Bishop Hill Reacting to Rose
Mar 18, 2013 Climate: Models Climate: Surface Climate: sensitivity In the wake of David Rose's Mail on Sunday article yesterday, Piers Forster tweeted that he was unimpressed with the article. I asked him if he would be willing to set out why in a bit more detail and this is his response:
It's fine to say that current models overestimate the last decade of warming. They clearly do, and as I say in my quote I think we can rule out some high sensitivity values because of this. But to do a far comparison you need to remove the effects of variability. Note also that some model runs also get the temperature evolution pretty right - although the majority don't. Even with a suggested ECS of around 2.5 C or so we can end up with a very significant climate change by 2100 if we don't do something - therefore I think the tone of the article in terms of its implications for the IPCC, climate science and the climate itself are all wrong.
He also sent the full quote that he gave Rose for his article, which gives some context.
Basically, the climate sensitivity has always been very uncertain. > estimates have put it somewhere between 1 to 5 C for a doubling of CO2. The IPCC best estimate has been around 3C. The fact that global surface temps haven't risen in the last 15 years, combined with good knowledge of the forcing terms changing climate over the satellite era: greenhouse gases, volcanoes, solar changes and aerosol is beginning to make the high estimates unlikely. Given this, i would put the best estimate using this evidence around 2.5 C. There are still uncertainties though particularly in heat going into the ocean, but climate sensitivities above 3.5C or so don't seem to fit. Keep in mind that this is only one line of evidence for quantifying climate sensitivity. Other lines of evidence have been able to firm up the bottom end. We now have good observational evidence for a positive water vapour feedback and even clouds, which have always been the largest headache in climate change, are beginning to be understood and a positive cloud feedback is looking more likely. This line of evidence helps rule out climate sensitivities below 2C. So I see it very much as a positive story that careful science ( and time) is helping to reduce the most significant uncertainty in climate science.
This thread will be tightly moderated for tone and relevance.
Reader Comments (187)
I think the Mail splash can be divided into three - the headline, which was incendiary, Rose's article which was pretty factual, and David Bellamy's piece at the bottom which would also have stirred the pot. I think many of the criticisms directed at Rose have been as a result of the headline (which was probably written by an editor) and by Bellamy's piece.
If climate sensitivity is 2.5 (I think it's probably lower) then most of the policy responses to date are far more expensive than the problem they purport to be addressing.
My comment to Piers Forster would be-
Don’t just tell us that there’s ‘good observational evidence for a positive water vapour feedback and even clouds’, get the proof out there for people to observe and discuss. Have some serious debates between the experts to hammer out latest thoughts on sensitivity. Stream them live. Take submitted questions.
[Snip -tone]
Good observational evidence for positive cloud feedback? Please can we have the references for this claim. Lindzen and Choi seems to refute positive feedback and several other papers. No evidence of troposphere 'hotspot' or increased water vapour. No evidence of SST increase nor of warming of the deep ocean.
Unsupported statements are not science.
I would back TinyCO2's comments. This is an important discussion. I've yet to see any discussion of the climate sensitivities that have been estimated by Shaviv and co-workers, whose latest paper suggests sensitivities markedly less than 2 degrees C per CO2 doubling and that there is very little evidence for any net positive feedbacks. Yet Piers Forster says he has good observational evidence that for positive water vapour feedback that rules these observations out. i.e. they are less than 2 degrees C.
What are Piers' views on the estimates of Shaviv and co-workers?
I thought the work by Roy Spencer et al showed that the feedback from water vapour/clouds was net neural or negative. Where is the evidence " a positive water vapour feed back or even clouds" has this evidence been published or scrutinised.
As others have said if Piers Forster has the evidence of positive feedback why has he not published it because until he does and people have had a chance to check it it is still so much pie in the sky.
[Snip - good point, but O/T here]
[Snip - O/T]
[Snip O/T]
We have had a rise in CO2 of about 40% in 120 years. The temperature has risen, but not steadily. It rose quite markedly 1920-1940, cooled 1945-1975, rose 1979-1998. This surely implies that there is natural variation.
Yet for a sensitivity (and linear response) of 2.5 we should see a rise in temperature of 1 ℃, more than the usual figure of 0.75 ℃. A sensitivity of 2 might be acceptable, if the entire rise is due to CO2, but the presence of natural variation must make up some part of that figure.
The other objection is that the rise in temperature in the Southern Hemisphere is nowhere near that of the Northern Hemisphere, being less than a third than that normally quoted for the north. I don't think you can make a valid case for a sensitivity above 0.6.
I don't see a good reason for a lower limit of 2 deg.
A number of observational studies are below 2 deg. And as they are observational, they include, whatever water vapour and clouds do.
(This very new one goes as low as 0.18 deg:
http://hockeyschtick.blogspot.com/2013/01/new-paper-confirms-findings-of-lindzen.html )
I would also think that the existence of a solar amplifier mechanism, for which there is spectacular evidence (some of which. according to Shaviv, with the best correlations of any variables in climate science), would strongly further reduce sensitivity.
http://kaltesonne.de/wp-content/uploads/2012/05/bond-et-al-2001.gif
[Snip - response to snipped comment]
[Snip - sorry, but I want the discussion to be about Piers' comments not about generalities]
Climate sensitivity has been at the centre of much of the disagreement, however we still do not seem to have made much headway.
Making vague statements like "This line of evidence helps rule out climate sensitivities below 2C.", doesn't really help the debate.
We need the supportative evidence to be published and criticised before we go back into the old scare meme "it could be really disasterous so let us spend massive amount of money now to cap emissions.
Rather than doing better science and having open debate before we spend the money!
Lovable Eccentric 70s TV Icon David Bellamy National Treasure Status (was).
Don't make into our first Skeptic Martyr..He don't need it .Extra CO2 plant and animal live is thriving.
[Snip]
Different people have different views on CS.
On a previous thread, I said
Another commenter, Entropic Man, said
Note that he quotes the coefficient multiplying the logarithm to three significant figures. I asked him where he got this stuff and he replied simply:
"I read the literature"
(Mar 11, 2013 at 3:13 PM)
I hope he will send the references he read to Professor Piers Forster. The Prof seems uncertain compared with Entropic Man's confidence in the precision of the formula above.
"We now have good observational evidence for a positive water vapour feedback and even clouds, which have always been the largest headache in climate change, are beginning to be understood and a positive cloud feedback is looking more likely."
As G.Watkins asks above, what is the evidence for that? I too, almost considered the quoted words to be those of someone trying to row-back from an untenable position.
Then he blew it. In the process of admitting that CO2 is not well modelled he appears to claim that they now have a handle on water-feedback and clouds? Gimme a break.
Latimer Alder, not saying it's perfect, but 'debate' is not the answer.
[snip - O/T]
And just supposing, at the end of the day, "variability" is all you've got. There are arguments (re-iterated recently) that there has been no gradual warming during the period 1975-1997 or between 1999 and the present but there was a step-change coincidental with (caused by?) the massive 1998 El Nino. There are papers flying around now that still argue that the net water vapour effect is negative. There are numerous other more (or sometimes less) credible hypotheses that down-play the role of CO2 to close to zero and argue cogently that "variability" is all you've got.
What then, Piers?
You can't just sit there and wave away the data and the hypotheses that don't fit and say "we have to remove the effects of variability" as if that made everything all right.
Without returning too blatantly to my hobby horse, how can I trust a centennial measure of anything being a constant when nobody here was able to suggest an experiment demonstrating climate sensitivity at any given place or time, including in controlled conditions in a lab? No, that's too difficult. Any fool can take a temp change over decades in the past and run the CO2 change through the formula and get a figure, but that figure is (arguably) otherwise meaningless.
Bishop Hill, would you be so kind as to ask Prof. Forster for some explicit examples/references of the "... good observational evidence for a positive water vapour feedback and even clouds...", as I'm sure this would be of great interest to those of us who frequent your blog.
[BH adds: Yes, I think that's a good idea]
[Snip]
I echo the above requests for evidence of water vapour and clouds having a net positive feedback.
I also question the 2.6C per doubling, as observation evidence suggests the models are bollocks:
Pre-industrial CO2 levels were about 265ppm and the current level is about 390ppm. Not a doubling but not far off.
The oldest instrumental datasets suggest temperatures have only risen about 1.5C in that time - NIKfromNYC's composite graph<\a> and much of that rise is due to the natural rebound from the Little Ice Age, and nothing to so with extra CO2.
As I stated on http://www.bishop-hill.net/blog/2012/12/19/climate-sensitivity-is-low.html a sensitivity on 1.6C would be a very good thing for most of the human population - 80% of us live in the northern hemisphere with cold winters and short growing seasons.
That said I maintain that CO2 sensitivity is about 0.25C per doubling at the most. e.g iirc, the decreased insolence due to just a 2% increase in cloud cover over the tropics and mid latitudes dwarfs the additional energy gained by the planet due to CO2 reflecting back outward IR.
The Mail is simply doing what the IPCC has done before. The Mail's headline graph is that published by the MET Office. It represents the state of play in the accepted literature. The work Piers refer to is apparently not yet in the public domain - and let's apply the peer-review cosh as well. So as the IPCC would tell us, Pier's work is at this stage irrelevant.
This is the frantic rowing back of hysterical war mists as they see they got it wrong.
In the future we can look forward to more 'of course we always knew this/that.....more money?"
[Snip - tone]
Its very hypocritical for "warmists" to be complaining about misleading headlines in newspapers, given the "Hockey Stick" , translating global warming to climate change - climate disruption etc. etc. etc.
People in the serious science community need to have a serious look at how the greens and environmentalist loonies are hijacking science, pushing propaganda and destroying the credibility of science overall.
The Polar Bears are dying etc springs to mind.
Misleading headlines and junk science seem to be allowed if its for the "cause" but woe betide headlines similar against the science....
This works both ways.
Discussion of water vapour feedbacks, with references, can be found in this section of the IPCC AR4 Working Group1 report
There's also this paper by William Ingram - while the paper is somewhat theoretical, William does explain the basis of his argument, and also provides other references worth reading.
[Self Snipped!]
Professor Forster's response is what one might expect when a particular field of science has gone spectacularly wrong: he, and his fellows out on the warming limb, have to row back from their extreme position on sensitivity but need to do it gradually. It does not matter if they are doing this consciously or unconsciously, bit by bit the estimate is coming down. After another ten years, and after another few trillion dollars have been wasted, academics like Professor Forster will be proclaiming a sensitivity of 0.6 deg C, and they will each do it with an entirely straight face.
There are precedents in other scientific fields.
They probably won't even feel guilty about the starvation, the lost opportunities for development or the deaths from hypothermia.
JF
If he understands clouds then I suggest he gets in touch with the IPCC. last time I looked they hadn't a clue.
(I assume he meant "a fair comparison").
Is this actually true, though?
I thought that the point of the modelling exercises was to run the models many 1000's of times, with a full set of known inputs and with a full set of known variables build into the model.
The output can then be used to determine the most likely path, but also to show that the known climate variabilty means that 1/2 (ish) of the runs will be above that path, and the rest below, and that the 75% and 95% bands are not 'error bands' at all, but 'weather bands', i.e. they ARE the unknown climate variablity.
So it the actual measurements fall outside these bands, then you cannot fall back on "you need to remove the effects of variability" because that was already built in to the results.
P.S. I found the layout of the Rose article confusing - it wasn't clear to me that we'd actually switched from Rose's voice to Bellamy's voice part way thru. Was this just me misreading it?
Martin A. "Note that he quotes the coefficient multiplying the logarithm to three significant figures. I asked him where he got this stuff and he replied simply:
"I read the literature" "
He got it from Wikepedia.
What I don't understand is that climate sensitivity of 1.5 to 4.5 was introduced in the Charney report in 1979. Around $100bn has been pumped into research and up until a few months ago it was still 3. What have they been doing with the money for the last 34 years?
As it happens we using the two equations supplied to us by Entropic Man from the University of Wikipedia, the climate sensitivity over the period from the post industrial age until today is 0.42. Now I am clearly doing something wrong if the range for 1C is 2-4.5C sensitivity, and I'm sure there are millions of people worthier than me who would have spotted that by now, but that's what you calculate using 0.8 deltaT and 400/280ppm for the CO2.
Others have noticed that Piers talks about "lines of evidence" without ever pointing to them, it is an alarmist ploy, used widely inside the climate science community, it gives weight to an assertion. The funny thing is it too was first used in the Charney report, at least that's the first time I saw it mentioned.
As for the 2.5C sensitivity, my guess is as good as Piers', as is anyone else's because it's just that, a guessing game. I believe it's 1, and that the earth will balance it's energy budget out accordingly. I believe that because if it was 4, 5 or 20 we'd have seen it in the historical records, like the MWP, the temperatures didn't run out of control then, but the increase in temperature must have increased water vapour into the atmophere, so why didn't the temperatures rise by 3C then? Same for the Minoan and Roman warm periods, so there's plenty of empirical evidence that the sensitivity is around 1, whereas Piers sensitivity comes from models, of a coupled non-linear chaotic system. What id the IPCC have to say about that I wonder? Oh I know
!” … In climate research and modelling, we should recognise that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible.”
IPCC TAR, Section 14.2 “The Climate System”, page 774."
Richard Betts
Sorry O/T -But to catch you while you're here may I ask if you also have thoughts on the Marcott, Shakun paper? - McIntyre is shredding it on CA and Paul Dennis has penetrating observations on the BH OMG thread today.
geronimo,
From the IPCC no less,
" In climate research and modelling, we should recognise that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible.”
Precisely. The problem of creating a reliable predictive model of the climate is orders of magnitude too hard at present, if indeed it's possible at all. So while such a thing may be fun, and even instructive, to attempt, the idea of placing any reliance on such a model, leave alone basing far reaching policy decisions on it, is ridiculous.
Frankly, I can't see why GCMs are considered a serious contribution to the discussion.
Mar 18, 2013 at 2:27 PM | steveta
But the observations are still within the 95% range of the CMIP3 models, see here.
Pharos - I have not yet come to an informed opinion on Marcott et al. Palaeoclimate reconstruction is not my field so it will take me a while. Thanks for asking though!
Anyway, back to work.....!
"But to do a far comparison you need to remove the effects of variability" (PF)
That would be natural variability, I assume? Be good to know what that was...
Yes, ask Forster to show us the evidence.
>>We now have good observational evidence for a positive water vapour feedback and even clouds<<
After 17 years of flat - now declining - temperatures, good observational evidence that there isn't any, I think he means.
Studies looking at feedbacks based on observations are below: including two of my own. the Fixed Anvil temp theory gives a positive cloud feedback and all satellite cloud data supports this. low cloud and mixed phase cloud feedbacks remain uncertain - but no evidence for a negative cloud feedback. Lindzen and Choi is wrong they omitted the climate forcing term in their equation. p.s. my estimate of ECS in going up not coming down - in Forster and Gregory 2006 my best guess was below 2 C!
Hurley .V. and Galewsky, J., 2010. A last-saturation diagnosis of subtropical water vapor response to global warming. Geophysical Research Letters, 37: L06702.
Sherwood, S.C., Ingram, W., Tsushima, Y., Satoh, M., Roberts, M., Vidale, P.L. and O'Gorman, P.A., 2010. Relative humidity changes in a warmer climate. Journal of Geophysical Research, 115: D09104.
Sherwood, S.C. and Meyer, C.L., 2006. The general circulation and robust relative humidity. Journal of Climate, 19(24): 6278-6290.
Sherwood, S.C., Roca, R., Weckwerth, T.M. and Andronova, N.G., 2010. Tropospheric water vapor, convection, and climate. Reviews of Geophysics, 48: RG2001.
Gettelman, A. and Fu, Q., 2008. Observed and simulated upper-tropospheric water vapor feedback. Journal of Climate, 21: 3282-3289
Forster, P.M.D. and Gregory, J.M., 2006. The climate sensitivity and its components diagnosed from Earth Radiation Budget data. Journal of Climate, 19(1): 39-52.
Dessler, A.E., 2010. A determination of the cloud feedback from climate variations over the past decade. Science, 330(6010): 1523-1527.
Dessler, A.E., 2011. Cloud variations and the Earth's energy budget. Geophysical Research Letters, 38: L19701.
Dessler, A.E. and Davis, S.M., 2010. Trends in tropospheric humidity from reanalysis systems. Journal of Geophysical Research, 115: D19127.
Dessler, A.E. and Wong, S., 2009. Estimates of the water vapor climate feedback during El Nino-Southern Oscillation. Journal of Climate, 22(23): 6404-6412.
Forster PMD; Collins M (2004) Quantifying the water vapour feedback associated with post-Pinatubo global cooling, CLIM DYNAM, 23, pp.207-214. doi: 10.1007/s00382-004-0431-z
Hartmann, D.L. and Larson, K., 2002. An important constraint on tropical cloud - climate feedback. Geophysical Research Letters, 29(20): 1951.
It's ironic that the alarmists are now embracing the concept of natural variability. After years if telling us that the anthropogenic signal overwhelms the "small amount" of natural variability, they now are forced to acknowledge that (a) they really don't have a good estimate for the magnitude of natural variability and (b) the claim that anthropogenic CO2 is the "dominant" cause of global warming can no longer hold.
"here remains substantial disagreement between different observational estimates of lapse rate changes over recent decades, but some of these are consistent with GCM simulations (see Sections 3.4.1 and 9.4.4)"
"Together, upper-tropospheric observational and modelling evidence provide strong support for a combined water vapour/lapse rate feedback "
Both the above from Richard's AR4 reference. I think they show a mindset. I note that the second quote refers to models as providing evidence. They do not. They may support real evidence found elsewhere.
I note that when they do provide such support as in the first quote, the ones that provide it are mentioned as if that validates them. It does not, but it pretty much DOES invalidate all the failing models, let's chuck them away and go with the one which works. I suspect Forster's evidence includes model 'evidence' and wonder whether it is cherry-picked from the whole range of model output.
(Well, I don't wonder at all, really.)
Thank you Dr Betts (Mar 18, 2013 at 2:17 PM) for the link to the AR1WG1 report's section.
However, I note that in this same document the IPCC were quite candid about the lack of understanding of the overall real-world effects of both water vapour and, more importantly, clouds -- see the quotes below. This is why the new, more recent, evidence hinted at by Prof. Forster would be of real interest to everyone who is trying to assess the scientific evidence for CAGW.
——————————————————-
http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch08.pdf
8.6.2.3 What Explains the Current Spread in Models’ Climate Sensitivity Estimates?
Using feedback parameters from Figure 8.14, it can be estimated that in the presence of water vapour, lapse rate and surface albedo feedbacks, but in the absence of cloud feedbacks, current GCMs would predict a climate sensitivity (±1 standard deviation) of roughly 1.9°C ± 0.15°C (ignoring spread from radiative forcing differences). The mean and standard deviation of climate sensitivity estimates derived from current GCMs are larger (3.2°C ± 0.7°C) essentially because the GCMs all predict a positive cloud feedback (Figure 8.14) but strongly disagree on its magnitude.
8.6.3.2 Clouds
In the current climate, clouds exert a cooling effect on climate (the global mean CRF is negative). In response to global warming, the cooling effect of clouds on climate might be enhanced or weakened, thereby producing a radiative feedback to climate warming.
…
Therefore, cloud feedbacks remain the largest source of uncertainty in climate sensitivity estimates.
8.6.3.2.1 Understanding of the physical processes involved in cloud feedbacks
The sign of the climate change radiative feedback associated with the combined effects of dynamical and temperature changes on extratropical clouds is still unknown.
…
The role of polar cloud feedbacks in climate sensitivity has been emphasized by Holland and Bitz (2003) and Vavrus (2004). However, these feedbacks remain poorly understood.
8.6.3.2.4 Conclusion on cloud feedbacks
Despite some advances in the understanding of the physical processes that control the cloud response to climate change and in the evaluation of some components of cloud feedbacks in current models, it is not yet possible to assess which of the model estimates of cloud feedback is the most reliable.
8.6.4 How to Assess Our Relative Confidence in Feedbacks Simulated by Different Models?
A number of diagnostic tests have been proposed since the TAR (see Section 8.6.3), but few of them have been applied to a majority of the models currently in use. Moreover, it is not yet clear which tests are critical for constraining future projections. Consequently, a set of model metrics that might be used to narrow the range of plausible climate change feedbacks and climate sensitivity has yet to be developed.
——————————————————-
http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch09.pdf
9.6.4 Summary of Observational Constraints for Climate Sensitivity
Structural uncertainties in the models, for example, in the representation of cloud feedback processes (Chapter 8) or the physics of ocean mixing, will affect results for climate sensitivity and are very difficult to quantify.
Oop, I posted before I'd seen Prof. Forster's post... many thanks to him for the quick feed-back.
Forster bluffs unless
Lines of evidence exist.
Transparency rules.
===========
So Forster is suggesting that his quote has been taken out of context by David Rose. Regrettably, nothing new there. However, it does appear that Forster is conceding that some of the higher estimates for sensitivity can be ruled out. So that is progress of sorts. Is this not the way that we gain understanding?
Has David Rose sensationalised the matter? Undoubtedly. Have the alarmists given him good precedent? Undoubtedly.
I have looked all the way through the bumper book of scientific terms but I have simply be unable to find 'pretty right' can so anyone tell me what that actual means in the terms of 'science ' ?
I think that Dr David Whitehouse sums this up best in his recent report :
"The counterbalancing climatic factors have not only compensated for the postulated
AGW at the end of the decade, they have kept the global annual average temperature
constant throughout the past 10-15 years when the AGW effect wants to increase it. The
key point that makes this constancy fascinating is that for every value of CO2 there is an
equilibrium temperature although equilibriums are never reached in the climate. In other
words, the higher CO2 concentration at the end of the decade exerts a stronger climate
forcing than at the beginning of the decade.
191. This makes what has happened in the past decade all the more remarkable. Because
the greenhouse effect wants to force the temperature up, which in the absence of a
cooling influence is what would have happened, the fact that the temperature has
remained constant indicates that whatever has been cooling the planet has had to
increase in strength at precisely the same rate as the CO2 warming, in order to keep the
temperature constant. This means that for about 15 years, the combined effect of all the
Earth’s climate variability factors have increased in such a way as to exactly compensate
for the rise in temperature that the increased CO2 would have given us. It is not a question
of the Earth’s decadal climate cycles summing up to produce a constant cooling effect,
they must produce a cooling effect that increases in strength at exactly the same rate as
the greenhouse effect, so as to keep the Earth’s temperature constant.
192. Can it really be the case that, over the past 15 years, the sum total of all the Earth’s
natural climatic variables, such as changes in solar irradiance, volcanoes, the Pacific
Decadal Oscillation, the North Atlantic Oscillation, and the Arctic Oscillation, all of which
can change from cooling to warming over decadal timescales, have behaved in such a
way as to produce a cooling effect that is the mirror image of the warming postulated
by the anthropogenic climate forcings from CO2 and other greenhouse gases, from the
changing water vapour, from tropospheric ozone, and from a clearing aerosol burden?
Am I alone in thinking, that in the dynamically changing global climate, this looks like a
contrived, indeed scientifically suspicious, situation?"