## A thought experiment

To follow up on my – possibly poorly titled – post from a couple of days ago, I thought I would pose a thought experiment. This is entirely unrealistic and is just intended to, maybe, illustrate what I was trying to get at in the earlier post. Of course, it may fail dismally, or may just be too unrealistic to make any sense, but I’ll give it a try.

Consider the following scenario. We start with the planet in energy balance and then we emit, in a short space of time, a large amount of CO2 that increases atmospheric CO2 concentrations. Afterwards, we fix our emissions to maintain, but not increase, this higher atmospheric CO2 concentration. This increase will produce a change in anthropogenic forcing. Consider also that at the same time the Solar forcing increases by an amount greater than the increase in anthropogenic forcing. Given these two increases in external forcing, we will warm and – one might argue – that we will be mostly warming because of the change in solar forcing.

Now imagine that at some point in the future, the Solar forcing drops back down to what it was at the beginning, so that there is now no net change in solar forcing. Also, imagine that this happens at a time when the increase in temperature exactly compensates for the increase in anthropogenic forcing (and associated feedbacks), so that the system is again in energy balance.

So, we have a situation where the only change in forcing is anthropogenic and in which the system has warmed so as to retain energy balance. Is the warming :

1. Mostly – or all – natural.
2. Mostly – or all – anthropogenic.
3. Both natural and anthropogenic.
4. Neither.
5. It’s just too complex to really describe in such a simple way.
6. Stop writing posts that don’t make any sense and just confuse everyone.

Okay, there’s my thought experiment. Remember, it’s not meant to be realistic and is just an attempt to maybe illustrate what I was trying to get at in my earlier post. It may not succeed in doing so and – just to avoid confusion – I’m really not trying to argue that changes in solar forcing can’t warm us (i.e., if you think that the point I’m trying to make is that there is no such thing as natural warming, you’d be wrong).

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### 88 Responses to A thought experiment

1. That presupposes that the anthropogenic emissions can result in surface warming rather than simply an adjustment in global air circulation which negates the thermal effect at the surface of the anthropogenic forcing.

The trouble is that, on average, energy in must equal energy out so if anything other than energy in alters the surface temperature then the system is permanently destabilised and the atmosphere cannot be retained in the long term.

You see, if GHGs reduce the energy outflow and thereby warm the surface then a new equilibrium can never be attained because those same GHGs reduce the additional outflow from the enhancement of the surface temperature too and so on ad infinitum.

Over enough time a tiny increase in GHGs could cause the entire atmosphere to be lost as a result of accumulating surface heat over aeons.

Since it has never happened in 4 billion years there must be an effective negative response inherent in the system.

If you don’t want me to post here just say so.

2. Tom Curtis says:

What happened to response 6a – stop writing posts that will just confuse people who wish to maintain their firm belief that recent warming is not anthropogenic?

3. Stephen,

That presupposes that the anthropogenic emissions can result in surface warming rather than simply an adjustment in global air circulation which negates the thermal effect at the surface of the anthropogenic forcing.

They can. This is not in dispute.

Over enough time a tiny increase in GHGs could cause the entire atmosphere to be lost as a result of accumulating surface heat over aeons.

No, you’re assuming a runaway process, rather than one that simply equilibrates at a higher temperature. The former is possible (Venus) but the latter is what has been happening on Earth.

If you don’t want me to post here just say so.

That might be best. On the other hand if you really would like to understand this better, there are many commenters here who are remarkably knowledgeable about this topic and will typically answer genuine questions. If that interest you, you’re welcome to give it a go. If you’re just going to essentially deny the greenhouse effect, then staying away would be preferred.

4. Tom,
I think that’s a more general issue than simply something related to this post 🙂

5. Tom Curtis says:

Stephen Wilde, [Mod: Be nice, please]

6. metzomagic says:

What Tom said. Thought experiments only work as a means of getting across a simple concept when people are willing to approach them with an open mind, not with ideological blinders on.

Also, they must understand the science behind the thought experiment. If they are off on some weird tangent like SW here, they’ll just screw up the experiment by applying their pseudoscience to it.

7. pblackmar says:

Obviously, once natural forcing cancels itself out, any remaining warming will be anthro. Determination of the natural cycle must be difficult, however, if there are multiple natural forcings of difference cycle lengths. Particularly when multiple natural forcings combine while all positive or negative. I think this illustrates where some have questions regarding climate sensativity to CO2. I’m not saying what’s right or wrong, just an observation. Further complicating the issue is multitude of ways incoming energy might manifest itself with relative/specific humidity, albedo and absorbtion.

These are not scientific observations but rather points to consider when communicating with the public. Current methodology between scientists in the field, or media, is to get feathers ruffled rather than entertain respectful debate. Only when carefully considering an opposing opinion can a truly logical and meaningful response be constructed. Hopefully one day soon the “Climate Wars” will be recognized for the opportunity it is to convey thoughts and impact opinions rather than a need to hide in order to avoid the mud slinging.

8. pblackmar,

Obviously, once natural forcing cancels itself out, any remaining warming will be anthro.

Yes, that was certainly one of the points I was trying to get across.

Determination of the natural cycle must be difficult, however, if there are multiple natural forcings of difference cycle lengths. Particularly when multiple natural forcings combine while all positive or negative. I think this illustrates where some have questions regarding climate sensativity to CO2. I’m not saying what’s right or wrong, just an observation.

Indeed, it is very complex. I don’t actually have an answer to my thought experiment. If anything, it may simply represent how complex this can be. The ideal would be to understand and consider all that can influence our climate, rather than trying to simply describe it in simple terms. That, however, is sometimes easier said than done.

Current methodology between scientists in the field, or media, is to get feathers ruffled rather than entertain respectful debate.

Possibly, but some people seem to get their feathers ruffled remarkably easily. In fact, just pointing out what is clearly accepted science seems to do it. I’m not actually sure how to do it without ruffling feathers (well, I guess we could not tell the truth, but that seems like a poor strategy).

9. Raymond Arritt says:

Mr. Wilde, I looked at your web site and it appears that your understanding of how climate models work is incorrect. Most notably they do not “assume a generally static global energy budget with relatively little internal system variability.” If you would like a basic introduction to present-day climate models I would be glad to point you to some references.

10. Just so it’s clear who Stephen Wilde is: http://denierlist.wordpress.com/2012/03/13/stephen-wilde/

11. ATTP,
To me your questions are not questions about physical world. They are questions about the way people describe a history using words. How people choose to do that for a highly unrealistic scenario does not seem a productive question to me.

12. > If you’re just going to essentially deny the greenhouse effect, then staying away would be preferred.

Better yet, I’d suggest that Stephen follows on his conceptual physics at Science of Doom, eg:

Redirecting concerns like Stephen’s is the only way to ackowledge them properly.

13. Pekka,
Your comment does not surprise me. When I wrote this I thought “I bet you Pekka won’t like it”, but I did it anyway 🙂

How people choose to do that for a highly unrealistic scenario does not seem a productive question to me.

The point wasn’t so much about how they might describe it, but what they take away from trying to do so.

14. If someone wonders, why I haven’t written anything on Stephen’s thoughts, I can only say that I have done my share of that at Climate Etc long time ago.

15. Tom Curtis says:

Willard, Stephen clearly is not interested in acknowledging properly either logical or evidential points against his views. He certainly is not interested in formulating his views in a manner which makes them scientifically testable. Therefore we are under no obligation to “acknowledge” his concerns properly. Sometimes simply stating that drivel is drivel is the best approach.

16. John Mashey says:

Some “contributions” are more like withdrawals, and the short excerpt from Billy Madison sometimes fits.

17. pblackmar says:

I agree with all. With that said, even with accepted science there can be yet unrealized permutations that fit within the model and provide additional understanding or have some impact on the exact workings of mechanisms at play. In the Utopian void, lol, all would simply say let me consider that and study it for a while and will get back to you after that time. Unicorns may appear first as it relates to AGW.

18. > Therefore we are under no obligation to “acknowledge” his concerns properly. Sometimes simply stating that drivel is drivel is the best approach.

I would argue that it never is the best approach, as it prolongs something that is best redirected elsewhere. Having the same food fights over and over again in every blogs in unsustainable. The Internet will be owned to conceptual theoreticians like Stephen and other kinds of freedom fighters as long as we don’t redirect arguments in their proper discussion threads.

Equivalence classes are a powerful weapon.

19. William,
I’m somewhat surprised that more haven’t selected that.

20. You’re surrounded by sycophants, only I dare speak truth to power 😉

21. BBD says:

B*ll*cks!
🙂

22. Marco says:

42.

23. John Mashey says:

This relates to ATTP’s recent Salby post.
Stephen WIlde was a frequent supporter Salby’s pseudoscience, withcomments spread across various blogs, such as Climate, Etc, WUWT, Tallbloke’s Talkshop, WUWT again, See also writings at Climate Realists (sic), i.e., him + Piers Corbin + Hans Schreuder.

24. Vinny Burgoo says:

I would have said ‘3’, but then I don’t understand this sentence: ‘Also, imagine that this happens at a time when the increase in temperature exactly compensates for the increase in anthropogenic forcing (and associated feedbacks), so that the system is again in energy balance.’

And I was confused by the main question, too. ‘Is the warming?’

Does that include historical warming? Or did you mean ‘Is the current warming?’ or ‘Is the forcing?’?

Hard work, these hypotheticals.

25. Vinny,
You might have just illustrated the point 🙂 Possibly a point I was getting at is that there is a difference between what might be causing us to warm at this moment in time, and the reason why – now – we are warmer than we were. So, for example, there may be many factors that are influencing the rate at which we are warming at the moment (or this decade), but the reason we are warmer now than we were 100 years ago is almost entirely anthropogenic.

26. BBD says:

I’ve never been entirely clear how those arguing for a large natural component to modern warming square this with its implication – that the climate system is moderately sensitive to radiative perturbation. How, then, can the forced response to increased GHGs be much lower than expected?

27. Michael 2 says:

As you have described the scenario only #2 fits.

28. DocMartyn says:

What do you mean by ‘energy balance’?
No matter what you do, for a spinning planet, in an elliptical orbit around a star you will find that over the course of an orbit the energy into the system will be essentially equal to the energy out of the system.

29. Re : DocMartyn, [Mod: Be nice, please] I think what he means that if the system is in temperature equilibrium, the incoming and outgoing energy fluxes are ‘balanced’. If the temperature of a radiating (absorbing) system is either rising or falling (neglecting internal heat generation sources independent if incident energy flux) then the system is out of balance, At that point it is continuously warming or cooling. It has little to do with the orbital parameters. Although those parameters may be changing continuously, the energy imbalance is both instantaneous, and continuous. With respect to the Earth, any changes in energy flux are rapidly distributed across the planet by … weather, which has more to do with axial tilt and rotation than it does with elliptical orbits, since the orbit of the Earth is nearly circular. We know our planet is out of energy equilibrium because we have integrated those fluxes over many many orbits by now and have measured the surface temperatures to a fairly high degree of precision. All that remains now it to quantify the ice sheet masses and mass changes to such a high degree of precision (coming soon) and extend those measurements to the deep ocean (also coming soon) but certainly we have enough information on hand to be able to approximate most of the forcings. Carbon dioxide greenhouse gas forcing happens to be the largest and easiest to model. Water vapor and clouds will likely require a bit greater modelling skill and computational resources, and possibly the need for extraterrestrial (extrasolar) planetary observations and modelling, and that skill will also be soon in coming, but that will likely not change the fundamental result that if we want to preserve our ice sheets and temperate interglacial climate, we need to change the CO2.

All that being said, the fact that right now periapsis occurs near the southern hemisphere summer where most of Earth’s water resides is probably fortuitous, but even that changes over time. You should be more considerate of the fortuitous circumstances of the planet of your birth, and more mindful of how those circumstances can be changed on relatively short geological timescales.

30. DocMartyn says:

“We know our planet is out of energy equilibrium because we have integrated those fluxes over many many orbits by now and have measured the surface temperatures to a fairly high degree of precision.”

Have we? I suspect that you are being economical with the actualité.
Any point on Earth typically undergoes daily and seasonal temperature changes; the temperature changes as a function of various fluxes. It is not ‘in balance’ at any particular place or time, but the whole system is at steady state over time, through a full year (as influx is partly a function of distance from the sun).
I do no believe that one cannot state that the influx and efflux of energy from the system are dissimilar, with any degree of precision, to be in a position to state that the system is ‘out of balance’. The various estimates of the fluxes are just too inaccurate to compare the integral of influx and efflux. However, given the Blog title and that his is not my field, give me the integrals of the fluxes over the last five years.

The use of the term ‘energy equilibrium’ really should not be used in the description of the system at all; it is clearly not and has never been an equilibrium.

31. Raymond Arritt says:

It just happens that a good overview of this topic was published recently. See “Earth’s energy imbalance” by Trenberth et al., J. Climate, http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00294.1
If you do not have full access the abstract is nonetheless useful.

32. Have we?

Yes, we have, quite independently of your denial of that reality.

The use of the term ‘energy equilibrium’ really should not be used in the description of the system at all; it is clearly not and has never been an equilibrium.

Indeed it hasn’t, unless you are some kind of absolutist. The correct description would be relative equilibrium. Right now the system as we know it is grossly out of equilibrium, to the tune of an average of roughly a half a watt per square meter. That is a LOT of energy on short timescales, when averaged over the surface of the earth, the complete set of orbital parameters of the earth, and against solar irradiance. On decadal timescales it is fatal to the climate as we know it. The only other thing we know of that exceeds that are supervolcanoes and asteroid strikes.

I’m not worried, they’re your kids and grandkids, not mine. I suggest you start here.

33. DocMartyn,

No matter what you do, for a spinning planet, in an elliptical orbit around a star you will find that over the course of an orbit the energy into the system will be essentially equal to the energy out of the system.

No, as others have pointed out, you would be wrong if you thought that.

34. uknowispeaksense says:

2, 5, 6b*

6b. Stop writing posts that do make sense but just confuse most people.

35. We can have a cyclic fluctuation around an increasing trend line such that we can say that the increasing trend line is determined 100% by property f and 0% by property g but that the fluctuation around the increasing trend line is determined 0% by property f and 100% by property g. To see a very simple example of this via a graph having very roughly the staircase-like shape of the global warming graph since the late nineteenth century, go to
https://www.desmos.com/calculator

and enter

sin(x) + x

and explore this function of x. If this does not work, then sometimes just typing this at Google works. I got this page:

Notice that we can say that that the upward trend is determined 100% by function f(x) = x and 0% by function g(x) = sin(x) but that the fluctuation around the upward trend is determined 0% by function f(x) = x and 100% by function g(x) = sin(x).

Suppose we let f be anthropogenic causes (greenhouse) and g be natural causes. Then it should be clear that we can say that “the warming” defined to be the upward trend is 100% anthropogenic and 0% natural.

Of course, if the “the warming” is defined to be the “steeper parts” of the fluctuation around the upward trend, then this 50-50 talk is relevant, and talk about what is causing the fluctuation is relevant, but so what? Isn’t what is causing the upward trend and what we can do about it the only thing that’s really relevant to the really important topic of the future welfare of humans and other species?

36. pblackmar says:

So when I read this article and having no background in this field I have to wonder about it’s claim. Any thoughts to share? Thanks
http://www.cdapress.com/columns/cliff_harris/article_1472eee4-8cd8-5b2b-94cb-78da3ca4493f.html

37. pblackmar,
Seems to be complete nonsense. This comment in the article

The volcanic ash emitted into the Earth’s atmosphere in just four days – yes FOUR DAYS – by that volcano in Iceland has totally erased every single effort you have made to reduce the evil beast, carbon. And there are around 200 active volcanoes on the planet spewing out this crud at any one time – EVERY DAY.

Volcanic CO2 emissions are – today – about 100 times less than our own.

Again this is wrong

I don’t really want to rain on your parade too much, but I should mention that when the volcano Mt. Pinatubo erupted in the Philippines in 1991, it spewed out more greenhouse gases into the atmosphere than the entire human race had emitted in all its years on earth.

Again wrong. You can look up the numbers yourself but according to my search Pinatubo emitted 42 million tonnes of CO2. We’re currently emitting about 30 billion tonnes per year.

38. pblackmar says:

looking for a little help with this http://www.cdapress.com/columns/cliff_harris/article_1472eee4-8cd8-5b2b-94cb-78da3ca4493f.html

Is it pseudo science as you call it, BS as some others may or does it have some merit. Thanks for the input

39. It has no merit, as far as I can see.

40. pblackmar says:

Awesome, thanks

41. pblackmar says:

42. mircea says:

Hi,
I would definitely say case 1. The warming is all natural and in this particular thought experiment CO2 actually cools the atmosphere. Here it is why I think so:

C1*Integral_to_t1(co2_e)dt + C2*Integral_to_t1(Solar_e)dt = C1*Inegral_to_t2(Co2_e)dt = C3*Integral(DeltaT(exp 4))dt + C4

where t1 is the moment the solar stops being a forcing. t2 is a moment in time later than t1 (but not too much). Solar_e and CO2_e are the forcing at a certain moment and DeltaT is the difference in temperature at the end of the solar cycle. C1, C2, C3 and C4 are constants.

C2*Integral_to_t1(Solar_e)dt – is always greater than 0 (solar doesn’t cool)

Results:

C1*Integral_to_t1(co2_2)dt = C1*Integral_to_t2(Co2_e)dt – C2*Integral_to_t1(Solar_e)dt

Results:
C1*integral_ti_t1(co2_2)dt < 0 (for a t2 not too far from t1)

Results:
As per the thought experiment the warming is 100% natural and CO2 has a cooling effect. Also the CO2 impact is not linear in time and is function of solar forcing.

Where am I wrong?

Thank you!
Mircea

PS
I was extremely busy these few last months and this is why my seldom commenting.

43. mircea,

Where am I wrong?

I don’t know where to start. Is it a serious question?

44. Tom Curtis says:

mircea, temperature is not heat content. Therefore integration of forcing over time to determine temperature is a (massive) error. Indeed, if temperature were a function of the integral of solar forcing relative to (for example) 4 billion years ago, then the Earth’s temperature would climb continuously, and have done so for all of the last 4 billion years.

45. BBD says:

pblackmar

If you want to understand the climate system better, you can go to SkS. Here’s an article from that site on volcanoes and CO2.

Cliff Harris is very clearly not a climatologist, as he claims, but a private weather forecaster, newspaper columnist and contrarian with a sideline in chemtrails, no PhD and no publication history whatsoever.

In other words, a crank who is misrepresenting his academic credentials.

46. mircea says:

Hi,

Yes, it’s a serious question.

Tom, I am not integrating forcing to get the temperature. That Integral of forcing (delta energy in) over a time t is equal with energy out (C3*Texp4) – Texp4 is T exponential 4. I also added a C4 constant to allow for eventual lags.

The equations used in my previous post are the classical equations used in any simple model. I am wrong somewhere, but where?

Thank you!
Mircea

47. Mircea must be a follower of Tisdale, Carter, Salby and all the other busy “integrators” out there that are integrating mounds of cr@p that no one will touch with a 10-foot pole.

It bears repeating that it takes more time to weed through incorrectly formulated equations than it does to follow an elegant derivation. That’s why physics TA’s are given the job of grading homework assignments and exams. A D-student is given lots more of the TA’s time to figure out what the student did wrong and to sincerely help them understand their mistakes.

No one is paying us here, so you get what you pay for Mircea.

In retrospect, I wished every student was A+. Grading would have been a breeze.

48. Mircea,
I think if you want to do what you’ve done you’d need to do something like this.

The heat content of the climate system is around $10^{24} J K^{-1}$. Therefore the relationship between temperature and energy is

$dT = 10^{-24} dE$.

The energy is determined by the change in flux, so that

$dE = 4 \pi r^2 dF dt = 4 \pi r^2 (dF_{solar} + dF_{anthro}) dt$.

Then you could develop a simple model based on (where $T_o$ is the initial temperature)

$T_n = T_{n-1} + dT = T_{n-1} + 10^{-24} 4 \pi r^2 (dF_{solar}(t) + dF_{anthro}(t)) dt - 4 \pi r^2 \sigma (T_{n-1}^4 - T_o^4) dt$.

You could then integrate that to get how the temperature changes with time.

The problem with that is that it ignore feedbacks, which you could include by adding something like $dW = 4 \pi r^2 \alpha (T_{n-1} - T_o)$ with $\alpha$ around 0.5 to the equation above.

At the end of the day, though, I don’t think you need anything quite as complicated as that. The point I’m trying to get at is that however we warm, if at the end of some time interval the only change in forcing is anthropogenic, then the reason we’re warmer is because of anthropogenic influences, even if some other process contributed to the warming itself.

49. On the same bat-channel, at a previous bat-time:

Well… the 0.106 per decade that represents 100% anthropogenic warming is aprox 62% of the 0.171 warming per decade 1975 – 1998. If one plays with the tolerances then it can get that 100% anthropogenic warming is under 50% of total warming. This is Judith argument, if I understand it correctly, against the 95% confidence.

Am I wrong ?

https://andthentheresphysics.wordpress.com/2014/01/23/i-also-dont-get-judiths-logic/#comment-12670

The “am I wrong?” is called an anacoenosis, BTW:

http://rhetoric.byu.edu/Figures/A/anacoenosis.htm

50. anoilman says:

Willard, or is it Nerd Sniping?
http://xkcd.com/356/

51. BBD says:

ATTP pro bono and on a Bank Holiday too. Please give the man a chocolate digestive biscuit and a cup of decent coffee [print and present to nearest idle family member].

52. mircea says:

Hi WebHub,

If you know than show me an elegant derivation of the solution to this thought experiment. It’s easy to say oh I know but I don’t tell. I do not understand how solar forcing plus c02 forcing for a period of time gets to be equal with the co2 forcing at the end of that time without some cooling mechanism taking place during that period of time. What is compensating for the solar extra energy ?
The equation I used is really simple and classic, If you are so good as you say, it should have taken you less time to tell me what is wrong than to write your nice but not helpful post

Thank you!
Mircea

53. mircea says:

Hi Willard,

I am not expert in these… I am an flight engineer and my expertise are flight simulators. I am interested in understanding the subject of climate change but not at an expert level. I like to read this blog because it raises issues that are challenging for me and I learn new things. When I do not understand I raise a question. Anders and Tom especially were always very nice and answered.
The thing is that Anders and Tom and others know much more than me in this subject. When my conclusion differ from them there are 99% chances that I am wrong somewhere in my rationale.
In the same time, my opinion is that there is a certain sensitivity (which I understand) in this blog when questions challenging the consensus are raised. For this motive I put “where I am wrong?” line, to show that I do not assert that I am right and I do not want to debate, I just want to understand the issue. I have no qualms to admit that I am wrong … Actually my first presumption is that I am wrong …

Thank you!
Mircea

54. Mircea,

Well, AT did the equivalent of a TA crossing a big X over your homework assignment and then redoing it for you.

You should thank the TA and go study his clean derivation.

55. Marco says:

http://www.factcheck.org/2010/06/eruption-corruption/

There are some calculations (which, of course, I cannot find) that estimate that particular volcanic eruption on Iceland may have *reduced* CO2 emissions, because air travel was significantly reduced for a while. Ironic, isn’t it?

56. mircea says:

Ander,

Thank you for the answer! I understand what you say in the equations (I might say that they are close to my extremely poor written ones) but…kill me if I understand where the extra solar energy goes if not in temperature increase.

If at initial time t0 there is only CO2 increase than we get a temperature increase T1 at a certain time t1. Keeping the CO2 constant will result in constant temperature for a t2 relatively close to t1 so we can neglect the feed backs for the interval t2-t1.
Now if we also have solar forcing until time t1 and the temperature is still T1 at the end of this period and we had only 2 forcings during this time (co2 and sun) and if sun is always positive then the only conclusion I can see is that for the interval t0 – t1 the co2 forcing should have been negative up to the maximum of the solar forcing increasing slowly then while solar forcing decrease.

If the above are correct than the answer is 1. Natural warming because during the interval t1-t0 CO2 not only didn’t warm the system but it cooled it (I am talking about your thought experiment here not what happens in real life).

Mircea

57. mircea says:

WebHub Telescope,

You are funny 🙂 I looked at your models, nice job!

Mircea

58. Mircea,

Thank you for the answer! I understand what you say in the equations (I might say that they are close to my extremely poor written ones) but…kill me if I understand where the extra solar energy goes if not in temperature increase.

Actually, I think I made a mistake, which I think I’ve now corrected (forgot about the negative Planck feedback). You’re right, though, that I think you can cast it in the same form as yours.

I’m afraid I don’t follow the rest of what you’re saying, though. Here’s the thought experiment expressed differently. We start at time $t = 0$, with temperature $T = T_o$, and with the system in thermal equilibrium. At some later time $t = t_1$, the system is back in thermal equilibrium, the temperature has increased to $T = T_1$, but the only net change in radiative forcing is anthropogenic. There is no net change in solar forcing.

My answer to the question would be that the reason it is warmer at time $t = t_1$ is entirely anthropogenic. However, during the period that it was warming it was warming due to both anthropogenic and solar influences. I don’t see how you get that the anthropogenic forcing produced cooling.

59. mircea says:

Yes, now it makes sense. If in the thought experiment the temperature increases above T1 during time interval t1-t0 than yes at the end we can say that the increase at moment t1 is 100% due to CO2. Now I can start working on my sims in peace 🙂

Thank you!
Mircea

60. dana1981 says:

2

I keep following links over to Curry’s on this subject, and I really need to stop. She tries so hard to justify her ’50/50′ natural/anthropogenic belief, but her arguments are so nonsensical, it’s just painful to read. Just as one example she keeps talking about how decadal internal varability needs to be considered when attributing warming since 1980 and it only averages out over longer timeframes. But the IPCC attribution statement is for the warming since 1950! Really every argument she makes seems to be based on little more than inflating the uncertainty involved.

61. Steve Bloom says:

As an area of study, uncertainty seems to lend itself all too well to just making stuff up.

62. Steve Bloom says:

Anders, the OP looks like it still needs a reference to the Planck feedback, maybe by a brief mention of what would happen to the heat from a temporary increase in solar forcing if nothing else changes. More generally, I think your terminology needs straightening out. This phrasing e.g. will be very confusing to someone not already familiar with the subject, noting the two different senses of “increase”:

Afterwards, we fix our emissions to maintain, but not increase, this higher atmospheric CO2 concentration. This increase will produce a change in anthropogenic forcing.

Also:

Consider also that at the same time the Solar forcing increases by an amount greater than the increase in anthropogenic forcing. Given these two increases in external forcing, we will warm and – one might argue – that we will be mostly warming because of the change in solar forcing.

What’ does “one might argue” imply? Not that one might reasonably argue otherwise, I hope. Also, if the amount of added solar forcing is only a little greater than the anthro forcing, then it’s not going to be “mostly,” rather it will be in proportion.

Finally, I know what you’re trying to say here, but I don’t think you said it:

Now imagine that at some point in the future, the Solar forcing drops back down to what it was at the beginning, so that there is now no net change in solar forcing. Also, imagine that this happens at a time when the increase in temperature exactly compensates for the increase in anthropogenic forcing (and associated feedbacks), so that the system is again in energy balance.

The solar forcing will have recently increased the temperature, and it sounds as if you’re trying to refer back to that.

63. Rob NIcholls says:

Dana, I find Curry’s blog bewildering, but probably for different reasons. It’s difficult for an amateur like me to assess the veracity and significance of many of the things that Curry says. In my uninformed opinion I’ve never seen anything written by Curry that (even remotely) seriously challenges the IPCC’s position, but sometimes it takes me ages to assess what she’s saying (and I’m very grateful for the time experts have put in to explaining the flaws in Curry’s arguments). I have tried to keep an open mind and keep looking for some sign that there is something really important hidden away in Curry’s arguments, but there comes a point where it’s wasting too much of my life; purely on the basis of Curry’s written testimonies to US Senate Committees, the contents of which seem really poor to me, I should probably give climate-etc a miss in future.

64. What these people are doing, right up to established climatology professors, is engaging in a theoretical geoengineering exercise to cover up a huge and glaring CO2 initiated global energy imbalance. In my view, this is highly unethical and somebody need to start complaining about this.

65. Dana,
Yes, I’m slightly at a loss for words. The 50:50 argument is pretty poor, but any attempt to suggest that what Salby is saying is “interesting” is going to be pretty hard to justifiy.

Steve,

As an area of study, uncertainty seems to lend itself all too well to just making stuff up.

Yes, the “it’s possible, therefore probable” school of statistics. I’ll have to think about your other comment. You may well be right – I didn’t claim that this thought experiment wasn’t going to be confusing 🙂

66. Rob,

It’s difficult for an amateur like me to assess the veracity and significance of many of the things that Curry says.

I think that is the problem. It’s quite hard to argue against what Judith says because it doesn’t always make sense, but if you simply respond with “that’s nonsense” you get accused of not engaging with the argument. So, those who may not understand this all that well, might get the impression that those arguing against what Judith is saying are just being mean and unpleasant, when – in fact – the only sensible response is “WHAT?”.

67. anoilman says:

Fear Uncertainty and Doubt (FUD) is the bread and butter of the denial community.

They don’t have to make sense. They just have to make some off base comments JAQ a bit, and pretend like they are for real.

68. Dana said:

She tries so hard to justify her ’50/50′ natural/anthropogenic belief, but her arguments are so nonsensical, it’s just painful to read.

Like this one?
“Over multiple centuries, all of this might be a wash, but not for multi-decadal periods”

That one got her into a trick-box. Multiple centuries and multiple millenium are where the natural variations in warming will start to appear, due to orbital changes, etc. Multiple decades are where all the ENSO, TSI, volcanic and even her own stadium waves cancel out.

Remember, all she wants to do is feed her Uncertainty Monster. Spreading FUD (as OilMan pointed out) is a good thing. People read this stuff, see dissent, and therefore believe these issues have not been resolved.

69. Joseph says:

I think the reason Curry is promoting this 50/50 argument is because she wants to defend the Stadium Wave theory which suggests that the up and down fluctuations of temperature in this century and the last are significantly impacted by the proposed periodic cycle. Whether her theory has any validity, I will leave to those who have more expertise than I do.

70. Come on guys, Judy’s 99-1 argument ain’t that far from the 100-0 one!

71. JCH says:

Somewhere in another thread here izen (not sure of the spelling) left a brilliant comment about cycles. Wish I could find it.

72. Tom Curtis says:

Mircea,

In the simple thought experiment, we have three significant time periods:

t(-1) → t(0)
During this time period, energy out matches energy in and both are unchanging (averaged over the annual cycle).

t(0) → t(1)
During this time period, energy out is less than energy in, as a result of which temperature is increasing. Because energy out is a (complex) function of temperature, that means energy out increases over time, while energy in is constant (having changed at t(0) precisely. Note that because energy out is less than energy in, over this period the integral of energy out diverges from the integral of energy in. Therefore the third equality in your original system of equations does not hold.

t(1) → t(2)
During this period, energy in drops back to the original energy in during t(-1) → t(0) (CO2 modulates energy out rather than energy in). Further, energy out equals energy in as in t(-1) → t(0), so energy out during this period equals energy out in the initial period as well. However, surface temperatures have still risen to compensate for the reduction in energy out due to the increased CO2 in the atmosphere.

It is important to note that as set up, surface temperatures in the scenario never exceed the equilibrium temperature for the change in CO2 concentration in the atmosphere. Therefore, indexing forcings by the terminal point of their operation (in this scenario), and defining all forcings with respect to the initial period, we have:

F(0;solar) = F(0;CO2) = 0
F(1;solar) > F(1;CO2) > 0
F(2;solar) = 0
F(2;CO2) = F(1;CO2)

Using the climate sensitivity factor, λ, with units of W/m^2/K, and defining change of temperature with respect to t(0), we can add formulas for temperature as well:
λΔT(0) = 0
0 < λΔT(x) < F(2;CO2), where 0 < x < 1
λΔT(2) = F(2;CO2)

Returning to your system of equations, and with the above formulas clearly in mind we, we see that the integral of F(1;solar) + F(1;CO2) over t(0) → t(1) equals the integral of F(2;CO2) over t(0) → t(2) if and only if the integral of F(1;solar) over t(0) → t(1) equals the integral of F(2;CO2) over t(1) → t(2). However, the period t(1) → t(2) is a period of arbitrary length introduced just so we can describe the final equilibrium condition. Therefore it cannot be the case that your first equality is an necessary condition of the scenario.

Therefore, once again, you cannot determine equilibrium temperatures by integrating energy flows. Even Ander’s superior attempt fails because it assumes that the ratio of system energy content to surface temperature is a constant, which equates to an assumption that temperature increases at all depths of the ocean are identical – a condition known to be false.

73. JCH,

Perhaps this comment:

While Dr Judith Curry’s defensive of her position on how much of the measured warming could be natural/human seems to miss the point of john N-G’s arguement, the subsequent discussion is… odd.

The idea that natural cycles are thermodynamically neutral by definition is ignored, and even longer natural cycles are proposed as a solution to the neutrality of a 60yr cycle having an effect on a trend caused by a forced energy imbalance. Despite the paucity of evidence for such cycles and the general observation that the longer the cycle the slower and smaller any changes.
The recovery from the LIA is quoted as an example of a natural variation that is not zero-sum in terms of energy, conveniently ignoring the fact that the LIA and the recovery from it are not considered to be natural variations, but due to changes in forcings. {sun output and volcanoes}

[…]

[A] natural variation may briefly negate an external forcing causing an energy imbalance, or at least negate the air surface temperature component while amplifying the ocean heat sequestration element.

https://andthentheresphysics.wordpress.com/2014/01/23/i-also-dont-get-judiths-logic/#comment-12696

74. JCH says:

Willard – that’s the one. I’m reading through the thread now. Thanks.

75. Steve Bloom says:

Joseph, the key thing to know about the stadium wave theory is that it’s not a theory at all since it lacks a physical mechanism. IOW, it’s an exercise in curve-fitting. That doesn’t require expertise to see. What does take a little expertise (very little, really) is to realize that for it to be true there would have to be large multi-decadal swings in either cloud cover or ocean heat sequestration. Both of those seem highly implausible, but Judy happily dodges having to address them precisely because she has no physical mechanism.

76. Regarding the Stadium Wave, the strongest physical connection is via the correlation with multi-decadal Length of Day (LOD) variations.

The group at JPL lead by Dickey link large scale angular momentum conservation with the slowly varying global temperature change. It is definitely intriguing to find out what is happening here. As of 2011, they don’t think it is caused by ocean transport, based on not enough mass redistribution.

[1] J. O. Dickey, S. L. Marcus, and O. de Viron, “Air Temperature and Anthropogenic Forcing: Insights from the Solid Earth,” Journal of Climate, vol. 24, no. 2, pp. 569–574, 2011.
PDF = http://journals.ametsoc.org/doi/pdf/10.1175/2010JCLI3500.1

and then look at this paper, this is some known stuff but the details are an eye-opener

[2] Le Bail, Karine, John M. Gipson, and Daniel S. MacMillan. “Quantifying the Correlation Between the MEI and LOD Variations by Decomposing LOD with Singular Spectrum Analysis.” Earth on the Edge: Science for a Sustainable Planet. Springer Berlin Heidelberg, 2014. 473-477.

77. My rationale on ideas like the Stadium Wave goes as follows in the spirit of exploratory research:

1) There’s enough indication of variability with 60 year (quasi) periodicity to warrant looking at the issue more carefully.

2) If it’s a real periodic effect it must be based on a sequence of phases, each of which has its signature.

3) The Stadium Wave of Marcia Wyatt and her collaborators is one proposal of such nature, invented probably mostly through a search of potential signals in a large variety of empirical time series.

4) When such a sequential combination is found in the data, it’s time to think about possible physical mechanisms. In the best case a mechanism is found, and further tests can be devised to confirm its role, in the worst it appears certain that the required coupling is missing. My understanding is that the Stadium Wave hypothesis is or could be modified to be between these clear cases.

Exploratory research is a part of proper science, much of science has gone trough that phase, but often the ideas found turn out to be of little consequence.

78. Pekka,
Of course I agree that these things are worth doing. One of my concerns, though, is whether or not the datasets extend sufficiently far back and are sufficiently reliable to robustly detect 60 year variability. Additionally, it seems that one should be removing the forced component. Not only does it seem possible to develop a model in which the forced component plus ENSO can match the temperature record (in which case there isn’t a long-term natural cycle) but also, there doesn’t seem to be a unique way of removing the forced component, so the natural cycle one detects presumably depends on that choice. This seems to be an issue with the AMO. It’s defined as a linearly detrended sea surface temperature. This only represent internal variability if the forced component is truly linear, which it probably isn’t.

The other more handwavy issue I have is what could be driving a 60 year cycle. I can’t think of anything. Also, given the influence of volcanoes, solar and even ourselves (John Mashey would be pointing out the work of Ruddiman who argues our influence can go back 100s of years) how has such a cycle been sustained?

79. ATTP,

I think that the formulation I chose accounts for your concern, at least I formulated it as I did for exactly that reason.

In the exploratory phase one should not limit the analysis to some specific way of preparing the data or to some specific way of removing a component that’s known to exist, but is not known precisely with little quantitative uncertainty.

The time to be more critical is in presenting conclusions from the whole process.

80. Pekka,
Indeed, I wasn’t suggesting otherwise. I was simply expressing my concerns in a slightly different way. I should add, though, that even though you acknowledge these issues, many who promote these 60 year cycle-type ideas, seem not to.

Tom,

Even Ander’s superior attempt fails because it assumes that the ratio of system energy content to surface temperature is a constant, which equates to an assumption that temperature increases at all depths of the ocean are identical – a condition known to be false.

I forgot to mention that in my thought experiment the planet is an ocean world with an ocean only 100m deep 🙂

81. Steve Bloom says:

The time to be more critical is in presenting conclusions from the whole process.

Of course, but Judy specializes in presenting uncertainty, not conclusions. Ever so much easier.

I have to say that these discussions make me think about setting up a competing blog: “..and Then There’s Paleoclimate.” Physicists do like to talk physics, and by all means should, but too often it distracts them from the big picture.

82. Steve Bloom says:

I forgot to mention that in my thought experiment the planet is an ocean world with an ocean only 100m deep 🙂

Srsly? Well, that would fix one of the concerns I raised.

83. anoilman says:

Anders… 100m ocean? That decides it for me. 6.

SIX!

84. Steve Bloom says:

At least it’s not 6!. 🙂

Interesting stuff, Web. I had seen something on this years ago but forgotten about it. But as the last sentence of the abstract of the linked one says:

In all three cases, their signals would be much smaller than the anthropogenic greenhouse gas effect on Earth’s radiation budget during the coming century.

…and Then There’s Paleoclimate.

85. I agree Steve. The Stadium Wave as mapped to the LOD caused a variation of +/- 0.1 C over the last 130 years, and averages to zero. That is in comparison to an upward move in land temperature which is greater than 1.2C over that same time span.

86. dana1981 says:

Gavin Schmidt does an excellent job explaining Judith Curry’s confusion on global warming attribution and her 50/50 nonsense at RealClimate: