scholarly journals Review of Implementing a sectional scheme for early aerosol growth from new particle formation in the Norwegian Earth System Model v2: comparison to observations and climate impacts

2020 ◽  
Author(s):  
Anonymous
Keyword(s):  
Particle Formation ◽  
Climate Impacts ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
New Particle Formation

Reduced effective radiative forcing from cloud-aerosol interactions with improved modelling of early aerosol growth in an Earth System Model

2021 ◽  
Author(s):  
Sara Marie Blichner ◽  
Moa Kristina Sporre ◽  
Terje Koren Berntsen
Keyword(s):  
Radiative Forcing ◽  
Particle Growth ◽  
Particle Formation ◽  
Climate Impacts ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
New Particle Formation ◽  
Secondary Aerosol ◽  
Effective Radiative Forcing

<p>Cloud-aerosol interactions are responsible for much of the uncertainty in forcing estimates from pre-industrial times and thus also climate sensitivity and future projections. Maybe the most important factor in this is our lack of knowledge about pre-industrial aerosols, their sources and their ability to act as cloud condensation nuclei (CCN). The number of CCN is highly dependent on secondary aerosol formation and in particular how much of this secondary aerosol mass that goes to new particle formation (NPF) and early particle growth, versus growing already large particles even larger. <br>Earth system models which seek to model this, face a challenge because we need to represent processes at a very fine scale (nanometers) to a sufficient accuracy, while simultaneously keeping computational costs low. A common approach is to use log-normal modes to represent the sizedistribution, while more computationally expensive sectional schemes are considered closer to first principles. </p><p>In this study, we investigate the effect of a newly developed scheme for early particle growth on the effective radiative forcing from cloud-aerosol interactions (ERF<sub>aci</sub>)  in the Norwegian Earth System Model v2 (NorESMv2). The new scheme, referred to as OsloAeroSec, presented in  Blichner et al. (2020), combines a sectional scheme for the growth of the smallest particles (5 - 39.6 nm), with the original semi-modal aerosol scheme which would simply parameterize the growth up to the smallest mode with Lehtinen et al. (2007). This was shown to to improve the representation of CCN relevant particle concentrations, when compared to measurement data.  </p><p>We find that ERF<sub>aci</sub> is weakened by approximately 10 % with the new scheme (from -1.29  to -1.16 Wm<sup>-2</sup>). The weakening originates from OsloAeroSec (the new scheme) reducing particle formation in regions with high aerosol concentrations while increasing it in very pristine regions. We find, perhaps surprisingly, that an important factor for the overall forcing, is that  NPF inhibits aerosol activation into cloud droplets in high-aerosol-concentration regions, while the opposite is true in pristine regions. <br>This is because the NPF particles act as a condensation sink, and if they cannot activate directly themselves, they may reduce the growth of the larger particles which would otherwise activate. <br>Furthermore, we find that the increase in particle hygroscopicity with present day emissions of sulphate pre-cursors, decreases the size of the activated particles, and thus makes NPF particles more relevant for cloud droplet activation. </p><p><strong>References: </strong></p><p>Lehtinen, Kari E. J., Miikka Dal Maso, Markku Kulmala, and Veli-Matti Kerminen. “Estimating Nucleation Rates from Apparent Particle Formation Rates and Vice Versa: Revised Formulation of the Kerminen–Kulmala Equation.” Journal of Aerosol Science (2007): https://doi.org/10.1016/j.jaerosci.2007.06.009.</p><p>Blichner, Sara M., Moa K. Sporre, Risto Makkonen, and Terje K. Berntsen. “Implementing a sectional scheme for early aerosol growth from new particle formation in the Norwegian Earth System Model v2: comparison to observations and climate impacts.” Geoscientific Model Development Discussions (2020): https://doi.org/10.5194/gmd-2020-357</p>

scholarly journals Implementing a sectional scheme for early aerosol growth from new particle formation in the Norwegian Earth System Model v2: comparison to observations and climate impacts

2020 ◽  
Author(s):  
Sara M. Blichner ◽  
Moa K. Sporre ◽  
Risto Makkonen ◽  
Terje K. Berntsen
Keyword(s):  
Size Distribution ◽  
Large Scale ◽  
Particle Formation ◽  
Early Growth ◽  
Number Concentration ◽  
Climate Impacts ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
New Particle Formation

Abstract. Aerosol-cloud interactions contribute with a large portion of the spread in estimates of climate forcing, climate sensitivity and future projections. An important part of this uncertainty is how much new particle formation (NPF) contributes to cloud condensation nuclei (CCN), and furthermore, how this changes with changes in anthropogenic emissions. Incorporating NPF and early growth in Earth System Models (ESMs) is, however, challenging both due to uncertain parameters (e.g. participating vapours), structural challenges (numerical description of growth from ∼1 to ∼100 nm), and due to large scale of ESM grid compared to NPF scale.A common approach in ESMs is to represent the particle size distribution by a certain number of log-normal modes. Sectional schemes on the other hand, where the size distribution is represented by bins, are considered closer to first principles because they do not make an a priori assumption about the size distribution. In order to improve the representation of early growth, we have implemented a sectional scheme for the smallest particles (5–39.6 nm diameter) in the Norwegian Earth System Model (NorESM), feeding particles into the original aerosol scheme. This is, to our knowledge, the first time such an approach has been tried. We find that including the sectional scheme for early growth improves the aerosol number concentration in the model when comparing against observations, particularly in the 50–100 nm diameter range. Furthermore, we find that the model with the sectional scheme produces much less particles than the original scheme in polluted regions, while it produces more in remote regions and the free troposphere, indicating a potential impact on the estimated aerosol forcing. Finally, we analyse the effect on cloud-aerosol interactions and find that the effect of changes in NPF efficiency on clouds is highly heterogeneous in space. While in remote regions, more efficient NPF leads to higher cloud droplet number concentration (CDNC), in polluted regions the opposite is in fact the case.

scholarly journals Implementing a sectional scheme for early aerosol growth from new particle formation in the Norwegian Earth System Model v2: comparison to observations and climate impacts

2021 ◽  
Vol 14 (6) ◽  
pp. 3335-3359
Author(s):  
Sara M. Blichner ◽  
Moa K. Sporre ◽  
Risto Makkonen ◽  
Terje K. Berntsen
Keyword(s):  
Size Distribution ◽  
Large Scale ◽  
Particle Formation ◽  
Early Growth ◽  
Number Concentration ◽  
Climate Impacts ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
New Particle Formation

Abstract. Aerosol–cloud interactions contribute to a large portion of the spread in estimates of climate forcing, climate sensitivity and future projections. An important part of this uncertainty is how much new particle formation (NPF) contributes to cloud condensation nuclei (CCN) and, furthermore, how this changes with changes in anthropogenic emissions. Incorporating NPF and early growth in Earth system models (ESMs) is, however, challenging due to uncertain parameters (e.g. participating vapours), structural issues (numerical description of growth from ∼1 to ∼100 nm) and the large scale of an ESM grid compared to the NPF scale. A common approach in ESMs is to represent the particle size distribution by a certain number of log-normal modes. Sectional schemes, on the other hand, in which the size distribution is represented by bins, are considered closer to first principles because they do not make an a priori assumption about the size distribution. In order to improve the representation of early growth, we have implemented a sectional scheme for the smallest particles (5–39.6 nm diameter) in the Norwegian Earth System Model (NorESM), feeding particles into the original aerosol scheme. This is, to our knowledge, the first time such an approach has been tried. We find that including the sectional scheme for early growth improves the aerosol number concentration in the model when comparing against observations, particularly in the 50–100 nm diameter range. Furthermore, we find that the model with the sectional scheme produces much fewer particles than the original scheme in polluted regions, while it produces more in remote regions and the free troposphere, indicating a potential impact on the estimated aerosol forcing. Finally, we analyse the effect on cloud–aerosol interactions and find that the effect of changes in NPF efficiency on clouds is highly heterogeneous in space. While in remote regions, more efficient NPF leads to higher cloud droplet number concentration (CDNC), in polluted regions the opposite is in fact the case.

scholarly journals Oceanic and atmospheric methane cycling in the cGENIE Earth system model

2020 ◽  
Author(s):  
Christopher T. Reinhard ◽  
Stephanie Olson ◽  
Sandra Kirtland Turner ◽  
Cecily Pälike ◽  
Yoshiki Kanzaki ◽  
...  
Keyword(s):  
Climate Impacts ◽  
Earth System Model ◽  
System Model ◽  
Comprehensive Treatment ◽  
Model Parameters ◽  
Anaerobic Oxidation Of Methane ◽  
Earth System ◽  
Atmospheric Methane ◽  
Model Framework ◽  
Oxidation Of Methane

Abstract. The methane (CH4) cycle is a key component of the Earth system that links planetary climate, biological metabolism, and the global biogeochemical cycles of carbon, oxygen, sulfur, and hydrogen. However, currently lacking is a numerical model capable of simulating a diversity of environments in the ocean where CH4 can be produced and destroyed, and with the flexibility to be able to explore not only relatively recent perturbations to Earth’s CH4 cycle but also to probe CH4 cycling and associated climate impacts under the very low-O2 conditions characteristic of most of Earth history and likely widespread on other Earth-like planets. Here, we present a refinement and expansion of the ocean-atmosphere CH4 cycle in the intermediate-complexity Earth system model cGENIE, including parameterized atmospheric O2-O3-CH4 photochemistry and schemes for microbial methanogenesis, aerobic methanotrophy, and anaerobic oxidation of methane (AOM). We describe the model framework, compare model parameterizations against modern observations, and illustrate the flexibility of the model through a series of example simulations. Though we make no attempt to rigorously tune default model parameters, we find that simulated atmospheric CH4 levels and marine dissolved CH4 distributions are generally in good agreement with empirical constraints for the modern and recent Earth. Finally, we illustrate the model’s utility in understanding the time-dependent behavior of the CH4 cycle resulting from transient carbon injection into the atmosphere, and present model ensembles that examine the effects of atmospheric pO2, oceanic dissolved SO42− and the thermodynamics of microbial metabolism on steady-state atmospheric CH4 abundance. Future model developments will address the sources and sinks of CH4 associated with the terrestrial biosphere and marine CH4 gas hydrates, both of which will be essential for comprehensive treatment of Earth’s CH4 cycle during geologically recent time periods.

scholarly journals Present and future aerosol impacts on Arctic climate change in the GISS-E2.1 Earth system model

2021 ◽  
Vol 21 (13) ◽  
pp. 10413-10438
Author(s):  
Ulas Im ◽  
Kostas Tsigaridis ◽  
Gregory Faluvegi ◽  
Peter L. Langen ◽  
Joshua P. French ◽  
...  
Keyword(s):  
Climate Change ◽  
Climate Impacts ◽  
Earth System Model ◽  
System Model ◽  
The Arctic ◽  
Earth System ◽  
Anthropogenic Aerosols ◽  
Emission Reductions ◽  
Air Temperatures ◽  
Arctic Surface

Abstract. The Arctic is warming 2 to 3 times faster than the global average, partly due to changes in short-lived climate forcers (SLCFs) including aerosols. In order to study the effects of atmospheric aerosols in this warming, recent past (1990–2014) and future (2015–2050) simulations have been carried out using the GISS-E2.1 Earth system model to study the aerosol burdens and their radiative and climate impacts over the Arctic (>60∘ N), using anthropogenic emissions from the Eclipse V6b and the Coupled Model Intercomparison Project Phase 6 (CMIP6) databases, while global annual mean greenhouse gas concentrations were prescribed and kept fixed in all simulations. Results showed that the simulations have underestimated observed surface aerosol levels, in particular black carbon (BC) and sulfate (SO42-), by more than 50 %, with the smallest biases calculated for the atmosphere-only simulations, where winds are nudged to reanalysis data. CMIP6 simulations performed slightly better in reproducing the observed surface aerosol concentrations and climate parameters, compared to the Eclipse simulations. In addition, simulations where atmosphere and ocean are fully coupled had slightly smaller biases in aerosol levels compared to atmosphere-only simulations without nudging. Arctic BC, organic aerosol (OA), and SO42- burdens decrease significantly in all simulations by 10 %–60 % following the reductions of 7 %–78 % in emission projections, with the Eclipse ensemble showing larger reductions in Arctic aerosol burdens compared to the CMIP6 ensemble. For the 2030–2050 period, the Eclipse ensemble simulated a radiative forcing due to aerosol–radiation interactions (RFARI) of -0.39±0.01 W m−2, which is −0.08 W m−2 larger than the 1990–2010 mean forcing (−0.32 W m−2), of which -0.24±0.01 W m−2 was attributed to the anthropogenic aerosols. The CMIP6 ensemble simulated a RFARI of −0.35 to −0.40 W m−2 for the same period, which is −0.01 to −0.06 W m−2 larger than the 1990–2010 mean forcing of −0.35 W m−2. The scenarios with little to no mitigation (worst-case scenarios) led to very small changes in the RFARI, while scenarios with medium to large emission mitigations led to increases in the negative RFARI, mainly due to the decrease in the positive BC forcing and the decrease in the negative SO42- forcing. The anthropogenic aerosols accounted for −0.24 to −0.26 W m−2 of the net RFARI in 2030–2050 period, in Eclipse and CMIP6 ensembles, respectively. Finally, all simulations showed an increase in the Arctic surface air temperatures throughout the simulation period. By 2050, surface air temperatures are projected to increase by 2.4 to 2.6 ∘C in the Eclipse ensemble and 1.9 to 2.6 ∘C in the CMIP6 ensemble, compared to the 1990–2010 mean. Overall, results show that even the scenarios with largest emission reductions leads to similar impact on the future Arctic surface air temperatures and sea-ice extent compared to scenarios with smaller emission reductions, implying reductions of greenhouse emissions are still necessary to mitigate climate change.

scholarly journals Greenhouse Gas Policy Influences Climate via Direct Effects of Land-Use Change

2013 ◽  
Vol 26 (11) ◽  
pp. 3657-3670 ◽  
Author(s):  
Andrew D. Jones ◽  
William D. Collins ◽  
James Edmonds ◽  
Margaret S. Torn ◽  
Anthony Janetos ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Land Use Change ◽  
Radiative Forcing ◽  
Climate Impacts ◽  
Earth System Model ◽  
Assessment Model ◽  
System Model ◽  
Earth System ◽  
Alternative Scenario

Abstract Proposed climate mitigation measures do not account for direct biophysical climate impacts of land-use change (LUC), nor do the stabilization targets modeled for phase 5 of the Coupled Model Intercomparison Project (CMIP5) representative concentration pathways (RCPs). To examine the significance of such effects on global and regional patterns of climate change, a baseline and an alternative scenario of future anthropogenic activity are simulated within the Integrated Earth System Model, which couples the Global Change Assessment Model, Global Land-Use Model, and Community Earth System Model. The alternative scenario has high biofuel utilization and approximately 50% less global forest cover than the baseline, standard RCP4.5 scenario. Both scenarios stabilize radiative forcing from atmospheric constituents at 4.5 W m−2 by 2100. Thus, differences between their climate predictions quantify the biophysical effects of LUC. Offline radiative transfer and land model simulations are also utilized to identify forcing and feedback mechanisms driving the coupled response. Boreal deforestation is found to strongly influence climate because of increased albedo coupled with a regional-scale water vapor feedback. Globally, the alternative scenario yields a twenty-first-century warming trend that is 0.5°C cooler than baseline, driven by a 1 W m−2 mean decrease in radiative forcing that is distributed unevenly around the globe. Some regions are cooler in the alternative scenario than in 2005. These results demonstrate that neither climate change nor actual radiative forcing is uniquely related to atmospheric forcing targets such as those found in the RCPs but rather depend on particulars of the socioeconomic pathways followed to meet each target.

scholarly journals Present and future aerosol impacts on Arctic climate change in the GISS-E2.1 Earth system model

2021 ◽  
Author(s):  
Ulas Im ◽  
Kostas Tsigaridis ◽  
Gregory Faluvegi ◽  
Peter L. Langen ◽  
Joshua P. French ◽  
...  
Keyword(s):  
Sea Ice ◽  
Climate Impacts ◽  
Earth System Model ◽  
System Model ◽  
The Arctic ◽  
Earth System ◽  
Anthropogenic Aerosols ◽  
Emission Reductions ◽  
Air Temperatures ◽  
Arctic Surface

Abstract. The Arctic is warming two to three times faster than the global average, partly due to changes in short-lived climate forcers (SLCFs) including aerosols. In order to study the effects of atmospheric aerosols in this warming, recent past (1990–2014) and future (2015–2050) simulations have been carried out using the GISS-E2.1 Earth system model to study the aerosol burdens and their radiative and climate impacts over the Arctic (>60° N), using anthropogenic emissions from the Eclipse V6b and the Coupled Model Intercomparison Project Phase 6 (CMIP6) databases. Surface aerosol levels, in particular black carbon (BC) and sulfate (SO42−), have been significantly underestimated by more than 50 %, with the smallest biases calculated for the nudged atmosphere-only simulations. CMIP6 simulations performed slightly better in simulating both surface concentrations of aerosols and climate parameters, compared to the Eclipse simulations. In addition, fully-coupled simulations had slightly smaller biases in aerosol levels compared to atmosphere only simulations without nudging. Arctic BC, organic carbon (OC) and SO42− burdens decrease significantly in all simulations following the emission projections, with the CMIP6 ensemble showing larger reductions in Arctic aerosol burdens compared to the Eclipse ensemble. For the 2030–2050 period, both the Eclipse Current Legislation (CLE) and the Maximum Feasible Reduction (MFR) ensembles simulated an aerosol top of the atmosphere (TOA) forcing of −0.39±0.01 W m−2, of which −0.24±0.01 W m−2 were attributed to the anthropogenic aerosols. The CMIP6 SSP3-7.0 scenario simulated a TOA aerosol forcing of −0.35 W m−2 for the same period, while SSP1-2.6 and SSP2-4.5 scenarios simulated a slightly more negative TOA forcing (−0.40 W m−2), of which the anthropogenic aerosols accounted for −0.26 W m−2. Finally, all simulations showed an increase in the Arctic surface air temperatures both throughout the simulation period. In 2050, surface air temperatures are projected to increase by 2.4 °C to 2.6 °C in the Eclipse ensemble and 1.9 °C to 2.6 °C in the CMIP6 ensemble, compared to the 1990–2010 mean. Overall, results show that even the scenarios with largest emission reductions lead to similar impact on the future Arctic surface air temperatures compared to scenarios with smaller emission reductions, while scenarios no or little mitigation leads to much larger sea-ice loss, implying that even though the magnitude of aerosol reductions lead to similar responses in surface air temperatures, high mitigation of aerosols are still necessary to limit sea-ice loss.

scholarly journals Revisiting the climate impacts of cool roofs around the globe using an Earth system model

2016 ◽  
Vol 11 (8) ◽  
pp. 084014 ◽  
Author(s):  
Jiachen Zhang ◽  
Kai Zhang ◽  
Junfeng Liu ◽  
George Ban-Weiss
Keyword(s):  
Climate Impacts ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Cool Roofs
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