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Future socioeconomic climate pathways have regional water-quality consequences whose severity and equity have not yet been fully understood across geographic and economic spectra. We use a process-based, terrestrial-freshwater ecosystem model to project 21st-century river nitrogen loads under these pathways. We find that fertilizer usage is the primary determinant of future river nitrogen loads, changing precipitation and warming have limited impacts, and CO 2 fertilization-induced vegetation growth enhancement leads to modest load reductions. Fertilizer applications to produce bioenergy in climate mitigation scenarios cause larger load increases than in the highest emission scenario. Loads generally increase in low-income regions, yet remain stable or decrease in high-income regions where agricultural advances, low food and feed production and waste, and/or well-enforced air pollution policies balance biofuel-associated fertilizer burdens. Consideration of biofuel production options with low fertilizer demand and rapid transfer of agricultural advances from high- to low-income regions may help avoid inequitable water-quality outcomes from climate mitigation. This study suggests consideration of biofuel production options with low fertilizer demand and rapid transfer of agricultural advances from high- to low-income regions that may help avoid inequitable water-quality outcomes from climate mitigation.

Agricultural practices are a major source of ammonia (NH.sub.3) in the atmosphere, which has implications for air quality, climate, and ecosystems. Due to the rising demand for food and feed production, ammonia emissions are expected to increase significantly by 2100 and would therefore impact atmospheric composition such as nitrate (NO3-) or sulfate (SO42-) particles and affect biodiversity from enhanced deposition. Chemistry-climate models which integrate the key atmospheric physicochemical processes with the ammonia cycle represent a useful tool to investigate present-day and also future reduced nitrogen pathways and their impact on the global scale. Ammonia sources are, however, challenging to quantify because of their dependencies on environmental variables and agricultural practices and represent a crucial input for chemistry-climate models. In this study, we use the chemistry-climate model LMDZ-INCA (Laboratoire de Météorologie Dynamique-INteraction with Chemistry and Aerosols) with agricultural and natural soil ammonia emissions from a global land surface model ORCHIDEE (ORganising Carbon and Hydrology In Dynamic Ecosystems), together with the integrated module CAMEO (Calculation of AMmonia Emissions in ORCHIDEE), for the present-day and 2090-2100 period under two divergent Shared Socioeconomic Pathways (SSP5-8.5 and SSP4-3.4). Future agricultural emissions under the most increased level (SSP4-3.4) have been further exploited to evaluate the impact of enhanced ammonia emissions combined with future contrasting aerosol precursor emissions (SSP1-2.6 - low emissions; SSP3-7.0 - regionally contrasted emissions). We demonstrate that the CAMEO emission set enhances the spatial and temporal variability in the atmospheric ammonia in regions such as Africa, Latin America, and the US in comparison to the static reference inventory (Community Emissions Data System; CEDS) when assessed against satellite and surface network observations. The CAMEO simulation indicates higher ammonia emissions in Africa relative to other studies, which is corroborated by increased current levels of reduced nitrogen deposition (NH.sub.x ), a finding that aligns with observations in west Africa. Future CAMEO emissions lead to an overall increase in the global NH.sub.3 burden ranging from 59 % to 235 %, while the NO3- burden increases by 57 %-114 %, depending on the scenario, even when global NO.sub.x emissions decrease. When considering the most divergent scenarios (SSP5-8.5 and SSP4-3.4) for agricultural ammonia emissions, the direct radiative forcing resulting from secondary inorganic aerosol changes ranges from -114 to -160 mW m.sup.-2 . By combining a high level of NH.sub.3 emissions with decreased or contrasted future sulfate and nitrate emissions, the nitrate radiative effect can either overcompensate (net total sulfate and nitrate effect of -200 mW m.sup.-2) or be offset by the sulfate effect (net total sulfate and nitrate effect of +180mWm-2). We also show that future oxidation of NH.sub.3 could lead to an increase in N.sub.2 O atmospheric sources from 0.43 to 2.10 Tg N.sub.2 O yr.sup.-1 compared to the present-day levels, representing 18 % of the future N.sub.2 O anthropogenic emissions. Our results suggest that accounting for nitrate aerosol precursor emission levels but also for the ammonia oxidation pathway in future studies is particularly important to understand how ammonia will affect climate, air quality, and nitrogen deposition.

Ammonia (NH3) emissions have been on a continuous rise due to extensive fertilizer usage in agriculture and increasing production of manure and livestock. However, the current global-to-national NH3 emission inventories exhibit large uncertainties. We provide atmospheric inversion estimates of the global NH3 emissions over 2019–2022 at 1.27° × 2.5° horizontal and daily (at 10 d scale) resolution. We use IASI-ANNI-NH3-v4 satellite observations, simulations of NH3 concentrations with the chemistry transport model LMDZ-INCA, and the finite difference mass-balance approach for inversions of global NH3 emissions. We take advantage of the averaging kernels provided in the IASI-ANNI-NH3-v4 dataset by applying them consistently to the LMDZ-INCA NH3 simulations for comparison to the observations and then to invert emissions. The average global anthropogenic NH3 emissions over 2019–2022 are estimated as ∼97 (94–100) Tg yr−1, which is ∼61 % (∼55 %–65 %) higher than the prior Community Emissions Data System (CEDS) inventory's anthropogenic NH3 emissions and significantly higher than two other global inventories: CAMS's anthropogenic NH3 emissions (by a factor of ∼1.8) and the Calculation of AMmonia Emissions in ORCHIDEE (CAMEO) agricultural and natural soil NH3 emissions (by ∼1.4 times). The global and regional budgets are mostly within the range of other inversion estimates. The analysis provides confidence in their seasonal variability and continental- to regional-scale budgets. Our analysis shows a rise in NH3 emissions by ∼5 % to ∼37 % during the COVID-19 lockdowns in 2020 over different regions compared to the same-period emissions in 2019. However, this rise is probably due to a decrease in atmospheric NH3 sinks due to the decline in NOx and SO2 emissions during the lockdowns.

Ammonia (NH3) emissions have been on a continuous rise due to extensive fertilizer usage in agriculture and increasing production of manure and livestock. However, the current global-to-national NH3 emission inventories exhibit large uncertainties. We provide atmospheric inversion estimates of the global NH3 emissions over 2019–2022 at 1.27° × 2.5° horizontal and daily (at 10 d scale) resolution. We use IASI-ANNI-NH3-v4 satellite observations, simulations of NH3 concentrations with the chemistry transport model LMDZ-INCA, and the finite difference mass-balance approach for inversions of global NH3 emissions. We take advantage of the averaging kernels provided in the IASI-ANNI-NH3-v4 dataset by applying them consistently to the LMDZ-INCA NH3 simulations for comparison to the observations and then to invert emissions. The average global anthropogenic NH3 emissions over 2019–2022 are estimated as ∼97 (94–100) Tg yr−1, which is ∼61 % (∼55 %–65 %) higher than the prior Community Emissions Data System (CEDS) inventory's anthropogenic NH3 emissions and significantly higher than two other global inventories: CAMS's anthropogenic NH3 emissions (by a factor of ∼1.8) and the Calculation of AMmonia Emissions in ORCHIDEE (CAMEO) agricultural and natural soil NH3 emissions (by ∼1.4 times). The global and regional budgets are mostly within the range of other inversion estimates. The analysis provides confidence in their seasonal variability and continental- to regional-scale budgets. Our analysis shows a rise in NH3 emissions by ∼5 % to ∼37 % during the COVID-19 lockdowns in 2020 over different regions compared to the same-period emissions in 2019. However, this rise is probably due to a decrease in atmospheric NH3 sinks due to the decline in NOx and SO2 emissions during the lockdowns.

Ammonia (NH3) is an important atmospheric constituent. It plays a role in air quality and climate through the formation of ammonium sulfate and ammonium nitrate particles. It has also an impact on ecosystems through deposition processes. About 85 % of NH3 global anthropogenic emissions are related to food and feed production and, in particular, to the use of mineral fertilizers and manure management. Most global chemistry transport models (CTMs) rely on bottom-up emission inventories, which are subject to significant uncertainties. In this study, we estimate emissions from livestock by developing a new module to calculate ammonia emissions from the whole agricultural sector (from housing and storage to grazing and fertilizer application) within the ORCHIDEE (Organising Carbon and Hydrology In Dynamic Ecosystems) global land surface model. We detail the approach used for quantifying livestock feed management, manure application, and indoor and soil emissions and subsequently evaluate the model performance. Our results reflect China, India, Africa, Latin America, the USA, and Europe as the main contributors to global NH3 emissions, accounting for 80 % of the total budget. The global calculated emissions reach 44 TgNyr-1 over the 2005–2015 period, which is within the range estimated by previous work. Key parameters (e.g., the pH of the manure, timing of N application, and atmospheric NH3 surface concentration) that drive the soil emissions have also been tested in order to assess the sensitivity of our model. Manure pH is the parameter to which modeled emissions are the most sensitive, with a 10 % change in emissions per percent change in pH. Even though we found an underestimation in our emissions over Europe (-26 %) and an overestimation in the USA (+56 %) compared with previous work, other hot spot regions are consistent. The calculated emission seasonality is in very good agreement with satellite-based emissions. These encouraging results prove the potential of coupling ORCHIDEE land-based emissions to CTMs, which are currently forced by bottom-up anthropogenic-centered inventories such as the CEDS (Community Emissions Data System).

Ammonia (NH.sub.3) emissions have been on a continuous rise due to extensive fertilizer usage in agriculture and increasing production of manure and livestock. However, the current global-to-national NH.sub.3 emission inventories exhibit large uncertainties. We provide atmospheric inversion estimates of the global NH.sub.3 emissions over 2019-2022 at 1.27° x 2.5° horizontal and daily (at 10 d scale) resolution. We use IASI-ANNI-NH3-v4 satellite observations, simulations of NH.sub.3 concentrations with the chemistry transport model LMDZ-INCA, and the finite difference mass-balance approach for inversions of global NH.sub.3 emissions. We take advantage of the averaging kernels provided in the IASI-ANNI-NH3-v4 dataset by applying them consistently to the LMDZ-INCA NH.sub.3 simulations for comparison to the observations and then to invert emissions. The average global anthropogenic NH.sub.3 emissions over 2019-2022 are estimated as â¼97 (94-100) Tg yr.sup.-1, which is â¼61 % (â¼55 %-65 %) higher than the prior Community Emissions Data System (CEDS) inventory's anthropogenic NH.sub.3 emissions and significantly higher than two other global inventories: CAMS's anthropogenic NH.sub.3 emissions (by a factor of â¼1.8) and the Calculation of AMmonia Emissions in ORCHIDEE (CAMEO) agricultural and natural soil NH.sub.3 emissions (by â¼1.4 times). The global and regional budgets are mostly within the range of other inversion estimates. The analysis provides confidence in their seasonal variability and continental- to regional-scale budgets. Our analysis shows a rise in NH.sub.3 emissions by â¼5 % to â¼37 % during the COVID-19 lockdowns in 2020 over different regions compared to the same-period emissions in 2019. However, this rise is probably due to a decrease in atmospheric NH.sub.3 sinks due to the decline in NO.sub.x and SO.sub.2 emissions during the lockdowns.

Global ammonia emissions from the CAMEO process-based model (general model description can be found in Beaudor et al., 2023, GMD; https://doi.org/10.5194/gmd-16-1053-2023). Monthly files containing global NH3 emissions in gN.m2.yr-1 (2.5° lon x 1.27° lat; IPSL-CM6A-LR Earth System Model resolution): 1) total agricultural emissions (TOT_AGRI; the sum of manure management and agricultural soil emissions) 2) manure management emissions (MANURE_MANAG.) 3) agricultural soil emissions (SOIL_AGRI) 4) natural soil emissions (SOIL_NAT) corrected for baresoil (excluding Sahara in this new version) 5) Fraction of continent (CONT_FRAC) from the model to use for CTM prescription or global budget calculation The four files correspond to a specific simulation using input4MIPs forcing files : - Present-day simulation from 2000 to 2014 - Future simulation from 2015 to 2100 under scenario SSP-2.45 - Future simulation from 2015 to 2100 under scenario SSP-4.34 - Future simulation from 2015 to 2100 under scenario SSP-5.85 Note that these datasets have been prepared in the scope of a publication to be submitted to the ERL journal. Beaudor, M., N. Vuichard, J. Lathière, D. Hauglustaine., Historical and future ammonia emissions database (2000-2100) from the CAMEO process-based model, in preparation.