Hi Greg--I think you have to account for the airborne fraction--it is about 4 GtC emission (or about 15 GtCO2) per ppm (assuming airborne fraction is roughly a half).
Mike On 8/22/15, 3:19 PM, "Greg Rau" <[email protected]> wrote: > It seems to me that the value of CO2 and SRM can be interrelated via warming > potential i.e. W/m2. If a doubling of air CO2 leads to a 3.7 W/m2 increase in > forcing (IPCC), then doubling the current air CO2 load (400ppm x 7.76 > GtCO2/ppm)= 3104 Gt CO2) to 6208 Gt CO2 means that for every Gt CO2 of the > total of 3104 Gt added we increase the forcing by 0.0012 W/m2. Assuming that > for every Gt of CO2 emitted only 45% stays in the atmosphere (in the near > term) then the net forcing is 0.00054 W m^-2 per Gt CO2 emitted or 0.54 picoW > m^-2 (tonne CO2 emissions avoided)^-1. If the social value of avoiding CO2 > emissions is $30/tonne (Uncle Sam) and that cost only takes into account > climate effects (not ocean acidification) then the value of either CO2 > avoidance or SRM is $56 per pW/m2 avoided - no? Then in the case of SRM the > issue becomes required timeframe of the avoidance - 100 years? > > Greg > > -------------------------------------------- > On Fri, 8/21/15, Andrew Lockley <[email protected]> wrote: > > Subject: Re: [geo] Tricky question - SRM / carbon credits > To: "David Grober-Morrow" <[email protected]> > Cc: "geoengineering" <[email protected]>, "Maggie Zhou" > <[email protected]> > Date: Friday, August 21, 2015, 1:31 PM > > David (and > others) > You're right that my question was inspired > by the recent research showing that SRM gives a free CDR > kicker. But this isn't the only way you could get carbon > credits, as the temperature equivalence is a valid effect. > > The question is simply one of whether there > will be any buyers. That will only be discovered when people > start trying to sell the first SRM carbon credits. > Bearing in mind you can get carbon credits from > forestry schemes, my guess is that current credits > aren't bought or sold on the basis of longevity. Having > an SRM credit that's calibrated against an avoided ton > CO2 over 100 years seems reasonable, and one that's > equivalent over 1000 years would seem essentially > irreproachable (based on RF). > If people think this is illogical, > illegitimate, immoral or illegal, then campaign for a ban. > Don't shoot the messenger. > Thanks > Andrew > On 21 Aug 2015 14:39, > "David Morrow" <[email protected]> > wrote: > Andrew, > I take it > that you're thinking about the recent research showing > that SRM could actually reduce the amount of CO2 in the > atmosphere by reducing the amount of carbon released from > (or not absorbed by) terrestrial sinks. (At least, I think > that's the mechanism people find in the simulations -- > if not, someone please correct me!). > I agree with Olivier that > there's no straightforward answer to the question about > how much carbon a "unit" of SRM removes/keeps out > of the atmosphere, both for the reason Olivier cited and > because I take it the magnitude of the carbon reduction > depends on background conditions (e.g., atmospheric > concentrations and temperatures), which would evolve over > time -- especially at the time scales needed to say that SRM > has actually prevented carbon release, rather than delaying > it. > I also agree with > Maggie that this isn't just a physics/earth science > question. A carbon credit is a social creation. SRM > isn't worth any carbon credits unless the relevant > decision-making bodies say it is. And I think it would be a > very bad idea for them to say so. > So, in short, I'd say the answer > to your question is: Currently, SRM is not worth any carbon > credits; and it should stay that way, regardless of > SRM's effects on atmospheric carbon > concentrations. > David > > On Thursday, August 20, 2015 at 7:47:40 PM > UTC-4, Maggie Zhou wrote:Hi > Andrew, > Firstly, there is no > sound answer to the question posed in terms of physics > /earth science, exactly because SRM is not a true substitute > of removing carbon, it does not confer the same effect in > terms of duration of effect, and effect on many other > aspects of the earth system other than the reduction of heat > while the aerosol is in the air. So it is scientifically > flawed to ignore all of that, in order to render a carbon > credit equivalent so as to be able to monitize SRM, just > like everything else is driven to be monitized under the > insane capitalist system. > Secondly, in > a non-voluntary system that requires carbon credits in order > to emit GHGs, SRM generated credits will simply add to the > annual emissions cap, which is what I pointed out in my last > email. In a voluntary system where people/corporations > simply purchase carbon credits to feel better or use as a PR > tool, SRM generated credits allow them to justify their > emissions which they otherwise would be under greater > pressure to reduce, and for those emissions outside of their > direct control, SRM generated credits won't help > reduce anyway. In fact they would feel even less > responsible to change agricultural emissions (advocating for > better agri practices, etc), or what their government is > doing in their name. > It's amusing, if not > also sad, that you considered what I discussed in the last > email as from a "political angle", i.e., not > "science proper". I'd suggest that what I > discussed there is simply science as applied to the physical > reality of this earth, not some abstract concept that draws > an artificial equivalence of SRM = C > removal. Peace. > > Maggie Zhou, PhDhttps://www.facebook.com/maggie.zhou.543 > > > > On Thursday, August > 20, 2015 7:00 PM, Andrew Lockley <[email protected]> wrote: > > > Maggie (and > list), > Thanks for your response. However, there are > a couple of problems with the stance you take. > Firstly, I'm simply looking to answer a > physics / earth science question. The answer will be true > whether we want it to be, or not. The world deals with many > other distasteful comparisons, such as how much is a life > worth in cost-benefit analyses. > Secondly, even if we engage with the > political angle you discuss, your logic doesn't > necessarily bear scrutiny. People may choose to offset only > the components of their emissions they have no control over, > eg agriculture, government sector, etc. I'd suggest that > those buying carbon credits are probably more prone to > taking mitigation action than demographically matched > controls. > I'd welcome further dialogue. > Thanks > Andrew Lockley > On 20 Aug 2015 23:49, "Maggie Zhou" > <[email protected]> > wrote: > "How many > carbon credits is a tonne of SRM > worth?" > Seriously? This is > precisely what geoengineering proponents promised that it > won't be used for - as a substitute in any way, shape or > form to carbon emission mitigation. To get acceptance for > the idea of even funding research into SRM or other > geoengineering schemes in response to global warming, the > repeated promise was that it is not meant to replace > emission reductions, only a backup to buy us some > time... > Using SRM to generate carbon credits is EXACTLY to > generate EXTRA carbon emissions allowances - even though all > SRM could do, at best, is masking the true impact of the > current GHG levels on warming while the spraying is ongoing, > without ever removing a single atom of carbon from the > atmosphere for which it's to claim carbon credit. In > short, SRM will lead to even MORE emissions, not less, and > due to the masking and the lack of public awareness that > it's the masking that's keeping the temperatures > from shooting up even higher even quicker, it just helps > keeping business-as-usual longer, on top of ocean > acidification, acid rain, potential disruption of regional > climate patterns, etc etc. > > Maggie Zhou, PhDhttps://www.facebook.com/maggie.zhou.543 > > > > On Thursday, August > 20, 2015 4:15 AM, Andrew Lockley <[email protected]> wrote: > > > How many carbon > credits is a tonne of SRM worth? > We could work this out as watts cooling or > weight sulphur for weight carbon. Doesn't really matter. > > Thanks > Andrew > > > > -- > > 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 http://groups.google.com/group/geoengineering. > > For more options, visit https://groups.google.com/d/optout. > > > > > > > > > -- > > 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 http://groups.google.com/group/geoengineering. > > For more options, visit https://groups.google.com/d/optout. > > > > > > > > -- > > 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 http://groups.google.com/group/geoengineering. > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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