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Comments 45101 to 45150:

45101. gpwayne at 16:30 PM on 25 May 2013
       On the value of consensus in climate communication
       

       I'm wryly amused by this little spat, because all the protagonists seem to be operating in the famously closed world of academia - a gentle accusation that is characterised by the comment that the study "doesn’t meaningfully enlarge knowledge of the state of scientific opinion on climate change". My rebuttal to that point is that for those who do climate science, or study it from a lay perspective (e.g. me), scientific opinion is irrelevant to the actual science. There are no planks to my own arguments with contrarians that depend on opinion (wheras nearly all contrarian arguments are not only opinionated, but usually stated as fact). 

       My arguments depend in their entirity on published papers, the experiments designed to test them, and the evidence that supports them (plus the consilience of climate science with other disciplines, and with the foundational science on which it rests, and with which it must conform). 

       Yet this study is really important in my view, and to support that view I need to ask that we step out of the scientific community, and into the wider world. On arrival, we might find something disconcerting: while it would be nice to think that the issues we're discussing are about science, in fact the issue is something else entirely, something grubby and distasteful, something that I have found scientists and activists are very reluctant to engage with, and that is propaganda.

       We are at war. We didn't want it, but it was forced on us, by those who cannot or will not embrace the implications of the science, and by those whose interests are threatened by those implications i.e. fossil fuel companies. Since the demagogues have no science to back up their arguments, it is necessary to find other weapons with which to wage war, and these weapons are stamped out of molds all too familiar: attacks on credibility and probity, insinuation, misrepresentation, demonisation, conspiracy, and implied or asserted furthering of vested interest. These are the weapons of the ideologue, and what this study does is put an equivalent weapon in my hand - one I have no hesitation in pointing at the enemy, because I recognise that there is good propaganda as well as bad, and what little I contribute is, I hope, of the former kind. It certainly isn't science.

       It is also important to understand where this battle is being fought. It is taking place in the media; the paper itself demonstrates that it isn't taking place within the climate science community. And it isn't scientists waging this war - at best, I think scientists feel co-opted, as if they've been caught up in a bar brawl when they were just trying to get a glass of water. Reading Kahan's remarks, there is a sense of frustration and annoyance which he acknowledges, but frames in terms of some putative failure on his part, or on the part of those trying to improve the communication of science. This misses the boat: science will never, ever, convince the public to support political and economic measures to mitigate or adapt to climate change. They don't get it, don't get the compelling probabilities, don't get the causal chain, don't get the timescales or the rapid development, which often appears contradictory or equivocal.

       What the public do get is propaganda. They may not recognise it as such, but so powerful is the effect of the constant repetition that the public discourse is blighted and twisted out of shape, where black really can be made to appear white, where there is no nuance and no shades of grey, and where there is no such thing as a fact. And in this petty war, one of the facts most open to attack is the consensual nature of climate science, for the 'unsettled' science is, as John points out, not only Luntz's weapon, but that of the tobacco industry before it, and perhaps more emotively, the principle tool of the National Socialists in the 1930s. I won't repeat Goebbel's aphorism about propaganda, but I will point out the consistency between his application of it, and that of all ideologues who followed, of which Luntz is just one more professional liar.

       This is a very old debate: when does the means justify the ends? Previously, I've identified the problem as the 'Bomber Harris' paradox. Harris ran the RAF's Bomber Command and is held responsible for either shortening the war by firebombing German cities, or for destroying the moral credibility of the Allied forces by being as inhuman and evil as the Nazis. This debate carries echoes of the same issue: the denial brigade lie all the time, so we find it incumbent to be truthful. Deniers never admit mistakes, so we have to (as SkS did, bravely, this week - and of course got pilloried for it - was this honesty successful if success is measured in propaganda terms?).

       So there's the paradox: while science continues on its quiet course through the long days of number crunching and patient gathering of information, there is a dirty war raging outside. Scientists don't want to be like Harris, don't want to tool up and start burning stuff, and good job too. Leave the dirty work to the soldiers, but don't think this war will be won by science, by evidence, or by banging on about the consensus, for this paper is nothing more than our missile shield, our Patriots, our counter-intelligence. It's purpose is to sabotage the enemy's propaganda, and for that I'm thankful because I'm very short of effective weapons when science and evidence don't work. 

45102. DSL at 13:49 PM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       William Haas, scientific consensus of the sort that Cook has done is not evidence for the theory of anthropogenic global warming.  Rather it is an index of the scientific support that the theory has.  That index is used by people who don't have the time, energy, training, means, and/or motivation to engage the published science effectively.  That would be most people.  Like it or not, most people rely on opinion-makers for their opinions.  They're forced to.

       Question for you, William: do you understand my point?

45103. DSL at 13:45 PM on 25 May 2013
       On the value of consensus in climate communication
       

       jdixon, I rarely post intentionally on my wall.  Occasionally, I'll be on a thread somewhere and it will show up on my wall.  I want to be very careful with the friends and family I've allowed on my FB.  The best opportunities are when a friend of a friend makes an unscientific comment and I see it on the home stream.  I feel no resistance to correcting the person, and it keeps the friend in observer mode.  If the friend wants to discuss it, no problem.  I look for situations where I can start conversations.  It's very difficult, though, to keep the baseball bat that is the published science in my back pocket.  However, I sober up when I think about how insulated my friends are.  Most have not had a liberal education that has allowed them to stand back from it all for several years.  For most of my friends, I can read their opinions in the content of CNN and FOX.  That's not an insult; it's a reality.  FB is a liberalizing force, though.  The more contact we have with each other's brains and cultural situations, the better.  It is easy to de-friend, though, and that's why I walk softly, most of the time.

       The family is another matter.  My family (up-tree) is small and dying.  My in-laws are large and growing.  And stereotypically Southern (US) for the most part. Some will say one thing in conversation and then whisper something else behind the back.  It's very annoying to someone who likes and encourages transparency of thought.  I've had my sit-downs on climate with a few of them, the mother-in-law in particular.  Again, though, anger is of no use.  It often takes years for evidence to begin to change belief.  Fortunately, my sister-in-law is heavy into sustainable living and community development.  They think she's flaky, but she's cute and funny so they tolerate her "wierd side."  We do occasionally do FB team-ups with family members when they get too obnoxious.

45104. Glenn Tamblyn at 10:11 AM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       William Haas

       All science requires consensus. The oft used claim is that it is about evidence not consensus, which is actually a very confused statement.

       
       Of course it is about the evidence for something. Does the evidence support the hypothesis or not? To determine this one has to evaluate the evidence and form a conclusion, an opinion, about whether the evidence supports the hypothesis or not. And each individual forms their own opinion on this. You and I might look at the same evidence and form different opinions about whether that evidence supports the hypothesis. So whose opinion should we accept, yours or mine?

       All knowledge is a consensus of the opinions of many people about the significance of evidence. If a large number of people share the same opinion that the evidence supports the hypothesis, we tend to accept that it does.

       Was the proof of Fermat's Last Theorem a few years back a valid proof? Yes, because that was the consensus of the many mathematicians who evaluated the proof.

45105. Tom Dayton at 09:42 AM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       William Haas, you should read the post "Is There a Scientific Consensus on Global Warming?" to understand what is meant by "consensus."  To make your example from mathematics applicable, you must address mathematicians' consensus on whether that single counterexample really does invalidate a theorem.  If you believe that all mathematical counterexamples are correct, you are living in a fantasy world.

45106. William Haas at 09:36 AM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       The case for AGW must be really shaky if a "scientific consensus" is required to substantiate it.  "Scientific consensus" is really an oxymoron because true science does not require a consensus.  The idea of voting on scientific truths seems totally alien to me.  It is just like the political entity that voted to change the value of pi.  In mathematics it takes only one counterexample to invalidate a theorem.

45107. John Russell at 09:20 AM on 25 May 2013
       On the value of consensus in climate communication
       

       One only needs to see how often the consensus is brought up as an arguing point by those in denial to know that this new paper has great value when it comes to the politics of climate change.

       But clearly it's neither here or there when it comes to the work of climate scientists trying to pin down the likely outcomes of steadily raising the planet's atmopheric CO2.     

45108. Dikran Marsupial at 08:33 AM on 25 May 2013
       It's cosmic rays
       

       JRT256: Firstly sun-spot numbers are correlated with total solar irradiance (TSI) as well as cosmic rays.  So a correllation between sunspot numbers and climate does not necessarily involve cosmic rays as the causal mechanism.

       Secondly, a link was provided to the "body of scientific research has determined that GCRs are actually not very effective at seeding clouds."  (i.e. the advanced version of the article).  The cosmic ray theory is not unlikely to be correct because it doesn't explain all warming, but because of the scientific research that has been performed has identified several problems with the causal mechanism,  If you want to discuss the details of any of the papers mentioned, I'm sure there will be plenty of contributors willing to discuss them with you.

       "it is more reasonable from a scientific point of view to try to figure out why the correlation broke than to use this fact to try to prove that the hypothesis is false."

       Actually, the most plausible theory is that there is more than one forcing that affects climate; changes in total solar irradiance and the rise in greenhouse gasses explains the breakdown in the correlation pretty well.  However, proving hypotheses to be incorrect is a fundamental part of scientific method.  Ruling out hypotheses is a good a way of finding out why the correllation broke down as any.

       Lastly, as a word of advice, if you want to have a discussion of science, starting by using phrases such as "That is both unscientific and fallacious reasoning." when you yourself obviously have not understand the argument put forward in the article is unlikely to be conducive to constructive dialogue.  Note I have taken pains to reply in a rather more civil manner.

45109. JRT256 at 07:57 AM on 25 May 2013
       It's cosmic rays
       

       IIUC, you are denying the scientific hypothesis that there is a correlation between sunspot numbers and climate on earth.  Your argument appears to be that because this hypothesis doesn't account for all global warming, that it doesn't account for any global warming.  That is both unscientific and fallacious reasoning.
       
       We have history that provides strong evidence that this hypothesis is correct.  The Maunder Minimum and the Little Ice Age being most significant.  Still, it is true that we do not completely understand the action mechiism.
       
       You are correct to point out that this correlation broke in the second half of the 20th century.  However, since it has been so strong historically, it is more reasonable from a scientific point of view to try to figure out why the correlation broke than to use this fact to try to prove that the hypothesis is false.
       
       Might I suggest one possible cause which is CFCs.  It is now belived that CFCs had a stronger effect on global warming than was once thought and their concentration in the atmosphere, taken as a factor (possibly with a delay in time) allong with the sunspot number as a proxy for solar activity in factor analysis might yield a reasonable answer to the question.

45110. DSL at 07:15 AM on 25 May 2013
       It hasn't warmed since 1998
       

       Chemasan, the methodology of Levitus et al. (2012) includes Argo data.  Go here to see the results.  If you choose Jan-Mar on any of the 3-month sets, you'll get up to 2013.  I strongly suggest using the 0-2000m set.  Here's global 0-2000m for all months:

       2005-3 8.972987
       2005-6 9.391529
       2005-9 9.681848
       2005-12 12.636982
       2006-3 11.932278
       2006-6 12.998004
       2006-9 12.264493
       2006-12 13.356965
       2007-3 13.49815
       2007-6 11.382808
       2007-9 12.277043
       2007-12 12.418795
       2008-3 13.305184
       2008-6 14.606297
       2008-9 13.024848
       2008-12 12.090649
       2009-3 12.614719
       2009-6 12.241169
       2009-9 13.816815
       2009-12 15.052814
       2010-3 15.881298
       2010-6 13.484779
       2010-9 13.959781
       2010-12 14.823184
       2011-3 15.215552
       2011-6 14.630487
       2011-9 16.870249
       2011-12 14.859973
       2012-3 17.308126
       2012-6 15.461417
       2012-9 15.34632
       2012-12 16.630146
       2013-3 19.332438

       The annual running average produces a linear trend of +1.74*10^21 joules added per year.  

45111. Chemasan at 06:50 AM on 25 May 2013
       It hasn't warmed since 1998
       

       For #40 and #50. Have you check Argo Project? It seems NO. Argo project the most serious study of the T and sea levels didn't observe increase in the T. It's true that it a new project (since 2005) but data is more accuracy.

       Moderator Response:

       (Rob P) You can use the search function to find a response to most climate-related questions. For example on the observed warming of the oceans:

       1. Ocean Cooling Corrected, Again

       2. Levitus et al. Find Global Warming Continues to Heat the Oceans

       3. Nuccitelli et al. (2012) Show that Global Warming Continues

       4. Observed Warming of the Ocean and Atmosphere is Incompatible with Natural Variation

       5. New Research Confirms Global Warming Has Accelerated

45112. R. Gates at 06:08 AM on 25 May 2013
       A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
       

       William,

       That rising air and positive AO mght indeed happen (especially in the warmer months), in which case we might get more storms like the Great Arctic Cyclone of 2012 (early August 2012, to be exact).  These storms not only bring up warmer water from depth, but also draw in more energy to the Arctic via the atmosphere as the strong low pressure pulls in wamer air from lower latitudes. 

       But there is another huge dynamic that I mentioned in my post #12 that must not be forgotten-- and that's the effects of SSW's on the AO.  These events, happening mainly from late November through February, begin high above the Arctic, and with the warm descending air, turn the AO very negative, and push the colder air out of the Arctic and we ususally see warmer than normal temps in the Arctic proper.  Most importantly, the causes of these events begins at lower latitudes, and are related to large-scale planetary waves whereby we can see the same SSW event having simultaneous (though opposite) effects over the pole and over the equator, 9000km away.

45113. Rob Honeycutt at 04:54 AM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       Thanks Tom.  I'm actually less stuck on the specific 97.1% figure that it may seem.  The fact that all this research, taken collectively, and taking the fact that Cook13 is such a large sampling of research, should tell people how robust the conclusions actually are.

       Again, I would challege any other group to perform a similar research project, using their own wording, and see if they can come up with appreciably different results.  The point being, Barry, Lucia, Schollenberg and others can quibble until the cows come home, but until they do their own research (and get it published) they have little ground to stand on.

45114. Tom Curtis at 02:55 AM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       Very briefly, all participants in this debate would do well to read Bray and Von Storch 2010 (particularly question 21, which shows that in 2008, 83.51% of climate scientists where significantly convinced that "most of recent or near future climate change is, or will be, a result of anthropogenic causes").  Note that this is not inconsistent with Cook et al 2013 because (a), climate scientists "convinced by the evidence" publish approximately twice as many papers on climate science on average relative to those unconvinced by the evidence (Anderegg et al, 2010), and (b), those not significantly convinced may well not be convinced for reasons other than the weight of evidence, and hence lag in proportion the balance of evidence as seen in the literature.  It should place a constraint on the over interpretations and the absurd underinterpretations of Cook et al 2013.

45115. Alexandre at 02:51 AM on 25 May 2013
       Matt Ridley's misguided climate change policy
       

       Lomborg is a slippery guy. He hardly claims anything, while conveying the unmistakable message that fossil fuels are all we need, and the environment is doing fine, and why do we have to conserve biodiversity after all?

       He does not say we shouldn't stop deforesting, but he claims that worries about deforesting are grossly exaggerated, and even misrepresents the FAO report to prove it once and for all.

       He does not say global warming is a hoax, but he knows of a climate model that miscalculated how much stratospheric warming there would be and, you know, that's what really matters.

       He does not say we should not manage water resources properly, but he assures us that dessalinization is a definite safety net to dismiss any claims that people would ever endure water shortage.

45116. Tom Curtis at 02:44 AM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       This debate is getting irritating beyond belief, so I'll take advantage of a moments insomnia to stick my oar in.

       Barry, you have shown that it is possible that authors used a more relaxed rating system than did the Consensus Project raters.  You have not shown that using the more relaxed rating system significantly increases the number of  papers rated as affirming the concensus, nor even that a significant number of authors used the more relaxed rating system.  Even if half of papers self rated as affirming the consensus are given a neutral rating, the support for the consensus from self rated papers remains at 94.5% of all relevant papers.  That shows how robust the results of the paper are; and that you must not just show the mere possibility of but the actuality of a difference in rating >>50% of affirmations if you wish to call the results into question.  To my knowledge, no critic of the paper has even attempted to do so.  At most they have argued for the mere possibility a less robust definition of "affirms agw" and then assumed that therefore >>50% of rated affirmations should have been rated neutrals.

       Rob (and others), the near match in percentage of abstract rated and self rated papers rated as affirming the consensus (from relevant papers) is a product of a 1.9 fold increase by percentage of papers rated as affirming the consensus, a 2.6 fold increase by percentage of papers rejecting the consensus, the lack of a category for papers uncertain of the consensus, and an increased rate of return on recent papers (more likely to affirm the consensus) than older papers (which are less likely to affirm the consensus, particularly prior to 1995).  Given that, it should largely be considered coincidental.  What is robust about this result is not the 97%, but the 95%+ of papers which is difficult to eliminate by varying the data to account for potential biases.

       I look forward with interest to further developments in this debate, and to when I have sufficient time to actively participate again.

45117. jdixon1980 at 01:55 AM on 25 May 2013
       On the value of consensus in climate communication
       

       DSL, I noticed you mentioned FB - do you post a lot about AGW on your own timeline?  If so, what has been your experience with the result of it?  

       In my case, I have been posting something about AGW impacts, green tech/policy developments on my timeline just about every weekday for the past several months (sometimes reposts from here, sometimes from David Roberts at Grist, sometimes from RenewEconomy, etc.).  I think it results in some of my closer friends who are not "skeptics," but just aren't as independently interested in the subject as I am, reading more about AGW than they otherwise would because they see on their "news feed" that I posted something.  Another effect is that a couple of my FB friends who are "skeptics" or "lukewarm skeptics" occasionally comment on my posts or even post their own links on my timeline, leading to discussions that my other friends often follow and chime in on.  I don't think I've made a tremendous impact on the "skeptics."  The closest thing to progress from a "skeptic" friend of mine was when he first posted (in his own WordPress blog) a reference to global warming as a "specious concept," and then in a later post of his musings on the theme of devoting our attention to the problems of the day, stated that for example he could donate to a global warming awareness organization, but he is "not convinced that climate change is a legitimate issue."  

       Going from proclaiming AGW as a "specious concept" to being "not convinced" is arguably some movement.  But what mainly motivates me to post on FB is to use my timeline as a kind of "information hub" for the benefit of my friends and for my own benefit as well - I have a kind of half-baked organization scheme where I sometimes post related articles in the comments to a a previous article, for later reference...  

45118. Rob Honeycutt at 01:27 AM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       HJones @209...  But I believe with such a large data set, if there were a weakness it would have presented itself as pretty obvious.  The big difference you see between the SkS raters and the self-ratings is that there are far fewer neutral papers.  And that makes sense because the SkS raters were not reading the full papers.  

       The fact that the consensus figures for the SkS raters and the self-ratings are nearly identical suggests a high level of robustness in the results.

45119. Rob Honeycutt at 01:20 AM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       Barry @208...

       You are presenting a subjective analysis of what you believe about the survey which is going to reflect your personal biases.  This is why science doesn't rely on any one piece of research to be the definitive answer on any question.  We are all subject to our personal biases.  

       What makes Cook13 important is the fact that the conclusions independently confirm the previous research of Doran, Oreskes, Anderegg and others.  Cook13 was also sufficiently blinded so that it would have been impossible for the raters to inadvertantly bias the ratings to come up with the same figures of previous research.  And the data set is sufficiently large enough to also prevent biasing. 

       Then, on top of that, Cook13 took the added step of being self-skeptical by asking scientists to self-rate their own research based on the definitions used in the study.  And the results there came out nearly identical with a 97.1% vs 97.2% consensus.

       Could all these pieces of the puzzle falling exactly into place be completely happenstance?  Highly unlikely! 

       Beyond that, it would be up to you, Barry, to come up with what you determined to be  less ambiguous phrasing and then test your results.  Based on how consistent these results have been I would guess any data you could compile would not be sufficiently different that those of any of these studies.

45120. jdixon1980 at 01:10 AM on 25 May 2013
       On the value of consensus in climate communication
       

       I think this statement by DSL @1 is thought-provoking, and so I am going to take the liberty of plucking it out and repeating it, lest it get lost. It's only human to quickly skim through a multi-paragraph comment and maybe miss a gem like this:  

       "More powerful than ideology is the need to remain valuable, and that need is amplified when the discussion is public. No one wants to be dismissed out of hand--to be categorized, labeled, boxed, stamped as innocuous."

45121. HJones at 01:08 AM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       barry & John Hartz,

       If enough respondants had a different ratings criteria to others, then the apparent corroboration between the 2 groups is undermined, weakening the results.

       Another factor that can weaken the results is the fact that the authors were rating their papers, while the raters were rating the abstracts.  Unless someone were to go through and re-evaluate some papers and check against the abstract rating, this level of weakenning will remain unknown.

45122. barry1487 at 00:37 AM on 25 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       John Hartz,

       I have posted my thoughts on the paper upthread.

       I think that the survey definitons are ambiguous, such that the criterion for rating the papers may have been different between the authors of the study (Cook et al), and the original Authors (the ~1200 that responded to the email and self-rated their papers).

       The close match in ratings between the authors and the original Authors is a centrepiece of the corroboration of the results. If enough respondants had a different ratings criteria to others, then the apparent corroboration between the 2 groups is undermined, weakening the results.

        

45123. Dikran Marsupial at 20:12 PM on 24 May 2013
       The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
       

       Prof Tung, regarding your most recent post:  As I said, I think SkS readers are familiar with the idea of internal variability and would readily agree that internal variability is most likely the cause of the apparent hiatus.  However, the abstract of your paper in JAS makes the claim that:

       When the AMO index is included as a regressor (i.e., explanatory variable), the deduced multidecadal anthropogenic global warming trend is so impacted that previously deduced anthropogenic warming rates need to be substantially revised.

       This is advancing a much stronger claim than that the hiatus is mot likely due to internal variability, but that some of the action of AMO has been misattributed to anthropogenic forcing.  The only quantative support for this assertion seems to come from the regression model.  In my example on the other thread I have shown that this regression model is flawed, and if AMO actually doesn't affect global mean surface temperatures (in your notation, the correct value of the regression coefficient D is precisely zero), then the regression method can misattribute some of the effects of anthropogenic forcing to the AMO.

       In an earlier post, Prof. Tung wrote:

       "The MLR analysis cannot stand on its own as evidence."

       The MLR analysis is clearly the key element of the paper in JAS entitled "Deducing Multidecadal Anthropogenic Global Warming Trends Using Multiple Regression Analysis".  For that paper to be sound, it is incumbent on you to be able to refute the counter example I have provided that shows the method is unreliable.

       "I also mentioned in part 2 of my post that one could legitimately claim that use of either the Enfield AMO index or the Trenberth and Shea index is ciruclar, if that is the entirety of the evidence that you presented."

       Enfield and Trenberth & Shea would only be circular if they used their detrended AMO indices to deduce the anthropogenic influence on global temperatures.  There is nothing circular about detrending AMO to remove anthropogenic influence, the circularity is introduced by assuming a model of anthropogenic warming to detrend AMO and then using that detrended AMO to deduce the anthropogenic warming.

       "Similarly, as you have done here, you assume the hypothetical case that the AMO is anthropogenically forced, but you do a MLR assuming it is instead mostly natural and remove it."

       No, this is clearly not the case.  In my example the AMO signal is a mixture of anthropogenic and natural.  The point is that the detrending procedure, whether lienar or quadratic affects both the anthropogenic and natural components of the AMO signal.  As a result the detrended AMO can still act as a proxy for anthropogenic warming, either because the detrending model was incorrect (in the case of lienar detrending) or becase the natural component is correlated with the anthropogenic signal (in the case of quadratic detrending).

       "You can then demonstrate that the resulting anthropogenic response is wrong. That is, it is different than you originally assumed to be true."

       The whole purpose of using a synthetic example is that I know that the resulting anthropogenic response is wrong as I know what the correct answer is by construction.  The MLR method gives the wrong answer unless the AMO is detrended to remove the anthropogenic signal exactly, which can't be done unless you know what the anthropogenic signal is a-priori.

       Conversely, if you consider the hypothetical case that the AMO is mostly natural, but you do not remove it, you would also get a wrong anthropogenic response in the end. This you could have known even before you do the Matlab calculation.

       The AMO signal in my example is mostly natural.  If the MLR method is sound, it needs to work whether the AMO is strongly affected by anthropogenic factors or not, and whether AMO affects global surface tempertures or not. 

       It is very important that you provide me with a direct answer to this question, so we can focuss in on the area of disagreement quickly:  Ignoring for the moment whether the hypothetical scenario is appropriate, is there an error in my implementation of the MLR method?  "Yes" or "No", if "Yes", please explain.

45124. MA Rodger at 20:06 PM on 24 May 2013
       The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
       

       KK Tung @111.

       Thank you for pointing out the mention of the 'hiatus' in T&Zh13. It had passed me by. The actual quote is:-

       
       "Recently, there have been debates about the slowing of the warming rates since 2005, with explanations (44–46) ranging from increases in stratospheric water vapor and background aerosol to increased coal burning in the emergent economy of China of the past 20 y. If one accepts the conclusion that the AMO is recurrent, and because this period coincides with the start of the descending phase of the AMO, one can suggest that the AMO is a more likely explanation."

       
       In the first post here at SkSci, there was also the statement that the residuals following MLR with QCO2(t) function showed "a minor negative trend in the last decade" ie during this same  'hiatus' period'. Indeed, is this "minor negative trend" as shown in fig 3 of the first post not the 'hiatus' iself that remains unexplained by T&Zh13 when the actual AMO is used (although explained with a theoretical "recurrent" AMO.)?

45125. JasonB at 19:46 PM on 24 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       s_gordon_b,

       Rob, again, based on my reading of the paper (please correct me if I'm wrong), your statement that the paper indicates that "97% of the research supports AGW" is the right conclusion. But that's not how the study is being (forgive me) spun.

       Perhaps it would be easier to understand your point if you could point us to some examples of where the study is being spun?

       Regarding the authors, again, they were asked to state whether each specific paper endorsed the proposition that anthropogenic GHGs are causing global warming, rejected the proposition that anthropogenic GHGs are causing global warming, or was neutral. If the author of the paper felt that their paper implied humans were having a minimal impact on global warming (e.g. by proposing an alternative as the main cause of global warming), or stated that human impact was minimal or non-existent, or stated that humans were causing less then half of global warming, then they would have categorised their own papers as rejecting the proposition.

       I'm fairly confident that anyone who rejected the consensus view would have made damn sure their paper was counted as a rejection if it was at all possible to do so! And let's not forget that the authors of any papers who feel their paper should have been counted as a rejection are free to search for their paper in the results and alert us to the miscategorisation.

       Anyway, the bottom line is that the authors of 97.2% of the papers that took a position stated that their papers endorsed the proposition that anthropogenic greenhouse gasses are causing global warming. That's it.

       *I've looked everywhere, but I can't find where the numbers of abstracts assigned to each of the original Table 2 categories is or the category assignments by the study authors. Could you point me to that data?

       http://www.skepticalscience.com/tcp.php?t=search

       Perhaps you should spend some time reading the earlier comments to avoid rehashing the same points over and over again.

       For a summary of the category assignments extracted from the database, see my earlier comment. The bottom line is that, ignoring neutral papers, the percentage of papers that endorse the consensus in each category are:

       Papers that quantify the human contribution to global warming (i.e. level 1 vs level 7): 88%

       Papers that make explicit statements about causation without quantification (2 vs 6): 98.4%

       Papers that imply the impact that humans are having (3 vs 5): 98.2%

       If we ignore all papers with implicit statements about the impact humans are having and only include those that make explicit statements about causation with and without quantification then we get 97.6%.

       No matter which way you cut it, the results keep coming up the same.

45126. nealjking at 19:12 PM on 24 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       s_gordon_b:

       As stated above, my interpretation of the meaning of the consensus is:

       "Not that the human contribution is necessarily greater than 50%, but rather that it is important enough that we should be seriously thinking hard about whether we want to change what we are doing, on a global scale."

45127. s_gordon_b at 18:14 PM on 24 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       I keep submitting this, but it keeps not showing up. I'm sorry if it ends up appearing in triplicate:
       
       Rob, again, based on my reading of the paper (please correct me if I'm wrong), your statement that the paper indicates that "97% of the research supports AGW" is the right conclusion. But that's not how the study is being (forgive me) spun. Evidence of 97% support/endorsement of a mostly* unquaintified degree of human causation (not the consensus) is being conflated with evidence of a 97% agreement with the consensus of predominant human causation. We criticize deniers and contrarians - indeed, SkS excels at this - for such sleights of hand. We should apply the same standard to "our" research. It's a good study, but unless someone can explain how and why I (and others who I now see have raised the same question) have got it wrong, the presentation of the study is not good.

       The study also attributes agreement with the consensus to >97% of the authors, based on their ratings (from the anstract: "Among self-rated papers expressing a position on AGW, 97.2% endorsed the consensus"). Reading the paper and the supplementary data, it again appears that the authors' 1-7 ratings were then aggregated in the same way as the reviewers' ratings, potentially conflating the popular (non-consensus) view that "people are at least responsible for some of the warming" with the consensus of the IPCC and, I think it's safe to guess (but not from this paper), most climate scientists.**

       *I've looked everywhere, but I can't find where the numbers of abstracts assigned to each of the original Table 2 categories is or the category assignments by the study authors. Could you point me to that data?

       **It's too bad the authors weren't asked for their views on the consensus, apart from what their papers had or had not said. The last survey had answers from less than 100 climate scientists. This study's sample size of ~1200 would probably have included hundreds more or even all of them, inasmuch as they were publishing papers on climate science regardless of their discipline.

       Moderator Response:

       [JH] The two prior duplicate posts have been deleted.]

45128. william5331 at 16:29 PM on 24 May 2013
       A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
       

       It should be interesting when the Arctic is ice free for three or four months of the year.  We should see rising air over the arctic and the mother of all positive AO's.  If the jet stream is weakening even now, will it disappear all together and a two cell system develop in the northern hemisphere.  Perhaps this explains the observation of hemlock pollin 3.6m years ago in that unpronouncable impact lake in Russia.  A persistant low over the Arctic much of the year would reverse the Beaufort gyre, flinging the surface cold somewhat fresh water in to the Transpolar drift and out through the Fram Straight.  Once the ice is gone and the halocline greatly reduced, it would be hard to reestablish ice cover.

45129. citizenschallenge at 15:14 PM on 24 May 2013
       A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
       

       Nice post post John.  

       I found that it shoe-horned with a recent happening in the states where a Senator Whitehouse gave a strong speech about global warming and extreme weather, while the Moore OK tornado was happening.

       Of course Republicans are trying to twist what happen and what he said.  

       In any event, thank's again for allowing us to repost these articles:

       Thursday, May 23, 2013

       "Explaining why Senator Whitehouse's claims are accurate"

       In light of Senator Whitehouse's claims, I thought this lesson, based on up to date information - explaining what scientists are observing within the Arctic Circle and the implications of those observations.

       It's a recent post from SkepticalScience.com that has the most comprehensive collection of digestible information I've seen to date about our Jet Stream. Considering how much the Jet Stream influences weather this is an informative article that should be read as supplement to Senator Whitehouse's attempt to wake up Republican Senators to the stakes they are gambling away.

       Thanks again to SkepticalScience.com for making these posts available to folks like me.

       ===========

       Also:

       "Senator Whitehouse and the Moore Oklahoma tornado"

       http://whatsupwiththatwatts.blogspot.com/2013/05/senator-whitehouse-and-moore-oklahoma.html

45130. JasonB at 12:56 PM on 24 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       There is a reason why the email asked the original authors whether their paper endorsed such a simple, "common speech" statement without definitions of each word — it's so that their answer can be reported to the general public in the same terms.

       Actually, there was one definition: "human activity (i.e. anthropogenic greenhouse gases)". This narrowing of "human activity" to just anthropogenic GHGs allows them to state that the consensus relates to GHGs without anyone being able to muddy the waters by claiming that some scientists might have been talking about other activities like land clearing.

45131. Riduna at 12:54 PM on 24 May 2013
       Matt Ridley's misguided climate change policy
       

       Climate sensitivity is found by the IPCC to be ~3.5C, a value confirmed by paleoclimate studies undertaken by Hansen and others and is widely accepted. Dr Otto et al, using data covering a relatively short period (too short?) has found that sensitivity appears to be significantly lower.

       Ridley concludes from this that public policy on curbing anthropogenic carbon emissions is misplaced, damaging and should be slowed. He comes to this conclusion without accurately quantifying and estimating the effect of slow feedbacks over next 87 years of this century or their capacity to fully off-set the Dr Otto's findings by 2100.

       Those feedbacks include loss of albedo, methane and carbon dioxide emissions trapped in and under permafrost and increased water vapour due to atmospheric warming. Nor can we ignore increasing ocean heat content and the likelihood of its release to the atmosphere, accelerating feedbacks.

       The speed with which feedbacks are now developing is more likely to increase rather than lower the rate of global warming. To interpret the findings of Dr Otto et al as indicating that we may have a decade or so longer in which to curb anthropogenic emissions is, in my view, the height of folly.

45132. Eric (skeptic) at 12:13 PM on 24 May 2013
       A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
       

       R Gates, I think my question also applies to SSW, but it may not.  It appears that models have improved a lot in coupling the stratosphere to the troposhpere.  The theory of SSW includes many factors including solar plus feedback with weather in the troposphere and ozone in the stratosphere.  The feedback with the troposphere could include some changes due to a decreased tempeature gradient from global warming but generally the gradient is so large during these events it is hard to imagine an impact from that long term trend.  Also difficult because those events are relatively rare.

       Chris, that makes sense although I'm not sure of the implications for the positioning and strength of the polar jet. 

45133. JasonB at 10:27 AM on 24 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       nealjking,

       In my view, it has to be understood as "common speech"

       Precisely. There is a reason why the email asked the original authors whether their paper endorsed such a simple, "common speech" statement without definitions of each word — it's so that their answer can be reported to the general public in the same terms.

       Consider the fact that laws are full of such undefined terms, like "reasonable". Probably the most famous of these is the phrase "guilty beyond reasonable doubt". The reason that they don't tell you, as a jury member, how you are "supposed" to interpret that is precisely because they want you to bring your own definition to the table. Get a large enough group of people together and the opinion of the majority will be an effective "poll" on what the word is supposed to mean.

       Likewise, ask a few thousand scientists whether or not their papers endorse the proposition that human activity is causing global warming and you can be sure that the majority are going to interpret that in the same way as the majority of the populace. It doesn't matter if a few scientists here and there have odd interpretations, or a few members of the public have odd interpretations, overall they will agree.

       The only exception to this rule is when the scientists have a reason for systematically interpreting it differently to the general population, and in this case it could well be true, because these scientists are climate scientists, and they can hardly be unaware of the IPCC's statement of consensus, which is that "human activity is very likely causing most of the current GW". Given that, it is entirely reasonable to assume that those scientists answered an even stronger interpretation of the statement than what the general population would assume it to mean, but this possibility does no favours to those who wish to nitpick.

       The bottom line is that several thousand scientists, when asked to asses their own papers —  so there was no need for them to try to interpret what they wrote, they knew exactly what they were trying to say —  responded by claiming that 97.2% of those that addressed the question at hand endorsed the statement that human activity is causing global warming.

       This is profound for two reasons: 1) It shows that a large number of scientists, independently interpreting both the meaning of that phrase and their own papers, arrived at the same level of endorsement as Cook et al did looking only at their abstracts, and 2) it did so while at the same time enormously growing the percentage of papers that actually addressed the question, that Cook et al were forced to categorise as "neutral". Incredible.

       Arguments over whether levels 2 or 3 endorse the proposition that humans are the "dominant" cause, or a "signficant" cause, or "> 50%", are seriously missing the point, just like those insisting that "reasonble" be precisely defined. If the scientists wanted to convey lesser degrees of human involvement, they could have chosen level 5, or level 6, or level 7, depending on how it was conveyed in their paper. The fact that the overwhelming majority of them didn't speaks volumes. Levels 2 and 3 cannot be read in isolation, and the fact that both have the worse "endorse" in the title cannot be ignored.

45134. KK Tung at 07:18 AM on 24 May 2013
       The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
       

       In reply to post 104 on the relevance of the recent hiatus to the present thread on the Tung and Zhou (2013) paper:  That paper offered one possible explanation for the observed hiatus observed since 2005, as due to a recurrent internal variability. Therefore it is relevant (thank you, Dikran, for pointing this out in post 105). There are many other suggestions, including coal burning in the emergent economy of China (Kaufmann et al. [2011] ), increases in stratospheric water (Solomon et al. [2010] ), or increases in “background” stratospheric aerosol (Solomon et al. [2011] ). I in no time suggested that ours is the only explanation.  The most recent explanation is that the heating from the greenhouse gas induced radiative imbalance goes into the deep ocean.  There are two timely paper by Jerry Meehl and his co-workers: One is published in 2011 in Nature Climate Change,vol 1, page 360-364, entitled : "Model based evidence of deep ocean heat uptake during surface temperature hiatus periods". The other is currently under consideration at J. Climate, entitled "Externally forced and internally generated decadal climate variability associated with the Interdecadal Pacific Oscillation".  They are very relevant to our current thread.
       

       Meehl et al used CCSM4 model run with a future scenario (RCP4.5), which does not have oscillatory variations in the forcing or dips such as those by volcano eruptions. With smooth forcing, the 5-member ensemble mean model global mean temperature is also smoothly increasing.  However the individual members show variability about the mean of around 0.5 K from peak to trough.  These papers are not about how good the model is in comparison with observation.
       

       From an energy balance standpoint, the top of the atmosphere radiative imbalance driven by the anthropogenic forcing should be accounted for mostly by the heat uptake in the oceans, as land and ice have much lower heat capacity.  In the model this heat budget can be done exactly.  Meehl et al defined the hiatus period as when the surface temperature has a negative trend even in the presence of increasing radiative driving. They found that during the hiatus period, the composite mean shows that the upper ocean takes significantly less heat whereas the ocean below 300m takes up significantly more, as compared with the non-hiatus period.  The second paper compares hiatus periods with accelerated warming periods, and finds the opposite behavior: the upper ocean takes up more heat and the deeper ocean much less.
       

       The question is, what causes some periods to have more heat going into the deep ocean while some other periods the heat staying more in the upper ocean?  I suggest that this is caused by the internal variability that we were discussing earlier.  Our previous exchanges hopefully established the viewpoint that we should view the ensemble mean as the forced solution and the deviations from the ensemble mean by each member as internal variability.  There are no hiatus periods in the forced solution under the CCSM4 RCP4.5 experimental setup.  In fact this solution is smoothly increasing in its global mean temperature.  It is the internal variability, possibly associated with variations in the deep overtuning circulations in the oceans, which determines when a portion of the heat should go to the deep ocean and show up as warming hiatus,  and when it should stay near the surface, and show up as accelerated warming. ENSO, which we generally view as internal variability, also has this kind of vertical distribution variability in the oceans: In La Nina, the upper ocean is cool while the heat goes to the deeper ocean, and opposite behavior in El Nino.
       

       The CCSM4 is known to have internal variability that is faster than in the observation.  Instead of having hiatus periods of about 2-3 decades in the observation its cooling periods last 1-2 decades.  This may possibly be caused by too rapid a vertical mixing in the ocean but I do not know for sure.  The Interdecadal Pacific Oscillation (IPO) that was discussed by Meehl et al is the low frequency portion of the Pacific Decadal Oscillation (PDO). In the observation the IPO cooling periods coincides with the cooling periods of the AMO, which led me to suspect that the IPO is just the Pacific manifestation of the AMO, which is caused by the variations of the Atlantic Meridional Overturning Circulation.
       

       
       

45135. From Peru at 06:41 AM on 24 May 2013
       Matt Ridley's misguided climate change policy
       

       "committed climate change damage of $2.4 trillion, or over 3% of the global gross domestic product"

       Well, this cost depends on the social discount rate r (among a lot of other variables) the lower the social discount rate, the higher the cost:

       Present value(cost) of pollution = Σ (future damage of year i)/(1+r)ⁱ......(summed over i; i is the number of years in the future)

       But the social discount rate is a function of economic growth:

                                                   r = δ +γ g,

       Where:

       • r is the discount rate
       • δ is the so-called "rate of impacience"
       • γ is a parameter called " aversion to intertemporal inequality"
       • g is economic growth

       [source: Christian Gollier, Pricing the future:The economics of discounting and sustainable development, Toulouse School of Economics, 2011]

       δ is set to zero for intergenerational timescales, leaving r as just a function of γ and g.

       Now if the economy is seriously damaged by climate disasters, g will turn smaller, lowering the discount rate and so raising the present value of future damages.

       I don't know how low can the discount rate fall. So:

       Could it fall below zero, making the present value of damages to skyrocket?

       Is this subtle effect accounted when the cost of CO2 is calculated?

45136. John Hartz at 06:38 AM on 24 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       @Barry 201:

       Speaking for myself, I do not find it terribly useful for you to define one gneral term, i.e., academic merit, with another general term, i.e., quality of scholarship. What is generally accepted set of standards which are associtaed with these terms? (Source please.)

       In your opinion, which of the standards were violated by Cook et al 2013?  

       Do you believe that the editors of Environmental Research Letters deliberately ignored  certain standards when they published Cook et al 2013?

45137. Chris Colose at 06:19 AM on 24 May 2013
       A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
       

       Eric #9

       
       The mechanisms behind jet changes (strength, latitudinal shifts, etc) are still pretty hot topics in dynamical meteorology.  I tend to agree, however, that increases in the upper tropospheric pole-to-equator temperature gradient may be more important than the (fairly shallow) decrease in surface pole-to-equator temperature gradient. 

       In fact, because the tropopause slopes downward as you move poleward, if you are floating at a fixed level in the atmosphere near the tropical tropopause you are initially in a region of strong warmer (the "hotspot") but if you moved polewards at that level, you'd eventually end up in a region that was cooling in a global warming scenario.  That has a lot of implications for dynamics, since gradients in wind velocity are directly proportional to horizontal temperature gradients.

45138. MA Rodger at 06:10 AM on 24 May 2013
       The anthropogenic global warming rate: Is it steady for the last 100 years?
       

       So where to look for evidence of AMO warming beyond the shores of the N Atlantic?

       My first thought was that if AMO was going to effect temperatures anywhere, it would be the UK. Indeed, the CET was invoked within T&Zh13. So I compared CET with the SST for the surrounding seas (45-65N, 20W-10E) with nomad3 providing monthly SST data - 1981 to date. The two temperature profiles are re-based for comparison and graphed below. with AMO also plotted (although AMO is of course subject to a de-trending).

       The divergent record is evidently CET not the SST which suggests that during these divergent periods, AMO is not in any way a dominant influence in CET. So are divergent periods infrequent such that the period 1988-2004 is the norm where SST & CET can be married together?

       

       A de-trended CET for the period of Enfield's AMO index (1856 to date) is next up for comparison being graphed below. Divergence appears the normal state here, with the two indices have little in common. I would conclude that the CET record does not support the suggestion that AMO drives UK temperatures.

       
       Still. It's early days. There may yet be that local variation is swamping the signs of the AMO driving UK temperatures. And the UK is not the whole globe.

45139. Dumb Scientist at 05:56 AM on 24 May 2013
       The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
       

       As I discussed in part 2 of the post, the MLR analysis follows the arguments laying out the evidence in favor of the AMO being mostly natural. [KK Tung]

       Again, I don't think that's the issue. Removing the AMO to determine anthropogenic warming would only be justified if detrending the AMO from 1856-2011 actually removed the trend due to anthropogenic warming.

       The MLR analysis cannot stand on its own as evidence. If that were what we did in our PNAS paper, then our arguments would have indeed been circular.

       Those arguments aren't sufficient to support your claim that ~40% of the warming over the last 50 years can be attributed to a single mode of internal variability. Especially because Isaac Held and Huber and Knutti 2012 used thermodynamics to conclude that all modes of internal variability put together couldn't be responsible for more than about 25% of the warming.

       Similarly, as you have done here, you assume the hypothetical case that the AMO is anthropogenically forced, but you do a MLR assuming it is instead mostly natural and remove it.

       Actually, Dikran's analysis defines the AMO as 40% anthropogenic and 60% natural. So it is mostly natural.

       But again, I think the key point is that linear detrending doesn't remove the nonlinear anthropogenic trend from the AMO.

45140. KR at 05:46 AM on 24 May 2013
       The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
       

       Dr. Tung - I would agree that the identification of the AMO is critical for attribution analysis. I would disagree on the AMO index you used. 

       You used the CET as an AMO proxy - however the CET is equally vulnerable to aliasing (hiding) the global warming signal. Frequency analysis in this case is suspect, as the sum forcings in the 20th century (GISS forcings here), when averaged out by climate response times, have a frequency similar to that of the AMO observations - and are therefore not directly separable using just time series analysis. 

       ---

       I am in addition greatly disappointed that you have (as yet) failed to respond to my points regarding the Ting et al 2009 analysis (time/spatial principal component analysis supporting the Trenberth Shea 2006 detrending method, not linear detrending) or to ocean heat content thermodynamic constraints (upper limits on contributions from internal variation), as raised here. Either of these points indicate a much different anthropogenic contribution to current temperatures. 

45141. MA Rodger at 04:57 AM on 24 May 2013
       The anthropogenic global warming rate: Is it steady for the last 100 years?
       

       Dikran Marsupial @62.

       I can agree almost fully with your comment. Perhaps the use of Occam's razor needs wielding with care so it doesn't become Occam's broom (sweeping stuff under the carpet, out of sight).

       The point with the 'chipping away' idea is that just as CAN BE is distinct from IS, so it is also distinct from IS NOT. Thus, while our inabilities in removing the AGW signal from AMO would seemingly present an insurmountable problem for the T&Zh13 method, the question of how much of recent global warming is AMO and not AGW will remain unanswered.

       So I'm thinking of looking to see if there are signs of AMO warming beyond the N Atlantic, or signs of non-AMO warming. A tiny bit of harmless analysis. But frankly analysis that I feel should have been done already. Perhaps it has & I missed it. Perhaps not.

45142. KK Tung at 04:42 AM on 24 May 2013
       The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
       

       Regarding the Matlab code result of Dikran mentioned in post 106 and by DumbScientist earlier:

       I am frustrated that I have not been able to get my point across despite a few attempts, as you continue to focus on a technical procedure, the multiple linear regression analysis (MLR).  As I discussed in part 2 of the post, the MLR analysis follows the arguments laying out the evidence in favor of the AMO being mostly natural.  The MLR is then used to see the possible impact it may have on the deduced anthropogenic warming rate assuming that the AMO is mostly natural.  The MLR analysis cannot stand on its own as evidence.  If that were what we did in our PNAS paper, then our arguments would have indeed been circular.

       I also mentioned in part 2 of my post that one could legitimately claim that use of either the Enfield AMO index or the Trenberth and Shea index is ciruclar, if that is the entirety of the evidence that you presented.  Similarly, as you have done here, you assume the hypothetical case that the AMO is anthropogenically forced, but you do a MLR assuming it is instead mostly natural and remove it.  You can then demonstrate that the resulting anthropogenic response is wrong.  That is, it is different than you originally assumed to be true.  Conversely, if you consider the hypothetical case that the AMO is mostly natural, but you do not remove it, you would also get a wrong anthropogenic response in the end.  This you could have known even before you do the Matlab calculation.

45143. rockytom at 04:21 AM on 24 May 2013
       A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
       

       John, another fantastic article with the best graphics I've seen integrated with the text.  I wish we (John Cook and I) had had the graphics when writing our textbook (Climate Change Science: A Modern Synthesis) as we certainly would have included at least some of them (with permissions, of course).

45144. KK Tung at 04:09 AM on 24 May 2013
       The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
       

       In reply to post 106 by Dikran: The effect of offsetting on the perceived spread of models has been underdiscussed in literature.  I agree with what you said about it here, and I would encourage you to develop it into a publishable paper.   The procedure of offsetting with a baseline is needed for model projections because projection is different from a prediction.  In a prediction of ,say weather for the next few days, today's measured weather is our baseline, and such a baseline is assimulated into the model.  The model attempts to predict both the forced and unforced response.  Due to chaos, models start to deviate after today, and after two weeks, the prediction becomes mostly useless. But it is useful for a week or so.

       The IPCC projections of future climate change is different.  The model is initiated in the preindustrial period, 1850-1870, runs about 150 years in the 20th century simulation (when what is to be simulated is known), and then runs forward under different scenarios of future emissions.  There is no hope of doing a prediction of both the forced and unforced response over such a long period.  Instead it is hoped that the forced response of the climate is simulated with the ensemble mean of the model runs.  If, in the presentation of the results, all models are offset against their initial condition at 1850-1870.  The intermodel spread is rather large, even during the period of 20th simulation, where the observed response is known before hand. This is caused by systematic errors in each model. This intermodel spread is reduced by offsetting each model's ensemble mean by its own climatology in a specified period, say 1980-1999, as used in Chapter 10 of AR4. It reduced the intermodel spread during the period of offset, and also for a decade or so after that.  AR4 uses different offsetting period in different chapters, and there is no consensus on how to do it. You have found that a longer offsetting period makes the pre-2000 results less anomalous.  On the other hand, for the purpose of evaluating projections to the future, perhaps it may be fairer to the models to offset it with the lates known data.  That is, year 2000 for AR4 projection and year 2005 for the CMIP5 projection.  We however do not know what the observed forced response is, but since AR4 models have simulated the observed 20th warming quite well with forced (ensemble mean) solutions, it may not be a bad idea to offset the model prediction at year 2000 for AR4 projection with the observation at year 2000, and then attribute the subsequent deviation of the model ensemble mean from the observation to the presence of internal variability. Have you tried it yet?

45145. R. Gates at 03:34 AM on 24 May 2013
       A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
       

       Wow, fantastic post. Lot's a great information.  One bit of information, perhaps advanced but very important for understanding a negative AO index at certain times of the winter and the havoc it can bring to lower latitudes.  Sudden Stratospheric Warming events (SSW's) where air is descending over the pole form the upper stratosphere and even the mesosphere bring of course high pressure over the pole, warming, and often times a very negative AO index.  These SSW events in essence "open the freezer door" on the Arctic and shunt this very cold air down to lower latitudes.  The normal winter westerlies turn to easterlies as the Polar Vortex is often shattered, and you get real nasty weather at lower latitudes.  Looking back historically, very negative AO events in the winter are highly correlated with these very disruptive SSW events.

       But again, a great article!

45146. nealjking at 03:00 AM on 24 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       s_gordon_b:

       You wrote:

       "Categories 2 and 3 are too ambiguous - as defined in table 2 - to equate to the consensus that humans are not only a cause of industrial era global warming but the dominant cause since the middle of the last century (at least). Am I not reading that right? And if so, shouldn't only those abstracts that take an unambiguous stand on the consensus of dominant human causation be counted and the others excluded in the same way that abstracts that take no stand at all were excluded?"

       From looking at the paper, what I find as the first statement of the consensus (in the abstract) is: “Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming.” So the definition of the consensus position is that “humans are causing global warming”. But how is this to be understood?

       In my view, it has to be understood as "common speech": When the proverbial “man in the street” asks the question, “Are we (humans) causing global warming?”, he is NOT necessarily asking, “Is the degree of responsibility for global warming that is due to human activity greater than 50%?” or "Is human activity the dominant cause of global warming?" He is asking something much closer to, “Is human activity contributing to global warming big enough that we ought to be doing something different?” And I believe most scientists would agree with this understanding of the AGW issue: Not that the human contribution is necessarily greater than 50%, but rather that it is important enough that we should be seriously thinking hard about whether we want to change what we are doing, on a global scale.

       My understanding of the Levels of Endorsement (LOEs) 2 & 3 is that they indicate agreement, explicit or implicit, with the spirit of the underlined statement above, which I regard as a filled-out "common speech" version of the statement in the abstract.

       Therefore, I have no doubts about including LOEs 1 - 3 together as indicating support for the AGW consensus.

45147. barry1487 at 02:39 AM on 24 May 2013
       Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
       

       John Hartz,

       What exactly do you mean when you use the phrase, "academic merit"?

       Quality of scholarship..

45148. Dumb Scientist at 02:33 AM on 24 May 2013
       Has the rate of surface warming changed? 16 years revisited
       

       jdixon @27: Sure, just return it when you're done so I can use it again. ;)

45149. John Mason at 02:04 AM on 24 May 2013
       A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
       

       Eric - interesting question. I'll have a read of those papers and get back to you in a few days. However one point I would make is that because the Tropopause is such a strong temperature inversion, convective heat transfer between the troposphere and stratosphere is effectively blocked. I would therefore suggest the troposphere plays the main role.

45150. jdixon1980 at 01:46 AM on 24 May 2013
       A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
       

       Wow that's a lot of info without having to buy a meteorology textbook - will have to look this one over a few times to absorb it.

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