scholarly journals Distinguishing the impacts of natural and anthropogenic aerosols on global gross primary productivity through diffuse fertilization effect

2021 ◽  
Author(s):  
Hao Zhou ◽  
Xu Yue ◽  
Yadong Lei ◽  
Chenguang Tian ◽  
Jun Zhu ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Cloud Amount ◽  
Diffuse Radiation ◽  
Gross Primary Productivity ◽  
Anthropogenic Sources ◽  
Ecosystem Productivity ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Vegetation Models ◽  
Carbon Aerosols

Abstract. Aerosols can enhance ecosystem productivity by increasing diffuse radiation. Such diffuse fertilization effects (DFEs) vary among different aerosol compositions and sky conditions. Here, we apply a suite of chemical, radiation, and vegetation models in combination with ground- and satellite-based measurements to assess the impacts of natural and anthropogenic aerosol species on gross primary productivity (GPP) through DFE during 2001–2014. Globally, aerosols increase GPP by 8.9 Pg C yr-1 at clear skies but only 0.95 Pg C yr-1 at all skies. Anthropogenic aerosols account for 41% of the total GPP enhancement though they contribute only 25% to the increment of diffuse radiation. Sulfate/nitrate aerosols from anthropogenic sources make dominant contributions of 33% (36%) to aerosol DFE at all (clear) skies, followed by the ratio of 18% (22%) by organic carbon aerosols from natural sources. In contrast to other species, black carbon aerosols decrease global GPP by 0.28 (0.12) Pg C yr-1 at all (clear) skies. Long-term simulations show that aerosol DFE is increasing 2.9% yr-1 at all skies mainly because of a downward trend in cloud amount. This study suggests that the impacts of aerosols and cloud should be considered in projecting future changes of ecosystem productivity under varied emission scenarios.

Responses of gross primary productivity to diffuse radiation at global FLUXNET sites

2021 ◽  
Vol 244 ◽  
pp. 117905 ◽  
Author(s):  
Hao Zhou ◽  
Xu Yue ◽  
Yadong Lei ◽  
Tianyi Zhang ◽  
Chenguang Tian ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Diffuse Radiation ◽  
Gross Primary Productivity

scholarly journals Climatic effects of 1950–2050 changes in US anthropogenic aerosols – Part 1: Aerosol trends and radiative forcing

2011 ◽  
Vol 11 (8) ◽  
pp. 24085-24125 ◽  
Author(s):  
E. M. Leibensperger ◽  
L. J. Mickley ◽  
D. J. Jacob ◽  
W.-T. Chen ◽  
J. H. Seinfeld ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
General Circulation ◽  
Transport Model ◽  
Circulation Model ◽  
Anthropogenic Sources ◽  
So2 Emissions ◽  
Anthropogenic Aerosols ◽  
Climatic Effects ◽  
Anthropogenic Aerosol ◽  
Direct Forcing

Abstract. We use the GEOS-Chem chemical transport model combined with the GISS general circulation model to calculate the aerosol direct and indirect (warm cloud) radiative forcings from US anthropogenic sources over the 1950–2050 period, based on historical emission inventories and future projections from the IPCC A1B scenario. The aerosol simulation is evaluated with observed spatial distributions and 1980–2010 trends of aerosol concentrations and wet deposition in the contiguous US. The radiative forcing from US anthropogenic aerosols is strongly localized over the eastern US. We find that it peaked in 1970–1990, with values over the eastern US (east of 100° W) of −2.0 W m−2 for direct forcing including contributions from sulfate (−2.0 W m−2), nitrate (−0.2 W m−2), organic carbon (−0.2 W m−2), and black carbon (+0.4 W m−2). The aerosol indirect effect is of comparable magnitude to the direct forcing. We find that the forcing declined sharply from 1990 to 2010 (by 0.8 W m−2 direct and 1.0 W m−2 indirect), mainly reflecting decreases in SO2 emissions, and project that it will continue declining post-2010 but at a much slower rate since US SO2 emissions have already declined by almost 60 % from their peak. This suggests that much of the warming effect of reducing US anthropogenic aerosol sources may have already been realized by 2010, however some additional warming is expected through 2020. The small positive radiative forcing from US BC emissions (+0.3 W m−2 over the eastern US in 2010) suggests that an emission control strategy focused on BC would have only limited climate benefit.

scholarly journals Aerosol radiative effects with MACv2

2019 ◽  
Author(s):  
Stefan Kinne
Keyword(s):  
Anthropogenic Sources ◽  
Transfer Model ◽  
Strong Impact ◽  
Radiative Effects ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Aerosol Forcing ◽  
Aerosol Radiative Effects ◽  
The Impact ◽  
Aerosol Radiative

Abstract. onthly global maps for aerosol properties of the MACv2 climatology are applied in an off-line radiative transfer model to determine aerosol radiative effects. For details beyond global averages in most cases global maps are presented to visualize regional and seasonal details. Aside from the direct radiative (aerosol presence) effect, including those for aerosol components as extracted from MACv2 aerosol optics, also the major aerosol indirect radiative effect is covered. Hereby, the impact of smaller drops in water clouds due to added anthropogenic aerosol was simulated by applying a satellite retrieval based fit from locally associations between aerosol and drop concentrations over oceans. Present-day anthropogenic aerosols of MACv2 – on a global average basis – reduce the radiative net-fluxes at the top of the atmosphere (TOA) by −1.0 W/m2 and at the surface by −2.1 W/m2. Direct cooling contributions are only about half of indirect contributions (−.35 vs −.65) at TOA, but about twice at the surface (−1.45 vs −.65), as solar absorption of the direct effect warms the atmosphere by +1.1 W/m2. Natural aerosols are on average less absorbing (for a relatively larger solar TOA cooling) and larger in size (now contributing with IR greenhouse warming). Thus, average TOA direct forcing efficiencies for total and anthropogenic aerosol happen to be similar: −11 W/m2/AOD at all-sky and −24 W/m2/AOD at clear-sky conditions. The present-day direct impact by all soot (BC) is globally averaged +0.55W/m2 and at least half of it should be attributed to anthropogenic sources. Hereby any accuracy of anthropogenic impacts, not just for soot, suffers from the limited access to a pre-industrial reference. Anthropogenic uncertainty has a particular strong impact on aerosol indirect effects, which dominate the (TOA) forcing. Accounting for uncertainties in the anthropogenic definition, present-day aerosol forcing is estimated to stay within the −0.7 to −1.6 W/m2 range, with a best estimate at −1 W/m2. Calculations with model predicted temporal changes to anthropogenic AOD indicate that qualitatively the anthropogenic aerosol forcing has not changed much over the last decades and is not likely to increase over the next decades, despite strong regional shifts. These regional shifts explain most solar insolation (brightening or dimming) trends that have been observed by ground-based radiation data.

Large contributions of diffuse radiation to global gross primary productivity during 1981‐2015

2021 ◽  
Author(s):  
Hao Zhou ◽  
Xu Yue ◽  
Yadong Lei ◽  
Chenguang Tian ◽  
Yimian Ma ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Diffuse Radiation ◽  
Gross Primary Productivity

scholarly journals Climatic effects of 1950–2050 changes in US anthropogenic aerosols – Part 1: Aerosol trends and radiative forcing

2012 ◽  
Vol 12 (7) ◽  
pp. 3333-3348 ◽  
Author(s):  
E. M. Leibensperger ◽  
L. J. Mickley ◽  
D. J. Jacob ◽  
W.-T. Chen ◽  
J. H. Seinfeld ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
General Circulation ◽  
Circulation Model ◽  
Radiative Properties ◽  
Anthropogenic Sources ◽  
So2 Emissions ◽  
Anthropogenic Aerosols ◽  
Climatic Effects ◽  
Anthropogenic Aerosol ◽  
Direct Forcing

Abstract. We calculate decadal aerosol direct and indirect (warm cloud) radiative forcings from US anthropogenic sources over the 1950–2050 period. Past and future aerosol distributions are constructed using GEOS-Chem and historical emission inventories and future projections from the IPCC A1B scenario. Aerosol simulations are evaluated with observed spatial distributions and 1980–2010 trends of aerosol concentrations and wet deposition in the contiguous US. Direct and indirect radiative forcing is calculated using the GISS general circulation model and monthly mean aerosol distributions from GEOS-Chem. The radiative forcing from US anthropogenic aerosols is strongly localized over the eastern US. We find that its magnitude peaked in 1970–1990, with values over the eastern US (east of 100° W) of −2.0 W m−2 for direct forcing including contributions from sulfate (−2.0 W m−2), nitrate (−0.2 W m−2), organic carbon (−0.2 W m−2), and black carbon (+0.4 W m−2). The uncertainties in radiative forcing due to aerosol radiative properties are estimated to be about 50%. The aerosol indirect effect is estimated to be of comparable magnitude to the direct forcing. We find that the magnitude of the forcing declined sharply from 1990 to 2010 (by 0.8 W m−2 direct and 1.0 W m−2 indirect), mainly reflecting decreases in SO2 emissions, and project that it will continue declining post-2010 but at a much slower rate since US SO2 emissions have already declined by almost 60% from their peak. This suggests that much of the warming effect of reducing US anthropogenic aerosol sources has already been realized. The small positive radiative forcing from US BC emissions (+0.3 W m−2 over the eastern US in 2010; 5% of the global forcing from anthropogenic BC emissions worldwide) suggests that a US emission control strategy focused on BC would have only limited climate benefit.

scholarly journals Stratospheric sulfate geoengineering enhances terrestrial gross primary productivity

2015 ◽  
Vol 15 (18) ◽  
pp. 25627-25645 ◽  
Author(s):  
L. Xia ◽  
A. Robock ◽  
S. Tilmes ◽  
R. R. Neely
Keyword(s):  
Primary Productivity ◽  
Climate Model ◽  
Carbon Sink ◽  
Diffuse Radiation ◽  
Atmospheric Model ◽  
Gross Primary Productivity ◽  
Terrestrial Carbon ◽  
Beneficial Impact ◽  
Climate Model Simulations ◽  
Terrestrial Carbon Sink

Abstract. Stratospheric sulfate geoengineering could impact the terrestrial carbon cycle by enhancing the carbon sink. With an 8 Tg yr−1 injection of SO2 to balance a Representative Concentration Pathway 6.0 (RCP6.0) scenario, we conducted climate model simulations with the Community Earth System Model, with the Community Atmospheric Model 4 fully coupled to tropospheric and stratospheric chemistry (CAM4-chem). During the geoengineering period, as compared to RCP6.0, land-averaged downward visible diffuse radiation increased 3.2 W m−2 (11 %). The enhanced diffuse radiation combined with the cooling increased plant photosynthesis by 2.4 %, which could contribute to an additional 3.8 ± 1.1 Gt C yr−1 global gross primary productivity without nutrient limitation. This increase could potentially increase the land carbon sink. Suppressed plant and soil respiration due to the cooling would reduce natural land carbon emission and therefore further enhance the terrestrial carbon sink during the geoengineering period. This beneficial impact of stratospheric sulfate geoengineering would need to be balanced by a large number of potential risks in any future decisions about implementation of geoengineering.

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