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Author Topic: The Science of Aerosols  (Read 25306 times)

jai mitchell

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Re: The Science of Aerosols
« Reply #100 on: November 21, 2016, 07:04:09 PM »
This document previously posted shows the impact of dimethyl sulifde on the atmosphere and global cooling impacts from current high-density forest regions.

http://digital.csic.es/bitstream/10261/117629/1/jgrd51980.pdf

This study shows the pollen records of previous interglacials showing what primoridal interglacials looked like from a forest biomass perspective.

http://centaur.reading.ac.uk/40025/1/cpd-11-1031-2015.pdf

This study shows that previous interglacial periods experience significantly increased temperature response to CO2 than the glacial periods.  It is my assertion that the cause of this increased response is due to much higher temperature sensitivities to cloudcover fractions at lower latitudes and more rapid shifts of cloudcover regimes to the further northern latitudes during interglacials with increases in temperature, leading to rapid and significant albedo declines, increased solar absorption and increased temperatures.

http://advances.sciencemag.org/content/2/11/e1501923.full

note that the expected ECS value for this study is closer to 5C.

Also supporting the potential for much higher interglacial ECS values is this study looking at a 2Mya global temperature reconstruction.

http://www.nature.com/nature/journal/v538/n7624/abs/nature19798.html

------------------------

In view of this information, with regard to future potential shifts in our climate.  We are running, while blindfolded, carrying scissors. 

We know that interglacial ECS is very likely at the high end (or higher) than the current IPCC range of 1.5C to 4.5C.  We also know that primordial interglacial forest dimethyl sulfide emissions AT MIDLATITUDES was much higher than our currently (relatively) deforested northern hemisphere can produce.

We know that the largest uncertainty with regard to paleoclimate ECS is the aerosol component.

---------

IF my assertion is correct and this increase is due to increased cloud-cover fraction sensitivity during interglacials.

THEN It is possibly the most critical need of the entire body of science to develop an adequate model of primordial forest dimethyl sulfide emissions in the mid latitudes during previous interglacials

SO THAT we can adequately deduce what how our current anthropogenic impacts on mid-latitude forest densities will induce on our modern cloudcover fraction as temperatures increase.

(reposted to conservative scientists and consequences thread)

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SteveMDFP

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Re: The Science of Aerosols
« Reply #101 on: November 21, 2016, 07:27:54 PM »
. . .                     
In view of this information, with regard to future potential shifts in our climate.  We are running, while blindfolded, carrying scissors. 
   

Perhaps we should say "running, while blindfolded, juggling chainsaws."

jai mitchell

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Re: The Science of Aerosols
« Reply #102 on: December 11, 2016, 02:22:53 AM »
Shmengie posted this question here:

http://forum.arctic-sea-ice.net/index.php/topic,1805.msg96253.html#msg96253

Does moisture content of atmospheric layers (troposphere/stratosphere) change or affect their height at the poles?


Funny, I was just reviewing "Observational Evidence for Aerosols Increasing Upper Tropospheric Humidity" by Riuttanen et al.  see: http://www.atmos-chem-phys.net/16/14331/2016/acp-16-14331-2016.pdf

I have been analyzing regional impacts of SO2 emission reductions on the tropopause height. A known effect, though the granual regional impacts are not well known, only a global average which is next to useless.

however, seeing the movement of tropical water vapor from the West extratropics all the way to the arctic this year makes me even more confirmed that we are seeing a great shift in the tropopause height, which produces a stronger meridional (North-South) gradient to move tropical water vapor and heat further into the arctic than ever before. (edit note: this appears to be a function of high temperature industrial process Aerosols which move more rapidly into the mid/upper troposphere as opposed to open fire (coal/biomass) aerosols which appear - during Winter especially - to stay predominantly in the lower/mid troposphere)

This paper was a bit of a Surprise to me though, The significant increase in upper tropospheric water vapor (humidity) would seem (at first glance) to cool this region.  I think the real issue here is that the expansion of the tropics is happening at the tropical edge, and the upper tropospheric (humidity) dynamics are limited there, while the boundary layer impacts of reduced AOD and cloud reflectivity levels are impacted more directly with reductions in SO2 emissions.  Not sure though.

So yeah, I would figure that, in the tropics at least, increased humidity at the upper troposphere would lead to a lowering of the tropopause height

--------------
post edit, the effect of increased rainfall in the upper troposphere of the tropics would work to effectively move latent heat from the upper altitudes to the lower altitudes, greatly increasing lower troposphere temperatures and cooling upper troposphere temperatures (in the tropics) this effect has been observed quite clearly in the MSU channel temp analyses. 

By  cooling the upper troposphere this way, the expansion of tropical waves of heat and water vapor in the meridional are reduces since the Coriolis effect is moderated by the lower tropopause heights. 

This is the primary reason that we are currently seeing greater expansions of tropical moisture into the mid latitudes since the last two weeks of 2015 (though it has been evidence since China slowed it's coal consumption growth in early 2013.
« Last Edit: January 04, 2017, 05:18:38 AM by jai mitchell »
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AbruptSLR

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Re: The Science of Aerosols
« Reply #103 on: December 14, 2016, 05:14:52 PM »
Aerosols can have a large impact on the rate of Arctic Amplification via their impact on clouds, and the linked reference discusses the use of both satellite data and computer models to reduce the uncertainties associated with this important feedback mechanism:

Zamora, L. M., Kahn, R. A., Eckhardt, S., McComiskey, A., Sawamura, P., Moore, R., and Stohl, A.: Arctic aerosol net indirect effects on thin, mid-altitude, liquid-bearing clouds, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1037, in review, 2016.

http://www.atmos-chem-phys-discuss.net/acp-2016-1037/

Abstract. Aerosol indirect effects have uncertain, but potentially large, impacts on the Arctic energy budget. Here, we have reduced uncertainty in current-day Arctic net aerosol indirect effects on the surface by better constraining various physical and microphysical characteristics of optically thin, liquid-containing clouds in clean, average and aerosol-impacted conditions using a combination of CALIPSO and CloudSat data and model output. This work provides a foundation for how future observational studies can evaluate previous model estimates of the aerosol indirect effect. Clouds over sea ice and open ocean show large differences in surface and meteorological forcing, including a near doubling of multi-layer cloud presence over the open ocean compared to sea ice. The optically thin cloud subset is susceptible to aerosols, and over sea ice we estimate a regional scale maximum net indirect effect on these clouds during polar night equivalent to ~ 0.6–0.8 W m−2 at the surface. Aerosol presence is related to reduced precipitation, cloud thickness, and radar reflectivity, and may be associated with an increased likelihood of cloud presence in the liquid phase. The observations are consistent with a thermodynamic indirect effect hypothesis and are inconsistent with a glaciation indirect effect.
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AbruptSLR

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Re: The Science of Aerosols
« Reply #104 on: January 03, 2017, 08:53:36 PM »
The linked reference provides some previously missing field information on Antarctic aerosols:

Giordano, M. R., Kalnajs, L. E., Avery, A., Goetz, J. D., Davis, S. M., and DeCarlo, P. F.: A missing source of aerosols in Antarctica – beyond long-range transport, phytoplankton, and photochemistry, Atmos. Chem. Phys., 17, 1-20, doi:10.5194/acp-17-1-2017, 2017.

http://www.atmos-chem-phys.net/17/1/2017/

Abstract. Understanding the sources and evolution of aerosols is crucial for constraining the impacts that aerosols have on a global scale. An unanswered question in atmospheric science is the source and evolution of the Antarctic aerosol population. Previous work over the continent has primarily utilized low temporal resolution aerosol filters to answer questions about the chemical composition of Antarctic aerosols. Bulk aerosol sampling has been useful in identifying seasonal cycles in the aerosol populations, especially in populations that have been attributed to Southern Ocean phytoplankton emissions. However, real-time, high-resolution chemical composition data are necessary to identify the mechanisms and exact timing of changes in the Antarctic aerosol. The recent 2ODIAC (2-Season Ozone Depletion and Interaction with Aerosols Campaign) field campaign saw the first ever deployment of a real-time, high-resolution aerosol mass spectrometer (SP-AMS – soot particle aerosol mass spectrometer – or AMS) to the continent. Data obtained from the AMS, and a suite of other aerosol, gas-phase, and meteorological instruments, are presented here. In particular, this paper focuses on the aerosol population over coastal Antarctica and the evolution of that population in austral spring. Results indicate that there exists a sulfate mode in Antarctica that is externally mixed with a mass mode vacuum aerodynamic diameter of 250 nm. Springtime increases in sulfate aerosol are observed and attributed to biogenic sources, in agreement with previous research identifying phytoplankton activity as the source of the aerosol. Furthermore, the total Antarctic aerosol population is shown to undergo three distinct phases during the winter to summer transition. The first phase is dominated by highly aged sulfate particles comprising the majority of the aerosol mass at low wind speed. The second phase, previously unidentified, is the generation of a sub-250 nm aerosol population of unknown composition. The second phase appears as a transitional phase during the extended polar sunrise. The third phase is marked by an increased importance of biogenically derived sulfate to the total aerosol population (photolysis of dimethyl sulfate and methanesulfonic acid (DMS and MSA)). The increased importance of MSA is identified both through the direct, real-time measurement of aerosol MSA and through the use of positive matrix factorization on the sulfur-containing ions in the high-resolution mass-spectral data. Given the importance of sub-250 nm particles, the aforementioned second phase suggests that early austral spring is the season where new particle formation mechanisms are likely to have the largest contribution to the aerosol population in Antarctica.
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AbruptSLR

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Re: The Science of Aerosols
« Reply #105 on: February 22, 2017, 05:20:59 PM »
The linked article is entitled: "Aerosol study to look at great unknown in climate science".  It looks like we still have a lot to learn, and if we were smart we world adopt a precautionary principal approach to climate change.

https://www.theguardian.com/world/2017/feb/22/antarctic-study-examines-impact-of-aerosols-on-climate-change

Extract: "Australian scientists are studying air pollution and cloud formation in Antarctica in an effort to understand how non-carbon aerosolised particles impact on global temperatures.

It’s the first comprehensive study of the composition and concentration of aerosols in the Antarctic sea ice area, a region that influences cloud formation and weather patterns for much of the southern hemisphere."
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jai mitchell

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Re: The Science of Aerosols
« Reply #106 on: March 04, 2017, 11:55:26 PM »
linked article shows strong model response to aerosol reductions forcing a widening of the InterTropical Convergence Zone - we are seeing this effect today with expansions of tropical water vapor pulses and atmospheric rivers moving up the pacific and atlantic from geolocation hot spots of pacific warm pool and gulf of mexico.  This will continue to grow in impact and intensity/frequency.

https://www.researchgate.net/profile/Robert_Allen12/publication/303853172_Future_Aerosol_Reductions_and_Widening_of_the_Northern_Tropical_Belt/links/576c5ae508ae9bd709960a4d.pdf

Future aerosol reductions and widening of the northern tropical belt
Robert J. Allen1 and Osinachi Ajoku1,2

1Department of Earth Sciences, University of California, Riverside, California, USA, 2Scripps Institution of Oceanography,
University of California, San Diego, La Jolla, California, USA

Abstract Observations show that the tropical belt has widened over the past few decades,
a phenomenon associated with poleward migration of subtropical dry zones and large-scale atmospheric circulation. Although part of this signal is related to natural climate variability, studies have identified an externally forced contribution primarily associated with greenhouse gases (GHGs) and stratospheric ozone loss. Here we show that the increase in aerosols over the twentieth century has led to contraction of the northern tropical belt, thereby offsetting part of the widening associated with the increase in GHGs. Over the 21st century, however, when aerosol emissions are projected to decrease, the effects of aerosols and GHGs reinforce one another, both contributing to widening of the northern tropical belt. Models that have larger aerosol forcing, by including aerosol indirect effects on cloud albedo and lifetime, yield significantly larger Northern Hemisphere (NH) tropical widening than models with direct aerosol effects only. More targeted simulations show that future reductions in aerosols can drive NH tropical widening as large as greenhouse gases, and idealized simulations show the importance of NH midlatitude aerosol forcing. Mechanistically, the 21st century reduction in aerosols peaks near 40∘N, which results in a corresponding maximum increase in surface solar radiation, NH midlatitude tropospheric warming amplification, and a poleward shift in the latitude of maximum baroclinicity, implying a corresponding shift in atmospheric circulation. If models with aerosol indirect effects better represent the real world, then future aerosol changes are likely to be an important—if not dominant—driver of NH tropical belt widening.
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Shared Humanity

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Re: The Science of Aerosols
« Reply #107 on: March 05, 2017, 03:30:14 PM »
A strong case is being made for dumping huge amounts of material into the upper atmosphere in a desperate attempt to keep the planet from burning up. This scares the hell out of me.

DrTskoul

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Re: The Science of Aerosols
« Reply #108 on: March 05, 2017, 03:57:40 PM »
A strong case is being made for dumping huge amounts of material into the upper atmosphere in a desperate attempt to keep the planet from burning up. This scares the hell out of me.

It should as we have no effing idea what the unintended consequences would be....
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jai mitchell

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Re: The Science of Aerosols
« Reply #109 on: March 21, 2017, 03:29:44 PM »
This paper shows that those models in the CMIP ensemble that include full indirect aerosol effects have about 1.5C of additional warming in the arctic over those that do not. (edit: I am estimating that the mean value for non-indirect is close to 3.0C under RCP 4.5 - so indirect Aerosol effects would be +4.5C warming - since we are already at +6C last year, obviously these models are incongruent with reality since they are looking at significantly higher forcing values than the ones we have today)   There are other aerosol effects not adequately modeled within any of these tools, including changes to the lapse rate, tropopause height and larger forcing changes in the tropics, leading to expansions of water vapor to higher latitudes, increased atmospheric rivers >80'N and a semi permanent +IPO.

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0362.1

Indirect Aerosol Effect Increases CMIP5 Models’ Projected Arctic Warming

Petr Chylek et al.

Abstract:  Phase 5 of the Coupled Model Intercomparison Project (CMIP5) climate models’ projections of the 2014–2100 Arctic warming under radiative forcing from representative concentration pathway 4.5 (RCP4.5) vary from 0.9° to 6.7°C. Climate models with or without a full indirect aerosol effect are both equally successful in reproducing the observed (1900–2014) Arctic warming and its trends. However, the 2014–2100 Arctic warming and the warming trends projected by models that include a full indirect aerosol effect (denoted here as AA models) are significantly higher (mean projected Arctic warming is about 1.5°C higher) than those projected by models without a full indirect aerosol effect (denoted here as NAA models). The suggestion is that, within models including full indirect aerosol effects, those projecting stronger future changes are not necessarily distinguishable historically because any stronger past warming may have been partially offset by stronger historical aerosol cooling. The CMIP5 models that include a full indirect aerosol effect follow an inverse radiative forcing to equilibrium climate sensitivity relationship, while models without it do not.

« Last Edit: March 22, 2017, 04:01:10 PM by jai mitchell »
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AbruptSLR

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Re: The Science of Aerosols
« Reply #110 on: April 16, 2017, 04:50:26 AM »
The linked reference discusses the use of machine learn to better evaluate the classification of primary biological aerosols:

Ruske, et. al. 2017, “Evaluation of machine learning algorithms for classification of primary biological aerosol using a new UV-LIF spectrometer”, Atmos. Meas. Tech., 10, 695–708,  doi:10.5194/amt-10-695-2017


http://www.atmos-meas-tech.net/10/695/2017/amt-10-695-2017.pdf

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AbruptSLR

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Re: The Science of Aerosols
« Reply #111 on: April 18, 2017, 12:27:14 PM »
The linked article discusses how CAM5 models open-fire aerosol impacts on direct radiative, cloud and surface-albedo effects:

Yiquan Jiang et. al. (2017), "Impacts of global open-fire aerosols on direct radiative, cloud and surface-albedo effects simulated with CAM5" Atmospheric Chemistry and Physics; 16:14805-14824; DOI: 10.5194/acp-16-14805-2016

http://www.atmos-chem-phys.net/16/14805/2016/acp-16-14805-2016.html

Abstract: "Aerosols from open-land fires could significantly perturb the global radiation balance and induce climate change. In this study, Community Atmosphere Model version 5 (CAM5) with prescribed daily fire aerosol emissions is used to investigate the spatial and seasonal characteristics of radiative effects (REs, relative to the case of no fires) of open-fire aerosols including black carbon (BC) and particulate organic matter (POM) from 2003 to 2011. The global annual mean RE from aerosol–radiation interactions (REari) of all fire aerosols is 0.16 ± 0.01 W m−2 (1σ uncertainty), mainly due to the absorption of fire BC (0.25 ± 0.01 W m−2), while fire POM induces a small effect (−0.05 and 0.04 ± 0.01 W m−2 based on two different methods). Strong positive REari is found in the Arctic and in the oceanic regions west of southern Africa and South America as a result of amplified absorption of fire BC above low-level clouds, in general agreement with satellite observations. The global annual mean RE due to aerosol–cloud interactions (REaci) of all fire aerosols is −0.70 ± 0.05 W m−2, resulting mainly from the fire POM effect (−0.59 ± 0.03 W m−2). REari (0.43 ± 0.03 W m−2) and REaci (−1.38 ± 0.23 W m−2) in the Arctic are stronger than in the tropics (0.17 ± 0.02 and −0.82 ± 0.09 W m−2 for REari and REaci), although the fire aerosol burden is higher in the tropics. The large cloud liquid water path over land areas and low solar zenith angle of the Arctic favor the strong fire aerosol REaci (up to −15 W m−2) during the Arctic summer. Significant surface cooling, precipitation reduction and increasing amounts of low-level cloud are also found in the Arctic summer as a result of the fire aerosol REaci based on the atmosphere-only simulations. The global annual mean RE due to surface-albedo changes (REsac) over land areas (0.03 ± 0.10 W m−2) is small and statistically insignificant and is mainly due to the fire BC-in-snow effect (0.02 W m−2) with the maximum albedo effect occurring in spring (0.12 W m−2) when snow starts to melt."
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AbruptSLR

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Re: The Science of Aerosols
« Reply #112 on: May 13, 2017, 07:00:37 PM »
Xie, X., Zhang, H., Liu, X., Peng, Y., and Liu, Y.: Sensitivity study of cloud parameterizations with relative dispersion in CAM5.1: impacts on aerosol indirect effects, Atmos. Chem. Phys., 17, 5877-5892, doi:10.5194/acp-17-5877-2017, 2017.

http://www.atmos-chem-phys.net/17/5877/2017/

Abstract. Aerosol-induced increase of relative dispersion of cloud droplet size distribution ε exerts a warming effect and partly offsets the cooling of aerosol indirect radiative forcing (AIF) associated with increased droplet concentration by increasing the cloud droplet effective radius (Re) and enhancing the cloud-to-rain autoconversion rate (Au) (labeled as the dispersion effect), which can help reconcile global climate models (GCMs) with the satellite observations. However, the total dispersion effects on both Re and Au are not fully considered in most GCMs, especially in different versions of the Community Atmospheric Model (CAM). In order to accurately evaluate the dispersion effect on AIF, the new complete cloud parameterizations of Re and Au explicitly accounting for ε are implemented into the CAM version 5.1 (CAM5.1), and a suite of sensitivity experiments is conducted with different representations of ε reported in the literature. It is shown that the shortwave cloud radiative forcing is much better simulated with the new cloud parameterizations as compared to the standard scheme in CAM5.1, whereas the influences on longwave cloud radiative forcing and surface precipitation are minimal. Additionally, consideration of the dispersion effect can significantly reduce the changes induced by anthropogenic aerosols in the cloud-top effective radius and the liquid water path, especially in the Northern Hemisphere. The corresponding AIF with the dispersion effect considered can also be reduced substantially by a range of 0.10 to 0.21 W m−2 at the global scale and by a much bigger margin of 0.25 to 0.39 W m−2 for the Northern Hemisphere in comparison with that of fixed relative dispersion, mainly dependent on the change of relative dispersion and droplet concentrations (Δε∕ΔNc).
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jai mitchell

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Re: The Science of Aerosols
« Reply #113 on: May 13, 2017, 07:35:31 PM »
this is good news to be sure, much more work must be done but this is good.
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Aporia_filia

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Re: The Science of Aerosols
« Reply #114 on: June 22, 2017, 01:32:11 PM »
I think this might be of relevant interest:

https://www.sciencedaily.com/releases/2017/06/170621133451.htm

"Role aerosols play in climate change unlocked by spectacular Icelandic volcanic eruption"
« Last Edit: June 22, 2017, 01:38:05 PM by Aporia_filia »

AbruptSLR

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Re: The Science of Aerosols
« Reply #115 on: June 23, 2017, 03:41:52 PM »
If tests on geoengineering are likely to occur, why not set them up so as to determine the aerosol-cloud feedback interaction so that climate model projections can be refined?

Robert Wood et. al. (22 June 2017), "Could geoengineering research help answer one of the biggest questions in climate science?", Earth's Future, DOI: 10.1002/2017EF000601

http://onlinelibrary.wiley.com/doi/10.1002/2017EF000601/abstract?utm_content=bufferc1ece&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Extract: "Anthropogenic aerosol impacts on clouds constitute the largest source of uncertainty in quantifying the radiative forcing of climate, and hinders our ability to determine Earth's climate sensitivity to greenhouse gas increases. Representation of aerosol-cloud interactions in global models is particularly challenging because these interactions occur on typically unresolved scales. Observational studies show influences of aerosol on clouds, but correlations between aerosol and clouds are insufficient to constrain aerosol forcing because of the difficulty in separating aerosol and meteorological impacts. In this commentary, we argue that this current impasse may be overcome with the development of approaches to conduct control experiments whereby aerosol particle perturbations can be introduced into patches of marine low clouds in a systematic manner. Such cloud perturbation experiments constitute a fresh approach to climate science and would provide unprecedented data to untangle the effects of aerosol particles on cloud microphysics and the resulting reflection of solar radiation by clouds. The control experiments would provide a critical test of high-resolution models that are used to develop an improved representation aerosol-cloud interactions needed to better constrain aerosol forcing in global climate models."
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AbruptSLR

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Re: The Science of Aerosols
« Reply #116 on: July 19, 2017, 05:05:26 PM »
The linked reference concludes that: "… aerosol–cloud interactions will play a key role in determining future interhemispheric shifts in climate."

Eui-Seok Chung & Brian J. Soden  (2017), "Hemispheric climate shifts driven by anthropogenic aerosol–cloud interactions", Nature Geoscience, doi:10.1038/ngeo2988

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2988.html?utm_content=buffer4bf23&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer&foxtrotcallback=true

Abstract: "The contrasting rainfall between the wet tropics and the dry subtropics largely determines the climate of the tropical zones. A southward shift of these rain belts has been observed throughout the latter half of the twentieth century, with profound societal consequences. Although such large-scale shifts in rainfall have been linked to interhemispheric temperature gradients from anthropogenic aerosols, a complete understanding of this mechanism has been hindered by the lack of explicit information on aerosol radiative effects. Here we quantify the relative contributions of radiative forcing from anthropogenic aerosols to the interhemispheric asymmetry in temperature and precipitation change for climate change simulations. We show that in model simulations the vast majority of the precipitation shift does not result from aerosols directly through their absorption and scattering of radiation, but rather indirectly through their modification of cloud radiative properties. Models with larger cloud responses to aerosol forcing are found to better reproduce the observed interhemispheric temperature changes and tropical rain belt shifts over the twentieth century, suggesting that aerosol–cloud interactions will play a key role in determining future interhemispheric shifts in climate."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson