## Reconciling ECS estimates – again

I’m heading home after giving a public talk, and have a bit of time to write about the recent Armour paper Projection and Prediction: Climate Sensitivity on the rise. It’s basically another attempt to reconcile energy balance estimates for climate sensitivity, with other estimates. Although the ranges for the different estimates do overlap, energy balance estimates (or observationally-based estimates) imply that equilibrium climate sensitivity (ECS) might be lower than the other estimates suggests.

The basic energy balance calculation is

$ECS_{infer} = \dfrac{F_{2\times}}{\lambda} = \dfrac{F_{2\times} \Delta T}{\Delta F - \Delta Q},$

where $F_{2\times}$ is the change in forcing after doubling atmospheric CO2, and $\lambda$ is the feedback factor. As can be seen in the equation above, this can be determined from the observed the change in temperature $\Delta T$, the measured change in system heat uptake rate $\Delta Q$, and an estimate for the change in radiative forcing, $\Delta F$.

However, as Armour (2017) says, when using the above to estimate ECS a

key, but often unstated, assumption:[is that] that the global climate feedback in operation when equilibrium is reached, $\lambda_{eq}$, will be equal to the feedback in operation at any given time, $\lambda$.

There are, however, indications that the feedback response may not be constant over time, possibly due to the pattern of the warming not being constant. This would imply that the above assumption is not correct and that the ECS inferred from a basic energy balance calculation will not necessarily accurately represent the actual ECS. This is illustrated in the figure below. It shows, as a function of time, (for both abrupt CO2 injections and 1% per year CO2 ramping) the ratio of the actual ECS to the ECS inferred using the energy balance approach. Essentially, the inferred ECS is typically smaller than the actual ECS.

Credit: Armour (2017)

Credit: Armour (2017)

If you use an estimate for the ratio of the actual ECS to the inferred ECS, you can then correct the ECS estimates, as shown in the figure on the right. This also includes a correction that takes into account that the models typically use air temperatures, while the measured surface temperatures are a combination of air and sea surface (as initially presented in Richardson et al. 2016). It also includes an additional correction which takes into account that the ratio might also depend on the actual ECS value. Overall, this does a good job of reconciling the energy balance estimates with the estimates for climate models, and suggest a best estimate for the ECS of around 2.9K, and a 90% range from 1.7 to 7.1K.

A few additional points. We don’t know that these adjustments are correct. However, we do have a situation where there is a mismatch between different climate sensitivity estimates. We also have plausible arguments that can reconcile these estimates. This doesn’t make this reconciliation correct, but does at least provide arguments for why we shouldn’t dismiss the possibility of climate sensitivity being higher than the basic energy balance estimates suggest – especially as these estimates require assumptions that may not be true (constant feedbacks).

There was another point that I wanted to try and make, but may not do very well, as it is getting late. What we’re trying to do is produce a distribution that gives us some indication of what we might expect climate sensitivity to be. There is, however, essentially only one answer; we just don’t know what it is. We want to use these estimates to inform how our climate might responds to future changes in anthropogenic forcing. In some sense, we may never really know which estimates where right, as we would only really regard the energy balance estimates as having been wrong if climate sensitivity turns out to be very high (say > 4K), and the others as being wrong if it turns out to be very low (say < 1.5K).

However, trying to argue for a reduced probability in some region of parameter space, when we can't yet know that this region is actually less likely, seems – to me, at least – a poor way to inform ourselves. Given that these energy balance estimates do not actually rule out (with high confidence) much of the standard ECS range, and given that there are plausible reasons as to why they might be producing a range that is skewed to lower climate sensitivity values, would seem to suggest that we should be careful of using them to strongly influence our assessment of the expected range for climate sensitivity.

Anyway, my train is almost due in, so I'll probably stop there. Hopefully I've explained this fairly clearly (it's been a long day) and if others have comments, feel free to make them.

Nic Lewis already has a post on how inconstant are climate feedbacks, and does it matter? The answer to the question he poses (according to Nic, at least) is essentially that they are not inconstant and, even if they were, it wouldn’t matter.

This entry was posted in Climate change, Climate sensitivity, ClimateBall, Judith Curry, Science and tagged , , , , , . Bookmark the permalink.

### 86 Responses to Reconciling ECS estimates – again

1. Arthur Smith says:

Hmm, I take Lewis’ post as essentially conceding the point (though he quibbles about the details) and then arguing that what matters in the near term is the transient sensitivity, which is quite true and I think widely accepted – the battles over equilibrium sensitivity have always been about very long term effects that shouldn’t really matter unless we don’t do anything at all about CO2. As to feedbacks being time dependent, there are a lot of ways time enters in here that complicates this sort of simple analysis and it’s never been clear to me what most people mean by time dependency in feedbacks. I think their rigorous definition (Bony st al partial differentials) only works at equilibrium. Outside of that, each feedback process in itself has a time profile for its response, so the distribution of feedbacks in effect at any given time depends strongly on the history of forcing. It’s complicated.

2. Arthur,

and then arguing that what matters in the near term is the transient sensitivity, which is quite true and I think widely accepted

Well, yes, but I think his suggestion below is too strong

That is because up to 2100 warming will depend very largely on the level of the transient climate response (TCR), not on equilibrium climate sensitivity (ECS). The claims made by Kyle Armour have no bearing on TCR or on its estimation from warming over the instrumental period.

I think that the feedback response could change before 2100 and, therefore, if you infer the TCR from observations and then use that to estimate how much we might warm by 2100 (given some assumed change in forcing) the estimate will be wrong if future feedbacks are not the same as they have been in the past.

3. I’ll make a quick comment about Nic’s TCR argument. If you look at Lewis & Curry, their 90% range for the TCR is around 0.9K to 2.5K. The standard range is also about 1K to 2.5K. They overlap strongly. The main difference is the best estimate, which Lewis & Curry would put at around 1.35K, while other best estimates are more like 1.8 – 1.9K. However, given various uncertainties, trying to argue for one over the other seems a bit much.

However, there’s another interesting factor. A while back I wrote a post arguing that the ratio of Nic Lewis’ TCR best estimate to his ECS best estimate is probably too high. It would suggest that we could never really sustain a large planetary energy imbalance, and yet we do. Our unrealised warming today probably makes such a large ratio unlikely.

However, in his recent post about the new Armour paper, he essentially seems to be arguing that even if Armour’s argument about the ECS has merit, it doesn’t matter because it has no bearing on the TCR and the TCR is what really matter for the near to medium-term future. Well, if he’s arguing for his best estimate (about 1.35K), then he nows has a TCR-to-ECS ratio smaller than 0.5 (assuming Armour’s best estimate of around 2.9K is about right). Well, this too seems a bit implausible given that it would imply a very large amount of unrealised warming; probably larger than our current planetary energy imbalance suggests.

4. verytallguy says:

From Realclimate

What would it actually take to make a real argument?

As I’ve been asking for almost three years, it is way past time for Curry to shore up her claims in a quantitative way. I doubt that this is actually possible, but if one was to make the attempt these are the kind of things needed:

Evidence that models underestimate internal variability at ~50-80 yr timescales by a factor of ~5.
Evidence that indirect solar forcing can increase the long-term impact of solar by a factor of 3 on centennial time-scales or reverse the sign of the forcing on 50-80 yr timescales (one or the other, both would be tricky!).
Evidence that warm surface ocean oscillations are associated with increased downward net radiation at the TOA. [This is particularly hard because it would mean the climate was fundamentally unstable].
Evidence that the known fingerprints of different forcings are fundamentally wrong. Say, that CO2 does not cool the stratosphere, or that solar forcing doesn’t warm it.

My bold.

5. ‘The main difference is the best estimate, which Lewis & Curry would put at around 1.35K, while other best estimates are more like 1.8 – 1.9K.’

From 1951 to 2015, TCR is around 1.35 (or a bit less) for Cowtan&Way, Hadcrut4 and Berkeley. Only GISS gives a higher ratio – a bit below 1.6. Not sure about NOAA.

‘Well, if he’s arguing for his best estimate (about 1.35K), then he nows has a TCR-to-ECS ratio smaller than 0.5 (assuming Armour’s best estimate of around 2.9K is about right)’
Apples and oranges. Armour’s 2.9K comes after increasing the TCR from Otto2013 (1.35K iirc) by 24%, following the Richardson ‘adjustment’. This gives TCR of 1.67 or so, but by definition leaves the TCR-to-ECS ratio unaffected.

What affects the TCR-to-ECS ratio is the fact that (in most models) equilibrium sensitivity (called ECS in Armour’s paper) is greater than effective sensitivity (called ECSinfer by Armour). But strictly speaking, this is apples and oranges again. Lewis&Curry had a ratio of TCR to effective sensitivity of 0.8; if equilibrium sensitivity is greater than effective sensitivity, then of course the ratio of TCR to equilibrium sensitivity would be lower. So TCR-to-ECS ratio could be 0.8 if we’re talking about effective sensitivity, or 0.7 about equilibrium, for example.

6. What affects the TCR-to-ECS ratio

What actually largely sets it is the rate at which energy can be transferred to the deep ocean (below the mixed layer). If this is very slow, then we will quickly heat the mixed layer/atmosphere very close to equilibrium and then slowly (over many centuries) tend towards equilibrium. The TCR-to-ECS ratio will be high. If, however, it is fast then we rapidly transfer energy into the deep ocean, and we might approach equilibrium more rapidly, but the TCR-to-ECS ratio will be lower. Mosy climate models suggest a ratio of around 0.6. This paper suggests that an intermediate response might better match observations. It could be around 0.8, and could be below 0.5, but these both seem rather inconsistent with observations which might suggest a ratio of around 0.7.

if equilibrium sensitivity is greater than effective sensitivity, then of course the ratio of TCR to equilibrium sensitivity would be lower. So TCR-to-ECS ratio could be 0.8 if we’re talking about effective sensitivity, or 0.7 about equilibrium, for example.

Except I’m talking about actual TCR to actual ECS. I’m suggesting that Nic’s claim that it has no bearing on the TCR (even if the correction for ECS is correct) doesn’t sound right given that it would then imply an implausibly low TCR-to-ECS ratio.

7. Since I linked to an Isaac Held post above, this one is also relevant.

8. Except I’m talking about actual TCR to actual ECS.

In that it can be observed, TCR is actual. ECS is hypothetical, not actual.

9. TE,
Sigh! I was (as I’m sure you realised) trying to distinguish between effective ECS/TCR (those determined using energy-balance methods/observationally-based) and what they would actually be.

10. Jai Mitchell says:

I would like to see a check of the Armour paper methodology by comparing modeled period 2002-2009 results with period 1978-1984 periods. First had rising aerosol emissions second had reduced emissions globally. Impacts could be significant but problem with OHC data from the period.

11. verytallguy says:

In that it can be observed, TCR is actual. ECS is hypothetical, not actual.

Is, I fear, not correct.

What can be observed is the temperature change, with uncertainty. Forcings can be modelled from observations, some much more accurately than others.

These can then together generate a model from which TCR can be estimated. Internal dynamics of the system means, of course, that it is certain that any two datasets from different time periods of observations will generate different TCR estimates.

So I don’t think it is any more possible to observe TCR than it is to observe ECS. It *might* be the case that uncertainty in TCR is less than uncertainty in ECS.

https://www.ipcc.ch/ipccreports/tar/wg1/345.htm

12. John Hartz says:

While we continue to slice and dice ECS and related issues, manmade climate change continues to impact all components of the Earth’s total climate system at an ever increasing rate. As to be expected, these impacts are especially noticeable in the Cryosphere. Here’s a summary of recently observed phenomena that should send shivers up and down our spines…

Scientists have discovered vast systems of flowing water in Antarctica. And that worries them. by Chelsea Harvey, Energy & Environment, Washington Post, Apr 19, 2017

When it comes to mitigating and adapting to manmade climate change, time is not on our side.

13. angech says:

.”..and Then There’s Physics says: “What affects the TCR-to-ECS ratio
What actually largely sets it is the rate at which energy can be transferred to the deep ocean (below the mixed layer). If this is very slow, then we will quickly heat the mixed layer/atmosphere very close to equilibrium and then slowly (over many centuries) tend towards equilibrium.”
If it takes a long time to transfer the energy to the deep ocean would the atmosphere heat up a lot more than the stated near equilibrium? In other words the atmosphere must shoot over equilibrium by quite a lot to actually end up transferring heat to the deep ocean.This should happen sooner rather than later if the heat is that hard to get into the deep ocean.

The basic energy balance calculation is a given. It just seems to be the degree of sensitivity that is the problem. It should be able to be assessed/has been assessed by using recent observations which unfortunately do not seem to agree with the models.

14. angech,

If it takes a long time to transfer the energy to the deep ocean would the atmosphere heat up a lot more than the stated near equilibrium? In other words the atmosphere must shoot over equilibrium by quite a lot to actually end up transferring heat to the deep ocean.

No, if the atmosphere warms above equilibrium, then we will start losing energy back to space.

It should be able to be assessed/has been assessed by using recent observations which unfortunately do not seem to agree with the models.

Well, no, because on short timescales internal variability can dominate and you can’t accurately assess the externally-forced signal.

15. angech says:

Thanks. Covers both points. I will have to think more about about the first one. Seems very sensible. I feel I am missing something there. Probably my bias showing.
There is a complimentary post to yours at JC. Will see if that offers any help.

16. https://www.nature.com/articles/ncomms14856
any thoughts about this study of carbon cycle and the apparent need for large scale CCS success?

17. anoilman says:

smallbluemike: I have serious doubts about CCS ever being viable. You’ll need to find a place on earth where no one has been… build a coal plant there… or a pipeline from a coal plant to there.. . then compress and shove the CO2 down. But we don’t have forever concrete, and the risks of future leaks and explosions are a real concern. (Much bigger if you’ve ever drilled there. Ever.)

We looked at CCS in Alberta and the issues are huge. With so much oil here, you can’t find a piece of ground that won’t leak. Although it can be co-opted into EOR (Enhanced Oil Recovery), but the cost for the pipelines to ship the CO2 are expensive.

Saskatchewan has unsuccessfully implemented a CCS system, and they’ve been able to ship some carbon for EOR. Their costs are going to \$0.12 per kwh.

18. In other words the atmosphere must shoot over equilibrium by quite a lot to actually end up transferring heat to the deep ocean.

The warmer the surface waters become, the more buoyant and less prone to mixing they become. That might argue somewhat for an increase in sensitivity with time – the oceans take up less heat as surface temperatures rise.

19. bluemike,

“anthropogenic emissions need to peak within the next 10 years, to maintain realistic pathways to meeting the COP21 emissions and warming targets.”

20. TE,
Good to see you included a “may” in that.

21. that would be great if it is true. I want to see more data and longer line. Peak followed by a steep decline would be great to see. I watch one number CO2 ppm per MLO, It’s really hard to spin or obscure the message of that number.

Daily CO2

ALL TIME HIGH >> April 18, 2017: 410.28 ppm
April 18, 2016: 407.80 ppm

Dr Mann said in 2014 that we should keep that number under 405. uh-oh.

Thanks for playing, we have some lovely parting gifts for you!

Mike

22. I am inclined to agree with you that CCS is not ever going to be viable. I hope we are wrong because the COP climate stabilization plans assume CCS is going to work somewhere somehow. gotta get busy with mousetrap that catches CO2.

23. izen says:

@-J H
“While we continue to slice and dice ECS and related issues, man-made climate change continues to impact all components of the Earth’s total climate system at an ever increasing rate. ”

Agreed, climate sensitivity as defined is an arbitrary metric for evaluating GCMs. How it impacts the real world always seems like a pinhead-angel ratio discussion.
Here is another real event that escapes capture by increasing the accuracy of the TCR-ECS ratio.

The amount of extra energy, in Joules, that the surface (land and ocean) is absorbing as a result of accumulating CO2 is well constrained by theory and observation.
If climate sensitivity is low, then it means that energy being distributed more rapidly into oceans. But if equilibrium is to be maintained then the extra energy has to be lost to space. Thermal emission seems to be the only way and that will eventually require a temperature rise. The Stephan-Boltzman curve constrains the amount of energy that can be lost, unless you invoke coherent emissions.

I find the concept of a low climate sensitivity at least equally worrying as a high climate response. That at least ensures a rapid return to equilibrium. Low climate sensitivity would mean those Joules are going to do other things than raising temperature. It seems myopic to presume the other effects are more benign that warming.

“Right now, no one wants to make the conclusion that we are starting to enter a Heinrich Event. Or worse — that the present rate of warming at 30 times faster than at the end of the last ice age is rapidly putting us in peril.”

24. John Hartz says:

izen: It bears repeating, CS is metric invented by the human mind. It does not exist in the physical world. In this context, much of the discussion about CS on the blogosphere is illusional.

25. John Hartz says:

We all can agree that, by definition, CS is a metric related to the behaviour of just one part of one component of the total global climate system, i.e., the temperature of the lower troposphere. Have scientists/modelers created metrics comparable to CS for the other components of the system?

26. Willard says:

> CS is metric invented by the human mind. It does not exist in the physical world. In this context, much of the discussion about CS on the blogosphere is illusional.

Salaries are expressed in numbers. Just like money and time, they are social constructs. Therefore any discussion of salaries are illusionary.

Does climate really exist?

MattStatt tried to pull the same trick at Judy’s yesterday:

https://judithcurry.com/2017/04/18/how-inconstant-are-climate-feedbacks-and-does-it-matter/#comment-846378

27. izen,
I’m not sure I’m following your argument. The amount of energy we accrue will also depend, I think, on climate sensitivity. If it is low, then we would accrue less energy than if it is high.

28. Willard says:

> . If it is low, then we would accrue less energy than if it is high.

Less energy by some time unit, AT.

Take both ends of the CS span, and pick a threshold: what time difference does it make to reach that threshold?

I suspect that, to borrow NicL’s ringtone, sensitivity issues aren’t that relevant for what needs to be done.

29. Less energy by some time unit, AT.

I don’t think so. We will accrue less energy (in returning to equilibrium) if CS is low, than if it is high.

30. JCH says:

I agree with aTTP, which is not a good sign for aTTP.

31. John Hartz says:

Wlliard:

Read my lips, “…much of the discussion about CS on the blogosphere is illusional.”

CS does not exist in the physical world. Many blogopshere discussions of it, would lead one to conclude that it does.

My observation has nothing to do with MattStatt’s comments. (I refuse to visit Curry’s blog out of principle.)

You can bet your sweet bippy that the Earth’s climate system exists in the physical world.

32. Willard says:

JohnH,

You can bet your sweet bippy that money does not exist in the physical world. Yet it’s quite relevant to us. So now read *my* lips – your argument is invalid.

It’s not because CS does not exist that most sensitivity matters are irrelevant. It’s because whatever central estimate one might fixate on doesn’t matter much for our infrastructure choices. To borrow from JoeR (this may be the only time I do) we’re driving way too fast already:

One may argue that CS exists the same way the ideal gas law does, BTW. Unless you’re willing to drop the ideal gas law, JohnH, I suggest you find yourself something else than an ontological argument.

33. John Hartz says:

Willard: I have no need to continue to debate with you over the existence or non-existence of CS in the physical world. I do, however, agree with you that we have much bigger fish to fry re the mitigation of manmade climate change. That is why I keep pointing out that the accelerating GHG effect driven by mankind’s activities are impacting all components of the Earth’s total climate system, not just lower troposphere. What’s happening in the cryosphere, for example, is truly scary.

34. Willard says:

> We will accrue less energy (in returning to equilibrium) if CS is low, than if it is high.

Of course. My point regarding energy per time unit was to hint at something like this:

The socioeconomic value of better understanding the ECS is well documented. If the ECS were well below 1.5 K, climate change would be a less serious problem. The stakes are much higher for the upper bound. If the ECS were above 4.5 K, immediate and severe reductions of greenhouse gas emissions would be imperative to avoid dangerous climate changes within a few human generations. From a mitigation point of view, the difference between an ECS of 1.5 K and 4.5 K corresponds to about a factor of two in the allowable CO2 emissions for a given temperature target [Stocker et al., 2013] and it explains why the value of learning more about the ECS has been appraised so highly [Cooke et al., 2013; Neubersch et al., 2014]. The ECS also gains importance because it conditions many other impacts of greenhouse gases, such as regional temperature and rainfall [Bony et al., 2013; Tebaldi and Arblaster, 2014], and even extremes [Seneviratne et al., 2016], knowledge of which is required for developing effective adaptation strategies. Being an important and simple measure of climate change, the ECS is something that climate science should and must be able to better understand and quantify more precisely.

The sentence emphasized seems to undermine the idea the authors are trying to sell in that paragraph. While a factor of 2 may have a substantial impact on centennial scale, its impact on decadal scale isn’t that great, and below that it’s barely noticeable. Facing the two extremes (1.5K and 4.5K), a city’s five-year plan for 4.5K will at worse be still valid for five more years. The same applies for decadal decisions made by states and corporations: even if the rubber meets the road in 20 years instead of 10, it’d be tough to argue that all these investments would have been thrown out of the window.

Moreover, a ratio of 1:2 represents two extremes we barely consider while we’re debating these sensitive matters. When the debate is about whether we should be over or under 3, the payoff becomes academic. The difference in investment timing is so short we can barely speak of intergenerational justice.

In effect, lowballing sensitivity with the lowest justified disingenuousness money the GWPF and other energy think tanks can buy is more than risky business. From a policy perspective, it is barely rational. It indicates a lack of fortitude to address a problem more than anything.

35. John Hartz says:

Willard: I nioticed that you use the term “real world” in your comments and I use the term “physical world” in mine. From where I sit, the two terms do not mean the same thing. Do you agree, or disagree?

36. The Very Reverend Jebediah Hypotenuse says:

John H:

I have no need to continue to debate with you over the existence or non-existence of CS in the physical world.

Exactly.

“The Earth’s climate system” is exactly as much a human construct, a bunch of labelled abstractions, a denoted set of ideas, as “climate sensitivity”.

Debating whether climate sensitivity exists is like debating whether the orbit of the Earth exists.
Or the ideal gas law.

What you can bet your sweet bippy on is this:

As both you and Willard seem to agree – We have important choices to make that do not depend on the ontological status of our terminology.

37. Willard says:

JohnH,

First you’re telling me that you have no need to continue to debate with you over the existence or non-existence of CS. Now you’re trying to split hair on the difference between real and physical by putting “real world” in my mouth. Which is it? While you think about what to do with your stack of chips, let me remind you of my counter-argument:

You can bet your sweet bippy that money does not exist in the physical world. Yet it’s quite relevant to us.

Since you insist, here’s what is said of the ideal gas law:

The ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation of the behavior of many gases under many conditions, although it has several limitations.

An ideal gas does not exist, yet we refer to an ideal gas to approximates the behavior of gases with it. Now, compare and contrast:

Although climate sensitivity is usually used in the context of radiative forcing by carbon dioxide (CO2), it is thought of as a general property of the climate system: the change in surface air temperature (ΔTs) following a unit change in radiative forcing (RF), and thus is expressed in units of °C/(W/m2).

Sensitivity is thus an idealization of the behavior of surface air temperature when subjected to a change in radiative forcing.

And to shake off a bit your certitude that climate exists:

Climate is the statistics of weather, usually over a 30-year interval. It is measured by assessing the patterns of variation in temperature, humidity, atmospheric pressure, wind, precipitation, atmospheric particle count and other meteorological variables in a given region over long periods of time. Climate differs from weather, in that weather only describes the short-term conditions of these variables in a given region.

https://en.wikipedia.org/wiki/Climate

Do you think that statistics exist?

38. John Hartz says:

Willard: I have never asserted that CS does not exist. From my perspective, it does not exist in the physical world in the same way that a forcing, for example, does. Ditto for equations that describe how components the physical world behaves.

I did not state that climate exists in the physical world. I stated that the climate system exists in the physical world.

My statement verbatim:

You can bet your sweet bippy that the Earth’s climate system exists in the physical world.

39. Willard says:

> I have never asserted that CS does not exist.

Of course you did not, JohnH:

It bears repeating, CS is metric invented by the human mind. It does not exist in the physical world. In this context, much of the discussion about CS on the blogosphere is illusional.

By the same token, money does not exist in the physical world. Does it mean it’s “illusional” to care about money?

That something does not exist in the physical world is a poor argument to justify the claim that we ought not discuss it. Most of our values do not exist in the physical world. Heck, most of our social reality does not exist in the physical world. Institutions. Decisions. Personhood. Etc.

40. angech says:

izen says: April 20, 2017 at 4:17 pm
“Here is another real event that escapes capture by increasing the accuracy of the TCR-ECS ratio.

Izen, there are matters of perspective here.
Not every event has to be seen as promoting global warming.
In this context, to my simple brain at least, the presence of increasing numbers of large icebergs presages one of 3 states. Situation normal, situation AGW or situation AGC [cooling].
Now if I think of a really warm world, Greenland loses its ice sheets [glaciers], there are now no icebergs. From now til then I would expect, on average less icebergs.
Situation normal, preferred option, there are decadal and annual fluxations in ice formation and breakup. Larger ice streams this year have broken up at a faster than usual rate at this time of year when they normally breakup [ I guess they break up quicker at this time, growing all winter and now facing rougher seas?? anyone].
In a cooling world the glaciers would be bigger, extend out further and produce more and bigger icebergs as Spring dawns.
Intrigued as to how the TCR-ECS fits in.
As a joke only at least it might improve the polar bears traveling destinations this year.

41. John Hartz says:

Willard: OK. I accept your point.

However, my initial comment as repeated by you was my reaction to how I believe CS is misrepresented in much of the discussion about it in the blogosphere. I not did not make the claim that we ought not discuss it. You inferred that from what I wrote.

42. Ken Fabian says:

Smallbluemike – re CCS. By weight we get 2.8 times as much CO2 emitted as “high quality” black coal burned. Less proportionally for lower quality coal, but then more of that needs to be burned for the same energy output and ultimately more is CO2 emitted. That 2.8 to 1 proportion says to me that CCS is never going to be cheap even if it were easy – and it isn’t.

CCS isn’t a solution. A strong commitment to CCS looks to me like a way to continue to delay and avoid strong commitment to replacing fossil fuel energy using the low emissions alternatives that we have.

43. John

Let me quote from a paper that freed my mind.

“The totality of our so-called knowledge or beliefs, from the most casual matters of geography and history to the profoundest laws of atomic physics or even of pure mathematics and logic, is a man-made fabric which impinges on experience only along the edges. Or, to change the figure, total science is like a field of force whose boundary conditions are experience. A conflict with experience at the periphery occasions readjustments in the interior of the field. Truth values have to be redistributed over some of our statements. Re-evaluation of some statements entails re-evaluation of others, because of their logical interconnections — the logical laws being in turn simply certain further statements of the system, certain further elements of the field. Having re-evaluated one statement we must re-evaluate some others, whether they be statements logically connected with the first or whether they be the statements of logical connections themselves. But the total field is so undetermined by its boundary conditions, experience, that there is much latitude of choice as to what statements to re-evaluate in the light of any single contrary experience. No particular experiences are linked with any particular statements in the interior of the field, except indirectly through considerations of equilibrium affecting the field as a whole.

If this view is right, it is misleading to speak of the empirical content of an individual statement — especially if it be a statement at all remote from the experiential periphery of the field. Furthermore it becomes folly to seek a boundary between synthetic statements, which hold contingently on experience, and analytic statements which hold come what may. Any statement can be held true come what may, if we make drastic enough adjustments elsewhere in the system. Even a statement very close to the periphery can be held true in the face of recalcitrant experience by pleading hallucination or by amending certain statements of the kind called logical laws. Conversely, by the same token, no statement is immune to revision. Revision even of the logical law of the excluded middle has been proposed as a means of simplifying quantum mechanics; and what difference is there in principle between such a shift and the shift whereby Kepler superseded Ptolemy, or Einstein Newton, or Darwin Aristotle?

For vividness I have been speaking in terms of varying distances from a sensory periphery. Let me try now to clarify this notion without metaphor. Certain statements, though about physical objects and not sense experience, seem peculiarly germane to sense experience — and in a selective way: some statements to some experiences, others to others. Such statements, especially germane to particular experiences, I picture as near the periphery. But in this relation of “germaneness” I envisage nothing more than a loose association reflecting the relative likelihood, in practice, of our choosing one statement rather than another for revision in the event of recalcitrant experience. For example, we can imagine recalcitrant experiences to which we would surely be inclined to accommodate our system by re-evaluating just the statement that there are brick houses on Elm Street, together with related statements on the same topic. We can imagine other recalcitrant experiences to which we would be inclined to accommodate our system by re-evaluating just the statement that there are no centaurs, along with kindred statements. A recalcitrant experience can, I have already urged, bc accommodated by any of various alternative re-evaluations in various alternative quarters of the total system; but, in the cases which we are now imagining, our natural tendency to disturb the total system as little as possible would lead us to focus our revisions upon these specific statements concerning brick houses or centaurs. These statements are felt, therefore, to have a sharper empirical reference than highly theoretical statements of physics or logic or ontology. The latter statements may be thought of as relatively centrally located within the total network, meaning merely that little preferential connection with any particular sense data obtrudes itself.

As an empiricist I continue to think of the conceptual scheme of science as a tool, ultimately, for predicting future experience in the light of past experience. Physical objects are conceptually imported into the situation as convenient intermediaries — not by definition in terms of experience, but simply as irreducible posits comparable, epistemologically, to the gods of Homer. Let me interject that for my part I do, qua lay physicist, believe in physical objects and not in Homer’s gods; and I consider it a scientific error to believe otherwise. But in point of epistemological footing the physical objects and the gods differ only in degree and not in kind. Both sorts of entities enter our conception only as cultural posits. The myth of physical objects is epistemologically superior to most in that it has proved more efficacious than other myths as a device for working a manageable structure into the flux of experience.

44. A lower climate sensitivity than we currently expect can be good or bad news. It depends what the reason is. If there is a cloud feedback that keeps the sun from warming the Earth as much then that is good news. If the climate sensitivity is low because more energy goes into the ocean, then we would also get more sea level rise. If the climate sensitivity is low because more of the additional energy goes into evaporation (rather than into warming the air) that would mean that we mess up the water cycle even more. That could well be worse than “just” warming.

45. Anders already cited Lewis & Curry (2014); here’s a relevant quote:

The key issue faced in the AR5 assessment was interpreting the discrepancy between climate sensitivity estimates based on climate models (higher values) versus recent empirically-derived sensitivity analyses (lower values). […] Using a global energy budget approach, this paper seeks to understand the implications for climate sensitivity (both ECS and TCR) of the new estimates of radiative forcing and uncertainty therein given in AR5. This approach avoids to a substantial extent the dependence on AOGCM simulations in previous energy budget studies (e.g. Otto et al. 2013). Further, we refine the energy budget methodology for determining climate sensitivity to minimize the impact of natural internal variability on the estimate of climate sensitivity. And finally, we account carefully for the impact of uncertainties in forcing, ocean heat uptake and surface temperature on the determination of climate sensitivity.

From the abstract of Armour (2017) we read:

I find that the long-term value of climate sensitivity is, on average, 26% above that inferred during transient warming within global climate models, with a larger discrepancy when climate sensitivity is high. Moreover, model values of climate sensitivity inferred during transient warming are found to be consistent with energy budget observations1–3, indicating that the models are not overly sensitive.

(Ref. 2 being L & C (2015))

This crap about TCR mattering more than ECS is nothing less than an attempt to reframe Armour’s argument so as to preserve the perception of L & C (2014/5) as a potent argument against Teh Stoopid Modulz.

Fortunately, we don’t need to go through the brain damage of TCR/ECS calculations at any point in time to read CMIP5 output for a given forcing scenario. Nic provides no such projection, a long-running and glaring omission.

46. John Hartz says:

Victor Venema: I wholeaheartedly concur. We must never become so focused on CS that we loose sight of the big picture, i.e., the global climate system in its entirety. One of the strategies of the Climate Scince Denial Spin Machine is, in my opinion, to suck us into endless discussions of CS.

47. izen says:

@-“The amount of energy we accrue will also depend, I think, on climate sensitivity. If it is low, then we would accrue less energy than if it is high.”

If climate sensitivity is low because there is a cloud negative feedback reducing the amount of surface absorption then I agree that less energy would be added to the CS.
But otherwise, the amount of energy added is proportional to cumulative CO2.
I can see no way to reach equilibrium without raising temperatures to emit that energy via the S-B curve.

@-Willard.
Of course TCR-ECS is real, like money.
And like money it is an abstract arbitrary definition constructed for its usefulness .
Not its physical accuracy.

48. verytallguy says:

Izen,

re. “I can see no way to reach equilibrium without raising temperatures to emit that energy via the S-B curve.”

It’s my understanding that the standard definition of ECS, the Charney sensitivity, does not include heat uptake by the deep ocean, only the “mixed layer”.

So by this definition, deep ocean heat uptake does affect the final “equilibrium” achieved.

ECS is a metric to assess climate response, NOT an expectation as to the final effect of rising CO2 on climate.

At least as I understand it.

49. vtg,

It’s my understanding that the standard definition of ECS, the Charney sensitivity, does not include heat uptake by the deep ocean, only the “mixed layer”.

I don’t think this is correct, because if it was, we’d reach equilibrium within a few years, not centuries. In fact, I’m pretty sure that the TCR-to-ECS ratio is largely set by the rate at which energy diffuses from the mixed layer into the deep ocean.

50. verytallguy says:

You’re right. At least I heavily caveated my post 🙂

51. I think there is some dependence on the very deep ocean, that I’ve never fully understood. Could simply be that the models don’t really incude energy transfer into the deepest parts of the oceans and if this is not negligible, then it will impact the equilibrium sensitivity.

52. verytallguy says:

Perhaps Victor could comment re his

If the climate sensitivity is low because more energy goes into the ocean,

or was that only referring to TCR?

53. JCH says:

If, during the latter years of the observation period, more energy went into the oceans because of intensified trade winds, not seen before, what happens to TCR if the intensified are not seen again?

54. John Hartz says:

Steven Mosher: Thank you for the thoughtful feedback. I sincerely apprecite it.

A follow-up question: From your perspective, is there a difference between physics and meta-physics?

55. izen says:

@-angtech
“In this context, to my simple brain at least, the presence of increasing numbers of large icebergs presages one of 3 states. Situation normal, situation AGW or situation AGC [cooling].”

By clear implication it will also have periods where it is in transition from one of your three states to the other.
For ~7000 years Greenland has been cooling and gaining ice on its icecap. Around half of the Greenland icecap is snow that has fallen since the Holocene optimum. It is a recent development that Greenland {and now Atarctica} are loosing mass. This is not typical behaviour after a glacial melt.

It may be simplistic to see >400 icebergs instead of the usual 80 as just annual variation. The suggestion this is the start of a Heinrich event is probably premature, but the reversal of the expected pattern of ice mass increase during an interstadial is definitely confirmed.

56. John Hartz says:

Willard: My Colombo gambit produced a positive result. We are in agreement. Peace.

57. izen says:

@-JH
“A follow-up question: From your perspective, is there a difference between physics and meta-physics?”

Physics is working on the presupposition that there is a discoverable objective reality that is mathematically computable and logically consistent.

Meta-physics is the discussion of whether that is a useful, accurate or misleading presupposition.

58. The Very Reverend Jebediah Hypotenuse says:

A curious thing about the ontological problem is its simplicity.
It can be put into three Anglo-Saxon monosyllables: ‘What is there?’
It can be answered, moreover, in a word—’Everything’—and everyone will accept this answer as true.

…is there a difference between physics and meta-physics?

Physics attempts to explain phenomena… Metaphysics attempts to explains physics.

59. John Hartz says:

TVRJH:

What atrempts to explain metaphysics? 🙂

Seriously, based on a very cursory review, it appears that scholars are engaged in a very lively debate about the proper definition and application of metaphysics. It’s somewhat similar to our debate over CS.

60. The Very Reverend Jebediah Hypotenuse says:
61. John Hartz says:

Speaking of definitions, I believe that the scientific community has inadvertently made it more difficult to effectively communicate climate science to the average person by using the word “climate” to describe differing things.

Comparing the IPPC/WMO definitions (courtesy of the handy-dandy SkS Glossary of Scientific Terms) of the word climate and the term climate system illustrates my point…

Climate in a narrow sense is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging these variables is 30 years, as defined by the World Meteorological Organization. The relevant quantities are most often surface variables such as temperature, precipitation and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. In various chapters in this report different averaging periods, such as a period of 20 years, are also used.

On the other hand, the climate system is defined to be…

The climate system is the highly complex system consisting of five major components: the atmosphere, the hydrosphere, the cryosphere, the land surface and the biosphere, and the interactions between them. The climate system evolves in time under the influence of its own internal dynamics and because of external forcings such as volcanic eruptions, solar variations and anthropogenic forcings such as the changing composition of the atmosphere and land use change.

Note: Defintions from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

62. Willard says:

> My Colombo gambit produced a positive result.

Nice epithet.

You know, I almost always try to be constructive. Even with contrarians. There would be little point in ClimateBall otherwise. Check my latest:

The Miracle Worker said he wasn’t from UK, André.

Next time you see a police car, try to take it for a ride. It’s public property so it’s yours to use, right?

Good luck with that.

https://judithcurry.com/2017/04/09/bullying-as-scientific-misconduct/#comment-846509

André’s no dummy, and his many Colombo gambits deserve due diligence. It steers into ethics, morality, politics, and the philosophy of law.

63. Steven Mosher says:

“Willard: My Colombo gambit produced a positive result. We are in agreement. Peace.”

Willard would appreciate a Colorado gambit.

64. Steven Mosher says:

” follow-up question: From your perspective, is there a difference between physics and meta-physics?”

Yes. First meta physics has become hard to define. It used to mean the study of being. What is being or substance? What is nothingness? And other such questions. .What are causes…

This sense of metaphysics fades pretty fast after hegel.. and after I suppose you could say the question becomes: Who is asking the question. .that is attention turns to questions about what it means to be human. .what is this thing questioning being.. ah so on the continent at least the questions turn to what is a human. .and so think nietzsche, heidegger..Sartre. so you will see metaphysics turning to questions of free will, what is consciousness, is your mind a physical thing.etc.

In the analytic tradition metaphysics takes a linguistic turn..do universals exist?? Similar questions about mind/body problem, questions about reference bound variables and also free will. Hmm maybe modality..

Metaphysics has a different method. That’s the most important difference. .

65. izen says:

The SKS widget –

http://4hiroshimas.com/

claims we are gaining 4 Hiroshimas a second.
I am still unclear whether climate sensitivity, TCR or ECS, has any influence on the rate of energy accumulation.
Or the cumulative total.

66. Steven Mosher says:

:”claims we are gaining 4 Hiroshimas a second.
I am still unclear whether climate sensitivity, TCR or ECS, has any influence on the rate of energy accumulation.
Or the cumulative total.”

You got it backwards.

67. Chris says:

izen, ECS is straightforward. There are qualitatively straightforward relationships between ECS and rate of energy accumulation and between ECS and cumulative total. Your “cause-and-effect” way of phrasing this “…whether climate sensitivity, TCR or ECS, has any influence on the rate of…” is slightly semantically problematic (and susceptible to smart-aleck one-sentence responses!).[*]

Considering a particular climate system like the Earth’s and the response to a forcing (like enhanced greenhouse forcing including feedbacks), a higher ECS should accompany a faster rate of energy accumulation. If one considers the time-dependence of the surface temperature (or total energy accumulation) response to the forcing, this might appear somewhat hyperbolic as the accumulated energy and the enhanced TOA emission progressively “fills in” the forcing – at equilibrium the forcing is gone. If the climate system has a higher ECS, then we expect the rate of temp/energy accumulation to also be faster.

Reality is a little more complex; the time-dependence of the changes will be a multiple of several time constants as different elements of the system respond with their own characteristic time-dependence (relatively rapid tropospheric response, slower albedo and deep ocean responses etc.). However especially in the early decades of the response to enhanced forcing a larger ECS will be associated with a faster rate.

Note that we must consider this in the context of a particular climate system. One can imagine a climate system such as Earth with much more land and much less ocean where (compared to the real Earth), a lower ECS than Earth’s might have a higher rate of response compared to our real Earth since the damping effect of the oceans would be much less and equilbration with the forcing would occur more quickly.

Cumulatively again ECS and total energy accumulation are related – higher ECS = higher net energy accumulation in the climate system at equilibrium.

Since TCR is some proportion of ECS broadly speaking (see discussion through this thread), I expect the same will apply. On the other hand since the climate response time constants aren’t very well constrained a relatively low TCR might be associated with a high ECS and vice versa. That seems to be a fundamental problem with attempting to determine climate sensitivity from observational data.

that’s how I think of it….

[*] Actually as i think of this again having written my post, your way of phrasing the question is OK

68. John Hartz says:

Chris: I believe Steve Mosher’s question should read:

How does the rate of energy accumulation affect TCR and ECS?.

In other words, I agree with the first paragraph of your response to Mosher.

Based on my understanding of climate sensitivity, it is a metric measuring the behavior of the system. It does not drive the system.

69. I am still unclear whether climate sensitivity, TCR or ECS, has any influence on the rate of energy accumulation.
Or the cumulative total.

Here’s my rather simplistic understanding (happy to be corrected if wrong). The ECS will ultimately determine how much energy we will accrue in total. As a rough approximation, if the ECS is 3K, then we’d expect the entire system to ultimately warm by about 3K. For a given ECS, the TCR will determine the rate at which we accrue energy. If the TCR is close to the ECS, then we will approach equilibrium rapidly, and then continue to accrue energy slowly. If the TCR is quite different to the ECS, then we will remain further from equilibrium and accrue energy more rapidly (most of which will be heating the deeper ocean, rather than the surface ocean).

70. John Hartz says:

ATTP: Two questions:

How can a meatric that measures how a sysem behaves also “determine” how it will behave?

Do you believe that ECS is a constant ratio over a long period of time?

71. Chris says:

John, I think you’re falling into a semantic trap yourself. The climate sensitivity isn’t really “a metric that measures how the system behaves”, although one knows what you mean when you say that.

Rather the climate sensitivity is a fundamental property of the climate system (one might qualify that by saying it’s “a fundamental property of the climate system in its particular state” to account for the likelyhood that the CS is somewhat state dependent). Stated like this it’s acceptable to say that the climate sensitivity ultimately determines how much energy the climate system accrues…

72. Chris says:

In fact there are lots of phenomena with semantically-similar terms:

e.g. one could say ” how can the heat capacity determine how much the temperature of a body of water will rise given a particular energy input when the heat capacity is a metric that measures how the system behaves”?

climate sensitivity like heat capacity are respective properties of the particular system…having recognised these properties we have to give them a name (and may also determine an equation or two to define them)…

73. JH,

How can a meatric that measures how a sysem behaves also “determine” how it will behave?

Yes, it was poorly worded. I was really just trying to point out that the ECS is related to how much energy we will accrue in total, and the TCR (or the TCR-to-ECS ratio) is related to the rate at which we will accrue that energy.

Do you believe that ECS is a constant ratio over a long period of time?

Well, no, it’s really just a model metric that allows us to quantify the sensitivity of the system under certain assumptions (fast feedbacks only). In reality there will be a base temperature dependence (it’s probably non-linear) and there will also be slow feedbacks that will also influence the overall warming.

74. John Hartz says:

Chris: Your explanation is a perfect example of why it is so difficult to translate “science-speak” into plain English. Rather than acknowledging this reality, you and others label it to be a “semantic trap.” We need to move beyond this impasse.

75. John Hartz says:

Chris & ATTP:

When I am asked, What is climate sensitivity?, I typicall respond with the following:

Climate Sensitivity

In IPCC reports, equilibrium climate sensitivity refers to the equilibrium change in the annual mean global surface temperature following a doubling of the atmospheric equivalent carbon dioxide concentration. Due to computational constraints, the equilibrium climate sensitivity in a climate model is usually estimated by running an atmospheric general circulation model coupled to a mixed-layer ocean model, because equilibrium climate sensitivity is largely determined by atmospheric processes. Efficient models can be run to equilibrium with a dynamic ocean.

The effective climate sensitivity is a related measure that circumvents the requirement of equilibrium. It is evaluated from model output for evolving non-equilibrium conditions. It is a measure of the strengths of the climate feedbacks at a particular time and may vary with forcing history and climate state. The climate sensitivity parameter (units: °C (W m–2)–1) refers to the equilibrium change in the annual mean global surface temperature following a unit change in radiative forcing.

The transient climate response is the change in the global surface temperature, averaged over a 20-year period, centred at the time of atmospheric carbon dioxide doubling, that is, at year 70 in a 1% yr–1 compound carbon dioxide increase experiment with a global coupled climate model. It is a measure of the strength and rapidity of the surface temperature response to greenhouse gas forcing.

Definition courtesy of IPCC AR4.

Do the two of you consider this to be “gold standard” definition of CS?

76. John Hartz says:

ATTP: Thanks for the feedback. My second question was rather poorly worded. I should have asked: Do you believe that the CS of a climate system experiencing a rapidly accelerating greenhouse gas effect will remain constant over time?

77. John Hartz says:

Chris: Thanks for the feedback. My initial respnse may have been a tad edgy. If so, I apologize for its tone.

78. John – thanks for raising this question: “Do you believe that the CS of a climate system experiencing a rapidly accelerating greenhouse gas effect will remain constant over time?” I have wondered about that, but CS is not my strong suit. I am a one trick pony, I just track CO2 in the atmosphere. I am interested in a lot of climate subjects, but I am not a climate scientist, I am social scientist. I track CO2 in atmosphere because that is where the rubber meets the road in terms of human behavior. If the number goes up, we are getting it wrong. If the number goes down, we are getting it right. A lot of humans get fooled by spin about falling emissions, but if our “falling emission” progress does not quickly produce falling atmospheric CO2 levels, then it is meaningless. Like your question abt a time of rapidly accelrating ghg effect, I think that when we are at 410 ppm, slowing the rate of increase is not enough. The number has to go down.

Several folks here have made the point that arguing endlessly about the CS number is pretty meaningless because we know what we need to do, we need to reduce CO2 in the atmosphere and we need to do it quickly if we want to reduce human conflict and suffering.

It really is that simple and the US voting population read the handwriting on the wall and lots of them voted to elect folks who deny the basic science of global warming. It’s hard to know what to say or do in response to that. My sense is that the species is failing this test.

per MLO:

Week beginning on April 16, 2017: 409.61 ppm
Weekly value from 1 year ago: 407.48 ppm

Warm regards

Mike

79. John Hartz says:

Mike: I consider my probing akin to peeling the layers of an onion, not ranting per se. Sometimes, I get frustrated at both myself and others and it affects the tone of my comment.

80. I think it’s fine to get in rant mode on occasion. We have painted ourselves into a pretty tight corner and it is frustrating so see folks propose that more paint is the solution. We need to cultivate thick skins and a sense of humor in these times. We need to support each other when any of us is so frustrated that they switch to rant mode. I think almost all of us do that on occasion.

I think blog rule number one may be “don’t feed the trolls” and number two might be “don’t take it personally when someone goes off on a rant.”

81. John Hartz says:

Mike: During my 32-year profesional carreer, I spent a goodly amount of my time translating “transportation technical speak” into plain English so that the it would be digestable by the general public. I have been doing something similar re “climate science” for over a dozen years now as a member of the Skeptical Science author team. Climate sensitivity is definitely one of the harder nuts to crack.

82. John Hartz says:

Mike: Peeling an onion can induce tears. 🙂

83. Climate sensitivity is definitely one of the harder nuts to crack.

Why is this? It is really just how sensitive our climate is to external perturbations/changes. Sensitive, here, normally means how much we will warm for a given external change. I realise that there are complications like, Transient, Equilibrium, Earth System, but from a public perspective these details may not matter all that much.

84. Chris says:

That’s OK John, There’s clearly a difference of perspective about the term “climate sensitivity”. I consider it to be a fundamental property of the climate system. It’s also very easy to understand –
“double atmospheric CO2 (or an equivalent forcing) – what does the surface temperature eventually re-equilibrate at?”

It’s fundamental in the context of climate science and human welfare. The former, for (at least) two reasons – (i) because it defines the major first-order question (“how much warming will there eventually be”?) and (ii) because the climate sensitivity is something that can be estimated in an informative manner from interpretation of paleo-data. The latter (human welfare), because we live at the Earth surface and we know the second-order effects of moderate to high climate sensitivity are likely to be somewhere on the spectrum between problematic and dire.

The TCR is more of an operational parameter I would say, that incorporates the fact that we may think it’s of more immediate concern to know how much warming there will be on the multi-decadal timescale (rather than some psychologically indeterminate time in the future).

“Do the two of you consider this to be “gold standard” definition of CS?”

The first sentence of your IPCC paste encompasses ECS to my mind: “In IPCC reports, equilibrium climate sensitivity refers to the equilibrium change in the annual mean global surface temperature following a doubling of the atmospheric equivalent carbon dioxide concentration.”

TCS is bound to be more problematic because we don’t have a very good handle on the fundamental response times of the relevant parts of the climate system, and these are not amenable to estimation from paleo-data.

85. John Hartz says: