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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Comments 68251 to 68300:

  1. (Fahrenheit) 451 ppm
    #96 Sphaerica : "You continually present a false dichotomy. You require a choice of either "abandon fossil fuels 100% immediately" or "stay on fossil fuels until the entire world is safe from poverty." Wrong. I observe how humanity behave (in energy-climate question) and try to understand why. If you consider the nearly 10 PgC/y emission in 2010 as a problem, you cannot just treat this problem by its future consequences, but you're obliged to discuss its present causes. I don't understand why such a simple idea is problematic here. At least, I understand it is a bit OT, but your reactions are not on this ground. Sea after, answers to Tom are relevant for your point. #97 Tom Curtis : The question is, then, will you withdraw your objection to the 2 degree C guard rail as a reasonable basis of discussion? Or will you instead show by your intransigence that when the science is against you, you just ignore it? Of course 2 K is a reasonable basis of discussion! And even the 350ppm Hansen target is to be discussed. But a) a basis of discussion is not a dogma in policy affairs ; b) as you say, science advises policymakers but does not replace them (happily, unless you dream of kind of 'expert government' where the diversity of human values, beliefs, convictions and consequently policy goals is ignored) ; c) if a basis of discusion is not sustainable, it will be abandoned after having losen a precious time in the wrong direction, and you gave me zero argument for suggesting this basis is sustainable (whereas I put at several moment some orders of magnitude for local (eg Indian) or global energy needs, potentially non compatible with the basis of discussion) ; d) you have totally ignore my major points, notably my 8-points response about my supposed "caveats" in #91 and after my different questions in #95. Such avoidance is sad for me, I've done the best to answer your own arguments against my case ; e) I consider (without any amenity) neither you nor Sphaerica offered convincing argument when you're questioned about the dilemmas between present problems / future problems solutions. I suggest you must have a reflexion on that because it is an argumentative weakness when advocating climate mitigation strategy, and will be more and more in the coming years. #98 John Hartz : Don't know, if there are rules for the number of posts in a discussion, please indicate them to me and I'll respect this number. Anyway I suggest to stop here this endless debate, I'm really tired of it. (-snip-)
    Response:

    [DB] Argumentative snipped.  Let's all rein in all points not specifically germane to the topic of the OP of this thread.  This has descended to the point of "Yes it is" and "No it's not" and detracts from the dialogue on this thread.

  2. It hasn't warmed since 1998
    SirNubwub... You have to pause a moment and think about it though. What are the chances that we're going to see any kind of cooling trend? The radiative properties of CO2 are very clear. It's basic physics. Increased levels of CO2 are going to warm the planet. If that's somehow not happening, then there's about 150 years of well established science to rework (i.e., that's not a very likely scenario). The chances that "global warming has stopped" is extremely unlikely. Where real science is operating right now is a matter of how much warming we're going to see from the expected increases in atmospheric CO2. Is the IPCC central estimate of 3.0C for 2XCO2 correct? Is it slightly lower? 2.5C? Or is it actually higher? ~4.0C? The difference between climate sensitivity of 2.5C and 4.5C has major implications for what human society needs to do to address the situation.
  3. (Fahrenheit) 451 ppm
    John Hartz - Personally, I'm a fan of less moderation, not more. While skept.fr has put quite a lot of volume on this thread (and others), with an unfortunate tendency to use several hundred words where a few would suffice, I still consider this discussion worth having, and quite revealing/educational. * Skept.ft's objections have been shown to be a False Dichotomy between shutting down the world economy - and unchanged business as usual (BAU), claiming that any action leads directly to crushing the developing world. (S)he has simply ignored the middle ground, of replacing current power generation with renewables as quickly as possible. Even a 1 for 1 replacement of aging power plants would lead to a significant (if not, perhaps as speedy as we might hope) cut-back in CO2. But skept.fr appears reluctant to even consider the middle range. * Skept.fr has also neglected the very real costs of continuing climate change, insisting that any limits on power generation are hugely more detrimental than mitigating climate change - again, a false dichotomy, and a strawman argument as well (as every plan I have seen includes ongoing increases in total power generation). This despite multiple studies indicating that mitigation will be far more cost effective than adaptation! * Finally, the ongoing focus on and criticism of any targets appears to be simple avoidance - 'No target is reasonable, so we shouldn't have any targets - take it easy, don't emphasis the risks, or you sound crazy', to paraphrase. This is simply a call for inaction. False dichotomies, strawmen, ignoring information on climate change impacts (It's not bad) - I see these as frequent 'skeptic' approaches that all should be familiar with.
  4. Climate sensitivity is low
    I love Kathryn Schulz! Her talks aren't as good as her book though.
  5. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    #58 dana: Soden & Held, 2006 found, if I understand it correctly, that the size of the 'hot spot' makes no difference to final warming in models. It can be undetectable, or it can be huge. It doesn't matter. The reason being that the 'hot spot' comes from more water condensing in the upper atmosphere, the latent heat causes the warming. This cools the surface (the latent heat comes from surface evaporation). The bigger the hot spot, the bigger the surface cooling. But the bigger the hot spot, the more water vapour stays in the upper atmosphere too so the more greenhouse effect you have. Iirc, Soden & Held found that models always found that the greenhouse effect of the extra water vapour always outweighed the latent heat cooling (the 'lapse rate feedback' or 'Earth cooling by sweating'), and always by about the same amount. This leaves Douglass' speculation with no evidence that I'm aware of, but I do plan to research this in more detail in the future.
  6. (Fahrenheit) 451 ppm
    Why on earth does SkS allow someone like "skept fr" to completely hijack a comment thread like this one and turn it into his/her personal blog site?
  7. It hasn't warmed since 1998
    133, SirNubwup, No. To have some confidence (one can never "know") that warming has stopped you would need to see 17 consecutive years in which you see no trend (mind you, that's not 17 years of no warming each year, but instead no trend in that span of 17 years) in both the atmosphere and the oceans. One would hope that in that same period you would also see an halt in the melting of glaciers and arctic ice and other indicators of a warming world.
  8. Ocean Acidification: Corrosive waters arrive in the Bering Sea
    Rob, I don't think I'd write off the oyster industry. Instumentation has improved to the point where aragonite saturation can be monitored real time at the water intakes for the hatcheries . This allows much improved success in culture of spat because the hatcheries can adapt to pH changes and to some degree modify seawater TA when necessary. Adult oysters are doing fine in current conditions in the Pacific Northwest. I am a commercial fisherman for 40 years and in no way would I dismiss the threat of O/A . I just think we need to acknowledge the successes we have along the way in what is going to be a very long battle. The Oyster industry has really pulled together and made some real progress so rather than writing them off you should go eat some oysters tonite. Thanks for the blog thanks for the hard work and thanks for taking on O/A. Bruce
  9. It hasn't warmed since 1998
    130 Sphaerica So, if I understand correctly, for global warming to be seen to be stopped, we would have to see steady temperatures in both the atmosphere and the oceans. Just one of these is not sufficient. Is this correct?
  10. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    @Richard Arrett If you're trying to suggest that you've in effect been banned, then you're wrong. Make any comment you like (within the rules) on the relevant threads and they will be answered. For instance for questions and comments about CO2 and its relation to current warming, put the relevant words into the search box (top left) and it will show you all the suitable threads. Don't worry, everybody will know you've posted there because the regulars monitor the 'comments' link directly at the top of this column. Happy browsing.
  11. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Thank you for your patience. I will not respond to the later comments directed to me, as it appears my responses would be considered off topic.
  12. The End of the Hothouse
    "The fall in CO2 concentration was from 1000-1200 ppm down to 600-700ppm, at which point it was cool enough to allow glaciers to start to form." If this result holds up to scrutiny, this could easily be a landmark paper, calling for a re-evaluation of the 'CO2 lags temperature' myth. This comment from lead author Pagani is especially relevant: "The onset of Antarctic ice is the mother of all climate 'tipping points,'" he said. "Recognizing the primary role carbon dioxide change played in altering global climate is a fundamentally important observation." An important prior work by the second author is Huber et al 2004: Considering that (1) Antarctica was not kept warm by subtropical currents, (2) evidence of above-freezing Eocene continental interior winter temperatures occurs in high latitudes of both hemispheres, and (3) substantial carbon cycle changes coincide with the Eocene-Oligocene boundary, the most parsimonious explanation of the enigmatic global warmth of Eocene climate was that it was caused by atmospheric mechanisms, such as greenhouse gas radiative forcing ... and potential feedbacks ... . The implication is that changes in greenhouse gas concentrations and subsequent feedbacks were primarily responsible for climatic deterioration into the Oligocene.
  13. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    ahaynes - this is basically an update to Oreskes' original paper which examined the AGW consensus in the peer-reviewed scientific literature. If a paper puts forth an alternative explanation which might explain a large chunk of the recent warming, I believe it's counted on the 'skeptic' list. However, such papers are rare, as this survey found.
  14. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    For those arguing that Douglass et al. should be included in the rejecting papers, this is simply not correct. The tropical troposphere 'hot spot' is not an anthropogenic fingerprint, as we have discussed on SkS several times. Thus this paper cannot bring the human-caused global warming theory into question. The authors of the paper suggest that their results might mean less future warming than is currently expected. Whether or not that conclusion is supported by their research (which I think is questionable), again, it does not bring human-caused global warming into question, but rather the magnitude of futhre human-caused warming. Thus it does not belong on the 'reject' list.
  15. Galactic cosmic rays: Backing the wrong horse
    Eric, Here's another version of a similar graphic: -- source It's difficult to tell if Be10 is that much lower now then in the past; at these scales, the short-term noise is larger than most of the long term variation. I found this Beer slide presentation; the 14th page after the title has another Be10 graph. The lowest points are roughly 48ka, 30ka, 22ka and 2ka. He cites a paper by Muscheler et al in EPSL 219, which I haven't gone after, as the source of that data. I don't see how this line of inquiry, without a mechanism for a climate connection to cosmogenic radioisotopes, helps one way or the other.
  16. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    (A lot of comments above, some of which might have addressed my Q) This series examines whether there's "a substantial case against human-caused global warming" but I think that's too broadly worded and doesn't get at the major objection now - some people these days will admit humans make some (unspecified but nonzero) contribution but raise the prospect that natural factors are more or equally important; would this constitute making "a case against human-caused GW"?. Also it's not clear whether "human-caused" would include other human actions whose effects don't include increased GHGs. I'd like to see a clarification of what's being looked at. (perhaps this has been addressed & I've overlooked it.)
  17. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Richard Arnett: One can be mild mannered and still be arrogant, condescending and rude. From Mel Brooks "History of the World" As noted you've traipsed merrily into a thread about peer-reviewed literature supporting a "skeptical" take on AGW, and have nothing to cite. I hope you've moved your discussion over to any of the threads about the numerous areas you are misinformed about.
    Moderator Response: Richard Arnett, there is a requirement, not just a suggestion, by this site's Comments Policy, for all comments to be on topic of the particular original post. Your initial comments were allowed to stand, so that you could be gently pointed to the relevant threads. Your comments most certainly are welcome, but only if they are on the relevant threads. If you want to comment on multiple topics, you must split your comments across the relevant threads. Your grace period has passed, so if you post irrelevant comments on threads where you already have been warned not to, your comments will be deleted.
  18. (Fahrenheit) 451 ppm
    skept.fr @95, I am not interested in re-arguing the whole case with you. My intervention was simply to point out your biases and prejudices behind whose ramparts you where criticizing SkS as being insufficiently skeptical (a refrain you keep on returning to regardless of evidence). One key bastion of your fortress of bias was the claim that the 2 degree C (450 ppmv) guard rail was not based on science but on political discussions and decisions. I have comprehensively demolished that pretense above. You now retreat behind a further bastion, that we can ignore particular scientific discussions of the preferable target because it is not part of an IPCC summary, and hence not part of the consensus of climate science. However even this bastion is shadow rather than rock. If you wish to maintain the IPCC has provided no guidance on this issue, you need to explain the purpose of the updated reasons for concern and the discussion of mitigation strategies in Working Group 2. While doing so you would do well to note their opinion that:
    "...quantifying market-based damages associated with MOC changes is a difficult task, and current analyses should be interpreted as order-of-magnitude estimates, with none carrying high confidence. These preliminary analyses suggest that significant reductions in anthropogenic greenhouse gas emissions are economically efficient even if the damages associated with a MOC slowing or collapse are less than 1% of gross world product. However, model results are very dependent on assumptions about climate sensitivity, the damage functions for smooth and abrupt climate change and time discounting, and are thus designed primarily to demonstrate frameworks for analysis and order-of-magnitude outcomes rather than high-confidence quantitative projections."
    Fairly obviously a cost/benefit analysis that only demonstrates "orders of magnitude outcomes" has no inherent superiority to guard rail analyses, or analyses of stabilization targets. More crucial to this point,however, is the discussion in WG 3, in which they state:
    "[S]ignificant benefits result from constraining temperature change to not more than 1.6°C–2.6°C above pre-industrial levels. These benefits would include lowering (with different levels of confidence) the risk of: widespread deglaciation of the Greenland Ice Sheet; avoiding large-scale transformation of ecosystems and degradation of coral reefs; preventing terrestrial vegetation becoming a carbon source; constraining species extinction to between 10–40%; preserving many unique habitats (see IPCC, 2007b, Chapter 4, Table 4.1 and Figure 4.5) including much of the Arctic; reducing increases in flooding, drought, and fire; reducing water quality declines, and preventing global net declines in food production. Other benefits of this constraint, not shown in the Table 3.11, include reducing the risks of extreme weather events, and of at least partial deglaciation of the West Antarctic Ice Sheet (WAIS), see also IPCC, 2007b, Section 19.3.7. By comparison, for ‘best guess’ climate sensitivity, attaining these benefits becomes unlikely if emission reductions are postponed beyond the next 15 years to a time period between the next 15–55 years. Such postponement also results in increasing risks of a breakdown of the Meridional Overturning Circulation (IPCC, 2007b, Table 19.1)."
    The prospect of 10-40% of all species on Earth going extinct illustrates the severity of the risk imposed by AGW, a risk which increases with increasing temperatures. Of course, what you won't find in the IPCC reports is an explicit statement as to the appropriate temperature for a guard rail. That is because the IPCC reports are advise to policy makers, not policy making themselves. However, the clear advise of AR4 WG3 is that in the range of 1.6 to 2.6 degrees C, impacts are severe but potentially not catastrophic, where as beyond that all bets are of. In other words, the IPCC may indicate that there will be massive ecosystem collapse at temperature increases greater than 4 degrees C, with a minimum species loss of 35% (making global warming potentially the second or third largest ever mass extinction, and significantly worse than the K-T extinction event that destroyed the dinosaurs), but it is still open to policy makers to decide that life in a greater than K-T extinction event is an acceptable option. Of course, as citizens, they have no doubt that anybody who would take that option either is secure in the fact that they will not witness it, or are insane. Returning to the primary, and very simple point. You have indicated very forcibly that the 2 degree guard rail is simply a manufactured number for political convenience. I have demonstrated that, on the contrary it is a figure based on science, and science reported by the IPCC. The final decision was made by policy makers, but it was an informed decision. The question is, then, will you withdraw your objection to the 2 degree C guard rail as a reasonable basis of discussion? Or will you instead show by your intransigence that when the science is against you, you just ignore it?
  19. (Fahrenheit) 451 ppm
    skept.fr, You continually present a false dichotomy. You require a choice of either "abandon fossil fuels 100% immediately" or "stay on fossil fuels until the entire world is safe from poverty." This fails because obviously there are solutions in between. The key point, however, is that any transition away from fossil fuels is going to take a lot of time so we have to start now. In Tom's words:
    It takes time to transition from a high carbon to a low or zero carbon economy. With the best will in the world it could not be done in less than twenty years, and ideally it would be phased in over 40 to 50 years (ie, through the natural cycle of replacement of obsolete power plants). Anything faster incurs significant increased costs.
    You are repetitively ignoring this reality by continually falsely representing the problem as an either/or choice between all or nothing. This is not the case.
  20. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Richard Arnett@30 "I thought that CO2 followed temperature by around 700 years." & "...the natural warming which may have occurred since 1850 could be the cause of the higher CO2 levels." 1850 was not 700 years ago. So either, no it is not the cause of the current CO2 increase or CO2 response to temperature increase is MUCH larger than we think. 600 more years of this would put as at ~1000ppm Of course all this ignores the known output of CO2 due to human activities.
  21. Climate sensitivity is low
    For the record, the 16.6 W/m^2 RW1 keeps throwing around is from his own entirely incorrect logic that there is a direct relationship between the radiation leaving the surface and the radiation emitted at TOA, and that this requires a linear "gain" and therefore the creation of non-existent energy. It basically comes from a completely flawed understanding of the system, I think because he is trying to translate it entirely into his own misapplied EE concepts of "gain," "feedback" and control theory rather than by understanding climate science and the actual system under discussion. The clearest (convoluted) path to understanding his logic is here, but in a nutshell, 16.6 W/m2 is a ridiculous constraint of his own devising, and there is no arguing with it, because he can't get past the mumbled incantations and heavy incense needed for his magical spells.
  22. Climate sensitivity is low
    DB, you should probably tack that comment on to every post that RW1 makes, so that no one makes the mistake of engaging him/her in discussion. It will also act as a standing demonstration of exactly what denialism is--a one-way street where the denialist presents the Truth and refuses to admit error. I've asked "wrongologist" Kathryn Schulz to target the global warming issue through interviews with a number of opinion-makers and scientists. I hope she ends up doing so. It's a very rich area for her--not just in the exploration of what happens when people who are committed to alternative theories come up against hard evidence against them, but also in statisticians' and scientists' relationship with modeling, in people who are paid to be publicly wrong, and in how scientists deal with being wrong.
  23. (Fahrenheit) 451 ppm
    #94 Tom : I would have prefer a counter-argument on my 8 points in #91, but let's go. Your answer first brings us to another of my concern about Sphaerica’text. Why IPCC exists ? Because there are thousands of science papers each year, because there are dozens in independant climate models and enery-economy models, beacause we need a global assessment of the confidence of climate scientists about the robustness of their results. As it has been noted by SkS , ‘The IPCC was formed to report on a broad range of scientific enquiries into the climate, and our effects on it, and to summarise the science for laypeople. The science they summarise is published so it is simple to compare the primary science with the IPCC reports, and compare both to what actually took place.’ In this paper, SkS suggested : ‘Claims that the IPCC is alarmist are not supported by evidence, and there are clear indications that the opposite may be the case.’ I don’t know what means the ‘opposite’, but if it is suggested that we must not believe the IPCC reports because they are too ‘non-alarmist’ (the logical meaning of the sentence above), it would be particularly devastating in my point of view. IPCC has always been the target of deniers because the doubt on the quality on statements from IPCC reports would imply a disruption in the public trust in climate science conclusions, as it would be very easy to say ‘oh scientists disagree, all that is matter of debate, we’ll see later’. Previous point explains why I’ve problem with reference like Smith 2009 in PNAS. Why? Because it’s the job of the whole climate community (and not 17 of its members) to assess the reasons for concern from the whole literature (and not just part of this literature). For example, one of this reason for concern is the risk of extreme weather impacts. But there is a recent IPCC report dedicated to this specific question, SREX 2011 (quoted above), so we should refer primarily to such a report. At least, a reference to this report will have more weigh than a reference to a particular study in the thousand of studies among literature. Of course, you have the (democratic) right to select your references and to determine from them you own level of risk or dangerous change. It was my point, so feel free to refute or endorse it, but be coherent in your choice. For my part, I suggest the good choice would be to refer to IPCC. And I observe it is the typical denialist strategy to distrust IPCC and to cherry-pick the studies that minimize sensitivity, sea-level rise, icesheets melting, etc. Of course, from a skeptical point a view, a symmetric and opposite cherry-picking is of no value. That’s why the SREX reference is correct for our level of understanding about extreme events projections impacts, vulnerabilities, etc. And the future AR5 2013 will be the correct reference for broader conclusions about climate change. The same is true for Bill Hare 2005 paper : not only it is a one-man work, but it has been written before the AR4 2007 publication. So at least, you must refer to WG2 and WG3 2007 conclusion concerning the impact or mitigation, as I did above when criticizing some Sphaerica’s proposals. And the same for Danny Harvey 2007 Clim Change paper. More broadly, you’re speaking of the future deaths in the third world due to climate change. But nowhere you speak of present deaths in the third world due to non-climatic reasons and nowhere you critically assess the carbon consequences of policy choices for preventing these present deaths. As the long as this blindness to present problems is the rule in climate mitigation debates here, don’t expect any trust in the conclusions from such a one-sided approach. The 20 years CO2 rise is mainly due developing countries. So look at another publication from UN experts, the Millenium Development Goals report. What is said for example in the latest fact sheet about the first concern, Eradicate Extreme Poverty and Hunger ? : ‘Over a 25-year period, the poverty rate in East Asia fell from nearly 60 per cent to under 20 per cent. Poverty rates are expected to fall to around 5 per cent in China and 24 per cent in India by 2015 (…)The World Bank estimates that the effects of the economic crisis will push an additional 64 million people into extreme poverty in 2010, and that poverty rates will be slightly higher in 2015 and beyond than they would have been without the crisis, mostly in sub-Saharan Africa and Eastern and South-Eastern Asia. (…)Between 1990 and 2008, the proportion of underweight children under five declined from 31 per cent to 26 per cent in developing regions with particular success in Eastern Asia, notably China. Despite such improvements, progress is currently not fast enough to reach the MDG target, and particular focus is required in Southern Asia.’ So it easy to see how our economy and energy decisions will affect the quality of life in the world : million of children in China have benefit from the carbon-intensive policy of their government. A 3% of negative growth is not just about ‘pizza’, it is about damaging consequences for such million of people now, and billion from now to 2050. That is the reality we must all cope with : million of people now escape each year poverty, hunger, disease, illiteracy thanks to policy choices founded on carbon-intensive energy supply for the national infrastructures. The denialist attitude toward such a reality is no more sustainable as there is an exponential growth of emission from non-Annex B countries. As defender of an egalitarian agenda, the problem for me is not just the share of wealth, but the very first creation of the wealth we can share in the present and the future. Your involuntarily bad but so suggestive example of 1950 USA standard (point 8 above) showed how difficult it is to universalize what is perceived here in Western contries as a medium quality of life without the supply of huge amount of energy. This is not about pizza, this is about the present and next generation life. And this is about my main point of concern in the present discussion : if we are to prevent a too sharp CO2 rise, we must first understand the origin of the rise from a human needs perspective and we must assess our policy choices for their realism in that purpose of satisfying human needs. Not just draw scary but impotent scenarios for the second part of this century. Not just defend a 450ppm target as an unquestioned mantra. Let's say that Smith at al 2009 are correct and preclude the future IPCC AR 2013 conclusions, or that your 3 billion citizens water-disrupted estimate in 2070 or 2090 (for a 2,5-3K transient warming) is correct. In this eventuality, what must we do? Must we cut CO2 emissions at any cost, or must we cut these emissions in so far we can replace the carbon energy service they provide by another service of the same quality? Must we ultimately forbid or strictly limit the fossil supply even if we know that a non-fossil source cannot provide the same amount of energy for population needs? Is the urgent good choice a 450 ppm target or a progressive carbon tax or another strategy? What if tomorrow India or another giant simply leaves climate negotiations they perceive as a threat for their national development and the world sink in a selfish strategy of separate energy choices? How can we accelerate the deployment of RE energy now and not in 10 or 20 years? That are non trivial questions waiting for non-trivial answers. Hope you have the time to look at the Revkin's links, some of these deal with such new perspective of the climate mitigation strategy.
  24. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    It seems that since I first posted a response to Richard Arrett back at #4, he has been given many reasons why he's wrong, seemingly to little effect. So I thought it might be worth summarising his position in the hope that he might see how illogical it is. Mr Arrett accepts that the rapid warming that we've experienced since 1950 is coincidental with a massive increase in CO2. However -- for reasons known only to him, and which he won't reveal -- Mr Arrett does not accept the mainstream science on which the consensus is built, that is generally acknowledged by the scientific community to explain the rapid warming. Instead, Mr Arrett wants to believe that there is an alternative cause that falls outside all the known natural and man-made forcings. Unfortunately he can't think what it might be, so he just endlessly repeats that there has to be another cause. What? Like maybe the turtle whose back the Earth stands on has caught a cold and is running a temperature? Last -- although he can't come up with a convincing alternative explanation himself -- he's asking scientists to disprove the alternative explanation (the 'turtle') that he just knows has to be there. The problem is, Mr Arrett, some elusive figment of your imagination, which constantly rewrites the laws of physics in order to survive, cannot be disproved if you won't accept the science. Sorry, the onus is on you.
  25. Galactic cosmic rays: Backing the wrong horse
    muoncounter, true about the space age but looking back further
    we seem to be at relatively low level of cosmic rays, with the caveat that there is no clear connection to climate in the period above, nor evidence of strong physical mechanism as we discussed in this thread. (source of graph is Beer et al 2006 - having trouble linking)
  26. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Richard Arrett talks a lot about the burden of proof – the science is much clearer then he thinks, as repeatedly shown on this website – so how about the burden of responsibility Mr. Arrett.
  27. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Richard Arrett @ 30 : That's what we have quantitative science for. Clever wordsmithing by the 'skeptics' has confused a lot of people about things. In the case of CO2, if you _only_ look at the ice cores then you find that yes, CO2 has lagged temperature in the past 800ka. I agree in this case that there is a burden of proof to show that a) the increase is human caused and b) CO2 can cause warming too. a) is shown by how human emissions (30 bn tons/year) are bigger than the amount going into the atmosphere (15 bn tons), and by how the oceans are gaining carbon. It's effectively certain that the entire CO2 rise is caused by humans - unless one of the skeptics' Harry Potter theories (transmuting carbon, astrology, whatever) is true. On top, you can do calculations using Henry's Law showing that the current CO2 concentration couldn't be achieved without massive fossil fuel emissions or burning down huge quantities of forest (much more than we see with satellites). b) is shown by physics, which you already accept. Once you add this evidence to the ice cores, isn't the burden of proof now on those who claim that the CO2 rise is natural? After all, they are claiming that chemistry, physics and measurements are all wrong.
  28. Schmittner et al. (2011) on Climate Sensitivity - the Good, the Bad, and the Ugly
    Hi Tom, Fair point about the ice a lower latitude in view of amount of land per unit of solar input due the earth's curvature but that isn't that great an effect from North to South Canada is it? The length of time in the sun is pretty similiar due to very long summer day in the poles, winter ice is irrelevant almost for albedo effects. Also during the Last Glacial the sea in the Pacific was cut of from the Arctic so was ice free I suspect and due to the gulf stream can't see it getting a massive amount larger in the North Atlantic in the summer either and the albedo effect on land is a much lower shift in effect (0.9-0.4-5) compared to (0.9-0.10) for open water. Then of course there are the extra accelerants of tree line moving northwards and the warming effects of the Arcitc ocean that were never present in most previous interglacials. Also Land based Ice sheet take ages to melt away compared to sea ice (although surface melt ponds can be siginificant), so sea ice loss at the pole in summer is like a turbo albedo effect is it not? I just can't help feeling that losing the arctic sea ice in summer (recently predicted for 2015) is going to rapidly increase warming, change all the NH weather systems to some degree. Of course Greenland and WIAS are also suspectable and from warming in the tropic was all the hot water baths the underneath of the below sea level ice sheets (especially in WAIS, which may accelerate the albedo effect. For short-term CS it seems worrying to realise that within 95% probability it could be upto 6oC with Ice present if the pliocene and lots of other paleo data is correct like the Royer paper suggests, that means 350ppm still means a 95% range of temperature rise of 1.8-3C roughly, and getting to 350ppm is going to take a lot lot lot more radical approach to anything that is being suggested by any international agreements. The evidence suggests it is time for a transformational scale change away from fossil fuels to carbon sequestration and every once of carbon counts as even total reforestation only draws down 20ppm! "The drawdown generated in northern-temperate- and tropicalafforestation(~20 ppm) simulations is more than double the drawdown produced by boreal afforestation (9 ppm)." Small temperature benefits provided by realistic afforestation efforts Vivek K. Arora1* and Alvaro Montenegro NATURE GEOSCIENCE VOL 4 AUGUST 2011 514
  29. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Richard Arrett said: "However, I also thought that the data was also consistent with other hypotheses, and that we did not have enough data to rule out one or the other yet." That is incorrect, skeptic hypotheses are only consistent with cherry picked parts of data. When you collate all the skeptic hypotheses and try to make sense of them, they either don't fit together, or in some cases even conflict with each other. What is usually bizarre is that the skeptics that have conflicting theories don't argue and attack each other! I think we all know why.
  30. Climate sensitivity is low
    Skywater @261 I believe that is the starting point in understanding how energenic the atmosphere realy is And without the van allen belts to protect us from the solar winds and cosmic rays (charged partical) life how we see it would not exist. That said it's my belief that what we are seeing regarding man made climate change is a result of or com's and detecting that use electromagnetic radiation from the ground and space http://missionscience.nasa.gov/ems/02_anatomy.html and is very sensitive to this process and would create changes and hot spots through processes like this. http://www.ips.gov.au/Category/Educational/Other%20Topics/Radio%20Communication/Transequatorial.pdf There's a picture halfway down that shows hot spots expanssion and a bulging at the equator that is interesting. And as you know heat and preasure differences drive the weather Just putting it together to for a bigger picture
  31. (Fahrenheit) 451 ppm
    skept.fr @93, it is no more a democratic right to decide that 350 ppmv, or 450 ppmv or whatever target is ideal than it is a democratic right to decide that pi should equal 3. What is a limited democratic right is the decision to accept a certain level of harm. Having done so, it then is a matter of science as to what temperature increase (if any) will result in that level of harm, and what CO2 concentration will result in that temperature increase. As to what is an acceptable level of harm, here is the basic data: Note that the increase in temperature is from 1990 levels. From a < a href="http://www.pik-potsdam.de/~mmalte/simcap/publications/Hare_submitted_impacts.pdf">more detailed study we learn that:
    "The number of people living in water stressed countries, defined as those using more than 20% of their available resources, and is expected to increase substantially over the next decades irrespective of climate change. Particularly in the next few decades population and other pressures are likely to outweigh the effects of climate change, although some regions may be badly affected during this period. In the longer term, however, climate change becomes much more important. Exacerbating factors such as the link between land degradation, climate change and water availability are in general not yet accounted for in the global assessments. ... Over 2 C warming appears to involve a major threshold increase in risk. One study shows risk increasing for close to 600 million people at 1.5 C to 2.4-3.1 billion at around 2.5 C. This is driven by the water demand of mega-cities in India and China in their model. In this study the level of risk begins to saturate in the range of 3.1-3.5 billion additional persons at risk at 2.5-3 C warming [42, 48]."
    Now, you may think it is OK to democratically decide that it is better that 3 billion people go without adequate water than that they lose 3% of their income, but as the people being so democratic are not among those risking the loss of water, I don't think so. Hence a limited democratic right. The key point here, however, is that there are many scientific studies which show that the negative impacts of climate change rise sharply above 2 degrees C. You showed in your sarcastic sentence, and again in your comment above that you are unfamiliar with that literature. It you where not, your comment about a target only set as policy and by politicians would be actively deceptive. You critique Hansen and co-authors for not being economists, and it is true that they do have that virtue. An economist is, after all, a person who "knows the price of everything and the value of nothing", a fact shown by the repeated failure of the cost benefit analyses you are so fond of to include the costs of the loss of ecosystems. However, Hansen et al did not just pull a target out of their hat. Rather, they built on the work of Danny Harvey who showed that:
    "The allowable radiative forcing ratio depends on the probability of significant harm that is tolerated, and can be translated into allowable CO2 concentrations given some assumption concerning the future change in total non-CO2 GHG radiative forcing. If future non-CO2 GHG forcing is reduced to half of the present non-CO2 GHG forcing, then the allowable CO2 concentration is 290–430 ppmv for a 10% tolerance (depending on the chosen pdfs) and 300–500 ppmv for a 25% risk tolerance (assuming a pre-industrial CO2 concentration of 280 ppmv). For future non-CO2 GHG forcing frozen at the present value, and for a 10% risk threshold, the allowable CO2 concentration is 257–384 ppmv. The implications of these results are that (1) emissions of GHGs need to be reduced as quickly as possible, not in order to comply with the UNFCCC, but in order to minimize the extent and duration of non-compliance; (2) we do not have the luxury of trading off reductions in emissions of non-CO2 GHGs against smaller reductions in CO2 emissions, and (3) preparations should begin soon for the creation of negative CO2 emissions through the sequestration of biomass carbon."
    Here a 10% risk threshold represents (conservatively estimated) "... allowing for a risk of death to individuals that is 100- to 1000-fold greater than the one-in-one-million threshold adopted by the US EPA and NRC." A 25% risk, ie, the 450 ppmv threshold, represents a risk of death from global warming that may be as high as 1 in 400. Not adverse impacts, mind, but death. As indicated before, these studies consistently show adverse impacts across a range of measures rise sharply above 2 degrees C. Of course, there is a caveat here. The studies may be in error and the sharp rise in negative impacts may follow 3 degrees C, or 1 degree C. But taking a central estimate of a 2 degree C threshold, and assuming significant encroachment beyond that threshold is at least as bad as the upper range for 2 degrees, then pushing global temperatures to 2.5 oe 3 degrees C will only be 1 tenth as bad as the 1985 Ethiopian famine (death rate of 1 in 40). Of course, that 1 tenth as bad averaged across the entire globe, and will be much worse in particular places and at particular times. So, my "democratic" right is to decide between a 3% loss of my income, or an additional 1 in 400 chance of premature death for my grandchildren and all their contemporaries. Of course, the cost benefit analyses have this covered, and handle it very elegantly. They notice that most of those deaths will be in the third world, and that a third world life is not worth as much as a first world life - so the benefit of saving those future lives (another important factor in making the lives less important) does not weigh much against the cost of a loss of 3% of my income (which may mean I need to go a week without pizza). (Please note, Richard Tol is on record as defending exactly that analysis for his cost benefit analysis, which he is also on record as saying Lomborg distorted by using a different and prejudicial discount rate for when compared to other alternative for meeting the worlds needs. I'm not sure Tol is on record about Pizza, though.) Returning to Hansen, what he has argued is that the previous work on thresholds have used only the Charney sensitivity, and that a target set on that basis will result in the long term in significantly higher temperatures due to the long term feedbacks.
  32. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    If you want to put up a position in the face of all established science (specifically, how could you increase GHG levels without causing warming), then that is an extraordinary claim. You can only propose natural cause if you can show us a natural cause. In science you must have evidence and that is what the skeptic position is lacking. For a skeptic position to credible, it needs two things: 1/ A natural forcing to explain current warming. 2/ A mechanism to negative greenhouse gas warming. Discussing a null hypothesis makes no sense in face of actual warming. Something has to cause it. To postulate a low sensitivity in the face of both theoretical and empirical data requires demonstrating the existence of a negative forcing. That is the position of Lindzen, Spenser. Just not succeeding so far.
  33. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    "This was the portion of the post which suggested that skeptics have the burden of proof (we have to 'falsify' the human-caused global warming theory)." Saying that no paper falsifies AGW is a statement of fact. The author is just reviewing what he claims to show, that despite what you might think by reading on the blogs, no paper falsifies AGW theory. How does that suggest "the burden of proof" is unfairly on skeptics? I agree with a comment upthread that this isn't a court of law, people are just trying to sort out whether bloggy claims about AGW not being real are supported by the peer reviewed literature. I don't see how pointing out that they're not is placing some unfair burden on one side..
  34. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Richard: natural variability...is the null hypothesis." I may be going out on a limb here, but I don't think the term "null hypothesis" is inclusive of mysterious undetected forces that contradict demonstrable facts about how the world works, which seems to be what the "skeptical" definition of natural variability amounts to these days.
  35. Climate sensitivity is low
    RW1 - Well, then, my apologies, I had not found that clear from your posts, which is probably my mistake. Mea culpa. So: a 10 W/m^2 TOA forcing results in a ~16.4 W/m^2 surface change. Of that 10 W/m^2 3.7 W/m^2 is direct CO2 forcing (assuming a CO2 doubling), and the remaining 6.3 W/m^2 is (as predicted by a 3°C sensitivity, with caveats due to uncertainties - 2-4.5°C) due to feedbacks. I would suggest viewing the detailed discussions at Water Vapor vs CO2 as a “Greenhouse” Gas and in particular Clouds and Water Vapor – Part Four by Science of Doom. Note that models of outgoing longwave radiation (OLR) match very well with observations, indicating that the models are pretty accurate. Water vapor represents ~2/3 of the greenhouse effect (in conjunction with clouds), and since water vapor is temperature dependent, it is a feedback, not a forcing. In addition, see Philipona et al 2005 ("...enhancing the forcing and temperature rise by about a factor of three") and others - water vapor is a strong positive feedback, as shown by the data.
    Response:

    [DB] Please note that RW1 has never retracted this statement:

    I appreciate that you seem to be interested in helping me, but I'm not really interested in being helped per say. I'm a staunch skeptic of AGW, so my purpose here is to present contradictory evidence and logic that disputes the theory. That's what I'm doing.

    By his own admission he is here to not learn.

  36. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Richard Arrett@45, I am a sceptic and I am not afraid of pointing to the evidence which supports my agreement with the AGW theory. The fact that we are both posting here at SkS means we both have access to a large amount of suitable information. In fact, I would hazard a guess that the truly sceptical (ie those who follow the evidence, not the loudest voice) who post here have been pointing to the evidence very clearly since the site opened. If you are a sceptic, you must have access to evidence. I ask again for you to produce the evidence that there is a case against AGW in the peer-reviewed literature, as I am not so far impressed by your apparent evasion of the subject. If you want to change minds, it is better to appeal to their intelligence than their credulity.
  37. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Richard Arrett - Find a respective thread to which your assertion relates, and post there. My fault for responding and not ensuring this was done earlier.
  38. Galactic cosmic rays: Backing the wrong horse
    Eric#110: "we are in a relatively low GCR period so the decreases may not be as effective" May I remind you, in 2009: Cosmic rays hit space age high And that was measured by the ACE satellite at the L1 point, where no atmospheric ionization gets in the way. FDs would be plenty noticeable. The problem for GCR adherents is that there just aren't enough of them. That's no doubt why the CLOUD experiment design straddled the energy line between solar cosmic rays and GCRs. But if you say solar cosmic ray flux modulates clouds, then you're still stuck in the high solar activity-> fewer clouds -> warming trap. Picking that warming signal out from the high solar activity warming is a tiny needle in a very large haystack.
  39. (Fahrenheit) 451 ppm
    #89 Tom Are you suggesting, perhaps, that we should adopt Hansen's scientifically supported target of 350 ppmv? No, of course not. A caveat that Hansen may be right goes in the wrong direction for you, and is consequently ignored. If you had paid any attention to it, you would not be so sarcastic about a 450 ppmv target. Your sarcasm, however, captures perfectly how one sided your skepticism is. I haven’t seen this point. Again, we can choose a 350ppm, a 450ppm, a 550ppm target... this is ultimately a policy choice of what we, humans, define as a level of climate change we can tolerate when we're correctly informed by science. If my neighbor decides that 650ppm target is its ideal, he has the fundamental right to do so and to try to convince policymakers that he's correct. The same of another neighbor that would prefer 250ppm as the correct level. That is not relativism, that is democracy, as far as a policy goal which impacts everyday life is subjet to the citizens' evaluation in a democratic system. If Hansen et al consider in their 2008 paper that, concerning climate, the 350ppm target would be a good one, they’ve their scientific reasons. And this will be normally discussed by their pairs, as it is the case in climate sciences for decades, and all sciences for centuries. IPCC AR5 will integrate and evaluate this work among others; I've not the competence to judge if James Hansen is right or wrong, that is a scientific debate among specialists, and notably modelers. But when it comes to policy, I can observe that Hansen and co-authors are not specialists of energy, economy, health, sociology, agronomy, and many domains of expertise that are concerned by the energy supply and use in human societies (eg WG3 job). I suppose you’ll agree that we cannot choose a CO2 target for humanity on the sole basis of one paper concerning one aspect (climatic) of the consequences of such a target. All that is just a variation on the points 2 and 3 of the previous message. Beside this point, I was sarcastic in this deleted (and poorly inspired by irritation) sentence, but I'm opposed to the 'sacrosanctification' of the 450 ppm target for rational reasons I developed previously in the thread. And I profit to suggest fellow readers the interesting Andy Revkin recent article about COP Durban, with all its link, notably the William R. Moomaw and Mihaela Papa op-ed. #90 John : He not she. And he is not 'disciple' (horror) of Lomborg (but critical reader of some of his books).
  40. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    KR @41: So I take it that you agree with me that the post in general, and the portion I quoted in particular do put the burden of proof onto the skeptic? You seem to agree that the burden does belong on the skeptic anyway (which I disagree with). By the way - the great mass of data you refer to merely show that it has warmed - not what has caused the warming. What caused the warming from 1700 to 1850? Whatever it was, it was not the rise in CO2 level - right? For that matter, it has been warming since 12,000 years ago. Sea level has risen 120 meters since then. What caused that warming? How do you know that what caused that warming isn't continuing to cause the latest .8C rise?
    Response:

    [DB] Those who respond to these various, unsupported assertions...please take it to a more appropriate thread than here.  This is OT here.

  41. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Richard Arrett#40: "This was the portion of the post which suggested that skeptics have ... to "falsify" the human-caused global warming theory." Apparently you do not have the data/facts/science to do this, so you're playing the 'argue the argument' card. #42: "data show that CO2 lags temperature. " Old news. Things have changed: somebody's putting a lot of CO2 into the air, which wasn't there back in those days. What was a feedback is now a forcing, according to physics. "suggest that this argument supports the notion that increased warming can cause GHG's to increase?" No, its chicken and egg boring. See: CO2 is the biggest control knob. Use the Search function, read and learn. But this thread was about a case in the peer-reviewed literature against AGW. Got any worth talking about?
  42. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    30, 42, Richard Arrett, Concerning CO2, temperature, and the transition from a glacial to an interglacial period, please see my recent post here. That should clarify for you what you are misunderstanding about the way the components of the system interact.
  43. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Dave123 @36: "It's positively insulting to the people who've put this site together for you to suggest that warming has caused the CO2 levels to increase" The data show that CO2 lags temperature. I thought one of the arguments for increased GHG's was that as the permafrost melted, it released methane gas. Is it insulting to suggest that this argument supports the notion that increased warming can cause GHG's to increase? I wonder if increasing temperature increases the risk of wildfires, leading to additional CO2 being put into the atmosphere? I doubt the people that run this blog find my mild mannered dialog as insulting as you do - but perhaps they will chime in and let me know.
    Response:

    [DB] "I doubt the people that run this blog find my mild mannered dialog as insulting as you do - but perhaps they will chime in and let me know."

    Can we all dial back the emotions a bit?

    "The data show that CO2 lags temperature."

    You have been pointed out as to the fallacy of this position.  Use the Search function.  Read, learn more.  Comment/question after.  Repeat as necessary.

    "I thought one of the arguments for increased GHG's was that as the permafrost melted, it released methane gas.

    Is it insulting to suggest that this argument supports the notion that increased warming can cause GHG's to increase?"

    It is well-understood that under non-anthropogenically-forced conditions, CO2 is generally a feedback.  Similarly, it is well-understood that under today's injection of long-sequestered fossil-fuel derived GHGs that CO2 is now acting like a forcing.  And will continue to do so for decades after all fossil fuel emissions cease.

    And yes, CO2 forcings raising temperatures also cause feedbacks which release even more greenhouse gases.  Hence the imperative to cease with the hand-waving of delay and act.

  44. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Richard Arrett - "This was the portion of the post which suggested that skeptics have the burden of proof (we have to "falsify" the human-caused global warming theory). " Given that the vast preponderance of the data supports human influences on global warming, yes. To quote Carl Sagan, "Extraordinary claims require extraordinary evidence." And refuting the great mass of data supporting the consensus view is a very extraordinary claim indeed...
  45. (Fahrenheit) 451 ppm
    skept.fr - "And so, why we do not implement immediately a global carbon tax, that is what I called "pricing carbon externalities"? It is very easy to implement (directly on coal, gas and oil producers, or deforesters) and quite easy to adapt (part of the tax will help specifically low and medium GDP countries that will be more affected by higher prices)." (emphasis added) I would, and do, support that. It's unfortunate that conservative ideologies (anti-tax) refuse to even consider this as a possibility. Hence (as an important note) my concern for informing such folks of the consequences of their (in)actions...
  46. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    Utahn @39: "None of the papers provides the “killer argument,” the one devastating fact that would falsify human-caused global warming." This was the portion of the post which suggested that skeptics have the burden of proof (we have to "falsify" the human-caused global warming theory).
  47. Climate sensitivity is low
    RW1 - You continue to mix TOA forcings with surface flux. Please note that an effective TOA emissivity of ~0.612, as measured and calculated, means that a TOA forcing of ~10 W/m^2 leads to 1/0.612 = ~1.64, or a required ~16.4 W/m^2 increase at the surface to increase emissions by ~10 W/m^2 at TOA to eliminate the imbalance. And that is strictly due to the emissivity of the Earth wrt. a blackbody. Your posts continue to interchange TOA with surface forcings, neglecting the effective emissivity to space (as per multiple threads), continue to invoke inappropriate "halving" of absorptions, and IMO represent errors. Nonsense statements such as "+6 W/m^2 (+1.1C) from 2xCO2 (3.7 W/m^2 directly from the CO2 'forcing' and the remaining 2.3 W/m^2 from the current average opacity of the atmosphere" do not aid your position (I have absolutely no idea where you got 2.3 from, for example). Your insistence on these issues demonstrate either (a) a lack of comprehension, or (b) an unwillingness to let data influence your position. Enough said. You have repeatedly demonstrated either a lack of knowledge or unwillingness to examine the evidence. Readers - if you wish to follow these conversations further, I would suggest the Climate Sensitivity or Lindzen and Choi threads, where this issue is discussed at great length. Personally, I feel no desire to rehash these topics...
  48. Is there a case against human-caused global warming in the peer-reviewed literature? Part 3
    #13 Richard Arrett "The part which requires that skeptics have the burden of disproving AGW." I guess I still don't see that part of the conclusion, can you quote from the post what suggests skeptics have the burden of proof?
  49. Climate sensitivity is low
    KR, "Your numbers are wrong." Are you trying to say the surface does not have to receive +16.6 W/m^2 in order to warm by 3C?
  50. (Fahrenheit) 451 ppm
    #88 Tom, please to read you here. 1) Although a layman, I myself always question my own skepticism, because I know our judgements (including mine) are so easily biased by poor information, prejudices, emotions, beliefs, etc. And I’m happy your critics drive me to such a questioning. But that is critics, not strawman about my supposed hidden goals. I hope you make the difference and you understand why, for my part, I doubt the bona fides of some of my interlocutors. 2) I do not neglect the caveat that climate sensitivity may be high, I’ve strictly no idea about that and I believe what models produce. We’re obliged to do so, AOGCMs and tomorrow Earth System Models are our sole instrument for such projections. Paleoclimates do not guarantee that CS in past conditions is the same that CS in current conditions, as it has been acknowledged in Schmittner et al discussion (for example on Real Climate). We are obliged to take decision under uncertainty : I consider the best choice is to rely on what models consider as their best estimate (eg 3 K). Of course, you can choose a lower or higher estimate. It depends on the perception of risk. If the choice of the higher sensitivity was cost-free and risk-free, it would be the most rational solution. But it is not, so the higher you choose a sensitivity, the more rigourous and precise you must be to estimate and justify the cost / risk that are the consequences of your choice. 3) I consider all level of warming as potentially ‘dangerous’, I’ve no reason to invent a treshold that would separate a dangerous and a non-dangerous warming (the same would be true for cooling, by the way). I don’t think the 2 K value has a sense, it’s purely conventional and IPCC never defined this value (it is recognized as a political choice, as the definition of 'dangerous' is not a scientific task). So, the less we warm the atmosphere, the ocean and the surface, the better it is. But I add : as long as the effort to lessen warming doesn’t produce more harm than it prevents. And here is the Gordian knot of our discussion : I don’t want a vague description of what is ‘dangerous’, I want a costs-benefits analysis of climate change compared to energy-economy change. My demand has nothing to do with denialism, and by no way it should be considered as particularly strange : Stern, Nordhaus, Tol and many other scholars are working on this question, in these terms. Maybe you dislike CB analysis, but as you know I’m a consequentialist, you won’t be surprised by this kind of request. 4) I dislike analogies and try to avoid them. But yours is interesting. You speak of a car (neutral) and a wall (harm). Your analogy is uncorrect as there is no cost to avoid the wall : the motorist is just stupid. In fact, a correct analogy would be something like : I’ve a house and I’m very attached to it, but there are floods threatening it and some suggest there could even be a tsunami. At which conditions must I leave my house for another one ? Here you have a real choice with costs on the two sides. And in real life, if you're obliged to leave your house, I bet you'll very strictly examine the details of the assertion about floods and tsunami, and the possibility to protect your house without leaving it. 5) I do not lack at all your second caveat concerning the fact that our current policies are not coherent (and in retreat) with the goal they defined themselves (remember the 2K/450 is a policy goal, not scientific one, point 3). In fact, it is precisely what I show : we clearly act as if the fossil benefits far outweigh the climate costs. Some say we do so because of lobbies, of conservatives, etc. I don’t agree with these kind of explanation, as I explained and illustrated by some examples. I suggest we act in this sense for many reasons, some bad (eg incapacity to project in the future, discount rate favorable to short term, 'know-nothing' and denialism of AGW, etc.) and some good (eg produce the material condition of decent life, create and trasmit wealth to future generations, etc.) 6) The rising price of fossil fuel is not a particular caveat of my position and it is a strange argument for those who want to increase by a mean or another the carbon price (by tax or by cap-and-trade like Kyoto). In fact, rising price of fossil fuels is a caveat of most SRES or RCP pathways, because none of them consider there could be a massive shortage in fossil supply during all the 21th century. It is a well-known critics of IPCC from Peak Oil defenders (like Jean Laherrère). This argument (I suppose against my position) is all the more so strange that a) I do not specially favor an inertial position on RE energy, because it is already competitive and would be more with a carbon price, and b) the example I gave for fossil fuels mainly concerned the ethical choices for less developed countries that have fossil fuel as a national ressource (India, South Africa, China, etc.). There are immune to great changes in fossil price if they exploit their own reserves. 7) The relative importance of energy to well being is not a sacrosanct point for me. It is an empirical observation we alreday discuss here on SkS and I’m totally open to a debate about that. If you show me a low energy period or country that could be reasonably considered as a model of welfare and a desirable example for policymakers and citizens, I would be happy to examine this case. Precision : the period or country in question should be on an enough long term to judge the diverse aspect and evolution of the quality of life. (For example, Cuba since the end of Soviet oil is a too short period, that is a classically bad example because all infrastructures of Cuba had been fossil-fuelled and we don’t know if the post-fossil Cuba will manage the replacement and modernization). 8) I think you have not the orders of magnitude in mind when you speak of the 1950’s USA standard as a universal goal. I’ve not the precise number for 1950 but as you can see on this graph , 1960 energy per capita was 5,5 tep. To be conservative, let’s imagine 3 tep in 1950, ten years before (in fact, the form of the curve suggest it should be more, probably 5 tep). 3 tep equals 126 GJ/c/y. A globalization of that condition would imply, for 8 billion persons (2030-2050), a 1008 EJ/y production. Of course, no energy scenario imagine such a high production, twice more than now. And certainly not without a huge part of fossil.

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