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Discussion > Dr Murry Salby - lecture at Parliament 6 Nov

If there are errors in any of my articles on SkS, please do add a comment to the article and explain your objection, I would be very happy to discuss them with you.
Nov 11, 2013 at 11:28 AM Dikran Marsupial

DM - Thanks for your clarifying comments. I'll try to dig out the analysis I did.

My recollection is that you showed that a line that did not pass through the origin would lead to one conclusion about CO2 residence time relative to the mean lifetime of a CO2 molecule. A line that did pass through the origin would lead to a different conclusion.

When I plotted the data with the origin of the x and y scales included, I could not produce figures that convinced me that one line was immensely better than the other.

Nov 11, 2013 at 6:09 PM | Registered CommenterMartin A

"Stoat has some observations about Salby"

I imagine the reverse is also true.

Nov 11, 2013 at 6:17 PM | Registered Commenterjamesp

Martin A, I tried to explain in the paper that the model I gave was only a first order approximation and was not suitable for quantative analysis, just to illustrate the most basic behaviour of the carbon cycle. The linear model that I used is not immensley better than one that goes through the origin, but it *is* better and the confidence interval on the adjustment time includes the uncertainty due to estimating the offset parameter. More importantly, if the line went through the origin, that would imply that the difference between natural emissions and natural uptake would be zero if the atmosphere had zero CO2, however Henry's law means that this could only be true if the oceans were also carbon free. The bias term is therefore fully justified on the grounds of physical plausibility.

Hope this helps (I am very pleased to hear someone has actually read the paper!)

Nov 11, 2013 at 7:24 PM | Unregistered CommenterDikran Marsupial

DM - thank you. I'll try to dig out my notes - if/when I've found them and reminded myself what it was about I'll email you. My recollection was that you'd said that the bias term came solely from estimating the slope from the data and not from physics but maybe I misunderstood or have misremembered.

Nov 11, 2013 at 9:44 PM | Registered CommenterMartin A

David Coe: Message received with interest, albeit some days later. I'm sure I'm not alone in looking forward to a three-cornered fight (or more) on the mysteries of CO2 and its cycle(s).

Nov 13, 2013 at 5:39 PM | Registered CommenterRichard Drake

“At the end of the day, any argument that suggests that the rise in CO2 is natural needs to be able to explain why the observed annual rise in atmospheric CO2 is less than annual anthropogenic emissions (on average about half). If the oceans and terrestrial biosphere were a net carbon source (taking in less than they emit) atmospheric CO2 would be rising faster than the rate of anthropogenic emissions as both mankind and nature would be net sources. ”

This is can be refuted with a relatively simple 'bath-tub' experiment.

A large bath-tub (with some level of water in it) has a large running tap at one end and a similarly capacious plughole at the other end. The tap is pouring water (imagine CO2) in at a slightly faster rate than it is disappearing down the plughole. So the level in the bath is rising. Take a jug of water (imagine it as containing a red dye, to help with the visualisation) and pour it into the bath. What happens?

The level in the bath will continue rising at least as fast as before and possibly faster, but how much? That will depend on how fast you pour, and WHERE. It is in fact quite possible to pour directly into the vortex at the sink and the bath water will not turn even slightly pink. The rate of increase of the water level would be similarly undisturbed. You can, of course, pour somewhere else and get a different result.

The concept of CO2 as being “well mixed” is an assumption that is misleadingly wrong in many situations. Natural CO2 sources and sinks are (by definition) not at equilibrium with either each other or the atmosphere. They are not even at a steady state. Henry's Law is a statement assuming equilibrium.

Nov 13, 2013 at 6:50 PM | Unregistered Commentermichael hart

"If the oceans and terrestrial biosphere were a net carbon source (taking in less than they emit) atmospheric CO2 would be rising faster than the rate of anthropogenic emissions as both mankind and nature would be net sources."

- Dikran, this is quite simply a non-sequitur, as in - it does not follow.

Nov 13, 2013 at 10:35 PM | Unregistered CommenterKatabasis

Katabasis - for the benefit of the slower witted members of the congregation (such as me) would you please spell out why this does not follow?

Nov 14, 2013 at 3:25 PM | Unregistered CommenterBig Oil

Because if you accept the it does follow then you have to accept that what Salby says in bunkum. But Salby can't be wrong, and therefore the sentence must be a non-sequitur.

Nov 14, 2013 at 7:17 PM | Unregistered CommenterChandra

Chandra - stop being so silly. Please.

Nov 14, 2013 at 7:34 PM | Unregistered CommenterBig Oil

Big Oil -

Because the global total of ((natural sources + anthro sources) - natural sinks) could come in at any rate of increase (or decrease). My understanding, especially after seeing Salby speak, is that the natural cycles completely overwhelm the anthro output and therefore variations in natural sources vs sinks are far, far more significant than relatively tiny increases in anthro output.

Dikran on the other hand presents us with an argument presupposing that the anthro contribution overwhelms the fluctuation in natural sources / sinks.

Nov 14, 2013 at 9:02 PM | Unregistered CommenterKatabasis

Katabasis, you ignore the word 'net'. In other words, the natural flows might be hugely bigger than the unnatural ones but only the net value is important, the net being what is left once you have subtracted the flows out of the sources and into the sinks. This net value would be zero for a system in equilibrium. Compared to zero, anthro flows are huge. And atmospheric CO2 is rising at half the anthro flow rate. Therefore the natural world is absorbing half of that flow.

Nov 14, 2013 at 11:41 PM | Unregistered CommenterChandra

-Humans are emitting more than enough CO2 to explain the rise
-CO2 rise has accelerated in lockstep with the rise in human emissions. Hasn't followed any natural cycle
-Other gases are curving upwards too, due to human activity
-The ice core record shows the recent CO2 level is unprecedented for thousands of years and so indicates the cause is man

The evidence is overwhelming that man is the cause is it not? To come up with some fabulous reason why the human CO2 emissions is magiced away is one thing, but to also have to find fabulous excuses to dismiss the ice core record and to dismiss the rise in other gases, well it's just too much. Salby would be more convincing arguing the world was flat.

Nov 14, 2013 at 11:41 PM | Unregistered CommenterMarkus

Big Oil, my post at Nov 13, 2013 at 6:50 PM , just before, Katabasis' comment was in fact an attempt to demonstrate how Dikran Marsupial's argument falls down, using the flow of water in and out of a bath as an analogy for carbon dioxide.

Maybe I failed! I could use other analogies. Try imagining the rise and fall of water levels in a tidal estuary (where the tide represents natural carbon dioxide fluxes, and the river represents human contributions). The river flow has some effect on the observed water level, depending on the time of day, and where the observer is standing. But it is not sensible to assert that it is the controlling influence on sea level.

Nov 15, 2013 at 10:26 AM | Unregistered Commentermichael hart

Markus - thank you for your comment. May I ask if you have actually watched and paid attention to Salby's Hamburg lecture? Some of your comments suggest that if you did watch it, you did not take in the points he made.

-Humans are emitting more than enough CO2 to explain the rise
No question about that. But that the amount could explain the rise does not necessarily mean that it does explain the rise.

-CO2 rise has accelerated in lockstep with the rise in human emissions.
Lockstep? Well it's true that the curves look quite similar.

Hasn't followed any natural cycle
Hold on. (Let's not bother with the fact that CO2 at the observation station follows an annual cycle, presumably natural.)

Systematic CO2 observations started around 1960 and have shown atmospheric CO2 has risen since then. Global mean temperature has also risen since 1960. Salby gives graphs showing that observed atmospheric CO2 closely follows closely the integral of global temperature so I'm not sure why you say "hasn't followed any natural cycle".

-Other gases are curving upwards too, due to human activity
If you are talking about methane, possibly due to human activity in part at least. But also possibly due to changes of temperature and rainfall also. Increased temperature and rainfall increases the rate of decay of dead vegetation. Salby showed that methane tracked CO2 well before any possible human influence.

-The ice core record shows the recent CO2 level is unprecedented for thousands of years and so indicates the cause is man
Unprecedented? Well, that is certainly the IPCC view, as Salby commented in his Hamburg lecture.

However, Salby said, after discussing the attenuation of changes in the ice record and how this needs to be compensated for:

"A change of proxy CO2 on a timescale of 100,000 years then underestimates the atmospheric change by a factor of fifteen. Swings of proxy CO2 of 100 ppmv during the glaciation cycle, then derive from changes in the atmosphere of order 1000 ppmv. Observed changes, during the twentieth century are then hardly unprecedented."

The evidence is overwhelming that man is the cause is it not?
No, I'd say it is far from clear. Salby, at London, showed plots from satellite observations of CO2 that showed that atmospheric CO2 is higher over regions such as the Amazon and central Africa where not only is there essentially no industry but very little human population.

Salby would be more convincing arguing the world was flat.
Do you really think that? Anyone who says that is inviting the rest of their comment to be dismissed as merely a recitation of what they memorised without understanding. It suggests, at very least, that you did not pay attention to what Salby said, even if you did in fact listen to his lecture.

Nov 15, 2013 at 12:18 PM | Registered CommenterMartin A

MartinA For Salby's hypothesis to be viable, he would need to be able to explain how the natural environment can be causing the increase in atmospheric CO2 whilst being a net carbon sink, that is taking more CO2 out of the atmosphere each year than it puts in. This can be determined with high reliability using the assumption of conservation of mass and the measurements from Mauna Loa and records of fossil feul use. Prof Salby himself presents the basic equation needed in his Sydney Institute talk, and also explicitly states that the two sources of data required are reliable. For further details, see my article at skeptical science http://www.skepticalscience.com/salby_correlation_conundrum.html .

Nov 15, 2013 at 2:19 PM | Unregistered CommenterDikran Marsupial

DM - yes I agree that needs explaining. Earlier I posted a link to your article and I said the mass balance argument sounds plausible.

Nov 15, 2013 at 3:13 PM | Registered CommenterMartin A

MartinA, interested to learn your thought on this matter, but I don't agree with everything Murray Salby says, unless I have misunderstood him. I would prefer that he said that the ice-core record COULD be hiding far larger swings in the atmospheric CO2 record, not that they must be.

This is the usual point every time a new hockey-stick is presented, with high short-term changes presented against a background of historical data that is simply not able to measure short-term changes as they occurred at the time. The asymmetry of the scientific method is also such that members of the hockey-team can present their latest stick as being "unprecedented" but the sceptical retort is merely that "It could be, but the data doesn't allow you to draw that conclusion".

As an aside, yes, it is difficult for a sceptic to improve the perceived quality of that objection in the face of the so called "precautionary-principle" which weighs so heavily in so many minds.

But asymmetry works in favour of sceptical viewpoints when cAGW proponents complain that sceptics use many and varied objections to their grand synthesis, some of them probably/possibly wrong. What the BBC et. al. routinely fail to grasp is that, as people often like to quote Einstein as saying, only one of the objections needs to be correct for the grand synthesis to be falsified.

Nov 15, 2013 at 3:18 PM | Unregistered Commentermichael hart

MA, I'd say it was more than just "plausible", I don't think anyone seriously doubts that the carbon cycle is a closed system and that carbon is not spontaneously created or destroyed or leaves the earth in any significant quantities. Prof. Salby certainly doesn't doubt it, given his Sydney Institute talk. Likewise nobody seriously doubts the modern instrumental CO2 record (ISTR WUWT ran a very good article on why Mauna Loa is actually quite a good place to measure background CO2, despite being a volcano), nor the estimates of fossil fuel use as governments keep good records on that as it is an important element of trade and taxation. The error bars on the data are much too small for there to be any real doubt about the conclusion. And that is only one line of evidence, there are many others http://www.skepticalscience.com/anthrocarbon-brief.html .

Nov 15, 2013 at 3:26 PM | Unregistered CommenterDikran Marsupial

I would prefer that he said that the ice-core record COULD be hiding far larger swings in the atmospheric CO2 record, not that they must be.

Nov 15, 2013 at 3:18 PM michael hart


michael,

I find it interesting - and perhaps telling - that there does not seem to have been any response whatever to Salby's discussion of the CO2 proxy record along the lines of "... this is a well understood effect that is routinely allowed for when processing measurements of atmospheric gases obtained from ice cores".

A quick search threw up a 2008 paper
http://www.geocraft.com/WVFossils/Reference_Docs/CO2_diffusion_in_polar_ice_2008.pdf
whose abstract starts

ABSTRACT. One common assumption in interpreting ice-core CO2 records is that diffusion in the ice does not affect the concentration profile. However, this assumption remains untested because the extremely small CO2 diffusion coefficient in ice has not been accurately determined in the laboratory.(...) We use noble gases (Xe/Ar and Kr/Ar), electrical conductivity and Ca 2+ ion concentrations to show that substantial CO2
diffusion may occur in ice on timescales of thousands of years. (...)

So it does seem to be normal practice to ignore diffusion effects in the ice proxy record.

To know more, I guess we'll have to await the eventual publication of Salby's work to see his analysis in detail, with the numbers he used and how he obtained and verified them.

I'd have thought that diffusion in ice would be a thing that was pretty much deterministic, permitting a reasonably precise calculation of how much the proxy record understates the true values. So maybe in due course we will indeed learn that the ice-core record must be hiding far larger swings in the atmospheric CO2 record, not merely could be hiding such changes. For the time being, we'll just have to wait.

Just (as they say) my two pennies worth....

Nov 15, 2013 at 5:51 PM | Registered CommenterMartin A

Martin A> I had no difficulty quickly and easily reproducing Salby's graphs, in the cases I tried, from publicly available data

You certainly can't do that for the ones I was talking about, because he has made up some key parameters and not told us the values. As I said.

If you know those values, then do please tell us what the values are for the non-conservative processes in the ice, and the diffusion in the ice. Because Salby certainly doesn't.

Nov 15, 2013 at 6:59 PM | Unregistered CommenterWilliam Connolley

To repeat *both* sentences of what I said...

" I had no difficulty quickly and easily reproducing Salby's graphs, in the cases I tried, from publicly available data. And I had no problem tweaking a lowpass filter to get visually identical curves to his in cases where he had smoothed the curves - perhaps surprising to you, in view of what you said about Salby not mentioning the filtering he used."

Nov 15, 2013 at 7:04 PM | Registered CommenterMartin A

MartinA, so you didn't actually reproduce anything that involved diffusion in ice. Or did I get you wrong?

But don't hold your breath waiting for that paper. He's not going to publish anything. If he were interested in doing so he would be interacting with scientists, who understand what he is talking about, rather than giving lectures to the public and politicians, who don't.

Nov 15, 2013 at 7:49 PM | Unregistered CommenterChandra

Chandra...

MartinA, so you didn't actually reproduce anything that involved diffusion in ice. Or did I get you wrong?

That's correct. I did not reproduce anything involving diffusion in ice. If I gave the impression that I did, then it was bad communication on my part. Maybe you were misled by William Connelly's 6:59 posting into thinking that I had claimed to do so?

But don't hold your breath waiting for that paper. He's not going to publish anything. If he were interested in doing so he would be interacting with scientists, who understand what he is talking about, rather than giving lectures to the public and politicians, who don't.

As I previously predicted... Others, who are convinced, like you, that "its settled, done, and nailed down" will doubtless be confident that Salby's work will be shown to be erroneous as soon as it appears in publication. Such people will also probably express doubts that it ever will be published.

Nov 15, 2013 at 9:11 PM | Registered CommenterMartin A

CO2 has curved upwards.

The Law Dome ice core curves upwards at the end too, and that ice core has decadal resolution.

Other gases like CFCs, SF4 and nitrous oxide have curved upwards due to human emissions, in line with those emissions.

CO2 curves upwards, doesn't follow any natural cycle.

Besides if Salby thinks CO2 follows temperature and CO2 is a proxy for temperature then it looks like temperature has accelerated in the past decade. No pause.

And if the ice cores are all wrong, why are skeptics citing them as evidence of some kind of lag between CO2 and temperature? Either the ice cores are wrong because of diffusion of gases, or they are right and highly accurate enough to determine small lags.

The contradictions here and avoidance of the strong evdience that the CO2 rise is human caused are evidence that Salby's position is incoherent and nuts.

Nov 16, 2013 at 1:43 PM | Unregistered CommenterMarkus