Discussion > Best evidence: The story so far.
Dung
What I have quoted is a well reported and documented period of time during which CO2 and temperature behave in a way that in no way agrees with the GHG theory. Therefore it is rubbish.
The small CO2 forcing change as concentrations rose from ~265ppmv (~11ka) to ~275ppmv (~1750CE) wasn't the dominant driver of Holocene climate change. CO2 forcing resulting from the ongoing increase since 1750 (~395ppmv 2012) is emerging as the dominant driver of modern climate change. This graph helps visualise the relative change in RF over the Holocene as a whole.
I'm interested in a considered and substantive response to my request that you think about the relationship between T and CO2 over the entire Cenozoic.
Mike Jackson
Or you could explain why Svensmark's 0.92 correlation between cosmic rays and cloud cover can be simply ignored.
Because nobody has proved that *if* GCRs produce an increase in aerosol formation that said aerosols can actually develop into CCNs and thus produce a climatologicially significant change in cloud cover at low altitude (or any altitude, come to that).
Or you tell us if you agree that it is correct that CO2 absorbs IR between certain concentrations and at certain wavelengths only and if not on what basis you reject this hypothesis.
'Between certain concentrations'? Atmospheric CO2 will absorb and reradiate IR at any concentration ppmv. If you increase the concentration, more absorption and reraditation will occur. The wavelengths are known. The scientific studies demonstrating that 'saturation' has somehow capped the enhanced greenhouse effect are non-existent. And there's a reason for that.
Or you could explain why if there is a positive feedback from increased water vapour in the atmosphere the effect is not lessened by the inevitable formation of clouds.
Because if clouds represented a net negative or neutral feedback, the climate would not - could not vary as it has done in response to small changes in forcing. I seem to recall going into this earlier:
If feedbacks net positive, the climate system is correspondingly sensitive to changes in forcings.
If feedbacks net neutral or negative, the climate system is correspondingly insensitive to changes in forcings.
So, how do we explain known climate variability from glacial terminations to the MWP and LIA and early C20th warming?
None were associated with a large change in forcing. Therefore, feedbacks must net positive. Otherwise, it doesn't work.
BBD
BBD
Great start ^.^ Hansen is already off message:
1. Introduction
Climate change is likely to be the predominant scientific, economic, political and moral issue of the 21st century. The fate of humanity and nature may depend upon early recognition and understanding of human-made effects on Earth's climate (Hansen, 2009).
Pachauri says that climate change is not important, it is just a small part of sustainability.
Dung
Dung
As has been said by others, I do not trust Hansen not least because he appeared before a senate committee and said that exaggerating a problem was a good thing because it helped to focus the public's mind on the need to take action.
I would very much like to see the transcript. I would like to know exactly what Hansen actually said, and exactly in what context.
I have a paper on my hard drive somewhere (pls dont make me find it) which concluded that the maximum temperature reached in our current Holocene interglacial was 6 deg C lower than that in the previous Eemian interglacial. In giving his findings the author mentions that there are other papers released recently that put the difference at 10 deg C.
I'm afraid you will have to find it as I suspect that what you are doing is confusing high latitude NH temperatures during the peak Eemian with global average temperature during the entire period.
Global *average* temperature difference between the Eemian and Holocene is estimated to be between 1C - 3C.
I'm very comfortable discussing paleoclimate, so don't worry about that.
BBD
BBD
You say:
The small CO2 forcing change as concentrations rose from ~265ppmv (~11ka) to ~275ppmv (~1750CE) wasn't the dominant driver of Holocene climate change. CO2
Now you are arguing against Eric Steig and Jeff Severinghaus over at Real Climate, tut tut.
Eric Steig:
But the calculations can only be done well when the temperature change is large, notably at glacial terminations (the gradual change from cold glacial climate to warm interglacial climate). Importantly, it takes more than 5000 years for this change to occur, of which the lag is only a small fraction (indeed, one recently submitted paper I’m aware of suggests that the lag is even less than 200 years). So it is not as if the temperature increase has already ended when CO2 starts to rise. Rather, they go very much hand in hand, with the temperature continuing to rise as the the CO2 goes up. In other words, CO2 acts as an amplifier, just as Lorius, Hansen and colleagues suggested.
Jeff Severinghaus:
This is an issue that is often misunderstood in the public sphere and media, so it is worth spending some time to explain it and clarify it. At least three careful ice core studies have shown that CO2 starts to rise about 800 years (600-1000 years) after Antarctic temperature during glacial terminations. These terminations are pronounced warming periods that mark the ends of the ice ages that happen every 100,000 years or so.Does this prove that CO2 doesn’t cause global warming? The answer is no.
The reason has to do with the fact that the warmings take about 5000 years to be complete. The lag is only 800 years. All that the lag shows is that CO2 did not cause the first 800 years of warming, out of the 5000 year trend. The other 4200 years of warming could in fact have been caused by CO2, as far as we can tell from this ice core data.
The 4200 years of warming make up about 5/6 of the total warming. So CO2 could have caused the last 5/6 of the warming, but could not have caused the first 1/6 of the warming.
Dung
BBD
You have reliable figures for global temperatures over the last 750,000 years that do not rely on ice cores? Dont bother with BH you are on for a Nobel Prize mate!
Dung
BBD
Here is the paper for the 6 deg C to 10 deg C interglacial temp difference
http://researchpages.net/media/resources/2009/08/13/GRL_resubmitted_jun19_withfigs.pdf
Dung
BBD
Its no good I am not willing to read hansen and sato; my bullshit warning bell is going non stop. I really warm to a guy who proves something by reference to a paper he wrote himself.
Well at least I found something we vaguely agree on ^.^
You said:
Global *average* temperature difference between the Eemian and Holocene is estimated to be between 1C - 3C.
in Hansen and sato he states that they are a fraction of that. I agree with you a lot more than Hansen hehe
Dung
Dung
Now you are arguing against Eric Steig and Jeff Severinghaus over at Real Climate, tut tut.
You are confusing the change between glacial and interglacial climate states with the change during an interglacial, in this case the Holocene 11.5ka - present.
BBD
Dung
The Sime et al. study you link is about regional variations in isotopic temperature proxies in Antarctic ice cores for the very recent past.
We explore the potential impact of changes in the relationship between temperature
during precipitation and mean temperature by examining the covariance between temperature and precipitation on Peninsula ice cores using 22 years (1980-2002) of ECMWF ERA40 surface air temperature (T), precipitation (P), and accumulation (PE - precipitation minus evaporation) data.
And
Over longer time periods, other type of change in climate may influence the relationship between annual mean δ and temperature [e.g. Sime et al., 2008]. Analysis of model runs over centennial timescales may therefore prove necessary for the interpretation of longer
Peninsula ice core δ records.
It's puzzling that you should link to this paper in this discussion.
BBD
BBD
My profound apologies I should have linked the following:
http://researchpages.net/media/resources/2009/12/11/SIME_nature08564.pdf
Dung
BBD
It really would be helpful if you stopped assuming this "holier than thou" kind of attitude mate, are you infallible? Do you never make mistakes? Is everyone who does not agree with you really an idiot?
Re Steig and Severinghaus, I am not confused at all and neither are they (well actually yes they are hehe).
Steig and Severinghaus are trying to suggest that CO2 is actually involved in BOTH warming from glacial to interglacial AND during interglacial. As you pointed out earlier everybody knows that CO2 has nothing to do with the change from glacial to interglacial.
Dung
BBD
Our conversation has effectively taken over Rhoda's thread which I think is unfair. I will only continue our discussion if you start to get more friendly and polite mate.
Dung
Dung
Steig and Severinghaus are trying to suggest that CO2 is actually involved in BOTH warming from glacial to interglacial AND during interglacial. As you pointed out earlier everybody knows that CO2 has nothing to do with the change from glacial to interglacial.
They are correct (GHG forcing prolongs interglacials) and what I said above doesn't contradict them. And when did I say that CO2 has 'nothing to do' with glacial terminations? I have said that it's an amplifying feedback to orbital forcing. Misrepresentation is naughty.
BBD
- we crossed
rhoda asked about best evidence and given your previous remarks about censorship I had assumed you regarded our discussion as OT.
As for friendly and polite, well, I'm sticking to the facts and not pulling faces... :-)
BBD
And one other thing:
It really would be helpful if you stopped assuming this "holier than thou" kind of attitude mate, are you infallible? Do you never make mistakes? Is everyone who does not agree with you really an idiot?
I took the time to read this paper. Having a pop at me because I wasted that time in order to discover that you had posted the wrong link is out of order.
BBD
Dung
Sime et al. (2009):
We conclude that previous temperature estimates from interglacial climates are likely to be too low. The available evidence is consistent with a peak Antarctic interglacial temperature that was at least 6K higher than that of the present day —approximately double the widely quoted 3 +/- 1.5K.
BBD:
I'm afraid you will have to find it as I suspect that what you are doing is confusing high latitude NH temperatures during the peak Eemian with global average temperature during the entire period.Global *average* temperature difference between the Eemian and Holocene is estimated to be between 1C - 3C.
So polar amplification at both ends... :-)
BBD
If it is not "best evidence", please don't post it here. Dung, you know the propensity of BBD for thread hijacking.
shub
I understand your point Shub but I believe Svensmarks theory has been better confirmed than GHG theory so where do I go?
OK if I want to post on this thread I must ignore BBD, sorry BBD.
Dung
Dung
Like you, I believe that Svensmark's hypothesis is worth pursuing. It may not be correct but if I am forced to choose between Svensmark's view of the universe and BBD's, I don't see any contest!
So let me try this one again:
I asked BBD to
explain why Svensmark's 0.92 correlation between cosmic rays and cloud cover can be simply ignored.and got the usual non-answer
Because nobody has proved that *if* GCRs produce an increase in aerosol formation that said aerosols can actually develop into CCNs and thus produce a climatologicially significant change in cloud cover...Next question then, BBD: Has anyone proved that the aerosols can't produce a climatologically significant change in cloud cover? And as a follow-up we'll go back to the previous question:
Given the 0.92 correlation between cosmic rays and cloud cover why would a scientist with a reasonably open mind not investigate to see if correlation does equal causation?
What you are saying — in effect — is that the hypothesis is not worth investigating because nobody has yet proved it.
Is that how science is supposed to be done?
Mike Jackson
BBD getting friendly is the other alternative. :)
shub
Mike - I've posted various links to various papers (a small representative sample of a much larger whole) showing very clearly that there is exactly zero evidence supporting the Svensmark hypothesis. A couple are on the 'communication' thread. They are, inter alia, examples of science being done properly. An example of it being done very badly is provided by Svensmark, who makes astonishingly large claims for a still-unvalidated hypothesis that looks dodgier by the year.
BBD
shub
If it is not "best evidence", please don't post it here. Dung, you know the propensity of BBD for thread hijacking.
If the evidence isn't discussed and examined, how are we to rate it? And since when were you appointed moderator here?
BBD
I'm sorry, BBD, but that doesn't work any more.
Your habit of referring to other people's work as a diversionary tactic to prevent having to actually answer a question is too well-known.
Let's pick up a couple of points:
Svensmark has not been making "astonishingly large claims" and he is only "doing science badly" in your book because he is proposing a hypothesis that — were it to prove correct — would blow a hole in your precious belief in CO2.
The hypothesis he proposes — which, I repeat, may or may or may not be a valid one — is a perfectly legitimate starting point, given that he has established a 0.92 correlation between cosmic rays and cloud cover. I note that you don't dispute this statement but somehow this correlation is not worthy of further investigation.
To say, as you did in your last post, that the hypothesis remains unvalidated, or as in your previous post, that "nobody has proved" that cosmic rays do actually cause increased cloud cover, simply makes you look foolish.
What you are saying in effect is that nobody should research something before it has been validated or before it has been proved. Don't you understand just how stupid that sounds?
Mike Jackson
BBD, the best evidence would not be models or proxies. It's not best evidence in legal sense just because it's the best you have, it has to be the best available. Which in this case one would hope to be measurements of IR up and down, insolation and albedo. In the case of Svensmark a link between GCRs, solar activity and albedo or cloud-related effects would be someething of use. If you want to hang the defendant Mr CO2, you need more than 'we can't think of anyone else'. In fact, you are not even able to prove a crime was committed. You are beyond 'no case to answer' but nowhere near 'beyond reasonable doubt'.
rhoda
BBD
Just to clarify why the temperature difference between the two interglacials is important:
AR4 concludes that in the Eemian interglacial, levels of CO2 did not exceed 280 ppm. Our current interglacial now has CO2 levels at 400 ppm so even the AR4 figures are pretty damning for the GHG theory. No surprise then that Hansen seeks to reduce the figure.