Discussion > Best evidence: The story so far.
Excellent, Rhoda, I was hoping you would retain this particular thread.
Essential if we are to find the so-called 'best evidence' which seems to be extremely lacking. RB simply cannot come up with any particularly 'compelling' evidence despite his claims.
And this particular 'Oxfordshire housewife' or should I say 'used to be Oxfordshire housewife' (among other things, I am sure RB could add a few choice descriptives!) commends the ability of those who are NOT 'Climate Scientists' to read and do ...what was that thing described by Gergis, oh yes 'commonly referred to as ‘research’', ie to read and do research.
So to borrow a previous analogy of yours I would say that, despite our Climate Scientists best efforts in torturing the data, our friend CO2, the accused, (who after all is essential for our life and wellbeing) must walk free due to lack of evidence.
Marion
My scientific qualifications are on a par with yours, rhoda, but you have done a power of work on this for which the rest of we dullards should be grateful.
My constant refrain — for 10 years and more — has been the same: show me the evidence. Give me something positive that is sound empirical evidence that "this time it's different". Everything I'm offered can be argued against with minimal investigation:
No evidence that "this time it's different.
No evidence that current temperatures are outwith normal historical variation.
A constant need, as Steve McIntyre puts it, to watch the pea under the thimble.
Perhaps most convincing of all (to confirm scepticism) the incredible behaviour of the "convinced" towards anyone — even fellow scientists — who dare challenge one iota of the belief system.
I wish you luck in your search but I'll repeat my other 10-year-long refrain: it's not about science; it's all about eco-politics.
Mike Jackson
rhoda
What I am looking for is evidence that those things take place in the observed world as well as the simulated one. I am looking for measurements of it actually happening. No waffle, no BS, measurements.
Your insistence that evidence is lacking remains puzzling. We've had a look at the observational data showing an increase in GAT, OHC, SST and ongoing mass loss from the cryosphere. Given the absence of *any* plausible alternative, increasing RF from CO2 remains the most likely reason why energy is accumulating in the climate system.
Baldly stating that global average temperature is a 'misleading construct' is itself misleading; approximating global average temperature change is vital to understanding modern climate behaviour as a whole. And while there are minor differences between the various surface temperature reconstructions what is striking is the close agreement between them (satellite data for tropospheric T at 14,000ft are overlayed from 1979 - present). The routine sceptical denial of the validity of large swathes of data is rhetorically useful but scientifically weightless. Sceptics need to show that all the records are significantly in error.
Paleo tells us nothing except possibly that CO2 has been all over the place in pre-historic time and temperatures have not seemed to be dependent on it.
This is mistaken. For example, Hansen & Sato (2012) demonstrates the relationship between CO2 and T over the Cenozoic (the last 65 million years), emphasis added:
The Cenozoic climate changes summarized in Fig. 1 contain insights and quantitative information relevant to assessment of human-made climate effects. Carbon dioxide (CO2) plays a central role in both the long-term climate trends and the Milankovitch oscillations (Fig. 1b) that were magnified as the planet became colder and the ice sheets larger. Cenozoic climate change is discussed by Zachos et al. (2001), IPCC (2007), Hansen et al. (2008), and many others. We focus here on implications about the role of CO2 in climate change and climate sensitivity.CO2 is the principal forcing that caused the slow Cenozoic climate trends. The total amount of CO2 in surface carbon reservoirs (atmosphere, ocean, soil, biosphere) changes over millions of years due to imbalance of the volcanic source and weathering sink, and changes of the amount of carbon buried in organic matter. CO2 is also a principal factor in the short-term climate oscillations that are so apparent in parts (b) and (c) of Fig. 1. However, in these glacial-interglacial oscillations atmospheric CO2 operates as a feedback: total CO2 in the surface reservoirs changes little on these shorter time scales, but the distribution of CO2 among the surface reservoirs changes as climate changes. As the ocean warms, for example, it releases CO2 to the atmosphere, providing an amplifying climate feedback that causes further warming.
The fact that CO2 is the dominant cause of long-term Cenozoic climate trends is obvious Earth's energy budget. Redistribution of energy in the climate system via changes of atmosphere or ocean dynamics cannot cause such huge climate change. Instead a substantial global climate forcing is required. The climate forcing must be due to a change of energy coming into the planet or changes within the atmosphere or on the surface that alter the planet's energy budget.
Solar luminosity is increasing on long time scales, as our sun is at an early stage of solar evolution, "burning" hydrogen, forming helium by nuclear fusion, slowly getting brighter. The sun's brightness increased steadily through the Cenozoic, by about 0.4 percent according to solar physics models (Sackmann et al., 1993). Because Earth absorbs about 240 W/m2 of solar energy, the 0.4 percent increase is a forcing of about 1 W/m2. This small linear increase of forcing, by itself, would have caused a modest global warming through the Cenozoic Era.
Continent locations affect Earth's energy balance, as ocean and continent albedos differ. However, most continents were near their present latitudes by the early Cenozoic (Blakey, 2008; Fig. S9 of Hansen et al., 2008). Cloud and atmosphere shielding limit the effect of surface albedo change (Hansen et al., 2005), so this surface climate forcing did not exceed about 1 W/m2.
In contrast, atmospheric CO2 during the Cenozoic changed from about 1000 ppm in the early Cenozoic (Beerling and Royer, 2011) to as small as 170 ppm during recent ice ages (Luthi et al., 2008). The resulting climate forcing, which can be computed accurately for this CO2 range using formulae in Table 1 of Hansen et al. (2000), exceeds 10 W/m2. CO2 was clearly the dominant climate forcing in the Cenozoic.
The same question applies to the overall shape of the Zachos curve as to GAT, OHC and SST: if not CO2, then what other climatologically significant forcing explains what we see? You've already said that you accept the mainstream scientific position on the radiative physics. If so, then you have a choice between parsimonious reasoning (it's CO2) and its opposite (it's fairy-dust).
Mike Jackson insists that this is all about eco-politics but it isn't. It's about objective reasoning.
BBD
BBD, you seem to have missed the point of the question. There is no proof in presenting me with a false dichotomy derived from paleo interpreted by Hansen et al. You may not be aware that some people do not trust Hansen, he is an activist, or had you not noticed in your rush to dump several tons of irrelevance over a serious thread?
rhoda
You say so, BBD.
You're a joke because no matter how much you regurgitate half-understood factoids from your favourite scientists' papers the eco-activists plod on with their own agenda and you can't see it.
Mike Jackson
rhoda
I apologise if I have missed the point, which I understood to be a request for empirical evidence that CO2 is a significant driver of climate change. In that light, I hope you can see why I considered the reference provided to be relevant to the thread.
I'm not sure why you distrust Hansen, who is widely respected. Nor is it clear why you reject HS12 since you don't explain why you disagree with its analysis of the relation between Cenozoic temperature change and CO2.
So, again: the same question applies to the overall shape of the Zachos curve as to GAT, OHC and SST: if not CO2, then what other climatologically significant forcing explains what we see? You've already said that you accept the mainstream scientific position on the radiative physics. If so, then you have a choice between parsimonious reasoning (it's CO2) and its opposite (it's fairy-dust).
BBD
BBD, (excuse me rhoda, off topic, but) it seems to me that the paper by Hansen et al. you, BBD, cite (HS12: "Paleoclimate Implications for Human-Made Climate Change") is, at least in part, single-sided CO2-AGW advocacy. An example: The authors refer on page 23 w.r.t. nonlinear processes at the rapidly retreating Pine Island Glacier (PIG) to a study by Jenkins et al., 2010 ("Observations beneath Pine Island Glacier in West Antarctica and implications for its retreat"), but he didn't mention that Jenkins et al.:
"report evidence gathered by an autonomous underwater vehicle operating beneath the ice shelf that Pine Island Glacier was recently grounded on a transverse ridge in the sea floor."Thus PIG "is no longer anchored":
„'The discovery of the ridge has raised new questions about whether the current loss of ice from Pine Island Glacier is caused by recent climate change or is a continuation of a longer-term process that began when the glacier disconnected from the ridge,' said the paper's lead author, Adrian Jenkins, a scientist at British Antarctic Survey and an adjunct at Lamont. 'We do not know what kick-started the initial retreat from the ridge, but we do know that it started some time prior to 1970.'“
September 2011
Jul 23, 2012 at 12:26 PM | Mike Jackson
I'll repeat my other 10-year-long refrain: it's not about science; it's all about eco-politics.
Indeed, Mike. You've been at this far longer than I, but (as I may have on occasion mused elsewhere), there have been times when I've wondered if, perhaps, the "arguments" regarding the C02-->(C)AGW "primary cause" hypothesis have been fostered (and allowed to fester) and given pride of place (e.g. the increasingly dubious "carbon" tax/credits/trading - and variants thereof) in order to keep attention focused and diverted.
And in the meantime the "sustainability" crew have been quietly "occupying" and extending their reach (in no small measure thanks to the efforts of the UNEP and its multiplicity of panels, committees and ever-expanding acronymic offspring)
This may well go some way towards explaining the final score at Rio+20: Climate change 22, sustainable 400.
Hilary Ostrov
As you guys are doing the Hansen paper over on the climate comms thread, and if I write what gives me reason to distrust Hansen it might be actionable, may I ask you to carry on there, and we'll wait here for the best evidence.
As an aside, I've seen three or four papers just this week all with different stories about what happened in the geological past to alter climate. There are competing theories. Nobody knows. It would be folly to pick CO2 based on Occam. It doesn't even fulfil Occam's indicators.
rhoda
Hilary
Thanks for the statistic. I knew that 'climate change' had been shoved on the back burner at Rio but I wasn't certain just how far.
It simply reinforces the argument that global warming has outlived its usefulness as a means of progressing the eco-activist agenda.
Mike Jackson
rhoda
I cannot compel you to answer the question, but I can say that your repeated refusal to do so is as informative as a direct response.
BBD
What question? Or which question, I should say?
rhoda
rhoda,
The trick is to insist that evidence for CO2 being a "major player" in climate change is the *same* as evidence that CO2 has done what the consensus position claims it has done, i.e., cause measurable changes in the past 30 years or so (i.e., the stuff that you are looking for). Richard Betts conflates/confuses the two as well.
1) 'lots' of global change has occurred
2) CO2 can cause lots of changes (forget about the timescales, the rate, the flimsiness, the patchiness, the speculative-ness of such a statement, just forget about it)
3) therefore it must be CO2
I don't believe in (1). I don't believe in (2). Even if I did, (1) and (2) do not constitute 'evidence'.
Enough time-wasting with copy pasted crap.
shub
Shub, they post that stuff for the lurkers, in order to look like they have a response. Indeed the new email thread right here has direct evidence of same. Well, lurkers, question everything. See who keeps to the point and who wants to shift to an area they are more comfortable with. You are the target here, and they can't propagate propaganda unless they have the proper geese.
rhoda
You are the target here, and they can't propagate propaganda unless they have the proper geese.Love it!
Mike Jackson
Mike, it is not my own. I heard it on the TV oh, twenty years ago as an old saying, but google has nothing so I cannot give credit to whoever originated it.
rhoda
rhoda
What question? Or which question, I should say?
Clumsy evasions are tedious. As we both know perfectly well, you are dodging this:
So, again: the same question applies to the overall shape of the Zachos curve as to GAT, OHC and SST: if not CO2, then what other climatologically significant forcing explains what we see? You've already said that you accept the mainstream scientific position on the radiative physics. If so, then you have a choice between parsimonious reasoning (it's CO2) and its opposite (it's fairy-dust).
BBD
What MATTERS is that we need to understand the drivers of these changes.
Agreed.
Whether anyone does or does not yet understand all the drivers does absolutely nothing to strengthen the case for it being CO2. That case needs to be made on its own merit - clearly it hasn't yet been made - and there is no onus on rhoda to provide the missing link.
matthu
By the way - and I can't get my head around this - does it matter if the medieval period was warmer or cooler than today?
Does it matter if the current flattening of temperatures continues for another 10 or 20 years?
In my opinion either of these would point to there being additional important drivers - identified or unidentified - that have not been taken properly into account. So I can't quite reconcile myself to scientists not accepting that these would be important considerations that may affect current thinking.
matthu
It's not even about what I think. It is about best evidence. Is this the best they can do, namely, we can't think of anything else so it must be that? Pathetic. I can't answer your question because you posed it as a false dichotomy, which I have already pointed out. Sorry you don't like to be called on that.
So, for the benefit of BBD, let's say it again. IF this effect is going to fry or drown us all, why can't you measure it happening? Never mind it's too little to see, we can't sort it from the noise. If it's that small, why should I worry? If you can't show me, there can't be much to see. And I mean measurements during the last fifty years, not from 65 million years ago when instruments were not so advanced.
rhoda
matthu
I'm with you.
The argument that what matters is understanding the drivers seems to me another example of moving the pea under the thimble.
Of course it matters if the MWP turns out to have been warmer than the present; it suggests (nay, proves) that present temperatures are nothing unusual and therefore not of immediate concern, especially if the current flattening of temperatures were to continue for a decade or so.
Meanwhile if climate scientists want to continue research into the drivers and hopefully come up with a more coherent answer on the subject of positive vs negative feedbacks we will no doubt all be duly grateful.
For as long as there is debate about the extent to which CO2 drives temperature I refuse to panic. The answer to BBD's question is we don't know but "it must be CO2 'cos we can't think of anything else" strikes me as at best lacking in imagination!
Mike Jackson
MJ - thank you - but I guess we'd best not pursue this line of thought as we would be hijacking the original thread - the intention of which was to determine the best available evidence to support the claim that CO2-caused climate change is actually happening and to what degree.
Not to ask what else could explain the facts. That is irrelevant.
Certainly not to discuss modelling.
And as rhoda has reminded us, not to guess what happened 65 million years ago.
Simply to test whether the best available evidence (available right now) is strong enough to stand up on its own merits.
matthu
Re: Jul 24, 2012 at 8:19 PM | matthu
"Certainly not to discuss modelling."
But that is all that our Climate Scientists can provide as their 'best evidence' so a complete FAIL.
Marion
Okay, here's a suggestion.
Climate scientists predict that the Earth should give off less heat when the surface is warmer (as a direct corollary of positive feedback) and this should be directly measureable.
How long have satellites been measuring outgoing radiation from the earth, and does the evidence stack up?
matthu
This is a post to bring up to date what has happened in my search for the best evidence to support the claim that CO2-caused climate change is actually happening and to what degree. I am not looking for radiative theory, I take it that what is represented by climate scientists is a correct description of radiative physics, that CO2 does what they say in terms of absorbing and emitting radiation in the claimed bands. And that the concentration of CO2 in the atmosphere is sufficient to produce the claimed effect, and that man-made emissions are probably responsible for an increase in CO2 concentration of around 2ppm/annum. What I am looking for is evidence that those things take place in the observed world as well as the simulated one. I am looking for measurements of it actually happening. No waffle, no BS, measurements. I find that what is currently trotted out as evidence is weak and uncinvincing. Paleo tells us nothing except possibly that CO2 has been all over the place in pre-historic time and temperatures have not seemed to be dependent on it. Models tell us nothing except about the prejudices of the programmer. The current state of knowledge regarding the physical processes modelled is nowhere near what is required for any degree of success. To claim otherwise is mere hubris. Global average temperature is a misleading construct, and the surface temperature records are, shall we say, disputed in accuracy and significance. Perhaps I should point out here that my scientific qualifications are zilch. All the previous is my opinion for what it's worth.
So, I posted my desire to see best evidence in a previous discussion post, 'Where's my best evidence' http://bishophill.squarespace.com/discussion/post/1865822 and the ever-helpful Richard Betts of the Met Office chimed in with a couple of papers. One was concerned with model to observed comparisons and thus of little interest (you can validate a model with observations, but not vice versa). The other was Harries et al, 2001 paywalled but at http://tinyurl.com/bs8rloa
I'd never heard of Harries, but the aim of comparing actual outgoing LWIR by waveband between satellite observations between 1970 and 1997 seemed to be exactly the kind of evidence which could prove GHE was having a measurable effect, in that a reduction in the appropriate band would show absorption by greenhouse gases, meaning (as I understand it) that the absorption would represent retained heat in the earth system, which would be a step towards proving the hypothesis. I read the paper, which turned out to be a rather brief letter to Nature. I noticed that there was an observable decrease in outgoing IR in one of the two bands linked to CO2 and also in bands for CFCs and CH4. There was no decrease in the minor CO2 band though, and there were no observations in the H2O bands. The changes are measured in Kelvin. It is the brilliance temperature which is observed., for a narrow field of view in clear sky conditions over an area of the central Pacific. I would have liked to have seen a chart of variation over time for the 27 years and a result in watts/sq m to have a direct comparison to AGW claims. I drew the conclusion that the data presentation held back from giving that figure, possibly because it did not really show much change. I asked a couple of questions about the results but did not get any answers. I went back to Google, mainly to find a non-paywalled Harries so I could make this post. There I found that Harries had been viewed as a good result by the warmist community, claimed by some to be the smoking gun. I couldn't quite see it because it seemed to be holding back. Then I found it had been dismissed as the smoking peashooter by John Daly way back in 2001. http://www.john-daly.com/smoking.htm long before I was interested in climate. I found follow-up papers in 2003 and 2007 with more information, including a long description of the problems with making sense out of the satellite data. There seems to be no long-running satellite record. The results are obtained by splicing data from three satellites. One stopped in 1971, one began in 1997. There is no chance of a graph over the 27 years, there is no intervening data. Just effectively two snapshots. The later papers add a further snapshot from 2003 from a further satellite. The satellites, not surprisingly, have different instruments with differing fields of view and precision, using different inclinations to view the surface. Harries et al had to use all sorts of manipulation to get comparable data. He declines to present the H2O data, because it is too noisy. He seems in 2003 to not even mention the minor CO2 band. But if there is no response there, surely it is significant in terms of warming? We don't see it in heat units, and he never says why (it may very well be too difficult to do given the data). And then, oh dear, he goes to the models. Now, it may be interesting to the modellers to know what is happening in the world, but it is not relevant to me. So when he shows that this model does not match observations or that that re-analysis agrees with neither, we get no nearer to the smoking gun.
So, there we are, current status is that no convincing evidence has been suggested to me showing actual measurements of actual conditions which show greenhouse gases having an effect in the real world which varies according to known changes in gas concentration.