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dana1981 at 02:58 AM on 14 April 2013Real Skepticism About the New Marcott 'Hockey Stick'
I would also strongly suggest that Brandon read the blog post that he's commenting on.
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Bob Loblaw at 02:39 AM on 14 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
Dr. Tung:
Please consider all the comments about the inclusion of temperature in the calculation of AMO - this is an issue that is important. ENSO has been mentioned in this context, as a phenomenon that can be defined without using temperature as part of the calculation (e.g. here).
Note that ENSO, meaning El Nino - Southern Oscillation is made up of two phenomena that were identified independently before they were recognized as being related. The Southern Oscillation Inex (SOI) was originally identified solely from the pressure difference between Tahiti and Darwin, and it was recognized that it varied over time and could be related to weather changes. El Nino was a phenomenon related to ocean temperatures (and its effect on weather and fishing off the coast of S. America) Only later was the physical link between the two recognized and explained (and research continues). The fact that SOI can be calculated without measurements of T is important - even if the pressure is related to T through atmospheric dynamics, there is an independence of SOI as a numerical value from any T results you want to look at.
In a T=f(x, other terms) situation, you need to be sure that your arrangement of terms doesn't have you looking at a T=f(x)*f(T) situation. What people are suggesting is that you have phrased things as T=f(x)*f(AMO) + other terms, but because f(AMO) includes an f(T) component, you are not properly isolating T on the left side of the equation. Writing the equation as f(AMO) only hides the fact that you are writing T=f(T) - a substitution of the AMO=f(T) relationship shows clearly that you have a T=f(T) equation.
It might help if you can provide part II of your response soon - that may help focus the discussion.
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Real Skepticism About the New Marcott 'Hockey Stick'
Brandon Shollenberger - If Marcott et al had aligned their reconstruction with modern instrumental temperatures on just the last 150 years of their reconstruction, which they state "...is probably not robust", you might have a point.
They did not, this is a strawman argument. As clearly stated in the paper:
To compare our Standard5×5 reconstruction with modern climatology, we aligned the stack’s mean for the interval 510 to 1450 yr B.P. (where yr B.P. is years before 1950 CE) with the same interval’s mean of the global Climate Research Unit error-in-variables (CRU-EIV) composite temperature record, which is, in turn, referenced to the 1961–1990 CE instrumental mean.
They used 1000 years of overlapping data to align and reference to a paleotemperature reconstruction, which itself is aligned and referenced to overlapping data in the instrumental record. The last 150 years of the Marcott et al reconstruction during the instrumental period (the 'uptick') are interesting to consider, but have no impact on alignment. Your objection therefore has no grounds - I would strongly suggest reading the paper.
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dana1981 at 02:12 AM on 14 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Climate4All @13 - equilibrium climate sensitivity (which the Norwegian study is attempting to estimate) should be an essentially constant value. It shouldn't fall or increase by any significant amount just by adding in another decade's worth of data. If it does, as with the Norwegian study, then you know something is wrong with the model (i.e. it's too sensitive to short-term natural variability, and not accounting for some important factor[s]).
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Rob Honeycutt at 02:12 AM on 14 April 2013Real Skepticism About the New Marcott 'Hockey Stick'
Brandon... "Robust" in reference to the Marcott paper is not the same thing as "reliable." You're conflating the two terms. In fact, the modern warming data is extremely robust and reliable. So, the modern uptick, irrespective of Marcott, is something that should shock you out of your shorts!
As has been continually pointed, you're making arguments that support high climate sensitivity. So, you can't do that, then turn around again and claim that CS is low in another conversation.
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dana1981 at 02:10 AM on 14 April 2013Further Comments on The Economist's Take on Climate Sensitivity
archie @8 - this is not right:
"If the actual global mean temperature is exiting the 5-95% confidence level of the climate models - clearly there is something wrong with the models. "
First of all, I don't know what "exiting" means here. That assumes we know what will happen in the near future, which nobody does. Second, as pointed out by Tsumetai @9, we expect the data to fall outside the 5-95% confidence interval 10% of the time (below it 5% of the time).
In short, what's happening is that the model runs that simulate the lagest cooling effect on surface temps from natural variability are right. Then you have to compare the current observational data to the model runs and see if that makes sense. So what's happening in the real world? We're seeing a preponderance of La Niña events, an accelerated warming of the oceans, especially the deep oceans, low solar activity, etc. Basically what we would expect for a period of relatively flat surface temps - the heat is going elsewhere.
If there's anything 'wrong' with the models, it would be that they don't accurately reflect the magnitude of natural variability associated with the transfer of heat to the oceans, but since the observations are still within the range of model simulations, that's not an accurate statement.
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Brandon Shollenberger at 01:57 AM on 14 April 2013Real Skepticism About the New Marcott 'Hockey Stick'
chriskoz, I'm afraid the link you provided doesn't answer my question at all. The graph I'm referring to showed "Reconstructed Temperature" from Marcott et al cleanly flowing into "Projected Temperature." The part where the two join is at the end of the uptick you say is "not reliable."
I'm not asking about Marcott et al's work. I'm saying, given the uptick isn't reliable, why is John Cook praising a graph that relies upon the uptick? Erase the uptick from that graph, and there would be a large gap between the two lines. It wouldn't be a "powerful" graph anymore.
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Bob Lacatena at 01:30 AM on 14 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
I haven't read everything through (boy, you guys are long-winded), but I think to me the crux of the problem is "how much of AMO is inherent in AMO, and how much of AMO is a response to rising temperatures?"
To put it another way, ENSO events can be measured by using observations other than temperatures... sea surface height, barometric pressure differences, and even sea surface temperature distribution (i.e. is the east markedly different from the west). One can measure ENSO events (if one wishes) based on criteria which have nothing to do with absolute temperature changes, and so one is able to separate those two components.
By measuring AMO purely using temperatures, no matter what you do, you are unable to separate cause and effect. No argument is of any meaning unless and until you come up with a measure for AMO that is independent of temperature.
For example, KK Tung says in his post:
“The phenomenon likely involves thermohaline circulation variability in the Atlantic Ocean. As described in Dima and Lohmann [2007 ]; Semenov et al. [2010] , the negative feedbacks between the strength of the thermohaline circulation which brings warm sea-surface temperature (SST) to the North Atlantic, and the Arctic ice melt in response to the warm SST, which, because of reduced deep-water formation, then slows the strength of the thermohaline circulation after a delay of 20 years, together create the restoring force responsible for the oscillation."
Is it possible to describe an AMO index which is based entirely on some (non-temperature based) strength of the thermohaline circulation, and so to correlate the AMO itself with temperature changes rather than correlate temperature changes to temperature changes?
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KK Tung at 01:09 AM on 14 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
In answer to MA Roger at post 21: Now we are getting to the point! Please read our paper, Tung and Zhou. MLR is a mathematical procedure, not a physical one. In our paper it came towards the end after evidence---and there were many pieces----was presented that supports physically the need to remove the AMO to reveal the anthropogenic response. Then we said, "Now we are in a position" to do this quantitative analysis, which is the MLR. You would be right if all we did were to see an AMO-like bent in the data and we removed that. Someone else may disagree with the evidence that we presented and have a better argument for removing the Pacific Decadal Oscillation, for example. Then he/she would then do a MLR using the PDO as a regressor. This is the scientific process. Neither is circular. I would accept his/her MLR result over mine if I find his physical argument and observational evidence presented more compelling.
On your last point. Consider the case of a time series--let's use it as the observation----that contains a nonlinear "anthropogenic " signal and a white noise. And nothing else. Suppose the noise is large and I can't see the anthropogenic signal without doing the MLR analysis, but I do not know what to use for the anthropogenic regressor. So I have to guess. Now suppose I am lucky and chose a regressor that happens to be varying in time like that nonlinear signal. After doing the MLR the residual is found and I examine that carefully. I see that it is white noise. The conclusion I would then make is that the MLR is successful and the anthropogenic signal is nonlinear. If on the other hand I am unlucky and picked a linear function as my regressor, then the residual will not be just noise, but have some trends as well. Then I would conclude that my MLR is not successful and the anthropogenic signal should be nonlinear. Then for my second try I would pick a more nonlinear regressor, until the residual becomes just noise.
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Dumb Scientist at 00:46 AM on 14 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
You may call me a pedant if you wish but my reticence to just answering Yes-Yes was more due to philisophy than facts. ... In this case it was not clear to me if the question was about some hypothetical N.A.SST or the N.A.SST(1856-2013). [MA Rodger]
I wasn't planning to call you anything. In fact, I think your responses have been quite helpful. For the record, I was referring to the same N.A.SST(1856-2011) used in Tung and Zhou 2013, which do contain an AGW signal.
The residual compensates for the non linearity of the assumed nonlinear function. We pointed out in Zhou and Tung that it is the removal of the AMO that makes the most difference in getting the final result, a point that Dumb Scientist now correctly understood. It is not the form of the anthropogenic regressor or the amount of smoothing involved. I will talk about the issues related to the choice of the AMO indice in the second post next week. It is not a circular argument. [KK Tung]
I've repeatedly pointed out that the form of the anthropogenic regressor or adding the residual back is not the problem that concerns me. It's the fact that warming the globe also warms the N. Atlantic, and that net anthropogenic warming was faster after 1950.
I still think it's circular to subtract a linearly detrended AMO to determine AGW, and then find that the remaining AGW is linear. I've been consistent about this point for months, so it's not clear what I "now correctly understood" because that seems to imply a shift in my understanding that I'm not aware of.
I'm grateful to MA Rodger for answering my two yes/no questions. Dr. Tung, would you please answer them? It would only take a few seconds, and I'm very interested to see what your answers will be. Thank you for your time.
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archie lever at 00:45 AM on 14 April 2013Further Comments on The Economist's Take on Climate Sensitivity
(-moderation complaints snipped-).
Moderator Response:[DB] Models are off-topic on this thread, as previously noted. This applies to all parties, equally.
[TD] Archie, nearly everything on this topic is related to everything else, so it would be easy for every post and comment thread to end up being about everything. One of the strengths of this site is the collection of related ideas together. That makes them easy to find. It also reduces redundancy across threads. And often people discover that they change what they want to write after reading the original post and some of the other comments in the most immediately relevant thread.
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MA Rodger at 21:55 PM on 13 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
KK Tung @19.
I fear you are incorrect. Your answer @12 to the 'first point' did get through. However I disagree with that answer, as I do with what I understand of your renewed answer @19.
May I attempt to explain.Your two points from the post are
(1) The "finding" of a smooth or even linear net anthoropogenic forcing/warming profile (NAF/WP) is not wrong. I agree, as long as it is a "finding" supported by the data.
(2) The smooth NAF/WP is not the product of circular reasoning. This I pretty-much disagree with as I dispute that the smooth NAF/WP is a "finding." Rather I see it as a product of the analytical method not a product of the data, even using MRL. Because...
We start with a wibbly-wobbly temperature record. We agree that we can see the signature of ENSO and volcanic forcing and if we look the signature of solar forcing too. We are happy that these signatures can be extracted using MLR. This smooths out the wibbly-wobbly temperature record 1980-2011 and we are still happy. If those wibbly-wobbles had been truely part of the NAF/WP then NAF/WP would look more the product of a hyper-active child armed with graph paper and crayon than the product of climatological analysis.
In Tung&Zhou13 this MLR is carried out 1850-2011 which yields a profile not dissimilar to the temperature record for 1850-1980, a bendy profile, perhaps an oscillating profile. This we are agreed should contain all the NAF/WP.
Now the 1850-2011 profile (before and after extracting ENSO etc) is remarkably similar to the AMO profile. If you remove that AMO profile, because of that strong similarity, you will always get a smoothed result. If this smoothed result contains the full NAF/WP, the NAF/WP will arguably be likewise smoothed. This is not a "finding" of the analysis. It is the natural outcome of the process. It can be no other way given the choise of using AMO.
The "finding" is not a smooth NAF/WP but if it is legitmate to extract the AMO profile and leave the full NAF/WP behind, the corollary (no stronger) is that NAF/WP will be smooth.There are parts @19 which I struggle with, although this may be pre-empting the next post.
You say "The residual compensates for the non linearity of the assumed nonlinear function." Yet you describe in the post how you treat that Residual. You proclaim your analysis "successful" because "Except for s a minor negative trend in the last decade in the Residual, it is almost just noise." Surely reducing the Residuals to almost just noise and calling it "successful" leaves no room for any non-linear function, NAF/WP or otherwise. -
MA Rodger at 21:20 PM on 13 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
Dumb Scientist @18
You may call me a pedant if you wish but my reticence to just answering Yes-Yes was more due to philisophy than facts. A question about N.A.SST will involve, as well as our respective understandings of the nature of N.A.SST (which will not be identical, possibly radically so), but also our respective understandings of the nature of the question which also will not be identical, possibly radically so. In this case it was not clear to me if the question was about some hypothetical N.A.SST or the N.A.SST(1856-2013). -
archie lever at 21:08 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Doug Hutcheson and others
The Economist leader writer said that - not me.
He/she also said that:
"OVER the past 15 years air temperatures at the Earth’s surface have been flat while greenhouse-gas emissions have continued to soar. The world added roughly 100 billion tonnes of carbon to the atmosphere between 2000 and 2010. That is about a quarter of all the CO₂ put there by humanity since 1750. And yet, as James Hansen, the head of NASA’s Goddard Institute for Space Studies, observes, “the five-year mean global temperature has been flat for a decade.”
I assume that by global temperature the authors mean the composite sea and land temperature, but you would probebly have to confirm than with Jim hansen and Ed Hawkins.
(-off topic snipped-).
Moderator Response:[DB] Please take further discussion of models to the "models are unreliable" thread. Models are off-topic on this thread.
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chriskoz at 20:47 PM on 13 April 2013Real Skepticism About the New Marcott 'Hockey Stick'
Tom Curtis,
You turned a lot of attention to 8.2ky event as the proof that Marcott 2013 reconstruction could not catch signifficant departures from Holocene optimum, contradicting Tamino's conclusions.
But have you considered the oposite: can 8.2ky be taken as a proof that Marcott 2013 is "incensitive" to the dT signals such as AGW? I tend to agree with chris who says that it cannot. He's shown @51 that there is no evidence 8.2ky was a global event, and the NH cooling due to AMOC overturning, was globaly diluted.
So, we may turn the topic around and ask: since Marcott 2013 did not detect 8.2ky event, can we conclude the event wasn't global? I.e. it resulted in circulation overturning only, therefore influenced some proxies only but overall, it did not create any forcing that would influence the global energy budget, like CO2 does? I'm postulating that it was only local cooling, because I don't know any mechanism by which the global energy imbalance could have been created to last over a century. To my liking it was more like a gigantic ENSO disturbance. To claim otherwise (that 8.2ky created signifficant negative global forcing comparable in scale with AGW, as you seem yto imply) you have to provide the physical mechanism for that.
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chriskoz at 20:12 PM on 13 April 2013Real Skepticism About the New Marcott 'Hockey Stick'
Brandon@53
Tamino answers your question comprehensively here.
Essentialy, the "uptick" in Mercott 2013 reconstruction is not reliable because fewer of their data covers the last centuary.
What is reliable, is the almost perfect alignment of last 2000y with other proven reconstructions of that period, e.g. Mann 2008, and consequently, with temperature record such as HadCRUT4. That's why the "blade" on figure 1 is marked with red (reliable HadCRUT4 data). So, Marcott 2013 uptick is not robust, but the rest of it is robust and the alignment with the other reconstructions is also robust and that's all we need to know to have confidence in this graph.
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Jim Hunt at 20:02 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Fresh from accusations of being a "SkepticalScience affiliate" by denialistas amongst The Economist commenters, I finally arrive here courtesy of a comment on my own blog. Would anyone here like to play "Spot the difference!" and then "What if?"?
Re #12 and #18, here's the latest news from the sharp end over here in soggy South West England, just down the road from the Hadley Centre:
http://econnexus.org/met-office-admit-our-climate-is-being-disrupted-by-the-warming-of-the-arctic/
To summarise, it seems Julia Slingo disagrees with The Economist leader writer. However it's still not clear what she intends to do about it. -
John Russell at 19:32 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Ray at #12 Re; apparently conflicting comments about weather from the UK Met Office.
One of the problems is that although we can know with high levels of certainty that the world is warming, and by how much per decade, it's very difficult to predict the effects of that warming on the resultant weather in a particular country -- particularly one as prone to variable weather as the UK. That's because we've never seen rapid rises in global temperature before during any periods when humanity has been in a position to record the results.
The truth is that a few years back the Met Office were more confident as to how global warming would manifest itself on UK weather than they are today. That's why, for instance, they dropped the long-range weather forecast. We've entered unchartered territory now and the changing pattern of the jet stream that has become apparent over the last few years is one example of the sort of change we're seeing.
As climate scientists have started to realise how much they don't know about the way global warming will manifest itself on weather, you've seen the Met Office change from statements like "expect warmer winters with less snow" (the simplistic guess) to the uncertainty revealed by the statement by Julia Slingo who said about the current cold weather the other day, "if this is how how climate change could manifest itself, then we need to understand that as a matter of urgency".
I think that instead of looking at this a weakness you need to put it in the context of the huge scientific research effort to understand what global warming will mean to weather.
If you'll permit me to use an analogy. It's like the uncertainty of a hot air balloon flight. If we know the direction of the wind, the amount of weight on board and how much gas it carries, we can predict with a reasonable level of certainty in roughly what area it will land. The more information we have and the more experienced the pilot, the surer we can be of predicting the landing site. But there are always variables and at the moment things are happening that create uncertainties we have not experienced before. This is making predictions more difficult; but everyone is working very hard to understand those uncertainties. Don't lose sight of the fact that however much uncertainty there is there is, one thing is not in question: the ballon will come down somewhere.
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Brandon Shollenberger at 18:49 PM on 13 April 2013Real Skepticism About the New Marcott 'Hockey Stick'
John Cook recently "tweeted" this:
If we don’t change our direction, we’ll end up where we’re headed - powerful graphs by Jonathan Koomey
Sharing a link to this piece which shows a graph of projected temperatures grafted to Marcott et al's reconstruction. The visual impact of this graph depends largely upon the uptick of Marcott et al's reconstruction flowing into the projected temperatures. However, this post says:
Much of the manufactured controversy about the Marcott paper is in regards to the 'blade' or 'uptick' – the rapid warming at the end of the graph over the past century. While their reconstruction does identify an approximately 0.6°C warming between 1890 and 1950, the authors note in the paper that this result is probably not "robust."
Without the uptick in Marcott et al., there would be little (if anything) to create a visual connection between the "reconstructed Temperature" and "Projected Temperature" of the graph John Cook says is "powerful." You guys say that uptick is "probably not 'robust.'"
How can a "powerful" graph rely upon a result that is "probably not 'robust'"?
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scaddenp at 18:04 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Climate4All - climate models have no skill at decadal prediction. They have never pretended to. That is pretty much the point made - and the problem with the methods that dont take account of high surface temperature variability.
First I have heard that model predict weakening of it. Got a source for that?
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Climate4All at 15:35 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
@14 scaddenp
The contention that I address only are those that Dana and Micheal suggest.
Not the OHC values. Not El Nino and its relationship to to surface temperatures. Not models being able to predict ENSO patterns, though I do believe that some models adjust for a general weakening of it.
Dana is willing to say they got it wrong, but by how much and at what certainty should global temperatures reside. he didnt say they got it completely wrong.
Has Mann done a similar study for the last decade yet?
I just wanted clarification.
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Alun at 15:29 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
I think we are encountering a problem I find frequently in my work with financial modelling. These models are less complex than the climate models, but their use generates similar arguments about interpretation of actual results versus those expected from the models. The simple problem is that the vast bulk of consumers of model outputs (climate and financial) have a very limited appreciation of stochastic type outcomes.
One can talk all one likes about 90% CIs and that 5% of actual outcomes will fall above and 5% below, but the users still get twitchy when the actuals are not tracking near the median line. The reaction in my experience is ALWAYS that there must be something wrong with the model and if the 90% CI line is broken the general view will be that the model is definitely and clearly wrong and must be fixed.
This inherent difficulty of understanding is coupled with the fact that the majority of the presentation of climate warming to date has demonstrated the effects using surface temperatures. Surface termperatures, after all, are what people, plants and animals actually experience.
I started studying climate impacts and models back in the 1970's and have no doubts about the veracity of the current science or its predictions (naturally within the normal scientific error bars). The current results are falling close to the 90%CI boundary because of the correlations of effects that hold surface temperatures lower over recent years versus the correlation of effects that held them higher 15 years ago. The actuals have not broken the boundary in the timeframe on the chart above which covers nearly 100 years and we would have expected a few by now so the models are clearly doing a very good job and I, for one, am quite comfortable with the estimated sensitivity. It looks absolutely spot on (within error bars).
But expect serious confusion and complaint against the models if the actuals actually do breach the 90%CI. The problem of course is much much wider than surface temperatures so we better start educating as even some of the comments on this forum demonstrate.
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scaddenp at 15:19 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Climate4All - please tell me how you can get OHC values at current levels with a sensitivity of 1.5.
For those of you here that think current surface temperature trends suggest climate models are wrong, can I ask which of these you believe?
1/ The next El Nino of greater than 1.8 wont break surface temperature records.
2/Models should be able predict the ENSO patterns
3/ Eli Nino's will be rare in the future and La Nina/Neutral conditions will surface temperatures as they are.
Ray, Climate4All, Archie?
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KK Tung at 15:12 PM on 13 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
In answer to MA Roger at post 14: I am glad I answered your second point. Somehow I still failed to yet my answer through on you're first point. While one of the two methods in Tung and Zhou used smoothing, the second method, the MLR method, does not, and it is this second method that I discussed in the present post. Let me try another way to presenting this point: Give me any nonlinear function that you prefer (within reason of course, and it should have an increasing long term trend), I go through the MLR. I would still get a fairly linear response as long as I add back the residual. The residual compensates for the non linearity of the assumed nonlinear function. We pointed out in Zhou and Tung that it is the removal of the AMO that makes the most difference in getting the final result, a point that Dumb Scientist now correctly understood. It is not the form of the anthropogenic regressor or the amount of smoothing involved. I will talk about the issues related to the choice of the AMO indice in the second post next week. It is not a circular argument.
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Climate4All at 14:38 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
If climate sensitivity hasn't fallen by a factor of 2, what would some of you suggest as a respectable amount of 'fallen off', and what percentage of certainty would that lay at?
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Ray at 13:55 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Interestingly the UK Met office has just released a statement on cold winters that is completely at odds with its previous comments on the effects of global wrming on the UK climate. Sometimes, like Archie Lever I find it difficult to determine what the real situation is.
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DSL at 13:22 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
And Archie, global ice mass loss has accelerated during the Had4 surface temp "hiatus." Remember: the climate-scale global (plus poles) surface trend is .169C per decade, just a hair short of the expected rate of warming. Use the eyecrometer and end up standing in the foolish line.
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Doug Hutcheson at 12:13 PM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Archie said
"The mismatch between rising greenhouse-gas emissions and not-rising temperatures is among the biggest puzzles in climate science just now."
Er ... not rising temperatures? Are you referring to global temperatures, or land surface temperatures? Globally, the oceans have been warming at the expected rate. Land surface temperatures have been constrained by such influences as ENSO and have behaved as expected, given the forcings. Which part of this is a big puzzle?
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Tsumetai at 11:57 AM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Archie, we generally expect about 10% of the data to fall outside the 5-95% CI. That's kind of what a 90% CI means.
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archie lever at 11:24 AM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
dana 1981
This quote is the central issue posed by the Economist article.
"Temperatures fluctuate over short periods, but this lack of new warming is a surprise. Ed Hawkins, of the University of Reading, in Britain, points out that surface temperatures since 2005 are already at the low end of the range of projections derived from 20 climate models (see chart 1). If they remain flat, they will fall outside the models’ range within a few years.
The mismatch between rising greenhouse-gas emissions and not-rising temperatures is among the biggest puzzles in climate science just now. It does not mean global warming is a delusion. Flat though they are, temperatures in the first decade of the 21st century remain almost 1°C above their level in the first decade of the 20th. But the puzzle does need explaining.
The mismatch might mean that—for some unexplained reason—there has been a temporary lag between more carbon dioxide and higher temperatures in 2000-10. Or it might be that the 1990s, when temperatures were rising fast, was the anomalous period. Or, as an increasing body of research is suggesting, it may be that the climate is responding to higher concentrations of carbon dioxide in ways that had not been properly understood before. This possibility, if true, could have profound significance both for climate science and for environmental and social policy."
If the actual global mean temperature is exiting the 5-95% confidence level of the climate models - clearly there is something wrong with the models. This has not been effectively addressed in any of the comments seen here of the Discovery News article or links.
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Dumb Scientist at 10:01 AM on 13 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
But if you add that N.Atlantic SST does contain an AW signal, then the answer to Q1 will have to be yes. [MA Rodger]
How could N. Atlantic SST not contain an AGW signal?
But where do such answers lead? They say 'Yes, they will remove some of the AW signal' and then beg the question 'How much is "some"?'
Exactly. Such answers would lead to the discussion I wanted to see in Tung and Zhou 2013: namely 'How much is "some"?' I'm astonished that they didn't even address the possibility that they're subtracting signal (unless I missed something?).
That surely leads off towards the nature of AMO which is the subject of the next part of these posts.
As I mentioned to Lee and ptbrown13 in the comments on my article, I have no problem with the idea that AMO variability has parts that are strictly internal and parts which alter the radiative imbalance of the climate. While a discussion of the nature of AMO could be informative, I'm skeptical that the nature of AMO can be elucidated by subtracting AGW after 1950.
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MA Rodger at 09:49 AM on 13 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
Dumb Scientist @16.
The two questions you pose could be answered in a number of contexts with differing assumptions to yield different answers.
But if you add that N.Atlantic SST does contain an AW signal, then the answer to Q1 will have to be yes.
And if you add that the AW signal is not linear, then AMO derived from N.A. SST through linear detrending will still contain an AW signal and the answer to Q2 will have to be yes.
But where do such answers lead? They say 'Yes, they will remove some of the AW signal' and then beg the question 'How much is "some"?' That surely leads off towards the nature of AMO which is the subject of the next part of these posts.
My apologies if the logic I present @ 14 has proved unclear. I shall attempt to re-state it.
If the AW forcing profile is smooth, so too will the AW signal within the temperature record. And visa versa. Thus if an analysis has by its nature the effect of smoothing the AW signal, by its nature it will produce a smooth AW forcing profile. Therefore such analysis cannot in itself be used to show how smooth is AW forcing.
This is perhaps why I spy in the post discontent with bendy forcing profiles - bendy profiles are inconsistent with a significant AMO signal being superimposed on the AW signal.
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Dumb Scientist at 07:10 AM on 13 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
... such a profile here is the implicit result of your analysis because you began by smoothing the temperature series. It is thus "assumed" and not "found". ... [MA Rodger]
I don't understand this point. I thought the issue was simpler, but I might be failing to comprehend in addition to my obvious failure to communicate. Perhaps it would help if we all answered these yes/no questions:
Question 1
Would regressing global surface temperatures against N. Atlantic SST without detrending the SST remove some anthropogenic warming from global surface temperatures?
Yes or no?
Question 2
Now suppose we regress global surface temperatures against N. Atlantic SST after linearly detrending the SST. In other words, we regress against the standard AMO index as Tung and Zhou 2013 did.
Just imagine that anthropogenic forcings increased faster after 1950. In that case, would regressing global surface temperatures against the AMO remove some anthropogenic warming from global surface temperatures after 1950?
Yes or no?
I'll start: my answers are yes and yes. In fact, I think answering yes to question 1 also implies a yes to question 2, but I'm willing to be educated.
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william5331 at 05:54 AM on 13 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
It should be interesting when the Chinese people demand that the Chinese government stops sending aerosols into the atmosphere. A similar scenario unfolded when America started electrostatically precipitating particulate matter from her smoke stacks and began to scrub out SO2.
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MA Rodger at 05:41 AM on 13 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
KK Tung @12.
Thank you for clearing up my final enquiry point.
It appears by your reply to my first point that we may be talking at cross-purposes. I will attempt to clarify the point.
My concern here is that most constructions of net forcing in the literature (and as linked in the post) show a strong increase in the net forcing from the 1970s on. Conversely, your paper is proposing a smoother (less bent) increase (described in Tung&Zhou13 as "converging to" a linear trend which to me is highly suggestive of a linear forcing). Neither in this post nor Tung&Zhou13 is the smooth/bent forcing issue adequately addressed.
The two methods presented in Tung&Zhou13, (the 50-y to 90-y wavelet band subtraction & the MLR with AMO index included) expressly attempt to produce a smoother (less bendy) temperature record. Thus when non-linear forcings are fed in (as described in the above post), it is obvious that the profile found "closest to the final adjusted data turns out to the QCO2(t) function", a very smooth forcing profile.
"Finding" a smooth forcing profile is not wrong (your first take-away point). However, such a profile here is the implicit result of your analysis because you began by smoothing the temperature series. It is thus "assumed" and not "found".
I wouldn't go so far to say that this makes for a circular argument. Yet it does require more support for use of a smooth forcing profile as it is "assumed" and to my limited knowledge forcing profiles for the century are usually rather bent. (@11 I also noted a seeming implied view within your post that the "bend" was being unreasonably exaggerated. This is still worthy of comment.) -
Bob Loblaw at 05:07 AM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
John R:
Kind of like the accident victim that is bleeding internally, with no visible signs of bruising or blood loss (yet), who is about to collapse and die?
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John Russell at 04:39 AM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Just a little point. I've heard the response from some of those in climate denial that if the heat is going into the oceans then that's a good thing; as if it's lost forever. I think it's important to reiterate what seems obvious to anyone who understands the basics of climate change: heat into the oceans is heat into the overall climate system and it will eventually come back to bite us.
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jdixon1980 at 04:07 AM on 13 April 2013The History of Climate Science
Coincidentally, his team happened to solve the mystery while I working on the project: Marble varieties with smooth ("granoblastic") grain boundaries would crack due to cycling thermal expansion and contraction, whereas marble varieties with rougher grain boundaries ("xenoblastic") tended to resist grains shifting around and thus didn't crack as easily.
Of course these ramblings have nothing to do with climate history and I wouldn't be offended if they were deleted as off-topic.
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jdixon1980 at 03:54 AM on 13 April 2013The History of Climate Science
Reminds me of back in engineering school when I was doing a project for my failure analysis class, and I was corresponding with a guy via email who was the head of a multinational European research project studying marble cladding on buildings, and in particular why some of the cladding was cracking and falling apart (due to the marble "bending" from non-uniform thermal expansion and contraction through its thickness), and some not. The name of the Danish gentleman in question was, I kid you not, Bent. Bent Grelk. And he insisted that I was the first person to comment on how appropriate that was! Very nice guy.
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jdixon1980 at 03:49 AM on 13 April 2013The History of Climate Science
I'm sure you've heard this before, but I love the name "Mason" for a guy who studies rocks.
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Dumb Scientist at 03:06 AM on 13 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
There was no assumption of net forcing being linear in our work. That was a misunderstanding on the part of Dumb Scientist.
My previous comment explained that you are assuming the net anthropogenic forcing is linear, by subtracting the linearly detrended AMO.
In fact, Figure 2 and Figure 3 are two examples using nonlinear net forcing indices. A third example was given in the paper by Zhou and Tung (2013) in Journal of Atmospheric Sciences. It discussed the case of using the nonlinear difference of the two anthropogenic forcing curves displayed in Figure 2a. In all three cases, the deduced anthropogenic response appears rather linear for the past 100 years, as long as one remembers to add back the Residual before measuring the trend.
Again, as I've already pointed out, that's just because you swept the faster warming since 1950 into the AMO(t) function.
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KK Tung at 02:02 AM on 13 April 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
Reply to MA Roger:
While you are correct to say (as you do) that it is not wrong if net forcing is found to be linear over the period, this is not the same as basing your study on an assumption of net forcing being linear over the period.
There was no assumption of net forcing being linear in our work. That was a misunderstanding on the part of Dumb Scientist. In fact, Figure 2 and Figure 3 are two examples using nonlinear net forcing indices. A third example was given in the paper by Zhou and Tung (2013) in Journal of Atmospheric Sciences. It discussed the case of using the nonlinear difference of the two anthropogenic forcing curves displayed in Figure 2a. In all three cases, the deduced anthropogenic response appears rather linear for the past 100 years, as long as one remembers to add back the Residual before measuring the trend.
Your comment that warming follows CO2 with such little time lag being rather tricky and "will not be discussed here." I like 'tricky'. Is it to be discussed in a later post?
It is tricky because it could easily lead to misunderstanding in such a public forum. If CO2 were the only anthropogenic forcing, the response in Figure 3 would have implied that the climate sensitivity is low. However, CO2 is not the only greenhouse gas, and greenhouse gas radiative forcing is not the only anthropogenic forcing. There are some negative anthropogenic forcings, such as tropospheric sulfate aerosols, that subtract from the greenhouse gas forcing. At least that is my current understanding. My previous work, Tung et al (2008), Geophysical Res. Lett., using the observed transient response to the 11 year solar cycle, gives a climate sensitivity estimate that is at the high end of the IPCC range.
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chris at 02:02 AM on 13 April 2013Real Skepticism About the New Marcott 'Hockey Stick'
Glen (@43) re:
And as an aside, how does a spike that intense and that short occur in the NA? If there was a significant collapse of the MOC, would it recover that quickly?
The evidence is pretty strong that it arises from a dramatic increase in fresh water from ice melt (or meltwater release from lake Agassiz in the case of the 8.2 kYr event) that dilutes the cold salt rich waters in the N Atlantic and disrupts the thermohaline circulation. This can seemingly occur and recover very quickly indeed. Related events in glacial periods (Dansgaard–Oeschger events) typically show very rapid warming in Greenland (over a few decades) followed by a slower decline (the Wikipedia page seems pretty decent on this!). D-O events are marked by a N-hemisphere S-hemisphere “see-saw” where N-hemisphere (Greenland) warming matches S-hemisphere (Antarctic) cooling and vice versa. It’s not clear whether the 8.2 kYr event matches the D-O events in terms of the bipolar “seesaw”. However the proxy evidence is consistent with more localised cooling in the high N-latitudes and little cooling (and perhaps some warming overall though this remains to be determined) in the S hemisphere [see my posts above and Morrill et al (2013) that Tom referred to which can be found here]:
www.clim-past.net/9/423/2013/cp-9-423-2013.html
Interestingly, the AMOC provides one of the few possibilities for fast “switch-like” processes in the climate system. On the question whether other large temperature excursions might have occurred in the past (e.g. the Holocene!) it's worth noticing that the other natural event expected to lead to rapid temperature responses is an intense and prolonged (e.g a decade or two) series of strong volcanic eruptions. Strong fast global scale temperature increases are less likely (requiring catastrophic release of CO2 or methane or a dramatic change in solar output). All of these potential catastrophic events would leave their own particular signatures in the paleorecord, especially in ice cores….
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chris at 01:35 AM on 13 April 2013Real Skepticism About the New Marcott 'Hockey Stick'
Tom (@44), one can’t invent data where it doesn’t exist. The Kilimanjaro paper you link simply doesn’t show evidence for a local cold spike. The delta 18O data (e.g. their Fig 4) shows high (warm) values for the period from about 10.8 kYr through about 6.8 kYr (when there is a very significant and abrupt “cooling” transition). All the apparent temperature spikes in the period are “warming” spikes.
The Morrill et al paper you mention (thanks for that) gives a pretty good summary of existing knowledge on proxies covering the 8.2 kYr event. These indicate large cooling in Greenland (delta 18O of -0.08 - -1.2 %o), cooling in the N. Atlantic and Europe of around 1 oC (del 18O – 0.4 - -0.8%o), with positive del 18O (+ 0.4 - +0.8 %o) in the N. hemisphere tropics. The more limited S. hemisphere proxies support negligible cooling (or at least a mix of either no change or some regional warming or cooling).
That’s simply what the data shows at this point. It seems reasonable to conclude that there was a very significant cooling in the high N. latitudes with an overall cooling in the N. Atlantic and Europe of around 1 oC, and negligible cooling (or warming) at lower latitudes and in the S. hemisphere. The pattern of temperature variation and the speed of the event is consistent with the meltwater hypothesis and its effect on the AMOC.
So there simply isn’t any evidence for a widespread global cooling that matches the magnitude of contemporary global scale warming. The proxy data would certainly support a rapid high N hemisphere cooling that was “diluted” globally so that the 1oC identified in the proxies in these regions is reduced when considered on a N. hemisphere basis and then halved by the lack of S. hemisphere cooling. The proxies are consistent with a global scale cooling perhaps somewhere between 0-0.5 oC. And this cooling (and warming) occurred faster than contemporary global scale warming. As far as the evidence goes, the 8.2 kYr event isn’t a particularly good test of the Tamino analysis.
One of the very useful things science-wise about the Marcott paper is that it provides a focus for addressing these issues (Holocene proxies and their spatial distribution). But it’s when the analyses enter the scientific literature that some incremental progress is made. Tamino’s analysis is simply the result of a couple of day’s consideration. It would be good if individuals with interest and expertise in this particular issue put their heads together and wrote a paper addressing the possibilities that particular scenarios could or could not be tested with existing proxies. Useful tests would involve inspecting the proxies themselves or addressing a global scale temperature reconstruction around the 8.2 kYr event using the proxies that cover this (e.g. in Morrill et al 2013). I expect that some of this is underway…
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Tom Dayton at 01:24 AM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
archie lever, the only way I can make sense of your contention that the Discovery News rebuttal story is "unimpressive in detail" and "would have much less authority than the Economist story," is to assume that you failed to click on the hyperlinks in the Discovery News story.
Print media must list their references as immediately-viewable text. That is distracting, so footnotes and endnotes were invented to reduce interference with reading the primary material while still providing easy access to the supplementary details. But electronic media often eliminate the distraction of the footnote and endnote numbers embedded in the primary text, by making key words and phrases links to that supplementary material.
In both that Discovery News story and the ABC Environment story, please click the embedded links to get to the details that you thought were not provided.
Here on the Skeptical Science site, most "Argument" rebuttals have multiple levels of detail contained in multiple tabbed panes: Basic, Intermediate, Advanced. The Argument Rebuttals are the ones in the "Most Used Climate Myths" list at the top left of every page, plus a much fuller list you can access by clicking the "View All Arguments" link there or the "Arguments" link at the left of the blue horizontal bar at the top of every page. (The Argument Rebuttals differ from the regular "Posts" such as the one you are reading now.)
I suggest you get a quick orientation to the science of climate change, by visiting the Home Page of this Skeptical Science site, and clicking the three big buttons at the top of that page: "Newcomers, Start Here," "History of Climate Science," and "The Big Picture." Remember that in all those pages, the details are accessible simply by clicking the hyperlinked in-line text. To get an accurate impression of how much detail really does exist, then visit The New Abridged Skeptical Science Quick Reference Guide.
You can keep an eye on comments across all the threads by monitoring the Comments page, which you can access by clicking the Comments link in the middle of the horizontal blue bar at the top of every page.
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dana1981 at 01:16 AM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
archie @2 - we did not dismiss The Economist article "as a sort of denialist rant." We simply pointed out all the important research they did not include. Failing to include that research skewed the article towards a conclusion that is not well supported when all evidence is considered.
Your final paragraph misses the point. They make a good case that the extent of warming has probably been overstated? That's like saying climate contrarians make a good case that the surface temperature record is biased. As long as you only consider the evidence and research that supports your conclusion, it's easy to "make a good case". Until you account for the contradictory evidence. That was the point of our article.
The Economist is a good magazine and usually writes good climate pieces. This one was not very good. I'm not accusing them of being deniers, just pointing out that they made mistakes in this article, which led to a wrong conclusion.
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Bob Lacatena at 01:14 AM on 13 April 2013Models are unreliable
bouke,
I'll give you a half-apology, if in fact your question was innocent and genuine, but I've reread it several times, and it strikes me as part concern-troll, part denier-mythology. You make a lot of broad-brush statements, dripping with doubt, like "I never hear a scientist say..." and "Why is that?" and "The issue I have is that I see scientists..." — as if your role as armchair-jurist is to judge how well scientists are doing their jobs, and your neighbor told you they aren't.
You read one paper, and then drew a bunch of unjustified conclusions. I suspect that much of your interpretation is tainted by the uneducated comments you may have seen on other sites, and if that is the case, I'd suggest that you follow up such comments with solid research to confirm their validity.
In particular I would suggest that you follow the following Google Scholar search and see what you can infer from the actual work that is being done by scientists, rather than hobby-site comments and a single paper:
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Tristan at 01:00 AM on 13 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Archie, if the article were well-researched, you'd expect the message to be in line with 'cutting edge' climate science.
It isn't.
Therefore, either it was poor research, if you give the economist the benefit of the doubt, or wilful ignorance (denialism).
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Paul R Price at 00:02 AM on 13 April 2013Real Skepticism About the New Marcott 'Hockey Stick'
@49 chriskoz
Many thanks for the excellent advice. I had not yet taken the time to explore how to format the graphic for the net so thanks for saving me the time.
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archie lever at 23:54 PM on 12 April 2013Further Comments on The Economist's Take on Climate Sensitivity
Paul Magnus and Authors
As a long time subscriber to the Economist, I have found their information on a range of subjects to be well researched and first class. It is a 'newspaper' widely read amongst decision makers all over the world. Their science and technology section is written for the layman but well detailed and cutting edge in many fields.
I would not dismiss their subject article on climate change as a sort of denialist rant.
The Discovery News rebuttal story you quote above is unimpressive in detail and would have much less authority than the Economist story.
The Economist is not denying a contribution to global warming by CO2 means but the authors make a good case that the extent of warming has probably been overstated, and the uncertainties probably understated.
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