I can’t help wondering if the following paragraph in the SPM will get revised:
The observed reduction in warming trend over the period 1998–2012 as compared to the period 1951–2012, is due in roughly equal measure to a cooling contribution from internal variability and a reduced trend in radiative forcing (medium confidence). The reduced trend in radiative forcing is primarily due to volcanic eruptions and the downward phase of the current solar cycle. However, there low confidence in quantifying the role of changes in radiative forcing in causing this reduced warming trend. {Box 9.2; 10.3.1; Box 10.2}
- 1. That the trend from 1998-2012 is less than the trend from 1951-2012.
- 2. That net radiative forcings due to volcanic eruptions average over 1998-2012 is lower than that averaged over 1951-2012
- 3. That net solar forcing average over 1998-2012 is lower than that averaged over 1951-2012 and
- 5. Observation (1) is in part due to the net effect of (2) and (3) (possibly with other things happening.
The difficulty is that 2 appears to be untrue and while 3 is true, the effect of 3 relative to 2 would be too small to matter.
Net radiative forcing due to volcanic eruptions
We can find information to estimate the net radiative forcing due to volcanic aerosols at GISS where they have posted data on optical thickness Ï„ from the SATO index. A conversion factor is required to convert this into forcing GISS suggests
The relation between the optical thickness and the forcings are roughly (See “Efficacy …” below):
instantaneous forcing Fi (W/m2) = -27 Ï„
adjusted forcing Fa (W/m2) = -25 Ï„
SST-fixed forcing Fs (W/m2) = -26 Ï„
effective forcing Fe (W/m2) = -23 Ï„
The choice of conversion factor is not important to my comment; I selected -23 Ï„. Using this, I plotted the time series for forcing due to aerosols (black). Along with the averages over the years 1951-2012 inclusive (purple) and 1998-2012 inclusive (blue).
In this curve, volcanic aerosols cool: that is 0 corresponds to no volcanic aerosols, and the absolute forcing due to this factor is 0. In constrast when volcanoes erupt, aerosols increase and cool . Notice that while a forcing of zero could hypothetically be achieved if vulcanism died on our planent, a forcing of 0 is never achieved during the period shown. Instead, volcanoes periodically erupt, and the aerosols clear. Generally, another volcanic eruptoin will occur before the previous one clears. The result is that during most periods, volcanic aerosols are generally providing some cooling, and the average for 1951-2012 is shown in purple. It happens the period from 1998-2012 represents a period when the skys were relatively clear of volcanic aerosols; relative to the full period shown, this sub period experiences 0.28W/m2 more radiative forcing. This means that if the temperature trend during the two period were strongly influenced by the average net forcing during their respective periods, we would expect the temperature trend from 1998-2012 to be larger than the temperature trend from 1951-2012.
This is the opposite of what the text in the SPM suggests.
Net solar forcing
Comparing the average solar forcing during over the two time periods in question is a bit more difficult. To do this, I first obtained a record suggested for use by AOGCMS submitting runs to the CMIP5:
https://ftp.geomar.de/users/kmatthes/CMIP5/TSI_WLS_mon_1882_2008.txt. Data ends in 2008, so I then obtained data from this file ftp://ftp.pmodwrc.ch/pub/data/irradiance/composite/DataPlots/ext_composite_d41_62_1302.dat which I think is sufficient for the purposes of this blog post. Note however that these values are perpendicular to the plane of the earth while those for volcanoes are for a unit area on the curved surface of the earth. So, the solar values must be divided by a factor of 4 when comparing to the the effect of volcanic aerosols.
The figure below shows from the first source in black; the second in blue:
Note there is some discrepancy near 2008, but the two records are largely similar in the overlap regions.
For purposes of this post, I averaged the two records where they overlapped, and then computed the temporal averages over 1951-2012 and 1998-2012:
Notice here, the average of solar effect over the later shorter time period would be cooling. Specifically, on average the later periods experienced 0.07 W/m^2 less warming than the longer period in which it is embedded.
Sum of Net Volcanic and Solar forcings
Of course you can add, but I think it’s worth creating the graph with the volcanic aerosols and solar radiation added together (scaling solar by a factor of 4):
In this graph, the forcings averaged over the later periods (blue) exceed those during the longer period in which it is embedded by 0.26 W/m^2. That is: if we use the average over these periods to develop a notion about whether solar and volcanic aerosols exerted a net warming or cooling effect on the climate, we should conclude that the net effect should have been warming. If so, they should have enhanced the trend during “the pause” rather than reduced it.
Closing
I suspect this SPM, particularly the portions about “the pause” are being slapped together in haste. And I even thing I know what they might wish to say (based on leaked Chapter 9). However, I’m not convinced by the argument I think they intend to make. So I will wait to criticize it until such time as they make it.
Meanwhile: If they do stick with the current wording, it is a horrible non-sensical jumble. I think the AR5 is supposed to be published any day now! Wait and see.
Update: SteveF pointed out I forgot to divide the solar forcing which acts on the projected area of the earth (~ π R^2) by 4 to put it on the same area basis as the volcanic aerosols which act over the full surface area (~ 4 π R^2). I’ve corrected the error, which lucky for me only makes my point stronger.
When I read the released summary, it was clear the AR5’s authors were struggling to find an explanation as to why The Pause is occurring, while at the same time not leaving any kind of impression with the reader that the pause might be permanent just for the very fact of its existence.
If they are having this kind of struggle in finding a credible way of explaining the pause in the summary document, what kind of struggle will they be having in explaining their latest predictive plots — whatever those will eventually look like?
Lucia,
I think your solar forcing estimate is too high by a factor of 5.7. The ~1366 watts/M^2 value is perpendicular to the suns rays above the atmosphere. The average at the earth’s surface is reduced by a factor of 0.7 (Earth’s albedo) then by a factor of 4 (surface area of a sphere versus surface area of a circle). Net: 4/0.7 = 5.71 times too high. The solar forcing variation is quite small (~0.2 watt/M^2 peak to valley) compared to the volcanic forcing.
OH.. shoot. I did forget these are on a flat surface perpendicular to sun. That only makes matters worse for IPCC of course… but embarrasing mistake. I’ll fix that.
Fixed.
Oh, it occurs to me I should add that CMIP5 guidance told modelers to use the solar cycle as measured up through 2008 and afterwards repeat the 23rd cycle. So, numerically, there is very little excuse for pinning any disagreement on the solar cycle. It’s true that the solar measurement from 199(x) won’t match 2009 perfectly and so on. But it it’s not as if the minimum value was used going forward. (And if they and, that would not explain models warming too fast. You’d expect them to warm too slow.)
As for volcanoes: I think there was no guidance for after 2008. I think there might be no guidance for after 2000. I don’t know if modelers left cooling by volcanic aerosols at the near record low values from 2008, the quite low values from 2008, or whether they picked some other slightly “hazy” value.
If they left them at near record lows, we can expect that:
1) current projections will be stated without mentioning that the projections assume volcanic forcings at their maximum conceivable values which means that we should anticipate they will tend to over predict warming and
2) When warming does not keep up with projects, people will insist on extremely detailed “corrections” to account for that before anyone is allows to note that the projections are, in fact, too warm. Anyone pointing out the projections are too warm will be scolded and told you can’t say that because … well… you haven’t corrected form volcanic aerosols.
3) If a huge volcanoe goes off, of course that will be “unexpected”. 🙂
3 is actually true. It’s impossible to predict when those are going to go off. But these small, nearly unnoticed at the time eruptions now supposedly ‘causing’ the pause happen all the time. It’s a bit odd not to keep the model-sky permanently slightly hazy!
Lucia,
The ~0.7 factor for albedo also applies, so the solar influence is even smaller… making the IPCC claim even less tenable. Final nit-picky point: the solar cycle can be set to zero for the average of the cycle, so that peaks are positive and valles are negative…. this is (I think) a little more fair way to present the solar influence… near zero on average.
Steve
Sure. It could be presented as an anomaly. I did use anomalies when I combined the two forcings, but showed individual ones using the their absolute values.
One problem with baselining the solar is that it would make it difficult to show the to different records do more or less overlap. I needed to look at that just incase there was some issue there.
Beta blocker writes “If they are having this kind of struggle in finding a credible way of explaining the pause in the summary document, what kind of struggle will they be having in explaining their latest predictive plots — whatever those will eventually look like?”
My guess is that AR5 model tuning will sacrifice some historical fit to get a better recent fit by playing with ocean heat uptake. Then we’ll start to see papers that rewrite the OHC history to match.
/cynacism
Tim, you very likely have made a valid prediction:
http://www.realclimate.org/index.php/archives/2013/09/what-ocean-heating-reveals-about-global-warming/
Ha! Right on cue. So the posturing begins…
Re: Dan Hughes (Comment #119658)
“It is difficult to establish the exact mechanism for this stronger heat flux to deeper water, given the diverse internal variability in the oceans.”
In other words, this mechanism has the virtue of being completely plausible while also being very hard to pin down. 😉
I noticed from Dan’s RC link that Rahmstorf is still pushing the terribly flawed analysis that he and Foster did.
Oliver, yep. The actual mechanism for the transfer of heat to the deep ocean is unknown.
So in spite of the fact that the deep ocean data are of uncertain validity and no model exists that can validate the apparent warming of the deep ocean layers without the surface layer warming, they are simply credulously accepted because, as far as I can see, they line up with prior expectations.
Carrick (Comment #119666),
Indeed, as is Tamino. One of the great things about climate science is that it is so predictable… you can always expect the scientist-advocates to continue to reference publications ‘proving’ catastrophic warming… no matter how poor the quality of those publications. The phrase ‘urban legend’ seems applicable.
SteveF, I thought it was pretty telling that Foster got apoplectic in his response to you. I never actually saw what looked like a coherent response from him, did you?
In addition to your work that appeared on this blog, there’s Troy Master’s work.
Kevin C appears to agree:
I’ve seen some pretty negative comments from other climate scientists… the group vote seems to be “silly curve-fitting exercise”.
Carrick,
“I never actually saw what looked like a coherent response from him, did you?”
.
Heck no! His paper was and is crap… pure and fetid. He bitched in his surly ‘Tamino’ way about how ‘wrong’ I was to linearly de-trend…. but he was perfectly willing to do the same when it supported his vision of catastrophic warming. (Justification? Justification!?! Tamino don’t need no stinking justification!) He never actually addressed the more substantive issues of non-physical solar lag and differences between solar and volcanic lag and sensitivity. I do wonder a bit about when radiation became non-fungible in Tamino’s world. I was actually a little disappointed with his lack of followup, but I can understand: it is hard to make a convincing case when you are working with rubbish.
It also doesn’t seem to make logical sense.
” roughly equal measure ” seems to be an attempt at quantifying the roles of variability and forcings and there is medium confidence in this. Yet there is low confidence in quantifying the role of changes in radiative forcings.
translated – I don’t know the value in the changes in radiative forcings but I know it’s about the same as internal variability (have I quantified that???). ehh!
Re: TimTheToolMan (Sep 24 22:17),
.
The more one thinks about the IPCC’s dilemma, the more one should believe that is just what they will do.
Let’s revisit your prediction at various intervals once the final AR5 report is published and the public response to its conclusions begins to emerge.
Now, if the warming trend resumes before AR6, the IPCC and the climate science community will consider themselves off the hook, even if the warming trend predicted by AR4 models, shifted to the right in time, remains below the lower boundary of the AR4 model ensemble.
But what if The Pause continues into AR6 and beyond, i.e. a flat or declining atmospheric global mean temperature in the face of ever-rising GHG emissions?
If that’s what happens, let’s all come back in another seven years to see just how convoluted the IPCC’s AR6 explanations became over that seven-year period relative to the previous AR4 and AR5 reports.
In any case, the IPCC and the climate science community will hang tough regardless of where GMT goes in the next two to three decades. It is all but written in their job descriptions they have to do this.
I detect a shift in the MSM. This week I’ve been hearing news reports from the CBC (Canada) and BBC (UK). Both have been including reports on the upcoming IPCC meeting. Both have been reporting business as usual but both have been reporting The Pause as well and both have at least been acknowledging that it’s a cause for concern among climate scientists.
(see: http://www.cbc.ca/m/touch/news/story/1.1868223 )
I don’t think computing forcing by itself is adequate to confirm or refute the plausibility of the IPCC statement. I think you need to at least use a one-box model to convert the forcing to a temperature time series and then look at the trends. Sample equation: http://www.gfdl.noaa.gov/blog/isaac-held/2011/03/05/2-linearity-of-the-forced-response/
Re: John N-G (Comment #119793)
September 27th, 2013 at 4:13 pm
OK I’ve done that and the effect is quite literally negligible using the same parameters as those which Professor Held used. The temperature gain associated with incremental forcing from GHG increases after aerosol offsets should be more than an order of magnitude larger than the volcanic plus solar change. So where do you want to go to after the elimination of that gem of an idea?
Sure. And to apply a simple one box model, you need to include all the forcings and see whether the change in volcanic aerosols and solar results in predicting a flat trend or has any significant effect. But the IPCC authors wrote a paragraph that doesn’t give any sort of computation as an explanation, they just say what they say which is that they conclude this based on the level of forcings mentioning only these two periods.
Beta
It won’t. 🙂
.
Let us suppose for purposes of argument that the excess heat trapped by GHG’s is in fact being sent into the deep oceans by some as-yet unexplained heat transportation mechanism, and that this unexplained heat transportation mechanism is The Root Cause of The Pause.
Is it possible that this unexplained heat transportation mechanism is a subcomponent of some larger global heat engine control mechanism — the very control mechanism postulated by Willis Eschenbach?
Beta
(1) Your hypothetical has not occurred.
(2) If it happened, the cause could be “low climate sensitivity”. That’s an entirely different mechanism from the “thermostatic” effect Willis suggests.
(3) To the extent that Willis’s theory is actually not very well described anything could be a “subcomponent” of the theory if the theory is true. However, until such time that Willis describes his subcomponents, we can’t know what behaviors are subcomponents. The consequence is there are no observations can even hypothetically be used to test “subcomponents” of his theory. So even assuming your hypothetical is correct thee answer is: who the heck could possibly answer that question when willis hasn’t described any subcomponents that make up his theory.
Re: lucia (Sep 28 13:05),
Lucia, concerning your response that is linked to above, you have indicated in other threads that you expect a warming trend to resume before the AR6 report is published.
For myself, I also believe that sooner or later, a warming trend will resume, but that it could just as well be later as be sooner.
Please forgive me if I’m asking you to repeat yourself, but how specifically would you characterize the emerging discrepancy between observed temperatures and the IPCC’s predicted temperatures?
–> Is there in fact a true discrepancy between observed temperatures and the IPCC’s predicted temperatures?
–> Has the rate of temperature increase experienced between 1975 and 1998 moderated since 1998? (If so, to what extent?)
–> If there is in fact a true discrepancy between observed temperatures and the IPCC’s predicted temperatures:
——- How long has evidence of the emerging discrepancy been clearly apparent?
——- How can the discrepancy best be characterized? Is it a slowdown? A hiatus? A pause? An unexplained divergence? An explainable but as yet unexplained divergence?
——- Is there some other more appropriate descriptive term or phrase that you would recommend as a short descriptor for the discrepancy?
——- Is there any evidence available which could be used to determine how long the factors which produced the discrepancy have been operative in the climate system?
Regarding that last question, if the explanation for the discrepancy is that the models overstate CO2 sensitivity, then of course that particular factor has always been operative, in which case a host of other questions must be raised — do we actually understand the mechanics of the earth’s climate system, just for one example.
Beta Blocker,
It would be nice if you would answer each of the questions you pose before asking others to do the same…. helps everyone understand where you are coming from. I rather suspect nobody will then take the time to answer, but I could be wrong.
Re: SteveF (Sep 28 19:33),
As I understand the IPCC’s position concerning The Pause (hiatus, slowdown, whatever you want to call it) they believe that if there is a difference between what the models predict and observed temperatures, the difference doesn’t make any difference.
While acknowledging there is always room for improvement, in their view, the models are generally valid and the IPCC’s approach to pursuing the science of AGW remains completely defensible.
SteveF, where I am coming from is that when I read Lucia’s commentary concerning The Pause — or whatever she wants to call it — and then when I read the various reader responses to those comments on this thread and on other threads, then I get the impression there may or may not be a true discrepancy between observed temperatures and the IPCC’s predicted temperatures, depending upon which position each reader takes regarding the true role and the true extent of the influence of GHG’s in the global warming which has occurred over the last fifty years.
It is not clear to me what the position of the lukewarmer community is concerning The Pause and its potential for invalidating the climate models either in whole or in part.
Does the lukewarmer community in general have a position concerning The Pause; and if so, what is the substance of that position?
If they do, how would they themselves characterize The Pause as to its nature and extent? Do they believe The Pause to be of such limited impact and extent that it has little or no potential to invalidate the climate models, in whole or in part?
I’m curious what your reaction is to Stephan’s reply to this comment:
http://www.realclimate.org/index.php/archives/2013/09/the-new-ipcc-climate-report/comment-page-1/#comment-414239
41
Adam Gallon says:
28 Sep 2013 at 2:31 PM
Discrepency between data & models as per Hans von Storch, http://www.spiegel.de/international/world/interview-hans-von-storch-on-problems-with-climate-change-models-a-906721.html
“At my institute, we analyzed how often such a 15-year stagnation in global warming occurred in the simulations. The answer was: in under 2 percent of all the times we ran the simulation. In other words, over 98 percent of forecasts show CO2 emissions as high as we have had in recent years leading to more of a temperature increase.â€
“If things continue as they have been, in five years, at the latest, we will need to acknowledge that something is fundamentally wrong with our climate models. A 20-year pause in global warming does not occur in a single modeled scenario. But even today, we are finding it very difficult to reconcile actual temperature trends with our expectations.â€
NOAA’s 2008 State of the Climate report said 15 or more years without global warming would indicate what was delicately described as a “discrepancy†between prediction and observation, we’ve achieved that length of time now.
We have CO2 emissions above Dr Hansen’s “Scenario A†levels, with temperatures at his “Scenario C†levels.
http://orssengo.com/GlobalWarming/Hansen1988Fig3b.PNG
Oh and why do you want me to run “analytics.js�
[Response: Unfortunately Von Storch has gone to the media with this statement without a peer-reviewed publication to back it up, so there is no way for other scientists to check or have any basis for commenting on it. -stefan]
um… Stefan
sue,
Stephan is disingenuous at best. Von Storch has published his paper and supporting docs on the web. Anyone, not just “scientists” can review it. Futhermore his results are consistent with other studies.
Beta Blocker (Comment #119833),
Lucia shows that there is indeed a discrepancy between model projections and reality; I am not sure why you would think otherwise after seeing the many analyses she has done which show this discrepancy. that has absolutely nothiung to do with the influence of GHG’s on surface temperatures. The models are almost certainly projecting more warming than has been observed. The implication is that either assumed forcings are too low (on net) or climate sensitivity in the models is too high.
.
“Does the lukewarmer community in general have a position concerning The Pause; and if so, what is the substance of that position?”
I am not sure such a community exists, but if it does, I would not presume to speak for it. I can speak for myself: the pause seems to be due to a combination of factors, including some influence of ENSO, which if accounted for, shows the warming has slowed quite a lot but not stopped (about 0.075C per decade oer the last 15 years). There is a substantial divergence between models and reality (even after taking ENSO into account in both), and this seems to me most consistent with the models be too sensitive to GHG forcing. Empirical estimate (like Nic Lewis and several groups have already published) place the most likely sensitivity well below the model mean, and those estimates seem to me much more credible, because there are fewer assumptions, parameterizations, etc. involved.
.
What I think you can safely say is that ‘lukewarmers’ consistently believe that GHG’s do warm the Earth, and that rising GHG’s in the atmosphere pretty much have to lead to continued warming. So lukewarmers tend to see GHG driven warming as a potential problem, and one that needs to be carefully considered and paid attention to. But it is not an existential threat; it is just one of many substantial challenges that humanity faces, all of which need our attention. If you look at teh backgrounds of those who call themselves lukewarmers, I think you will consistently find that they are technically trained, many (most) with advanced degrees in science and engineering, and are genuinely skeptical of the projections of doom made by many climate scientists.
Ahem. That’s why they call it a summary. All details will be provided (or not) on Sept 30 when the WG1 report is released, in boxes 9.2 and 10.2 and section 10.3.1.
I would like to go and say that you’ve refuted the IPCC statement where Lucia hadn’t.
John N-G…. Yes. And the leaked version of Chapter 9 wasn’t exactly convincing either. 🙂
But to a large extent, I want to hold back on detailed discussions until the final versions of the supporting documents are published.
Beta Blocker (Comment #119824)
Sorry, but I don’t take well to comments that are nothing but series of homework assignments or nothing more than requests to repeat things I’ve said in various places before. If there is some point you wish to make, make it.
Beta
No one can speak for the entire lukewarmer community. Different people have different notions about what what to call it, what it means, what we can conclude from it and so on. As for this question “Do they believe The Pause to be of such limited impact and extent that it has little or no potential to invalidate the climate models, in whole or in part?
I don’t even know what that means. If your asking whether “models” are “invalidated”… we’ll that can only be answered if you explain what it means for a model to be valid. I tend to talk about whether observations are consistent with projections. That’s not the same thing as discussing whether “models” are “valid”. Since I don’t know what you mean by a “model” being “valid”, I can’t begin to guess whether a pause or haitus of any length could ever invalidate or validate a model.
And beyond that, there are whole bunches of questions in there for which my main thought is “who cares”. For example:
“How can the discrepancy best be characterized? Is it a slowdown? A hiatus? A pause? An unexplained divergence? An explainable but as yet unexplained divergence? ”
Who cared whether it’s called a ‘slowdown’, hiatus, pause or what not?
“
I was much impressed with the OP but upon pondering over it some more, two issues occurred to me. Or maybe that’s one quibble and one real issue. The quibble concerns this claim:
“[…] CMIP5 guidance told modelers to use the solar cycle as measured up through 2008 and afterwards repeat the 23rd cycle. So, numerically, there is very little excuse for pinning any disagreement on the solar cycle.”
This is a valid criticism *if* the fact that the recent 15 year period only covers about one and a half solar cycle is being used as an excuse for explain (part of) the model discrepancy with observed temperatures. But it is perfectly valid for simply explaining the recent slowdown in the warming trend. And that seems to be what the quoted IPCC claim is addressing.
Now for the main issue. What must be explained is the reduction in the warming trend in the recent short period (14 years) compared with the recent long one (61 years). The volcanic forcing seems flat over the short period. Its average over that period is higher than its average over the long period (or the previous 47-year segment). Lucia seems to infer that this should lead us to expect a more positive trend over the 14-year period. But this should only be expected if the transient response is very slow and regular. If it is initially quick, drops off fast (within just 3 or 4 years, say), and then has a long tail with very little slope, it will have very little effect on the trend over the latter 14-year period. On the other hand, the fact that the volcanic forcing is close to zero over the 14-year period will have the effect of raising the 1951-2012 trend compared with the 1951-1998 trend while the 1998-2012 trend remains flat (still assuming a fast transient response). So, the 1998-2012 trend will be more negative compared with the 1951-2012 trend than it was compared to the flatter 1951-1998 trend (still only considering volcanic effects on temperatures for now). And that must be the main IPCC point.
Expressed differently, it’s the very fact that recent temperatures have been caused, by the (lack of) volcanoes, to be stalled at high values that has increased the long term trend since 1951 and made the recent slow down appear more dramatic.
Now, regarding solar forcing, my main point is analogous albeit simpler. It also seems that the transient response to rather fast changes in forcing (more than 0.3W/(decade*m^2), say) have the shape described above. However what is mainly relevant in this case is the temporally *restricted* effect of the solar cycle on the trend within the 1998-2012 period. It’s just the fast transient response that lowers the trend. Over the last 61 years the solar-cycle has had little effect on the long trend. And the fact that the average forcing over the *whole* recent 14-year period was lower than the average solar forcing over the previous 47 years has little significance compared to the fast transient response within the recent period. It’s just a long tail effect with little incidence on the comparative slopes between the different periods.
Since I don’t know the shape of the actual response to the relevant forcings, and lack the skills to model the process, I can’t quantify this any better. But it seems intuitively reasonable and it makes sense of the IPCC claims. That may be something to consider.
Pierre
Sure. But read John N-G’s comment above. Not he says to discuss whether solar/volcanoes to be the reason for a slow down, we should at least use a simple model like at Helds blog (or Lumpy I used to frequently discuss here.) But in the AR5, they highlight AOGCM and even with the solar forcing oscillating down in those models, the model mean does not collectively drop during that period. So whatever the effect, it is not strong enough to see when we average out the noise over many runs of many models. So, on the one hand, solar is given as a “reason” and on the other hand, the projections which contain the solar forcing do not show a flattening arising from that “reason”.
That’s not what I infer. I mostly infer that the paragraph ought to have been gone over by a copy editor because– actually– I don’t think that’s what the authors really mean. And I don’t even think it’s a “summary” of other more detailed arguments in the body of the report as John NG implies one ought to expect it to be when placed in a summary. But the other chapters ought to come out today, so we’ll see.
Why in the world would the time constant for a response be initially quick and then slow? This would be a very, very odd thing to claim and would need quite an involved argument and good evidence to support it. (Either that, or I don’t understand what you are trying to say.)
And if there is a fast response and then slow recovery, why wouldn’t we see the same thing with Pinatubo? If that were the case with Pinatubo, we’d still be seeing a upward trend from the temperature recovering from Pinatubo which was much stronger than the recent three piddly eruptions. That argument doesn’t really work. But I’ll wait for the IPCC to make that sort of argument before criticizing them for saying it!
Paul_K went ahead and applied Issac Helds simple response model. The IPCC claim really isn’t going to hold up– because to hold up, you have to forget that other forces are supposed to be acting too. I’m waiting for the final report to make more involved comments as at least in principle things can change.
Lucia: “I don’t even think it’s a “summary†of other more detailed arguments in the body of the report as John NG implies one ought to expect it to be when placed in a summary.”
One might expect such if the authors of the summary are the same as the authors of the body. But we’ve seen that the draft summary has been bowdlerized by governmental representatives who apparently don’t want to present any factual statements which might undermine the policies they favor. Perhaps the SPM should be renamed “Summary *from* Policy-Makers”.
Lucia and SteveF, what you are saying in response to my questions is that The Blackboard is not acting as an Alternative IPCC which is attempting to champion a particular alternative viewpoint concerning the scientific issues surrounding both climate change and the specific conclusions of the latest IPCC report.
As I interpret your responses, The Blackboard exists not to gain consensus agreement concerning the basic scientific questions surrounding climate processes and climate change, but to provide a forum where those with an interest in the nitty-gritty details of the science can get together and offer up their own fairly detailed technical and scientific insights into those questions.
One viewpoint is as good as another here on this forum as long as a contributor offers a properly supported analysis which does not violate the laws of physics and which does not veer off into the weeds by pushing outlandish notions such as there is no true greenhouse effect operating in the atmosphere.
Beta Blocker,
You seem to be trying to imagine some grand purpose for this blog. To be clear: The Blackboard is my hobby blog. I have never even remotely imagined it exists as “an Alternative IPCC” nor does it exist to “to champion a particular alternative viewpoint concerning the scientific issues”. I have no idea why anyone would have imagined such a reason for it’s existence.
As for this conclusion, all I can say is “huh?”
On the one hand: If you have a claim and can explain it, people will be interested in discussing that. As many claims about climate change do end up being being about physics and not leprechaun-o-logy, generally many people claims will draw on physics as support.
If you admit a claim is based on intuition: fine. If it’s based on linear extrapolation (which is not physics) fine. If extraterrestrial aliens told you: fine. Admit that’s your basis. People probably won’t give your claim much credence if it’s based on communication with extraterrestrials, but at least we’ll know that is your basis.
But if you start making claims like “x violates the 2nd law of thermo”, people are going to ask you to explain your claim that “x violates the 2nd law of thermo”. It doesn’t matter whether ‘x’ is saying you think there is no true greenhouse effect of whether you are saying there is a true greenhouse effect. People who understand the 2nd law of thermo are going to ask you to explain how in the world you applied the 2nd law so as to conclude that the 2nd law requires ‘x’.
The same things happens if one makes a claim that they earth has a “thermostat” of some sort. People here will tend to ask for a phenomelogical basis for that– and ideally, they are going to want to read one that at least fleshed out enough to plausibly create a thermostatic basis. Not just “look at this cool article about plankton”!
As for any suggestion that somehow the notion that suggesting “here is no true greenhouse effect operating in the atmosphere” is forbidden: it’s not. But if you want to advance that, you need to explain how that can be justified based on our general understanding of things like radiative physics. So far, I’ve never seen anyone who makes that claim come up with anything remotely reasonable. I’ve seen various people (a) call the navier stokes equations the 2nd law of thermo, (b) invoke ‘chaos’ (as if either the earth is chaotic or the greenhouse gas exists which is nonesense), (c) decree the entire concept of average temperature doesn’t exist, (d) say that models projections being off means that the greenhouse effect doesn’t exist at all, (e) say that people in other fields don’t believe in back radiation (a claim that would come as a surprise to people who design furnaces or engineers who work on all sorts of projects or just people who know how a thermos works).
All of these things are totally inadequate as attempts to overturn radiative physics– and if someone advances them, people will tell them so.
Beta Blocker (Comment #119875),
Yikes! I didn’t say anything about why Lucia runs The Blackboard, and she has (in my memory) never said why.
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I comment here (and have made some guest posts) because the blog content is generally interesting (scientifically) and usually relevant to climate science. My only personal objectives are 1) to learn, and 2) to try to make sure poor quality and/or biased climate science is called to task. Bad public policy could result from bad climate science, and I would like that to not happen.
SteveF –
I’d like to add that bad public policy can result from good climate science as well…Weren’t there warnings about the inadequacies of NO levees and the danger of NYC coastal flooding from previous storms, which were ignored or back-burnered?
My impression is that climate science is being used to rationalize certain policy actions, which are taken more because they benefit certain companies/factions or disadvantage certain other companies/factions, or because they provide an opportunity for political self-aggrandization. Yes, that’s cynical. Someone was asking for the “lukewarmer view” — my view is that this is an area of concern, but not of alarm. “Concern” won’t get a lot of legislators moving, but alarm will. Hence the amplification of alarmed voices and the muting of merely concerned ones.
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Lucia and SteveF …. Willis Eschenbach’s speculations concerning the possibility that the earth’s heat transfer and distribution mechanisms are influenced by some sort of natural self-regulating thermostat are intriguing to those like myself who tend to view the earth’s large-scale natural processes somewhat mechanistically.
An so The Pause may be one reason to further speculate upon the possibility of the existence of such a natural thermostat.
But so far as I am aware, there has not been any kind of documented, well-organized, and comprehensive analysis which lays out the case for that possibility in a way which goes beyond mere speculation and which matches — in its scope, in its level of detail, and in the quality of its argument — the highly ambitious nature of that particular speculation.
Publication of the AR5 report is an opportunity for Willis to put together a documented, well-organized, and comprehensive analysis which lays out the case for the existence of his speculative natural thermostat. His arguments and his analysis can then be peer-reviewed here and elsewhere on the Internet, for better or for worse.
Beta Blocker
You can be intrigued all you like. But I’d be interested in you definition of “mechanistically”. Do you define mechanistically as
(a) “behaving like an engineered system with mechanical components created by a designer incorporated a thermostat”? Or
(b) “obeying the laws of mechanics, thermodynamics and heat transfer”? Or
(c) something else.
Because I usually use ‘mechanistically’ to mean (b) and I think I view the earth’s large scale natural processeses do (b) but I find it almost impossible to reconcile Willis’s view with (b). So using my definition Willis’s view is nearly impossible to reconcile with a mechanistic view of earth’s natural processes.
On the other hand, it might match (a), but I don’t really apply “mechanistically” to view (a). I would apply “Believing in the guiding hand of God” or something like that to view (a). Or possibly “religious”.
On the other hand, maybe you have another definition of “mechanistically”. So if you could share, that would help clarify what you mean.
At least you seem to be admitting it is speculation and that as far as you are aware, no one has done anything to find any basis of support for this particular speculation.
Of course Willis could better describe his speculation. For now, he really hasn’t other than suggesting some sort of thermostatic process exists. Period. No more. Those of us who actually have studied mechanics would point out he has not advanced any mechanism that might result in the existence of the “earth thermostat”.
Lucia asked: “Why in the world would the time constant for a response be initially quick and then slow? This would be a very, very odd thing to claim and would need quite an involved argument and good evidence to support it. (Either that, or I don’t understand what you are trying to say.)”
Yes, you’re right. This part of my argument was ill-conceived. I had also incorrectly assumed the time constant of the transient climate response to be much shorter than it likely is.
I still have trouble, though, with your suggestion that the solar effect over the 1998-2012 period ought to be neglected because it is more than compensated by the volcanic forcing effect. You relied on a comparison between the average forcing over long (1951-1998) and short (1998-2012) periods. However — what is close to my original point — this difference would be relevant if this were comparable to a step change in forcing occurring around 1998. But the negative volcanic forcing was completely over some time before 1998. I would therefore assume the TOA imbalance to have been restored to its normal long term sustained level (about 0.6W/m^2 say) and not have an incidence on the climate response after 1998. It therefore can’t cancel the climate response to the solar-cycle within the 1998-2012 period. This later effects certainly offsets a significant chunk of the enhanced greenhouse effect. I am puzzled that this is not shown in the model ensembles that you mentioned. Is it just lost in the noise? The newly released AR5 WG1 notes that “Solar forcing went from a relative maximum in 2000 to a relative minimum in 2009, with a peak-to-peak difference of around 0.15 W m–2 and a linear trend over 1998–2011 of around –0.10 W m–2 per decade” This is 1/3 of the greenhouse forcing trend for the 19510-2011 period.
This doesn’t fully account for the pause but my issue is with one central argument of your blog post: that the history of volcanic forcing over the whole period under considerations ought to more than offset the recent solar-cycle effect. The volcanic forcing is short lived. For the volcanoes that occurred during the early period to have a lingering effect on the climate response during the 1998-2012 period there would need to be a residual effect from the Plank response to the earlier disturbance. The volcanoes would have reversed the slow Plank response (surface warming) to the enhanced greenhouse effect while the sulfate forcing was effectively reversing the TOA imbalance. It then would have yielded a larger positive TOA imbalance at the start of the 1998-2012 period. But this would only had been effective in boosting the warming trend if there had not been the large El Nino in 1998 that greatly increased surface temperatures above the trend and thereby boosted the Plank response, thus erasing the lingering volcanic effect after 1998.
Pierre,
If the IPCC wished to make a more nuanced argument involving the shape of the changes, they could do so. I’m merely reading their exact words– involving nothing but average levels over periods– and showing that what they wrote did not make sense.
I am not rebutting all other possible ways of interpreting the solar/volcanic data.
As it happens, the write more in chapter 9. What they write there is a confusing mess.
Lucia,
They only presented their discrete periods as baselines for average temperature trends. They invoked the particular solar and volcanic forcings, in addition to internal variability, as potential explanations for the reduction of the recent trend. They never invoked the average forcings over the extended periods, in the way you did in this blog post, as part of their own explanation. This is something you read into their arguments that just wan’t there, it seems to me.
It turns out that the volcanic forcing they were talking about just is the forcing within the recent period and had nothing to do with the forcing over the earlier period. The same is true for the solar forcing.
Finally, the nuances (you may say convolutions) in my argument weren’t offered as a proposal to improve on their insufficient argument. Their explanation of the hiatus was simple enough. My convolutions only were required to show that their simple argument was immune from your specific criticism regarding the volcano forcing effect allegedly offsetting the solar forcing effect. This alleged offsetting effect seems to me not to exist whatever way they own exact argument might be construed.
Nevertheless, you’ve been gracious enough to consider my claims and respond. I’ve made my point as best as I could and would feel guilty to bother you more about a rather unimportant issue. Maybe if others can see where I might have gone wrong or might have missed some key points of your positive argument (regarding the warming effect from volcanoes being larger than the cooling solar effect) they might jump in.
Pierre
This is silly. One cannot compare the effects of forcing on temperatures in periods 1 vs. 2 and only discuss forcings in period 2. Whatevever point one wishes to make, it must relate to relative forcings in the two periods.
So? One can discuss their own exact argument or their description of their argument even if someone else could come up with a different argument that might be more plausible.
Not a bother.
I don’t think you’ve necessarily gone wrong on an argument that could be made. I just continue to think they made a bungle in their statement in the SPM.
Anyway, if you do the exercise John N-G suggested, picking parameters Isacce Held finds fit his model, one finds that the net effect of volcanic forcing had they acted in isolation would have been -0.04C/decade. But this is not enough to “explain” a 0 trend given that the effect of increased GHG’s was expected to result in a trend of 0.2C/dec according to the IPCC in the AR4. So if someone is resorting to a longwinded verbal discussion trying to ‘offset’ predictions, one would at best discount the 0.04C/dec from the 0.2C/dec and 0.16C/dec. (Mind you in the ‘box’ section in Chapter 6 discussing this, they don’t mention what trends would be anticipated.)
Meanwhile, the from the 50s-now would have been some smaller value (which I didn’t compute– but much smaller). So, the net would not have been to ‘expect’ that the trend from the 1998-2012 should have been smaller than the trend from 1951-2012. (And in Chapter 16, they pretty much say this. The change in the aerosol/volcanic is not enough to explain either why the trend from 1951-2012 is higher than that from 1998-2012 nor to explain why the trend from 1998-2012 is so low.
Oh… btw: if you put volcanic effects only into an simple lumped model, you would expect the trend from 1951-2012 would be more negative than the trend from 1998-2012! This is true because the volcanic loading generally declined from 1951-2012. So, even if one discusses volcanic and solar only, any decline ought to be purely solar, not volcanic.
In anycase though: it really doesn’t make sense to just compare trends in solar in volcanic or even the trend in total forcing without considering the over-burden of accumpulated. To do so ignores the heat capacity of the climate system which (a) does exist and (b) is constantly invoked when warning people that even if we don’t moderate GHG’s the earth will continue to rise.
So the entire discussion in Chapter 9– which this presumably summarizes– is a mess making implicit assumptions that (a) violate physics and (b) everyone would criticize ‘dragonslayer types for using (which they do when they draw all the graphs showing that CO2 rose while trends fell over a period of 10 years and suggest this means CO2 doesn’t cause warming!)
The average forcing over the whole periods obviously tells us nothing about the cause of the temperature trend over the *earlier* period. This earlier period wasn’t sensitive to whatever was going to occur, in the future, during the last period. The forcing *trend* over the earlier period is more relevant to explaining the temperature trend over that period because it is responsible for sustaining the TOA imbalance while the Plank response (the surface warming) regularly increases. The forcing average over the last (short) period has some relevance because it can mark a deviation from the earlier trend. But the forcing *trend* over the last period also is relevant, just as it was over the earlier period.
the net effect of volcanic forcing had they acted in isolation would have been -0.04C/decade. But this is not enough to “explain†a 0 trend given that the effect of increased GHG’s was expected to result in a trend of 0.2C/dec according to the IPCC in the AR4.
There is no need to explain a zero trend since the observed trend was at least 0.04C/decade (depending on the data set). So, the discrepancy to be accounted for just is 0.16C/decade. They never suggested that either natural variability, the solar forcing, or volcanic forcing, in *isolation*, were separate candidates for explaining the hiatus. They rather claimed that internal variability accounts for about one half, while changes in forcing (solar + aerosol; in some combination) might account for the other half. So, if internal variability (the large El Nino in 1998, the two recent La Nina episodes, etc.) can account for 0.08C/decade, and volcanoes for about 0.04C/decade, then solar forcing (and possibly some contribution from anthropogenic aerosols) only need account for another 0.04C/decade.
Yes, I agree with this. What must be understood indeed is what caused the trend to be lower than the expected 0.2C/decade. (This was not a short term forecast, though, but just an expectation — just as the expected value for two dice throws is 7; which is not a forecast either. The expected value becomes a forecast over periods long enough for the variance to become small relative to the magnitude of the expected signal.)
That’s true, but it still partly explains why the recent trend is 0.16C/decade lower than expected. It explains 1/4 of the hiatus, which is all that’s required of it.
I am unsure I understand this argument. The large heat capacity of the system explains two things. It explains why the the transient response is long to achieve and, thereby, why there remains a finite TOA flux imbalance when the forcing varies monotonically.
In this case, were it not for natural variability and its effects on surface temperatures, and thereby on the TOA imbalance, then the TOA imbalance at the start of 1998-2012 would be the dominant factor at the start of the period for determining the temperature trend at that time. Subsequent small changes in forcing would modulate this only somewhat, because the total imbalance would be large compared with the forcing change.
But as I had suggested earlier, internal variability already had pushed surface temperature above the long term trend in the lead up decade to 1998, and even more so with the large 1997/98 El Nino. So, the TOA imbalance was quite reduced in 1998 (to about 0.25W/m^2, I think). It then most likely rose in the later part of the 1998-2012 period as a result of the reversal of the PDO. This increased the TOA again. But when the TOA is thus increased “from below”, as it were (i.e. from sea surface cooling through upwelling, rather than through increased external forcing) the result isn’t an increase of global surface temperatures, obviously, but just an increase in the rate of ocean heat uptake.
hadn’t the IPCC ignored this in their argument, then this would only strengthen it, so far as I can see. But they just didn’t bother to discuss the ENSO effect in any detail in their little hiatus box. They simply suggested that internal variability could easily account for half the hiatus effect, which seems plausible enough when one considers, e.g., Kosaka and Xie, 2013.
My html quote tags (bracket, “q”, bracket) don’t have the expected effect. I wanted to indent the quoted text in the same way you are doing.
I also forgot to put the paragraph beginning “[…]the net effect of volcanic forcing…” between quotes. For some reason, I can’t edit my message. When I click on the “Edit” button, an empty editing box comes up.
Pierre
Emphasizing the word “trend” doesn’t make what you said any more sensible. What you wrote is this
The forcing *trend* over the earlier period still involves the volcanic and solar forcing in the earlier periods just as much as they are involved in the trend does for the later period. If they are referring to that period and referring to volcanic forcing, it is silly to suggest that somehow, “they” aren’t discussing volcanic forcing in that earlier periods but only the volcanic forcing in the later period. (Or if “they” aren’t considering the trend in the volcanic forcing in the later, then “they” are being even sillier than I have previously suggested.)
If they are comparing the *trends* in forcing in period 1 and period 2, in order to explain the relative trends in temperature then the trends in both periods must matter. (And it happens that the trend in volcanic forcing in the earlier period is larger than in the later period.)
Sorry. I thought you’d been following other people’s comments too. John N-G brought up an particular issue, and Paul_k did also. In (John N-G (Comment #119793) you will find a link to Issac Held’s blog where Issac disscusses a simple 1-d model. These are discussed here too from time to time. Unfortunately, Issac Held’s blog is dead for the time being because NOAA (for some odd reason) decided to do extra unnecessary work turning off their web pages because of the federal government shut down. (For all I know the odd reason is a legal requirement. But basically Issac’s blog is on a NOAA server and it’s currently turned off due to political issues.)
But the model is basically a model that assumes
C dT/dt = -γ T + F
Where “C” is a constant related to heat capacity, γ is the rate of heat loss radiated into space (linearized) and F is the applied forcing. Issac found the parameters that best fit the gfld model. One can integrate with Forcings from 1850 and see what results one gets.
Precisely. If the earth has not ‘equilibrated’ to the forcing long before even 1951, or 1998 (or any periods you wish) the forcing imbalance at the start of the period must be considered. And it happens that if you run the 1-d model like that discussed at Issac Held’s blog, the solution dictates that the trend after 1998 would still be large.
And what was it in 1951? But in any case, the paragraph we are discussing is not explaining the natural variability part. They are trying to discuss the deterministic part. So, the El Nino part is irrelevant here. That is not a “volcano” or “solar”. It’s fine to attribute the change to natural variability– but just remember, that’s not relevant to the discussion of the deterministic effects arising from the change in trend due to vulcanism or solar.
On the quotes you need <blockquote> not <q>. I fixed.
Lucia,
I’ll come back to some earlier points at a later time. For now:
Of course I expect that. I expect something around 0.5W/m^2 to 0.8W/m^2 when the models merely responds to historical forcing in recent decades (and also discounting internal variability), since this is the TOA imbalance that I usually see quoted (Hansen or Trenbeth).
But you have mentioned that the net effect of the volcanic forcing, considered in isolation, in the simple model, was to produce a negative temperature trend of -0.04°C/decade. But in your original post you had suggested that, on account of the average volcanic forcing being higher over the last period than it was over the early one, it would promote warming and hence more than compensate for the solar cooling effect. Had I misunderstood you?
Sorry for not having followed the whole discussion in great details. I had only perused all the message after reading the OP in order to see if my (initial) main point regarding your averaging argument had been addressed and it had not seemed to me that it had been. The topic you now point me to seems interesting and I will attend to it when I can, possibly after the NOAA site is back up, if ever.
One final thing, for now. You are right that my discussion of internal variability in the context of the discussion of the overall volcanic effect on the trend variation must lead to double counting. That was a mistake since I was committed to making sense of the separate IPCC attributions (one half/one half) of the cause of the hiatus to internal variability and forcing.
(Cool… I am again able to edit now.)
There is another isolated point, though, that I’d like to come back to.
We are agreed that explaining the “pause” can boil down to two different things. One might undertake to explain why the trend after 1998 was lower than the trend from 1951 until then. But one might also undertake to explain why the trend since 1998 is lower than the 0.2°C/decade of the model expectation for the first couple decades following 2000. The second explanatory burden is much higher since the baseline trend is much higher.
I had suggested that the fact that the 1998-2012 period covers an uneven number of solar-cycles can be invoked to explain the recent slowdown, which is the first burden mentioned above. You yourself had suggested that this can’t help one meet the second burden since the models used a repeat of the previous solar-cycle as part of the input forcing for the 1998-2012 period. So, the only solar effect that the IPCC would be entitled to invoke to explain the model/temperature discrepancy would be the unforeseen length and depth of the recent solar minimum. I was agreed with this. But not anymore.
It just occurred to me that the IPCC never “predicted” that the 0.2°C/decade trend would apply to just any short future periods that might cover uneven numbers of solar cycles. Expressing such an expectation would simply amount to denying a priori that the solar-cycles can have any short term effects at all beyond the effects from unforeseen variations in the secular trend. The 0.2°C/decade expectation cover the near future (after 2000) and ought only to strictly apply to periods that average out the (climate response from the) variation within complete solar-cycles. That was not an expected trend (let alone a forecast) for the specific 1998-2012 period. So, they are entitled to invoke any solar-cycle effect that might have lowered the 1998-2012 trend as compared with the model expectation. This expectation isn’t meant to be (nor can it possibly be) scaled down with perfect accuracy to produce an expectation for short periods that cover incomplete solar-cycles.
Re: Pierre-Normand (Oct 2 09:32),
The problem is that the TSI change from the solar cycles is not enough to explain a significant part of the temperature change. For solar cycles to be a factor, you have to invoke new physics that definitely aren’t in the GCM’s. And as with multi-decadal quasi-periodic oscillations, the end result could be a significantly lower climate sensitivity to ghg forcing as the solar cycles could be responsible for part of the rapid warming as well as the less rapid warming.
DeWitt Payne,
That’s not a problem for me. I wasn’t arguing in this specific post that the solar-cycle effect was sufficient for accounting for the recent hiatus, or even that it was significant. I was rather arguing against the validity of a specific argument for discounting it completely. Of course it is equally responsible for contributing to temporary increased-warming episodes as it is to temporary reduced-warming episodes. But the secular trend is negative since 1960. And it is acknowledged that it contributed some part of the early 20th century warming.
Pierre-Normand
The text doesn’t compare the after 1998 to the 1951 until 1998. It calls out 1998-2012 and 1951-2012. The trend in volcanic aersols is piddling in both cases.
I am not saying it would promote warming.I don’t think you can really make any claim one way or the other by either comparing
(a) the trend in the two periods or
(b) the mean in the two periods.
And I think the paragraph in the SPM and the longer discussion in Chapter 9 is nothing but a confusing mess.
I think no matter what you do you need to account for heat capacity of the system and so you cannot do either when presenting an argument. If we use the fit to Isacc Helds model which has one of the smallest response times I’ve seen for a transient response, we get this sort of response if the only forcing was volcanic:
(BTW: I’m lucky I could run that. I was able to load http://data.giss.nasa.gov/modelforce/strataer/tau.line_2012.12.txt, but I can’t load http://data.giss.nasa.gov/modelforce I assume the problem is the federal government shut down. I had hoped to snag their other forcings to illustrate things a bit better. I suspect from your name you may not be American, but things like NASA and NOAA are shut right now. )
I’ll put up solar forcings in a moment (and the sum).
Accounting for very small amounts of heat capacity, here is what we get for solar alone and solar with volcanic:
Note that if we look at solar&volcanic, we expect cooling during both periods. So, while one can go on about this, none of this makes any sense unless you also discuss the forcings that are thought to have caused warming between 1951-2012. Because otherwise, standing alone, the question is: Why didn’t it cool between 1951-2012? And while we know the answer to that is “GHG’s are much, much, much more important than solar and volcanic”, that just puts us back to “So what about this tiny change in volcanic and solar?
(I’m sure you are wondering… so why doesn’t lucia add GHG’s. I planned to do so.. but the government shut down is making some of the pages unavailable. I may be able to fiddle and get the nasa forcings for other things– after all I can get their volcanic forcings– but right now since I can’t load the main page, I don’t know the uri for the ghg forcings which might load. I have to admit: I’m not quite sure why static pages are off line… but whatever. Delaying blogging is not the worlds largest tragedy!)
Pierre-Normand
I’m not advocating discounting it. I’m just finding the argument in the chapters of the IPCC confused.
And as mentioned above: possibly the solar explains about -0.04 C/dec of the slowing which would still leave +0.16C/dec of warming in an adjusted projections. But this is still much higher than we’ve seen. (Which leaves ‘internal variability’ and/or ‘models warm too much’ as explanations.)
No. The trend in the multi-model mean from the AR4 based on Jan 1998-Dec 2012 is 0.2165 C/decade. The trends between 1994 and 2000 tend to be high owing mostly to the recovering from Pinatubo.
Yes. But if so, that means they should knock the -0.04 to account for the unforseen decline in solar, and the adjusted trend is 0.1765 C/dec rather than the 0.16 I suggested when I gave the IPCC the benefit of the doubt and mentioned their 0.2C/dec projection.
No. But if you or they are going to explain slowed cooling in terms of solar forcing to and explain away a forecast, one must make some estimate. I tended to round in favor of the IPCC argument– only putting the 0.2C in their mouths when 0.2165C/dec is the more correct warming trend in the IPCC projections for that period. So: the solar decline would not explain the haitus. One is still left with ‘internal variability’ or ‘models over estimate warming’.
Lucia,
Actually, in post #119934 you had written:
This got me on a wrong track. Now, in light of the new data you presented, I suppose you misspoke and meant to refer to the effect of solar-forcing, not the volcanic forcing. The IPCC also considers non-volcanic aerosols. Is the data easily obtainable for this? In any case, as they acknowledge, because of uncertainties stemming from uneven spatial distribution, the confidence level is low regarding the net effect of aerosols.
Thanks for the new analysis and for correcting me about the time frame of the AR4 model projection. I hadn’t realized that a projection even higher than 0.2°C/decade had been produced specifically for the period 1998-2012.
Yes. I mean -0.04 is combined. Sorry.
I don’t know yet. The CMIP5 data set might have some guidance for anthropogenic but they left most of the natural up to individual groups.
The document doesn’t state one. What it does is:
1) Explain how they came up with the multi-model mean.
2) Provide a graph of the multi-model mean.
3) Provide numerical estimates for defined periods based on the multi-model mean. (In principle these could be read off the graph, but in practice that’s difficulties.)
4) Provide uncertainty statments.
But afterwards, Geert-Jan Van Oldenberg placed all the runs here:
http://climexp.knmi.nl/selectfield_co2.cgi?id=someone@somewhere
It’s possible to download and apply the methodology that replicates all of 1-4 above. (Except they smooth their graph which is evident if you apply the methodology)
It turns out that the multi-model mean trend from 1980-2030 and that from 2000-2030 are both very close to 0.2C/dec (but actually a bit higher.) But there is a big dip after the eruption of Pinatubo. So, around 1990-1993 or so, the trend is negative. But from 1993-199x it warms at a faster rate. Since I’ve downloaded these and computed them many times (I have a script in fact.) So I was pretty sure the trend from 1998-2012 would be higher than 0.2C/dec. I’ll slap up a graph to show you in a sec.
Pierre-Normand,
These were the respective trends in the AR4:
The trend for the later periods was projected at 0.2165377 C/dec. That for the earlier one 0.1453312 C/dec. If we subtract 0.04 from the later period we get 0.1765377 , which is still larger than the trend for the earlier period.
So, you would still need “more” to get the AR4 model based estimate for the deterministic trend in the later period below that for the earlier period.
I could do this for the AR5– but really, the entire discussion in the AR5 is bizarred because it’s not accounting for heat capacity at all, and they certainly aren’t going to explain “0”. in one place they do admit that all this still doesn’t explain the hiatus. You need a larger than anticipated level of natural variability to ‘explain’ it. (Not that you can’t get 2σ weather events. You can. But you do need quite a bit of unexpected cool weather to get explain the low observed trend.)
Lucia are you looking at both Ch 8 and 9 for the numbers?
AR5 chap 9 box 9.2 say:
The reduction in AR5 best-estimate ERF trend over 1998–2011 compared to both 1984–1998 and 1951–2011 is mostly due to decreasing trends in the natural forcings,–0.14 ± 0.10 W m–2 per decade over 1998–2011 compared to 0.0 ± 0.01 W m–2 per decade over 1951–2011
I have some trouble with your post Lucia.
Your result differ from GIEC ones maybe because of different dataset (see annexe 2 for GIEC ones).
AR5 state: After 1998, however, some contributions to a decreasing ERF trend are missing in the CMIP5 models, such as the increasing stratospheric aerosol loading after 2000 and the unusually low solar minimum in 2009
Did GISS dataset use real forcing or did they set volcanic and solar forcing to 0 for the two last years (GIEC recommendations for inter-model comparisons or something like that, my memory can fail).
One detail that I have trouble with. GIEC natural forcing trend for 1951-2011 is 0,0. Why did they use only a single digit instead of two like in all others number ? We have a very good accuracy for this period (± 0.01). In fact one order of magnitude better than all others number given for aerosols. So maybe they found 0,00 and they rounded it, or maybe their computer gives them 0,0 for a different reason than an exact inverse match between volcanic and solar forcing.
On the putative dataset problem, here what AR5 say about the forcing, the models and the “pause”:
Nonetheless, over 1998–2011 the CMIP5 ensemble-mean ERF trend is lower than the AR5 best-estimate
ERF trend by 0.05 W m–2 per decade