Mike, you wrote: "Basically, the question is the extent to which these fluxes are driven by the concentration gradient created by the current year's emissions versus by the gradients created by past emissions.” That is is indeed the critical issue.
I have played around with a number of very simple box models to try to see what is happening. One such model consists of three boxes, with carbonate chemistry governing the aqueous equilibria. The boxes are the atmosphere, the mixed layer, and the deep ocean. It is not difficult to reproduce observations, including the amount of carbon that has already made its way to the deep ocean (recent observations suggest that carbon removed from the atmosphere has made its way down to ~ 1500 m, as has heat). Or one can model it as a two box system, just atmosphere and mixed layer, and then it is difficult to explain observations. Or one can lump the atmosphere and the mixed layer, and include the deep ocean as a second box, and that works fairly well. It seems to me that the slow time scale of mixing with the deep ocean is important and it appears to be the degree of chemical disequilibrium between the mixed layer and the deep ocean that drives the sink strength. If true, that implies that this years emissions are not the driver: the degree of disequilibrium between atm/mixed layer and the deep ocean is what matters. As you say, the atmosphere and mixed layer mix rapidly. I don’t have the capability to examine this within an oceanic model as detailed as those in some current GCMs, but the folks that run those models could/should be providing answers. Stay well, John John Harte Professor of the Graduate School Ecosystem Sciences ERG/ESPM University of California Berkeley, CA 94720 [email protected] > On Aug 12, 2021, at 2:08 PM, Michael MacCracken <[email protected]> wrote: > > Hi John--I've heard arguments both ways on this (e.g., Susan Solomon et al. > some years ago in Science; she worked with CO2e and I think used the CO2 > decay times, and had a very long tail; I've heard, I think it was, Steve > Pacala and Steve Hamburg make the same point you are--namely the fluxes would > continue for a while and I think they suggest the CO2 concentration would get > pulled down by about 50 ppm) and am wondering what the resolution is on this > (I've yet to read the IPCC relevant chapter on this). > > Basically, the question is the extent to which these fluxes are driven by the > concentration gradient created by the current year's emissions versus by the > gradients created by past emissions. For the atmosphere to the wind-mixed > upper ocean, the lag time I think is pretty short (1-2 years), but then from > the upper ocean to deep ocean may well be based mainly on gradient created by > past emissions, so it may persist for a while, but that flux is pretty small, > so emissions would need to get below the value of that flux to start to pull > things down. > > For atmosphere to the terrestrial biosphere, ignoring the return flux due to > fire, don't experiments like the FACE studies show that higher CO2 stimulates > additional growth for a few years and then starts to tail off, so does not > higher uptake stop pretty fast if there is no longer a gradient, etc. > > Is there a good well-documented resolution about this where theory and models > and observations agree what happens if one basically heads down toward zero > emissions by 2050 or so? > > Mike MacCracken > > > > On 8/12/21 4:46 PM, John Harte wrote: >> Kevin, you write: "Finally, and as you point out, carbon removal will be >> slow. The natural rate of removal is so slow as to not be measurable against >> CO2 emissions”. >> >> The current rate of removal of atmospheric carbon dioxide by natural marine >> and terrestrial processes is about 5 Gt(C)/year, which is about half of >> current annual anthropogenic emissions. >> >> That hardly seems to be unmeasurably slow! >> >> Were we to cease emissions today those natural sinks would persist but with >> diminishing strength in the future as the atmospheric level draws down. The >> sinks will not get the atmosphere down to a pre-industrial CO2 level of >> course, but they will nevertheless make a big difference. >> >> Among the most important things we can do is to stop degrading those natural >> sinks … protecting them is cheaper, would accomplish more than engineering >> artificial sinks, and would also provide numerous co-benefits. >> >> >> John Harte >> Professor of the Graduate School >> Ecosystem Sciences >> ERG/ESPM >> University of California >> Berkeley, CA 94720 >> [email protected] <mailto:[email protected]> >> >> >> >> >> >> >> >> >> >>> On Aug 12, 2021, at 5:01 AM, Kevin Lister <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> To answer Robert's comments on not seeing a downside to his proposal, and >>> in the immortal intellectual framework of a previous Secretary of Defence: >>> >>> There are known knowns, these are: >>> >>> >>> If you are dropping wind turbines out of a plane, then best guess is that >>> these would have a maximum power output of 2kW, or thereabouts. If they >>> successfully land and penetrate the ice and start pumping, and the water >>> forms a volcano shaped dome, with an inclination angle of 0.1 deg, then it >>> will take a approximately 161 days to grow a cone that is 3 meters high at >>> the pump, and it will have a radius of 1.7km. It would then take about >>> 107,000 of these to cover the ice sheet. That's a lot and probably far >>> more than all the planes of the US strategic deployment force can deliver >>> at the beginning of winter. Even if this is successful, a significant >>> number will be released from the edge of the ice in summer, say 10%, so >>> approximately 10,000 will float around in the ocean. >>> >>> Then there are known unknowns, these are: >>> >>> You do not know the angle that the water will settle on the ice, >>> You do not know what shape the ice will form around the pump, it is likely >>> to be a more complex and irregular doughnut shape. The mathematics behind >>> this is extremely complicated, and after about a year's effort I managed >>> only a partial solution before giving up. >>> You do not know what effect the continual heat flow from the subsurface >>> water being pumped onto the existing ice surface will have. In extremis, >>> the pumps could cause the ice adjacent to them to melt so all they end up >>> doing is pumping water into water. >>> Even if there are solutions to all of these, there is the practical >>> engineering matter of establishing the reliability of the pumps, especially >>> when they are to operate in the Arctic winter which is both cold, dark and >>> inaccessible. >>> >>> Then there are the unknown unknowns, these are: >>> >>> With the heat flow into the Arctic from the lower latitudes, then getting >>> reliable and consistent ice formation, even in the depths of winter, may no >>> longer be possible. >>> Ice formed on the surface of existing ice is of a totally different >>> structure to ice naturally formed by freezing downwards from the existing >>> ice. This new ice may have a structure more like glass and be of low >>> albedo, so in the summer it could act as a miniature greenhouse on the >>> existing ice, which is also being warmed from below, thus accelerating the >>> loss of existing ice when it is needed the most. This would be the worst >>> case scenario. We prevent heat release in the winter and minimise albedo in >>> the summer. >>> It is now as big an issue to release heat from the planet as it is to stop >>> more heat coming in. Given that the Arctic sea ice is now fatally doomed, >>> an alternative is to accept this and smash up the remaining ice in the >>> winter with icebreakers to allow the most rapid release of heat to space, >>> at an estimated rate ~500W/m^2 >>> >>> This is not to say that we should not increase planetary albedo and find >>> ways to release heat. We clearly must do it. I maintain that the safe >>> temperature rise is less than 0.5degC above baseline, which we passed >>> through in 1980. But we should be under no illusions that this is going to >>> be simple and absent of scientific and engineering risks. >>> >>> Finally, and as you point out, carbon removal will be slow. The natural >>> rate of removal is so slow as to not be measurable against CO2 emissions >>> and the paleoclimate records that the AR6 is now taking more notice of >>> indicates it will take about 250k years for CO2 to fall back to safe >>> levels. So, as well as exploring all viable albedo and heat releasing >>> mechanisms, we must immediately and simultaneously find ways to >>> decarbonise. >>> >>> Kevin >>> >>> >>> >>> >>> >>> >>> On Wed, Aug 11, 2021 at 12:16 PM 'Robert Tulip' via geoengineering >>> <[email protected] <mailto:[email protected]>> >>> wrote: >>> I thought it was pretty bad that the IPCC report >>> <https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf> >>> states as its headline B.1 finding that "Global warming of 1.5°C and 2°C >>> will be exceeded during the 21st century unless deep reductions in CO2 and >>> other greenhouse gas emissions occur in the coming decades." >>> >>> It should rather state "Global warming of 1.5°C and 2°C will be exceeded >>> during the 21st century even if deep reductions in CO2 and other greenhouse >>> gas emissions occur in the coming decades." (my bold) >>> >>> As the NOAA AGGI report <https://gml.noaa.gov/aggi/> states, CO2 >>> equivalents are now above 500 ppm. Emission reduction, technically defined, >>> only reduces the future addition of GHGs to the system, and does nothing to >>> remove the committed warming from past emissions. Leading scientists (eg >>> Eelco Rohling) think past emissions already commit the planet to 2°C. >>> >>> Even a major program of carbon conversion, transforming CO2 into useful >>> commodities such as soil and fabric, would do nothing to stop the >>> escalation of extreme weather this decade. Carbon removal is too small and >>> slow, despite having orders of magnitude greater potential cooling impact >>> than decarbonisation of the world economy. >>> >>> My view is the only immediate solution is to brighten the planet. Albedo >>> enhancement should start by pumping sea water onto the Arctic sea ice in >>> winter to freeze and reduce the summer melt using wind energy (diagram >>> attached). Marine cloud brightening is the next best option, followed by >>> areas that need considerably more impact research such as stratospheric >>> aerosol injection and iron salt aerosol. >>> >>> It is a disgrace that the IPCC seems to have entirely written off this >>> whole area of response, with no scientific reasoning as to why. >>> >>> >>> I understand that people find climate intervention for planetary >>> restoration a rather mind-boggling idea and would prefer it were not >>> needed. The problem is that extreme weather is steadily getting worse, and >>> cutting emissions through the energy transition can do nothing to stop it. >>> The overall issue is to define a scientific response to climate policy. >>> That means relying on evidence to define the most safe and effective >>> methods to support ongoing climate stability. Sadly AR6 squibbed that >>> challenge. >>> >>> Much of the public policy relies on other factors as well as science. >>> Notably this is about public perceptions rather than empirical assessment. >>> But that means the climate activist community will no longer be able to use >>> the mantra "the science says" to oppose geoengineering, as Michael Mann and >>> Bill McKibben and others now do. >>> >>> I think the factors that could change public opinion quite quickly include >>> the idea that immediate action to refreeze the Arctic is essential to >>> maintain stability of main ocean currents. I was very perturbed to see the >>> report last week on the slowing down of the AMOC Atlantic Meridional >>> Overturning Circulation >>> <https://www.theguardian.com/environment/2021/aug/05/climate-crisis-scientists-spot-warning-signs-of-gulf-stream-collapse> >>> and Gulf Stream collapse, with potential disasters for the world economy >>> and ecology. >>> >>> The linked press report suggested that decarbonising the economy is "the >>> only thing to do" to prevent the AMOC from stopping. That is an absurdly >>> unscientific opinion. It just fails to see that such natural processes >>> require action at orders of magnitude bigger scale than the marginal effect >>> of slowing down how much carbon we add to the air. >>> >>> If steps were taken to fully refreeze the Arctic Ocean, perhaps with the >>> quid pro quo of including transpolar shipping canals >>> <https://en.wikipedia.org/wiki/Transpolar_Sea_Route>through the ice, the >>> scale would be big enough to stop the dangerous looming tipping points of >>> accelerating feedback warming. Alongside AMOC, big problems such as polar >>> methane release, wandering of the jet stream and melting of the Greenland >>> Ice Sheet are also well beyond what decarbonisation can prevent. >>> >>> I really don't see any downside to such a freezing proposal, which should >>> be an Apollo-type world peace project led by the G20. The climate activist >>> community sees it as enabling a slower transition to >>> renewables, but surely buying time in this way is entirely a good >>> thing if it means we actually stabilise the climate? >>> >>> >>> Robert Tulip >>> >>> >>> From: [email protected] >>> <mailto:[email protected]> >>> <[email protected] >>> <mailto:[email protected]>> On Behalf Of Robert Cormia >>> Sent: Tuesday, 10 August 2021 4:32 AM >>> To: chris.vivian2 <[email protected] >>> <mailto:[email protected]>> >>> Cc: Carbon Dioxide Removal <[email protected] >>> <mailto:[email protected]>> >>> Subject: Re: [CDR] IPCC AR6 Summary for Policymakers >>> >>> >>> It took decades to get the public's attention about the clear and present >>> danger of climate change, through extreme weather events, historic fires, >>> and sea level rise. CDR is entering the dialog, slowly, it >>> needs to accelerate. Newscasters could add a simple soundbite "net >>> zero emissions and CO2 removal" as strategies, not just "clean energy and >>> electric cars" How do we gain the public's awareness, much less attention, >>> that putting a speed brake on emissions requires CDR, and restoring energy >>> balance (addressing energy imbalance) is our best potential/feasible >>> solution? >>> >>> >>> -rdc >>> >>> >>> On Mon, Aug 9, 2021 at 2:48 AM 'chris.vivian2' via Carbon Dioxide Removal >>> <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> In the IPCC AR6 Summary for Policymakers published today, see sections >>> D.1.4 to D.1.6 on page 40 where it mentions CDR - >>> https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf >>> <https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf>. >>> >>> Chris >>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "Carbon Dioxide Removal" group. >>> To unsubscribe from this group and stop receiving emails from it, send an >>> email to [email protected] >>> <mailto:[email protected]>. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/CarbonDioxideRemoval/d2ad5678-cf60-4af2-8968-3233344509f5n%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/CarbonDioxideRemoval/d2ad5678-cf60-4af2-8968-3233344509f5n%40googlegroups.com?utm_medium=email&utm_source=footer>. >>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "Carbon Dioxide Removal" group. >>> To unsubscribe from this group and stop receiving emails from it, send an >>> email to [email protected] >>> <mailto:[email protected]>. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/CarbonDioxideRemoval/CA%2B-rYQEG6iTG9qVC3GD-H5n6JdCBP%3Dwe3T24P-%2BUz6BR3E%2BhNg%40mail.gmail.com >>> >>> <https://groups.google.com/d/msgid/CarbonDioxideRemoval/CA%2B-rYQEG6iTG9qVC3GD-H5n6JdCBP%3Dwe3T24P-%2BUz6BR3E%2BhNg%40mail.gmail.com?utm_medium=email&utm_source=footer>. >>> >>> >>> -- >>> 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] >>> <mailto:[email protected]>. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/geoengineering/012c01d78ea2%2457f06f20%2407d14d60%24%40yahoo.com.au >>> >>> <https://groups.google.com/d/msgid/geoengineering/012c01d78ea2%2457f06f20%2407d14d60%24%40yahoo.com.au?utm_medium=email&utm_source=footer>. >>> >>> -- >>> 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] >>> <mailto:[email protected]>. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/geoengineering/CAE%3DUiezcG6_KoUsZMQN4jGfV1MA4EEVmmn_L_%2BHjqq3P6bok1g%40mail.gmail.com >>> >>> <https://groups.google.com/d/msgid/geoengineering/CAE%3DUiezcG6_KoUsZMQN4jGfV1MA4EEVmmn_L_%2BHjqq3P6bok1g%40mail.gmail.com?utm_medium=email&utm_source=footer>. >> >> -- >> 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] >> <mailto:[email protected]>. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/geoengineering/F676A5E0-67CA-4F55-BF32-7162310577B9%40berkeley.edu >> >> <https://groups.google.com/d/msgid/geoengineering/F676A5E0-67CA-4F55-BF32-7162310577B9%40berkeley.edu?utm_medium=email&utm_source=footer>. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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