Hi Mike, I agree that the situation is far from black and white. Ultimately it's a bit of a judgment call, weighing the risks of what we don't know about solar geo against what we don't know about climate change, and more importantly perhaps, what we don't know about how people will behave differently. I admit that my "20 years" might have more to do with my perceived timeframe for when (a) the impacts of climate change will be much more obvious and (b) where we're headed in terms of stabilizing the climate through mitigation will be much more obvious, and less to do with what we actually learn about solar geoengineering - but given that I think (a) and (b) could easily push "us" (who "us" is is a separate conversation) into wanting to do it in ~20 years, I'd rather be prepared. We'd better make a lot more progress over the next 10 years than we have over the last 10 (that isn't a dig against the research, but against the funding levels).
My hesitation with telling the House Science Committee on Wednesday that they should urgently fund a goal-oriented strategic research program is primarily that I don't trust them not to use this as an excuse not to mitigate, and IMHO not mitigating is even worse than not pursuing research urgently. (And a fair argument to make would be that nothing I say is likely to influence how much mitigation the US does, but might influence how much research is done.) doug -----Original Message----- From: Michael MacCracken [mailto:[email protected]] Sent: Sunday, November 05, 2017 10:46 PM To: [email protected]; [email protected]; 'geoengineering' <[email protected]> Subject: On when it might make sense for intervention to begin Hi Doug--In response to your Nov 4 post below, I am all for learning, but the problem with waiting and waiting is that the Earth will keep warming and warming and impacts will keep growing and growing--including especially ones that are or near irreversible, such as to biodiversity and commitment to sea level rise. If the goal were, during this 20-year learning time, only to reduce or offset year-by-year warming as might be done, based on our understanding of volcanic effects, using quite small annual increments to the stratospheric sulfur loading, and basically iterating as we go on something like 5-year running averages, we would very likely be in a much more favorable situation to evaluate how to proceed, both having better model analyses and having some experience to work with. If we find the 20-year accumulation is worse than ongoing global warming with GHGs or that mitigation is working particularly well, the stratospheric injection level could be gradually reduced instead of continuing with ongoing augmentation. While there would of course be uncertainties, it is not really clear that they would be more serious than the increasing changes and impacts that are occurring. It just seems to me that to do nothing while continuing with research just lets the situation get worse and then the cure having to be so much stronger than deployment itself could be problematic. If, as Santer et al suggest, early 21st century rate of warming was slowed by the cooling influences of small volcanic eruptions that injected amounts that were barely noticeable even with advanced instruments and really not at all noticeable by the general public, I'd suggest that we actually have a natural analog of the type of influence that I am suggesting be pursued. And, in that we will be learning along the way through the 20-year research program (let's assume that the research is funded), so it just seems, as noted above, that the uncertainties associated with such an approach would not be less than the impacts and uncertainties of deferring all intervention efforts until some probably pretty arbitrary level of understanding in the future. Regarding my favoring of regionally focused alterations, I would make that a research priority, but I'd suggest that the earlier one started injecting enough sulfur to offset each year's forcing increment or so, the better--just thinking that, in the type of relative risk framing that I view as appropriate to the situation given where we are, that, with mitigation ramping up virtually everywhere (and the US doing somewhat well despite the Administration's mistaken actions), starting very modestly with stratospheric aerosol climate intervention could really help in making sure that the situation is not so bad by the time we learn enough to "make reasonably informed decisions" (whatever that means) that we will be unable to avoid significant overshoot of the global average temperature without such aggressive intervention that we'll be suffering from both the growing impacts and then the supposed cure. At the very least, I would think a good case could be made for such an effort. Best regards, Mike MacCracken On 11/4/17 11:43 AM, Douglas MacMartin wrote: > Both SAI and MCB probably need of order of 20 years of research before > we could make reasonably informed decisions; both have a long list of > unknowns. (In the case of MCB, we don't even really know if it > "works" in any meaningful sense of the word, because cloud-aerosol > interactions are too uncertain today, so we really don't know whether > there is a useful fraction of cloud meteorological conditions in which > the albedo is significantly enhanced. We should all really really > hope that it doesn't work very well, because if it doesn't, that means > the indirect aerosol effect is smaller than current best guess and > climate sensitivity will be on the low end...) > > (And, of course, at the current level of worldwide funding, that "20" > above is probably off by a few orders of magnitude.) > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Michael Hayes > Sent: Saturday, November 04, 2017 10:00 AM > To: geoengineering <[email protected]> > Subject: Re: [geo] Can anyone offer a CE perspective on this SLR article? > > Holly and List, > > The use of sulfur needs proper polar field level testing. Testing is planned > yet may not be done in areas prone to Polar Stratospheric Cloud formation. > Time of the season is also of the essence for testing. > > Until that is done, SAI has a large question to answer; in general terms. > > MCB, used in key areas, is a critical first step. There should be no > deflection at that engineering level. Once MCB paves the way, other marine > capable systems can gain traction. > > What marine engineering minded person or institution would not give Steven's > word heavy weight? This is a marine issue. > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
