Hi, Mike - Thanks. I was just trying to draw basic links between local RF effects and actual air levels at the ground since the general response to the question about troposhperic use was that it's too dangerous. But let's say that, in my imagination, I was in fact imagining something specific, like ships with smokestacks on them going around, about the height of a typical smokestack, and you are saying that local conditions make the amounts that actually reach ground level air quite different regionally, is that right?
In general, in the much colder, dryer air there, would more or less of them stay aloft, fall out by dry or wet deposition, etc? The same MIT paper said there was about a 4 day lifetime of sulfate aerosols here in eastern US, and you're saying a week, is that difference reflective of such, or just from speaking generally? What about local wind patterns, etc.? Or let's take this the other way: starting from a specific delivery source, like release at the height of a smokestack, at the ESAS what, in the simplest way, would happen differently to the aerosols? Roughly, could we, all in all, probably emit more or less, to reach about the same maximum tolerable level of ground-level loading? Fundamentally, I'm just trying to say that there's a degree of pollution that we all accept as reasonable and not terribly harmful, so let's start from there and simply work back to see how much S that entails and how much RF change we can get from that in one very targeted area. So, if we wanted to allow about ~12ppb SO2 over the area of methane hotspots around the ESAS, do these differences, aside from the obvious insolation differences (and we're only talking about doing it during the summer), generally increase or decrease the amount of -RF we get from that? All best, Nathan On Mar 21, 8:25 am, Mike MacCracken <[email protected]> wrote: > Hi Nathan--Just a note that the sulfate layer is mainly based on what > happens above the boundary layer (so lifetime is of order a week) and the > NAAQS levels of SO2, etc. are at the surface, so not directly comparable. > Once surface SO2 emissions were reduced by switching away from coal for home > heating, etc. in the first third of the 20th century or so (at least in the > US), the thrust of air pollution control for SO2 for the middle third of the > century became to loft it so it blew away from the source (unintentionally > creating the sulfate loading), and only later became focused on simply > reducing SO2 emissions. So, one has to be careful of the linkages you make. > > I certainly agree the calculations need to be made. > > Mike > > On 3/20/12 10:30 PM, "Nathan Currier" <[email protected]> wrote: > > > > > Since none of those with the skills to do these calculations much more > > professionally seem to be jumping in quickly to take over the reigns, > > I'll try not to embarrass myself in giving initial crude answers to my > > own question from the other day, which follow: > > > I find that in a recent paper from MIT (Leibensperger, 2011), the > > localized RF from sulfate aerosol¹s direct effect for the eastern US > > is estimated as -.3W/m2. Then, if we estimate for Twomey/Albrecht > > indirects, we can say roughly something like -.5W/m2 for the current > > eastern US sulfate forcing. > > > What are the sulfur levels giving this RF? The basic NAAQS - annual > > average primary standard - is still unchanged from the 1970s. (http:// > >www.epa.gov/air/sulfurdioxide/), at 30ppb (about 80 micrograms/m3). > > But in actuality, average regional levels now only range from 1-6ppb > > across the US. There was apparently talk lately of introducing a new 5- > > minute standard for asthmatics, but it was not done, and I think we > > can all agree that a geoengineering approach could be designed to > > avoid spikes pretty well, so the annual average of course, in our > > case, it would really be a three or four month average is alone what > > matters here. > > > So, let¹s examine some actual current annual average local levels a > > bit. > >http://www.epa.gov/airtrends/sulfur.html > > > I live now in New York City. The most complete reading here is from a > > midtown Manhattan monitor station, where as recently as 2003 SO2 seems > > to have been around 14ppb, but the data ends in 2007, by which time it > > had dropped to ~11ppb. I used to live rather close, it would seem, to > > that particular monitoring station back in the early 1990s, when the > > levels it read were closer to 20ppb, but let¹s take something nearer > > the lower figure and be conservative. Either way, this area entails > > some of the highest readings in the eastern US for SO2 pollution that > > I found. > > > Look at the interactive map's levels around the rest of the eastern US > > - they are really surprisingly low now almost everywhere. I was > > shocked when I looked at it (no wonder warming is ahead of the models! > > At least it suggests the termination effect won¹t be too bad here in > > the US - we¹ve already gone through much of it!). Within that 1-6ppb > > range, let¹s say it¹s an average of 3ppb? > > > Now, then, is it not accurate to say that we should be able to go up > > to 3x or even 4x that -.5W/m2 without making any air that is worse > > than Manhattan's has been very recently? That is, if we aimed for > > ~12ppb level. Is this really so bad, so evil? I didn¹t realize I was > > torturing myself by living here! I walk my dog almost daily in the one > > old growth section of the city (Inwood Hill Park), where there is > > plentiful lichen, moss, etc. Birds of all varieties seem healthy and > > in robust populations. A new species of leopard frog was just > > discovered here, as you might have read the other day. It is not > > pristine, but I found a crayfish walking around by a stream in Central > > Park. I have even had asthmatic friends who love living here, except > > in the heat of summer. > > > Is this air I am breathing every day really so noxious and dangerous > > that you would not want to consider using it, in an almost completely > > unpopulated area moreover, even if thereby you could help stave off a > > potential arctic disaster? Really? > > > Next, what are the levels of SO2 currently in Siberia? There is one > > former gulag site where there is today smelting and other industry > > that emits massive SO2, but that is far from the ESAS and otherwise > > the level seems to be very low. One recent paper I found (Lee et al, > > 2011), that aims to constrain SO2 global emission estimates by looking > > at ozone and other satellite data (OMI and SCIAMACHY), makes it appear > > in a map as though the area in question is extremely low, although it > > is not at all detailed. > > > Thus, my supposition is that we could possibly get some 2W/m2, > > possibly half the local net forcing, without creating any air worse > > than New York City¹s has been just in this past decade. Please > > correct me if that seems to be mistaken. > > > The current modeled estimates for ESAS talik extent suggest about 3-5% > > of total area. Thus, to give an adequate buffer around this, to > > effectively cool incoming waters, etc, covering 10% of ESAS area = > > ~50,000 sq. miles. Now, maybe some of those with better expertise can > > figure the dispersal rates, column depth, etc, etc and estimate how > > just how much sulfur this would entail, that is, to emit enough S to > > cover ~50,000 sq. miles with about 12ppb SO2 for about four months per > > year, how much sulfur is that? Thanks much in advance for your answer, > > I appreciate it. > > > Lastly, in terms of the addition of methane effects, I find that it > > would at best add only about .1W/m2, and possibly almost nothing > > measurable. Using a very rough methane RF (including all indirect > > effects, i.e., from Shindell et al, 2009) of 1000ppb=~1W/m2, then with > > an anomaly there ranging from +100-200ppb, and a possible maximum 40% > > reduction emission rate from local wetlands if the anomaly were > > completely caused by wetland emissions, which I very strongly doubt > > then still at best one would only get -.1W/m2. So that factor would be > > very unlikely to be significant. Obviously, MCB could/should then be > > added to or combined with the above. Latham hasn¹t responded, so maybe > > someone else could give a rough estimate of what the options might be > > to use them together and what those effects might be? > > > I am, I confess, somewhat frustrated by some of the experts here > > excepting Mike not in their expertise, which I always find > > impressive, but in their seeming inability, or perhaps unwillingness, > > to use such expertise more flexibly. John Nissen¹s exchange with > > Latham a few days ago, with John¹s poignant questions, I found almost > > painful to read, frankly (of course, I can appreciate that MCB deals > > with much the same complexities as CLAW, which after 800 papers is > > still mired in controversy but maybe that only connotes that another > > 5 years of modeling still won¹t alone resolve John's questions, but > > doing Lovelock¹s version of what some have branded ³improvisatory > > experimentation,² i.e., simply getting out into the field and making > > small prototypes and playing around variously with different > > parameters until you start to get what you are looking for, could be a > > better and quicker way to go?). > > > As to the fundamental question of risk in dealing with tropospheric > > SO2, I think it¹s probably safe to say that there is likely zero > > global-scale risk whatsoever to the proposed plan. The risks of a > > large-scale excursion of methane, if one took place, on the other > > hand, are without question extraordinary. I think that¹s the kind of > > circumstance where you decide it¹s best to act with relatively > > imperfect knowledge. None of us know what the probability of a large > > CH4 emission really is. And none will ever know what "might have > > been", whether we act or don¹t act, had we taken the ³other path.² > > That's what decision is all about. Nor do I imagine that anyone can > > really say whether what I am proposing would actually be effective, > > but as I just suggested for John's designs, one could always alter the > > parameters easily in real time. > > > I think that in a larger context of fighting climate change > > altogether, what I'm suggesting also represents one possible ³step 1² > > or ³2² towards the lowest-possible-risk pathway forward, which is what > > everyone should be striving for, it seems to me. That is, the > > combination of a very large and rapid non-CO2 (CH4/BC) emissions > > program (please keep in mind, members of AMEG, that the recent > > Shindell paper had the good news that, if Asia is less important for > > Arctic BC forcing than some thought, it also means that a rather small > > number of northern European and Scandinavian countries can be quite > > important in reducing that arctic BC forcing and therefore AMEG > > could and should ALSO be engaged in urgently requesting the UK > > government to be the spearhead for such a program, including more > > advanced diesel filters, etc) and at the same time, alongside it, > > some kind of small-scale, pinpointed geoengineering program like the > > one I am suggesting here, should, if done together, be able to push > > back strongly against the dissolution of the arctic as we know it for > > a while. Obviously that's hardly the end of the story, just steps 1 > > and 2, the first chapter. > > > Then, along with steep declines in carbon emissions, the kind of SRM > > geoengineering that some here consider ³serious² (both Revkin and > > Keith used that word in recent days seemingly to distinguish what they > > have in mind from what I am proposing), best pegged exclusively to > > lost aerosol loading (thus, no setting of any global ³thermostat² as > > in Keith¹s conundrum), which would then itself be pegged in its > > termination to subsequent CDR, through biochar, reforestation and > > other technologies like Keith¹s artificial tress, etc. All > > ... > > read more » -- 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]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
