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Rob Honeycutt at 06:16 AM on 21 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
KR... Well, you know, they don't have much room to play with at 0.7% of the research. ;-)
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Eyal Morag at 05:59 AM on 21 May 2013Was Greenland really green in the past?
The Saga of Erik the Red - Icelandic Saga Database
1880, English, transl. J. Sephton, from the original 'Eiríks saga rauða'.Now, afterwards, during the summer, he proceeded to Iceland, and came to Breidafjordr (Broadfirth). This winter he was with Ingolf, at Holmlatr (Island-litter). During the spring, Thorgest and he fought, and Eirik met with defeat. After that they were reconciled. In the summer Eirik went to live in the land which he had discovered, and which he called Greenland, "Because," said he, "men will desire much the more to go there if the land has a good name."
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Alexandre at 05:41 AM on 21 May 2013Help close the consensus gap using social media
dagold at 05:22 AM on 21 May, 2013
Not likely, I know, but I wish there were more people dreaming of the right things...
Already liked on Facebook.
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dagold at 05:23 AM on 21 May 2013Help close the consensus gap using social media
Okay- think I got the hyper-link inserted now:
www.huffingtonpost.com/davidgoldstein/a-daughters-tears_b_3287465.html?utm_hp_ref=climate-change
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dagold at 05:22 AM on 21 May 2013Help close the consensus gap using social media
Well, here is my latest Huffington Post article with my attempt to generate climate awareness. It is the complete text of the dramatic climate policy speech we all want Obama to make. It's gotten some buzz in the climate world and I am hoping folks will share it enough so that it comes to the attention of Pres. Obama himself. Here it is: http://www.huffingtonpost.com/davidgoldstein/a-daughters-tears_b_3287465.html?utm_hp_ref=climate-change
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Rob Painting at 05:06 AM on 21 May 20132013 SkS Weekly News Roundup #20B
William - actual research demonstrates that the effect of ocean warming on fish stocks is significant. I don't think that anyone here disputes that overfishing is a huge concern - many species are heading toward collapse. These pressures are not mutually exclusive.
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rockytom at 04:38 AM on 21 May 20132013 SkS Weekly News Roundup #20B
#5. From Peru
It may be that the authors used a non-permafrost area to conduct their experiment. Their abstract doesn't mention permafrost (I haven't read the whole article). The main concern about the warming Arctic is the release of methane from thawing permafrost and not the release of carbon from non-permafrost soils over a 20-year period. Maybe someone who has read the whole article can elucidate.
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Dikran Marsupial at 04:35 AM on 21 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
I'm sorry Dr Tung, but there were no accusations of your motives, in fact I clearly stated "I did not mean to imply that your comments were deliberately unfair".
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MP3CE at 04:25 AM on 21 May 2013Help close the consensus gap using social media
I think SkS does this job very good. Perhaps the issue of polluting without paying a price to it should be compared to avoiding taxation at the expense of others, but again, I am not sure about public perception of this as some people do think that avoiding taxation is good and not a cheating on others.
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KK Tung at 04:17 AM on 21 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Replying to post 67 by Dikran: Your comment is well taken. I had suspected that all these accusations of my motives may be due to a word that I used. Instead of the word "underpredict" I should have used a longer phrase "a difference and the difference is negative when taken as the model ensemble mean minus the observation". I will try to be more careful commenting on this site and not use short-hand words. Often when I was busy or in a noisy environment trying to reply using my ipad I tend to write tersely, and it has not worked here.
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Dissident at 04:11 AM on 21 May 2013Another Piece of the Global Warming Puzzle - More Efficient Ocean Heat Uptake
I'm not sure whether this is off topic, but I have read in other threads that there is less cold water plunging to the ocean floor around Antarctica (and presumably the Arctic too) due to the sea water becoming less saline due to increased precipitation and melting polar ice. In the Arctic that can result in a weaker gulf stream in the North Atlantic, while in the southern ocean, would the same mechanism increase the flow of water into the Humboldt current (what doesn't plunge down has to go somewhere) - behaviour of both currents are different due to land mass distribution.
I think the increase in water 'available' for the Humboldt current would automatically make it stronger, would that be a reasonable hypothesis? If that current is stronger, wouldn't the likelihood of La Niña be increased, with an associated increase of polar water migrating to the tropical Pacific, which would affect the amount of heat absorbed by the Pacific?
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Alexandre at 04:00 AM on 21 May 2013Help close the consensus gap using social media
For some time now I'm convinced this issue needs a more skillful aproach - PR wise.
Documents like that joint statement from academies of science are not nearly enough to reach the broader audience. Only a few climate geeks get to read it.
Simple and direct messages are much more suitable for this kind of task. If you could get the endorsement of a few top-rank climate research insitutions, it could be even better (GISS? NOAA? Hadley Center?). I don't think it's beyond the reach of the SkS community.
This project is definetely a step in the right direction. I wish you success.
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william5331 at 03:35 AM on 21 May 20132013 SkS Weekly News Roundup #20B
If the snow pack is melting in the Rockies, providing the water too early for agriculture, they better start encouraging the spread of the Canadian Beaver. They serve the same purpose as glaciers in shifting water from winter to summer, mitigating floods and eliminating catastrophic low water. Read Three Against the Wilderness by Eric Collier to see just how effective beavers were in 1948 when the reverse happen. There was a very heavy snow pack and a much delayed spring. When it came, the floods were incredible and the Frazer Valley Delta by Vancouver had huge floods. Only on Meldrum Creek where Eric had brought back the beavers from near extinction, were the waters held and released slowly.
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william5331 at 03:23 AM on 21 May 20132013 SkS Weekly News Roundup #20B
Trying to blame climate change for a change in fish catches is like when the Canadians tried to blame the seals for the decline of fish on the Grand Banks. (read Sea of Slaughter by Farley Mowat). Yes there may be an effect but it is miniscule in relation to the destruction we have wrought on the fisheries stocks by our amazingly stupid fisheries policies. In the future, climate may be the overwhelming factor but at present it is us.
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Dikran Marsupial at 02:30 AM on 21 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dear Prof Tung, "underpredict" and "discrepancy" are both words that carry a strong implication that two things should be the same, but aren't.
As we agree, the ensemble mean is an estimate of only the forced response. This means that it is not itself a prediction of observed temperatures. Therefore it is unfair to say that the ensemble mean underpredicts something that it does not actually attempt to predict.
The collins dictionary says this about the word "discrepancy":
"Discrepancy is sometimes wrongly used where disparity is meant. A discrepancy exists between things which ought to be the same; it can be small but is usually significant. A disparity is a large difference between measurable things such as age, rank, or wages"
Now if you had said there was a difference rather than a discrepancy, your statements would have been far less of an issue.
Note this is not nitpicking. There are many skeptical arguments used to criticise models that explicitly or implicitly are based on the assumption that the observations should lie close to the ensemble mean (which would seem reasonable to most, but which we would I hope agree is incorrect). Sometimes these arguments even make it through into publciations in peer reviewed journals, for example Douglass et al (2008). When discussing science for the general public, especially on a contentious subject, such as climate change, it is very important to make sure that ones choice of words is correct and does not propogate misunderstandings.
I offer this in the hope that we can return to the substantive issue, which is the circularity of the proposed method.
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KR at 02:16 AM on 21 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
barry - Two comments, with the understanding that the "concensus on AGW" means AGW as the dominant force behind global warming:
First: The title is part of the definition of the categories, as viewed by both raters and authors. And category 2 "Explicit endorsement without quantification" is just that, endorsement of the AGW consensus. If a paper treats AGW as not the dominant influence, it's not endorsing the consensus, and shouldn't be rated as Category 2. Ratings are not just off the description (a refinement), but also the category title itself. And somehow, I cannot see an author whose paper rates AGW as a minority influence would voluntarily rate it as explicitly endorsing the consensus.
Second: Category 3, "Implicit Endorsement: Implies humans are causing global warming. E.g., research assumes greenhouse gas emissions cause warming without explicitly stating humans are the cause", is a clear endorsement of human caused global warming if you understand that greenhouse gas emissions are caused by humans.
Therefore, unless there is a statement in the abstract or paper that increases in GHGs such as CO2 are from natural causes, rather than anthropogenic (very much a minority view), this is indeed an endorsement of the consensus. Because, quite frankly, the evidence for human driven increases in CO2, CFCs, and the feedback from water vapor is overwhelming.
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What is most amazing to me in these discussions (here and on sites like the Blackboard) is the push for one-sided filtering: that papers categorized as rejections are always rejections, but that somehow papers categorized as endorsements are not always endorsements. That seems overwhelmingly biased to me...
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KK Tung at 02:05 AM on 21 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
In reply to post 63 and post 65 by JasonB: you and others are asking a different question and a different test than the point I was trying to make. The question you asked was if I claim that the model is in error in under predicting the observed warming what statistical test do I have to prove it. The standard test, which many of you are alluding to, is to test if the mean of all the ensemble members is different from the observation by seeing if it is within two standard deviations of the variance created by the ensemble members. If so then I cannot claim that the model is in error because the difference is random climate noise. My question was different, it concerns forced response vs unforced response. I used the model ensemble mean to approximate the forced response. If I see the forced response is lower than the observation, which contains both forced and unforced internal variability, I tentatively attribute the difference to internal variability that is not and should not be in the ensemble mean. It is tentative because there were not enough ensemble members from any modeling group in CMIP3. I see it happen systematically in most models we looked at with more attention paid to models we trust. I mentioned it previously as an revelation to me, a thought process that is often necessary in science, not a proof in mathematics. You may have a different thought process for discovery. I know of mathematicians who do not proceed to solve for the solution to a partial differential equation until they could prove that the existence and uniqueness of the potential solution.
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barry1487 at 01:55 AM on 21 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Amendment
"I don't believe 97% of papers/abstracts gave exlicit endorsement 1) to the notion that human activity is >50% responsible for global warming. I think 97% of papers gave unquantified + explicitly quantified endorsement that AGW is happening."
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Dikran Marsupial at 01:23 AM on 21 May 20132013 SkS Weekly Digest #20
Hi Tom, I hope the urgent matters can be resolved satisfactorally, I also look forward to your return.
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barry1487 at 01:23 AM on 21 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
A comment disappeared - don't know if my posting status has changed.
Jason, i've read the paper and the supplementary material quite carefully. The supplementary material gives the email sent to original authors with the endorsement statemtn (which mentions nothing about degree of human influence) and the options. Can you explain how options 2) and 3) endorse >50% human influence on global warming? I don't think they do at all. Only 1) specifically states this. The other 2 are unquantified, as the paper attests.I don't believe 97% of papers/abstracts gave exlicit endorsement 1) to the notion that human activity is responsible for global warming. I think 97% of papers gave unquantified + explicitly quantified endorsement that AGW is happening.
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barry1487 at 01:17 AM on 21 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Jason,
Did you actually try the rating exercise yourself?
Yes, twice in the public survey rating the 10 abstracts. The second time i loked up the full papers to see how the full text compared with the abstracts. I found, as most others did, that the full papers were more likely to express an opinion that the abstracts. I believe I understand what neutral means, and I certainly don't think it implies a rejection of the consensus. But neither does it imply endorsement.
I disagree that options 1, 2 and 3 support an endorsement of the anthropogenic influence of global warming is greater than 50%. only option does.
2) Explicitly states humans are causing global warming or refers to anthropogenic global warming/climate change as a known fact
3) Implies humans are causing global warming. E.g., research assumes greenhouse gas emissions cause warming without explicitly stating humans are the cause
The endorsement statement in the email received by original authors is given in the supplementary material.
Endorsement: The second drop down indicates the level of endorsement for the proposition that human activity (i.e., anthropogenic greenhouse gases) is causing global warming (e.g., the increase in temperature). Note: we are not asking about your personal opinion but whether each specific paper endorses or rejects (whether explicitly or implicitly) that humans cause global warming:
Can you explain how options 2) and 3) endorse a >50% contribution to global warming from humans?
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Tom Curtis at 00:29 AM on 21 May 20132013 SkS Weekly Digest #20
FYI, urgent private matters are likely to keep me away from climate discussion for the next month or so. I wish you all good fortune, and look forward to when I am able to once again rejoin the discussion.
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Bob Lacatena at 22:25 PM on 20 May 20132013 SkS News Bulletin #12: The Consensus Project
Tom,
As far as I know, this is common knowledge (and common sense). No one expects (or wants) the President of the United States to spend his time tweeting.
At the same time, there is no question that his twitter account follows guidelines and an agenda laid out by himself and his staff, and is under his name, so it is representative of what he would tweet if he had the time. It is for all intents and purposes from him.
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Tom Curtis at 21:20 PM on 20 May 20132013 SkS News Bulletin #12: The Consensus Project
And speaking of blunder's (or errors, anyway), apparently most tweets @BarackObama are not by the President himself. In the profile it says:
"Barack Obama Verified account
@BarackObama
This account is run by Organizing for Action staff. Tweets from the President are signed -bo.Washington, DC · http://www.barackobama.com"
The Tweet above is not so signed, and so originated with Obama's staff rather than with the President himself.
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Tom Curtis at 21:16 PM on 20 May 20132013 SkS News Bulletin #12: The Consensus Project
CBDunkerson @18, that is indeed the point. I think there is a legitimate further argument. "An expert is someone who knows some of the worst mistakes that can be made in his subject and how to avoid them." (Werner Heisenberg) When 97% of the world's experts on a subject agree, you can therefore be very sure that it isn't because they are making blunder. They may be wrong, but the facts that show them to be wrong will either be hard to come by, or require subtle reasoning to demonstrate. Put another way, when you have a broad concensus in a well developed field, it takes an Einstein to show that they are wrong.
Despite this, time after time deniers come up with arguments that AGW is not occurring, or will not be bad, etc, that assume the world's climate scientists have made absolutely trivial blunders. The arrogance of those claims continues to stun me. But anyway, given a 97% concensus, if somebody presents themselves saying they have made a trivial blunder it is quite appropriate to ask (and a valid implicit argument), "Which is more likely, that several thousand of the world's top scientists have made a trivial blunder, or that you have?"
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CBDunkerson at 20:51 PM on 20 May 20132013 SkS News Bulletin #12: The Consensus Project
william - The point of the study is not to argue, '97% of climate scientists agree, therefor it must be true'... but rather, '97% of climate scientists agree, therefor the claims of widespread scientific disagreement are clearly false'.
In short, this study should be a knockout blow to climate myth number 4 in the list at the upper left of the page. Though I expect the usual deniers to keep spreading that myth, hopefully now they will be called on it.
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Tom Curtis at 20:44 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
barry @146, the criticism that several of the abstracts were publicly discussed on the SkS forum, contrary to the statement in the paper that ratings were "independent" at the first stage, is correct. I do not have a hard figure on how many were discussed, but it is more than 10 and likely less than 20. Of those discussed, many (possibly most) were simply posted with a note that it was odd, or interesting and with no discussion of the appropriate classification or rating. Others were posted with the posters own classification but no further discussion.
These instances do contradict the claim in the paper that, "Each abstract was categorized by two independent, anonymized raters." With just 10 to 20 instances, ie, less than 0.2% of instances, to say the claim that the raters were not independent would be misleading. Never-the-less it could be argued that these abstracts should be excluded from the analysis. Of course, from among those I have examined, the were either excluded as "not climate related", rated as neutral or, in one instance, rated as rejecting the consensus. Consequently I don't expect any demands in that direction.
Given the very low number of abstracts involved and the very high number of abstracts surveyed, there is no question of these instances having distorted the result. Indeed, it is not even known that it would have changed the rating of any given paper so it is entirely possible that it would have no effect on the result.
Curiously, the only instance that contained extensive discussion the appropriate rating, and the instance used as an example by Brandon Shollenberger at Lucia's was Cool dudes: The denial of climate change among conservative white males in the United States. What he does not mention was that it was rated as neutral and excluded at not climate related. Given that it is an analysis of the effects of gender, race and politics (conservative white males) on acceptance of climate change denial, who could disagree? Of course, it takes all of 5 seconds on the SkS concensus project searchable database to find out that information - far too much time to be expected to spend on research before you start slinging accusations /sarc
In fact, the only person at Lucia's to have mounted criticisms of any seriousness is Lucia herself. I think she is wrong either on the substance of significance of her criticisms but at least they are criticisms worthy of consideration. The rest of the criticisms are completely inconsequential, absurd, or in at least one case outright dishonest.
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yocta at 19:54 PM on 20 May 2013It's too hard
Tom Curtis @27:
Thanks for the reply.A lot to think about. I would agree that looking more into the numbers of things is important, however the 77.7 square metres per week I feel is quite significant. Also that will only account for 2tW. There would be another 13tW to go.
According to the International Energy Outlook [1] the future of energy has it growing by ~50% by the year 2035. Projected oil use increases. Projected fracking from natural gas reservoirs also increases.
More of a comment really, but I don't share your optimism that it would only cost 1% of the US GDP. There are so many countries with their own competing interests, and, if history shows Economy always beats the Environment. Coal usage [2] shows absolutely no sign of slowing down, especially in the developing world.
If the effects from Cook et al., (2013) recent study still shows from the usual crowds is denial, denial, denial. The often misquoted Daniel Botkin on how it will take a natural disaster or two to get people really talking, Results from the Yale Climate Change Communication Project [3] showing that a cold season is enough for people to think Climate Change is not happening, again reinforces this view.
World population and energy use per person I think will be the elephant in the room. I would agree that Bartlett's equation does exclude the Emissions Intensity. Thankyou for that.
I am still staggered by the level of denial I meet on any news article, blog, or YouTube video of people still not understanding anything.
This reads more of a rant than anything constructive. I wish I could share your optimism. Myself I work in the energy sector trying to green things (or at least light brown) them up but at times I feel like Sisyphus. If you or anyone could direct me to any readiing material that can show a more optimisic world view I would be very appreciative.
[1] http://www.eia.gov/forecasts/ieo/
[2] http://www.eia.gov/oiaf/aeo/tablebrowser/#release=IEO2011&subject=0-IEO2011&table=7-IEO2011®ion=0-0&cases=Reference-0504a_1630
[3] http://environment.yale.edu/climate-communication/article/Climate-Beliefs-April-2013
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Kevin C at 19:35 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Eli's just put up a cross comparison from his own smaller study here.
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scaddenp at 17:42 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Barry, the aim of the methodology is create an inscutable rating of the papers. It is not an investigation of bias - it aims to avoid it. Surely discussion and comparison of ratings and raters to produce a reliable rating of the papers is actually important to this.Deniers are in a tiz of John's surveys because they are not confident that their ratings would not show bias. However, this paper is actually about measuring the consensus.
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JasonB at 17:37 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Hard to believe that something so basic can stump them.
Indeed.
I think of the work leading up to the supporting/rejecting test as a filtering exercise, designed to weed out the irrelevant papers.
We start with the title of the paper: "Quantifying the consensus on anthropogenic global warming in the scientific literature"
That means that the first filter we are going to apply is one that will weed out everything that is not "the scientific literature". In this case, the ISI Web of Science was chosen to represent "the scientific literature".
This will include a lot of early papers that are not really relevant to modern scientific thinking, so the next filter is to limit the time period to 1991-2011.
This is still going to give an enormous quantity of literature to review, most of which will be irrelevant to the question at hand, so the next filter is to use the topics "global warming" and "global climate change". This should not affect the final result provided there is no systematic difference in the use of those keywords between papers that endorse the consensus and those that reject it.
Now the first three filters don't really require any manual effort to apply, but unfortunately there's no avoiding the next one — weeding out papers that are irrelevant to the question at hand but happen to use those keywords. That requires human involvement.
But the result of that final filtering step is a set of papers that actually does address the question and allows the degree of consensus to be quantified, just as the paper purported to do.
Now, they could report the percentage of papers that endorse the consensus and the percentage of papers that reject the consensus as percentages of various totals:
1. All papers that address the question at hand. (97.1% endorse, 1.9% reject.)
2. All papers that passed the keyword and date range filtering steps. (32.6% endorse, 0.7% reject.)
3. All scientific papers. (~0% endorse, ~0% reject.)
The first one is obviously relevant because it directly addresses the question at hand.
The second is also somewhat interesting, because we expect that as the science matures, fewer and fewer authors will feel the need to state a position on the subject because it will be conventional wisdom, and it's interesting to know how much effort the authors put in and to quantify the size of the work in the field.
The third is obviously useless.
Confusing the second with the first is, as you say, hard to believe.
Why stop at papers with those keywords? What is so special about a paper that fails to address the question that happens to use those keywords vs a paper that fails to address the question that happens not to? After all, the purpose of those keywords was simply to make the problem tractable by reducing the number of papers that need manual classification without, hopefully, affecting the final results. The percentages in #2 can be made as small as you like by adding even more irrelevant papers, but the percentages in #1 should be invariant provided the assumption holds that there is no systematic difference in the use of those keywords between papers that endorse the consensus and those that reject it.
Anybody who nevertheless chooses to use #2 but fails to report the "rejection" figure as 0.7% really has no excuse.
BTW, there is one filtering step that really does make a difference to the outcome, and that's the first one, but since that's the whole point of the paper I guess I'll let it slide. :-)
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JasonB at 16:43 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
I think the distinction between accept/reject AGW (options 1, 2 &3) and >50% influence (option 1) is blurred at times in the paper.
Papers that implied humans were having a minimal impact without saying so explicitly, or explicitly minimised or rejected the notion that humans are causing global warming, or explicitly stated that humans are causing less than half of global warming, were classified as 5, 6, and 7, respecitvely, so I think that the reporting you are objecting to actually reflects the findings correctly.
one must also be careful to note that a large proportion of the rated abstracts/papers were neutral.
Did you actually try the rating exercise yourself? If not, I suggest you do so, because then you'll see why they were "neutral" and what that really means. 50% of my sample were "neutral" according to the rules of the classification, but in every case it was purely because they were looking at impacts without addressing why global warming was occuring as it was outside the scope of their study. Indeed, the very first sentence of the introduction of one of my "neutral" papers (rated by reading the abstract in isolation) explicitly stated how much temperature was due to rise globally over the coming century based on greenhouse gas emissions and cited the IPCC as the reference!
For the purposes of this study it is fair to ignore neutral papers when quantifying the consensus, but it would be a mistake to assume that because they are neutral that is somehow evidence against the consensus. In fact, the reverse would be true — as the science matures, fewer and fewer papers would feel the need to mention "humans are causing global warming" because it's taken for granted that everyone accepts that, just as papers in the field of biology aren't going to be stating that they accept evolution unless they are explicitly about evolution.
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schmoepooh at 16:37 PM on 20 May 20132013 SkS News Bulletin #12: The Consensus Project
People who make a living dealing in untruths find it convenient to suppose truth is an unrealistic ideal.
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JasonB at 15:45 PM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dr Tung,
It was not intended to be a criticism, but I might have pushed one of the hot buttons for some of you unknowingly. Could it be the word "under predict", which to me just means that the model warming is less than the observed warming. I did not attach any value judgement to it.
I think the issue is that we're used to statements like that being supported. There are many potential reasons why the models might under-predict the early 20th century warming but we'd like that to be established before moving on to the implications.
Your point about inter-model variability is a good one. One danger of combining different models with different systematic errors is that the systematic differences become part of the spread (i.e. it makes it harder to distinguish between internal variability, which is meant to model non-climactic "noise", and systematic differences between models).
If this is a genuine issue that you have identified then you should be able to answer "Yes" to my first question in my last comment — there is a test that would allow you to distinguish between the actual observations and any of the individual model realisations. If so, please present it, it would be really interesting to see.
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KK Tung at 15:39 PM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
In reply to Tom Curtis in post 61: your points are well taken. Assume the observation is perfect in my hypothetical argument. By "multidecadal internal variability" you could take it to mean "internal variability that in this multidecadal period in total gives rise to an additional warming"
I find it frustrating that I often get bogged down by words. I was surprised by so much nitpicking that distracts the discussion into a different direction. I guess I shouldn't have been surprised. After all this is Skeptical Science.
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JasonB at 15:31 PM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dr Tung,
But we find the model ensemble mean to under predict the observed warming rate in the first half of the twentieth century.
You keep making this statement as if it is self-evidently meaningful so allow me to ask a very simple question:
If you plot the observed warming rate in the first half of the 20th century together with all of the model simulations, does it stand out? In other words, can you pick out which one is the observed warming without knowing in advance which line represents the observations and which lines represent the simulations?
My answer to that question would be "No", based on Figure 9.5 (a) from AR4, posted already by KR in #23 and reproduced here for convenience:
If the observed warming wasn't black then you wouldn't be able to distinguish it from any of the individual realisations of the climate models. Contrast this with Figure 9.5 (b) above — the behaviour of the black line clearly stands out from the individual realisations in the second half of the century and is even the most extreme realisation a few times in the first half.
A more sophisticated test would be: "What is the range of trends for the individual realisations for the first half of the 20th century? Is there a statistically significant difference between the observed trend and that range?"
All of this is even before considering Tom Curtis' points, which are also valid, and the fact that Kevin C's simple 2-box model does a remarkable job of matching the observations with just the forced response and ENSO.
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KK Tung at 15:28 PM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Continue with my post 60: I hope post 60 can clear up the confusion and we can get back to the scientific issue at hand.
Back to CMIP3 models. I mentioned that the intermodel spread is rather large. It is difficult to conclude anything concrete with the intermodel spread. For political reasons less developed models from some countries were included. Some models have unrealistic internal variability. I know of one model with a perfectly periodic ENSO with exactly two year period that is also quite large in amplitude. Another model with a huge decadal variability of 0.4 C in the global mean temperature. In the 40 years the early twentieth century warming also warmed by 0.4C in the observed global mean temperature. When all of the model results are averaged in the all model ensemble mean, only 0.2 C warming is found during this period. There should have enough members in the all-model ensemble mean to eliminate the model internal variability, but we are not sure if that ensemble mean gives the correct forced solution. We could pick a few models we know and trust and look at them. Although there were not enough ensemble members available (usually 5 were done), we suspect that they were good enough to reveal approximately the forced response. During the first half of the 20th century, the warming generally were rather flat in these models that we examined. This is also a period during which the AMO was in its warm phase and can contribute 0.3 C to the warming. This was my thought process. It was not intended to be a criticism, but I might have pushed one of the hot buttons for some of you unknowingly. Could it be the word "under predict", which to me just means that the model warming is less than the observed warming. I did not attach any value judgement to it.
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barry1487 at 15:01 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
scaddenp.
Barry, how exactly can "double-blind" applied to this methodology?
It does not apply. I mentioned that as but one familiar standard, a strict one. Is there a standard that the methodology for independence follows in this paper? Or is it a unique methodology? Is it normal practise for surveyors to discuss and amend their approach during the initial ratings procedure in this kind of review, or is it unusual? Does the methodology weaken the results? I don't know the answers to these questions.
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Tom Curtis at 14:53 PM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
"In this hypothetical case the discrepancy is certainly due to the presence of a multidecadal internal variability"
Or it is due to two episodes of opposite sign of subdecadal variablility coincidentally timed.
Or possibly it is due to an incorrect characterization of the forcing agents (ie, the paleoclimatologists got it wrong, not the modellers).
Or it is due to errors in the instrumental record due to reduced coverage consequent on the two world wars.
Or it is due to synergy of two or more oceanic oscilations that do not coincide more than once every thousand years on average.
Or ....
The leap to the AMO is not justified, and is certainly not justified on the AR4 model runs which do not have a systematic error in the post 1950 temperature record which would be there if the AMO was the cause of "systematic discrepancy" in the early twentieth century. If you are to run your argument, you must at least assume the models are in error about the post 1950 forcing response, and hence presumably the pre-1950 responce. Having done that, you are not entitled to assume a "perfect" model will continue to show the pre-1950 discrepancies.
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barry1487 at 14:52 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Rob,
Exactly how many times do you have to do research coming to the same conclusion using different methods before "skeptics" finally admit that maybe the answer is correct?
I don't know which posts you are referring to, but a counter to your point is the "right answer, wrong method" response. This is a particularly apt caution considering the emphasis given by the author/s of this paper to the importance of solidifying public perceptions.
(I'm still mulling over the methodology and haven't yet arrived at an opinon)
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bharath272 at 14:32 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Kudos to you all for the effort!
I am wondering something : did you in any way measure the correlation between the abstract rating and the self rating? The paper mentions only how many papers were rated as endorsing or rejecting or no position under each rating method. It would be fun to see if there are any patterns in the rating of the abstract, which is admittedly subjective, vis-a-vis the self rating....
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KK Tung at 14:29 PM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
In reply to post 56 and post 59: I must have been a terrible communicator that you both think that I said the opposite of what I wanted to say on some aspects of the problem. So let me try again in a different way. Let us remove the emotions and value judgements by considering a perfect model of our climate, a hypothetical model. Because of chaos, and the hypersensitivity to the initial conditions, we can only hope to simulate the observed forced response, not the observed response which contains definitely both forced and unforced response. To reveal the model forced response, we need to average out the internal variability by ensemble averaging. We need at least 15 ensemble members, each initiated differently. Suppose we have the resources for doing them and we now have the perfect model forced response. Now we want to compare with the observed response, but we do not know what the observed forced response is. But we find the model ensemble mean to under predict the observed warming rate in the first half of the twentieth century. What can we conclude from this fact? By using the word "under predict" I can't possibly be saying the model's forced solution is in error. Remember we said the model is perfect. Is it unfair to the hardworking folks who produce this model to even compare the model with the observation and notice this systematic discrepancy? Notice that I used the word "discrepancy" and not the word "error". In this hypothetical case the discrepancy is certainly due to the presence of a multidecadal internal variability (do I dare to say the AMO?), which is present in this one realization that is our observed climate but not in the ensemble mean model result.
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Daniel Bailey at 14:19 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
"Exactly how many times do you have to do research coming to the same conclusion using different methods before "skeptics" finally admit that maybe the answer is correct?"
Exactly, Rob. Just as the E.P.A. is not required to reprove the existence of the atom every time it approaches a scientific question, scientists need not state a position on climate change in every paper they publish.
This is why the National Academy of Science took the unusial step of referring to the warming of the Earth and the human causation of it as "settled fact" (pages 44 and 45, here). -
scaddenp at 14:09 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Barry, how exactly can "double-blind" applied to this methodology? The conventional meaning is that subject doesnt know whether getting placebo or treatment, and nor does the assessor of the subject response. I'm scratching my head to see how you apply this paper ratings.
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Rob Honeycutt at 13:57 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
This begins to sound something like the hockey stick arguments. "Skeptics" claiming that this study is wrong for one reason, and another wrong for another reason, etc. But there are now over a dozen multiproxy reconstructions that come up with essentially the same conclusion as Mann's original work.
Now we have the consensus issue. Here we have a much larger sampling of data that is coming up with almost exactly the same number as several previous research papers. But there is always this and that nitpic.
Exactly how many times do you have to do research coming to the same conclusion using different methods before "skeptics" finally admit that maybe the answer is correct?
It seems to me this is exactly why we begin to call "skeptics" deniers.
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barry1487 at 13:38 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Dana @ here,
I hope I express Lucia's views properly:
Lucia thinks that if reviewers altered their approach to rating during the first phase of the rating period as a result a result of discussing and refining rating criteria, then this interferes with the notion of independent rating.
I'm not convinced either way, based on what the study methodology purports, but it certainly fails a double-blind test.
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barry1487 at 13:28 PM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
I think the distinction between accept/reject AGW (options 1, 2 &3) and >50% influence (option 1) is blurred at times in the paper. The paper begins;
Among abstracts expressinga position on AGW, 97.1% endorsed the consensus position that humans are causing global warming
but then strays in the body of the paper.
...there is wide public perception that climate scientists disagree over the fundamental cause of global warming...
...We examined a large sample of the scientific literature on global CC, published over a 21 year period, in order to determine the level of scientific consensus that human activity is very likely causing most of the current GW...
...We classified each abstract according to the type of research (category) and degree of endorsement. Written criteria were provided to raters for category (table 1) and level of endorsement of AGW (table 2). Explicit endorsements were divided into non-quantified (e.g., humans are contributing to global warming without quantifying the contribution) and quantified (e.g., humans are contributing more than 50% of global warming, consistent with the 2007 IPCC statement [consensus?] that most of the global warming since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations)......Among respondents who authored a paper expressing a view on AGW, 96.4% endorsed the consensus....
A careful reading can tease this distinction apart, and one must also be careful to note that a large proportion of the rated abstracts/papers were neutral. It wouldn't matter so much if this was not a study aimed at public perceptions. As Joe Public aren't always careful readers they could come away with the impression that 97% of all the abstracts/studies endorse the 'consensus' that humans are primarily responsible for global warming over the last 50 - 100 years. This distorted reading, helped along by SkS emphasis here and there, is echoed in the press and blogosphere. Eg,
They found over 4,000 studies written by 10,000 scientists that stated a position on this, and 97 percent said that recent warming is mostly man-made.
http://www.accuweather.com/en/weather-blogs/climatechange/new-study-reaffirms-overwhelmi/12560235
The vast majority of scientists who conduct climatological research and publish their results in professional journals say humans are the cause of global warming.
The study went one step further, asking the authors of these papers to rate their entire paper using the same criteria. Over 2000 papers were rated and among those that discussed the cause of recent global warming, 97 per cent endorsed the consensus that it is caused by humans.
http://www.australasianscience.com.au/news/may-2013/consensus-humans-cause-climate-change.html
A survey of scientific papers by a team led by Mr Cook and... found more than 97 per cent of researchers endorsed the view that humans are to blame for global warming.
Of those who a stated a position on the evidence for global warming, 97.1 per cent endorsed the view that humans are to blame.
These statements either state or imply that 97% of rated abstracts (or the subset of those venturing an opinion) agree with the proposition that human activity is responsible for most/all of recent global warming, a misapprehension not undiminished by the full context of the articles.
Is there a breakdown of results for each of the 7 ratings for the whole period in the study or supplementary material? I couldn't find any, which is a disappointing omission for a peer-reviewed survey.
The messaging seems to be successful, but at some cost to scientific rigour, IMO. Advocacy and objective science make uneasy bedfellows.
Moderator Response:[RH] Fixed link that was breaking page formatting.
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KR at 12:37 PM on 20 May 20132013 SkS News Bulletin #12: The Consensus Project
william - One of the underlying issues is that the public perception (and hence the political will to action) of climate consensus is only about 50-50%, rather than the reality of 97-3%. This is in large part due to false balance in the media (one denier for one scientist) and a rather dedicated campaign to heighten uncertainties - see the 2002 Frank Luntz memo for some real horrors in that regard.
That consensus gap is a serious impediment to political action - and (IMO) why this paper is important.
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william5331 at 12:26 PM on 20 May 20132013 SkS News Bulletin #12: The Consensus Project
Playing the consenses card is unscientific, and just gives the deniers ammunition. Climate change is real at the omega 3 level because virtually all the evidence supports it. No need to stoop to the level of the deniers to try to make the point.
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Bob Loblaw at 11:58 AM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dr. Tung:
I have been watching the disucssion, but I have been mostly staying out of it. One of the comments policies here at SkS is "no dogpiling", which means SkS does not want one participant to have to deal with comments from a large number of people at the same time. In this case, I have tended to stay out because you, as author of the blog post, may find it discouraging if you have to have multiple conversations with multiple participants at the same time. It is more constructive to keep a small number of conversations going, and avoid having you feel overwhelmed.
Nonetheless, I have been reading, and Dikran has suggested that he'll be dropping out, so I am going to pick up the conversation with one point that you have repeated several times. In #55, you said:
"What it reveals to me is a tendency for the model ensemble means to under predict the observed warming in the early half of the 20th century."
Now here is the problem that I have with that statement, and what I believe Dirkan has been trying to point out in his comments about the spread of the model simulations:
- you have agreed that the ensemble mean represents primarily the "forced response" (at least, better than a single model run would).
- you seem to be neglecting that the observations always represent both the forced response plus the internal variability. It cannot possibly be any other way - the observations include everything. Thus it is, in part, an apples-oranges comparison to look at observation with respect to the ensemble mean.
You cannot come to a conclusion that the ensemble mean of the models is in error (which is what "under predict" is saying) unless you can separate the forced portion of the observations from the internal variation portion. And that is exceedingly difficult.
Even in a single model run, you cannot easily separate the forced and non-forced portions of the response. However, if you run the model a number of times, with slightly different initial conditions, each different model run will have the same forced response, but a different "internal variability" response. Averaging those runs will see the forced response have the same effect on the ensemble mean (thus it will be strongly represented), but the differing internal variability between runs will tend to cancel out and not appear in the mean.
At that point, the ensemble mean no longer tells you about internal variability - but you can look at the entire range of individual model runs to see how far the internal variability can change the results from the forced response.
..and to get back to the observations - as long as the observed temperatures fall along the path that could have happened in any one of the many possible single model runs, then you have to accept that the observations are not in disagreement with what the model has done. After all, if you picked a different model run, you'd see a different combination of forced response plus internal variability - and the model isn't "wrong" until it is different from all single model runs (i.e., it falls outside th range).
In summary, I simply disagree with you that comparing the ensemble mean to the observations is an appropriate test. The ensemble mean could be a perfect match for the real forced response, and the ensemble mean and observations would still be different because the observations include both the forced response and the internal variability.
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