Victor Venema and Judith Curry were having a Twitter discussion yesterday about uncertainty. I think – although Victor can correct me – that Victor was trying to get Judith to acknowledge that uncertainty works both ways. Even though it is possible that we could warm more slowly than expected, it’s also possible that we could warm much faster than expected. Deciding – for example – that we are likely to warm more slowly than expected would seem to be ignoring large swathes of evidence to suggest that this isn’t necessarily a likely outcome.
What got me interested, though, was that Judith said
@VariabilityBlog Temperatures could go either way. In the 21st century, decades of cooling should not be ruled out.
— Judith Curry (@curryja) May 26, 2014
to which I responded with
@curryja What? How is that possible without an asteroid strike or major volcanic eruption? Is radiative physics wrong? @VariabilityBlog
— There's Physics (@theresphysics) May 26, 2014
(yes, I should probably stop responding with terms like What?, although sometimes I really am incredulous). Judith’s response was
@theresphysics @VariabilityBlog major volc. erupt, solar effects, ocean circ. could all contribute to cooling. IPCC only focused on AGW
— Judith Curry (@curryja) May 26, 2014
So, here’s my issue. During the Maunder Minimum, Total Solar Irradiance was about 3.5 Wm-2 less than today. Dividing by 4 means that if we were to return to Maunder Minimum-like conditions Solar forcing would reduce by about 0.6 Wm-2. Such changes would typically take decades, so solar forcing might drop by 0.1 – 0.2 Wm-2 per decade. If we continue increasing our emissions, anthropogenic forcings could increase by as much as 0.5Wm-2 per decade. So, in the most extreme possible scenario, Solar variability could reduce the rate of increase by maybe 30%. So, it doesn’t seem possible for Solar variability to result in an external forcing that reduces with time, assuming we continue increasing our emissions. Given this, how can Solar variability produce decades of cooling?
As far as ocean cycles go, yes it does seem that ocean cycles can influence warming. However, it seems that they typically act to produce variability around the long-term trend. Bearing in mind that our emissions could increase anthropogenic forcings by around 0.5 Wm-2 per decade, if ocean cycles are to produces decades of cooling, they somehow have to act to take a system that is out of equilibrium, further from equilibrium. For there to be decades of cooling, the oceans would have to be absorbing all the excess energy – and more – while the energy imbalance continued to increase. This just seems thermodynamically impossible. So, how can ocean cycles produces decades of cooling?
To be fair, Twitter is a rubbish medium. I often say things I later regret, or don’t express myself as clearly as I should. Maybe Judith didn’t quite mean it the way it seems. On the other hand, maybe Judith does think that Solar variability or oceans cycles could contribute to decades of cooling. I think that this is physically implausible. However, given that we’re discussing science, this would seem to be something that could be discussed in more detail. Maybe Judith could actually explain what she means and how this could work. Provide some kind of actual mechanism and some real numbers. On the other hand, maybe Judith could look at the numbers and realise that it’s not possible, unless something completely unprecedented and unexpected were to happen.
As to the IPCC focusing on AGW only. Firstly, I don’t think that is strictly true. I’ve seen discussions of variability and other non-AGW influences in the IPCC documents. However, if it appears that way, maybe it’s because the evidence suggests that the dominant forcing in the coming decades is going to anthropogenic, not because the IPCC is somehow biased against other possibilities.
...and Then There's Physics 
Agree that decades of cooling caused by solar radiation or ocean circulation is implausible.
I am not sure what Curry is expecting the IPCC to do. I don’t think it is their role to speculate about what could happen if a major volcanic eruption occurred.
A doctor can tell you that if you keep smoking 20 a day you’ll on average reduce you life expectancy by 20 years for example. You could still walk out of the surgery and be hit by a car. Curry’s critiscm seems to be the equivalent of criticising a doctor for not taking into account road accident statistics when telling you your prognosis for smoking.
James,
Indeed. Something I had meant to add to the post is that the evidence suggests that the dominant factor that will determine changes in external forcing is our own emissions. Something completely unexpected, unpredictable and – possibly – unknown, could counteract that, but that’s completely beyond our control. We can, however, control our own emissions. So, arguing for some unknown mechanism that could lead to decades of cooling just seems scientifically unjustified, but also an extremely poor policy option. Wishful thinking is not, typically, the best course of action.
ATTP,
You present a value of about 3.5 W/m^2 for the Maunder minimum as it that would be a well established value. According to a rather recent paper of Feulner that’s not the case at all.
Earlier Judith Curry was explicit about the two-way nature of the uncertainty, but not that clearly any more. She presents in her recent post three alternatives for the dynamic behavior of the climate. The first is the main stream view, while the two others are dominated either by quasiperiodic oscillations or fully aperiodic climate shifts. What I don’t understand in that post is the smallness of the role of AGW in the latter two alternatives. Even assuming that the natural variability has been very important over the latest few decades, the importance of AGW is expected to grow and lead to a behavior intermediate between the alternative I and either one of the two others rather than purely to her alternative II or III.
She does say that AGW would be superimposed on the natural variability, but her further comments give very little role for that over several more decades to come. That would require a significantly lower TCR than proposed by Nic Lewis and others who argue for a low TCR.
Pekka,
Interesting, thanks for the link. From a quick read, it seems that there is some evidence that the TSI difference could have been much smaller, or as big as 5.8Wm-2. That would change things a little. If the difference could be that large, then the change in solar forcing could be as large as 1.5 Wm-2. Again, however, it would seem that such a change would still take decades. I guess, there is an outside chance that if such a large change is possible that it could become comparable to the change in anthropogenic forcings, and hence counteract that. However, the paper does conclude with
and also says,
So, I stand corrected on my choice of TSI difference, but I don’t think what one would conclude is wildly different.
Indeed, that would seem to be an issue and is probably another way of saying what I was saying here. If you want variability to completely counteract anthropogenic warming, the anthropogenic warming will have to be on the slow side.
Pekka, the linked paper calls a “TSI difference of 0.2–0.7 W m−2 as compared to the 2008/2009 solar minimum” an “an emerging consensus”, but describes two studies with a different result. It then compares the forcing implications of those estimates of those studies to the historical record over the last two thousand years. It finds an estimate that indicates zero difference between the Maunder Minimum and the 2008/09 minimum consistent with the temperature record, but the one showing a TSI difference of 5.8 W/m^2 to be largely inconsistent with that record.
Overall, based on that paper, Anders has greatly over estimated the potential effect of a new Maunder Minimum. Was that in fact the point you were trying to make? If so, it is not evident from your words.
Tom,
I thought I had picked up on that issue, but you’re right, the paper’s conclusions are that the more extreme difference is inconsistent with the record and that it is more likely that the difference was smaller.
If I was trying to do anything it was to show that for the Maunder Minimum-like conditions to have any appreciable effect, it would have to be extreme and – as you point out – be even more extreme than the Maunder Minimum was itself. Hence, it seems very unlikely – although, I may not have made that as obvious as I should have.
I didn’t mean to propose that a high solar forcing during the Maunder minimum would be likely. What I had more in mind is that all the value is not really known based on any direct reliable method. We cannot use an indirectly inferred value as justification in the way ATTP did as that’s actually a circular argument, when the inconsistency is used as basis for arguing against the highest values.
As a side remark I notice that circular arguments are very common in climate discussion. Very many values are inferred indirectly and it’s not unusual at all that someone picks the inferred value (B) and uses it to support another value (A) that was actually the starting point for determining (B).
One area where that happens often is the global energy balance where the balance at TOA, changes in OHC, and possibly other related quantities are discussed.
Pekka,
I wasn’t quite sure that I did this, and I’m not quite sure what you mean. The post wasn’t arguing against high Maunder Minimum values as such, it was trying to illustrate that even if we did go back to Maunder Minimum-like conditions, it’s unlikely to produce decades of cooling. I clearly did just pick a value for the TSI that I found online without checking that it was accepted/reasonable. I stand corrected in that regard, but the paper you link to seems to strengthen the basic argument, rather than weaken it.
Pekka,
If you mean that some people use the TOA imbalance, to infer the OHC without realising that the TOA imbalance is typically constrained using the OHC, then I agree. However, using the OHC and other system heat uptake rates to infer the energy imbalance, doesn’t – itself – seem circular.
In some cases fully circular inferences are made, TOA imbalance is a typical case. It’s more common to see mixed cases where a non-circular valid argument is complemented by circular arguments either to add details or to claim stronger evidence when the direct observations are not as accurate as one would like. This second kind of error is common in discussion of OHC as well.
It’s more generally true that knowledge on climate is plentiful but sparse. The total amount of observations is large but there are also gaps in knowledge everywhere. Combining the disjoint pieces of data is done using models – either explicit numerical models or less precisely defined mental models and narratives. This kind of situation leads very easily to circular arguments. That makes it also very difficult to judge the level of uncertainties allowing knowledgeable people end up in very different conclusions. While one person may feel subjectively that his estimates of the uncertainties are well justified she or he cannot prove that to another whose personal judgment differs.
Yes, that was my intention and to my surprise Curry acknowledges that the uncertainty can go both ways and even referred to an AGU talk of hers from 2010. Pretty alarmist stuff about the importance of the fat tails of the probability distribution for the climate sensitivity and impacts. (With fat tail the probability for extreme deviations only goes to zero very slowly. Combined with a strong increase of the damages for extreme deviations, this can make that the damages are determined by a single extremely extreme catastrophe).
And her fans acted as she had just refuted the IPCC, because she claimed the IPCC was too conservative and only considered the bulk of the climate sensitivity distribution. (Not sure if that is true, more people working on impacts know about fat tails. Maybe that work is less known. Scientists typically do not like talking about it in public, because it sounds rather alarmist. Except for Curry. My respects, hat tip!)
Apologies I tend to use a lot of medical analogies. Maybe the problem with being related to doctors. However, I think they are good. 🙂
I hope most people go to a doctor if they have a medical condition and trust modern medicine. Yet modern medicine is based on trials and research that give the doctors boundaries and probability distributions about how a patient with respond to drugs or how a condition will progress. Modern medicine cannot tell you exactly how an individual patient will respond. Our ‘model’ is always ‘wrong’. Yet no one refuses medical advice because the doctor cannot tell you how high your fever will be in week 3 or you might get the flu in 4 weeks.
Modern medicine cannot predict the unexpected or take into account every other condition you might develop in the future. I would consider CO2 to be the equivalent of a chronic condition and a volcanic eruption to be the equivalent of an acute condition. Chronic conditions don’t go away because you develop an acute condition. If you have cancer a skiing accident doesn’t stop the cancer. In the short term the priority will obviously be dealing with the acute condition but once you are past that the chronic condition remains. There may be a volcanic eruption and global temperatures may pause or decline for a decade but once that has past there will still be more CO2 in the atmosphere and the planet will eventually warm to the same equilibrium temperature had the volcanic eruption not occurred. The final equilibrium temperature from the rise in CO2 is independent of the natural variability on the path that gets us there.
In medicine there is rarely, if ever, a situation when having a chronic condition makes dealing with an acute condition easier or via verse. If you were unlucky enough to have a skiing accident having cancer at the same time doesn’t make things better! I think most people would think your chances of dealing with the trauma of a skiing accident were better without already being stressed from another illness. The media focuses a lot on temperatures because it’s an easy way to explain the problem to the layman. However, in this simplification we fail to get across the message that the real dangers of global warming is how the climate changes. A 2oC raise in temperatures by itself it not that significant. However, the melting of ice and region effects on rain patterns are far more serious problems. Yet they could happen without any change in average global temperature.
Should we get declining temperatures from a volcanic eruption, I think many people seem to assume this would “counter” AGW. That is not the case at all. The pattern of cooling from a volcanic eruption is not the opposite of the warming pattern from AGW. If you press a pattern into plastic from 1 direction and press a different pattern in from another direction. The result is not a flat piece of plastic but an even more distorted shape with areas of even higher stress. A volcanic eruption could result in more extreme local weather than if the same volcanic eruption had happened without AGW. (I define extreme weather as weather existing outside or near the limits of ‘normal’ distribution. So extreme might be a mildish winter in Siberia rather than hurricanes or tornadoes)
So I fail to see what comfort Curry is expecting us to take from an unexpected natural event occurring. It won’t make AGW go away and could well be made worse by AGW. Dealing with AGW first will make it easier to deal with the surprises.
Not exactly in defense of Judith’s argument (I agree that her attitude towards uncertainty is often very selective)….
==> “Dealing with AGW first will make it easier to deal with the surprises.”
My sense of her argument is that it is kind of the inverse of that argument. Something like this: The need to “adapt” to extreme weather due to natural variability (surprises) is more certain than the need to “mitigate” extreme weather that would result from the external forcing of ACO2. As I understand the argument, it also goes on to…. “Adapting” to natural weather extremes would also provide resilience to any form of extreme weather, and we don’t really know how to effectively “mitigate,” or at least we don’t know how to do so without deleterious economic outcomes.
The main problem that I have with that argument (if I got it right) is that very last part: As from what I’ve seen, it rests upon a poor recognition of the bi-directional uncertainty of economic outcomes.
Given what is well know about the cumulative effect of greenhouse forcings, when I read your post I couldn’t help thinking of this story:
“Some years ago I had a conversation with a layman about flying saucers – because I am scientific I know all about flying saucers! I said ‘I don’t think there are flying saucers’. So my antagonist said, ‘Is it impossible that there are flying saucers? Can you prove that it’s impossible?’ ‘No’, I said, ‘I can’t prove it’s impossible. It’s just very unlikely’.
At that he said, ‘You are very unscientific. If you can’t prove it impossible then how can you say that it’s unlikely?’ But that is the way that is scientific. It is scientific only to say what is more likely and what less likely, and not to be proving all the time the possible and impossible.”
Apologies for “Pulling a Feynman” (I wonder if someone will name a new law about the critical number of posts on a scientific topic before Richard Feynman is quoted)
Joshua, and additional problem with the “adaptation” argument is that much of it will be after the problems have already started, and that much of it actually depends on the accuracy of the regional impacts of climate change – which are much less predictable than the global changes.
For example, at present the Victorian desalination plant is on standby, right after completion, because there has been sufficient rainfall in the last few years, after many years of drought that was thought to be the new normal. If this recent rainfall period turns out to be the new climate normal, they will still spend about 18 billion dollar over the next 24.5 years for a facility that isn’t used, due to a deal with the construction consortium that contains a 1.8 million a day fee regardless of whether the water is needed. The cost will only be worth it when the climate in that region indeed will do what is expected (which is worse drought).
The JC tweet that we might see “decades of cooling” is ambiguous – did she mean that there will be periods of up to a decade when GAT cools slightly or did she mean ‘several consecutive decades of global cooling’?
The first interpretation is, as I understand it, not at all contentious. The second is probably unphysical nonsense.
She means decades of cooling; as in, 1940 to whatever: mid-century cooling.
And she thinks we’re on the brink of it right now.
ATTP,
Careful what you do with your time. From the transcript linked here:
http://rabett.blogspot.com/2014/02/like-lambs-to-slaughter.html
DR. CURRY:
[…]
You asked the questions of solar influences beyond TSI. This is a subject that intrigues me greatly. It’s sort of in the known/unknown category. All you can do is sort of speculate on ideas.
That might be cosmic rays, global electric circuit, magnetic field. We simply don’t know. But I wouldn’t be surprised if they are important.
And when I talked to people doing planetary atmospheres, a question that — why don’t you people pay attention to the magnetic field in planetary atmosphere? This is a big deal.
And we don’t really pay much attention to the magnetic field in context. So, there are things like this, questions that we haven’t really asked. So, I don’t know, but some very intriguing possibilities.
[…]
DR. BEASLEY: Judy, you talked about solar influences. And I thought that Bill nailed one of the influences, which is changes in the solar. It’s hard to understand how that would happen. I can really see that.
But then you mentioned a bunch of others that kind of surprised me, quite frankly. And so, for example, the magnetic field, I can’t resist picking that one. Do you have a physics notion of what —
DR. CURRY: Okay, this is known/unknown. Some people with publishing papers speculating.
DR. ROSNER: This is based on they are certain that there is an effect or they have a physical process in mind that actually would do something?
DR. CHRISTY: There is the cosmic —
DR. CURRY: Well, that is one example. I can’t recite all the arguments off the top of my head. But people are publishing papers that present some intriguing possibilities. These are obviously not in the mainstream. But we have only really started looking at these kind of topics.
If you are interested, I can send you a list of papers I have been recently. But this is known/unknown category.
Judith believes (believed?) that warming could be as high as 10C for a doubling of CO2:
“That there is a 33% probability that that actual sensitivity could be higher or lower than my bounds. To bound at a 90% level, I would say the bounds need to be 0-10C.” – http://judithcurry.com/2011/02/26/agreeing/#comment-49648
FWIW, if I recall one of Mike Lookwood’s recent talks correctly, based on the latest evidence it is reasonable to assume that we’ve probably seen Maunder Minimum conditions (with respect to solar activity) during the last solar minimum (2008-2010). Just saying …
BBD: My understanding of the simulation data is that indeed decades of cooling could occur… but again… that could be confusing. Global surface temperatures can go down for decades, that doesn’t mean Global Warming has stopped or declined, just surface temperatures with the exclusion of ocean heat content.
You argue against Straw lady Judith Curry. There can be no discussion with JC out of your numbers for antropogenetic forcing, since for her this is not settled science. If you’ve read what she wrote, her opinion is that these figures are too high. Perhaps you should acquaint yourselves with what she has said. All these AGW mantras don`t help for understanding atmosphere. Neither do denial of natural variations. Oceans are driving climate variations more than atmosphere in the short run. And what are the role of feedbacks in the great energy current. Yor numbers imply that you know it.
Nobodyknows,
Very droll 🙂
AoM,
I think I see what you’re getting at, but my issue is that if we continue increasing our the radiative forcing will increase. If we were to undergo decades of cooling then we’d have a system that was out of energy equilibrium that somehow was in a state where it moved itself even further out of equilibrium. That seems thermodynamically implausible.
Anders, you are correct. When we talk about global warming we are talking about Global Heat Content. Often however Pseudo Skeptics will (intentionally?) confuse global heat content with surface temperatures, as though the problem some how disappears in a poof of logic.
By the way… I worked on a military communication system some years ago. (Its on the Dash of the Hummer in Iron Man 1.) Early in the design process, heat from the processor was deemed a concern, so some bright spark decided that we could use Peltier modules to transfer the heat to the casing. (http://en.wikipedia.org/wiki/Thermoelectric_cooling) Then they noticed that the case was getting hot, and oh by the way, the it was heating up the processor. A different solution was found… (You can’t just make this stuff up you know.)
Marco –
==> “Joshua, and additional problem with the “adaptation” argument is that much of it will be after the problems have already started, and that much of it actually depends on the accuracy of the regional impacts of climate change – which are much less predictable than the global changes.”
Yes. This is true. Additionally, a problem with the “adaptation” argument is that mitigation could make adaptation much more efficacious.
Layzej –
==> “Judith believes (believed?) that warming could be as high as 10C for a doubling of CO2:”
Not only that, but consider this opinion of hers from not all that long ago:
What an alarmist!!1!!!1!!1
Joshua,
Don’t forget that Judith Curry endorsed Storm World;
http://www.desmogblog.com/judith-curry-was-me-she-was-against-me
For decades of cooling in the surface air temperature ( a dip in the GAT), there would have to be an enormous amount of heat sequestered into the oceans, and the ocean surface would have to have a large expanse of exceedingly cold water continuously upwelled. I don’t think that situation can happen. It certainly has not happened in the 21st Century as the have been a few record warmest years recorded.
So from where is the extra cold going to come?
AOM – What a long, strange trip it’s been.
AoM
I’m with ATTP on this. Several consecutive decades of cooling in a system already out of equilibrium and which is also under a sustained and increasing forcing… Nope.
Surface air temperature wibbles modulated by variability in the rate of ocean heat uptake… yes.
I think this paper by Li (IPCC lead author) et al is relevant
http://onlinelibrary.wiley.com/doi/10.1002/2013GL057877/pdf
Abstract
[1]The twentieth century Northern Hemisphere mean surface temperature (NHT) is
characterized by a multidecadal warming–cooling–warming pattern followed by a flat trend
since about 2000 (recent warming hiatus). Here we demonstrate that the North Atlantic
Oscillation (NAO) is implicated as a useful predictor of NHT multidecadal variability.
Observational analysis shows that the NAO leads both the detrended NHT and oceanic
Atlantic Multidecadal Oscillation (AMO) by 15–20 years. Theoretical analysis illuminates
that the NAO precedes NHT multidecadal variability through its delayed effect on the AMO
due to the large thermal inertia associated with slow oceanic processes. A NAO-based linear
model is therefore established to predict the NHT, which gives an excellent hindcast for NHT
in 1971–2011 with the recent flat trend well predicted. NHT in 2012–2027 is predicted to fall
slightly over the next decades, due to the recent NAO weakening that temporarily offsets the
anthropogenically induced warming.
Well, we shall see.
Everybody seems now so eager to emphasize OHC over surface temperatures. Noting this figure 4 from the paper of Lyman and Johnson (JClimate 24, p. 1945-1957 (2014)) I’m not so sure whether the availability, coverage and quality of data makes that such an obvious conclusion.
Maybe the term “cooling” is used in the way WUWT and Co. use it: for a warming rate that is below average, like we had since 1998.
Pekka
I think perhaps it is the rate of increase in OHC (0 – 2000m) over recent years (ARGO) that some people are keen to emphasise as providing a physical explanation for the slowdown in the rate of surface warming.
Sorry – missed link:
OHC 0 – 2000m layer
BBD,
I have still my doubts on the justification of that approach. It’s only 0-2000 m, there are still some limitations in the areal coverage, and I would not be surprised at all by some future variability in that data that contradicts the role given on that data.
That does not mean that I would be doubtful on climate science, but I have a strong feeling that many of the arguments used are not valid even when the conclusions are right. People continue to make with conviction unneeded statements that will turn out to be wrong. That does not add to the credibility of the science or its proponents.
Surface temperatures were used without serious reservations until “the hiatus” came out. Roger Pielke Sr was advocating OHC, others resisted largely because based on lack of data. ARGO has helped a little, but only a little so far. Choosing in hindsight what argument to use is a bad practice. It may be called cherry picking of a kind.
==> ” People continue to make with conviction unneeded statements that will turn out to be wrong. That does not add to the credibility of the science or its proponents.”
A case in point – from WUWT via Hotwhopper:
——————
———————————
Note how the WMO speaks of “radiative forcing,” and Anthony in a typically non-sequiturial [I like making up words ] fashion, speaks of “the temperature data” with chart w/ an unlabeled X axis.
Although the evidence is not yet conclusive, it does appear that the 17-year slowdown in warming in the face of increasing GHG forcing reflects, at least in part, a vertical redistribution of ocean heat. An obvious question is how long can this continue, and what mechanism would perpetuate the process? It seems to me that if the current pattern of heat redistribution remains unchanged, surface warming should resume at a rate commensurate with forcing. For the surface temperature to remain relatively unchanged rather than warming, the heat must become more severely redistributed – i.e., heat would have to flow into the deep ocean, warming it more and more, while surface temperatures remained flat, so that the gradient between surface and the depths would continue to decline. What mechanism could keep this going for years or decades despite the presence of convective processes and vertical currents that have maintained the gradient at its level of the past? I don’t suggest it’s impossible, but it would seem very unlikely in the absence of evidence for major observable changes in the forces operating on the ocean, including wind patterns, which themselves would require a mechanism. A resumption of more normal warming patterns within less than several years would appear more likely. I would add that if this reasoning is correct, one needn’t postulate that heat in the deep ocean must “come out” soon for warming to resume – it merely need stay where it is. Indeed, if “coming out” happened, one might expect a supernormal level of warming. I’ll be interested on evidence bearing on these points.
Fred,
The warming of deep ocean is very slow assuming that a large part of the ocean volume takes part in that. Therefore the reduction in the temperature differential remains small for a long time. Stated in another way, a very small change in the surface temperature is enough to keep the difference constant. The scale we have for changes in surface temperature is tenths of degress, the scale for deep ocean is hundredths or perhaps only millikelvins.
What’s a much more important factor is the strengthening of the forcing. With a constant surface temperature we have no Planck feedback and maintaining that state gets rapidly impossible. That’s the reason for expecting that the warming will resume and its rate will get relatively high.
I’m perfectly ready to present this kind of predictions as subjective expectations and present my arguments in their support. What I have protested against in some of my above comments is selective use of observational data and presenting that cherry picked selection as scientific evidence. This practice is too common. Some scientists behave like that (most don’t), Many climate blogs (or commenters at those blogs) behave very badly like that. The scientific skepticism is really easy to forget, when a result appears supportive of own wishes or prejudices.
Pekka
That’s a lot of ocean and a lot of energy.
The sampling density is higher for 0 – 1750m than 1750 – 2000m:
ARGO 0 – 1750m 2005
ARGO 0 – 1750m 2009
ARGO 0 – 1750m 2013
Well, I think I would be, but we can differ on this.
And it may be called the rough edge of scientific understanding, which of course it is.
Pekka,
Agreed, that’s essentially the point I was trying to make in the post. Similarly, it’s hard to see a plausible scenario in which the forcing increases while surface temperatures decrease.
BBD,
In some of the OHC data series we have seen strong oscillations rather recently. If that data is correct, all the warming of the ARGO period could easily be reversed for a while.
ARGO period is too short for drawing any strong conclusions from that amount of warming that has occurred. It may be representative of the future, but equally well it may not. There isn’t enough empirical evidence or good enough theoretical understanding of ocean dynamics to really tell.
Pekka – Thanks for your comment. We may be saying similar things. If forcing increases and the Planck feedback does not, the planetary imbalance must increase and this should be reflected in an increase in OHC at depth but not the surface. You state that maintaining that state becomes impossible. I agree, but the question is why.
Fred,
There’s probably hand-waving arguments as to why this is impossible, but it would nice to see something a bit more rigorous. Right now, I don’t quite now where to start.
In a simple model we might have three moving parts: OHC dominated by deep ocean, surface temperature that applies both to surface ocean (70 m seems to be a typical maximum depth for that) and the atmosphere, and atmospheric variability meaning mainly albedo that might vary depending on the state of the ocean (location of warm and cool areas).
In that picture the state of the ocean affects both the heat flux into the deep ocean and the albedo. Both may contribute significantly and both are something that simple models cannot really say anything about. To me this seems to be a problem that requires AOGCMs that describe well both atmospheric dynamics and cloudiness, i.e. more than the best present day models can do.
I cannot see, how any simple approach would be of much value, if the real issues are those that I propose.
Pekka,
I agree that there doesn’t seem to be a simple way to demonstrate this. I would argue, though, that a system out of equilibrium is unlikely to evolve in such as a way as to move further from equilibrium. Given that the alternative view seems to be “we don’t know, therefore maybe”, a simple argument about energy and equilibrium seems quite compelling.
The long term trend seems clear, although its strength is not well known, but the variability may provide surprises. I don’t believe in decades, but 5-10 more years of little surface warming might be possible.
I’m just speculating further on what I see as an eventual resistance to the continuing deposition of heat into the deep ocean with little change in surface temperature. It’s true that the ocean is a very large heat sink, but it’s not actually an infinite one. While average warming of the deep ocean may be very small, it’s also likely to be inhomogeneous, and areas where there is active downward transport may exhibit larger temperature changes, and hence more “resistance” to further warming, than the deep ocean as a whole. Obviously, this is a process that requires data more than speculation, but it’s worth looking into. It’s one of those circumstances where intuitively, we expect, often correctly, that an unusual process can’t continue forever, without yet knowing the exact mechanism that limits it (like perpetual motion machines where the Second Law violation is so subtle it’s hard to identify).
Timescales really matter..
Ex: it is very easy to get a cooling trend* over a year, via a big volcano.
Ex: every time we switch into La Nina, there can be a cooling trend for a few years ending then.
Ex: any time there’s a sequence of La Ninas, there can be a cooling trend for a while.
The escalator is a nice representation.
But what does “decades of cooling” actually mean, mathematically?
a) Does it mean regression lines, or drawing lines between endpoints (hope not)?
b) Does it mean that there will be at least two decades this century where there is a 10-year cooling trend?
c) Does it mean that there will be at least one period where there is a cooling trend across at least 20 years?
For a really quick graph, see NASA GISTEMP Land-Ocean.
Stick that data in Excel, and simply compute the SLOPE to ending year, for 10, 15, 20, 25-year intervals. That converts hard-to-eyeball jiggly diagonals into rates of change, by interval, for each year, which makes it hard to cherry-pick specific dates.
Regression slopes chart does this.
It is possible to have a 10-year cooling trend (barely) if you pick 2011 or 2012, but since 1980, 10-year trends average about 0.017C/yr, while jiggling between 0 and .03.
There are no 15-, 20- or 25- year cooling trends since the mid-1970s, and most of those slopes have been between .01 and .02C/yr.
None of this is any great surprise, and obvious why one wants 20+ years for climate issues.
Think circulation changes, Fred.
Agreed that Twitter is ungood for conducting scientific conversations.
James Westwood says: (May 27, 2014 at 11:20 am) “I tend to use a lot of medical analogies… I think they are good”
Naturally! I think the same of my analogies 🙂 but in this case there’s a HUGE difference:
Doctors practice their arts hundreds of times, multiplied by thousands of doctors. That invokes *repeatability*, a thing largely missing from climate science.
A more correct analogy would be an extremely complex, life-threatening medical procedure that had never been done before but only simulated in a computer.
If you believe it is certain the patient will die without the attempt being made, then it is not worse to at least try the procedure.
But if the disease itself has never been experienced, and the procedure never been tried, how can anyone be sure that the patient will die?
[Mod edit: this bit is likely to provoke, so removed it]
And Then There’s Physics says: (May 27, 2014 at 7:49 am) “We can, however, control our own emissions.”
Indeed I do as much as is practical — efficient automobile and less traveling, CFL and LED illumination, timers on fans, stuff like that. But when you say “we” I suspect that what you have in mind is not me making my own decisions. I’m pretty sure that this nation cannot just stop “emitting”.
Michael 2:
“A more correct analogy would be an extremely complex, life-threatening medical procedure that had never been done before but only simulated in a computer.”
Climate has never changed in the past and has only been simulated in a computer? We have no paleo evidence to consider, not at all? Evidence for the PETM is just … a computer simulation?
Or perhaps your analogy isn’t very good after all.
Hi,
I have a newbie question: If there is no atmospheric temperature increase and there is no SST increase but only OHC increase then is the water vapor feedback still happening and still calculated? I understand that the water vapor feedback happens only when the air temperature increases and as such it shouldn’t happen unless there is an increase in the surface temperatures. If this is the case, then as long as the heat goes into the oceans the ECS should be only what is given by the CO2 which, if I understand correctly it should be aprox 1.2 deg per doubling. I am pretty puzzled about this.
Thank you!
Mircea
Mircea,
You’re right that if surface temperatures remain fixed, then the water vapour feedback doesn’t operate. You’re suggesting that that would imply an ECS associated only with doubling CO2. The problem is that when the temperatures do start to rise, water vapour feedback will start to operate and the ECS will exceed 1.2oC.
Michael 2
I wasn’t really meaning anything specific. What I was getting at was that we can’t control volcanoes, the Sun, ocean cycles. However, we do control the emissions. That’s true irrespective of economic arguments about how our emissions should evolve in the future.
Models: I strongly recommend Steve Easterbrook’s TEDx talk on modeling.
One more time: we don’t need supercomputer models to get good approximations of temperature rise as function of emissions. Arrhenius did OK 100+ years ago with pencil and paper, and we also have a lot more paleo data now.
Mircea and ATTP,
The question is relevant and the answer of ATTP is right, but another point is that the imbalance from the forcing is only what CO2 produces directly without any amplification by feedbacks. There’s certainly some natural variability also in the energy balance. In comparison of that variability with CO2 forcing the contributions from feedbacks are also absent, when surface temperatures do not change.
There are, however, significant changes in the surface temperatures of some areas, and their influence on the regional energy balances is actually the most likely driver of natural variability in the global energy balance. The mechanism is exactly that of feedbacks. Cancellation of these changes in average surface temperature is not likely to lead to cancellation in the total feedback. This results in a significant uncertainty for the actual energy imbalance of the Earth system.
John,
The knowledge Arrhenius had available as starting point of his analysis was so lacking that it must be considered just good luck that he got results that agree quantitatively so well with present understanding. His sizable errors happened to largely cancel each other.
Hulburt and Plass got similarly lucky. One might even be able to say the same for Manabe and Wetherald.
Manabe and Wetherald were, however, the first, whose basic picture of the atmosphere was close to present understanding. That’s at least, how I see the history.
I have some memory of Eddington’s famous confirmation of GR also actually having large errors and the result being “correct” partly by chance. I can’t find any confirmation of that, but I think there was some similar issue with that.
As another poster has commented it is doubtful that JC accepts the mainstream values for the energy imbalance. I thought they were securely derived from the radiative transfer physics, but perhaps the unknowns gremlins and uncertainty monster can get everywhere.
If the increased CO2 really adds energy to the surface as calculated, the way to minimise any surface temperature rise is to use it to warm water because of its large thermal capacity. A lot of Joules can also be lost without a temperature change by driving the phase change of water.
So melt all the ice, dump that cold fresh water on top of warmer dense saline. Invoke (handwaving?) the thermohaline circulation process and dynamic ocean currents to cause a reduction in the deep ocean thermal gradient. Maximal absorption of Joules with minimal temperature increase. This is of course nonsense, or at least a big unknown uncertainty…..
OHC may be poorly measured by the ARGO system and the duration of the data is too short. But there is another clear indicator of OHC, sea level rise. Thermal expansion is a factor in that, as is the phase change of land ice. Increased rainfall can shift some of the sea level rise onto the land, at least briefly, but rising sea levels and increased rainfall could offset a lot of surface temperature rise by sequestering the Joules into deep water. I think modeling has been done of pure water-worlds. I am not sure they resist significant warming, or have a lower TCR/ECS than ocean/land surfaces.
All of this is just playing with uncertainty, and the ‘unknowns’. The suspicion is that the intended audience is not the mainstream science community which will pick up on these wonderful novel concepts, but the ideologically dogmatic that will welcome sustenance for their motivated reasoning. They are the obverse of the claim that given a really extreme set of circumstances AGW could lead to the oceans boiling. It is barely physicaly possible, never mind likely, but plays well with alarmists.
The claim that ‘some unknown’ factors will, with marginal physical credibility and high improbability lead to AGW resulting in little or no actual warming, (just rising seas) plays well with the denialists.
Climate sensitivity is nothing more than an estimate (a guess). If climate sensitivity turns out to be a lot lower than expected, then that would explain some of the missing heat (it’s just not there) and would also make a decade or more of cooling a more plausible scenario. Even without cooling, if the atmospheric temperature remains flat for another decade… climate sensitivity will still have to be re-evaluated.
Anders –
Don’t know if you’ve seen this, but if you haven’t I’m sure that you’ll get a kick out of it.
http://andrewgelman.com/2014/05/27/whole-fleet-gremlins-looking-carefully-richard-tols-twice-corrected-paper-economic-effects-climate-change/
Richard’s comments peg 11 on the unintentional irony scale. My favorites are when he says that considered criticism of his analysis is “bitching,” and suggests that others take the data and work out an analysis for themselves…
Skeptical,
I have a feeling that you’re rather conflating Transient and Equilibrium climate sensitivity.
Joshua,
I have been following that. Very interesting. For some reason the word “comeuppance” keeps springing to mind.
off topic but just saw the years of living dangerously episode with Rick Joyner and I was screaming at Kathryn Hayhoe to give him Mashey’s list of questions. Absolutely maddening that people are expected to be reasonable in the face of such unreason.
Anders,
You said, in a previous comment; “I would argue, though, that a system out of equilibrium is unlikely to evolve in such as a way as to move further from equilibrium.”
Therefore, the response to the Transient climate sensitivity should not diminish if the forcing is moving us away from equilibrium.
Skeptical,
I don’t really follow your argument. I was simply suggesting the following : the way the planet maintains an energy balance is through the surface temperature. If we are out of energy balance, we would expect the surface temperatures to change so as to retain energy balance. All I was suggesting was that it’s very difficult to see how a process could operate in which we move further from energy balance (i.e., how we can have decades of cooling while also having an ever increasing energy excess). I’m not quite sure what this has to do, specifically, with the Transient sensitivity.
> Climate sensitivity is nothing more than an estimate (a guess).
And your point is?
According to some, science is nothing more than a collection of guesses like that, and another collection of guesses that turned out to be wrong.
Some call these two kinds of guesses conjectures and refutations.
Anders,
The increasing excess energy is calculated, not measured. My argument is that if climate sensitivity is lower than estimated, then there is actually less excess energy than predicted. The whole premise that the planet cannot cool is based on a high climate sensitivity to CO2. If you give less weight to CO2 Transient sensitivity and more weight to natural variability, then a decade or more of cooling becomes an option.
Assuming climate equilibrium is even plausible, doesn’t your assertion that cooling takes climate further out of equilibrium presuppose that a hypothetical equilibrium state is warmer than now? What if we approached equilibrium in the 1900’s and are there now?
Chic,
Equilibrium is simply a state in which we recieve as much energy as we lose. We currently have evidence for an energy imbalance – we’re receiving about 0.5 Wm-2 more than we lose. The only way (if nothing else changes) to return to equilibrium is for surface temperatures to rise. If we continue to increase our emissions, then the imbalance will grow if surface temperatures don’t rise. Therefore if our emissions increase, the Sun doesn’t do anything completely unprecedented, we don’t have a major volcanic eruption, and we aren’t hit by an asteroid, if our surface temperatures were to drop, we’d be moving the system further from equilibrium.
Oh dear:
Please read this and have a careful think:
Thanks for posting the pointer to view of the whole elephant, BBD. Further thoughts:
Fans of a long-term hiatus should stop and actually consider ocean circulation. We only have the one warm pool, and it has known oscillatory behavior (ENSO). The other big feature is the Antarctic Circumpolar Current, the key role of which is obvious from looking at a map of THC. The only possible place to put significant added ocean heat is deep down, but as it happens most of the heat that gets there is in the form of Antarctic Bottom Water, courtesy of the ACC, and moves north verrry slowly (as measured), so slowly that significant decadal oscillatory behavior isn’t going to happen. So this is the problem the Stadium Wave runs into: No plausible physical mechanism because there’s literally no place to fit one, or to put it another way, if there is some sort of ENSO-like oscillatory behavior globally (maybe), it can’t operate to slow surface warming for long. One can then try to invoke some sort of cloudiness increase due to current changes, but at that point we’re basically in Lindzen hand-waving territory. The bow on the package is that no such effect is apparent in ice or sediment cores, noting the failed effort by Gerard Bond to find one.
What convinced me to be on the lookout for a relatively quick response to anthropogenic warming was the Naish et al. sediment core results finding rapid oscillations of the WAIS during the late Pliocene and early Pleistocene, synchronized with *weak* changes in orbital forcing. (This is why I expected the recent WAIS tipping point results, although of course recent obs were also pointing in that direction.) Clearly this is not a system that fools around when it gets a push, nor did anything operate to interfere significantly with those glacial cycles nothwithstanding the weak forcing that drove them.
Finally, when discussing climate sensitivity, IMO we should start with the changes already observed, particularly including the expansion of the tropics and the associated current changes, which among other things are already melting the ice at both ends of the planet, and note that the GCMs were (and remain) behind the curve on these changes. That being the case, and given that expansion of the tropics is a continuing process, why would we expect projected effects for the decades ahead to not be similarly over-conservative?
ATTP,
“We currently have evidence for an energy imbalance – we’re receiving about 0.5 Wm-2 more than we lose.”
If surface temperatures were actually rising to alleviate an imbalance, then I could see your argument. Without significant temperature change in the atmosphere and questionable evidence of ocean warming, I have to ask where the evidence for 0.5 W/m2 imbalance is and +/- what?
Chic,
Temperatures are rising (Cowtan & Way 2014). OHC data also indicates that it is increasing (Lyman & Johnson 2014). If you want to argue otherwise, you’re welcome to do so with suitable evidence. As for +/- the evidence I’ve seen suggests it is probably somewhere between 0.4 and 0.6 Wm-2.
Chic, to be consistent you need to respond to the next “warming surge” in the same way. I look forward to that!
“Without significant temperature change in the atmosphere and questionable evidence of ocean warming”
Ah, homework and the not doing thereof.
Pekka,
It’s only 0-2000 m, there are still some limitations in the areal coverage
An interesting little finding which came to my attention recently: masking altimeter sea level data to only include cells with ARGO coverage results in an SLR average trend about 20% smaller than the full field average over the ARGO period. In other words ARGO areal coverage is biased (or can be), and over this recent period is biased towards indicating smaller steric SLR.
The main culprit appears to be the Indonesian region, in which ARGO floats are largely absent. Currently a discussion paper, von Schuckmann et al. 2013 finds that masking out just the Indonesian region results in a 20% reduction in SLR.
If we assume the difference is entirely a function of steric sea level variability and that ocean mass change has contributed to about half the observed SLR over this period (similar to a number of estimates) the finding suggests ARGO measurements have missed about 40% of global contributions to steric SLR. It’s unlikely all of the difference is due to temperature/OHC changes in uncovered regions. Salinity probably plays a significant role.
Thanks for that, Paul. It’s that ole debil warm pool again, it seems.
Although, the response to comments and revision was seven months ago and the paper is still not final? Possibly it was superceded by this?
Here is some homework for Chic Bowdrie. For tomorrow’s test please read the paper by Trenberth et al. on Earth’s Energy Imbalance
Paul S,
I have no personal opinion on the direction of potential biases in various data sets, I’m just generally skeptical on all scientific results that are too recent for having been scrutinized thoroughly enough by many groups. You point to one paper that indicates one potential bias. I would be surprised if that’s the last significant finding related to ARGO data. Rather I would expect that several non-negligible corrections that affect the data in both directions are still to come. There’s no sign yet that the understanding of OHC dynamics would have reached a stable state, where all future corrections are only minor adjustments of the order of stated error narrow error ranges in the earlier data.
What I consider important is being able at the same time to recognize all actual uncertainties, and to use the data without the attitude that the uncertainties make it useless for policy relevant conclusions. In the present discussion I see signs both of downplaying real uncertainties and of declaring a far too large or erroneously weighted role for an “uncertainty monster”.
Some people have complained that I make the issues too difficult to everyone, But in my view they are that difficult without any making from my part. Pretending that a complex issue is not that complex restricts own learning and may backfire when used as basis for communication.
The article of Trenberth, Fasullo, and Balmaseda is open access also in its final published form
http://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-13-00294.1
Follow up questions for ATTP, Steve Bloom, and Ian Forrester:
Stephens et al. 2013 estimate energy imbalance as 0.6 +/- 0.4 W/m2. How do they get that accuracy or precision from numbers for outgoing radiation such as 100.0 +/- 2 for SW and 239.7 +/- 3.3 for LW. Error propagation generally leads to more not less error.
With regard to OHC, are you prepared to make the case that the alleged increase in ocean heat content is sufficiently accurate to translate into a forcing significantly different than zero?
Chic,
Yes, the data is not consistent (at high significance) with a change in radiative forcing that is zero.
On a related note,
I believe that the uncertainty in the energy imbalance is constrained by the OHC data, so the uncertainty isn’t determined by propagating the errors in the other fluxes. This is because the largest heat sink is the oceans and so since the change in OHC is known with higher accuracy than other measurements associated with energy fluxes, it makes sense to use it to constrain the range of the energy imbalance.
Chic and ATTP,
The new paper of Trenberth et al mentioned above is really useful for understanding these questions. While it explains a lot it tells also that there’s still quite a lot to learn in the details and to confirm more solidly in what seems to be understood presently.
Pekka,
Sure, but that’s almost always true. Unless I misunderstand the OHC data, I don’t believe that it is consistent with no energy imbalance.
dhogaza says: (May 28, 2014 at 5:24 am) “Climate has never changed in the past and has only been simulated in a computer? We have no paleo evidence to consider, not at all? Evidence for the PETM is just … a computer simulation?”
Yes, as you say, comprehension of past climate changes exists inside computers. What is real is tree rings and ice cores (among other things) that can be assumed to be proxies for temperature (and of course other things the relative proportions of which are not obvious).
With the aid of a computer these “proxies” turn into temperatures. But the temperature cannot be validated. It is and will always be a computer simulation.
Now as to the applicability to doctoring — we come full circle to my initial assertion which remains unchallenged. A disease which has never been SEEN before (not by you, by me or any living doctor), and isn’t even surely a disease (but it might be), is to be treated in a way that has never been tried by anyone and which, like radiation treatment or chemotherapy has KNOWN serious side effects.
Yes, admit it, more than most readers here you are indeed willing to inflict known serious side effects to cure something you believe is a disease and the cure has never before been tried anywhere. It’s a gamble. Spin the wheel and hope for the best I suppose.
Michael 2,
I don’t really encourage people to challenge others to accept some characterisation. Not a great way to encourage dialogue. Although we can’t know the impacts of our possible policy options, we can try to understand. Another gamble is to hope that climate sensitivity will be low, when there is evidence to suggest that it might not be.
ATTP,
“I believe that the uncertainty in the energy imbalance is constrained by the OHC data….”
This seems circular argumentation to me. IOW, OHC data indicate there should be an energy imbalance, therefore outgoing radiation must be less than incoming. Where are the measurements showing outgoing radiation errors less than 1%?
Pekka, I failed to find anything in the Trenberth et al. paper that justifies any non-zero energy imbalance. Where am I wrong?
Chic,
To a certain extent it is, in that the main reason we are confident of an energy imbalance is because of the OHC data. The rise in OHC data (plus the reduction in ice, increase in surface temperatures) is evidence – by itself – of an energy imbalance. The satellite measurements are consistent with this but, by themselves, would – I think – not be accurate enough to determine the imbalance without a large uncertainty. The point, though, is that we don’t need to satellite measurements to be confident that we’re not in energy balance.
ATTP,
Without confirmation that energy imbalance predicted by OHC is confirmed by the difference between incoming and outgoing radiation, there is insufficient confidence. There’s just too much ocean which has not been measured and no good reason why atmospheric temperatures stagnate while ocean temperatures increase.
Chic,
If the heat content of the Earth system is growing, then we can conclude that a net energy flux exists. A net energy flux is synonymous with energy imbalance.
That’s the whole argument, and that’s a solid argument.
ATTP,
I certainly didn’t mean that the paper would tell that no imbalance exists. What i meant by the uncertainties discussed concerns the completeness and accuracy of knowledge of the OHC data. A reanalysis added to the knowledge base, but could reach full consistency. We know that different atmospheric reanalyses give significantly different results, and that ll of them have some open issues. It’s likely that the state of ocean reanalysis is not as advanced as that of the atmosphere.
I think it’s a good paper, but I really don’t think that future understanding will agree quantitatively with its findings. Perhaps another ocean reanalysis will be done in a couple of years by some other group than that used in the paper. Then some other scientists will use that reanalysis for a similar work as Trenberth et al did here. I would expect that the results of that deviate significantly (tens of percents, on some points perhaps by a factor of two) from the present results.
Right now we have values that can be considered best existing estimates, but still unconfirmed and likely to get modified.
.. but could not reach full consistency.
Pekka,
“If the heat content of the Earth system is growing, then we can conclude that a net energy flux exists. A net energy flux is synonymous with energy imbalance.”
That’s more of a truism than an argument. The argument is whether or not the heat content of the planet IS growing. Ocean heat content is only one factor and one not completely accounted for, as you have alluded to previously.
Chic,
The heat content of the oceans is dominant. We’re also losing ice and surface/atmospheric temperatures continue to rise (although more slowly than expected). The energy of the climate system is increasing. There is virtually no doubt about this. That’s fundamentally what global warming means. Further, the evidence overwhelmingly suggests that it is a consequence of anthropogenic emissions. If you want to convince me otherwise, feel free to try, but you’re going to have to actually do some work and provide some evidence.
All other components of the Earth energy content change so little that OHC dominates with high certainty. While the uncertainties in the determination of OHC are large they are not large enough to make the increase of OHC questionable to a significant degree over periods of decades.
Mistaking the trees for the forest may also backfire when used as basis for communication, Pekka.
Maybe it would be helpful for you to consider this whole “hiatus” business as an exercise in “normal politics” (formerly “post-normal science”; see my comment in the next thread). It was politicians, not scientists, who decided it might have policy significance. So now scientists are defending the science (and society) by focusing on the lack of significance of the perceived “hiatus” relative to the very dangerous big picture, and as someone not in the field nitpicking their efforts you’re being helpful… how, and to whom?
Also relating to my reply above to the comment from Paul S, here’s a related new paper by more or less the same group.
look at the Csiro plot for 0-to-700 meters Lol, probably right.
In two earlier comments, I suggested a possible mechanism that might eventually limit or reverse the vertical redistribution of ocean heat downward that appears to be involved in the recent slowdown of surface warming despite continued ocean heat uptake. Specifically, I suggested that warming of ocean waters at depth would serve as a brake to continuing redistribution, particularly in areas where deep warming rates exceeded the average. Steve Bloom provided a more specific example relevant to the process, involving abyssal water in the Antarctic. The following article (a meeting abstract) appears to provide some substantiation, although it doesn’t specifically address the surface temperature component – Abyssal Warming.
That’s the correct research thread, Fred. See P&J’s most recent paper covering much of the same material; it also has citing papers that look interesting.
Of note, they say:
This sort of thing is why I consider model projections for 2100, or indeed climate sensitivity estimates based on current models, to be severely low-balled.
To repeat what I said above, I don’t see any room here for a braking process in the near term given that the older abyssal waters moving north are colder. Rather, acceleration seems inevitable. Presumably there’s some limit to that, but as noted by the authors there’s no present way of establishing what that might be.
Steve – Thanks. You may be right about the timescale,,but for how long do you think the surface can transfer heat sufficient to warm bottom waters at about 0.03 C/decade if the surface itself hardly exceeds that or even falls below that rate? Some of that deep warming occurred when the surface was warming faster than recently and therefore faster than the deep water – e.g., in the 1980’s and 1990’s. I’m not suggesting I know the answer, but I wouldn’t be surprised to see the rate of bottom water warming slow down.
Fred, I’m not sure I quite have a grasp on the details of the mechanism, but the paper I linked makes it clear that what’s driving the process isn’t a temperature differential but rather salinity changes due to the increased flux of fresh water from melting glaciers.
I’m sure you recall the recent papers discussing how the increase in westerly winds driven by poleward expansion of the Hadley circulation (in turn ultimately driven by… us) has been driving warmer water (IIRC from intermediate depths) up onto the continental shelf where it undermines the glaciers and produces the aforesaid fresh water (and enhances sea ice formation, but that’s another story).
Given all this, I would be surprised to see the AABW warming slow down. To the contrary, I would expect it to scale up with increasing melt.
But is the amount of heat taken into the abyss by the ACC, even it it accelerates, capable of flattening the SAT with ACO2 at 400 ppm plus? I don’t see how it could do that.
The AABW doesn’t seem to be a big factor in SAT, as yet anyway. Also it takes a lot of heat to melt that ice, so that may be the larger factor. But even if it increases, this mechanism seems like it wouldn’t be much competition for the wind-driven process (in the mid-Pacific) described by England et al. a few months ago. (IANAS.)
Just now getting caught up on new papers and I see in Nature (title/abstract)::
Hmm, that mechanism sounds kind of familiar.
The change in the heat content of deep ocean is the net sum of changes in all mechanisms that transfer heat either in to the deep ocean or out. Changes in the temperature or strength in any of these components leads to a change in the warming of deep ocean.
Formation of abyssal water is one of these processes and the current of old water out that allows the new water flow in is another. In other areas we have turbulent mixing related to tidal flows. How many mechanisms have been identified in total, I have no idea about.
Intuitively we concentrate easily on one or two of the mechanisms and forget the rest. That may happen even when the two mechanisms are linked.
Right. IIRC all of the current flow hasn’t even been mapped in detail yet.
You’re right and Curry’s wrong. One nitpick – to get the solar forcing, in addition to dividing by 4, you have to multiply the change in TSI by 0.7 to account for albedo. So the forcing is 30% smaller than your estimates above.
I should also add there’s been a lot of research showing that another grand solar minimum wouldn’t cause more than 0.3°C cooling (or more accurately, would offset no more than 0.3°C warming). So Curry’s comments are at odds with the scientific literature (which isn’t uncommon).
http://www.skepticalscience.com/grand-solar-minimum-mini-ice-age-intermediate.htm
You are forgetting the unknown unknowns. All you did was count up all the things you know about climate and say, well none of these things could (apparently) cause cooling, so its impossible! But there are all sorts of factors we barely understand and interrelations and feedbacks. The fact is the climate has cooled by large amounts on decadal time scales before, there is no reason why those factors could not come about in the 21st century. Yes, there is an increase in the radiative forcing due to C02, but that is just one factor, you cannot ignore all the others! Don’t forget that there could be an ice age coming as well! Our C02 may or may not be enough to stop that, who knows?
The point Curry is making about the IPCC is that it is part of their stated mission to only study CO2 and other ahtropic emissions, therefore they are structurally blind to other possibilities. This is a major weakness.
Patrick,
Not really. If we continue increasing our emissions, the radiative forcing will continue to increase and we will remain out of energy balance. A system that is receiving more energy than it is losing has to warm – basic thermodynamics. There are some possibilities for cooling – a major asteroid strike, or a lots of volcanic activity. Without those, though, if we accept that our understanding of radiative physics is correct, then decades of cooling is virtually impossible.
There is – of course – the possibility that some fundamental physics is wrong, and that would be remarkable if true. Personally, however, suggesting that something could happen because maybe our fundamental understanding – which is well tested – is wrong, is a little like appealing to magic. If you want to make this type of argument, then you could apply it to anything and we’d all live in terror of the possibility that the Sun might not rise tomorrow morning.
Patrick: The IPCC’s goal is not to study CO2, you might wanna look their goals up before posting. They are studying climate change, wherever that leads them. Cosmic radiation, solar cycles, and pretty much anything that affects Earth’s energy imbalance is quantified and measured.
ATTP, one “known unknown” is what would happen if the WAIS collapses or GIS icemelt really speeds up. This will change ocean currents, which could cause cooling or warming. Thing is, if we’d get there anywhere soon, we’re really in deep doodoo.
Marco,
That’s an interesting point, I hadn’t thought of that. Of course, if it did produce cooling while we still increased our emissions, it would be a thermodynamically interesting situation.
ATTP, cf http://www.uea.ac.uk/~dps/publications/RWHSB05.pdf
AOM,
IPCC’s declared task is to assess climate change, not climate science or climate more generally. It was formed to support UNFCCC, which defined explicitly that climate change means AGW. From the UNFCCC web page we can read:
That’s the rationale behind IPCC. All it’s activities are built on that.
There’s nothing wrong in that.
Pekka/AOM/Patrick
Obviously understanding natural variability is “relevant” – actually essential – to this task – which is why they include it.
VTG,
Understanding natural variability is important for the task, but the basic question is different. It’s not necessary to ask explicitly, what the properties of natural variability are, but rather, what can we tell about AGW taking into account also natural variability. In some cases that requires as much knowledge about the natural variability as the first question, but in other cases lesser knowledge may suffice.
A similar issue applies to the share of AGW in the past warming. The share by itself is not essential for the task of IPCC, what’s more essential is climate sensitivity (all varieties: TCR, ECS, TCRE, perhaps others). Some of the uncertainties in the estimate of the historical share of AGW do not contribute to the uncertainty of the sensitivity, while many do.
Marco,
Interesting link, thanks. Two immediate thoughts are that even that would seem to only be about a decade of cooling, rather than decades. Also, I wonder if the simulation was self-consistent. If you wanted to rapidly melt a large portion of an Antarctic ice sheet, you’d need a fair amount of energy, so such a scenario might imply that a large fraction of the energy imbalance is associated with this melting and, hence, not with warming the rest of the climate system. Whether that is physically plausible or not, is another issue, I guess.