Discussion > That CO2 thing again..
SoD
I think the problem here is that we are not simply arguing at cross purposes but past each other.
What RR and I are saying (and I think I've him/her right) is that, first off, the GCMs are plain wrong. They are consistently over-estimating warming and have been doing for long enough for this to become evident enough for us to say that at their current state of development they are useless.
The theoretical effect of CO2 is to raise temperatures by 1.2C for each doubling in the absence of other forcings or feedbacks.
One natural forcing is the recovery from the LIA, the precise effect of which is probably unknown but put a figure on it and it reduces the temperature increase since the mid-1800s which can be attributed to CO2.
The CO2 concentration of 280ppm began to increase (we are told) at roughly that time and has now reached 400ppm.
The actual temperature increase since the mid-1800s has been ~0.8C which given that the effect is, we are told, logarithmic looks to be about right but allowing for the LIA recovery, perhaps the CO2 contribution is a bit less
So by the time that CO2 concentration reaches 560ppm the average earth temperature will have increased by about 0.5C compared with today — absent other feedbacks of course.
How long it will take to reach 1020ppm is anyone's guess.
And that really is it, isn't it? We're talking about an average temperature increase over perhaps the next 50 years of less than the difference between what it was when I got up this morning and what it was when I finished breakfast.
You can argue all the equations you like; real people are only concerned with what is happening in the real world and that is precious little. Certainly not enough to warrant the time and money that is being wasted on the science and the hype that is surrounding it.
Mike Jackson
Martin A
What a silly thing for her to say.
I am not arguing from authority, I am arguing from the data .
The warmingratw since accurate records began is 0.6C/ century.
Look at the GISS data and you will see a green confidence limits bar for the 21st century data of +/- 0.6C.
The quickest way to estimate the time scale of significant change is to work out how long it would take for confidence limits to no longer overlap, is a difference of 0.12C. At the long term warming rate of 0.06C/decade that would be twenty years.
Vicki Pope strikes me as pessimistic. 2004 had an anomaly of 0.51, so she is projecting 0.81 for 2014. That is twice the maximum warming rate for 1975 to 2005. Some people are expecting 2014 to be a record year. We'll know in January.
Entropic man
Yes, SoD, you are right, we are – yet again! – arguing over the nap of the cloth. I have no beef with radiative transfer, as it is easily verifiable in a laboratory; whether it is significant in the field is debatable. What I query is that this is the “control knob” of climate, with CO2 as the key component; I suggest that the evidence indicates that this is not so. Others, it would seem, in desperate attempts to keep with the meme, want to declare that all observations are not correct, as you pointed out. Quite why we should discard the many, many measurements that disagree with the theory and cleave to those few that do, as well as adjusting historical records so that they fit, too. To admit otherwise is to admit, as Mike Jackson has pointed out, that the GCMs are wrong.
My “guess” (and I have not the wherewithal, ability or inclination to take it further) is that the whole scenario is considerably more complex than many are admitting; indeed, many seem to be ignoring perhaps the biggest component of the Earth’s climate – the Sun!
Radical Rodent
EM - I don't think it makes any sense to talk about "confidence limits bars" for a process whose statistical properties are essentially unknown and of which only a small sample is available. Predicting future climate from past records without a known statistical model is just guesswork.
Vicky Pope seems to have been shunted into a siding where she is not going to bring the MO further ridicule ("Head of Integration and Growth"). But she has held various senior positions "Head of climate change advice", "manager of atmospheric climate model development and evaluation". Her statements may have been silly but have to be regarded as the met office's view.
Apparently she got the 0.3° from a paper by met office researchers, possibly who had worked with Vicky as their manager.
http://www.sciencemag.org/content/317/5839/796
Martin A
"One of them, at least, seems to think that climate science has been reduced to a few precise analytical formulas." No, but some aspects of it clearly are. It is remarkable that some here continue to dispute energy flows despite seeming to have been immersed in the subject for years. As SoD's comment at the end of page 12 indicates, I think, the physics (the fancy equations) is known; rising CO2 causes energy to accumulate. That we cannot point to a surface temp record and see this fact unequivocally indicates the inadequacies of the record. The physics says the energy has accumulated and will continue to.
Raff
…rising CO2 causes energy to accumulate.In laboratory conditions, that is correct. Unfortunately, the atmosphere might not have the same conditions that can be imposed in a lab. Ah, but you do seem to agree with yet another point made: "Because climate hasn't warmed for the last x years, it clearly demonstrates that SST and lower tropospheric temperature measurements by satellites are clearly rubbish". You might say that the energy has accumulated and will continue to do so, reality, though, appears to be saying something completely different. “Therefore,” you might crow, “as all these theories are right, reality must be wrong!”
Radical Rodent
Martin:
people - perhaps like me - who don't dispute the physics of radiation, of gaseous expansion, and so on, but who think that the complexity of the carbon cycle system and of climate system has been greatly underestimated. And our ability to understand it has been both greatly overestimated and greatly exaggerated
Moi aussi. A bientot to SoD and thanks.
Richard Drake
Richard, move over on Martin’s bench and let me join you two… I suspect there may be a few others who will want to be counted with us, too.
Radical Rodent
SoD, my previous question is perhaps better described as being about how extra CO2 (or other GHG) affects OLR at different physical locations in the Earth's atmosphere (wrt both vertical and lateral distribution). More specifically, when/where the transported heat arriving at any given location (before it is lost to space) is significantly different than what would be the case in a simple ground-up, 1-D, radiative energy model. I don't see why why the globally-integrated effect of increases and decreases in OLR over all such areas must necessarily be greater than zero (i.e. warming). It might be in practice. I'm not arguing one way or the other, but curious as to how that can asserted with certainty.
I think you mentioned temperature inversions in an intervening post. That was partly what I had in mind.
michael hart
michael hart,
"..I don't see why why the globally-integrated effect of increases and decreases in OLR over all such areas must necessarily be greater than zero (i.e. warming). It might be in practice. I'm not arguing one way or the other, but curious as to how that can asserted with certainty.
I think you mentioned temperature inversions in an intervening post. That was partly what I had in mind."
The temperature inversions are over a short height- maybe 1km.
If you had a temperature inversion all the way to the top of the troposphere - or even half way up - then that would definitely change things.
If - for example - temperature vs height was a constant, there would be no inappropriately-named "greenhouse" effect at all. If temperature vs height was positive then the "greenhouse" effect would work in the other direction. More GHGs would cool the climate. (Of course, such a situation is currently thermodynamically impossible so take it as a thought experiment to give conceptual insight).
The main effect of increased CO2 takes place in the mid to upper troposphere.
Here is how I think about the problem:
a) if you know the surface temperature, atmospheric temperature profile and GHG concentrations you can very accurately predict the TOA flux
b) therefore, it is, I'd like to say "trivial" but let's say instead, "straightforward" with the appropriate grasp of theory and the HITRAN database of absorption coefficients - straightforward to show that more well-mixed CO2 will reduce OLR
c) if you don't know the surface temperature, temperature profile vs height and / or GHG concentrations then your calculation or prediction or whatever you want to call it, will have the uncertainty due to your prediction of those values,
So, increasing well-mixed GHGs reduces OLR - even for temperature inversions extending right through the boundary layer.
Another way to write the same piece of information is "the pre-feedback effect of increased CO2 of x% = a radiative forcing of y W/m2" and we can calculate these values.
What we don't know with any certainty is the post-feedback effect.
It is difficult to convey the key parts of the puzzle to people new to the problem. I was very confused myself after reading a few textbooks about many aspects of radiative transfer in the real atmosphere. It wasn't until I had done some RTE calculations myself that everything became crystal clear.
Science of Doom
Raff:
"As SoD's comment at the end of page 12 indicates, I think, the physics (the fancy equations) is known; rising CO2 causes energy to accumulate. That we cannot point to a surface temp record and see this fact unequivocally indicates the inadequacies of the record. The physics says the energy has accumulated and will continue to."
My perspective is slightly different. "All other things being equal" more CO2 will "unequivocally" increase temperature.
That's a standard physics line when you want to isolate one component.
Science of Doom
rising CO2 causes energy to accumulate. That we cannot point to a surface temp record and see this fact unequivocally indicates the inadequacies of the record. The physics says the energy has accumulated and will continue to.
Sep 4, 2014 at 5:03 PM | Unregistered Commenter Raff
I had thought that 'models trump data' was just a joke. But I think Raff is serious.
Raff - 'the physics' is the analysis of a model; it is not the real thing. There will be effects in the real thing not included in the model and not fully understood. If the results of the analysis of the model do not agree with the data, the best you can say is 'there is something here that we don't understand'. To say that the disagreement unequivocally indicates that the data is wrong invites ridicule.
splitpin
Science of Doom
I am interested to know:
- what proportion of the Earth's radiation to space (ie photons that escape without further interaction with the atmosphere) originates in the stratosphere.
- how this proportion would change if the atmospheric concentration of CO₂ increased.
- how this energy radiated reaches the stratosphere (I presume by radiation from below if convection does not play a significant role).
- the effect emitting this radiation has on the temperature of the stratosphere (presumably it cools it, with greater cooling at lower altitudes).
I have looked at your website but did not find this information - perhaps I did not search thoroughly enough. If you would point me in the right direction, I'd be grateful.
Martin A
Martin A: now you are looking beyond the nap of the cloth, and wish to discuss what loom it was that the cloth was woven on! Let us move our concentration to the bigger picture in all this: DO the models fit the observations? If not, why should we give the models such credence? Should we not be expanding our search to find other factors that might have some effect on the climates? It is getting more like pantomime with regards to CO2: “It’s CO2 what did it!” – “Oh no, it didn’t!” – “Oh yes, it did!”
Radical Rodent
RR - Should we not be expanding our search to find other factors that might have some effect on the climates?
Yes. It would be interesting to see an explanation of what caused the little ice age and what made it come to an end.
I'm still interested in understanding the theory of atmospheric CO₂. In trying to understand something, I like to look at extreme or corner cases and see if I can make sense of those. Hence my question about radiation from the stratosphere.
Martin A
Martin A
Something to get you started researching the LIA.
Milleret al 2012 identifies a link between vulcanism induced cooling and the onset of the LIA. They also identify increased Arctic sea ice as a feedback which sustained the cooling.
Other hypotheses include the lack of sunspots during the Maunder Minimum , a sustained solar minimum.
Personally I would suspect a ropadope with both contributing. The MM coinxises with the peak of the LIA, but came too late to initiate it. Have fun! I would be interested to know what else you find.
Entropic man
Martin A
Incidentally, I doubt that a change in CO2 caused the LIA. There is a small drop in the CO2 curve from the Law Dome ice core in 1600.
Entropic man
EM - thank you. I said it would be interesting to see an explanation of the LIA rather than indicating any intention of investigating it myself. I'll leave it to others to determine the cause of the LIA but I'll be interested to read their findings. It will be interesting to look at the refs you kindly give.
I have always assumed that the CO₂ law dome dip was due to reduced natural CO₂ emission as a result of the drop in temperature. Or reduced natural absorption.
Martin A
Martin A
It is quite possible that the LIA drop in temperature produced the CO2 dip but it happened a lot more abruptly than these things usually do naturally.
Entropic man
Martin A,
For your comment of Sep 5, 2014 at 2:00 PM I don't have the answer to this question. I would need to fire up the Matlab model, and dissect the results. I'm travelling at the moment and don't have Matlab.
Science of Doom
SoD, If you were willing, in due course, to see what your Matlab model says, especially if you think the answer might be of interest to others, then I'd be grateful to learn what the answer is.
Martin A
Interpretation of the Arctic ice record demonstrates that over last 3000 years, Earth has experienced a fall in temperature from the Minoan period with blips up (but each to a lower level) through the Roman Warm Period, down again through the Dark Ages, up to the Mediaeval Warm period down to the Little Age and is now recovering.
Note that a 'blip' in these circumstances can last several hundred years!
Other historical observations such as Roman buildings, Mediaeval riches, Viking occupation of and departure from Greenland, Ice Fairs on the Thames etc. , broadly support this interpretation
Clearly, anthropogenic CO2 cannot be the source of the historic blips. What evidence have we for its impact on this latest warming phase? Until we understand past history, we are simply unable to rule out completely natural causes, which suggests that the impact of CO2 emissions is small.
I have no quarrel with the scientific observations of the ability of the CO2 molecule to absorb e/m energy in two narrow bands of the infra-red spectrum, but am wary of building enormously complex computer codes using this as the basis for describing the progress of the Earth's climate.
Present-day models are attempting to predict the future, in the absence of any credible ability to explain the past. From my own experience of modelling complex phenomena, this a risky business.
Ronaldo
Rinaldo
Yes, CO2 is not the only driver.
The best current description of Holocene temperatures is Marcott et al 2013.
The cooling since the Holocene optimum is mostly credited to gradual (and ongoing orbital changes reducing high northern latitude insolation. The LIA was probably started by vulcanism and sustained by an extended solar minimum ( the Maunder Minimum).
Most of the relevant variables have been generating cooling forcing during the 20th century, while CO2 has been warming. It could have been worse.
Beware of the logical fallacy of claiming that because anthropogenic carbon dioxide did not cause past natural changes it cannot cause change now.
It is like claiming that because your great grandfather could not use a computer nor can you.
Entropic man
But what caused the upward blips?
I love logical fallacies. My grandfather couldn't use a computer because they did not exist. I don't think that CO2 is any different now than centuries ago. Why did the Mediaeval Warm period arise and disappear?
Ronaldo
SoD thank you for doing your best to help our discussion. As you'll have gathered, there are a range of views being expressed on this thread.
** rhoda (who kicked it off but seems to have gone quiet) wanted (I think):
- (A) to understand some of the details of radiative transfer
and also...
- (B) to know what measurements have been/could be made to verify directly a relation between atmospheric warming and increased atmospheric CO₂
You have helped with (A) and pointed out that (B) can't be.
** people who doubt the whole idea that a bit of CO₂ in the atmosphere can affect things significantly and who express that view. Talk 'of 'back-radiation' confirms to them that the whole thing is nonsense.
** people who don't dispute that more CO₂ in the atmosphere reduces outgoing radiation but think that the eventual consequences have been greatly exaggerated and may even, on balance, be beneficial.
** people - perhaps like me - who don't dispute the physics of radiation, of gaseous expansion, and so on, but who think that the complexity of the carbon cycle system and of climate system has been greatly underestimated. And our ability to understand it has been both greatly overestimated and greatly exaggerated.
** people who cannot understand how other, apparently moderately intelligent, people do not accept that it has been established beyond doubt that emission of CO₂ poses great dangers. One of them, at least, seems to think that climate science has been reduced to a few precise analytical formulas.
Every time someone comes up with something about the last X years of climate history in the context of demonstrating what CO2 does or doesn't do...
Don't overlook that, years back, we were told, by climate scientists at top level, that we would see things in the near future that simply have not happened. I don't know for sure what is the explanation for that but I assume it is that their understanding of climate is much less complete than they had imagined.
Since the climate scientists told us that, within X years, CO₂ would cause things (eg "our children won't know what snow is", "temperature will have risen by 0.3 degrees by 2014") that have not happened, it's not unreasonable for us to think that the last X years of climate history at least tells us that their understanding of the effects of CO₂ is less complete than they had thought.
But if the idea is to win some kind of argument there isn't much point being here.
It's not an argument that anybody is going to 'win' but we'll no doubt carry on pointing out the flaws in the opinions of those we don't agree with. Thank you pointing us to the facts on radiative transfer.