further growth of 1.3 GtCO2 eq. in GHG emissions to reach 59 ± 6.6 GtCO2 eq. by 2019. Our analysis ofglobal trends in anthropogenic GHG emissions over the past 5 decades (1970–2018) highlights a pattern of varied but sustained emissions growth. There is high confidence that global anthropogenic GHG emissions haveincreased every decade, and emissions growth has been persistent across the different (groups of) gases. There is also high confidence that globalanthropogenic GHG emissions levels were higher in 2009–2018 than in any previous decade and that GHG emissions levels grew throughout the most recent decade. While the average annual GHG emissions growth rate slowed between2009 and 2018 (1.2 % yr−1) compared to 2000–2009 (2.4 % yr−1), the absolute increase in average annual GHG emissions by decade was neverlarger than between 2000–2009 and 2009–2018. Our analysis further revealsthat there are no global sectors that show sustained reductions in GHGemissions. There are a number of countries that have reduced GHG emissionsover the past decade, but these reductions are comparatively modest andoutgrown by much larger emissions growth in some developing countries suchas China, India, and Indonesia. There is a need to further develop independent, robust, and timely emissions estimates across all gases. As such, tracking progress in climate policy requires substantial investmentsin independent GHG emissions accounting and monitoring as well as in national and international statistical infrastructures. The data associatedwith this article (Minx et al., 2021) can be found at https://doi.org/10.5281/zenodo.5566761. 

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4. Contributions of healthier diets and agricultural productivity toward sustainability and climate goals in the United States

   https://doi.org/10.1007/s11625-022-01232-w  

   Wu, Grace C.; Baker, Justin S.; Wade, Christopher M.; McCord, Gordon C.; Fargione, Joseph E.; Havlik, Petr (November 2022, Sustainability Science)

   Abstract Meeting ambitious climate targets will require deploying the full suite of mitigation options, including those that indirectly reduce greenhouse-gas (GHG) emissions. Healthy diets have sustainability co-benefits by directly reducing livestock emissions as well as indirectly reducing land use emissions. Increased crop productivity could indirectly avoid emissions by reducing cropland area. However, there is disagreement on the sustainability of proposed healthy U.S. diets and a lack of clarity on how long-term sustainability benefits may change in response to shifts in the livestock sector. Here, we explore the GHG emissions impacts of seven scenarios that vary U.S. crop yields and healthier diets in the U.S. and overseas. We also examine how impacts vary across assumptions of future ruminant livestock productivity and ruminant stocking density in the U.S. We employ two complementary land use models—the US FABLE Calculator, an agricultural and forestry sector accounting model with high agricultural commodity representation, and GLOBIOM, a spatially explicit partial equilibrium optimization model for global land use systems. Results suggest that healthier U.S. diets that follow the Dietary Guidelines for Americans reduce agricultural and land use greenhouse gas emissions by 25–57% (approx 120–310 MtCO_2e/y) and pastureland area by 28–38%. The potential emissions and land sparing benefits of U.S. agricultural productivity growth are modest within the U.S. due to the increasing comparative advantage of U.S. crops. Our findings suggest that healthy U.S. diets can significantly contribute toward meeting U.S. long-term climate goals for the land use sectors. 

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5. Improved global wetland carbon isotopic signatures support post-2006 microbial methane emission increase

   https://doi.org/10.1038/s43247-022-00488-5  

   Oh, Youmi; Zhuang, Qianlai; Welp, Lisa R.; Liu, Licheng; Lan, Xin; Basu, Sourish; Dlugokencky, Edward J.; Bruhwiler, Lori; Miller, John B.; Michel, Sylvia E.; et al (December 2022, Communications Earth & Environment)

   Abstract Atmospheric concentrations of methane, a powerful greenhouse gas, have strongly increased since 2007. Measurements of stable carbon isotopes of methane can constrain emissions if the isotopic compositions are known; however, isotopic compositions of methane emissions from wetlands are poorly constrained despite their importance. Here, we use a process-based biogeochemistry model to calculate the stable carbon isotopic composition of global wetland methane emissions. We estimate a mean global signature of −61.3 ± 0.7‰ and find that tropical wetland emissions are enriched by ~11‰ relative to boreal wetlands. Our model shows improved resolution of regional, latitudinal and global variations in isotopic composition of wetland emissions. Atmospheric simulation scenarios with the improved wetland isotopic composition suggest that increases in atmospheric methane since 2007 are attributable to rising microbial emissions. Our findings substantially reduce uncertainty in the stable carbon isotopic composition of methane emissions from wetlands and improve understanding of the global methane budget. 

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