Mike, I could be wrong but i was under the impression that the relevant time constant (inverse rate const.) characterizing the gradient-driven gross flow of CO2 from air to sea is on the order of a decade or two. A result I thought obtained from C14 tracer studies. I am also under the impression that the year to year variation in the sink strength does not track annual emissions very closely, suggesting that there are longer time constants in the system (as well as "noise" from variations in wind etc. and inter annual variability in the terrestrial sink).
It's been a while since I looked at this so maybe my understanding is out of date. Cheers, John John Harte Professor of Ecosystem Sciences ERG/ESPM 310 Barrows Hall University of California Berkeley, CA 94720 USA [email protected] On Jan 25, 2015, at 1:27 PM, Mike MacCracken <[email protected]> wrote: > Hi John and Greg—So responding to both messages (and I pasted John’s into the > thread) > > I would think the terrestrial biosphere time constant is a decade or two, but > for the ocean, I’d suggest that it is much shorter. My understanding is that > the time constant of the wind-stirred ocean mixed layer is a year or two—not > a decade or two. Changing the net flux rate to the deep ocean would be pretty > slow, but that net flux is pretty small. > > And so, how would it work. Well, in terms of the net flux to the ocean, the > CO2 is driven into the upper ocean by the gradient between the atmosphere and > the upper ocean, so once one stabilizes the atmospheric concentration and the > ocean mixed layer concentration catches, up, there will be no gradient to > drive the flux. > > Well, this is not quite correct as the net flux to the deep ocean would > continue, so there could be a net flux from the atmosphere to the upper ocean > to make up that difference. However, the ocean surface layer would also > continue to warm as there is a lag in the thermal term—and so the warmer the > mixed layer, the higher the CO2 partial pressure would be and this would tend > to resist uptake of CO2. > > In terms of gross fluxes, the carbon rich upwelling waters would end up > giving off a bit more CO2 with CO2 stabilization as opposed to the situation > were the CO2 higher, and the uptake in high latitudes where water is cold > would not be going up because the atmosphere-upper ocean gradient would be > less, so again, one would lose the ocean sink, and that would mean that a > greater share of any emissions that did occur (so in reducing the CO2 > emissions from 37 Gt CO2/yr, one does not get to assume the ocean sink would > continue as it has—and I suspect that would be a pretty fast adjustment. > > For the biosphere, John suggests that he is quite concerned about the > continuance of the terrestrial sink (basically, it seems, whether or not one > stabilizes the CO2 concentration). > > So, as I indicated initially, it seems to me that one would pretty quickly > need to be taking up 90% of the 37 GtCO2/yr by your proposed approach—and > that is a lot of carbon to be taking up. Hence, I’ll stand by my earlier > statement that it will be hard for CDR/atmospheric and oceanic scrubbing to > make much of a difference with respect to slowing the rate of climate change > until emissions drop a lot. > > Mike > > > Msg from John Harte—combined into this thread. > > Mike, I think the truth is flanked by your's and Greg's statements. If we > were to reduce emissions starting immediately so that each year from here on > out we emit only about half current emissions, then for a decade or two, at > least, the current carbon sink would roughly equal emissions and the CO2 > level would be roughly constant, as Greg suggests. The concentration gradient > between air and sea would slowly shrink however and so in the longer run the > sink strength would diminish and emissions would have to be reduced further. > At a steady annual flow from air to sea of 15 - 20 Gt(CO2)/y, however, it > would take decades before there was an appreciable diminishment of that sink > flow. The real shorter-term danger I think is that soil warming and forest > dieback leading to terrestrial sources of CO2, along with possible CH4 > releases, all because of the warming associated with trying to keep a steady > 400 ppm of CO2, would necessitate much greater emissions reduction and the > sooner we achieve that the better. > > John Harte > Professor of Ecosystem Sciences > ERG/ESPM > 310 Barrows Hall > University of California > Berkeley, CA 94720 USA > [email protected] > > > On 1/25/15, 3:23 PM, "Greg Rau" <[email protected]> wrote: > >> I'm not necessarily advocating lowering air pCO2, but stabilizing pCO2 say >> at the present 400 uatms. If this is stable, how does additional ocean >> degassing ensue? Exactly how much CDR would be needed to achieve this, the >> resulting response of natural CDR and natural emissions, and the required >> time course of this I will leave to the modelers. Ditto for achieving >> stability via pure anthro emissions reduction. Obviously, some combination >> of these will, in my opinion, be needed to stabilize pCO2. Anthro emissions >> reduction would appear to have significant technological and policy >> awareness lead relative to CDR. I'm suggesting this needs to change, in case >> emissions reduction alone continues to fail to achieve its promise. >> >> As for reducing air pCO2, this already happens on an intra-annual basis >> thanks to natural CDR and in spite of ocean degassing: >> https://scripps.ucsd.edu/programs/keelingcurve/2013/10/23/the-annual-rise-in-co2-levels-has-begun/#more-940 >> Is it unthinkable that this decline couldn't be increased to some degree >> via human intervention? Wouldn't it be desirable/necessary to investigate >> this in the now likely event that current policies and actions have us >> blowing by the pCO2 "safety threshold" for decades if not centuries, or >> beyond if permafrost/clathrate degassing ensues? >> Greg >> >>> >>> >>> >>> >>> From: Mike MacCracken <[email protected]> >>> To: Greg Rau <[email protected]>; Geoengineering >>> <[email protected]> >>> Sent: Sunday, January 25, 2015 11:10 AM >>> Subject: Re: [geo] Energy Planning and Decarbonization Technology | The >>> Energy Collective >>> >>> >>> >>> Re: [geo] Energy Planning and Decarbonization Technology | The Energy >>> Collective >>> Hi Greg--The problem with your calculation is that if you were to take CO2 >>> out of the atmosphere, the ocean and biosphere would readjust to the lower >>> atmospheric concentration and return to the atmosphere that they have taken >>> up earlier when the original amount of CO2 was emitted. Thus, you really >>> have to figure out how to sequester 90+% of the 37 Gt CO2/yr that is >>> emitted—you don’t get to keep counting the 20 Gt CO2 taken up by the ocean >>> and the biosphere. >>> >>> Mike >>> >>> >>> On 1/25/15, 1:25 PM, "Greg Rau" <[email protected]> wrote: >>> >>>> Just to be clear, we currently emit 37.0 GT CO2/yr, yet in the short term >>>> only 17.5 Gt/yr remain in the atmosphere, the rest being removed by >>>> natural CDR (reviewed here: >>>> http://www.nature.com/nclimate/journal/v4/n10/full/nclimate2392.html ). So >>>> our net emissions is 17.5 Gt/yr. Cutting this by 90% via enhanced CDR >>>> alone would mean removing an additional 15.8 GT CO2/yr over and above the >>>> 19.5 Gt/yr already removed, a 81% increase in CDR. Is this sufficient to >>>> stabilize air pCO2 or lower pCO2? If the latter then we'd also have to >>>> contend with legacy CO2 degassing from the ocean. It should be easier to >>>> reduce emissions than increase CDR, but then how is that going? I'd say >>>> it's time to find out just how easy or hard additional CDR is, relative to >>>> the technical, economic and political difficulties of emissions reduction, >>>> and relative to the consequences if the latter strategy continues to >>>> seriously underperform. >>>> Greg >>>> >>>>> >>>>> >>>>> >>>>> >>>>> From: Mike MacCracken <[email protected]> >>>>> To: Greg Rau <[email protected]>; Geoengineering >>>>> <[email protected]> >>>>> Sent: Sunday, January 25, 2015 8:27 AM >>>>> Subject: Re: [geo] Energy Planning and Decarbonization Technology | The >>>>> Energy Collective >>>>> >>>>> >>>>> >>>> Re: [geo] Energy Planning and Decarbonization Technology | The Energy >>>> Collective >>>> Let me expand my quick description to be 90% cut in human-induced >>>> emissions (on top of all the natural sinks), so natural CDR does not count. >>>> >>>> And on the proposed removal industry, for $100 per ton of CO2, an awful >>>> lot could be done to replace fossil fuels with other sources of energy, or >>>> even better efficiency, a huge amount of which could be done for much >>>> less, if we’d try. So, nice that there is a CO2 removal approach as a >>>> backstop to what the cost of changing energy would be—basically, you are >>>> suggesting it should cost less than $100 per ton of CO2 to address the >>>> problem. With the new paper in Nature (lead author is a former intern that >>>> worked with me at the Climate Institute) that the social cost of CO2 is >>>> more than twice the cost of, then it makes huge economic sense to be >>>> addressing the problem. So, indeed, let’s get on with it—research plus >>>> actually dealing with the issue. >>>> >>>> Mike >>>> >>>> >>>> >>>> >>>> On 1/24/15, 1:40 PM, "Greg Rau" <[email protected]> wrote: >>>> >>>>> Mike, >>>>> If it takes "a 90% cut in CO2 to stop the rise in atmospheric >>>>> concentration", we are already more than half way there thanks to natural >>>>> CDR. About 55% of our CO2 emissions are mercifully removed from air via >>>>> biotic and abiotic processes. So just 35% to go? >>>>> As for "CDR replacing the fossil fuel industry", here's one way to do >>>>> that: http://www.pnas.org/content/110/25/10095.full , but low fossil >>>>> energy prices (or lack of sufficient C emissions surcharge) are unlikely >>>>> to make this happen. Certainly agree that we need all hands and ideas on >>>>> deck in order to stabilize air CO2. But for reasons that continue to >>>>> baffle me, that is not happening at the policy, decision making, and R&D >>>>> levels it needs to. >>>>> Greg >>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> From: Mike MacCracken <[email protected]> >>>>>> To: Geoengineering <[email protected]> >>>>>> Sent: Saturday, January 24, 2015 9:06 AM >>>>>> Subject: Re: [geo] Energy Planning and Decarbonization Technology | The >>>>>> Energy Collective >>>>>> >>>>>> >>>>>> >>>>>> Re: [geo] Energy Planning and Decarbonization Technology | The Energy >>>>>> Collective >>>>>> In terms of an overall strategy, it takes of order a 90% cut in CO2 >>>>>> emissions to stop the rise in the atmospheric concentration, and that >>>>>> has to happen to ultimately stabilize the climate (and it would be >>>>>> better to have the CO2 concentration headed down so we don’t get to the >>>>>> equilibrium warming for the peak concentration we reach (recalling we >>>>>> will be losing sulfate cooling). >>>>>> >>>>>> Thus, to really stop the warming, CDR in its many forms has to be at >>>>>> least as large as 90% of CO2 emissions (from fossil fuels and biospheric >>>>>> losses). That is a lot of carbon to be taking out of the system by >>>>>> putting olivine into the ocean, biochar, etc. at current global >>>>>> emissions levels (that are still growing). The greater the mitigation >>>>>> (reduction in fossil fuel emissions), the more effective CDR can be—what >>>>>> would really be nice is CDR replacing the fossil fuel industry so >>>>>> ultimately it is as large. I’d suggest this is why it is really >>>>>> important to always be mentioning the importance of all the other ways, >>>>>> in addition to CDR, to be cutting emissions—that is really critical. >>>>>> >>>>>> Mike >>>>>> >>>>>> >>>>>> On 1/24/15, 10:19 AM, "Stephen Salter" <[email protected]> wrote: >>>>>> >>>>>>> >>>>>>> Hi All >>>>>>> >>>>>>> Paragraph 2 mentions 'carbon negative' nuclear energy. The carbon >>>>>>> emissions from a complete, working nuclear power station are mainly >>>>>>> people driving to work. But digging, crushing and processing uranium >>>>>>> ore needs energy and releases carbon in inverse proportion to the ore >>>>>>> grade. There were some amazingly high grade ores, some once even at >>>>>>> the critical point for reaction, but these have been used. Analysis by >>>>>>> van Leeuwen concludes that the carbon advantage of present nuclear >>>>>>> technology over gas is about three but that the break-even point comes >>>>>>> when the ore grade drops to around 100 ppm. This could happen within >>>>>>> the life of plant planned now. >>>>>>> >>>>>>> As we do not know how to do waste disposal we cannot estimate its >>>>>>> carbon emissions. But just because we cannot calculate them does not >>>>>>> mean that they are zero. >>>>>>> >>>>>>> Stephen >>>>>>> >>>>>>> >>>>>>> >>>>>>> Emeritus Professor of Engineering Design. School of Engineering. >>>>>>> University of Edinburgh. Mayfield Road. Edinburgh EH9 3JL. Scotland >>>>>>> [email protected] Tel +44 (0)131 650 5704 Cell 07795 203 195 >>>>>>> WWW.see.ed.ac.uk/~shs <http://WWW.see.ed.ac.uk/~shs> YouTube Jamie >>>>>>> Taylor Power for Change >>>>>>> >>>>>>> On 24/01/2015 14:56, Andrew Lockley wrote: >>>>>>> >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Poster's note : none of this explains why there's any need for >>>>>>>> integration. Chucking olivine in the sea seems easier and cheaper than >>>>>>>> all. >>>>>>>> >>>>>>>> >>>>>>>> http://theenergycollective.com/noahdeich/2183871/3-ways-carbon-removal-can-help-unlock-promise-all-above-energy-strategy >>>>>>>> >>>>>>>> >>>>>>>> 3 Ways Carbon Removal can Help Unlock the Promise of an >>>>>>>> All-of-the-Above Energy Strategy >>>>>>>> >>>>>>>> >>>>>>>> January 24, 2015 >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> “We can’t have an energy strategy for the last century that traps us >>>>>>>> in the past. We need an energy strategy for the future – an >>>>>>>> all-of-the-above strategy for the 21st century that develops every >>>>>>>> source of American-made energy.”– President Barack Obama, March 15, >>>>>>>> 2012 >>>>>>>> >>>>>>>> >>>>>>>> An all-of-the-above energy strategy holds great potential to make our >>>>>>>> energy system more secure, inexpensive, and environmentally-friendly. >>>>>>>> Today’s approach to all-of-the-above, however, is missing a key piece: >>>>>>>> carbon dioxide removal (“CDR”). Here’s three reasons why CDR is >>>>>>>> critical for the success of an all-of-the-above energy strategy: >>>>>>>> >>>>>>>> >>>>>>>> 1. CDR helps unite renewable energy and fossil fuel proponents to >>>>>>>> advance carbon capture and storage (“CCS”) projects. Many renewable >>>>>>>> energy advocates view CCS as an expensive excuse to enable >>>>>>>> business-as-usual fossil fuel emissions. But biomass energy with CCS >>>>>>>> (bio-CCS) projects are essentially “renewable CCS” (previously viewed >>>>>>>> as an oxymoron), and could be critical for drawing down atmospheric >>>>>>>> carbon levels in the future. As a result, fossil CCS projects could >>>>>>>> provide a pathway to “renewable CCS” projects in the future. Because >>>>>>>> of the similarities in the carbon capture technology for fossil and >>>>>>>> bioenergy power plants, installing capture technology on fossil power >>>>>>>> plants today could help reduce technology and regulatory risk for >>>>>>>> bio-CCS projects in the future. What’s more, bio-CCS projects can >>>>>>>> share the infrastructure for transporting and storing CO2 with fossil >>>>>>>> CCS installations. Creating such a pathway to bio-CCS should be >>>>>>>> feasible through regulations that increase carbon prices and/or >>>>>>>> biomass co-firing mandates slowly over time, and could help unite >>>>>>>> renewable energy and CCS proponents to develop policies that enable >>>>>>>> the development of cost-effective CCS technology. >>>>>>>> >>>>>>>> >>>>>>>> 2. CDR bolsters the environmental case for nuclear power by enabling >>>>>>>> it to be carbon “negative”: Many environmental advocates say that >>>>>>>> low-carbon benefits of nuclear power are outweighed by the other >>>>>>>> environmental and safety concerns of nuclear projects. The development >>>>>>>> of advanced nuclear projects paired with direct air capture (“DAC”) >>>>>>>> devices, however, could tip the scales in nuclear’s favor. DAC systems >>>>>>>> that utilize the heat produced from nuclear power plants can benefit >>>>>>>> from this “free” source of energy to potentially sequester CO2 >>>>>>>> directly from the atmosphere cost-effectively. The ability for nuclear >>>>>>>> + DAC to provide competitively-priced, carbon-negative energy could >>>>>>>> help convince nuclear power’s skeptics to support further >>>>>>>> investigation into developing safe and environmentally-friendly >>>>>>>> advanced nuclear systems. >>>>>>>> >>>>>>>> >>>>>>>> 3. CDR helps enable a cost-effective transition to a decarbonized >>>>>>>> economy: Today, environmental advocates claim that prolonged use of >>>>>>>> fossil fuels is mutually exclusive with preventing climate change, and >>>>>>>> fossil fuel advocates bash renewables as not ready for “prime time” — >>>>>>>> i.e. unable to deliver the economic/development benefits of >>>>>>>> inexpensive fossil energy. To resolve this logjam, indirect methods of >>>>>>>> decarbonization — such as a portfolio of low-cost CDR solutions — >>>>>>>> could enable fossil companies both to meet steep emission reduction >>>>>>>> targets and provide low-cost fossil energy until direct >>>>>>>> decarbonization through renewable energy systems become more >>>>>>>> cost-competitive (especially in difficult to decarbonize areas such as >>>>>>>> long-haul trucking and aviation). >>>>>>>> >>>>>>>> >>>>>>>> Of course, discussion about the potential for CDR to enable an >>>>>>>> all-of-the-above energy strategy is moot unless we invest in >>>>>>>> developing a portfolio of CDR approaches. But if we do make this >>>>>>>> investment in CDR, an all-of-the-above energy strategy that delivers a >>>>>>>> diversified, low-cost, and low-carbon energy system stands a greater >>>>>>>> chance of becoming a reality. >>>>>>>> >>>>>>>> >>>>>>>> Noah Deich >>>>>>>> >>>>>>>> >>>>>>>> Noah Deich is a professional in the carbon removal field with six >>>>>>>> years of clean energy and sustainability consulting experience. Noah >>>>>>>> currently works part-time as a consultant for the Virgin Earth >>>>>>>> Challenge, is pursuing his MBA from the Haas School of Business at UC >>>>>>>> Berkeley, and writes a blog dedicated to carbon removal >>>>>>>> (carbonremoval.wordpress.com <http://carbonremoval.wordpress.com >>>>>>>> <http://carbonremoval.wordpress.com/> >>>>>>>> <http://carbonremoval.wordpress.com/> >>>>>>>> <http://carbonremoval.wordpress.com/> > ) >>>>>>>> >>>>>>>> >>>>>>>> -- >>>>>>>> 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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