Thursday
Apr052012
by 
Bishop Hill
Bishop Hill Greenhouse reversal
Apr 5, 2012 Climate: other A new paper in Nature reports that the temperature-leads-CO2 effect seen in the Antarctic ice cores reverses when the analysis is extended to the globe as a whole (report here).
The new data is from northern hemisphere ice cores and proxies from other places around the globe.
A new, detailed record of past climate change provides compelling evidence that the last ice age was ended by a rise in temperature driven by an increase in atmospheric carbon dioxide.
The finding is based on a very broad range of data, including even the shells of ancient tiny ocean animals.
According to the BBC report, "the study covers the period in Earth history from roughly 20,000 to 10,000 years ago".
Lots of questions occur:
- we are comparing proxy-derived temperature readings to proxy-derived CO2 readings - presumably big uncertainties?
- how were the proxies selected?
- why the period selected - does the relationship hold outside this period?
Interesting stuff.
Reader Comments (80)
My layman’s take on this study is that the increased solar energy resulting from the change in the Milankovitch cycle was absorbed by the Northern Hemisphere ice sheets, but without immediately inducing a general warming of the global atmosphere.
The rest of the sequence follows. No additional heat is required to outgas CO2 from the Southern Hemisphere oceans because the already existing ocean heat is more concentrated in the Southern Hemisphere by the melted ice sheets having disrupted the Northern Hemisphere ocean circulation.
In other words, externally induced local warming of the ice sheets set of a sequence leading to CO2 outgassing from the oceans, thus leading to warming of the global atmosphere.
Whatever the scientific merits of this claim, it is certainly a very interesting and rather clever idea. A bonus is that it is potentially productive, in that it could generate further studies along this line of thinking.
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Spot on time for the next ipcc report, the rebuttal won't make it on time.
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The will now have to explain cooling, in the face of high CO2 levels to kick off the global cooling. Oh, and why the Argon out-gassing is only 6-800 years different from CO2, and not 2000 years.
Apr 5, 2012 at 10:28 PM | Pharos
"More and more I am convinced that the obsession with the CO2 paradigm and the abstract global average temperature meme acts as powerful a brake on the scientific understanding of climatic processes as did religion on astronomy."
Everything going on now looks to me exactly how I'd expect a religion to start up. I just don't see much science going on here... Hence arguments around the subject don't really get anywhere, which you'd expect if someone was defending an issue of faith. To be fair, this happens to some extent I would say from many of the sceptical points of view
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Here's a reviewer comment which Lindzen faced:
http://climateaudit.org/2011/06/10/lindzens-pnas-reviews/
Do you think this paper was judged with the same critical eye?
"Climate Science"/"Climate Scientist" have become, for me, pejorative terms.
Has anyone noted that we are currently about 800 years after the end of the MWP?
Brendan
So the atmosphere is warmed by the CO2, but not by the "increased solar energy" creating it. Are you sure?
James P
I posted that fact in here about a year ago :)
several issues are not considered in this paper (or at least in the abstract).
Antarctica does have its own climate but it does not have its own private source of CO2. Acording to the paper it is the warming of the southern oceans that produces the rise in CO2. The CO2 content of the air over Antarctica will be the same as anywhere else on the planet and so the ice cores should accurately record the timing of global changes in CO2.. However in Antarctica the CO2 rises about 800 years after the temperature rises and therefore the paper is saying that Antarctica warms 800 years before the southern oceans even though it is now getting less sunlight???
If the axis of the earth has tilted then the equator will have moved towards the Tropic of Cancer but the northern oceans dont warm??
It is still the case that according to the IPCC's own graphs, the last interglacial was 6 deg C warmer than this one with CO2 at 0nly 280 ppm. The current models of climate sensitivity (to CO2) would demand CO2 at over 2000 ppm for a 6 deg C rise :)
Looks like the spread of data doesn't provide the temporal accuracy to validate their claim..
http://wattsupwiththat.com/2012/04/06/a-reply-shakun-et-al-dr-munchausen-explains-science-by-proxy/
First rebuttal, to the authors credit he has documented all the proxy data.
http://wattsupwiththat.com/2012/04/06/a-reply-shakun-et-al-dr-munchausen-explains-science-by-proxy/
Now, there’s plenty of things of interest in there. It’s clear that there is warming since the last ice age. The median value for the warming is 4.3°C, although the range is quite wide.
But if you want to make the claim that CO2 precedes the warming?
I fear that this set of proxies is perfectly useless for that. How on earth could you claim anything about the timing of the warming from this group of proxies? It’s all over the map.
Final Conclusion
The reviewers should have taken the time to plot the proxies … but then, the authors should have taken the time to plot the proxies.
Also with more to come no doubt
Its starts with a wobble but then the CO2 takes over so its not the wobble that counts.
http://wattsupwiththat.com/2012/04/06/shakun-on-our-wobbly-worlds-precession-ocean-co2-fizzing-the-last-ice-age-and-all-that/
On WUWT, Willis Eschenbach plots the proxy data , all normalised to the same mean and std dev. and displays the result.
He concludes:
Martin A
Thanks for the heads up about that Willis Eschenbach analysis - though the link seems broken when I click it:
http://wattsupwiththat.com/2012/04/06/a-reply-shakun-et-al-dr-munchausen-explains-science-by-proxy/#more-60802
Excellent and straightforward walk through the collection of proxy temps. Simply laid out like that the "narrative" looks even more unconvincing as the set of data that has timings of max and min all over shop by all appearance , and timing is everything in this story they want to tell. My layman mind is still unimpressed at this stage by the melding them together to claim a new "narrative".
Martin A
Thanks for the heads up about that Willis Eschenbach analysis - though the link seems broken when I click it.
Excellent and straightforward walk through the collection of proxy temps. Simply laid out like that the "narrative" looks even more unconvincing as the set of data that has timings of max and min all over shop by all appearance , and timing is everything in this story they want to tell. My layman mind is still unimpressed at this stage by the melding them together to claim a new "narrative".
Dung
"I posted that fact in here about a year ago :)"
I didn't think it would be original, but it's not something you see mentioned a lot. No wonder Mann and his chums were so keen to remove the MWP (and focussed on that rather than earlier manifestations of the same thing).
James P: “So the atmosphere is warmed by the CO2, but not by the "increased solar energy" creating it. Are you sure?”
No, I’m not sure. The increased solar energy may well play a part in the heating of the atmosphere during a deglaciation. As I say, I am a layman and my previous post offered my understanding of the claims of this study.
The study seems to be a refinement of the existing explanation, that the change in the Milankovitch cycle triggers a general atmospheric warming, leading to melting of the Northern Hemisphere ice sheets, which leads to a reduction in albedo, warming of the oceans, CO2 outgassing, followed by further warming.
The Shakun study modifies this sequence and focuses on ocean circulation as the mechanism for outgassing CO2.
I am no scientist, so I can’t make any informed comment about the science. But this study offers an interesting line of thought that seems at least intuitively plausible.
"How were the proxies selected?"
Or, more generally (and absolutely vital for today's climate science ) : what relevant data was disregarded or not sought ?
Brendan
Thanks for the reply. I still have trouble with "a general atmospheric warming, leading to melting of the Northern Hemisphere ice sheets, which leads to a reduction in albedo [and] warming of the oceans"
Why would the ice sheets, which have the albedo, warm up before the ocean, which doesn't? The ocean needs to warm to produce the CO2, so it requires some gymnastics to make the CO2 responsible, and even the authors make an exception for "the onset of deglaciation", which rather pulls the rug from under their own argument, IMO.
OK I think I have my head round Shakun et al and it does not stack up:
1) The timing of CO2 rising/falling is taken from the antarctic ice core records so they agree that it is a true record of global CO2 levels.
2) The first event in Shakun's sequence is the tilting of the Earth, moving the North Pole into greater sunlight. Note that this also means that Antarctica gets less sunlight and also that northern oceans get more and southern oceans get less. The Arctic warms and fresh melt water runs off into northern oceans. Whatever happens next, warming started the process not CO2.
3) The northern oceans cool because the desalination stops the ocean circulations that bring heat from the equator to the northern oceans. However when the earth tilts, the line around the earth which gets the most heat from the sun is no longer the equator, the line moves north INTO the northern oceans. So why should the Northern oceans cool?
4) The heat at the equator backs up causing the southern oceans to warm. But the southern oceans are now getting less sunlight plus the heat is in the northern oceans so why should the southern oceans warm?
5) The southern oceans warm and cause an outgassing of CO2 which is accurately recorded in the antarctic ice core samples.
6) Shakun accepts that the ice core samples are a correct record of the antarctic and these records show that the Antarctic had been warming for 800 years before levels of CO2 but the antarctic should have been cooling?
The whole thing just does not stack up.
Some of the comment here is so unequivocal and apparently authoritative (eg from mydogsgotnonose) that it surprises me the authors feel it necessary to hide behind pseudonyms. Saying "my research suggests..." sounds very grand but my guess is that such "research" is just a few quick Google searches, and picking selectively from the work of real, non-anonymous, researchers.
James P: “Thanks for the reply. I still have trouble with "a general atmospheric warming, leading to melting of the Northern Hemisphere ice sheets, which leads to a reduction in albedo [and] warming of the oceans"
Why would the ice sheets, which have the albedo, warm up before the ocean, which doesn't?”
Bit of confusion here. I was referring to the previous understanding, where the sequence was slightly different, and assumed an initial generalised global warming.
But in both cases, and keeping in mind that I am not a scientist, I assume the ice melts first because of the thermal lag of the ocean versus the land.
The primary issue in this new explanation is that local warming in the Northern Hemisphere generates a sequence leading to global warming.
So the sequence goes: change in the Milankovitch cycle; additional solar energy to Northern Hemisphere; local melting of Northern Hemisphere ice sheets; fresh water influx into North Atlantic; change in ocean circulation; back-up of equatorial heat to Southern Hemisphere ocean; outgassing of CO2 from concentration of ocean heat; global warming.
Thus, no generalised global warming is required in the first instance to generate CO2-induced warming.
There is no greenhouse, so it can't be reversed.
Many so-called sceptics are not really basing their arguments on the true physics of the atmosphere. By failing to do so, they are demonstrating that they also have fallen for the IPCC bluff that radiation from a cooler atmosphere (including so-called backradiation, but also initial radiation) can transfer thermal energy to a warmer surface.
This is not correct physics and the sooner this is made clear to the public the better. True physics, backed up by basic phenomena such as the fact that radiation in a microwave oven is not absorbed in the usual sense of the word, shows why this is the case. No one has ever proved anything to the contrary in any empirical experiment, and never will.
The only thing any such radiation from the atmosphere can do is slow down that third or so of surface cooling which occurs by way of radiation that does not escape to space via the atmospheric window. Radiation from the atmosphere can have absolutely no effect on evaporative cooling, chemical processes or sensible heat transfer. These non-radiative components plus the radiation to space make up about 70% of all surface cooling. Furthermore, the effect of carbon dioxide with its limited frequencies is far less than a true blackbody, and less per molecule than water vapour. No gas can radiate outside its Planck spectrum (ie more than a true blackbody) and so there is no way that carbon dioxide (1 in 2,500 molecules) can contribute a very large amount of radiation anyway.
The other cooling processes merely accelerate and compensate for any minuscule slowing of radiative cooling. Thus there is absolutely no warming attributable to carbon dioxide. It is time for sceptics to get their facts right and stop giving in to part of the hoax. Only truth will prevail in the long run.
Sure, cooler bodies warming warmer ones sounds wrong. But as you intimate Doug, a warmer (less cool) cool body, can slow cooling of a warmer one.
And are you saying Tyndall's law is bollox ?
Backradiation:
Measurements show longwave radiation incident on the earth's surface. This is understood to come from the atmosphere, which is cooler. So in fact a cooler body CAN transfer thermal energy to a warmer one; and backradiation is real.
The real questions seems to be : how much of it is down to CO2 ?
Eschenbach looked at the temperature data from Shakun et al. and found a bit of a mess (http://wattsupwiththat.com/2012/04/06/a-reply-shakun-et-al-dr-munchausen-explains-science-by-proxy/). Now he has looked at all the CO2 reconstructions he could find, and he found something a bit more interesting:
'Dang, I didn’t expect that rise in CO2 that started about 6,000 BC. I do love climate science, it always surprises me … but the big surprise was not what the ice core records showed. It was what the Shakun2012 authors didn’t show.
I’m sure you can see just what those bad-boy scientists have done. Look how they have cut the modern end of the ice core CO2 record short, right at the time when CO2 started to rise again …
I leave the readers to consider the fact that for most of the Holocene, eight centuries millennia or so, half a dozen different ice core records say that CO2 levels were rising pretty fast by geological standards … and despite that, the temperatures have been dropping over the last eight millennia …
And I leave everyone to ponder how far climate “science” has fallen, that a tricksy study of this nature can be published in Nature, and can get touted around the world as being strong support for the AGW hypothesis. The only thing this study supports is the need for better peer review, and at a more basic level, better science education.
My best to all, stay skeptical,'
Source: http://wattsupwiththat.com/2012/04/07/shakun-redux-master-tricksed-us-i-told-you-he-was-tricksy/#more-60932
Doug Cotton: so are you a physicist? Sure sounds convincing!
But the scientific community (including physicists) seem convinced that CO2 is a greenhouse gas. As we put such emphasis on honest science, transparency, full disclosure, etc, I am sure we would all appreciate some references to substantiate your post. Details of your own research into the area would be appreciated too.