Source contributions to sulfur and nitrogen deposition – an HTAP II multi-model study on hemispheric transport

Tan, Jiani; Fu, Joshua S.; Dentener, Frank; Sun, Jian; Emmons, L. K.; Tilmes, Simone; Flemming, Johannes; Bian, Huisheng; Zhu, Qiao; Yang, Chia Ping Huang; Keating, Terry

doi:10.5194/acp-18-12223-2018

Cited by 24 publications

(9 citation statements)

References 77 publications

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“…Hence, by keeping natural sources of emissions fixed at present-day levels, our results may underestimate the future aerosols loads. Moreover, a recent review of climate feedbacks on aerosol distributions suggests that, in regions where anthropogenic aerosol loadings decrease, the impacts of climate on the variability of natural aerosols increase (Tegen and Schepanski, 2018). Changing climatic conditions may also affect the radiative forcing through changing cloud distributions and surface albedo.…”

Section: Discussionmentioning

confidence: 99%

Anthropogenic aerosol forcing under the Shared Socioeconomic Pathways

2019

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Abstract. Emissions of anthropogenic aerosols are expected to change drastically over the coming decades, with potentially significant climate implications. Using the most recent generation of harmonized emission scenarios, the Shared Socioeconomic Pathways (SSPs) as input to a global chemistry transport and radiative transfer model, we provide estimates of the projected future global and regional burdens and radiative forcing of anthropogenic aerosols under three contrasting pathways for air pollution levels: SSP1-1.9, SSP2-4.5 and SSP3-7.0. We find that the broader range of future air pollution emission trajectories spanned by the SSPs compared to previous scenarios translates into total aerosol forcing estimates in 2100 relative to 1750 ranging from −0.04 in SSP1-1.9 to −0.51 W m−2 in SSP3-7.0. Compared to our 1750–2015 estimate of −0.55 W m−2, this shows that, depending on the success of air pollution policies and socioeconomic development over the coming decades, aerosol radiative forcing may weaken by nearly 95 % or remain close to the preindustrial to present-day level. In all three scenarios there is a positive forcing in 2100 relative to 2015, from 0.51 in SSP1-1.9 to 0.04 W m−2 in SSP3-7.0. Results also demonstrate significant differences across regions and scenarios, especially in South Asia and Africa. While rapid weakening of the negative aerosol forcing following effective air quality policies will unmask more of the greenhouse-gas-induced global warming, slow progress on mitigating air pollution will significantly enhance the atmospheric aerosol levels and risk to human health in these regions. In either case, the resulting impacts on regional and global climate can be significant.

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Section: Discussionmentioning

confidence: 99%

Anthropogenic aerosol forcing under the Shared Socioeconomic Pathways

2019

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“…Emission data are available for the years 1990, 1995, 2000, 2005 and 2010, and the intermediate years were calculated by linear interpolation. The national emissions were spatially disaggregated to the EDT grid using proxies for roads and shipping routes and population density, the European Pollutant Release and Transfer Register (EPRTR) and the TNO-MACC inventory for NH 3 emissions (Terrenoire et al, 2015;Bessagnet et al, 2016). Where high spatial resolution inventories are available (UK and France), the national data were used to disaggregate the emissions.…”

Section: Model Simulationsmentioning

confidence: 99%

An evaluation of European nitrogen and sulfur wet deposition and their trends estimated by six chemistry transport models for the period 1990–2010

et al. 2019

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Abstract. The wet deposition of nitrogen and sulfur in Europe for the period 1990–2010 was estimated by six atmospheric chemistry transport models (CHIMERE, CMAQ, EMEP MSC-W, LOTOS-EUROS, MATCH and MINNI) within the framework of the EURODELTA-Trends model intercomparison. The simulated wet deposition and its trends for two 11-year periods (1990–2000 and 2000–2010) were evaluated using data from observations from the EMEP European monitoring network. For annual wet deposition of oxidised nitrogen (WNOx), model bias was within 30 % of the average of the observations for most models. There was a tendency for most models to underestimate annual wet deposition of reduced nitrogen (WNHx), although the model bias was within 40 % of the average of the observations. Model bias for WNHx was inversely correlated with model bias for atmospheric concentrations of NH3+NH4+, suggesting that an underestimation of wet deposition partially contributed to an overestimation of atmospheric concentrations. Model bias was also within about 40 % of the average of the observations for the annual wet deposition of sulfur (WSOx) for most models. Decreasing trends in WNOx were observed at most sites for both 11-year periods, with larger trends, on average, for the second period. The models also estimated predominantly decreasing trends at the monitoring sites and all but one of the models estimated larger trends, on average, for the second period. Decreasing trends were also observed at most sites for WNHx, although larger trends, on average, were observed for the first period. This pattern was not reproduced by the models, which estimated smaller decreasing trends, on average, than those observed or even small increasing trends. The largest observed trends were for WSOx, with decreasing trends at more than 80 % of the sites. On average, the observed trends were larger for the first period. All models were able to reproduce this pattern, although some models underestimated the trends (by up to a factor of 4) and others overestimated them (by up to 40 %), on average. These biases in modelled trends were directly related to the tendency of the models to under- or overestimate annual wet deposition and were smaller for the relative trends (expressed as % yr−1 relative to the deposition at the start of the period). The fact that model biases were fairly constant throughout the time series makes it possible to improve the predictions of wet deposition for future scenarios by adjusting the model estimates using a bias correction calculated from past observations. An analysis of the contributions of various factors to the modelled trends suggests that the predominantly decreasing trends in wet deposition are mostly due to reductions in emissions of the precursors NOx, NH3 and SOx. However, changes in meteorology (e.g. precipitation) and other (non-linear) interactions partially offset the decreasing trends due to emission reductions during the first period but not the second. This suggests that the emission reduction measures had a relatively larger effect on wet deposition during the second period, at least for the sites with observations.

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“…Thus, in regions with decreased NO y deposition, only a portion of the increased NH 3 emissions partitioned to the aerosol phase (NH 4 + ). Once NH 3 emissions are controlled, the remaining NH 3 in the atmosphere might partition to particulate NH 4 + as the aerosol becomes more acidic (26).…”

mentioning

confidence: 99%

Ammonia emission abatement does not fully control reduced forms of nitrogen deposition

Tan

Seinfeld

2020

Proc. Natl. Acad. Sci. U.S.A.

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Human activities and population growth have increased the natural burden of reactive nitrogen (N) in the environment. Excessive N deposition on Earth’s surface leads to adverse feedbacks on ecosystems and humans. Similar to that of air pollution, emission control is recognized as an efficient means to control acid deposition. Control of nitrogen oxides (NOx = NO + NO2) emissions has led to reduction in deposition of oxidized nitrogen (NOy, the sum of all oxidized nitrogen species, except nitrous oxide [N2O]). Reduced forms of nitrogen (NHx = ammonia [NH3] + ammonium [NH4+]) deposition have, otherwise, increased, offsetting the benefit of reduction in NOy deposition. Stringent control of NH3 emissions is being considered. In this study, we assess the response of N deposition to N emission control on continental regions. We show that significant reduction of NHx deposition is unlikely to be achieved at the early stages of implementing NH3 emission abatement. Per-unit NH3 emission abatement is shown to result in only 60–80% reduction in NHx deposition, which is significantly lower than the demonstrated 80–120% benefit of controlling NOx emissions on NOy deposition. This 60–80% effectiveness of NHx deposition reduction per unit NH3 emission abatement reflects, in part, the effects of simultaneous reductions in NOx and SO2 emissions.

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Source contributions to sulfur and nitrogen deposition – an HTAP II multi-model study on hemispheric transport

Cited by 24 publications

References 77 publications

Anthropogenic aerosol forcing under the Shared Socioeconomic Pathways

Anthropogenic aerosol forcing under the Shared Socioeconomic Pathways

An evaluation of European nitrogen and sulfur wet deposition and their trends estimated by six chemistry transport models for the period 1990–2010

Ammonia emission abatement does not fully control reduced forms of nitrogen deposition

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