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« Lindzen at the Oxford Union - Cartoon Notes by Josh | Main | Air quality »

Lindzen at the Oxford Union

The Lindzen debate at the Oxford Union was, I think, a rather significant moment in the climate debate. One in which sceptic views got a fair hearing in an open debate. Lindzen was to be accompanied by a panel of invited experts consisting of David Rose, Mark Lynas and Myles Allen. Part 1 was an interview of Lindzen with interjections from the panel, while part 2 opened up the debate to the floor.

A few of us sceptics - Josh, Tallbloke, David Holland and others had met up beforehand and I think it's fair to say that we all expected little from the evening. Mehdi Hasan, the left-wing journalist who was to compere the event had been using the d-word a couple of evenings ago and had said he wasn't a neutral. This didn't bode well. In the event he ran through the gamut of "questions you ask sceptics" - denialism, big oil funding and do on - and in a way that was quite aggressive (but not unfairly so), but I think it fair to say that didn't go the way he expected. I should add that Hasan's handling of the Q&A was exemplary.

Lindzen's laid-back style does not make for good TV and I think Hasan and the TV people might have wished for a more flamboyant figure. However, it does lend him an air of authority and many of the barbs from the chair seemed to simply bounce off Lindzen's avuncular force-field.

The debate was very wide-ranging, covering everything from peer review to climate sensitivity to Milankovitch cycles to policy matters and US libel laws. Lindzen certainly knows his stuff and there was nothing that threw him and only a couple of moments when his quiet calm seemed disturbed.

The star of the show, however, was David Rose, whose controlled aggression and moral outrage was combined with great lucidity and an ability to get complex points over in an accessible fashion. This was star in the making stuff. His opponents on the expert panel on the other hand were strangely muted and almost seemed as if they had no stomach for the fight. There was in fact a great deal of agreement on many aspects of the debate - for example, everyone agreed that Hasan's "97% of scientists" line was irrelevant (and as Barry Woods explained later isn't true anyway). Perhaps more importantly, everyone also seemd to agree that current policy choices are foolish, the main differences being over whether emissions reductions are required.

Before I left home I wondered if such a long trip was worth the effort. In the aftermath I am sure that it was.

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Reader Comments (180)

"Warming is proportional to the logarithm of CO² and is +2°C (or +1 or +3 or +4 or whatever) per doubling"

This is the new universal climate change religion. Even sceptics believe in it.

Mar 10, 2013 at 9:44 AM | Registered CommenterMartin A

Martin A: I don't think we have enough planets to allow a controlled experiment so mark me down as the first agnostic. I assume the log relationship is roughly right, all else being equal. But of course all else isn't remotely equal.

Mar 10, 2013 at 10:02 AM | Registered CommenterRichard Drake

There's more to science policy than climate, While you were cheering Dick Lindzen in Oxford, Martin Rees was pontificating unopposed on the March 8 editorial page of Science-- and giving new life to the watermelon meme in the podcast that accompanies his screed.

Mar 10, 2013 at 10:05 AM | Unregistered CommenterRussell

The amount of CO2 in the atmosphere is currently increasing at a linear rate of about 2ppm (parts per million). At this rate of increase it is going to take 200 years to double the CO2 concentration in the atmosphere from the present level of 400ppm to 800ppm

In reply to Entropic Man ( Mar 10, 2013 at 12:44 AM) may I explain that this rate of increase wasn’t an assumption. It is an empirical observation based on measurements of CO2 concentrations at the Mauna Loa observatory, see Here

You can see from the linked graph that the over the past few decades the rise in CO2 has been quite steady (linear) and that it is increasing at a rate of somewhat less than 2ppm per year. It is certainly not ‘exponential’ (in spite of our increasing CO2 emissions).

It is not difficult to project therefore, that at this rate of increase it is going to take over two hundred years to double the current level from 400ppm to 800ppm. That is simple mathematics. Let us call it ‘settled science’ since it is based on repeated observation over many years.

Of course, the rate of increase in CO2 level may change sometime in the future, but why should it? If we continue to burn fossil fuel at today’s rate then we can expect , as a worst case, maybe one or two degrees warming in two centuries from now. This is not catastrophic.

Mar 10, 2013 at 11:34 AM | Unregistered CommenterMikeB

Let us not forget that the GCMs, whose mysterious feedback mechanisms are crucial to the case for alarm, do not actually model CO2 in the climate system.

Instead, they use the curious device of a posited 'external forcing', by which is meant the sudden imposition of a disturbance to the radiation budget at the 'top of the atmosphere'. This then is a conclusion added to the models as a kind of heuristic in the hope that as the model adjusts to the imposed disturbance, it will somehow mimic in an adequately realistic way, key features of what might happen in the climate system itself.

In the early days of this device, the models departed so embarassingly far from reality that a bodge called 'flux adjustment' was introduced to impose some credibility in the outputs.

Have GCMs been more of a help or a hindrance in the development of atmospheric science? Some seem to find the world of the model so convincing that it becomes more real than the one the rest of us are thinking about.

But as for policy-making, who can doubt that the models have been immensely helpful for the encouragement of potentially catastrophically harmful government interventions, of which perhaps the most egregious to date is the UK's Climate Change Act.

Mar 10, 2013 at 11:57 AM | Unregistered CommenterJohn Shade

I assume the log relationship is roughly right, all else being equal. But of course all else isn't remotely equal.
Mar 10, 2013 at 10:02 AM Richard Drake

Some time back, I posted a question on Science of Doom asking how the logarithmic relationship was derived. I had assumed it was the analytic solution of an analysis of black body radiation in the presence of a surrounding atmosphere containing x ppm of CO² or something like that.

The reply was helpful and referred to a paper where detailed numerical modelling had produced results for various levels of CO². It had been found that a log curve could approximate the numerical results over the range computed.

So it's still "models all the way down". Validated models? Haha..

Somehow the "logarithmic relationship" has encysted itself into the folklore of climate change as established fact.

Mar 10, 2013 at 12:06 PM | Registered CommenterMartin A

Martin A and others

Lubos Motl has an explanation for the logarithmic relationship. I'm sure you've come across him but, if not, there are good reasons why his views on this are worth reading: he's clever, understands a lot of physics (and its current limitations) and is very sceptical of AGW.

He concludes that 1 degree sensitivity isn't far off.

Mar 10, 2013 at 12:36 PM | Unregistered CommenterSimon Anthony

Thanks for that link Simon. Arrhenius first stated the logarithmic relationship but I admit I haven't tracked all the history or the varying formulae over time. I will read Lubos.

Mar 10, 2013 at 1:20 PM | Registered CommenterRichard Drake

The log relationship may work in the lab or on paper. It probably works locally. But does that give us a basis to assume it works no matter what the other conditions over centennial timescales? That is what we are being asked to accept when we pick a number for climate sensitivity and take it seriously. If I were a sceptic I'd say 'prove it'.

Mar 10, 2013 at 1:33 PM | Unregistered CommenterRhoda

SA - thank you. Will take a look.

Rhoda - haha

Mar 10, 2013 at 2:21 PM | Registered CommenterMartin A

There is also presumably an 'interval of validity' for the log relationship, though I've never seen this mentioned anywhere.

Mar 10, 2013 at 3:07 PM | Unregistered CommenterJake Haye

As far as the D-word is concerned Richard Lindzen actually prefers it to skeptic, he says so in this interview.

Mar 10, 2013 at 3:30 PM | Unregistered CommenterHengist McStone

Jake, rhoda, et al. -
The source with which I'm most familiar which discusses the logarithmic (or near-logarithmic) dependence is Myhre et al. (1998). See especially the top panel of its Figure 1.

Mar 10, 2013 at 3:36 PM | Registered CommenterHaroldW

His sardonic irony Hengist- he's jewish.

Mar 10, 2013 at 3:45 PM | Registered CommenterPharos

Yes I've read Myrhe. It's mathematically-derived from theory. I don't accept that all the various interactions are taken into account when you say a forcing in w/sqm is logarithmic in terms of a resultant global temperature anomaly. The link just is not there (I don't think Myrhe claims it), you'd have to demonstrate it. That is why you build a climate model, to resolve that question. But if you program the forcing change into the model the wrong way you risk assuming what you meant to check.

Even observation will not reveal the answer unless you accept that CS is constant globally over a period of time despite starting conditions. You'll get an answer but it will tell you nothing about the future if the concept of CS is, shall I say, overblown.

Mar 10, 2013 at 4:32 PM | Unregistered CommenterRhoda

It was the Myrhe et al paper that SoD referred me to when I asked about the origin of the log relationship.

I looked at Motl web page and found myself thinking "this is, at best, a plausibility argument" with its gross simplifications and apparently arbitrary assumptions.

But he finishes up saying "... the derivation above is a caricature primarily designed to understand some qualitative features of the greenhouse effect" so I don't think he's claiming more than that.

The logarithmic relation seems now to be widely accepted as if it were a physical law (subject to uncertainty in a coefficient) yet it seems to have its origin in one paper giving the results of computations from models.

Mar 10, 2013 at 5:44 PM | Registered CommenterMartin A

I am surprised to see sceptics questioning the logarithmic nature of CO2’s greenhouse effect. The fact that it is logarithmic, and not linear, acts to strongly mitigate the effects of any additional CO2. It is a fact that the IPCC prefers not to emphasise.
To illustrate what ‘logarithmic’ means, consider painting a window in order to block out the light. The first coat of paint will have a marked effect – but some light will still get through. Apply a second coat and you block out most of remaining light – but maybe some still gets through, so you continue to add more and more coats of paint.
Note that the first coat of paint has a marked effect, but successive coats of paint have less and less effect.

CO2 in the atmosphere acts very much like that, see here for a fuller description
CO2 is logarithmic because the CO2 absorption bands are effectively ‘saturated’. Any warming effect you are going to get from CO2 you have already got. Adding more will have only a marginal effect.

In this regard, you often hear that Methane is a more important greenhouse gas than CO2. But this is only because the levels of methane in the atmosphere are very low and the methane absorption bands are not saturated; so every methane molecule added has a full effect because at low concentrations the effect of additional molecules is linear. If CO2 were at the same low concentrations as methane, then adding CO2 would produce a greater greenhouse effect.

So let’s be happy that CO2’s effect is logarithmic.

Mar 10, 2013 at 6:28 PM | Unregistered CommenterMikeB

And then you go to the Harries et al paper comparing actual radiation absorption from satellite measurements. It isn't easy and involves different sats and missing years of coverage among its problems. But it finds (in the graphs, not brought to the attention afaik) that the minor band of CO2 absorption shows no change. Maybe it is saturated. If it is, then Myrhe's wattage is wrong over time. There may be other changes with increasing ppm, we don't know. Nobody therefore can state with any degree of certainty that there is a figure for CS good over decades or centuries. Of course, you are getting this from an Oxfordshire housewife. Not a climate scientist on either side.

Mar 10, 2013 at 6:30 PM | Unregistered CommenterRhoda

Mike B

Is the increase in CO2 accelerating, linear or decelerating?

It is easy to tell.

Download and print your preferred graph of the Keeling curve, such as this one.

Lay a straight edge along the top edges of the earliest and latest peaks and draw a line.

If the rate of change is accelerating, the middle part of the graph will drop below the line.

If the graph is linear, the middle part of the graph will follow the line.

If the rate of change is decelerating, the middle part of the graph will be above the line.

Try it and decide for yourself.

Mar 10, 2013 at 6:52 PM | Unregistered CommenterEntropic man

MikeB, if my last doesn't make it clearer, I don't dispute that forcing wattage is logarithmic over a small range, but that it has a fixed number of degrees per doubling effect on the global mean temp. It does not just follow, it needs a proper argument. And confidence limits on how sound that argument is over multiple doublings and centuries. No doubt the work has been done and I missed it..otherwise the concept of CS is a hypothesis in need of proof or falsifiability before we start worrying about what the number is.

Mar 10, 2013 at 6:55 PM | Unregistered CommenterRhoda

Several people have taken a properly sceptical stance as to just how sound is the basis of the logarithmic "rule". Some at least (I think) accept that individual GHGs in lab measurements and in theory have logarithmic effects but question whether that behaviour continues to apply when the gases are mixed together in the atmosphere.

Now it's probably obvious to people here but, at the risk of offering egg-sucking lessons to my mother's mother, if the effect of lots of GHGs is a sum of logarithms, with different coefficients and arguments, corresponding to absorption by different GHGs in different bands, their sum can be combined to give a single logarithm. The sensitivity for the combined logarithm - the effective atmospheric sensitivity - would be the sum of the individual sensitivities.

So if individual GHGs have logarithmic effects over some temp range, so does their combination.

Mar 10, 2013 at 7:29 PM | Unregistered CommenterSimon Anthony

Simon, it is not obvious to me. I do not discount the possibility that I am just being stubborn, but I think the effects you speak of overlap, and also that enthalpy effects may be step rather than linear, and that clouds will mees the whole thing up. By all means treat CS as a thing that is indicated, but don't give me two doublings and link that to a global average temp to an accuracy of parts of a degree. I don't buy it. I might be inclined to listen to a suggestion of falsifiability criteria..

Mar 10, 2013 at 7:44 PM | Unregistered Commenterrhoda

@ MikeB Mar 10, 2013 at 6:28 PM

I am surprised to see sceptics questioning the logarithmic nature of CO2’s greenhouse effect. The fact that it is logarithmic, and not linear, acts to strongly mitigate the effects of any additional CO2. It is a fact that the IPCC prefers not to emphasise.

If I understand you right, sceptics should not question the existence of effects which, if they exist, are beneficial?
To illustrate what ‘logarithmic’ means...

Yes, yes, we know what logarithmic means. You did A-level maths too?
So let’s be happy that CO2’s effect is logarithmic.

Please point to where its logarithmic effect has been confirmed.

Mar 10, 2013 at 7:57 PM | Registered CommenterMartin A

Steve McIntyre tried to track the CS + logarithmic stuff down in 2008 and gave me the impression of being unimpressed.

Somehow this stuff seems to have been picked up and taken as having essentially the status of a physical law by just about everyone.

Mar 10, 2013 at 8:17 PM | Registered CommenterMartin A

if the effect of lots of GHGs is a sum of logarithms

No, it isn’t Simon, it's not as simple as that. Whether the effect is logarithmic or not depends on the concentration of the particular greenhouse gas in question and whether their absorption bands are ‘saturated’ or not.
According to the IPCC

“The existing concentrations of a particular gas dictate the effect that additional molecules of that gas can have For gases such as the halocarbons, where the naturally occurring concentrations are zero or very small, their forcing is close to linear in concentration for present-day concentrations Gases such as methane and nitrous oxide are present in such quantities that significant absorption is already occurring and it is found that their forcing is approximately proportional to the square root of their concentration Furthermore, there is significant overlap between some of the infrared absorption bands of methane and nitrous oxide which must be carefully considered in calculations of forcing For carbon dioxide, as has already been mentioned, parts of the spectrum are already so opaque that additional molecules of carbon dioxide are even less effective, the forcing is found to be logarithmic in concentration”.

Entropic man, thanks for your concern, but I do know how to judge whether a trend is increasing or not. If you apply your own test to the last decade or so of Mauna Lao measurements I think you will agree that the trend is linear. Of course, if you go back far enough, then you can detect slight rate changes around the 70s and 80s. But, over the recent past, is it not fair to say that CO2 concentrations have been increasing at a steady rate.

Mar 10, 2013 at 8:25 PM | Unregistered CommenterMikeB

Entropic Man,
The Mauna Loa CO2 time series does indeed show a slight increase over time (even ignoring a period of ~3 years after the Mt Pinatubo eruption.

This is what I would expect from a warming planet out-gassing extra CO2 from the oceans, and consistent with temperature primarily driving CO2, not CO2 driving temperature.

If (if) the commonly expounded volcanic cooling from Pinatubo is real, this also explains the clear inflection in the Mauna Loa data after the Pinatubo event.

The "consensus" view likes to invoke a temperature-CO2 feedback when attempting to explain away the inconvenient ice-core records, but ignore it in the present-day instrumental record.

Mar 10, 2013 at 8:41 PM | Unregistered Commentermichael hart

Mar 9, 2013 at 6:52 PM | HaroldW

John Whitman -
Having engaged with Steven Mosher elsewhere, I take issue with your characterisation above. He is definitely not of the tribe which foresees doom from fossil fuel. Indeed, he wrote above, "But if I had to make the case, I'd make the case that 3C of warming has definite risks and those risks outweigh the benefits...It's not certain that this will be safe. It's not certain that it will be a disaster."

- - - - - - - -


Thank you for your comment.

Mosher is indeed a very well known commenter across many skeptic blogs. His unique and self-named position of 'lukewarmerism' goes with him. We have had comment exchanges over several years that are often critical in nature. I have enjoyed it.

Indur's comment (below) to Mosher shows an unsubstantiated claim (opinion) by Mosher juxtaposed against Indur's published research. Therefore they do have a fundamentally different epistemological quality. Therefore I considered, in my previous comment, it possible that if Mosher thinks he is right then it must be by some higher 'a priori' epistemically basis than Indur's rational scientific process / publication approach. Therefore my comment on Mosher's epistemic dualism.

Mar 9, 2013 at 5:13 PM | Indur M. Goklany

Steve Mosher

You claim, "But if I had to make the case, I'd make the case that 3C of warming has definite risks and those risks outweigh the benefits."

But where's your risk analysis?

I have provided a risk analysis for 4C, and it seems we would be better off despite any climate change through 2200 at least, if you believe climate change impacts analyses built on GCM results.

I am trying to drill down to get at possible hidden premises in his 'lukewarmerism', which may or may not be false premises. Skeptic dialog 101.


Mar 10, 2013 at 8:56 PM | Unregistered CommenterJohn Whitman

Alexander K,
Entropic Man used to be a school teacher for a couple of decades and it tends to come across that way in his words.

Mar 10, 2013 at 9:02 PM | Unregistered Commentermichael hart


' "if the effect of lots of GHGs is a sum of logarithms"

No, it isn’t Simon, it's not as simple as that. '

That's why I included the word "if" in my remark. My point was about a fairly trivial identity that logarithms obey (A-level, I think someone else mentioned), not about the absorption properties of GHGs.

Mar 10, 2013 at 9:13 PM | Unregistered CommenterSimon Anthony

"If you apply your own test to the last decade or so"

Not cherrypicking, I hope.

We have measured data on CO2 from 1957, that's more than 50 years in the Keeling curve Why would you want to limit your assessment to one decade?

The Pinatubo eruption did not release large amounts of CO2, its effect was a temporary cooling due to SO2 and lasted #3 years. A good reason to take as long a baseline as possible.

If you go the the Law Dome data you have a more pronounced acceleration, visible over the 250 years since 1750.

Incidentally, before you get sniffy about Law Dome, remember that the end of the ice core data overlaps the Keeling curve, giving a useful comparison between two independantly collected datasets and the measurements from both match well.

Mar 10, 2013 at 9:30 PM | Unregistered CommenterEntropic man

The radiative forcing due to increasing CO2 can be calculated using the equation

Forcing = 5.35 * natural logarithm (New CO2 concentration/ reference CO2 concentration)

The reference CO2 concentration is 280ppm. The units of forcing are W/M^2

This is where the logarithmic relationship between [CO2] and temperature comes from.

Mar 10, 2013 at 9:58 PM | Unregistered CommenterEntropic man

Alexander K,
Entropic Man used to be a school teacher for a couple of decades and it tends to come across that way in his words.

Mar 10, 2013 at 9:02 PM | michael hart

Help! I'm trapped in a website full of optimists! :-)

Mar 10, 2013 at 10:03 PM | Unregistered CommenterEntropic man

Even though Myles is probably long gone, I think his position is very reasonable and may be pretty close to the truth. What I'm not sure of is whether we will ever get to 800ppm. I think its pretty unlikely if technology advances apace. Shale gas is replacing coal and has half the CO2 of coal. So, there are some good signs that we will probably be fine even in the long term.

We don't really know either that a 4C warmer world will be a lot more inhospitable to humans. We need a lot more information to say that and maybe that's where we should be focusing our research. I'm not sure GCM's are worth much further investment. As they get more complex, the spread of their results is increasing.

Mar 10, 2013 at 10:11 PM | Unregistered CommenterDavid Young

Entropic Man,
You appear to address MikeB in your last comment but, as far as I can tell, he did not mention the Mt Pinatubo eruption, I did. So I'll assume you were replying to me.

You misunderstand my comment and, apparently, the ML data. I was not referring to any gaseous emissions from Pinatubo. I was referring to the fact that the proposed cooling from Mt Pinatubo apparently caused a clear DOWNWARD inflection in the atmospheric CO2 growth rate-consistent with cooling causing an increase in oceanic absorption of CO2 (or decreased out-gassing).

Ice cores do not have anything approaching the kinetic resolution of ML instrumental data, or, for that matter, the wet-chemical methods in use prior to that (chemical methods airily dismissed by IPCC supporters). The age-of-ice/age-of-entrapped-air conundrum will not go away by smoothing the data and shifting the time-axes until they magically fit.

Mar 10, 2013 at 10:12 PM | Unregistered Commentermichael hart

Entropic man, your comment about CS is bogus. You give a formula for w/m2 but that is not a temperature. If you read what my doubts are in previous comments you will see that it is the claim that there is a CS link to temperature which is logarithmic over centuries which is in doubt. Your assertions go no way to prove the link to temps, global mean temps, over a long timescale or many doublings.

(Yes I know there is a way people use to convert forcings to temp changes. I do not believe their methods are sound on a global scale. )

Mar 10, 2013 at 10:25 PM | Unregistered CommenterRhoda

Regarding the logarithmic relationship, it is an approximation over a limited range, and dates back at least to Arrhenius. To quote his paper:

"We may now enquire how great must the variation of the carbonic acid in the atmosphere be to cause a given change of the temperature. The answer may be found by interpolation in table VII. To facilitate such an enquiry, we may make a simple observation. If the quantity of carbonic acid decreases from 1 to 0.67, the fall of temperature is nearly the same as the increase of temperature if this quantity augments to 1.5. And to get a new increase of this order of magnitude (3.4 degrees) it will be necessary to alter the quantity of carbonic acid till it reaches a value nearly midway between 2 and 2.5. Thus if the quantity of carbonic acid increases in geometric progression, the augmentation of the temperature will increase nearly in arithmetic progression."

It's obvious it can't be a general rule, because if it was, then at zero CO2 the temperature would be minus infinity. Arrhenius calculated it as the fourth root of a rational function at each latitude band, and then summed over several latitude bands, plugging in the measured values for humidity, clouds, albedo, etc. It's a messy calculation and I haven't picked it apart yet, but it's quite definitely not a logarithm.

Arrhenius got the mechanism of the greenhouse effect wrong. He thought it was the result of back-radiation emitted by the atmosphere reducing the rate of heat loss, and his 'fourth-root of optical depth' formula reflects that. The greenhouse effect actually works by increasing the altitude of emission to space, and the logarithmic effect is more a consequence of the roughly exponential change in atmospheric (and hence GHG) density with altitude, combined (the climate scientists say) with complicated pressure-broadening effects on absorption lines lower down in the atmosphere. I don't know if that's the case - I haven't checked.

Somebody told me Gavin at RealClimate once said the modern value is calculated by running GCMs at varying CO2 levels and fitting a log curve to the results. I don't know how high they went, or even if it's true. I wouldn't recommend we assume it still applies at super-high levels.

Mar 10, 2013 at 10:52 PM | Unregistered CommenterNullius in Verba

When where will those who dwell in remote lands be able to view the video?

Mar 10, 2013 at 11:48 PM | Unregistered CommenterLawrence

In an earlier comment I suggested that, if the developing world catches up to US emissions per capita (pc) within 30 years, cumulative CO2 levels would - given a sensitivity of 1 degree - lead to a total of 3 degrees of warming.

Some scepticism was expressed at such a rate of increase, several people apparently thinking hundreds of years is a more likely time-scale.

I'm not sure how best to argue that my suggestion might not be entirely outrageous. However, I've come across some figures for historic CO2 emissions per capita at this website...

I can't vouch for their accuracy (certainly the spurious precision of the data doesn't impress). However, the figures for the US seem to show that they went from current Chinese levels, ~5Tpc, in ~1885 to ~15Tpc in ~30 years. (It's interesting and possibly significant that thereafter US per capita consumption has hardly changed and current levels are ~17Tpc).

There are obviously obstacles which may delay or prevent the developing world from reaching such levels within a generation but there's also a precedent to show it's by no means inconceivable.

Mar 10, 2013 at 11:48 PM | Unregistered CommenterSimon Anthony

Michael Hart.

Right enough. I got mixed up between two adjacent comments.

Pinatubo probably did change the change the flow of CO2 between ocean and atmosphere temporarily. I fail to see the significance over longer timescales. If anything, it is an argument for using long baseline data if available. This minimises the danger of misinterpreting tempoeary variations as long term trends.

Ice cores do not have the resolution of direct measurement. However, being able to compare the two allows better understanding of the degree of uncertainty in ice core data. I hope you are not slipping into the fallacy that any uncertainty in data automatically invalidates it completely.


Radiative forcing is a decrease in outgoing radiation relative to incoming radiation for a planet. Since both are expressed as a rate of energy flow, W/ M^2, the forcing will be in the same units.

On Earth a rise in forcing of about 3.6W / M^2 would produce a temperature rise of 1C.

Mar 11, 2013 at 1:02 AM | Unregistered CommenterEntropic man

Entropic Man,

The significance, if correct, of the Pinatubo effect is that it demonstrates that temperature regulates CO2 in the atmosphere over short time scales (as well as long time scales), not vice versa. It seriously undermines the argument that the atmospheric CO2 increases are due to human influence, and the IPCC choice of carbon-cycle model. The IPCC also apparently fails to see the significance of that.

Re: Ice Cores.
I'm all for genuine attempts at cross-calibration. First thing they need to do is go out and collect a lot more data. It shouldn't be that difficult because the relevant strata are the ones at the top!

But I don't read of much effort being expended in this direction. I wonder why?

Similarly, some, ahem, well known dendrochronologists could put a lot of uncertainties/doubts behind them by doing likewise to show the reproducibility of the dubious claims made. Will they be done? We're still waiting.

Mar 11, 2013 at 4:09 AM | Unregistered Commentermichael hart

The radiative forcing due to increasing CO2 can be calculated using the equation

Forcing = 5.35 * natural logarithm (New CO2 concentration/ reference CO2 concentration)

The reference CO2 concentration is 280ppm. The units of forcing are W/M^2

This is where the logarithmic relationship between [CO2] and temperature comes from.
Mar 10, 2013 at 9:58 PM Entropic man

Radiative forcing is a decrease in outgoing radiation relative to incoming radiation for a planet. Since both are expressed as a rate of energy flow, W/ M^2, the forcing will be in the same units.

On Earth a rise in forcing of about 3.6W / M^2 would produce a temperature rise of 1C.
Mar 11, 2013 at 1:02 AM Entropic man

Gosh, is it all as simple as that? Really? Where do you get this stuff?

Mar 11, 2013 at 7:20 AM | Registered CommenterMartin A

Yes Entropic, but outgoing in fact equals incoming. It pretty much has to. There is no mismatch and therefore no forcing? Given time to equilibrate of course. All that CO2 does not change the totals of incoming or outgoing to the planetary system one whit.

Mar 11, 2013 at 7:48 AM | Unregistered CommenterRhoda

My absorption bands are saturated in so many ways - I haven't even made it across to Lubos - but please accept my thanks, Nullius, Simon, Martin, Rhoda and all for this discussion. Especially that link back to CA almost five years ago. Bottom line for me: we (humanity, not just alarmists or sceptics) are in the shallows when it comes to understanding climate and whether CS even means anything. I find it highly unlikely that the impact of CO2 is worse than logarithmic. But I mean the impact on human well-being there. I long ago bought Essex's point that a globally averaged surface temperature anomaly is pretty meaningless, even as a proxy for energy. What matters is whether a doubling of CO2 (plus all the other GHGs and the effects of aerosols, etc) has anything like a linear effect on human suffering due to weather. Even if we burn all fossil fuels. Count me an extreme sceptic on that.

Mar 11, 2013 at 12:25 PM | Registered CommenterRichard Drake

"Where do you get this stuff?"

Mar 11, 2013 at 7:20 AM | Martin A

I read the literature.

"Given time to equilibrate of course."

Mar 11, 2013 at 7:48 AM | Rhoda

And there you have the point. The CO2 we have added to the atmosphere has upset the equilibrium by reducing the outgoing radiation. The extra trapped heat increases the temperature.

We now wait while increasing temperature increases outgoing radiation. A new equilibrium will be reached when the outgoing radiation once more matches the incoming radiation. This will be at a higher temperature than at presesnt.

Mar 11, 2013 at 3:13 PM | Unregistered CommenterEntropic man


Sorry, Didn't mean to do a hit and run. More like a 'drop a seed and see if it grows'
I'll respond to the most cogent commenters so If I ignore you, take offense.

just kidding.

Ok - let's examine some options ...

You, and the IPCC, are right and we shouldn't gamble with our '15u future'...

Does that necessitate a 'Green' future or could we look at other options?

Well, I've never said we shouldn't gamble because we must gamble and we are gambling.
If you think there is no chance of risk, if you think that risk is logically impossible, I await your syllogism. What I have said is very simple. I don't think our PLAN should be to burn it all.
how hard is that to grasp. Given the uncertainty I don't see anyone can maintain that our plan should be to burn it all. Admiting that does not necessitate a "green future" I don't even know what that means.

"You, and the IPCC, are wrong and CO2 doesn't control climate (low sensitivity) ...."

First you cannot progress in a discussion when you populate it with strawmen. The science, I could give a rats ass about the summary report, isn't anything close to your representation. C02 has nothing to do with whether the climate response function has a low value or high value.
Remember; sensitivity is the response to ANY change in forcing.

Does that necessitate a 'Green' future or could we look at other options?

Nothing necessitates a green future and nothing prevents looking at other options

You, and the IPCC, are partially correct and CO2 plays an important, but not exclusive, roll in climate ....

Does that necessitate a 'Green' future or could we look at other options?

I can see a pattern forming here.

Nothing necessitates a "green future" and nothing prevents looking at other options. That is the patternI think you're worried about what I might argue you into and your quite aware that its sensible, so you just want to deflect that conversation.

Mar 11, 2013 at 3:35 PM | Unregistered Commentersteven mosher

Under natural conditions I would agree with you. After a glacial period the extra Northern Hemisphere warming due to orbital changes generates a small amount of warming, extra CO2 is released and a positive feedback between the two ensues, which slowly raises both The result is that interstadial temperatures and CO2 rise in step over 10,000 years or so.

According to the paleoclimate evidence the colder state is a global average of 9C and 200ppm CO2. The interstadials stabilise at around 14C and 280ppm, which was our preindustrial levels.

The problem is that current conditions are no longer natural. The current CO2 levels are way above the natural norm with CO2 passed 390ppm. This is not due to natural processes. It due to us releasing by combustion CO2 trapped millions of years ago.If the past temperature/ CO2 interaction pattern continues from this starting point, considerable warming is probable.

Mar 11, 2013 at 3:37 PM | Unregistered CommenterEntropic man

Mosh: I've taken offence, as instructed. I've also not understood everything you've just written. But I think it's valuable make the defining issue whether we should burn all our fossil fuels. (All that become economic to burn, I guess. And that's quite a circular function. But anyway.) I do think it's possible that it will be net harmful to humanity for humanity to do so. (Almost channeled a negative Gettysburg there.) So I have no reason to take offence at your position. And I certainly agree that all options should be on the policy table, with some of the stupidest ones labelled green, because that's what how we choose to color code them. :)

Mar 11, 2013 at 3:50 PM | Registered CommenterRichard Drake

"Steven Mosher, I have already asked this of Myles.
How long do you think it will take the world to burn all the Fossil Fuels to achieve the 3 degrees C warming?
Do you think world's science, understanding and power generation will be the same after that amount of time, especially considering the changes of the last 100 years?"


I suppose we could work out an estimate. I suppose and hope that power generation will be different 100 years from now, BECAUSE of that hope, BECAUSE working out an estimate of how long it will take to burn it all, I think we can agree that the plan should NOT be to burn it all. That is my modest proposal. Don't commit yourself to a plan that necessitates burning it all. If that is your plan, then I'd want to see the syllogism proving that 3C is risk free. Pretty simple.

Mar 11, 2013 at 4:16 PM | Unregistered Commentersteven mosher

"I have provided a risk analysis for 4C, and it seems we would be better off despite any climate change through 2200 at least, if you believe climate change impacts analyses built on GCM results."

When you have a syllogism proving that a rise of 3C is risk free, I'd find it most interesting. My claim is simple. I don't think the plan should be Burn it all. Note this doesn't say what the plan should be. Note this doesnt rely on uncertain analysis of risks and impacts. It says, given that there is some risk in a burn it all strategy, we ought not make "burn it all the plan of record." Note, this doesnt imply wind or solar or nuclear, or anything. It merely says 'Don't plan on burning it all' If you do want to plan on burning it all, then pass me a syllogism demonstrating the logically impossibility of impacts from burning it all.

Mar 11, 2013 at 4:29 PM | Unregistered Commentersteven mosher

I don't think there is anybody who proposes burning it all, I just think we don't need to cut our own throats by a massive reduction in the rate of burning. We have time to get it right. Not via inefficient tech, not keeping poor people poor, but by using the best of technologies to avoid any problem. Right now we don't know for sure that there is a problem. I sympathise with those who say we better not find out the hard way, but we have time. Plenty of time, if we try to avoid going for some advocate's preferred solution which involves going along with some agenda of 'fairness' where everybody submits to central control and imposed conscience. Get rich. Adapt to whatever comes. Get the nukes built, with desalination plants co-located for when the grid doesn't need the power. And apparently now put livestock on the desert.

Mar 11, 2013 at 4:40 PM | Unregistered Commenterrhoda

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