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DSL at 07:15 AM on 25 May 2013It hasn't warmed since 1998
Chemasan, the methodology of Levitus et al. (2012) includes Argo data. Go here to see the results. If you choose Jan-Mar on any of the 3-month sets, you'll get up to 2013. I strongly suggest using the 0-2000m set. Here's global 0-2000m for all months:
2005-3 8.972987
2005-6 9.391529
2005-9 9.681848
2005-12 12.636982
2006-3 11.932278
2006-6 12.998004
2006-9 12.264493
2006-12 13.356965
2007-3 13.49815
2007-6 11.382808
2007-9 12.277043
2007-12 12.418795
2008-3 13.305184
2008-6 14.606297
2008-9 13.024848
2008-12 12.090649
2009-3 12.614719
2009-6 12.241169
2009-9 13.816815
2009-12 15.052814
2010-3 15.881298
2010-6 13.484779
2010-9 13.959781
2010-12 14.823184
2011-3 15.215552
2011-6 14.630487
2011-9 16.870249
2011-12 14.859973
2012-3 17.308126
2012-6 15.461417
2012-9 15.34632
2012-12 16.630146
2013-3 19.332438The annual running average produces a linear trend of +1.74*10^21 joules added per year.
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Chemasan at 06:50 AM on 25 May 2013It hasn't warmed since 1998
For #40 and #50. Have you check Argo Project? It seems NO. Argo project the most serious study of the T and sea levels didn't observe increase in the T. It's true that it a new project (since 2005) but data is more accuracy.
Moderator Response:(Rob P) You can use the search function to find a response to most climate-related questions. For example on the observed warming of the oceans:
1. Ocean Cooling Corrected, Again
2. Levitus et al. Find Global Warming Continues to Heat the Oceans
3. Nuccitelli et al. (2012) Show that Global Warming Continues
4. Observed Warming of the Ocean and Atmosphere is Incompatible with Natural Variation
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R. Gates at 06:08 AM on 25 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
William,
That rising air and positive AO mght indeed happen (especially in the warmer months), in which case we might get more storms like the Great Arctic Cyclone of 2012 (early August 2012, to be exact). These storms not only bring up warmer water from depth, but also draw in more energy to the Arctic via the atmosphere as the strong low pressure pulls in wamer air from lower latitudes.
But there is another huge dynamic that I mentioned in my post #12 that must not be forgotten-- and that's the effects of SSW's on the AO. These events, happening mainly from late November through February, begin high above the Arctic, and with the warm descending air, turn the AO very negative, and push the colder air out of the Arctic and we ususally see warmer than normal temps in the Arctic proper. Most importantly, the causes of these events begins at lower latitudes, and are related to large-scale planetary waves whereby we can see the same SSW event having simultaneous (though opposite) effects over the pole and over the equator, 9000km away.
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Rob Honeycutt at 04:54 AM on 25 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Thanks Tom. I'm actually less stuck on the specific 97.1% figure that it may seem. The fact that all this research, taken collectively, and taking the fact that Cook13 is such a large sampling of research, should tell people how robust the conclusions actually are.
Again, I would challege any other group to perform a similar research project, using their own wording, and see if they can come up with appreciably different results. The point being, Barry, Lucia, Schollenberg and others can quibble until the cows come home, but until they do their own research (and get it published) they have little ground to stand on.
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Tom Curtis at 02:55 AM on 25 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Very briefly, all participants in this debate would do well to read Bray and Von Storch 2010 (particularly question 21, which shows that in 2008, 83.51% of climate scientists where significantly convinced that "most of recent or near future climate change is, or will be, a result of anthropogenic causes"). Note that this is not inconsistent with Cook et al 2013 because (a), climate scientists "convinced by the evidence" publish approximately twice as many papers on climate science on average relative to those unconvinced by the evidence (Anderegg et al, 2010), and (b), those not significantly convinced may well not be convinced for reasons other than the weight of evidence, and hence lag in proportion the balance of evidence as seen in the literature. It should place a constraint on the over interpretations and the absurd underinterpretations of Cook et al 2013.
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Alexandre at 02:51 AM on 25 May 2013Matt Ridley's misguided climate change policy
Lomborg is a slippery guy. He hardly claims anything, while conveying the unmistakable message that fossil fuels are all we need, and the environment is doing fine, and why do we have to conserve biodiversity after all?
He does not say we shouldn't stop deforesting, but he claims that worries about deforesting are grossly exaggerated, and even misrepresents the FAO report to prove it once and for all.
He does not say global warming is a hoax, but he knows of a climate model that miscalculated how much stratospheric warming there would be and, you know, that's what really matters.
He does not say we should not manage water resources properly, but he assures us that dessalinization is a definite safety net to dismiss any claims that people would ever endure water shortage.
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Tom Curtis at 02:44 AM on 25 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
This debate is getting irritating beyond belief, so I'll take advantage of a moments insomnia to stick my oar in.
Barry, you have shown that it is possible that authors used a more relaxed rating system than did the Consensus Project raters. You have not shown that using the more relaxed rating system significantly increases the number of papers rated as affirming the concensus, nor even that a significant number of authors used the more relaxed rating system. Even if half of papers self rated as affirming the consensus are given a neutral rating, the support for the consensus from self rated papers remains at 94.5% of all relevant papers. That shows how robust the results of the paper are; and that you must not just show the mere possibility of but the actuality of a difference in rating >>50% of affirmations if you wish to call the results into question. To my knowledge, no critic of the paper has even attempted to do so. At most they have argued for the mere possibility a less robust definition of "affirms agw" and then assumed that therefore >>50% of rated affirmations should have been rated neutrals.
Rob (and others), the near match in percentage of abstract rated and self rated papers rated as affirming the consensus (from relevant papers) is a product of a 1.9 fold increase by percentage of papers rated as affirming the consensus, a 2.6 fold increase by percentage of papers rejecting the consensus, the lack of a category for papers uncertain of the consensus, and an increased rate of return on recent papers (more likely to affirm the consensus) than older papers (which are less likely to affirm the consensus, particularly prior to 1995). Given that, it should largely be considered coincidental. What is robust about this result is not the 97%, but the 95%+ of papers which is difficult to eliminate by varying the data to account for potential biases.
I look forward with interest to further developments in this debate, and to when I have sufficient time to actively participate again.
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jdixon1980 at 01:55 AM on 25 May 2013On the value of consensus in climate communication
DSL, I noticed you mentioned FB - do you post a lot about AGW on your own timeline? If so, what has been your experience with the result of it?
In my case, I have been posting something about AGW impacts, green tech/policy developments on my timeline just about every weekday for the past several months (sometimes reposts from here, sometimes from David Roberts at Grist, sometimes from RenewEconomy, etc.). I think it results in some of my closer friends who are not "skeptics," but just aren't as independently interested in the subject as I am, reading more about AGW than they otherwise would because they see on their "news feed" that I posted something. Another effect is that a couple of my FB friends who are "skeptics" or "lukewarm skeptics" occasionally comment on my posts or even post their own links on my timeline, leading to discussions that my other friends often follow and chime in on. I don't think I've made a tremendous impact on the "skeptics." The closest thing to progress from a "skeptic" friend of mine was when he first posted (in his own WordPress blog) a reference to global warming as a "specious concept," and then in a later post of his musings on the theme of devoting our attention to the problems of the day, stated that for example he could donate to a global warming awareness organization, but he is "not convinced that climate change is a legitimate issue."
Going from proclaiming AGW as a "specious concept" to being "not convinced" is arguably some movement. But what mainly motivates me to post on FB is to use my timeline as a kind of "information hub" for the benefit of my friends and for my own benefit as well - I have a kind of half-baked organization scheme where I sometimes post related articles in the comments to a a previous article, for later reference...
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Rob Honeycutt at 01:27 AM on 25 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
HJones @209... But I believe with such a large data set, if there were a weakness it would have presented itself as pretty obvious. The big difference you see between the SkS raters and the self-ratings is that there are far fewer neutral papers. And that makes sense because the SkS raters were not reading the full papers.
The fact that the consensus figures for the SkS raters and the self-ratings are nearly identical suggests a high level of robustness in the results.
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Rob Honeycutt at 01:20 AM on 25 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Barry @208...
You are presenting a subjective analysis of what you believe about the survey which is going to reflect your personal biases. This is why science doesn't rely on any one piece of research to be the definitive answer on any question. We are all subject to our personal biases.
What makes Cook13 important is the fact that the conclusions independently confirm the previous research of Doran, Oreskes, Anderegg and others. Cook13 was also sufficiently blinded so that it would have been impossible for the raters to inadvertantly bias the ratings to come up with the same figures of previous research. And the data set is sufficiently large enough to also prevent biasing.
Then, on top of that, Cook13 took the added step of being self-skeptical by asking scientists to self-rate their own research based on the definitions used in the study. And the results there came out nearly identical with a 97.1% vs 97.2% consensus.
Could all these pieces of the puzzle falling exactly into place be completely happenstance? Highly unlikely!
Beyond that, it would be up to you, Barry, to come up with what you determined to be less ambiguous phrasing and then test your results. Based on how consistent these results have been I would guess any data you could compile would not be sufficiently different that those of any of these studies.
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jdixon1980 at 01:10 AM on 25 May 2013On the value of consensus in climate communication
I think this statement by DSL @1 is thought-provoking, and so I am going to take the liberty of plucking it out and repeating it, lest it get lost. It's only human to quickly skim through a multi-paragraph comment and maybe miss a gem like this:
"More powerful than ideology is the need to remain valuable, and that need is amplified when the discussion is public. No one wants to be dismissed out of hand--to be categorized, labeled, boxed, stamped as innocuous."
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HJones at 01:08 AM on 25 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
barry & John Hartz,
If enough respondants had a different ratings criteria to others, then the apparent corroboration between the 2 groups is undermined, weakening the results.
Another factor that can weaken the results is the fact that the authors were rating their papers, while the raters were rating the abstracts. Unless someone were to go through and re-evaluate some papers and check against the abstract rating, this level of weakenning will remain unknown.
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barry1487 at 00:37 AM on 25 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
John Hartz,
I have posted my thoughts on the paper upthread.
I think that the survey definitons are ambiguous, such that the criterion for rating the papers may have been different between the authors of the study (Cook et al), and the original Authors (the ~1200 that responded to the email and self-rated their papers).
The close match in ratings between the authors and the original Authors is a centrepiece of the corroboration of the results. If enough respondants had a different ratings criteria to others, then the apparent corroboration between the 2 groups is undermined, weakening the results.
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Dikran Marsupial at 20:12 PM on 24 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Prof Tung, regarding your most recent post: As I said, I think SkS readers are familiar with the idea of internal variability and would readily agree that internal variability is most likely the cause of the apparent hiatus. However, the abstract of your paper in JAS makes the claim that:
When the AMO index is included as a regressor (i.e., explanatory variable), the deduced multidecadal anthropogenic global warming trend is so impacted that previously deduced anthropogenic warming rates need to be substantially revised.
This is advancing a much stronger claim than that the hiatus is mot likely due to internal variability, but that some of the action of AMO has been misattributed to anthropogenic forcing. The only quantative support for this assertion seems to come from the regression model. In my example on the other thread I have shown that this regression model is flawed, and if AMO actually doesn't affect global mean surface temperatures (in your notation, the correct value of the regression coefficient D is precisely zero), then the regression method can misattribute some of the effects of anthropogenic forcing to the AMO.
In an earlier post, Prof. Tung wrote:
"The MLR analysis cannot stand on its own as evidence."
The MLR analysis is clearly the key element of the paper in JAS entitled "Deducing Multidecadal Anthropogenic Global Warming Trends Using Multiple Regression Analysis". For that paper to be sound, it is incumbent on you to be able to refute the counter example I have provided that shows the method is unreliable.
"I also mentioned in part 2 of my post that one could legitimately claim that use of either the Enfield AMO index or the Trenberth and Shea index is ciruclar, if that is the entirety of the evidence that you presented."
Enfield and Trenberth & Shea would only be circular if they used their detrended AMO indices to deduce the anthropogenic influence on global temperatures. There is nothing circular about detrending AMO to remove anthropogenic influence, the circularity is introduced by assuming a model of anthropogenic warming to detrend AMO and then using that detrended AMO to deduce the anthropogenic warming.
"Similarly, as you have done here, you assume the hypothetical case that the AMO is anthropogenically forced, but you do a MLR assuming it is instead mostly natural and remove it."
No, this is clearly not the case. In my example the AMO signal is a mixture of anthropogenic and natural. The point is that the detrending procedure, whether lienar or quadratic affects both the anthropogenic and natural components of the AMO signal. As a result the detrended AMO can still act as a proxy for anthropogenic warming, either because the detrending model was incorrect (in the case of lienar detrending) or becase the natural component is correlated with the anthropogenic signal (in the case of quadratic detrending).
"You can then demonstrate that the resulting anthropogenic response is wrong. That is, it is different than you originally assumed to be true."
The whole purpose of using a synthetic example is that I know that the resulting anthropogenic response is wrong as I know what the correct answer is by construction. The MLR method gives the wrong answer unless the AMO is detrended to remove the anthropogenic signal exactly, which can't be done unless you know what the anthropogenic signal is a-priori.
Conversely, if you consider the hypothetical case that the AMO is mostly natural, but you do not remove it, you would also get a wrong anthropogenic response in the end. This you could have known even before you do the Matlab calculation.
The AMO signal in my example is mostly natural. If the MLR method is sound, it needs to work whether the AMO is strongly affected by anthropogenic factors or not, and whether AMO affects global surface tempertures or not.
It is very important that you provide me with a direct answer to this question, so we can focuss in on the area of disagreement quickly: Ignoring for the moment whether the hypothetical scenario is appropriate, is there an error in my implementation of the MLR method? "Yes" or "No", if "Yes", please explain.
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MA Rodger at 20:06 PM on 24 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
KK Tung @111.
Thank you for pointing out the mention of the 'hiatus' in T&Zh13. It had passed me by. The actual quote is:-
"Recently, there have been debates about the slowing of the warming rates since 2005, with explanations (44–46) ranging from increases in stratospheric water vapor and background aerosol to increased coal burning in the emergent economy of China of the past 20 y. If one accepts the conclusion that the AMO is recurrent, and because this period coincides with the start of the descending phase of the AMO, one can suggest that the AMO is a more likely explanation."
In the first post here at SkSci, there was also the statement that the residuals following MLR with QCO2(t) function showed "a minor negative trend in the last decade" ie during this same 'hiatus' period'. Indeed, is this "minor negative trend" as shown in fig 3 of the first post not the 'hiatus' iself that remains unexplained by T&Zh13 when the actual AMO is used (although explained with a theoretical "recurrent" AMO.)? -
JasonB at 19:46 PM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
s_gordon_b,
Rob, again, based on my reading of the paper (please correct me if I'm wrong), your statement that the paper indicates that "97% of the research supports AGW" is the right conclusion. But that's not how the study is being (forgive me) spun.
Perhaps it would be easier to understand your point if you could point us to some examples of where the study is being spun?
Regarding the authors, again, they were asked to state whether each specific paper endorsed the proposition that anthropogenic GHGs are causing global warming, rejected the proposition that anthropogenic GHGs are causing global warming, or was neutral. If the author of the paper felt that their paper implied humans were having a minimal impact on global warming (e.g. by proposing an alternative as the main cause of global warming), or stated that human impact was minimal or non-existent, or stated that humans were causing less then half of global warming, then they would have categorised their own papers as rejecting the proposition.
I'm fairly confident that anyone who rejected the consensus view would have made damn sure their paper was counted as a rejection if it was at all possible to do so! And let's not forget that the authors of any papers who feel their paper should have been counted as a rejection are free to search for their paper in the results and alert us to the miscategorisation.
Anyway, the bottom line is that the authors of 97.2% of the papers that took a position stated that their papers endorsed the proposition that anthropogenic greenhouse gasses are causing global warming. That's it.
*I've looked everywhere, but I can't find where the numbers of abstracts assigned to each of the original Table 2 categories is or the category assignments by the study authors. Could you point me to that data?
http://www.skepticalscience.com/tcp.php?t=search
Perhaps you should spend some time reading the earlier comments to avoid rehashing the same points over and over again.
For a summary of the category assignments extracted from the database, see my earlier comment. The bottom line is that, ignoring neutral papers, the percentage of papers that endorse the consensus in each category are:
Papers that quantify the human contribution to global warming (i.e. level 1 vs level 7): 88%
Papers that make explicit statements about causation without quantification (2 vs 6): 98.4%
Papers that imply the impact that humans are having (3 vs 5): 98.2%
If we ignore all papers with implicit statements about the impact humans are having and only include those that make explicit statements about causation with and without quantification then we get 97.6%.
No matter which way you cut it, the results keep coming up the same.
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nealjking at 19:12 PM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
s_gordon_b:
As stated above, my interpretation of the meaning of the consensus is:
"Not that the human contribution is necessarily greater than 50%, but rather that it is important enough that we should be seriously thinking hard about whether we want to change what we are doing, on a global scale."
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s_gordon_b at 18:14 PM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
I keep submitting this, but it keeps not showing up. I'm sorry if it ends up appearing in triplicate:
Rob, again, based on my reading of the paper (please correct me if I'm wrong), your statement that the paper indicates that "97% of the research supports AGW" is the right conclusion. But that's not how the study is being (forgive me) spun. Evidence of 97% support/endorsement of a mostly* unquaintified degree of human causation (not the consensus) is being conflated with evidence of a 97% agreement with the consensus of predominant human causation. We criticize deniers and contrarians - indeed, SkS excels at this - for such sleights of hand. We should apply the same standard to "our" research. It's a good study, but unless someone can explain how and why I (and others who I now see have raised the same question) have got it wrong, the presentation of the study is not good.The study also attributes agreement with the consensus to >97% of the authors, based on their ratings (from the anstract: "Among self-rated papers expressing a position on AGW, 97.2% endorsed the consensus"). Reading the paper and the supplementary data, it again appears that the authors' 1-7 ratings were then aggregated in the same way as the reviewers' ratings, potentially conflating the popular (non-consensus) view that "people are at least responsible for some of the warming" with the consensus of the IPCC and, I think it's safe to guess (but not from this paper), most climate scientists.**
*I've looked everywhere, but I can't find where the numbers of abstracts assigned to each of the original Table 2 categories is or the category assignments by the study authors. Could you point me to that data?
**It's too bad the authors weren't asked for their views on the consensus, apart from what their papers had or had not said. The last survey had answers from less than 100 climate scientists. This study's sample size of ~1200 would probably have included hundreds more or even all of them, inasmuch as they were publishing papers on climate science regardless of their discipline.
Moderator Response:[JH] The two prior duplicate posts have been deleted.]
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william5331 at 16:29 PM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
It should be interesting when the Arctic is ice free for three or four months of the year. We should see rising air over the arctic and the mother of all positive AO's. If the jet stream is weakening even now, will it disappear all together and a two cell system develop in the northern hemisphere. Perhaps this explains the observation of hemlock pollin 3.6m years ago in that unpronouncable impact lake in Russia. A persistant low over the Arctic much of the year would reverse the Beaufort gyre, flinging the surface cold somewhat fresh water in to the Transpolar drift and out through the Fram Straight. Once the ice is gone and the halocline greatly reduced, it would be hard to reestablish ice cover.
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citizenschallenge at 15:14 PM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Nice post post John.
I found that it shoe-horned with a recent happening in the states where a Senator Whitehouse gave a strong speech about global warming and extreme weather, while the Moore OK tornado was happening.
Of course Republicans are trying to twist what happen and what he said.
In any event, thank's again for allowing us to repost these articles:
Thursday, May 23, 2013
"Explaining why Senator Whitehouse's claims are accurate"
In light of Senator Whitehouse's claims, I thought this lesson, based on up to date information - explaining what scientists are observing within the Arctic Circle and the implications of those observations.
It's a recent post from SkepticalScience.com that has the most comprehensive collection of digestible information I've seen to date about our Jet Stream. Considering how much the Jet Stream influences weather this is an informative article that should be read as supplement to Senator Whitehouse's attempt to wake up Republican Senators to the stakes they are gambling away.
Thanks again to SkepticalScience.com for making these posts available to folks like me.
===========
Also:
"Senator Whitehouse and the Moore Oklahoma tornado"
http://whatsupwiththatwatts.blogspot.com/2013/05/senator-whitehouse-and-moore-oklahoma.html
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JasonB at 12:56 PM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
There is a reason why the email asked the original authors whether their paper endorsed such a simple, "common speech" statement without definitions of each word — it's so that their answer can be reported to the general public in the same terms.
Actually, there was one definition: "human activity (i.e. anthropogenic greenhouse gases)". This narrowing of "human activity" to just anthropogenic GHGs allows them to state that the consensus relates to GHGs without anyone being able to muddy the waters by claiming that some scientists might have been talking about other activities like land clearing.
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Riduna at 12:54 PM on 24 May 2013Matt Ridley's misguided climate change policy
Climate sensitivity is found by the IPCC to be ~3.5C, a value confirmed by paleoclimate studies undertaken by Hansen and others and is widely accepted. Dr Otto et al, using data covering a relatively short period (too short?) has found that sensitivity appears to be significantly lower.
Ridley concludes from this that public policy on curbing anthropogenic carbon emissions is misplaced, damaging and should be slowed. He comes to this conclusion without accurately quantifying and estimating the effect of slow feedbacks over next 87 years of this century or their capacity to fully off-set the Dr Otto's findings by 2100.
Those feedbacks include loss of albedo, methane and carbon dioxide emissions trapped in and under permafrost and increased water vapour due to atmospheric warming. Nor can we ignore increasing ocean heat content and the likelihood of its release to the atmosphere, accelerating feedbacks.
The speed with which feedbacks are now developing is more likely to increase rather than lower the rate of global warming. To interpret the findings of Dr Otto et al as indicating that we may have a decade or so longer in which to curb anthropogenic emissions is, in my view, the height of folly.
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Eric (skeptic) at 12:13 PM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
R Gates, I think my question also applies to SSW, but it may not. It appears that models have improved a lot in coupling the stratosphere to the troposhpere. The theory of SSW includes many factors including solar plus feedback with weather in the troposphere and ozone in the stratosphere. The feedback with the troposphere could include some changes due to a decreased tempeature gradient from global warming but generally the gradient is so large during these events it is hard to imagine an impact from that long term trend. Also difficult because those events are relatively rare.
Chris, that makes sense although I'm not sure of the implications for the positioning and strength of the polar jet.
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JasonB at 10:27 AM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
nealjking,
In my view, it has to be understood as "common speech"
Precisely. There is a reason why the email asked the original authors whether their paper endorsed such a simple, "common speech" statement without definitions of each word — it's so that their answer can be reported to the general public in the same terms.
Consider the fact that laws are full of such undefined terms, like "reasonable". Probably the most famous of these is the phrase "guilty beyond reasonable doubt". The reason that they don't tell you, as a jury member, how you are "supposed" to interpret that is precisely because they want you to bring your own definition to the table. Get a large enough group of people together and the opinion of the majority will be an effective "poll" on what the word is supposed to mean.
Likewise, ask a few thousand scientists whether or not their papers endorse the proposition that human activity is causing global warming and you can be sure that the majority are going to interpret that in the same way as the majority of the populace. It doesn't matter if a few scientists here and there have odd interpretations, or a few members of the public have odd interpretations, overall they will agree.
The only exception to this rule is when the scientists have a reason for systematically interpreting it differently to the general population, and in this case it could well be true, because these scientists are climate scientists, and they can hardly be unaware of the IPCC's statement of consensus, which is that "human activity is very likely causing most of the current GW". Given that, it is entirely reasonable to assume that those scientists answered an even stronger interpretation of the statement than what the general population would assume it to mean, but this possibility does no favours to those who wish to nitpick.
The bottom line is that several thousand scientists, when asked to asses their own papers — so there was no need for them to try to interpret what they wrote, they knew exactly what they were trying to say — responded by claiming that 97.2% of those that addressed the question at hand endorsed the statement that human activity is causing global warming.
This is profound for two reasons: 1) It shows that a large number of scientists, independently interpreting both the meaning of that phrase and their own papers, arrived at the same level of endorsement as Cook et al did looking only at their abstracts, and 2) it did so while at the same time enormously growing the percentage of papers that actually addressed the question, that Cook et al were forced to categorise as "neutral". Incredible.
Arguments over whether levels 2 or 3 endorse the proposition that humans are the "dominant" cause, or a "signficant" cause, or "> 50%", are seriously missing the point, just like those insisting that "reasonble" be precisely defined. If the scientists wanted to convey lesser degrees of human involvement, they could have chosen level 5, or level 6, or level 7, depending on how it was conveyed in their paper. The fact that the overwhelming majority of them didn't speaks volumes. Levels 2 and 3 cannot be read in isolation, and the fact that both have the worse "endorse" in the title cannot be ignored.
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KK Tung at 07:18 AM on 24 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
In reply to post 104 on the relevance of the recent hiatus to the present thread on the Tung and Zhou (2013) paper: That paper offered one possible explanation for the observed hiatus observed since 2005, as due to a recurrent internal variability. Therefore it is relevant (thank you, Dikran, for pointing this out in post 105). There are many other suggestions, including coal burning in the emergent economy of China (Kaufmann et al. [2011] ), increases in stratospheric water (Solomon et al. [2010] ), or increases in “background” stratospheric aerosol (Solomon et al. [2011] ). I in no time suggested that ours is the only explanation. The most recent explanation is that the heating from the greenhouse gas induced radiative imbalance goes into the deep ocean. There are two timely paper by Jerry Meehl and his co-workers: One is published in 2011 in Nature Climate Change,vol 1, page 360-364, entitled : "Model based evidence of deep ocean heat uptake during surface temperature hiatus periods". The other is currently under consideration at J. Climate, entitled "Externally forced and internally generated decadal climate variability associated with the Interdecadal Pacific Oscillation". They are very relevant to our current thread.
Meehl et al used CCSM4 model run with a future scenario (RCP4.5), which does not have oscillatory variations in the forcing or dips such as those by volcano eruptions. With smooth forcing, the 5-member ensemble mean model global mean temperature is also smoothly increasing. However the individual members show variability about the mean of around 0.5 K from peak to trough. These papers are not about how good the model is in comparison with observation.
From an energy balance standpoint, the top of the atmosphere radiative imbalance driven by the anthropogenic forcing should be accounted for mostly by the heat uptake in the oceans, as land and ice have much lower heat capacity. In the model this heat budget can be done exactly. Meehl et al defined the hiatus period as when the surface temperature has a negative trend even in the presence of increasing radiative driving. They found that during the hiatus period, the composite mean shows that the upper ocean takes significantly less heat whereas the ocean below 300m takes up significantly more, as compared with the non-hiatus period. The second paper compares hiatus periods with accelerated warming periods, and finds the opposite behavior: the upper ocean takes up more heat and the deeper ocean much less.
The question is, what causes some periods to have more heat going into the deep ocean while some other periods the heat staying more in the upper ocean? I suggest that this is caused by the internal variability that we were discussing earlier. Our previous exchanges hopefully established the viewpoint that we should view the ensemble mean as the forced solution and the deviations from the ensemble mean by each member as internal variability. There are no hiatus periods in the forced solution under the CCSM4 RCP4.5 experimental setup. In fact this solution is smoothly increasing in its global mean temperature. It is the internal variability, possibly associated with variations in the deep overtuning circulations in the oceans, which determines when a portion of the heat should go to the deep ocean and show up as warming hiatus, and when it should stay near the surface, and show up as accelerated warming. ENSO, which we generally view as internal variability, also has this kind of vertical distribution variability in the oceans: In La Nina, the upper ocean is cool while the heat goes to the deeper ocean, and opposite behavior in El Nino.
The CCSM4 is known to have internal variability that is faster than in the observation. Instead of having hiatus periods of about 2-3 decades in the observation its cooling periods last 1-2 decades. This may possibly be caused by too rapid a vertical mixing in the ocean but I do not know for sure. The Interdecadal Pacific Oscillation (IPO) that was discussed by Meehl et al is the low frequency portion of the Pacific Decadal Oscillation (PDO). In the observation the IPO cooling periods coincides with the cooling periods of the AMO, which led me to suspect that the IPO is just the Pacific manifestation of the AMO, which is caused by the variations of the Atlantic Meridional Overturning Circulation.
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From Peru at 06:41 AM on 24 May 2013Matt Ridley's misguided climate change policy
"committed climate change damage of $2.4 trillion, or over 3% of the global gross domestic product"
Well, this cost depends on the social discount rate r (among a lot of other variables) the lower the social discount rate, the higher the cost:
Present value(cost) of pollution = Σ (future damage of year i)/(1+r)i......(summed over i; i is the number of years in the future)
But the social discount rate is a function of economic growth:
r = δ +γ g,
Where:
- r is the discount rate
- δ is the so-called "rate of impacience"
- γ is a parameter called " aversion to intertemporal inequality"
- g is economic growth
[source: Christian Gollier, Pricing the future:The economics of discounting and sustainable development, Toulouse School of Economics, 2011]
δ is set to zero for intergenerational timescales, leaving r as just a function of γ and g.
Now if the economy is seriously damaged by climate disasters, g will turn smaller, lowering the discount rate and so raising the present value of future damages.
I don't know how low can the discount rate fall. So:
Could it fall below zero, making the present value of damages to skyrocket?
Is this subtle effect accounted when the cost of CO2 is calculated?
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John Hartz at 06:38 AM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
@Barry 201:
Speaking for myself, I do not find it terribly useful for you to define one gneral term, i.e., academic merit, with another general term, i.e., quality of scholarship. What is generally accepted set of standards which are associtaed with these terms? (Source please.)
In your opinion, which of the standards were violated by Cook et al 2013?
Do you believe that the editors of Environmental Research Letters deliberately ignored certain standards when they published Cook et al 2013?
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Chris Colose at 06:19 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Eric #9
The mechanisms behind jet changes (strength, latitudinal shifts, etc) are still pretty hot topics in dynamical meteorology. I tend to agree, however, that increases in the upper tropospheric pole-to-equator temperature gradient may be more important than the (fairly shallow) decrease in surface pole-to-equator temperature gradient.In fact, because the tropopause slopes downward as you move poleward, if you are floating at a fixed level in the atmosphere near the tropical tropopause you are initially in a region of strong warmer (the "hotspot") but if you moved polewards at that level, you'd eventually end up in a region that was cooling in a global warming scenario. That has a lot of implications for dynamics, since gradients in wind velocity are directly proportional to horizontal temperature gradients.
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MA Rodger at 06:10 AM on 24 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
So where to look for evidence of AMO warming beyond the shores of the N Atlantic?
My first thought was that if AMO was going to effect temperatures anywhere, it would be the UK. Indeed, the CET was invoked within T&Zh13. So I compared CET with the SST for the surrounding seas (45-65N, 20W-10E) with nomad3 providing monthly SST data - 1981 to date. The two temperature profiles are re-based for comparison and graphed below. with AMO also plotted (although AMO is of course subject to a de-trending).
The divergent record is evidently CET not the SST which suggests that during these divergent periods, AMO is not in any way a dominant influence in CET. So are divergent periods infrequent such that the period 1988-2004 is the norm where SST & CET can be married together?
A de-trended CET for the period of Enfield's AMO index (1856 to date) is next up for comparison being graphed below. Divergence appears the normal state here, with the two indices have little in common. I would conclude that the CET record does not support the suggestion that AMO drives UK temperatures.
Still. It's early days. There may yet be that local variation is swamping the signs of the AMO driving UK temperatures. And the UK is not the whole globe. -
Dumb Scientist at 05:56 AM on 24 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
As I discussed in part 2 of the post, the MLR analysis follows the arguments laying out the evidence in favor of the AMO being mostly natural. [KK Tung]
Again, I don't think that's the issue. Removing the AMO to determine anthropogenic warming would only be justified if detrending the AMO from 1856-2011 actually removed the trend due to anthropogenic warming.
The MLR analysis cannot stand on its own as evidence. If that were what we did in our PNAS paper, then our arguments would have indeed been circular.
Those arguments aren't sufficient to support your claim that ~40% of the warming over the last 50 years can be attributed to a single mode of internal variability. Especially because Isaac Held and Huber and Knutti 2012 used thermodynamics to conclude that all modes of internal variability put together couldn't be responsible for more than about 25% of the warming.
Similarly, as you have done here, you assume the hypothetical case that the AMO is anthropogenically forced, but you do a MLR assuming it is instead mostly natural and remove it.
Actually, Dikran's analysis defines the AMO as 40% anthropogenic and 60% natural. So it is mostly natural.
But again, I think the key point is that linear detrending doesn't remove the nonlinear anthropogenic trend from the AMO.
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KR at 05:46 AM on 24 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dr. Tung - I would agree that the identification of the AMO is critical for attribution analysis. I would disagree on the AMO index you used.
You used the CET as an AMO proxy - however the CET is equally vulnerable to aliasing (hiding) the global warming signal. Frequency analysis in this case is suspect, as the sum forcings in the 20th century (GISS forcings here), when averaged out by climate response times, have a frequency similar to that of the AMO observations - and are therefore not directly separable using just time series analysis.
---
I am in addition greatly disappointed that you have (as yet) failed to respond to my points regarding the Ting et al 2009 analysis (time/spatial principal component analysis supporting the Trenberth Shea 2006 detrending method, not linear detrending) or to ocean heat content thermodynamic constraints (upper limits on contributions from internal variation), as raised here. Either of these points indicate a much different anthropogenic contribution to current temperatures.
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MA Rodger at 04:57 AM on 24 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
Dikran Marsupial @62.
I can agree almost fully with your comment. Perhaps the use of Occam's razor needs wielding with care so it doesn't become Occam's broom (sweeping stuff under the carpet, out of sight).
The point with the 'chipping away' idea is that just as CAN BE is distinct from IS, so it is also distinct from IS NOT. Thus, while our inabilities in removing the AGW signal from AMO would seemingly present an insurmountable problem for the T&Zh13 method, the question of how much of recent global warming is AMO and not AGW will remain unanswered.
So I'm thinking of looking to see if there are signs of AMO warming beyond the N Atlantic, or signs of non-AMO warming. A tiny bit of harmless analysis. But frankly analysis that I feel should have been done already. Perhaps it has & I missed it. Perhaps not.
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KK Tung at 04:42 AM on 24 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Regarding the Matlab code result of Dikran mentioned in post 106 and by DumbScientist earlier:
I am frustrated that I have not been able to get my point across despite a few attempts, as you continue to focus on a technical procedure, the multiple linear regression analysis (MLR). As I discussed in part 2 of the post, the MLR analysis follows the arguments laying out the evidence in favor of the AMO being mostly natural. The MLR is then used to see the possible impact it may have on the deduced anthropogenic warming rate assuming that the AMO is mostly natural. The MLR analysis cannot stand on its own as evidence. If that were what we did in our PNAS paper, then our arguments would have indeed been circular.
I also mentioned in part 2 of my post that one could legitimately claim that use of either the Enfield AMO index or the Trenberth and Shea index is ciruclar, if that is the entirety of the evidence that you presented. Similarly, as you have done here, you assume the hypothetical case that the AMO is anthropogenically forced, but you do a MLR assuming it is instead mostly natural and remove it. You can then demonstrate that the resulting anthropogenic response is wrong. That is, it is different than you originally assumed to be true. Conversely, if you consider the hypothetical case that the AMO is mostly natural, but you do not remove it, you would also get a wrong anthropogenic response in the end. This you could have known even before you do the Matlab calculation.
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rockytom at 04:21 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
John, another fantastic article with the best graphics I've seen integrated with the text. I wish we (John Cook and I) had had the graphics when writing our textbook (Climate Change Science: A Modern Synthesis) as we certainly would have included at least some of them (with permissions, of course).
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KK Tung at 04:09 AM on 24 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
In reply to post 106 by Dikran: The effect of offsetting on the perceived spread of models has been underdiscussed in literature. I agree with what you said about it here, and I would encourage you to develop it into a publishable paper. The procedure of offsetting with a baseline is needed for model projections because projection is different from a prediction. In a prediction of ,say weather for the next few days, today's measured weather is our baseline, and such a baseline is assimulated into the model. The model attempts to predict both the forced and unforced response. Due to chaos, models start to deviate after today, and after two weeks, the prediction becomes mostly useless. But it is useful for a week or so.
The IPCC projections of future climate change is different. The model is initiated in the preindustrial period, 1850-1870, runs about 150 years in the 20th century simulation (when what is to be simulated is known), and then runs forward under different scenarios of future emissions. There is no hope of doing a prediction of both the forced and unforced response over such a long period. Instead it is hoped that the forced response of the climate is simulated with the ensemble mean of the model runs. If, in the presentation of the results, all models are offset against their initial condition at 1850-1870. The intermodel spread is rather large, even during the period of 20th simulation, where the observed response is known before hand. This is caused by systematic errors in each model. This intermodel spread is reduced by offsetting each model's ensemble mean by its own climatology in a specified period, say 1980-1999, as used in Chapter 10 of AR4. It reduced the intermodel spread during the period of offset, and also for a decade or so after that. AR4 uses different offsetting period in different chapters, and there is no consensus on how to do it. You have found that a longer offsetting period makes the pre-2000 results less anomalous. On the other hand, for the purpose of evaluating projections to the future, perhaps it may be fairer to the models to offset it with the lates known data. That is, year 2000 for AR4 projection and year 2005 for the CMIP5 projection. We however do not know what the observed forced response is, but since AR4 models have simulated the observed 20th warming quite well with forced (ensemble mean) solutions, it may not be a bad idea to offset the model prediction at year 2000 for AR4 projection with the observation at year 2000, and then attribute the subsequent deviation of the model ensemble mean from the observation to the presence of internal variability. Have you tried it yet?
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R. Gates at 03:34 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Wow, fantastic post. Lot's a great information. One bit of information, perhaps advanced but very important for understanding a negative AO index at certain times of the winter and the havoc it can bring to lower latitudes. Sudden Stratospheric Warming events (SSW's) where air is descending over the pole form the upper stratosphere and even the mesosphere bring of course high pressure over the pole, warming, and often times a very negative AO index. These SSW events in essence "open the freezer door" on the Arctic and shunt this very cold air down to lower latitudes. The normal winter westerlies turn to easterlies as the Polar Vortex is often shattered, and you get real nasty weather at lower latitudes. Looking back historically, very negative AO events in the winter are highly correlated with these very disruptive SSW events.
But again, a great article!
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nealjking at 03:00 AM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
s_gordon_b:
You wrote:
"Categories 2 and 3 are too ambiguous - as defined in table 2 - to equate to the consensus that humans are not only a cause of industrial era global warming but the dominant cause since the middle of the last century (at least). Am I not reading that right? And if so, shouldn't only those abstracts that take an unambiguous stand on the consensus of dominant human causation be counted and the others excluded in the same way that abstracts that take no stand at all were excluded?"
From looking at the paper, what I find as the first statement of the consensus (in the abstract) is: “Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming.” So the definition of the consensus position is that “humans are causing global warming”. But how is this to be understood?
In my view, it has to be understood as "common speech": When the proverbial “man in the street” asks the question, “Are we (humans) causing global warming?”, he is NOT necessarily asking, “Is the degree of responsibility for global warming that is due to human activity greater than 50%?” or "Is human activity the dominant cause of global warming?" He is asking something much closer to, “Is human activity contributing to global warming big enough that we ought to be doing something different?” And I believe most scientists would agree with this understanding of the AGW issue: Not that the human contribution is necessarily greater than 50%, but rather that it is important enough that we should be seriously thinking hard about whether we want to change what we are doing, on a global scale.
My understanding of the Levels of Endorsement (LOEs) 2 & 3 is that they indicate agreement, explicit or implicit, with the spirit of the underlined statement above, which I regard as a filled-out "common speech" version of the statement in the abstract.
Therefore, I have no doubts about including LOEs 1 - 3 together as indicating support for the AGW consensus.
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barry1487 at 02:39 AM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
John Hartz,
What exactly do you mean when you use the phrase, "academic merit"?
Quality of scholarship..
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Dumb Scientist at 02:33 AM on 24 May 2013Has the rate of surface warming changed? 16 years revisited
jdixon @27: Sure, just return it when you're done so I can use it again. ;)
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John Mason at 02:04 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Eric - interesting question. I'll have a read of those papers and get back to you in a few days. However one point I would make is that because the Tropopause is such a strong temperature inversion, convective heat transfer between the troposphere and stratosphere is effectively blocked. I would therefore suggest the troposphere plays the main role.
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jdixon1980 at 01:46 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Wow that's a lot of info without having to buy a meteorology textbook - will have to look this one over a few times to absorb it.
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Eric (skeptic) at 01:15 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Good article. My main question is about how this explanation fits with prior explanations of changes in AO. For example: <A HREF="ftp://psrd.hawaii.edu/engels/Stanley/Textbook_update/Science_297/Moritz-02.pdf">ftp://psrd.hawaii.edu/engels/Stanley/Textbook_update/Science_297/Moritz-02.pdf</A> The explanation in this 2002 paper seems to be that GHG cooling of the lower stratosphere leads to an increased vertical gradient and a stronger polar jet. The explanation above seems to focus on the decreased horizontal temperature gradient causing a weaker jet. Is one gradient more important than the other? My opinion is that the 1950-present chart above appears to be mostly natural variation.
A question specific to Sandy is that the left turn came not just from blocking but from Sandy phasing with a strong short wave riding on the deeply diving longwave jet. I'm not sure why there would be any natural or GHG-induced trend in the strength of the short waves because their strength seems to depend on local temperature contrasts that greatly exceed any of the trends in wide scale temperature contrasts from GHG or natural cycles.
Finally, Andrew Freedman has a good perspective on climate change and tornadoes <A HREF="http://www.climatecentral.org/news/making-sense-of-the-moore-tornado-in-a-climate-context-16021">http://www.climatecentral.org/news/making-sense-of-the-moore-tornado-in-a-climate-context-16021</A> with a focus on strong tornadoes only.
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jyyh at 01:03 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Thanks for this informative post. I find it's a bit sad case that scientific articles like this one get pretty quickly buried in other kinds of articles on politics, opinions and rebuttals of denialist bullshit. After reading this, I remembered there was a good article on SkS about Sudden Stratospheric Warmings breaking the polar jet stream just recently... after some 10 minute searching I wasn't sure of it anymore. Eventually I found it. It's here :-D : http://neven1.typepad.com/blog/2013/04/sudden-stratospheric-warmings-causes-effects.html
I might some day (or week or two) go through the entire archives of climatology blogosphere to seek these kinds of articles I've found clear and approachable to my level students of climate, but as of yet this hasn't happened. I'll note here if I get to it. Thanks again.
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jdixon1980 at 00:31 AM on 24 May 2013Has the rate of surface warming changed? 16 years revisited
DS @21 I like the water sloshing analogy better than the "flywheel" or the yo-yo because of the built-in illustration of measurement at a single location - I assume you don't mind if I borrow it?
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Rob Honeycutt at 00:27 AM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
s_gordon_g... Instead of trying to over interpret the exact wording, take a step backward and look at big picture.
~97% of the research supports AGW.
~3% of the research rejects AGW.
The way you're approaching it, you're completely missing the forest for the trees. This is a common "skeptic" tactic when faced with data they don't like.
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John Mason at 23:04 PM on 23 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Chris, I'll split up your many questions and attempt to answer them in bold type:
Polar jet stream, is maybe a bit confusing sicne the southern antarctic oscillation is also a polar jet stream?
Yes, there is also a southern polar jet, but this post is specifically with regard to the Northern Hemisphere.
Polar air intrusion during the winter because of the higher jet stream amplitude. The UK will likely expereince much more pronounced floods, with Jet Stream blocking patterns, when the rain system just keeps sitting there.
This can be the case but more typically from a blocked pattern in summer - when it's warmer then the air can contain more moisture. Winter blocks tend to produce pronounced cold spells.
What about downward bursts/microburst?
These are features associated with high-precipitation thunderstorms and so occur in highly unstable atmospheric environments - an approaching upper trough with its attendant PVA will encourage mass ascent of air, but downbursts are storm-scale features.
Greenland is according to Jennifer Francis a prime spot for blocking patterns to occur, see Sandy - caused 90 degree turn.
Yes WRT Greenland, with stubborn high pressure over it and linking down to the Azores High being a good example of a blocked setup. The upper pattern played a part WRT Sandy's course, but I'm not sure of the exact figure without looking it up.
Where exactly is the Jet Stream, if not with the Jetstreaks?
See the diagrams up-post
Are these visible from the ground - do they come with clouds or is this different?
Cirrus can occur within jetstreaks and is obvious as it's moving rapidly. But in general no.
In regards to tornadoes and Jet Stream:“As with hurricanes, I think frequency needs to be separated from intensity.Climate change increases the available energy for tornadoes through a warmer and moister atmosphere. Wind shear decreases in the global mean, but this might be irrelevant locally when the jet stream dives southward like it did last weekend across the Plains.“I believe there is evidence that the strongest tornadoes are getting stronger. They are certainly getting longer and wider.” - James B. Elsner, an atmospheric scientist at Florida State University Humid air and the Jet Stream help to fuel more intense thunderstorms/tornadoes
Joe Romm has a post-Moore, OK, review of tornado climatology at Climate Progress:
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Dikran Marsupial at 21:31 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
MA Rodger The degree to which Prof. Tung's method over- or under-estimates the true anthropogenic component depends on both the true "noise" (the variation not due to the factors explicitly included in the model - note this is not necessarily the same as the residuals from the regression) and on the nature of the non-anthropogenic factors. As linear and quadratic detrending are correllation based methods, they are highly susceptible to any correlation or anti-correlation between the anthropogenic and non-anthropogenic components of the AMO. Similarly any flaw in the detrending of the AMO that is correllated or anti-correlated with the noise in the observations may be exploited by the regression procedure.
Essentially Prof. Tung's regression approach appears only to be workable if we can eliminate the anthropogenic influence on AMO exactly without attenuating any of the non-anthropogenic component. We can't do this unless we already know what exactly the anthropogenic influence on AMO actually is. I don't think this is "chipping away"; if my analysis turns out to be correct (and I have no problem with being wrong - it is part of normal scientific procedure!) then the whole regression procedure is invalid and hence does not support the conclusion.
Even when valid, regression methods can only really show that something CAN BE explained by something else, not that something IS explained by something else. We really need physics to determine whether AMO actually does influence GMST. The work of Foster and Rahmstorf shows that we don't need AMO to explain the "hiatus" as it CAN BE explained using ENSO etc. Occam's razor suggests we shouldn't needlesly introduce new elements if an existing theory already explains the observations already; however that doesn't mean that AMO has no effect on GMST.
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Dikran Marsupial at 21:04 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Prof Tung writes
"When the observation is below the model ensemble mean, I tentatively suggest that the explanation could be that there is an internal variability that is in a cool phase in the observation but is not (and should not be) in the model ensemble mean."
Yes, I think that the majority of SkS readers would agree that the ensemble mean is probably the best method we currently have for estimating the forced response of the climate system and that any difference between the observations and the ensemble mean can be explained as being due to the unforced response due to sources of internal climate variability. This is of course, provided the difference is approximately within the spread of the ensemble (in reality this is probably an underestimate of the true uncertainty due to the small number of model runs and the limited number of models).
"The point I made previously was why we need it now during the hiatus period and not during the period of accelerated warming."
I do not agree with this statement. There are multiple sources of internal climate variability, which include for example ENSO and plausibly AMO. Most of the time these will be acting to warm or cool the climate essentially at random, and so most of the time might be expected to largely cancel out. This is why the ensemble mean, while being an estimate of only the forced response, is still a reasonable point estimate of the observed climate. However, sometimes multiple sources of internal variability may temporarily align in direction, causing the observed climate to stray away from average conditions. Under such circumstances one would expect the observations to stay reasonably close to the forced response most of the time, but for there to be occasional periods of little or no warming, or conversely more warming than expected.
Easterling and Wehner (2009) investigated this issue in some detail and found that
"...periods of no trend or even cooling of the globally averaged surface air temperature are found in the last 34 years of the observed record, and in climate model simulations of the 20th and 21st century forced with increasing greenhouse gases. We show that the climate over the 21st century can and likely will produce periods of a decade or two where the globally averaged surface air temperature shows no trend or even slight cooling in the presence of longer-term warming."
In other words, we should expect to see the occasional "hiatus" ocurr due to internal climate variability, the models predict that they will happen if you wait long enough, but being chaotic phenomena the models cannot predict when they will happen. As far as I can see, there is little evidence that the models need internal variability more in recent years than they did before.
It is also worth noting that the issue to do with baselines may look as if the observations were more central in the spread of the models during the baseline period as baselining removes any offset between timeseries exactly within the baseline period, but only approximately outside. Some of these offsets will be due to random rather than systematic differences, so the apparent uncertainty of the models in the baseline period will be lower than outside the baseline period. This effect will be smaller the longer the baseline period, as shown in my earlier post, but I suspect it does contribute to the observations looking less "anomalous" during the pre 2000 years than perhaps they should.
I think it is very important to be highly skeptical of phenomenon that seem obvious from a visual inspection of the data. The human eye is very prone to seeing patterns in noise that don't actually mean anything. We should be reticent in claiming that there has been a real hiatus until there is statistically significant evidence for that assertion.
Incidentally, as Dumb Scientist points out, I have also made two posts in the previous thread addressing the issue of circularity, which seems to suggest that the regression method proposed does involve circularity. The posts are here and here. If you are a MATLAB user, I can send you the scrips used to perform the analysis.
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MA Rodger at 20:39 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
Dikran Marsupial @57.
Assuming your method holds up, you have illustrated that by subtracting the AMO signal from global temperature to reveal the AGW, you can be also inadvertantly be subtracting a significant amount of AGW. Your "Question 2" @16 thus stands now with evidential support.
Commendable stuff but....
The question that would perhaps follow would concern whether the proportions shown within the example you present (ie that 33% of the AGW signal is lost by subtracting AMO in this manner) are sensitive or insensitive to the situation. Will it always be about 33% or will it sometimes be much more, or less.
And I am far more sceptical about T&Zh13., I feel this chipping away is not the best approach. Indeed I remain sceptical that there can be any significant contribution to the global temperature anomaly from AMO.
One point I would make runs as follows - If global temperature wobbles 0.3ºC peak-to-peak due to AMO (as T&Zh13 asserts) and if 67% of this is resulting naturally from AMO (ie if we factor in the suggested finding @57 = 0.2ºC) then how much energy will be required to wobble the global temperature that amount? With TRC=2ºC (this is one place where contrarians would find high Climate Sensitivity useful), the global wobble would require a forcing equatable to 10% of 2xCO2 or 0.37Wm^-2 or an energy flux of 6ZJ pa. If this energy flux originates solely in the N Atlantic (ie if it is a direct energy output of the AMO), it will incur significant losses as it spreads out around the world. If the AMO has some deliverable other than 'heating of the climate' then the T&Zh13 thesis has some explaining to do.I think I will go in search of my 6+ZJ pa. It is rather a large quantity to go unnoticed.
I suppose my feeling on all this is that the AMO is simply an ocean waggling like a continent and is driving zip. But such comment here is pure speculation. And I am prepared to admit as much.
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Dikran Marsupial at 20:36 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
MA Rodger It seems to me that Prof. Tung has introduced the "hiatus" largely as a way of establishing the existence of internal variability, although I think the majority of SkS readers will already accept that without the need for it to be stated explicitly.
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