The Science of Aerosols

[DrTskoul]

Weak average liquid-cloud-water response to anthropogenic aerosols

Thanks, important article. Lame that they didn't pay for open access though. There's an editorial on it here: https://www.nature.com/articles/d41586-019-02287-z


Last paragraph of the conclusion:

The cancellations between increases and decreases in LWP that we have observed in liquid clouds downwind of different aerosol sources under a wide range of meteorological conditions is in stark contrast to the unidirectional aerosol-induced increases in the LWP simulated by 45 GCMs . Although in multiple GCMs an increase in the LWP enhances the Twomey effect by more than 100%45, our analysis of pollution tracks show that decreases in the LWP in fact offset 23% of the Twomey effect. The compensation between increases and decreases in the LWP in pol- lution tracks agrees with the bidirectional LWP responses found in idealized process-level model simulations15–17 and in global satellite observations of maritime clouds19,20. Now, our analysis of pollution tracks shows with unprecedented confidence that the global average LWP response to anthropogenic aerosols is weak. We expect this con- straint on the LWP response based on observations of pollution tracks to lead to improved aerosol-cloud parameterizations in GCMs and to translate into reduced uncertainty in aerosol forcing calculations and more reliable projections of future climate.

Hope they're on the right track. The number of assumptions and limitations is frightening.

Lame indeed, should have been open access...

[Reginald]

Speaking of Aerosols, but not inside clouds.

Harvard creates advisory panel to oversee solar geoengineering project
https://www.nature.com/articles/d41586-019-02331-y

Nature, July 2019

Scientists will inject particles of calcium carbonate into the atmosphere and study their effects on incoming sunlight.

Plans to test a technique that would cool the planet by blocking sunlight are one step closer to reality. Harvard University in Cambridge, Massachusetts, has created an external advisory panel to examine the potential ethical, environmental and geopolitical impacts of this geoengineering project, which has been developed by the university’s researchers.

Known as the Stratospheric Controlled Perturbation Experiment (SCoPEx), the project would involve the release of calcium carbonate particles from a steerable balloon some 20 kilometres above the southwestern United States.

Louise Bedsworth, executive director of the California Strategic Growth Council, a state agency that promotes sustainability and economic prosperity, will lead the Harvard advisory panel, the university said on 29 July. The other seven members include Earth-science researchers and specialists in environmental and climate law and policy.

[DrTskoul]

And somehow I shudder to the idea...

[TerryM]

And somehow I shudder  to the idea...

While I'm sure that Harvard has been given a thumbs up by all of the worlds various political bodies, I can't but feel the pain this will cause to the installed base of PV and Solar Thermal facilities.


Will the diurnal winds that spin so many turbines be effectively muted in the dim days ahead, and what will become of the marginal northern farms that are limited today not by temperature, but by the seasonal lack of solar radiation. At one time these farms were seen by some as the answer to failing agriculture in more southern climes.


Just because we've made some minor errors - Australian Cane Toads, The Grand Banks Fisheries and  Mono Culture Forestry spring to mind - is no indication that this time won't be, almost uniquely, successful.


Harvard itself has an unblemished reputation - ask any Slav, but even the brightest and the best have been known to err on the side of hubris.
Terry

[jai mitchell]

More on the recent "good news"
https://phys.org/news/2019-08-pollution-wont-global-spike.html

meaning pollution is unlikely to offset more than half of greenhouse gas warming.

our current top of atmosphere energy imbalance as measured by the ocean heat content increases (SEE NODC OHC) is 0.6 Watts per meter squared.  The total forcing from GHGs is about 2.4 Watts per meter squared.  This means that some large portion of the total forcing is being offset by aerosols.  if less than half we still have the 0.6 Watts per meter squared being experienced PLUS the (estimate) 1.0 Watts per meter squared from aerosols.  to reach equilibrium)  Since methane is about 20% of the current forcing and other short lived climate pollutants balancing each other out,

even this 'good news' study indicates that we still have about 1.6 Watts per meter squared of globally averaged annual forcing to be worked through the system before reaching temperature equilibrium.

This does not include the longer term climate warming feedbacks due to carbon cycle emissions as the earth warms from the 1.6 Watts per meter equilibrium warming.

[Oscillidous]

Regarding this recent paper, I don't know of many other papers exploring the idea that reduced droplet formation in clouds is what is responsible for greater cooling, it's the reflective of the particulates themselves, no? Seems to me the equivalent of saying "good news, fire doesn't cause as much frostbite as previously thought" when obviously no one was even considering the possibility.

The paper in Nature recording localized temperature change over North America 3 days after 9/11 is an example of observed warming as a result from absence of some anthropocentric aerosols, which at least to my laymen understanding seems to be a better analogue for what to expect as a result of reduced industrial output.

[Ktb]

Got to hear Dr. Jim Haywood from Exeter University and the Met Office speak today about Aerosol masking, clouds, and possible future geoengineering. He agreed to provide me his powerpoint presentation. I will try to upload it here when I obtain it.

Edit: Jim** Haywood

[TerryM]

Got to hear Dr. James Haywood from Exeter University and the Met Office speak today about Aerosol masking, clouds, and possible future geoengineering. He agreed to provide me his powerpoint presentation. I will try to upload it here when I obtain it.

Looking forward to it.
Terry

[Ktb]

Having a million difficulties trying to upload the presentation as a PDF.

I tried to take detailed notes, and stuck around for the Q&A. I may be able to answer some basic questions if anybody has any.

[blumenkraft]

Having a million difficulties trying to upload the presentation as a PDF.

The download works well. Thank you!

[Ken Feldman]

Having a million difficulties trying to upload the presentation as a PDF.

I tried to take detailed notes, and stuck around for the Q&A. I may be able to answer some basic questions if anybody has any.

Did the question about a possible spike in warming from reduced aerosols with the reduction in fossil fuel burning come up?  If so, what was the answer?

[Ktb]

Did the question about a possible spike in warming from reduced aerosols with the reduction in fossil fuel burning come up?  If so, what was the answer?

Yes, I actually asked about Hansen et al.'s 2013 paper on aerosol masking, and the effect that immediately stopping production of sulfates via oil/coal/etc. Dr. Haywood said he respected Dr. Hansen, but believed that the warming effect would not be as great or as rapid as Hansen described. Additionally, Dr. Haywood said that sulfates would be replaced with other aerosols that occur naturally, the names of which escape me.

[Ken Feldman]

Thanks.  Here's a paper that discusses variability of natural aerosols.

https://www.nature.com/articles/nature12674

Large contribution of natural aerosols to uncertainty in indirect forcing
K. S. Carslaw, L. A. Lee, C. L. Reddington, K. J. Pringle, A. Rap, P. M. Forster, G. W. Mann, D. V. Spracklen, M. T. Woodhouse, L. A. Regayre & J. R. Pierce

Nature volume 503, pages 67–71 (07 November 2013)

Abstract

The effect of anthropogenic aerosols on cloud droplet concentrations and radiative properties is the source of one of the largest uncertainties in the radiative forcing of climate over the industrial period. This uncertainty affects our ability to estimate how sensitive the climate is to greenhouse gas emissions. Here we perform a sensitivity analysis on a global model to quantify the uncertainty in cloud radiative forcing over the industrial period caused by uncertainties in aerosol emissions and processes. Our results show that 45 per cent of the variance of aerosol forcing since about 1750 arises from uncertainties in natural emissions of volcanic sulphur dioxide, marine dimethylsulphide, biogenic volatile organic carbon, biomass burning and sea spray. Only 34 per cent of the variance is associated with anthropogenic emissions. The results point to the importance of understanding pristine pre-industrial-like environments, with natural aerosols only, and suggest that improved measurements and evaluation of simulated aerosols in polluted present-day conditions will not necessarily result in commensurate reductions in the uncertainty of forcing estimates.

[jai mitchell]

Having a million difficulties trying to upload the presentation as a PDF.

I tried to take detailed notes, and stuck around for the Q&A. I may be able to answer some basic questions if anybody has any.

interesting to see what happened to arctic sea ice and the development of "the blob" in the north east pacific ocean after the 2014 eruption in iceland.

[morganism]

Dust from a giant asteroid crash caused an ancient ice age

http://www.fieldmuseum.org/about/press/dust-giant-asteroid-crash-caused-ancient-ice-age

“Our hypothesis is that the large amounts of extraterrestrial dust over a timeframe of at least two million years played an important role in changing the climate on Earth, contributing to cooling,” says Heck.

“Our results show for the first time that such dust, at times, has cooled Earth dramatically,”

[Richard Rathbone]

Having a million difficulties trying to upload the presentation as a PDF.

I tried to take detailed notes, and stuck around for the Q&A. I may be able to answer some basic questions if anybody has any.

That looks quite promising for the next generation of climate models. Its seems we finally have enough measurements of aerosols to be able to have robust arguments about what sort of modelling approach makes sense rather than crossing fingers and praying that we haven't overfitted too badly.

[Ktb]

Glad everybody enjoyed the read. The presentation was fantastic. Excellent speaker.

[jai mitchell]

Study on the aerosol impact of the 2014-2015 eruption of Bárðarbunga in Iceland


https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015GL067070

Observations of a substantial cloud-aerosol indirect effect
during the 2014–2015 Bárðarbunga-Veiðivötn
fissure eruption in Iceland
Daniel T. McCoy1 and Dennis L. Hartmann

The estimated changes in upwelling SW and cloud albedo over the first 2 months of the eruption due to anomalies in re are shown in Figure 4. Cloud albedo was estimated to increase by up to 3% in the Norwegian Sea and Greenland Sea (Figure 4b). Local increases in upwelling SW exceeded 2 W/m^2. The zonal mean upwelling SW across the 60°N–70°N latitude band was estimated to increase by 1 W /m*2, and the cloud albedo was estimated to increase by 1.5% (Figure 4