To start, I agree completely with the bottom line that we must do as much as possible as fast as possible. But my understanding of the carbon cycle is that the strength of the land and ocean sinks is driven by the cumulative amounts of carbon in the atmosphere, not the annual emissions. Thus, if emissions dropped to zero, the current sink strength will decline slowly. The result would be a multi-decadal period during which the land and ocean sink terms would be greater than the anthro additions, leading to a gradual decline in atmospheric carbon concentrations. Of course, we have not run this thought experiment in the real world and we might be surprised.
Sent from my iPad On Jul 11, 2019, at 8:16 AM, Kevin Lister <kevin.lister2...@gmail.com<mailto:kevin.lister2...@gmail.com>> wrote: Hi Doug et al, On point 2 below, "But people (well, mostly John Nissen) keep making the argument you’re making on the assumption that zero emissions = constant concentrations, which is simply not true." Let me come to John's defence. 1. The correlation between cumulative emissions and atmospheric CO2 is effectively perfect with r^2=0.999, which is quite extraordinary. This strongly implies that all the CO2 emissions from fossil fuel burning are still in the ecosystem. That obviously doesn't imply that all the CO2 from fossil fuel burning is in the atmosphere, but it does reasonably lead to the conclusion that all interconnected carbon sinks are filling equally, such as the the ocean surface, soils, and the atmosphere. Given that this perfect correlation has been unaffected by the rate of emissions, then it would further imply that the rate of permanent sequestration must been extremely slow, and effectively negligible compared to fossil fuel emissions. 2. The immediate upwards rise of atmospheric CO2 at the start of the industrial revolution further indicates that the rate of permanent CO2 sequestration is very slow. At this time emissions were a fraction of what they are today and the ecosystem was in a considerably more healthy state. 3. The saw tooth profile of the Vostok Ice Core shows the rate of permanent carbon sequestration to be slow and averaged over the last 4 inter-glacial cycles it is around 6.7E-4ppm/year, which is negligible compared with the rate of increase. 4. Even if zero carbon led to CO2 concentration reductions, the cooling effect would be too small due to the logarithmic relation between forcing and concentration. So the evidence would support that zero emissions=constant concentrations, at least on for any timescale that matters, The things that matter to determine the timescale are the initiation of climate tipping points and points of irreversibly, beyond which climate and ecosystem recovery becomes impossible even with SRM interventions. We have certainly past the points of initiation of tipping points, and will soon be past the points of irreversibly. So it seems to me that from a pragmatic risk management perspective, we should assume that zero carbon=constant emissions, and plan accordingly, which means identifying interventions in the climate system that can lead to cooling and CDR, as well as forcing much deeper cuts in anthropocentric emissions. Kevin On Thu, Jul 11, 2019 at 11:22 AM Douglas MacMartin <dgm...@cornell.edu<mailto:dgm...@cornell.edu>> wrote: 1. So agree with you that if you want to accurately characterize the Paris agreement on this plot, the line should corresponding to that should only go to 2030 and then stop. That is, not what you drew. Also agree that I was wrong in my interpretation of what you meant by that line; I was misled by the fact that you’d continued the line out towards the right-hand end of the plot rather than ending it in 2030 like you intended. 2. Agree that there is uncertainty associated with this, and uncertainty associated with nonlinearity in particular. I generally go back to Cao and Caldeira 2010, https://iopscience.iop.org/article/10.1088/1748-9326/5/2/024011/pdf, simply because Figure 1 has the nicest plot of the effect, but UVic is admittedly an old model with a lot missing and a questionable carbon cycle… but there is quite a bit of content on this in IPCC reports that would be good to digest before ignoring (that is, broadly the same behaviour is seen in current models, though again, I agree that there is potentially important physics missing from those models). But people (well, mostly John Nissen) keep making the argument you’re making on the assumption that zero emissions = constant concentrations, which is simply not true. 3. I think we agree that the choice is non-obvious, but I personally don’t think it is likely that <280ppm is going to be optimal, so I still don’t think it is particularly disingenuous to draw the line as it was. (Besides, the axis was climate effects, presumably relative to some baseline, and if that baseline is preindustrial, then going below 280ppm is likely to increase climate damages in the opposite direction… but agree that I don’t know that, and that it would be wonderful to ever be in a situation where that question matters.) 4. I would never use the word “assertion” with regards to a schematic figure like that… though as someone who uses (my own version) of this diagram frequently, I agree with you that when I talk about it I should be a bit more careful with regards to how I talk about where the SRM line goes. (And yes, John’s napkin is the first I know of that diagram, I don’t know what paper that specific version came from, it looks nearly identical to the one that I typically use, but with different fonts. I think I more or less copied the version I use from one that David Keith was using, so it is hardly surprising that plenty of us have our own independent but very similar versions.) From: Robert Tulip <rtulip2...@yahoo.com.au<mailto:rtulip2...@yahoo.com.au>> Sent: Wednesday, July 10, 2019 9:35 PM To: Douglas MacMartin <dgm...@cornell.edu<mailto:dgm...@cornell.edu>>; Andrew Lockley <andrew.lock...@gmail.com<mailto:andrew.lock...@gmail.com>> Cc: Stephen Salter <s.sal...@ed.ac.uk<mailto:s.sal...@ed.ac.uk>>; geoengineering <geoengineering@googlegroups.com<mailto:geoengineering@googlegroups.com>> Subject: Re: [geo] RE: [CDR] blog 28, Elon Musk vs regenerative development // Elon Musk vs le développement de régénération Response to comments from Doug MacMartin and Andrew Lockley “1. Given that the Paris agreement commitments don’t actually tell you what’s going to happen towards even the middle of the century, drawing any line corresponding to those commitments is a guess, but regardless, it seems pretty remarkable to assert that no-one will *ever* cut emissions beyond what was agreed upon in Paris – that’s your hypothesis, and doesn’t reflect an “inaccurate” diagram.” • Sorry Doug, but you completely miss the point. Under the Paris Accord, <~WRD147.jpg>Nationally Determined Contributions<https://unfccc.int/process-and-meetings/the-paris-agreement/nationally-determined-contributions-ndcs> have been made to 2030. These indicate a cut of <10% in annual emission growth by 2030, from about 60 GTCO2e under BAU to 56.2 GT <~WRD147.jpg>(2016 report page 9)<https://unfccc.int/sites/default/files/resource/docs/2016/cop22/eng/02.pdf>, and still way above the current level. Including that in the chart as I suggested would accurately reflect the marginal impact of current climate policy. It does not in any way imply that emission reduction could not be more than has been already agreed under Paris, as shown with the “aggressive” line on the chart. It might ratchet up, and economic forces might increase the cut to a still marginal 20%, but seeing the political reaction to efforts to make energy more expensive I am not holding my breath for more aggressive emission cuts. “2. Mostly wrong… actually, if net emissions are zero, then once you’ve paid the price for removing tropospheric aerosol cooling, the residual committed warming is mostly balanced by the residual drawdown of CO2… obviously not going to be exact, and depends a lot on whether there are nonlinear tipping points, but zero emissions is NOT the same thing as constant-concentration commitment, so to first order the original diagram is more accurate than your amended one.” • Firstly, the line was not about “net zero emissions” (which include CDR) but about emission reduction alone, so your “balancing” argument is not relevant to what the graph asserts. Further to that, I would like to see the source for your argument about balancing. Recent commentary I have read (eg from Kevin Lister) says the amplifying feedbacks from committed warming, seen in events such as the melting of the poles and burning of forests, mean that aggressive emission reduction alone cannot possibly cause the planetary temperature to flatline as you argue here. Given the sensitivity to initial conditions seen in the orbital drivers of long term climate, your hypothesis of balancing by residual drawdown looks highly unlikely and risky when we leave in place a massive driver of 700 GT of extra carbon in the air with no CDR. “3. The version of this that John posted has CDR continuing all the way down towards zero but not below it, your version goes below zero effects, so I’m not clear on what your point is here… Obvoiusly, that’s ultimately a choice where one stops.” • No, the choice of where to stop the line on CDR climate effect is far from obvious. There is a widespread false assumption in much climate literature, including from IPCC, that net zero emissions constitutes a hard floor. This assumption is reflected in how the original diagram shows a flattening as CDR effect approaches net zero climate effect. Showing CDR effect extending below zero on the Y axis reflects the need to work out how to remove enough carbon to get back to 280 ppm, to restore Holocene planetary stability. Assuming the X time axis is linear here means that CDR objective requires the line going well below the zero point on the Y effect axis. The misleading effect of the portrayal in the original diagram is to increase the imagined benefit of emission reduction and reduce the potential effect of carbon removal. “4. Sure… again, that’s a choice, that doesn’t reflect an inaccurate diagram, simply that the diagram doesn’t show the full range of possible policy options.” • But the problem is that the diagram falsely maximises the effect of currently promoted policies around decarbonisation while minimising the potential of geoengineering. That policy bias is reflected in this assertion in the diagram that SRM could not reduce climate effect. “5. Well, unclear given that there are no units or scales on the qualitative y-axis. Though RCP8.5, which is generally what people think of as BAU, does indeed result in roughly linear increase in temperature over time. Of course, the relationship between “effects” and temperature aren’t clear.” • The difference between exponential and linear effects under BAU is minor, even though an exponential line showing amplified feedback would better emphasise the catastrophic risk. Happy to focus on the other lines which appear to have major politically inspired material errors. On Andrew Lockley’s comments, <~WRD147.jpg>Shepherd’s Napkin Diagram<http://jgshepherd.com/wp-content/uploads/2011/01/Napkin-diagram.pdf> shows a rough sketch that I would have hoped could have been made more accurate over the decade since it was published. Unfortunately, it looks like the updated version of the Shepherd diagram reflects the ongoing domination of politics over science within climate advocacy, so it has not been properly revised to reflect accurate scientific information. Robert Tulip On Thursday, 11 July 2019, 02:24:42 am AEST, Andrew Lockley <andrew.lock...@gmail.com<mailto:andrew.lock...@gmail.com>> wrote: To give credit where credit's due, this was originally Shepherds famous napkin diagram. The srm line has been adjusted somewhat, however. I don't think that Doug's claims regarding Paris Commitments not conceivably being exceeded is supported empirically. Swansons law suggests very steep falls in the cost of energy by mid century, perhaps low single figure percentages of current costs. It would be implausible if large-scale use of fossil fuels would continue when renewable energy was one or two orders of magnitude cheaper On Wed, 10 Jul 2019, 17:12 Douglas MacMartin, <dgm...@cornell.edu<mailto:dgm...@cornell.edu>> wrote: Um… 1. Given that the Paris agreement commitments don’t actually tell you what’s going to happen towards even the middle of the century, drawing any line corresponding to those commitments is a guess, but regardless, it seems pretty remarkable to assert that no-one will *ever* cut emissions beyond what was agreed upon in Paris – that’s your hypothesis, and doesn’t reflect an “inaccurate” diagram. 2. Mostly wrong… actually, if net emissions are zero, then once you’ve paid the price for removing tropospheric aerosol cooling, the residual committed warming is mostly balanced by the residual drawdown of CO2… obviously not going to be exact, and depends a lot on whether there are nonlinear tipping points, but zero emissions is NOT the same thing as constant-concentration commitment, so to first order the original diagram is more accurate than your amended one. 3. The version of this that John posted has CDR continuing all the way down towards zero but not below it, your version goes below zero effects, so I’m not clear on what your point is here… Obvoiusly, that’s ultimately a choice where one stops. 4. Sure… again, that’s a choice, that doesn’t reflect an inaccurate diagram, simply that the diagram doesn’t show the full range of possible policy options. 5. Well, unclear given that there are no units or scales on the qualitative y-axis. Though RCP8.5, which is generally what people think of as BAU, does indeed result in roughly linear increase in temperature over time. Of course, the relationship between “effects” and temperature aren’t clear. Bottom line, it is completely inaccurate for you to refer to this conceptual diagram as being inaccurate or containing major errors. It is perfectly accurate to observe that none of the lines on the diagram are immutable. But given that there are no units, that’s hardly a criticism… From: 'Robert Tulip' via geoengineering <geoengineering@googlegroups.com<mailto:geoengineering@googlegroups.com>> Sent: Wednesday, July 10, 2019 8:21 AM To: geoengineering@googlegroups.com<mailto:geoengineering@googlegroups.com>; s.sal...@ed.ac.uk<mailto:s.sal...@ed.ac.uk> Subject: Re: [geo] RE: [CDR] blog 28, Elon Musk vs regenerative development // Elon Musk vs le développement de régénération Further to the needed corrections mentioned by John Gorman, Stephen Salter correctly points out that this diagram is inaccurate. It actually embeds a series of major myths in climate politics. I read Error! Filename not specified.<~WRD147.jpg>Benoit Lambert's link <https://cologie.wordpress.com/2019/07/09/elon-musk-vs-regenerative-development-elon-musk-vs-le-developpement-de-regeneration-french-below-en-francais-plus-bas/> but did not find the chart there. Here is a revised version of the chart. It shows that every line of the previous version contains major error with strong potential to mislead decision makers and the public. 1. Full implementation of current Paris commitments (added) would only have small marginal effect on Business as usual, 2. Aggressive emission cuts do nothing about committed warming from past emissions, so do not flatline the climate effect 3. CO2 removal continues below the farcical imaginary floor of zero effect 4. Solar radiation management can produce net negative radiative forcing. 5. The BAU line (not changed here) should show ongoing exponential growth rather than the shown linear increase. Robert Tulip Error! Filename not specified. On Wednesday, 10 July 2019, 07:46:59 pm AEST, Stephen Salter <s.sal...@ed.ac.uk<mailto:s.sal...@ed.ac.uk>> wrote: Hi All Zero emissions do not immediately mean zero temperature rises, especially if we have passed tipping points. Stephen Emeritus Professor of Engineering Design. School of Engineering, University of Edinburgh, Mayfield Road, Edinburgh EH9 3DW, Scotland s.sal...@ed.ac.uk<mailto:s.sal...@ed.ac.uk>, Tel +44 (0)131 650 5704, Cell 07795 203 195, Error! Filename not specified.<~WRD147.jpg>WWW.homepages.ed.ac.uk/shs<http://WWW.homepages.ed.ac.uk/shs>, YouTube Jamie Taylor Power for Change <~WRD147.jpg> Index of /shs On 10/07/2019 09:35, john gorman wrote: This diagram from the paper says it all in my opinion, and simply!! With, of course some variation in angles. Eg SRM could be angled down and I don’t believe cutting emissions will ever result in zero emissions. Good realistic paper! 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