Hi David‹I would suggest that the attached paper might be interpreted to give support to the idea that the approach might well work. The plume described in the paper you attached came from a pretty concentrated source region so the concentrations were high and the proposal for tropospheric sulfate engineering would have emissions much more dispersed. What is interesting in the paper is that the plume stays aloft and the paper (at least the abstract) does not indicate any impact on human activity except a mid-tropospheric reduction in visibility. And the lifetime is pretty long, again indicating that the amount injected can be relatively limited compared to surface injections.
All approaches are going to require some trade-offs, and it seems to me mid-level visibility might well be worth the benefits of limiting warming. That is just the type of comprehensive evaluation that needs to be done. Mike On 5/1/12 3:42 PM, "David Hawkins" <[email protected]> wrote: > Mike, > We have evidence of long-distance transport of sulfur-laden plumes (see, eg, > http://www.atmos-chem-phys.net/9/4729/2009/acp-9-4729-2009.pdf). What > confidence do we have that sulfur injection at a scale that achieves > meaningful reductions in forcing will not reach populated areas? > David > > > From: [email protected] [mailto:[email protected]] > On Behalf Of Mike MacCracken > Sent: Tuesday, May 01, 2012 3:09 PM > To: Geoengineering > Cc: [email protected] > Subject: Re: [geo] Regional SRM experiment > > Hi David H and David K‹For purposes of debate, I¹ll venture an alternative > viewpoint on point 2. > > The approach, however, would not be to inject the SO2 as it is now injected > nor where it is injected, but to do it in a way that would greatly reduce the > adverse impacts while getting much more benefit from the emissions. > 1. The key problem with current SO2 emissions comes from their location and > link to coal-fired power plants. If both links can be broken, then it seems to > me there are some possibilities. > 2. Putting the SO2 out from power plants puts the emissions mostly where > people are (so health effects‹some suggest probably more from the other > pollutants that come out along with the SO2, which may be more a proxy than > the culprit). In any case what one would want to do is to have emissions where > can have maximum effect on solar radiation, and this would be at low latitudes > where sun is at maximum and over the oceans so one has a dark surface below > for maximum albedo contrast. One would also want the emissions put up into the > free troposphere to lengthen their lifetime, and not at surface where people > are (at those altitudes, use the sea salt approach of Salter and Latham). > 3. Power plants also put out SO2 when there is need for electricity‹ideally, > one would put the SO2 out when weather and chemistry is favorable for extended > lifetime (so could use a few fixed locations for injection and let winds carry > the SO2/sulfate over broader areas). Emissions need not be steady in time as > we are aiming at cumulative effect. > 4. So, I would suggest that having lower loadings over larger areas such as > the remote (and largely unpopulated) areas of the low albedo Indian and > Pacific Oceans (and above the boundary layer so not generally exposing people) > could allow much more effect for a given emissions amount than the present SO2 > emissions that are concentrated where people are and where sun angle is low > for much of the year. > 5. Yes, there could still be impacts when sulfate got carried over land areas > and deposited. But main deposition impacts on ecological systems was when > accumulated on snow during winters (low light periods that really serve little > purpose for SRM) and when got deposition in dew (again, not something that > would be likely with proposed strategy above). And do note that in some areas > farmers add sulfur to the soils, so sulfur deposition is not a problem > everywhere. In any case, the concentration would be lower as would be much > more spread out. And, it could be that one could go to another material than > SO2 if impacts were large‹or go to sea salt. > 6. As to comparisons with other approaches: >> 1. Cloud brightening would require a good bit more effort for injection as >> CCN lifetime is pretty short, but then effect on cloud albedo is likely more >> significant than having aerosols above the boundary layer. For free >> troposphere injection, would likely get a bit greater clear sky effect. Yes, >> an impact is reduced visibility‹but how does that compare to other benefits? >> 2. Compared to stratospheric SRM, this would not have problem of turning >> direct to diffuse radiation over all land areas, so not affecting direct >> solar technologies, would not have the stratospheric ozone depletion problem, >> could more quickly be terminated in event of major volcanic eruption, and >> would not require the effort of stratospheric injection as might be able to >> do from some elevated hills, etc.--or at least much lower altitude balloon >> held pipes. >> 3. I would also suggest that tropospheric sulfate would allow a more targeted >> effect than possible with stratospheric sulfate and does not require ocean >> access, so might be useful for regionally focused types of interventions, >> such as to limit Arctic warming. > 7. Thus, I would not rule it out so fast. It seems to me, given that reducing > emissions from coal-fired power plants and for air pollution clean-up, that > the cooling offset of existing SO2 emissions is going to go down, and the > question is how best to offset this plus the continuing rise in the CO2 > concentration even despite mitigation and adaptation. It seems to me that > governance issues might be easier with tropospheric rather than stratospheric > emissions, largely due to familiarity (as David Hawkins other points suggest, > there is a lot of learning possible from what has been done to date and what > is going on). Even though the amount of the emissions needs to be higher than > for the stratosphere due to shorter lifetime, the amounts are likely still > less than what world has been putting out, and the design of effort would > greatly reduce adverse impacts. So, what is needed in my view is a > comprehensive relative risk and cost evaluation‹cavalierly dismissing the > possibility seems to me premature. > > Mike > > > On 5/1/12 1:32 PM, "David Hawkins" <[email protected]> wrote: > Hi David, > My thoughts on your points: > > On 1. I am wondering more about the opportunity to do measuring of phenomena > than testing. Others will have to say which phenomena would be the most > interesting to observe and whether current instrumentation is adequate. But I > assume that more detailed observations on the fine points aerosol forcing and > second+ order effects would be the most likely targets. > > On 2. I sure hope no one is thinking of tropospheric SO2 injection for the > reason you mention. > > On 3. My initial comment about fine particle pollution reduction being > inadvertent geoengineering was most tongue in cheek. But there is an > underlying question that I am interested in getting expert views on: can we > learn anything useful about forcing and second+ order effects by gathering > data on changes to the atmosphere in a region like the eastern US that are > associated with these recent and projected changes in particle loadings? If > so and there are gaps in instrumentation, it would be a good idea to come up > with a proposal for such instrumentation improvements. > David > > > From: David Keith [mailto:[email protected]] > Sent: Tuesday, May 01, 2012 1:07 PM > To: Hawkins, Dave; [email protected]; [email protected] > Cc: [email protected]; Debra Weisenstein ([email protected]) > Subject: RE: [geo] Regional SRM experiment > > Folks > > I am not getting this, and yet I am close to it. My office is down the hall > from the GEOS-Chem group that produced these papers. We collaborate in that > Debra Weisenstein works with me and with that group is doing modeling for > geoengineering and looking into improvements to the GEOS-Chem stratospheric > chemistry. > > 1. Can someone tell me exactly what would be tested here? Climate response? > Aerosol radiative forcing? > > 2. Is there a sensible reason why you one would prefer troposphere SO2 for > geoengineering if one wanted to do it? Recall that trop SO2 now is linked to > about 1 million air pollution deaths per year globally as well as acid rain > etc. > > 3. The idea that cutting tropospheric SO2 pollution is a form of > geoengineering would seem to me to extend the definition of geoengineering to > mean, in effect, ³any human action that may alter the climate². I doubt this > definition will help clarify debate. > > Yours, > David > > > > > > From: [email protected] [mailto:[email protected]] > On Behalf Of Hawkins, Dave > Sent: Tuesday, May 01, 2012 10:51 AM > To: [email protected]; [email protected] > Cc: [email protected] > Subject: RE: [geo] Regional SRM experiment > > Nathan, > > The CEC report you link to was useful but is now dated. Much more current > information on SO2 emissions (up to and including 4th quarter 2011 for the > power sector) is available thanks to the 1990 Clean Air Act, which required > SO2 continuous emission monitors on all coal power plants in the 48 contiguous > states of the US. > > A handy spreadsheet of national SO2 emission trends from 1980 to 2010 can be > found here: > > http://www.epa.gov/airmarkets/progress/ARPCAIR_downloads/CAIR_ARP_2010_data_1. > xls > <http://www.epa.gov/airmarkets/progress/ARPCAIR_downloads/CAIR_ARP_2010_data_1 > .xls> > > This spreadsheet also includes data disaggregated by state and by month. > > Other pages at the airmarkets link above will get you access to hourly > emissions and operational data from all significant US coal power plants. > (FWIW, getting the rules in place to require these data to be reported at all, > much less to be reported electronically and accessible to anyone, required > quite a lot of persistent advocacy.) > > The national SO2 trends are informative as to the scale of the reductions from > more than 17 million tons of SO2 from the power sector in 1980 to about 5.2 > million tons in 2010. The combination of EPA¹s new transport rule and toxics > rule will cut the load further to about 2 million tons in the 2015-2016 time > frame. http://www.epa.gov/ttn/ecas/regdata/RIAs/matsriafinal.pdf, Table 3-4. > > But the additional instrumentation I was referring to in my email was not > emission monitoring data (as the above information indicates, we now have that > pretty well in place in the US for the power sector). Rather, I am thinking > of high resolution data of the characteristics of the atmosphere that might > change as these additional emission reduction occur. I don¹t know enough to > have anything in particular in mind but I imagine there are some on this list > who could identify the data sets they would like to have to fully characterize > the forcing and other aspects of the changes brought about by the large SO2 > reductions from 1980 to date and from the large additional percentage > reductions that will occur over the next 3-5 years. For example, how linear > or nonlinear are the forcing responses to a given tonnage reduction in fine > particle precursors or a given ppm change in fine particle concentrations. My > hunch is that the localized impacts will differ depending on the baseline > atmospheric conditions on which the emission changes are imposed. Knowing > more about that might be nice to help improve modeling estimates of the > local/regional impacts of SRM experiments. > > David > > From: [email protected] [mailto:[email protected]] > On Behalf Of Nathan Currier > Sent: Tuesday, May 01, 2012 11:38 AM > To: [email protected] > Cc: [email protected]; Geoengineering > Subject: Re: [geo] Regional SRM experiment > > Hi, David - > > I fully agree with that, and actually used that same MIT paper in something > I wrote up for the group AMEG recently. In fact, if you look at table 3.3 in > this - > > http://www.findthatfile.com/search-19564999-hPDF/download-documents-4876_power > plant_airemission_en.pdf.htm > > you'll also see that of the top 10 highest SO2-producing > power plants in the US - and these are the only US plants that put out > over 100,000 mt SO2/yr each (and their inputs get smaller pretty quickly as > the sizes decrease) - 7 of the 10 are just in Penn & OH alone. > On the "dot map" of US SO2 emissions in the attached, these two states are > almost invisible, being swallowed up by a big dot for all the SO2 there. > I don't have a figure for the average loading of the two states, but it > could be roughly ascertained pretty easily by EPA's SO2 trends map. > > Anyhow, just a study of the SO2 in these two states, Penn and Ohio, would > be the most helpful, and in fact possibly even more useful *because* it's > in the troposphere, I feel. But it needs to be done very soon, as the new > > CAIR program rules are apparently going to reduce all of this a good deal > > more in the next 3-4 yrs, I believe. > > All best, > > Nathan > > > On Monday, April 30, 2012 2:44:33 PM UTC-4, David Hawkins wrote: > > The largest insight I draw from this paper is the reminder that there are > fairly large-scale activities going on right now that might provide useful > information regarding SRM if we had systems set up to monitor resulting > changes. > > This paper documents one of them the large reversal of sulfate loadings in > the eastern half of the US, mostly occurring since the 1990 Clean Air Act was > passed. And those reductions will continue. Rules promulgated by EPA in the > > last six months will required millions of tons more of SO2 and NOx reductions > over the next 3-5 years. > > It would be nice to do a rapid assessment of what additional instrumentation > might produce even more useful information, relevant to the many unanswered > questions about SRM. To be sure, most of these reductions are > > occurring in the troposphere and so may not be directly applicable to SRM in > the stratosphere. Still, I imagine there could be useful information to be > gathered. It might be much easier to get governments to devote some > > money to such an enhanced measurement effort than to try to stand up some new > ³geoengineering program.² > > > > > > > > From: [email protected] <mailto:[email protected]> > [mailto:[email protected] > <mailto:[email protected]> ] On Behalf Of Mike MacCracken > Sent: Sunday, April 29, 2012 8:38 PM > To: Geoengineering > Subject: Re: [geo] Regional SRM experiment > > > > Hi David‹Very interesting, and just why it might be possible to do something > to limit warming in an area like the Arctic, which, as was documented over and > over again at the Montreal IPY meeting last week, is changing very fast. > > Mike MacCracken > > ******** > > > On 4/28/12 10:06 AM, "David Hawkins" <MailScanner has detected a possible > fraud attempt from "[email protected]" claiming to be [email protected] > <http://[email protected]> > wrote: > > Climatic effects of 19502050 changes in US anthropogenic aerosols Part 2: > Climate response > http://www.atmos-chem-phys.net/12/3349/2012/acp-12-3349-2012.pdf > <http://www.atmos-chem-phys.net/12/3349/2012/acp-12-3349-2012.pdf> > > > Reduction in air pollution from coal fired power stations due to environmental > regulations since the 1980s has increased regional global warming in the > Central and Eastern United States. Climate scientists from the Harvard School > of Engineering and Applied Sciences (SEAS) found that particulate pollution, > particularly from coal fired power stations, caused a global warming hole, or > a large cold patch reducing temperatures by up to 1 degree C in the region, > particularly lowering maximum temperatures in Summer and Autumn. > > > > Since I have spent a good deal of the past several decades advocating for > rapid deployment of particle reducing techniques, I guess I can be tagged as > an inadvertent geoengineer. > :>) > > Sent from my iPad > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected] > <mailto:geoengineering%[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 view this discussion on the web visit > https://groups.google.com/d/msg/geoengineering/-/PRIGiFXTufkJ. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [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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