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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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Riduna at 11:36 AM on 20 May 2013Who is Paying for Global Warming?
Old Mole – You are quite right. Thank you for pointing out the error in percentages shown as “% of Total Production Exported” in Table 4. The percentages published are wrong - caused by a spread sheet coding error which I should have picked up in the final edit. They will be corrected.
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Riduna at 09:43 AM on 20 May 20132013 SkS Weekly Digest #20
JH - How eminently sensible - and that cartoon, surely one of the best published by SkS!
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KR at 07:44 AM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
I find discussions like this delightful - although I find myself wanting to wave my arms as I talk, scribbling back and forth on a white-board.
I invariably learn from them, even in the (all too common, sadly) case of finding I was completely mistaken. :)
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CBDunkerson at 07:30 AM on 20 May 20132013 SkS Weekly Digest #20
On the, "If you know of any media coverage which is not listed on the page, please let us know in the comments and we'll add it."... were you looking to include hatchet jobs or not? I note that Watts, Bishop Hill, Tucson Citizen, and other denier outlets that miscast the survey aren't listed... but Science 2.0's article insinuating that it was a non peer-reviewed vanity paper is included.
Moderator Response:[JH] Dana writes the text for the SkS in the News sectuion of each Weekly Digest. That is where the sentence you quote comes from. It is therefore appropriate for him to respond to your question.
As the creator of the Weekly News Roundup and the News Bulletin, I studiously avoid including articles from denier outlets such as the ones you have listed.
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scaddenp at 07:22 AM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
This has been a very interesting discussion and I would be very disappointed if an aggressive tone led to a premature conclusion. I would really encourage the participants to keep discussing the science. It's rare to see such debate online.
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Jim Eager at 06:01 AM on 20 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Herrhund, first, GCR induced cloud nucleation climate forcing is very far from being an established theory supported by the full body of evidence. But more important, as DSL pointed out, any GCR effect, regardless of sign or magnitude, would in no way negate the radiative physics of CO2 and other greenhouse gases, nor negate the observed fact that burning fossil carbon has increased atmospheric CO2 by ~42%, thereby forcing Earth's energy budget out of balance. Any GCR effect would be entirely separate and in addition to the known anthropogenic enhanced greenhouse forcing, and not in any way be an alternative hypothesis. In short, it would neither endorse nor refute the AGW hypothesis.
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Dikran Marsupial at 03:02 AM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
I'm sorry Dr Tung, I explained why it is important to look at the spread of the model runs as that is the way in which the models characterise internal variability. You agree with me on this point, as you wrote "I agree with everything you said except the last paragraph", yet you then follow this by "discussing model-observation systematic discrepanices", without reference to the spread of the model runs and concentrating solely on the ensemble mean.
Of course the model ensemble means don't exactly match the observations, but this is not evidence of a systematic discrepancy, it is evidence of a stochastic/chaotic discrepancy, which the spread of the models clearly tells us we should expect to see.
I will now bow out of the discussion. I have explained why I feel your comment was unfair, and explained the two reasons for this, and asked you "Do you disagree with either of these statements? If so, please can you explain why.". I am perfectly willing to change my mind if I am wrong, but if polite questions are asked that are designed to address a misunderstanding, and those questions are ignored, the chance of a productive discussion are rather slim. Note I did not mean to imply that your comments were deliberately unfair.
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KK Tung at 02:07 AM on 20 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
In reply to post 54 by Dikran Marsupial: I agree with everything you said except the last paragraph, where you still accuse me of being unfair to modelers. I am one of them and I had no intention of doing so.
What is nice about this way of communication is that what we said are all recorded. You can go back to reread what I said and see if I was being unfair. My statements were about what we could learn from the models, in particular about model-observation systematic discrepancies. We have looked at both CMIP 3 and CMIP5 model result archives, at individual model's ensemble means where it is available. 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. I wanted to learn from this model result, while you thought I was a unfairly attacking the hard working modelers. I suggested that the discrepancy was possibly due to the absence of internal variability in the ensemble mean. The ensemble means were not supposed to contain much internal variability. We both agree with that.
The intermodel spread is an entirely different matter.
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From Peru at 01:54 AM on 20 May 20132013 SkS Weekly News Roundup #20B
What happened with my HTML hyperlinks?
Moderator Response:[DB] Manually writing the html results in what you initially saw. The new commenting features incude a WYSIWYG interface. You can highlight your selected text and then click the Insert/Edit Link button to establish a hyperlink to your selected text. I fixed your html in your previous comment.
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From Peru at 01:51 AM on 20 May 20132013 SkS Weekly News Roundup #20B
I am confused by this paper in Nature:
Long-term warming restructures Arctic tundra without changing net soil carbon storage
That shows that at a site where for 20 years there was simulated greenhouse warming, "there was no net change in total soil carbon ( P=0.5) or nitrogen stocks" and "After 14 years of warming, greenhouse plant carbon stocks had increased by 50%"
I am not surprised from the increase in plant (vegetation) carbon, that was already found in other studies, but the "no change in total soil carbon" seems at odds with a lot of papers that studied this problem before.
Any idea of what is going on?
Note on "other papers": I was thinking in papers like this:
The effect of permafrost thaw on old carbon release and net carbon exchange from tundra
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CBDunkerson at 22:45 PM on 19 May 20132013 SkS News Bulletin #12: The Consensus Project
Joshuas193: You can find answers to all of those questions on this site. The list of common issues on the left and the search panel should both help.
1: China is the largest emitter in total and the US the largest emitter per person. However, that isn't the right question. This isn't a problem caused by one, or two, or a dozen countries. Rather, there are only a handful of countries which are not a significant part of the problem. See this link for info.
2: The only currently viable solution is to switch to power sources which do not emit carbon dioxide. Various geo-engineering schemes have been proposed, but none seem likely to work. Many countries have begun clean power programs, but thus far they have mostly just slowed emissions growth. The US is one of only a few countries which has actually been able to decrease emissions... by converting large amounts of power generation from coal to natural gas, but that can only go so far.
3: The tech exists and should actually cost much less than fossil fuels... except that fossil fuels receive massive direct and indirect subsidies which have kept them in use. Unsubsidized solar PV power is now falling below even the heavily subsidized cost of fossil fuels in sunny parts of the world. See renewable power and fossil fuel subsidies.
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MA Rodger at 22:28 PM on 19 May 20132013 SkS Weekly News Roundup #20B
chriskoz @3
The paper by Chen et al is on-line here.
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Tom Curtis at 22:26 PM on 19 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Longhornmaniac8 @134, I believe you've got the idea, but you have your figures wrong. When normalizing the original abstract ratings to allow for detected bias, I get the following for all papers rated:
Total: 11944 (100%)
Affirm: 7349 (61.53%)
Neutral: 4334 (36.29%)
Unsure: 22 (0.18%)
Reject: 239 (2.0%)Ignoring neutral papers, that gives us:
Total: 7610 (100%)
Affirm: 7349 (96.57%)
Unsure: 22 (0.29%)
Reject: 239 (3.14%)So, even adjusting for bias as best we are able with publicly accessible figure, the 97% concensus figure looks very solid, although it is possible that the original abstract rating understated rejections (1.2 vs 3.1%). We should not make the mistake of thinking that normalized figures are superior to the original abstract ratings. They no doubt contain their own biases, and some dubious projections. The figure for "unsure" papers is based on projections from just 5 out of a 1000 papers.
The normalized figures do not supplant the original figures, therefore, but help flesh out how robust those figures are. Various critics of this paper have pointed out a number of possible causes of error (many of which are imaginary). They have not, however, tended to flesh out the criticisms with numerical values. When you do, as you can see, the original figures continue to look very good.
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chriskoz at 20:39 PM on 19 May 20132013 SkS Weekly News Roundup #20B
An interesting article on the shifting poles due to the Greanland melt. Obviously they have the data from GRACE and the data should confirm the SLR contribution by icesheets.
But an interesting aspect is, as Jianli Chen, the lead author says, they have some polar shift data going back 100y. With that data, they can estimate the Greenland melt, hopefully quite precisely for those 100y, well before GRACE. It will an interesting development.
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Dikran Marsupial at 20:14 PM on 19 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dr Tung, electronic forms of communication have a tendency to be percieved (on both sides) as being more aggressive than is intended. None of what I have written is intended as an attack on you, but is intended to understand your statements and to discuss and correct errors where they appear. That is the way science should work. I find the best way to go about this is to ask direct questions and give direct answers; however when they are not answered this inevitably leads to misunderstandings.
The ensemble mean is the models estimate of the forced response, I think we can agree on that.
Now I would say that the spread of the ensmeble (at least for a particular model) characterises the plausible effects of the unforced response (i.e. natural variability) and the observations can only be expected to lie within the spread of the models runs and no closer. Do you agree with that?
Now you have said that the spread of the models is wide, and I have agreed that it is. However, what I want to know is whether you think there is good reason to expect the spread of the models to be any smaller than it is. This question is intended to help me understand why you appear to think that the models under-predict the warming. As far as I can see it doesn't, the warming lies within the stated uncertainty of the hindcast.
Essentially when comparing observations with models you need to look at BOTH the ensemble mean AND the spread of the ensemble as they are both integral parts of the projection/hindcast. If you only look at the ensemble mean and igniore the spread, you are ignoring the information about internal variability that the model provides.
I'm sorry, but in my view you are being unfair in suggesting the modellers use the ensemble mean because they can't predict chaotic phenomenon, firstly becuase the forced component is the answer to the question posed by the politicians and secondly because they don't ignore internal variability, the spread of their model ensemble is a characterisation of internal variability. If the modellers only used the ensemble mean the comment would be fair, but they don't. Do you disagree with either of these statements? If so, please can you explain why.
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noelfuller at 18:32 PM on 19 May 20132013 SkS Weekly News Roundup #20B
There is some good comment with links on the report on sealevel rise projections just published here:http://www.carbonbrief.org/blog/2013/05/scientists-warn-of-up-to-70-cm-of-sea-level-rise-by-2100,-but-is-this-better-or-worse-than-we-thought -
noelfuller at 18:26 PM on 19 May 20132013 SkS Weekly News Roundup #20B
With respect to the Telegraph story on Fiji villagers moving uphill and others doing the same there is reference made to a new study on sea level rise by 2100 (but no link) where the maximum sea level rise is misquoted as 27cm. In fact the study claimed 27 inches or 69 cm. -
BillEverett at 17:18 PM on 19 May 20132013 SkS News Bulletin #12: The Consensus Project
Joshuas193@11, you can find answers to some of your questions via WBGU-World_in_Transition.doc.
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dhm60 at 16:59 PM on 19 May 2013Trillions of Dollars are Pumped into our Fossil Fuel Addiction Every Year
An intresting piece on one of the denier groups (Intitute for Energy Research) can be found here: www.instituteforenergyresearch.org/2013/04/03/the-imfs-outlandish-claims-about-energy-subsidies/
Standard approach - question the science (Big Oil pay way too much tax) while denigrating the work (outlandish?). I guess the IMF are now part of the great big global AGW conspiracy now. :o That's the IMF - part of the Washington Consensus!
btw: The IMF did a good paper on petroleum subsidies in 2010 entitked "Petroleum Product Subsidies: Costly, Inequitable, and Rising". Worth reading. http://www.imf.org/external/pubs/ft/spn/2010/spn1005.pdf
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KK Tung at 16:42 PM on 19 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
In reply to post 51 by Dikran Marsupial:You have taken my statements on model-observation discrepancy out of context. We all seem to agree that ensemble mean model results reveal the forced response. And we all agree that this one realization that is our observed climate in principle contains internal variability as well as forced response. If model ensemble mean systematically under predicts the observed warming, as happens in the first half of the 20th century, it is legitimate for a scientist to ask whether the difference could be caused by the presence of internal variability in the real climate. To me the discrepancy is revealing and is what we should be learning from models. This is not a criticism of the models. You first claimed that the difference was insignificant because the internal variability is unpredictable by models and quoted AR4 to support your view. Then when I replied that your position was essentially asking us to ignore internal variability you accused me of being deeply unfair and uncharitable to the community of hard working scientists. I am sorry that our scientific discourse has taken this sad turn.
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Bert from Eltham at 16:38 PM on 19 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
There is 100% consensus from the denialist camp on the validity of consensus in scientific matters of peer reviewed papers especially with this peer reviewed paper. Does their opinionated only consensus even negate their own premise? It is a perfect example of circular thinking. Sad. Bert
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scaddenp at 16:00 PM on 19 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Herrhund. There was an interesting review of the CLOUD results at RealClimate which gives some indication of why the research is interesting and worth doing. However, it also outlines succinctly the steps required for the results to even relevant to the question of global climate change. Do you believe new results from CERN are going to advance any of these steps further?
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Joshuas193 at 15:31 PM on 19 May 2013Antarctica is gaining ice
Ok, so I am a noob here. but if I am reading this right there is increased loss of Land Ice in Antarctica and this fresh water freezes easier causing the sea ice to be greater? And even with the rise in temperature it is too small to cause the sea ice to melt. Is this basically the short version of the article?
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