Hi John‹Regarding your query about changing power plant emissions, think back to the situation in the mid-20th century when all the black soot and ash was also coming out of power plants. Modern coal-fired power plants are tuned so as to not make much soot (it is wasted energy) and filter out most of the rest. For SO2, many are already taking much of that out as well. Your question might better be could one have power plants not remove the SO2. Doable, but would likely have significant health and acid precipitation consequences.
It would make much more sense, were one to want to augment the sulfate amount in the free troposphere to enhance the cooling effect to take the S that has been and is being scrubbed out of power plants and then set up release locations in the remote, low latitude, mid Pacific and Indian oceans, oxidize the S, loft it to above the boundary layer to increase its lifetime, and so generally increase the tropospheric sulfate loading while also benefitting from some amount of cloud brightening effect‹doing so over the low albedo ocean areas where there are very few people and lofting above the boundary layer would be important. So, one would benefit from large area, sharp albedo contrast, sun well up in the sky, etc., so augmentation of loading might be low enough to avoid serious consequences when a fraction of the emitted sulfate eventually got carried to populated areas and areas sensitive to acid deposition (acid deposition is especially a problem when get buildup on snow over winter and then rapid melt‹and would avoid that). Now, some would say the health consequences are not worth the moderations of climate change, and others would say the SO2 is a proxy for health effects of other substances normally coming from power plants, so not much need to worry. What would be needed would be a major comparative assessment of benefits of slowing climate change, unintended and unavoidable side effects, and lots more. An additional question would be whether there are alternatives that might be better (less costly, fewer unintended consequences, more workable governance issues, more easily tested, and so on), including possibly: (a) lofting sea salt for brightening marine stratus clouds (so in the boundary layer, where lifetime would be less than in free troposphere‹would require more energy, but reduced likelihood of health effects, etc.); (b) lofting the sulfur into the stratosphere as is being most looked at; (c) combining various approaches, either on global basis or in polar regions; (d) etc. In any case, I don¹t think that increasing release of SO2 from power plants is close to the best idea. What we really need to do is have power plants be as clean as possible to limit close-in health effects (and certainly not add to overall CO2 emissions). Beyond that, a lot to look at, especially when the aim would be to offset a limited fraction of a CO2 doubling, starting small and gradually increasing, rather than trying to suddenly reverse a full CO2 doubling. Mike ******* On 9/14/12 3:19 PM, "John Nissen" <[email protected]> wrote: > Hi Mike, > > Could there be a method of selective filtering of coal-fired power stations, > such that the cooling aerosol (or SO2 precursor) is allowed into the > troposphere while the black carbon is removed? > > Cheers, > > John > > --- > > On Tue, Sep 11, 2012 at 7:15 PM, Mike MacCracken <[email protected]> wrote: >> Hi Stephen‹I would think that Chinese sulfate (like tropospheric sulfate from >> virtually anywhere) would contribute to cloud and free air brightening, so a >> cooling influence (especially when that sulfate is above the dark Pacific >> Ocean). Now, in that coal plants put out more than pure SO2, there might well >> be some components (such as black carbon) that would exert a strong warming >> influence, especially if they are carried far enough to deposit on snow >> and/or ice during the sunny half of the year in the Arctic. For net effect, >> there is need for much more analysis than I have seen. >> >> On limiting heat reaching the Arctic Ocean, there have been suggestions to >> even build a dam across the Bering Strait‹as long ago as the mid-20th century >> (though I think then it was with the intent to warm the Arctic). My guess on >> the kelp idea is that the sunny part of the year is not long enough for that >> approach to be all that practical (not only is the sunny part of the year >> short, but the sun angle is often not helpful). And sea ice is typically only >> a few meters thickness, so no where near 30 m. >> >> Mike >> >> >> >> On 9/11/12 12:48 PM, "Stephen Salter" <[email protected] >> <http://[email protected]> > wrote: >> >>> >>> Mike >>> >>> Do you think that the higher levels of SO2 from Chinese coal burning could >>> account for some of the increase in Arctic temperatures? >>> >>> Another thought for your list might be to increase the drag of water >>> flowing in through the Bering Strait. In summer kelp grows at an amazing >>> rate but not below about 30 metre water depth because of the shortage of >>> light. The net flow is 800,000 m3 a second and it will be warmer than polar >>> water so a small velocity reduction makes a big difference. What if we put >>> strong ropes moored at 30 metres to give them kelp a foot hold? If kelp >>> gets scraped off by floating ice it will can grow again. Does ice reach >>> down to 30 metres? >>> >>> Stephen >>> >>> On 11/09/2012 18:05, Mike MacCracken wrote: >>> >>> >>>> Re: [geo] Coupled Model Intercomparison Project 5 (CMIP5) simulations of >>>> climate following volcanic eruptions In my view, this is just why >>>> geoengineering efforts to cool the Arctic should consider as approaches: >>>> (a) spring-summer only injection of the appropriate sulfur compound >>>> (whatever will lead to sulfates) into the LOWER stratosphere or free >>>> troposphere, (b) cloud brightening in region or over currents carrying heat >>>> into the region, (c) approaches to brighten the surface albedo (e.g., >>>> microbubbles) in or near the region, and, perhaps, (d) approaches to reduce >>>> cirrus that are reducing IR loss. >>>> >>>> >>>> Parallel to these efforts, we should also be working to limit emissions of >>>> substances that amplify Arctic warming above and beyond the amplification >>>> that happens due to natural processes, so black carbon from sources in and >>>> near the region, etc. >>>> >>>> Mike >>>> >>>> >>>> >>>> >>>> On 9/11/12 5:03 AM, "Stephen Salter" <[email protected] >>>> <http://[email protected]> > wrote: >>>> >>>> >>>>> >>>>> Hi All >>>>> >>>>> Six out of the eight models in the Driscoll et al paper show near >>>>> surface-warming in Arctic winters following volcanic eruptions. This is in >>>>> line with figure 2a the Jones Hayward Boucher Robock 2010 paper in >>>>> Atmospheric Chemistry and Physics. The obvious mechanisms are blanketing >>>>> of outgoing radiation and side-scatter of high solar rays that might have >>>>> missed the polar regions. Given the concerns about the loss of Arctic >>>>> ice and increased methane release we will have to be very careful not to >>>>> let any geo-engineering sulphur that we inject at low latitudes reach the >>>>> Arctic in winter. >>>>> >>>>> Stephen >>>>> >>>>> On 10/09/2012 16:52, Simon Driscoll wrote: >>>>> >>>>> >>>>> >>>>>> >>>>>> >>>>>> Dear all, >>>>>> >>>>>> the published version (no longer PiP) is now available here: >>>>>> >>>>>> http://www.agu.org/pubs/crossref/2012/2012JD017607.shtml >>>>>> >>>>>> Warm regards, >>>>>> >>>>>> Simon >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> ________________________________________________ >>>>>> >>>>>> Simon Driscoll >>>>>> Atmospheric, Oceanic and Planetary Physics >>>>>> Department of Physics >>>>>> University of Oxford >>>>>> >>>>>> Office: 01865 272930 >>>>>> Mobile: 07935314940 >>>>>> >>>>>> http://www2.physics.ox.ac.uk/contacts/people/driscoll >>>>>> >>>>>> http://www.geoengineering.ox.ac.uk/people/who-are-we/simon-driscoll/ >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> From: [email protected] >>>>>> <http://[email protected]> >>>>>> [[email protected] <http://[email protected]> >>>>>> ] on behalf of Andrew Lockley [[email protected] >>>>>> <http://[email protected]> ] >>>>>> Sent: 14 August 2012 02:06 >>>>>> To: geoengineering >>>>>> Subject: [geo] Coupled Model Intercomparison Project 5 (CMIP5) >>>>>> simulations of climate following volcanic eruptions >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> http://www.agu.org/pubs/crossref/pip/2012JD017607.shtml >>>>>> >>>>>> >>>>>> The ability of the climate models submitted to the Coupled Model >>>>>> Intercomparison Project 5 (CMIP5) database to simulate the Northern >>>>>> Hemisphere winter climate following a large tropical volcanic eruption is >>>>>> assessed. When sulfate aerosols are produced by volcanic injections into >>>>>> the tropical stratosphere and spread by the stratospheric circulation, it >>>>>> not only causes globally averaged tropospheric cooling but also a >>>>>> localized heating in the lower stratosphere, which can cause major >>>>>> dynamical feedbacks. Observations show a lower stratospheric and surface >>>>>> response during the following one or two Northern Hemisphere (NH) >>>>>> winters, that resembles the positive phase of the North Atlantic >>>>>> Oscillation (NAO). Simulations from 13 CMIP5 models that represent >>>>>> tropical eruptions in the 19th and 20th century are examined, focusing on >>>>>> the large-scale regional impacts associated with the large-scale >>>>>> circulation during the NH winter season. The models generally fail to >>>>>> capture the NH dynamical response following eruptions. They do not >>>>>> sufficiently simulate the observed post-volcanic strengthened NH polar >>>>>> vortex, positive NAO, or NH Eurasian warming pattern, and they tend to >>>>>> overestimate the cooling in the tropical troposphere. The findings are >>>>>> confirmed by a superposed epoch analysis of the NAO index for each model. >>>>>> The study confirms previous similar evaluations and raises concern for >>>>>> the ability of current climate models to simulate the response of a major >>>>>> mode of global circulation variability to external forcings. This is also >>>>>> of concern for the accuracy of geoengineering modeling studies that >>>>>> assess the atmospheric response to stratosphere-injected >>>>>> particles.Received 13 February 2012; accepted 24 July 2012. >>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "geoengineering" group. >>>>>> To post to this group, send email to [email protected] >>>>>> <http://[email protected]> . >>>>>> To unsubscribe from this group, send email to >>>>>> [email protected] >>>>>> <http://[email protected]> . >>>>>> For more options, visit this group at >>>>>> http://groups.google.com/group/geoengineering?hl=en. >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "geoengineering" group. >>>>>> To post to this group, send email to [email protected] >>>>>> <http://[email protected]> . >>>>>> To unsubscribe from this group, send email to >>>>>> [email protected] >>>>>> <http://[email protected]> . >>>>>> For more options, visit this group at >>>>>> http://groups.google.com/group/geoengineering?hl=en. >>>>>> >>>>>> >>>>> >>>>> >>>>> >>>>> >>>> -- >>>> You received this message because you are subscribed to the Google Groups >>>> "geoengineering" group. >>>> To post to this group, send email to [email protected] >>>> <http://[email protected]> . >>>> To unsubscribe from this group, send email to >>>> [email protected] >>>> <http://[email protected]> . >>>> For more options, visit this group at >>>> http://groups.google.com/group/geoengineering?hl=en. >>>> >>> >>> >>> -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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