Yes, this clarifies the matter. When the commitment to various future temperatures is spoken of, we are talking about temperatures reached at equilibrium. Today's CO2 concentration (along with other GHGs) if maintained permanently at today's levels, would result in equilibrium temperature increases substantially above what has been measured to date. If all human-caused GHG emissions were ceased today, natural sinks would gradually bring down today's concentrations and would result in lower equilibrium temperature increases than the constant concentration scenario. Since we are not going to cease all human-caused emissions immediately we are certainly on a path to temperature increases above those experienced to date.
The scenarios that Meinshausen and others have modeled, estimate the probabilities of exceeding various future equilibrium temperatures, given various future emissions paths and including removals by natural sinks. They show how rapid emission reduction paths can increase the probability of staying below various equilibrium temperature increases. So it is not twaddle technically to assert there is still a meaningful chance of not exceeding 2 degrees equilibrium temperature increase, assuming a rapid enough emission reduction path starting now. To say that does not conflict with the point that if geoengineering approaches could be deployed fast enough and at large enough scales and were successful, that the future equilibrium temperature increase could be lower than without. My own view is that we cannot argue today that we will not need geoengineering approaches, since that need is a function of how long it takes before we shift from increasing emissions to decreasing emissions. But at the same time, I believe it is premature to argue that we must begin to deploy massive SRM geoengineering approaches now without having more complete research on the potential negative consequences. Intensifying current research programs certainly makes sense as an intellectual proposition. They difficulties emerge when the context includes arguments that other programs must be cut and if politicians hide behind geoengineering research to rationalize their opposition to meaningful mitigation. These are not arguments against calls for more geoengineering research; just an attempt to describe why there is hesitation. ________________________________ From: Charles H. Greene [[email protected]] Sent: Sunday, March 16, 2014 5:02 PM To: Hawkins, Dave Subject: Re: [geo] Friends of the earth March 2014 advance briefing on AR5 Working Group 3 report Hi John and David: Please note that there is no inconsistency in what either of you is talking about. We are at 398 ppm today, and if the concentration stays at that level, then we will very likely exceed 2 degrees C. However, if we were to stop CO2 emissions immediately, then the uptake of CO2 by the natural sinks would bring us below 350 ppm by the end of the century, and we would most likely not exceed 2 degrees C. As we continue to emit CO2 into the atmosphere. we exceed the capacity of the natural sinks to remove the current excess. Note that when we talk about committed warming or "warming in the pipeline", this natural uptake is included. That is why even though we are currently at 398 ppm, our committed warming does not exceed 2 degrees C yet. Perhaps the first good discussion of this can be found in the following paper: Hansen, J et al. Target atmospheric CO2: where should humanity aim? Open Atmospheric Science Journal 2, 217-231 (2008). Cheers, Chuck Greene On Mar 16, 2014, at 3:19 AM, Hawkins, Dave <[email protected]<mailto:[email protected]>> wrote: John, You say-- the level of CO2 in the atmosphere has to be reduced if the world is to have any chance of keeping below 2 degrees C warming. If you are referring to today's level of CO2 in the atmosphere, what paper(s) can you point to that support this conclusion? As for the FOE comments about geoengineering, I think it is worth noting that FOE says it opposes only one form of geoengineering, SRM, and appears to be primarily concerned about one form of SRM, stratospheric particle injection. David Sent from my iPad On Mar 16, 2014, at 4:50 AM, "John Nissen" <[email protected]<mailto:[email protected]><mailto:[email protected]>> wrote: Hi all, FoE says the WG2 report on climate impacts will be published on March 29th and the WG3 report on "pathways to avoid dangerous climate change" will be published on April 11th. To quote from the WG3 summary by FoE: "It is still possible to reduce global carbon pollution fast enough and deep enough to make 2 degrees of global warming unlikely and provide a small chance of avoiding 1.5 degrees of warming, but only by making far-reaching socio-economic changes." This is complete twaddle and wishful thinking by people whose solidarity is clearly with the "egalitarians" (see posting by Dan Kahan on polarities). It is twaddle because the level of CO2 in the atmosphere has to be reduced if the world is to have any chance of keeping below 2 degrees C warming. There is no way that some vague collection of "socio-economic changes" can reduce the CO2 in the atmosphere as required. Only geoengineering can do this. It is also twaddle because the situation in the Arctic is completely ignored. Best scientific evidence points to a vicious cycle of warming and melting in the Arctic as albedo is lost. The only way to break this cycle, and halt the slippery slide into complete Arctic meltdown, is to cool the Arctic. The sooner that IPCC accepts geoengineering as a logical necessity for both CO2 removal and cooling the Arctic, the sooner that the twin dangers from excess CO2 and Arctic overheating will be accepted by politicians and society at large. The talk of geoengineering will make everyone aware that the situation we find ourselves in is already dangerous - really dangerous. The only sensible "pathways to avoid dangerous climate change" must involve geoengineering to remove CO2 and geoengineering to cool the Arctic. The pathway proposed by WG3 is suicidal lunacy. Cheers, John On Sat, Mar 15, 2014 at 12:34 AM, Oscar Escobar <[email protected]<mailto:[email protected]><mailto:[email protected]>> wrote: IPCC AR5 WG2 report - advance briefing Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment, Working Group 3 report Questions and answers in advance of publication http://www.foe.co.uk/sites/default/files/downloads/advance-briefing-ipcc-report-climate-mitigaton-45694.pdf (Excerpt) Reasons to be worried Although the WG3 report will show that the potential to cut carbon pollution sufficiently to make 2 degrees warming unlikely exists, it will also illustrate the very significant socio-economic changes that are needed to do so. Currently the political will to make these changes, for example reducing fossil fuel use or reducing inequalities between and within countries, is sorely lacking. Because of current and past failures to reduce carbon pollution it is not surprising that the IPCC has investigated geoengineering options. However, by doing so it potentially normalises these approaches alongside energy efficiency, renewables, etc. The risks of particularly solar radiation management are very high and this will need to be made clear. What are others likely to say? It is likely that climate deniers will identify the high costs of mitigation whilst ignoring the considerable benefits which outweigh the costs. It is also possible that right-wing think tanks and the media focus on the potential for geoengineering as a potentially low cost response to climate change, particularly regarding the extremely risky strategy of injection of aerosols into the stratosphere as a form of solar radiation management. Friends of the Earth is opposed to the deployment of solar radiation management. There is also the danger that some commentators also reject all negative emissions technologies in addition to rejecting solar radiation management. This is simplistic and could create opposition to development of necessary technologies to remove carbon pollution from the atmosphere (e.g. air capture of carbon utilising carbon capture and storage). -- 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 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]<mailto:[email protected]>. To post to this group, send email to [email protected]<mailto:[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.
