Dear John, all As a coordinating lead author of IPCC AR5 WG1 (and someone how has done work on these topics) I’m surprised to read such comments.
> Blunder 1. IPCC has ignored the increasing loss of Arctic albedo, which is > already contributing the equivalent of 30 ppm CO2 to the radiative budget, > i.e. a quarter of the forcing from CO2. […] The first blunder is symptomatic > of IPCC's treatment of the Arctic sea ice, where they refuse to accept the > observations that it is in a death spiral, preferring to rely on models of > proven inadequacy which predict that the sea ice will last for decades. You > can read all about it in Peter Wadhams' new book "A Fairwell to Ice". The change in albedo is part of every climate model as snow cover and sea ice change. Indeed some many models show smaller Arctic sea ice decline than observed. But the natural variability is very large (e.g. Kay 2011, Swart 2015, Screen 2013, 2016). There is no reason why short term trends could simply be extrapolated, and the predictions by Peter Wadhams of sea ice disappearing by today have not happened so far (https://www.theguardian.com/environment/2012/sep/17/arctic-collapse-sea-ice, http://www.independent.co.uk/environment/climate-change/arctic-could-become-ice-free-for-first-time-in-more-than-100000-years-claims-leading-scientist-a7065781.html). Maybe the models are missing something, but it’s just as plausible (and in most scientist’s view more likely) that the models are largely consistent with observations within natural variability. Many studies have used observations to recalibrate and weight models, and even IPCC has explicitly made projections for Arctic sea ice based on those models that best reproduce various aspects of sea ice (section 12.4.6.1). All of these studies indicate that using observations point to a somewhat steeper decline of Arctic sea ice (Boe 2009, Massonnet 2012, Mahlstein 2012, Wang 2013, Notz 2016), but not a “death spiral”. I’m not downplaying the strong changes in the Arctic, but the science suggests a fairly linear (and reversible) relationship between Arctic sea ice and temperature with large variability superimposed. In my view they do not support a “death spiral”. >Blunder 2. IPCC has ignored the warming effect of accumulated CO2. They say >that global temperature rise will be halted when net CO2 emissions have fallen >to zero, ignoring the effect of accumulated CO2 and other forcing agents in >the atmosphere.[…] The second blunder can be illustrated by AR5 WG1 figure >6-40 attached and available here [1]. The red curves are supposed to show the >effect if net emissions were to suddenly fall to zero at 2050, when CO2 has >reached about 500 ppm. The temperature (red curve in bottom diagram) should >continue to rise as a result of the forcing from 500 ppm CO2; but instead the >temperature flattens off as if the accumulated CO2 ceased to have a warming >effect! Of course CO2 continues to have an effect, but as emissions are set to zero the atmospheric concentration and therefore forcing decrease. >It is absolutely astonishing and frightening that such a fundamental mistake >can be made. Where is the evidence for a fundamental mistake? >If we want to halt global warming at any particular temperature, then we need >to bring net forcing down to zero by the time that temperature has been >reached. No, that is simply wrong. The forcing has to decrease to compensate the slowly decreasing ocean heat uptake, but it does not have to be zero at any time to limit warming, not even in equilibrium. The global energy balance is Q=F-lambda*T where Q is heat uptake, F is forcing, lambda is the inverse of climate sensitivity and T is warming (see Knutti and Hegerl 2008 for example). If today F~=2.3 Wm-2 and Q~=0.9 Wm-2 and we want to keep T constant and Q=0 towards equilibrium then F needs to decrease to about 2.3-0.9=1.4 Wm-2 on the timescale on which the ocean warms (decades to centuries), but not zero. Climate is complex, but conservation of energy isn’t. IPCC WG1 chapter 12 has an long discussion of the difference concepts of commitment warming (section 12.5.2) with plenty of references from different models going back many decades. There is even an FAQ 12.3 discussing that, and it also does discuss non-CO2 forcings. There are models which show some warming after zero CO2 emissions, and others that show some cooling, but in general these concepts of commitment warming are well understood. IPCC isn’t perfect, but it’s probably the best reviewed document on climate, with hundreds of scientist contributing. It seems rather unlikely that it would contain “fundamental mistakes”, and in my view the claims you made here have no scientific basis. Best regards, Reto Knutti, ETH Zurich http://www.iac.ethz.ch/people/knuttir Swart, Neil C., John C. Fyfe, Ed Hawkins, Jennifer E. Kay, and Alexandra Jahn. 2015. “Influence of Internal Variability on Arctic Sea-Ice Trends.” Nature Climate Change 5 (2). Nature Publishing Group: 86–89. doi:10.1038/nclimate2483. Kay, Jennifer E., Marika M. Holland, and Alexandra Jahn. 2011. “Inter-Annual to Multi-Decadal Arctic Sea Ice Extent Trends in a Warming World.” Geophysical Research Letters 38 (15): 2–7. doi:10.1029/2011GL048008. Screen, James a., Clara Deser, Ian Simmonds, and Robert Tomas. 2013. “Atmospheric Impacts of Arctic Sea-Ice Loss, 1979–2009: Separating Forced Change from Atmospheric Internal Variability.” Climate Dynamics 43 (1–2): 333–44. doi:10.1007/s00382-013-1830-9. Screen, James A., and Jennifer A. Francis. 2016. “Contribution of Sea-Ice Loss to Arctic Amplification Is Regulated by Pacific Ocean Decadal Variability.” Nature Climate Change 6 (9): 856–60. doi:10.1038/nclimate3011. Boé, Julien, Alex Hall, and Xin Qu. 2009. “September Sea-Ice Cover in the Arctic Ocean Projected to Vanish by 2100.” Nature Geoscience 2 (5). Nature Publishing Group: 341–43. doi:10.1038/ngeo467. Mahlstein, Irina, and Reto Knutti. 2012. “September Arctic Sea Ice Predicted to Disappear near 2°C Global Warming above Present.” Journal of Geophysical Research 117 (D6): 1–11. doi:10.1029/2011JD016709. Notz, Dirk, and Julienne Stroeve. 2016. “Observed Arctic Sea-Ice Loss Directly Follows Anthropogenic CO2 Emission.” Science, November, 1–9. doi:10.1126/science.aag2345. Overland, James E., and Muyin Wang. 2013. “When Will the Summer Arctic Be Nearly Sea Ice Free?” Geophysical Research Letters 40 (10): 2097–2101. doi:10.1002/grl.50316. Massonnet, F., T. Fichefet, H. Goosse, C. M. Bitz, G. Philippon-Berthier, M. M. Holland, and P.-Y. Barriat. 2012. “Constraining Projections of Summer Arctic Sea Ice.” The Cryosphere 6 (6): 1383–94. doi:10.5194/tc-6-1383-2012. Knutti, Reto, and Gabriele C. Hegerl. 2008. “The Equilibrium Sensitivity of the Earth’s Temperature to Radiation Changes.” Nature Geoscience 1 (11): 735–43. doi:10.1038/ngeo337. From: [email protected] [mailto:[email protected]] On Behalf Of John Nissen Sent: Montag, 14. November 2016 16:06 To: David Lewis <[email protected]> Cc: geoengineering <[email protected]>; Kevin Anderson <[email protected]>; [email protected]; Greg Rau <[email protected]>; Peter Wadhams <[email protected]>; Kevin Lister <[email protected]>; Sev Clarke <[email protected]>; Alan Gadian <[email protected]> Subject: Re: [geo] Negative Emissions: Arrows in the Quiver, Life Preserver, and/or Moral Hazard? Dear David, I think Klaus et al have the voice of realism. Global warming is far more serious than we have been led to believe, and without several rapid interventions, we are heading for many degrees of global warming this century. IPCC are guilty of two colossal blunders in their projections of global warming. The effect has been to lull the international community into a false sense of security. Rapid interventions are now required to avoid a lethal combination of climate change, ocean acidification and rising sea levels. Here are the facts: Blunder 1. IPCC has ignored the increasing loss of Arctic albedo, which is already contributing the equivalent of 30 ppm CO2 to the radiative budget, i.e. a quarter of the forcing from CO2. Blunder 2. IPCC has ignored the warming effect of accumulated CO2. They say that global temperature rise will be halted when net CO2 emissions have fallen to zero, ignoring the effect of accumulated CO2 and other forcing agents in the atmosphere. The first blunder is symptomatic of IPCC's treatment of the Arctic sea ice, where they refuse to accept the observations that it is in a death spiral, preferring to rely on models of proven inadequacy which predict that the sea ice will last for decades. You can read all about it in Peter Wadhams' new book "A Fairwell to Ice". The second blunder can be illustrated by AR5 WG1 figure 6-40 attached and available here [1]. The red curves are supposed to show the effect if net emissions were to suddenly fall to zero at 2050, when CO2 has reached about 500 ppm. The temperature (red curve in bottom diagram) should continue to rise as a result of the forcing from 500 ppm CO2; but instead the temperature flattens off as if the accumulated CO2 ceased to have a warming effect! It is absolutely astonishing and frightening that such a fundamental mistake can be made. If we want to halt global warming at any particular temperature, then we need to bring net forcing down to zero by the time that temperature has been reached. This involves bringing all GHGs down to their pre-industrial level and restoring Arctic albedo, unless their residual heating (positive forcing) is counteracted by an equal amount of cooling (negative forcing), e.g. from aerosols. CDR has to suck CO2 out of the atmosphere faster than it is being emitted into the atmosphere, in order to bring the level down from over 400 ppm to pre-industrial 280 ppm. Methane emissions have to be suppressed (including fugitive emissions from coal, oil and gas extraction) in order to bring the level down from 1850 ppb to pre-industrial 750 ppb. The retreat of sea ice has to be halted and then Arctic albedo has to be restored to its level of at least thirty years ago. Thus our best chance to halt global warming is through CO2 emissions reduction (better than already committed) combined with several immediate and aggressive interventions: CDR, methane emissions reduction, and rapid cooling of the Arctic. As Klaus Lackner et al say in their comment, CDR is indeed like throwing a lifebelt to a drowning person. We need to start CDR as quickly as we can, to be as certain as we can be to save the planet. In parallel we must suppress methane and cool the Arctic before we lose any more albedo from snow and sea ice retreat. The ultimate objective must be to restore the Earth System to Holocene conditions of climate stability, ocean alkalinity and sea level constancy. Cheers, John [1] http://www.ipcc.ch/report/graphics/images/Assessment%20Reports/AR5%20-%20WG1/Chapter%2006/thumbnail/Fig6-40.jpg On Mon, Nov 14, 2016 at 4:55 PM, David Lewis <[email protected]<mailto:[email protected]>> wrote: Anderson could maintain his stance as a voice for realism while adding his voice to those calling for research into all forms of geoengineering. He could compare the cost of reducing emissions to the current cost of removing them from the atmosphere, call for a vigorous program of further research, then state that it is still his opinion that civilization needs to urgently and fundamentally transform its social, economic, and political relations if it wants to continue to exist. Moral: Do not ignore or downplay potentially useful actions, especially if you have the time and resources to carefully evaluate them. ________________________________ From: Greg Rau <[email protected]<mailto:[email protected]>> To: Geoengineering <[email protected]<mailto:[email protected]>> Sent: Friday, November 11, 2016 4:50 PM Subject: [geo] Negative Emissions: Arrows in the Quiver, Life Preserver, and/or Moral Hazard? -- 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 post to this group, send email to [email protected]<mailto:[email protected]>. Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout . http://science.sciencemag.org/content/354/6313/714.1 GR: Disclaimer - I was a co-signer. -- 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 post to this group, send email to [email protected]<mailto:[email protected]>. Visit this group at https://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]<mailto:[email protected]>. To post to this group, send email to [email protected]<mailto:[email protected]>. Visit this group at https://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 https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
