Thanks, Mike, for the excellent responses, with which I agree 100%. Do you have handy a link to the new UNEP assessment you mention? I'd much like to see it.
One of the things that often perplexes me is why CCS from burning coal at a plant is generally considered geoengineering, but trapping the methane that escaped in mining that very same coal is generally not. For purposes of this site, where thinking is on a much higher level than in general climate discourse, I hope that we can consider both equally to be "geoengineering" (or neither, I suppose, depending on how one wants to define geoengineering). In any case, a major point of mine for a number of years now has been that the best, safest, cheapest, way to cool the planet quickly (at least to help put off tipping points into the future, if not enough to avoid them altogether, so that SRM, etc, would be ready) will likely be shown to be rapid methane emission declines (or CH4/BC). In the past I've written here my own estimates of what is possible - rough amounts, their resulting radiative forcing effects and evolution in time-scale, and their costs - saying that the maximum amount that could be spent now is ~$250 Bn. But economics works on minimums, of course. The M2M (now GMI) program has thus far only been spending about $10Mn/yr for a half decade, or $50Mn. But they say that this spending has leveraged $387Mn in total project investments (or a 7.7x leveraging). Clearly $250 Bn wouldn't really need to be spent. Since one wants to insure maximum speed, one can guess that actual spending would need to be > $32.5Bn, but even assuming just a three-fold leveraging, ~$80Bn total could probably achieve about the same as the $250Bn, a relatively pronounced near-term forcing decline for the arctic (i.e. effects beginning to be felt in a few years from onset of program). Were there even a mild carbon market price of $14/t CO2e, the methane trapped that I am talking about would have a ~$40Bn/yr value, and even without any such market, it provides a formidable income stream (which is why governments, international corporations and lending institutions, etc, have so greatly leveraged the rather meager US investments). So, even just $5-8Bn from each of a dozen wealthy nations might be enough to make a HUGE difference in our current emergency, if we can figure out how to make this into an appealing "methane game." In recent posts, people have been talking about how to trap methane down in the arctic taliks and so on. At present there's an estimated total of ~8 MMt/yr coming from there, and it would be a most messy business, but easily well above 10x that could be trapped quickly through currently planned projects, while also providing an appealing profit stream, all around the world, and probably having more climate effect/t, since it would effect the larger ocean/air currents entering the arctic from outside that are a large part of what's pushing it out of its current state. This is the best "geoengineering" we've got at the moment, I believe. Call it "methane CCU" - carbon capture and use, that is - if it feels more like geoengineering that way. Again, a total -RF equal to some 1/3 of the net positive forcing is at stake with this approach. In terms of Michael Hayes' comment, The notion of un-known/hypothetical feedbacks denuding SRM efforts is interesting. In that, it is injecting a double-false conditional into the debate. This is more of a media tool than a scientific one. I'd like to mention something that partly underscores why I continue to say that methane seems like the real key, more than BC, even though some BC sources are cheaper per unit of -RF. BC is quite complex and gives both positive and negative forcings, and has its positive forcing *increased*when in a general mix of negative forcing aerosols. That's precisely the kind of feedback that Hayes is dubbing hypothetical - it isn't, but such aerosol/aerosol interactions are vastly problematic to ever get a precise handle on, so it makes things less certain in terms of resulting effects (both for BC reductions and for any SRM done at an altitude where it could interact, by the way, if Ramanathan's very large 1W/m2 BC forcing is right). I much agree with Drew Shindell at GISS, in his saying that methane reductions have a very low level of uncertainty. (That being said, taking down the 20% or so of BC from very inexpensive to change sources around the Himalayas should obviously be one of the very first things that we do, if possible.) So, in terms of Andrew saying he's much more "gung-ho," I'm not convinced. I quite agree with the despondent tone of some recent posts, suggesting that even full-scale SRM might become ineffective, if we let the arctic go too far on its own. So, to truly get gung-ho, what we all need now is to switch gears a bit - sure, keep thinking about "boil and bubble, toil and trouble" brightwater innovations and so on - but what we REALLY need to figure out is how to get ASAP some $50-80Bn going on a global methane project. Could the UN start a new program, a "game" taking off from the GMI with 15-20 countries putting into a kitty, and a central structure putting together high-incentivization loan schemes in target countries (i.e. with "lowest-hanging fruit" projects) to allocate from it? If one wanted it to be "free," like the recent US bailouts, all players could then be paying something back on their profit streams over a multi-decadal period, ultimately paying back the original investors. So, a 20 yr plan that aims to have maximum methane draw-down up front, but works so that the largest initial investors get all or most of the investments back near the end. Maybe we don't need much US money to get it going, if the US would be hard to get anything from. China, UK, Eurozone, etc, could be the largest initial investors, perhaps? Cheers, Nathan -- 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.
