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« Mashive attack | Main | Ben Pile on Steve Jones »
Thursday
Aug042011

More pointed questioning of AGW

H/T Messenger for this podcast by Professor Murray Salby of Macquarie University. Salby looks to be pretty mainstream, having published with Susan Solomon and Martin Juckes among others. The message appears to be that much of the rise in atmospheric carbon dioxide may be natural and caused by non-anthropogenic warming.

Andrew Bolt summarises the talk here, noting Salby's comments that anyone who thinks global warming science is settled is "living in Fantasia".

 

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Reader Comments (84)

If mainstream, his turnabout acquires greater impact.

His textbook, second edition expanded, certainly enhances such cred.

Aug 4, 2011 at 11:00 AM | Unregistered CommenterOrson

Interesting. Here's Salby's homepage at Macquarie; plenty of J. Climate papers in his publications list.

Aug 4, 2011 at 11:14 AM | Unregistered Commenteranonym

What Professor Murray Salby is trying to do is to put the science back into climate science, that is;

Temperature is the main driver of atmospheric concentrations of CO2, and not the other way about.

Aug 4, 2011 at 11:27 AM | Unregistered CommenterMac

I especially liked this comment by pennyoz on Bolt's article.

settled science - there should be no such thing. New discoveries are always being developed. New theories. And that should be the headline taught to students and inculcated into every new student of science in academic institutions.
Instead we are getting designer dogma.
Designer dogma is the only science that is settled. Narrow minded and if all the rules were like this we’d still be wearing bear skins.
"Designer dogma"! Lovely phrase.

Aug 4, 2011 at 11:31 AM | Unregistered CommenterMike Jackson

I also like the phrase "Designer Dogma" but I think of it as "Supermarket Science" It's the most expensive supermarket in the world and to all intents and purposes, it is a monoply.
Their prices are extremely high, but their products (the results that you want) are guaranteed to be politicaly digestable and supportive of reductions in personal freedom and will have revenue (tax) solutions.

Aug 4, 2011 at 12:04 PM | Unregistered Commenterpesadia

I don't entirely understand the point he is trying to make. We can calculate pretty accurately the tonnage of CO2 put into the atmosphere by human activity and it corresponds well with the measured rise in CO2 in ppm

Aug 4, 2011 at 12:10 PM | Unregistered CommenterScots Renewables

There is erudite discussion about this talk at a science philosophy blog. In comments there, Rafe Champion there is an excellent and extremely able proponent of Karl Popper's work.

Mike Jackson rightly points to the pungent phrase "designer dogma". Surely, Freeman Dyson would approve!

Aug 4, 2011 at 12:14 PM | Unregistered CommenterOrson

Scots Renewables
'We can calculate pretty accurately the tonnage of CO2 put into the atmosphere by human activity'

Really , how do you do this given no one even knows the amount of human activity let alone the amount of human activity that releases CO2 to any degree of accuracy. You can guess it , you can even intelligently guess it but know one knows the actual figures for certain .

Aug 4, 2011 at 12:20 PM | Unregistered CommenterKnR

Salby:

Carbon dioxide is emitted by human activities as well as a host of natural processes. The satellite record, in concert with instrumental observations, is now long enough to have collected a population of climate perturbations, wherein the Earth-atmosphere system was disturbed from equilibrium. Introduced naturally, those perturbations reveal that net global emission of CO2 (combined from all sources, human and natural) is controlled by properties of the general circulation – properties internal to the climate system that regulate emission from natural sources. The strong dependence on internal properties indicates that emission of CO2 from natural sources, which accounts for 96 per cent of its overall emission, plays a major role in observed changes of CO2. Independent of human emission, this contribution to atmospheric carbon dioxide is only marginally predictable and not controllable.

IPCC science rest on many gross assumptions. One is that only ACO2 in the atmosphere is disturbing the carbon cycle equilibrium. This is based on the assumption that C12/C13 ratios tell us that humans are responsible for it.

My understanding from my first listen to the podcast is that Salby has looked quite closely at the annual fluctuations in atmospheric CO2 and their components. Just as Prof. Tom Segalstad of the University of Oslo argues, an isotopic geochemist, the human element is overwhelmed by unmeasured natural flux.

Anyone want to help me flesh out further details, and correct me?

Aug 4, 2011 at 12:25 PM | Unregistered CommenterOrson

Scots Renewables: "We can calculate pretty accurately the tonnage of CO2 put into the atmosphere by human activity and it corresponds well with the measured rise in CO2 in ppm"

Not quite. According to IPCC AR4, anthropogenic effects [which include e.g. land-use changes, as well as actual emissions] are approximately twice the measured rise in atmospheric CO2.

Aug 4, 2011 at 12:39 PM | Unregistered CommenterHaroldW

Scots Renewables

"I don't entirely understand the point he is trying to make. We can calculate pretty accurately the tonnage of CO2 put into the atmosphere by human activity and it corresponds well with the measured rise in CO2 in ppm"

I'm sorry this statement is simply wrong. The rise in concentration of CO2 in the atmosphere is less than what we might expect due to fossil fuel burning, cement manufacture, deforestation etc. This is because there is an increase in the flux to different sinks (photosynthesis, ocean uptake etc). Both contribute about 50% to this increased sink rate.

I haven't listened to the talk yet and will do so tonight. It's an interesting perspective and he will need to have some pretty strong arguments to convince me. Our combined data from increased CO2 levels, 13C/12C ratios, 14C composition, and O2/N2 ratios all point to anthropogenic emissions as being the dominant component in the recent rise in CO2 levels. I am not ruling out, however, the fact that ocean outgassing, respiration etc. may also be increasing.

Aug 4, 2011 at 12:40 PM | Unregistered CommenterPaul Dennis

not sure how Messenger supplied the link, is unthreaded still the place for such tips? Though it seems to have been mistaken for the discussion threads, it would be useful if all tips are in one place to prevent redundant posts.

After listening to the podcast, I was left wondering why he sat on this research for a year, and a further 6 months with his peers, if this research so remarkable. Clearly it swipes the legs from under any carbon tax mandate, this should have been released in a much more timely manor. Was it's release delayed for a book deal, or because it was inconvenient?

Aug 4, 2011 at 12:44 PM | Unregistered CommenterFrosty

I really need to see the slides / published paper. It sounds really good and very convincing as a scientific argument, but without the graphs its hard to judge the quality of the correlations etc.

Physically, it fits everyhting we expect to see ie temperature changes CO2 not vice versa. We were even blogging on this earlier this week...

Aug 4, 2011 at 12:44 PM | Unregistered CommenterThinkingScientist

Loved the reference to the dog in MIB!

Aug 4, 2011 at 12:45 PM | Unregistered CommenterThinkingScientist

The bank account analogy is also very good. IPCC et al have pushed the net figure for a long time, whilst ignoring (a) the huge natural sources and sinks and (b) the large errors on the estimates of the size of those sources and sinks, the errors dwarfing the human and net emission figures.

Aug 4, 2011 at 12:48 PM | Unregistered CommenterThinkingScientist

Perhaps then he would like to explain why the Oxygen to Nitrogen ratio has dropped with pretty much the exact rate needed to explain the CO2 increase from buring fossil fuels?

http://www.esrl.noaa.gov/gmd/obop/mlo/programs/coop/scripps/o2/o2.html

Aug 4, 2011 at 12:50 PM | Unregistered CommenterRedbone

Redbone,


"Perhaps then he would like to explain why the Oxygen to Nitrogen ratio has dropped with pretty much the exact rate needed to explain the CO2 increase from buring fossil fuels?"

Like Scots Renewables statement this one is also wrong. It is because the O2/N2 ratio hasn't fallen as expected for combusting fossil fuels, cement manufacture etc. that we are pointed towards an increasing flux to the various sinks.

Aug 4, 2011 at 12:58 PM | Unregistered CommenterPaul Dennis

I am thinking this hypothesis also sits quite nicely with the observation of a very short residence time for CO2 in the atmosphere of 5 - 7 years.

For those wanting a summary of CO2 fluxes, I posted some numbers on BishopHill earlier this year:

http://bishophill.squarespace.com/blog/2011/2/3/emissions.html?currentPage=2

Aug 4, 2011 at 12:58 PM | Unregistered CommenterThinkingScientist

I don't entirely understand the point he is trying to make. We can calculate pretty accurately the tonnage of CO2 put into the atmosphere by human activity and it corresponds well with the measured rise in CO2 in ppm
Aug 4, 2011 at 12:10 PM Scots Renewables

Show us the proven link to AGW from CO2 for the huge blame and by the way, it has to be empirical and not driven by models. Simple really! If you have the time can you also show us where the "Hotspot" is?

Aug 4, 2011 at 1:36 PM | Unregistered CommenterPete H

"the Oxygen to Nitrogen ratio has dropped with pretty much the exact rate needed to explain the CO2 increase from buring fossil fuels"

"We can calculate pretty accurately the tonnage of CO2 put into the atmosphere by human activity and it corresponds well with the measured rise in CO2 in ppm"

The trouble with both these alleged 'pretty exact' calculations is that they have clearly been tweaked and adjusted and homogenised (and yes, fiddled) to make them 'pretty much' 'correspond' with the thermageddonist writers' religious beliefs.

Aug 4, 2011 at 1:53 PM | Unregistered CommenterMartin Brumby

For those who cannot be bothered to look it up or follow the link, the flux numbers for CO2 are:

Fossil fuel burning approx 6.4 Gt per year
Atmospheric flux from natural sources is approximately 200 Gt of which:
about 90 Gt is ocean
about 110 Gt is biomass
Uncertainty on sources/sinks in nature +/- 30 to 40 Gt

The IPCC and AGW hypothesis supporters like to talk about net CO2 because it looks scary, but compared to the actual flux of CO2 and the associated uncertainty the human contribution is actually pretty small. And we know from ice core data that there is strong evidence that warming increases CO2, not the other way round.

Aug 4, 2011 at 1:54 PM | Unregistered CommenterThinkingScientist

"Mike's Nature trick to hide the decline". Just ignore anything that you disagree with, wonderful.

Global warming does not explain the constant increase of CO2 measured on Mauna Loa since 1958, fossil fuel combustion does.

http://www.esrl.noaa.gov/gmd/ccgg/trends/

Natural sources do not account for the isotope C12/C13 ratio asociated with the increase in CO2.

http://www.esrl.noaa.gov/gmd/icdc7/proceedings/abstracts/mukaiFF208Oral.pdf

Rebuttal: http://wattsupwiththat.com/2008/01/28/spencer-pt2-more-co2-peculiarities-the-c13c12-isotope-ratio/

And finally, the O2 to N2 ratio decline matches the expected decline associated with the combustion of fossil fuels.

http://www.esrl.noaa.gov/gmd/obop/mlo/programs/coop/scripps/o2/o2.html


Although any one of the above three hypothesis is not sufficient, all three together are very strong evidenvce that we are adding CO2 to the atmosphere by burning fossil fuels. To deny that possibility, or belittle it, is sticking your finger in your ears and yelling lalalalalalalalala. Frankly, I've seen a lot of that over on the CAGW side, it saddens me to see it here.

Aug 4, 2011 at 2:12 PM | Unregistered CommenterRedbone

Scots Renewables
We can calculate pretty accurately the tonnage of CO2 put into the atmosphere by human activity and it corresponds well with the measured rise in CO2 in ppm

But do we know how much is produced naturally, and is it constant?

Aug 4, 2011 at 2:17 PM | Unregistered CommenterPFM

Paul Dennis --
Do you have a reference to current estimates of the size of the sinks implied by the O2/N2 ratio history, perhaps something more recent by your colleague Dr. Manning? I'd hate to have to wait until AR5.

Thanks in advance.

Aug 4, 2011 at 2:22 PM | Unregistered CommenterHaroldW

It is really good to have Paul Dennis and Richard Betts come and post some real science over here and refute the hand-waving claims of certain individuals. Thanks to both of you.

Aug 4, 2011 at 2:33 PM | Unregistered CommenterPhillip Bratby

HaroldW,

It's a while since I've worked on O2/N2 ratios. I'll check some of the latest data and post here. As of a few years ago the O2/N2 ratio data implied that approximately 50% of the global anthropogenic CO2 output was being taken up by 2 different sinks. These are oceanic uptake (dissolution) and photosynthesis. The contribution of each of these sinks is roughly the same. ca 3 Gtonnes of anthropogenic CO2 were taken up by these sinks.

The O2/N2 data alone can't tell you the absolute size of the oceanic and terrestrial sinks.

Redbone,

the O2/N2 data shows a decrease in oxygen concentration but it doesn't match that which we would expect for anthropogenic CO2 outputs. We must be accurate here. It suggests that whilst we are burning fossil fuels we are also increasing the activity of the 2 sinks I discussed above.

Aug 4, 2011 at 2:44 PM | Unregistered CommenterPaul Dennis

RE: Redbone says

"Global warming does not explain the constant increase of CO2 measured on Mauna Loa since 1958, fossil fuel combustion does."

The natural fluxes are of the order of 200 Gt of CO2 per annum, the IPCC estimate of anthropogenic CO2 is 6.4 Gt. Miraculously, despite the IPCC natural source/sink numbers being deduced by difference, despite their having error bars of +/- 30 to 40 Gt per annum, the IPCC model assumes steady state for the natural system, the natural fluxes miraculously balance out (depsite error bars of +/- 30 - 40 Gt per annum) and voila - miraculously the increase at Mauna Loa is exactly the amount estimated to be added from anthropogenic CO2. The IPCC result is based on an assumption - atmospheric CO2 is in steady state equilibrium. This is probably why they also disregard/ignore the 150 years of reliable chemical assay data for atmospheric CO2 which paint a much more varied picture of atmospheric CO2. Never let data get in the way of your preferred model.

Alternatively, it could be that CO2 in the atmosphere is influenced by huge natural events such as ENSO, PDO and (gasp - surely not) temperature increases. Murry Slaby presents a compelling argument based on real world observations to support this alternative hypothesis. And he has actual data from satellites, not hand waving IPCC estimates.

I suspect very strongly that too many IPCC results are obtained by first thinking of the number you want, then deriving the estimates to get the required result. The only figure they publish which I believe are observed rates of sea level rise, because its difficult to fudge those.

Aug 4, 2011 at 2:50 PM | Unregistered CommenterThinkingScientist

Redbone,

the O2/N2 data shows a decrease in oxygen concentration but it doesn't match that which we would expect for anthropogenic CO2 outputs. We must be accurate here. It suggests that whilst we are burning fossil fuels we are also increasing the activity of the 2 sinks I discussed above.

Absolutely, and if the photosynthesis sink increases, we would expect the O2/N2 ratio to increase proportionately. My point is that the evidence is very strong that we are increasing the CO2 concentration in the atmosphere by burning fossil fuels. To deny that this is a very strong possibility is not good science and comparable to the despicable tactics employed by the IPCC and CAGW crowd.

How much of the measured CO2 concentration rise is anthropogenic and how much that rise affects the climate are very different and contentious issues. But to outright deny that we are not affecting the atmospheric CO2 concentration, and to deny that atmospheric CO2 concentration plays a part in the Earth's climate is just as wrong as saying that it will certainly be catastrophic. There is an effect. Is it micro or macro or somewhere in between? What we need is unbiased and scientific measurements, not prejudicial rhetoric.

Aug 4, 2011 at 3:13 PM | Unregistered CommenterRedbone

Redbone,

I don't disagree with your point of view. I was pointing out that, to be accurate, the decrease in O2/N2 ratio is not as great as one might expect if the sole change was the output of anthropogenic CO2. There is also an increase in photosynthesis and oceanic uptake.

The key question is not if man is increasing atmospheric CO2, but rather what is the climate sensitivity to CO2.

Aug 4, 2011 at 3:20 PM | Unregistered CommenterPaul Dennis

I am not a scientist but comment on his talk, and the answers he gave to questions, as an interested member of the public at large.

I was struck by:
1 the significance of human sources of CO2 (he said 5 gt) relative to the oceans (50 gt) and the land (60 gt);
2 that very little is known about these natural ocean/land sources or how they balance out with the natural sinks;
3 that relatively minor annual fluctuations in the natural sources and natural sinks completely dwarf the human component;
4 that the satellite record revealed that the principal source regions for CO2 were not, as you might expect, the Ohio basin, northern Europe or China but were to be found in the Amazon basin, tropical Africa and SE Asia - that certainly was an eye opener;
5 that natural events like the Mt Pinataubo eruption and El Nino were decisive in causing the earth`s temperature to fall or to increase in the 30 year satellite record.

It would be very helpful if someone could persuade him to publish the charts that accompanied his talk.

Aug 4, 2011 at 3:23 PM | Unregistered Commenteroldtimer

Professor Murray Salby,


I enjoyed the podcast of your presentation. Your reasoned approach and concise style was very stimulating even without video or presentation charts.


I look forward to your book that will come out before your paper.


John

Aug 4, 2011 at 3:37 PM | Unregistered CommenterJohn Whitman

While it is good that exact proportions of CO2 have been calculated, in the sense of human input v natural input, this is simply not the point or points.

The points are:
* is the observed warming attributable to human CO2 input exclusively?
* is this a bad thing?
* should we destroy our economies (and the lives of people) because of the well calculated human proportion of rising CO2?

When empirical observations are being treated as something shameful; when data obtained from empirical observations are tortured to fit models; when models are tweaked and tweaked and tweaked again to support a political agenda, without scientists not inside The Team raising their voices against the abuse of the scientific method, then a debate about an even more precise calculation of the human proportion on CO2 is comparable to debating how many angels can dance on the tip of a needle.

Aug 4, 2011 at 3:44 PM | Unregistered CommenterViv Evans

Viv Evans

I think the main points are;

1. Fluctuations in atmospheric CO2 are very sensitive to changes in temperature.

2. The recent net increase in CO2 since 1960 are not in the main anthropogenic.

3. Ice cores do not tell the whole story about the levels of past atmospheric concentrations of CO2.

4. There must a natural negative feedback to counter the positive feedback of increasing temperatures and increasing atmospheric CO2.

5. Humanity cannot control atmospheric changes in CO2, therefore it cannot possibly mitigate changes in global temperature.

6. Thus far it has taken 18 months for these research results to become public knowledge. Possibly, in total, 2 years before publication in a journal.

Conclusion: What has happened in the ancient past and in very recent times, the last 50 years, are one and the same thing - temperature drives levels of atmospheric CO2 - humanity cannot play a part in this process.

Aug 4, 2011 at 4:06 PM | Unregistered CommenterMac

Soooo ... Prof Salby has been out in the climate wilds, seeking fame and fortune.

Now he's coming back from the crusades, from slaying the heathen for their sins against the consensus. He seeks again comfort in the safe civilised haven of the scientific method, to settle down to the a nice country manor post to spend his wealth and give wisdom to his underlings. The Prodigal Son returns ...

Well ... he'll just have to line up at the gate like the rest of his faithful, clamouring to get back into the castle of scientific integrity before the storm breaks. Someone should tell Salby that there is a long infamous human history of people sharing his sort of behaviour. I think there is a name for it too ... though the word escapes my notice at this time ;-)

Aug 4, 2011 at 4:39 PM | Unregistered CommenterBrady

"temperature drives levels of atmospheric CO2"

I seem to recall Al Gore making the same point, albeit unintentionally, with his (in)famous graph...

Aug 4, 2011 at 4:43 PM | Unregistered CommenterJames P

Additional info over at Jo's blog.

Salby does not dispute that some of the rise in CO2 levels is due to man-made emissions, but found that temperature alone explains about 80% of the variation in CO2 levels.

The up and coming paper with all the graphs will be released in about six weeks. It has passed peer review, and sounds like it has been a long time coming. Salby says he sat on the results for six months wondering if there was any other interpretation he could arrive at, and then, when he invited scientists he trusted and admired to comment on the paper, they also sat on it for half a year. His speech created waves at the IUGG conference, and word is spreading.

http://joannenova.com.au/2011/08/blockbuster-plantary-temperature-controls-co2-levels-not-humans/

Aug 4, 2011 at 4:45 PM | Unregistered CommenterLord Beaverbrook

Some interesting bed time reading in preparation for the Salby paper.

http://icecap.us/images/uploads/TomQuirkSourcesandSinksofCO2_FINAL.pdf

Aug 4, 2011 at 4:52 PM | Unregistered CommenterLord Beaverbrook

Is this the right time to mention Sir Paul Nurse stating that anthropgenic CO2 is seven times that of natural sources?

Aug 4, 2011 at 4:53 PM | Unregistered CommenterProgContra

Brady
Make your point.
This simple-minded soul can't handle more than one bit of snide a day.

Aug 4, 2011 at 4:56 PM | Unregistered CommenterMike Jackson

Paul Dennis: "The O2/N2 data alone can't tell you the absolute size of the oceanic and terrestrial sinks."

Quite. I was interested, as you no doubt surmised, in the fluxes, rather than the amount of carbon in the sinks. Sorry about the imprecision in my request.

The latest information I could find in a brief search was Manning and Keeling 2006, which stated

For the 10-yr period from 1990 to 2000, the oceanic and land biotic sinks are estimated to be 1.9 ± 0.6 and 1.2 ± 0.8 Pg C yr−1, respectively, while for the 10-yr period from 1993 to 2003, the sinks are estimated to be 2.2 ± 0.6 and 0.5 ± 0.7 Pg C yr−1, respectively.
This doesn't match your "roughly equal sinks" comment, so there must be something more current.

Aug 4, 2011 at 4:57 PM | Unregistered CommenterHaroldW

There are just so many quoted pieces of data here given global this and that. Let me tell you that none of this data is of sufficient resolution to provide definitive proof of human intervention. You can if you like, as trolls tend to do, assume that humans have an influence because we are so many and so powerful but you cannot use your assumption as proof.

There is no data yet available with sufficient resolution to be proof of anything. If governments stopped wasting our money on totally useless climate models (12's of them) and spent it on improving data gathering, management,accuracy and resolution we would now have a better understanding of our planet.

Just look at the CO² uncertainty figures. They are 4 to 5 times greater than the 'expected' human contribution. And, how in hell's name do you measure that contribution and that of nature when you don't even have a satelite to do it with and even if you did how would you account for night day differences?

Stop quoteing NOAA and NASA giss figures they are worthless guesses.

Aug 4, 2011 at 4:58 PM | Unregistered Commenterstephen richards

For the 10-yr period from 1990 to 2000, the oceanic and land biotic sinks are estimated to be 1.9 ± 0.6 and 1.2 ± 0.8 Pg C yr−1, respectively, while for the 10-yr period from 1993 to 2003, the sinks are estimated to be 2.2 ± 0.6 and 0.5 ± 0.7 Pg C yr−1, respectively.

So then HAROLDW

oceanic and land biotic sinks are estimated to be 1.9 ± 0.6 that's 1.3 to 2.5

and land biotic sinks 1.2 ± 0.8 Pg C yr−1 0.4 to 2.0

So possibly each might be exactly 2 Pg C yr-1 voilà balanced

Aug 4, 2011 at 5:04 PM | Unregistered Commenterstephen richards

Did I miss your point ??

Aug 4, 2011 at 5:05 PM | Unregistered Commenterstephen richards

Well, even a sceptic might agree that 6 gigatons produced by man might just make a difference when the measured annual increase is only 3GT, no matter what or how accurate the numbers in the so-called carbon cycle. (I don't think it is a cycle as the water cycle is, and I don't think anyone has handle on the figures at all.) I do believe that if we didn't burn stuff, the CO2 might well stabilize or reduce. That point is not essential to the sceptic position anyway. Defending the source of the increase does not help us any more than the trace gas people or the second law lot.

Sensitivity is the key, and the magnitude of natural variation of climate.

Aug 4, 2011 at 5:10 PM | Unregistered CommenterRhoda

Bish, do you think someone should email Sir Paul of the Royal Society and inquire about his Horizon comment that humans contribute seven times more CO2 than natural sources:

Aug 4, 2011 at 5:13 PM | Unregistered CommenterBob

Natural sources and sinks of CO2 are NOT static - they are dynamic - there are NOT balanced.

Over 80% of the NET increase in atmospheric CO2 since 1960 has been NATURAL.

The MAIN driver in this increase of atmospheric CO2 is TEMPERATURE.

To MITIGATE increases in global temperatures by controlling the release of man-made CO2 emissions is an IMPOSSIBILITY.

Aug 4, 2011 at 5:18 PM | Unregistered CommenterMac

Bob

It wasn't Nurse that said it, it was his interviewee.

Aug 4, 2011 at 5:21 PM | Registered CommenterBishop Hill

stephen richards --
I was actually only considering the data reported for 1993-2003 -- the fluxes were given as 2.2 ± 0.6 and 0.5 ± 0.7 Pg C yr−1, which are significantly different. Manning & Keeling 2006 mentions that there was an improvement in technique:

we calculate what we believe is our best estimate for global carbon sinks over a 10-yr period, shown in Table 1, Part 1. This covers the period from 1993–2003, that is, after we improved our gas handling procedures in 1992 (Keeling et al., 2005), and when we have full records from both Southern Hemisphere and Northern Hemisphere stations.
I didn't follow the trail to the referenced paper, but took them at their word that this was the better estimate.

At any rate, this appears to be a superseded estimate based on Paul Dennis' comment.

Aug 4, 2011 at 5:22 PM | Unregistered CommenterHaroldW

Bish, you're right that Nurse didn't say it. But he repeated it and has not corrected his statement in light of many comments as to its correctness (or lack of...)

Aug 4, 2011 at 5:23 PM | Unregistered CommenterProgContra

This is interesting and surprising. I had always thought that "the CO2 rise is natural" was one of the weaker sceptic arguments, but maybe I have been misled by AGW propaganda (not something I am usually susceptible to).

If this is correct, this means that the AR4 SPM fig 1, and the associated claim of a 'preindustrial' CO2 level of 280 ppm is even more misleading than I previously thought.
The IPCC 'CO2 hockey stick' is the usual misleading splice of chalk and cheese (ice cores and atmosphere measurements) and greatly underestimates past fluctuations of CO2, as indicated by, for example, research on plant stomata, ignored by the IPCC (see above link for details).

Aug 4, 2011 at 5:24 PM | Unregistered CommenterPaulM

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