I had written this yesterday, but accidentally sent it just to David Keith and not the group.....
Thanks much. First, in terms of your 3. below, that was from Dave, and not me, so he could take that up further, perhaps..... In terms of 2., I'm not sure what Dave meant there either, but I could imagine wanting to look into relations between current aerosol localized radiative forcing in Ohio, say, the current ground level SO2 readings there, and then current health statistics there, too, to see, for example, whether the 1 million figure you cite - which is of course concerning to everyone who cares about the common good - is necessarily relevant, given the amount of SO2 that would be needed to get a useful localized -RF effect if emitted at some level of the troposphere (obviously not in Ohio, however! - quite the contrary, this would be intended for largely unpopulated strategic regions). In terms of 2. - which I think is really the most interesting part of this - it seems to me that, while it might not in the end work all that well, the idea of a super-pinpointed project to cool the region with most of the methane hotspots around the Siberian shelf, if their emissions should increase a lot, is something that should really be explored. Even if a large emergency non-CO2 program for emissions reductions of BC/CH4 were undertaken to grapple with a situation like that (i.e. a great expansion of the program the US state Dept recently started, or the GMF, etc), it would probably take at least a few years to start showing much effect, so something to locally effect the region in the meantime could be hugely helpful, if Gt-scale releases started to take place. Most of the methane hotspots are currently focused within a ~50,000 sq mile area of the shelf around Tiksi. It seems to me that sensible reasons behind this line of thinking include: that tropospheric injections could be pinpointed to a specific region much more than stratospheric injections ever could; because the region is small and the total injections would consequently be so small (probably less than 1 large US coal plant to achieve ~-5F for the region) , the side effects of doing this might in the end turn out to be far less, rather than greater, than using the stratosphere (i.e., no global scale perturbation of hydrological cycles, etc.); it demands little new technological development, and would have fewer possible surprises, since we have 200 years of experience doing it already; as Mike MacCracken has noted, such a program could take advantage of the shorter aerosol lifetime at lower altitudes, to adjust and stop emissions rapidly where any harm was being caused; it would not be an expensive program, possibly costing as little as $15 million per year; its governance would not be a large multinational issue, since it would be entirely on Russian territorial waters or soil (and the SO2 pollution that has been wafting into neighbors like Norway from Russian companies like Norisk Nickel has been far, far greater than this could ever be); it should potentially be a legal entity to have it as a corporation (a non-profit) sited in Russia, and the state fees imposed through Russian air quality regulations for the SO2 in those quantities would total perhaps only some $50,000/yr. The idea, in my thinking, would be to minimize the "geoengineering footprint" and to depend upon emissions reductions as much as possible, and while I think it might be counterintuitive that using the troposphere could help with this, I actually think it might, if one considers certain locales as having great global strategic importance, like the ESAS and its carbon stores. All best, Nathan -- 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/-/sNJXVbpj2NgJ. 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.
