650 000 années de concentrations de gaz à effet de serre
) Les derniers résultats du forage EPICA en Antarctique viennent juste d'être publiés dans le numéro de cette semaine de Science (Siegenthaler et al. et Spahni et al.). Cette carotte glaciaire a permis d'étendre l'enregistrement du climat Antarctique jusqu'à 800 000 ans, alors que les concentrations de gaz à effet de serre, piégées sous forme de minuscules bulles de gas, ont été analysées pour les 650 000 dernières années. Ces enregistrements de CO2, CH4 et N2O sont en accord avec ceux de Vostok (également en Antarctique) disponibles depuis quelques années, et permettent d'observer 4 cycles d'alternance glaciaire/interglaciaire supplémentaires. Ces travaux sont remarquables, et justifient des efforts gigantesques effectués sur le terrain pour ramener des échantillons enfouis jusqu'à 3km de profondeur dans la glace Antarctique. Que nous disent ces nouvelles données, et dans quelle direction peuvent elles nous mener ?
(suite…)
Premièrement, ces résultats démontrent clairement que la relation entre climat et CO2 déduite a partir de l'enregistrement de Vostok est remarquablement robuste - en dépit d'un changement majeur dans les caractéristiques des alternances glaciaire-interglaciaire avant 400 000 ans. Un exercice international, 'le challenge EPICA' avait été mis en place il y a quelques mois pour les chercheurs travaillant sur les modèles du cycle du carbone, afin de déterminer si ce serait le cas ou pas, et la plupart des prédictions se sont révélées justes. (Qui a dit que les prédictions climatiques ne peuvent être vérifiées ?). Ceci va de pair avec le fait que toute incertitude sur la fiabilité et reproductibilité des enregistrements de gaz a effet de serre doit maintenant être complètement écartée. En effet, que différents laboratoires, étudiant de la glace extraite de différentes manières et provenant de différents endroits donnent des résultats très similaires, montre de manière très claire que ce qu'ils mesurent est réel. Dans le cas ou il subsiste des problèmes (par exemple pour mesurer le N2O dans de la glace riche en poussières), ces problèmes sont clairement identifiés et ces données écartées.
Deuxièmement, ces résultats vont permettre aux paléoclimatologues de regarder en détail les différences entre les différents interglaciaires du passé. Les 3 précédents interglaciaires a notre ère se ressemblent beaucoup et furent relativement brefs (environ 10000 ans). Celui qui a eu lieu il y a 400 000 ans (correspondant au stade isotopique marin 11, pour ceux qui comptent de cette manière) était par contre supposé ressembler a l'Holocene (la période interglaciaire pendant laquelle nous vivons) et semble être plus long (environ 30 000 ans). Alors que beaucoup de détails n'étaient pas complètement résolus dans les données de Vostok, ceux ci devraient maintenant s'éclaircir. Ces enregistrements permettront peut être de tester et de résoudre certaines des idées de Ruddiman, et également nous aider a estimer la durée probable de la période chaude pendant laquelle nous vivons.
Plus généralement, comme ces interglaciaires semblent assez différents de ceux précédemment décrits, ceux-ci vont nous permettre de tester certains modèles et théories du climat dans une nouvelle série de cas. Comme le dit Richard Alley "que vous soyez un physicien, un chimiste, un biologiste, un géologue ou qui que ce soit étudiant le système Terre, il y a dans ces données a la fois des confirmations majeures de ce que nous comprenons déjà de cette planète et de nouvelles interrogations sur quelques points".
Mise-a-jour 1er décembre: Thomas Stocker a envoyé une image plus claire des données:
.
25 novembre 2005 at 4:03 AM
Hello Gavin
Your graph is not very lisible.
Can you rectify it?
A question:
Is this time of -800000 years the possible limit of ice cores?
And what is the becoming of very much older ice in Antarctica or Greenland?
I suppose these both regions were cold since millions of years.
So is there a sort of melting of very deep ice in contact with ground and under pressure?
25 novembre 2005 at 5:26 AM
One little annoying thing is that looking at the graphs quick makes you think that what’s happening now is nothing new and has happened before (the fast changing temperature)… are there good explanations for all the peaks? (Bet there are…)
25 novembre 2005 at 5:40 AM
To be a bit more precise, the correlation between CO2 and temperature has been known for quite some time, and this just makes it stronger. The early (and some times still) question is what comes first, and there is no one line answer to that…
Discussing the anthropogenic effect of the temperature this correlation would help if you clearly could say that CO2 affects the temperature an not only the other way around. Now looking at the graphs it mainly looks the other way around. And explaining that it some times before CO2 also strengthens or weakens the temperature effect isn’t all that easy?
So what would you say to a person that shows this diagrams and says, look it is the temperature that affects CO2 not the other way around. And if he continuous to argue that it have bean really fast changes in temperature before and it don’t have anything to do with CO2…
(Under 30sec that is…)
Anyone?
25 novembre 2005 at 7:15 AM
To #3
The question on the phaselag between CO2 and temperature was answered several times already, e.g. http://www.sciencemag.org/cgi/content/full/283/5408/1712 find a lag of about 600 years during glacial terminations. Among many other factors the ocean has an important control on CO2 concentrations which is why a phaselag of a couple of hundred years is no surprise. During the change from cold glacial to warm interglacial conditions it’s not CO2 which is moving first and somehow driving primarily the system.
To your second question: The real question is if you can understand the global character of glacial endings and the corresponding temperature amplitudes without a CO2 feedback. The answer is no. This results is based on different type of model studies.
The curves therefore give you an idea of how CO2 and temperature are linked to each other by different mechanisms acting on different time scales.
To find out what triggered the end of a glacial is however a different story and I dont see that CO2 should be the driving agent as your question suggests.
25 novembre 2005 at 7:56 AM
Any comment on this story in the Guardian today. In particular there’s the somewhat misleading sub-headline “Cut in greenhouse gases futile, researchers say” which implies that even if we did cut emissions massively it wouldn’t make any difference.
From what I know I thought that significant differences would be seen by the end of the century if you compare a stabilistion scenario at 450 ppm and a ‘business as usual’ scenario where CO2 levels keep rising through 2xpre-industrial [550ppm] and keep on going higher.
If you dig a bit deeper into the text of the article it turns out that the Professor is saying the he doesn’t think that GHG emissions will be cut enough to make a difference which is a different thing altogether. [ie he thinks that *if* CO2 emissions were cut by ~50% then it would make a difference but he doesn’t think that such a cut is politically or economically feasible].
[Response: Miller’s point is that sea level will continue to rise under any conceivable scenario (as seen in the ‘committed climate change’ papers by Meehl et al and Wigley earlier this year. The sub-headline is misleading though; while cuts in emissions will not prevent sea level rise, they may prevent the worst case scenarios in the medium to long term. -gavin]
25 novembre 2005 at 8:22 AM
Reply to #2 & #3.
There is a good article here on here about the ~800year lag of CO2 to temperature at glacial terminations.
25 novembre 2005 at 9:24 AM
#1
800Kyr must not be the absolute limit. I think Dome A is discussed of being a possible drilling site with ice going back until 1,000ky BP. Quality of DomeC ice at the bottom is already poor and I dont know about the future of gas measurements in the lowest part.
In Greenland the search for a place nicely stratified down to the bottom goes on. The is the discussion about North North GRIP looking for a place covering the Eemian period (130.ky). Much older datable ice is very improbable to find there.
Yes there is underground melting both in Greenland and in Antarctica. Check for Lake Vostok and corresponding scientific activities to drill this lake (mainly to learn about its biology). More fantastic projects include drilling into the lake sediments of Lake Vostok thereby having access to climate information over a couple of millions of years.
25 novembre 2005 at 10:55 AM
There is an interesting relationship in the time series data for ENSO and global CO2 growth (both peak in 1982-83, 1987-88 and 1997-98).
Multivariate ENSO Index (MEI)
from: NOAA Climate Diagnostics Center
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
Global Average Growth Rate based on CO2 measurements
from: NOAA CMDL cooperative air sampling network
http://www.cmdl.noaa.gov/gallery/ccgg_figures/co2trend_global
25 novembre 2005 at 11:17 AM
Thanks for the response,
I know the C budget and it’s ways through the system. My thought was that maybe some one has a good quick answer to some old historic passage where CO2 clearly (seem to) have an effect. I’m just pointing out what I hear regularly from what persons that are new to these things say.
However I also know that there seldom is a quick answer to complicated issues…
25 novembre 2005 at 12:51 PM
re#7
Thanks for your response Georg.
How can we understand the relatively abrupt increasing of CO2 concentration after glacial period?(less abrupt than now)
Can orbital oscillations (Milankowitch) be so discontinuous?
Or can we invoke retroactions or volcanic CO2?
Do climate models offer us good simulations of these periods?
25 novembre 2005 at 2:47 PM
Somehow the ice cores are getting back into the attention. I predict that the isotope (=temperature?) and CO2 correlation is the biggest misunderstood phenomenon in the whole climate science.
Once it will be clear what we can really see in the ice cores and it has nothing to do with warming.
I posted this somewhere else today:
Not Temperature but Precipitation (Non Calor Sed Umor)
The other month I posted this:
“The isotope spikes in the ice cores are not temperature indicators but precipitation indicators. Of course I know that lesson one part A of climate theory is that ice cores store temperature changes in oxygen and hydrogen isotope ratios (d18O and dD), but it’s very easy to proof that this is not true. Both on the long time scales ~420,000 years (Vostok and EPICA Dome C ice cores) as for the detailed millenium scale around the last termination (GRIP, NGRIP, GISPII ice cores). Multiple palynological proxies are showing clearly that the Younger Dryas was not cold but dry and that the start of the Holocene was not warming but a dramatic, perhaps near global, increase of precipitation. Moreover it can be shown that the increase of humidity reduces the Rayleigh effect which leads to a increase in heavy isotopes (18O, 2H), misinterpreted as warming. Furthermore an increase in summer precipitation has the same effect, increasing the average ratio of heavy isotopes, without a requirement for warming. Bottom line, those “isotope = temperature” graphs are not temperature but precipitation changes and for the last five “glacial terminations” in the last half a million years we may very well have found what has caused it exactly: the country size clathrate destabilisation that caused and preceded the giant Storegga landslides at the slope of the European continental plate between Norway and Iceland.(Bryn et al 2005). The last event (Mienert et al 2005). led to the extinction of the mega fauna (Mammoths, Mastodonts, etc). The mechanism: strong increase in oceanic evaporation due to effective ocean surface enlargement (bubbles, splash water) due to roiling of the methane gas and a strong surface water current radiating away from the event, disrupting normal patterns and sending warmer water to arctic areas
**********
So Did I mention what caused those CO2 spikes?
Picture that methane roiling in ocean also sending deep waters to the surface. Deep water is under high pressure and can contain (much) more CO2. So when the pressure is released at the surface, just like opening a coke bottle, the CO2 comes sizzling out escaping into the atmosphere. That’s why the CO2 spikes in those ice cores lags the isotope spikes slightly.
Refs:
Bryn et al (2005) Explaining the Storegga Slide Marine and Petroleum Geology, Volume 22, Issues 1-2, January-February, Pages 11-19
Mienert et al (2005) Ocean warming and gas hydrate stability on the mid-Norwegian margin at the Storegga Slide, Marine and Petroleum Geology, Volume 22, Issues 1-2, January-February, Pages 233-244
25 novembre 2005 at 3:00 PM
Upon seeing the host author, I know already that the rebutal will be for my post, that doesn’t show yet. Yes I’m familiar with the d15N/d40Ar behavior during the Bolling Allerod and PreBoreal spikes in the Greenland Ice cores. I’m also familiar with several palynologic studies that contradict the d15N d40Ar = temperature conclusion but support the precipitation hypothesis.
The question is what a dramatic increase of summer precipitation and it’s inclusion of warmer summer air in the snow would have on the d15N d40N.
[Response: Since you already know why you are wrong, it seems superfluous to mention all the other lines of evidence: increased % pachyderma in N. Atlantic sediments, higher d18O calcite in foraminefera, alkenone measurements, diatom assemblages, etc. etc… but I can’t help myself. Plus, ‘dry’ and ‘cold’ tend to go together in N. Atlantic region climate changes, so evidence of one is not evidence of the absence of the other. -gavin]
[Also, Gavin didn’t mention the beetle data from English bogs, showing Younger Dryas was not just cold, but that the mean annual cooling was especially in winter. These data are at least 20 years old and precede the ice core N-isotope data (and entirely agree with it). — eric]
25 novembre 2005 at 3:44 PM
According to EPICA, they drilled until they were 5 m above bedrock. Their limiting factor was the ice thickness at the drill site. One may therefore assume that thicker ice would allow for older ice cores.
[Response: In fact the Vostok core is deeper than the EPICA core: http://en.wikipedia.org/wiki/Image:Epica_do18_plot.png but doesn’t go so far back in time. What you need for a really long-time core is an ice dome (so no/minimal flow) and a low accumulation rate - William]
25 novembre 2005 at 4:13 PM
Re response 12
Gavin have you wondered why the oceanic sediment proxies respond so promply on the isotope spikes whilst the oceans behave like a slow higher order response system with eigen frequencies of centuries to millenium. Have you seen that the oceanic proxies actually seem to be leading the ice cores instead of lagging. Have you wondered why all those articles are full with unknown and “not understood”. Any idea what changes in salinity, p02, pH would to do benthic proxies? Any idea what massive clathrate destabilisation events would do to salinity pO2 pH etc but most of all the changes in response characteristics?
It’s all part of the puzzle, that could not be solved before knowing the complete picture.
25 novembre 2005 at 4:22 PM
re #11: Independent evidence that the oxygen isotope records are a reasonable proxy for temperature comes from temperature measurements of the ice made during the drilling of the core. The borehole temperature measurements confirm the interpretation of changes in oxygen isotope records as fluctuations in surface temperature.
25 novembre 2005 at 4:53 PM
re 15
The borehole temperatures (Greenland GRIP and GISP-2) are far too indistictive to show the Younger Dryas let alone other spikes. They make it clear that it has been colder 20-30Ky+ ago but you cannot find the border on that very shallow graph. It does not show when exactly the jump to warming happened.
Consider this, the last glacial maximum was 18-22 carbon years ago (22,5-27 Ky cal Bp) after that many glacial proxies in America showed consideral warming and glacial retreat. But not a single indication in the isotope values. You had to wait to 14,700 Cal BP years (Bolling event), before there was any reaction. But together with the isotopes also the CH4 spiked as well as the precipitation in concert with all the next spikes, Bolling - Older dryas - Allerod - Younger Dryas - Pre Boreal. So if the great melting started earlier, confirmed by sea level proxies, to start at 19 Kyrs ago, why don’t we see the Last Glacial Maximum back in the greenland Ice cores? Why those late reactions?
Check the proxies I mentioned here:
http://home.wanadoo.nl/bijkerk/gisp-compare.GIF
[Response:It is indeed often said that the Greenland ice cores show a “late” deglacial signal. This is rather careless though, and not actually supported by the evidence. In fact, the Greenland isotope records have a minimum around 20 ka, just like the Vostok and other Antarctic ice cores do. Superimposed upon that are the higher frequencies ups-and-downs of the D-O events, which allow one to subjectively state that one has to “wait until 14.7 kyr B.P.” for the deglaciation to begin. But the ice sheets can only respond significantly to low frequencies, so it is the low-pass filtered version of the Greenland records you want to look at. And they look pretty much like Vostok. See e.g. Alley, R.B., E.J. Brook and S. Anandakrishnan. 2002. A northern lead in the orbital band: North-south phasing of ice-age events. Quaternary Science Reviews, 21, 431-441. — eric]
25 novembre 2005 at 6:00 PM
A proper legend for the graph would be nice, also.
[Response: Sorry about that. The figure shows a composite record of CO2 measurements from 0 to 650,000 years ago (last section is from the new paper), along with the deuterium measurements from Vostok and EPICA Dome C. - gavin]
25 novembre 2005 at 6:54 PM
Re #1: To see the detail on the graph, click on it to open it in its own window, then zoom in as needed.
(Gavin, I have a different problem, which is that the top of the second paragraph is somehow cut off by the graphic. The first line I can see begins with “Vostok core appears…” I’m running Windows Explorer on XP Pro (both up-to-date) and have a 15″ monitor, if that’s any help. I’ve noticed this same problem on a couple of prior RC posts.)
25 novembre 2005 at 8:43 PM
I would welcome any sensible challenge to the following comments.
After reading the leading article, I conclude:
- there is a strong correlation between global temperature and global CO2 concentrations;
- Neither the article, nor referenced documents, provide any indication on whether temperature influences CO2 or vice versa;
- the results do not help us predict future world climate;
- The statement: “who says climate predictions can’t be verified?” is misleading in that it implies that the quoted results back ‘climate models’. On the contrary, the predictions apply to conditions with zero human influence and provides no indication on the impact of manmade CO2 emissions on future climate.
[Response: I’ll step you through it. There is a clear correlation between CO2 and temperature (and Milankovitch forcing). Given the lag in CO2/CH4 to Milankovitch and temperature it is clear that climate influences CO2 and CH4 levels. Given separate studies in how cold the planet was at the peak of the last ice age given those values of GHGs and ice sheets etc. it is clear that GHG forcing is roughly reponsible for half of the glacial cooling (e.g. Lorius et al, 1990). Thus we have a classic feedback - climate influences GHGs (through ocean + biosphere interactions), and GHGs in turn influence climate (through the atmospheric greenhouse effect). If, given the Milankovitch forcing and how warm it was, carbon cycle models can correctly estimate how much CO2 was in the atmosphere, prior to the actual results being released, it implies the carbon cycle models have some skill at relating the three effects. And finally, since the atmosphere doesn’t care whether CO2 is man made or not, and given that Milankovitch forcing is small for the next few centuries, the same physics will likely work for the future as well. -gavin]
26 novembre 2005 at 3:44 AM
Re comment #19:
Gavin said:
Given separate studies in how cold the planet was at the peak of the last ice age given those values of GHGs and ice sheets etc.
Let me give an example of how cold the planet really was during the Late Pleistocene:
Alfimov et al (2001) Beringian Climate during the Late Pleistocene and Holocene. Quaternary-Reviews 20 (2001) 127-134:
Quote:
Here we demonstrate the possible use of the fossil remains of beetles in the weevil genus Stephanocleonus for Late Pleistocene and Holocene climate reconstruction.
“.that they feed on only a few species of plants and occupy habitats, with a relatively narrow range of environmental conditions.”
“The main range of these species is zonal steppe and mountain steppe of southern Siberia and Central Asia. As in the case of the weevils,
Three weevil species - Stephanocleonus eruditus, S fossulatus, and S. foveifrons, play important roles in the insect fauna of relic steppe biotopes. “.
The Pleistocene remains of these weevils have been discovered throughout northeast Asia. Stephanocleonus fossulatus and S. eruditus were common throughout the immense area from the Lena River to the Anadyr River; fossil remains of S. fovifrons have been found in the lower reaches of the Kolyma and the Indigirka and on Ayon Island
Present climate at northern limit of its range:
1200 - 10°C annual temperature sum. ….In N.E. Siberia, at 70°North now only 200-300°.
16°C mean July air temperature. ..In N.E. Siberia at 70°N now only 4-10°C.
26 novembre 2005 at 10:43 AM
Re 19.
On the link between Temperature and CO2
I would just like to add to Gavin’s reply that from basic physics we know that CO2 in the atmosphere exerts a direct warming influence (it helps trap infrared radiation). One of the things that the paleoclimate record tells us is there are no natural feedbacks in the climate system that will serve to entirely negate warming due to the CO2 and other GHSs we are adding to the atmosphere. This picture is also consistent with the fact that no one has ever came up with a physicaly plausible climate model (here meaning the full range from complex GCMs to simple “back of the envelope” conceptual models) that predicts that adding more GHGs will not raise the global mean temperature.
26 novembre 2005 at 12:08 PM
I’ll second Gavin’s comment regarding #19. The LGM situation provides the most direct evidence against the existence of some unanticipated stabilizing feedback that would ameliorate the response of climate to CO2 (e.g. Lindzen’s old cumulus drying idea, or his newer Iris idea). If such a mechanism existed, it would almost certainly work during LGM times as well as in the present. If that were the case, then the implication would be that models (without this mechanism) exagerate the cooling due to reduction in CO2 in glacial periods. However, WITH the CO2 effects, current models can come close to reproducing the observed degree of cooling. If some strong stabilizing feedback were added to the models, then they would NOT be able to reproduce glacial-era climates.
Study of the LGM gives a pretty strong indication that the range of CO2 sensitivity in the IPCC models can not be too far off the mark. There’s a lot of work underway now to tighten up this statement, so as to use the LGM behavior to provide some indication about whether the true climate sensitivity is near the lower or higher end of the IPCC range.
26 novembre 2005 at 12:57 PM
I think the relationship presented in #8 (ENSO compared to growth in CO2) means an acceleration in CO2 accumulation and global warming as oceans warm.
26 novembre 2005 at 4:52 PM
I’ve seen the contrarian argument before regarding warming preceding increases in GHGs, with the implication that this disproves AGW. I’m no climate scientist, but simple logic tells me this in no way serves to disprove the point that GHGs cause warming (the two are analytically separate issues) — and this latter has been well accepted for a long time re the natural greenhouse effect. The only issue remaining was whether the addition of our human GHGs could cause additional warming, and that has been long resolved enough for me to turn off lights not in use.
However, the idea, which contrarians seem to embrace whole-heartedly, that warming precedes (and thus causes) an increase in GHGs, is a very serious issue indeed, and points to the possibility of runaway global warming (positive feedback loops), which would make global warming all the more serious, by contrast to only GHGs causing warming. What it means is that my GHG emissions may have much worse repercussions — the harm that keeps on harming and harming and harming. (I don’t think this positive GHG-warming feedback loop is included in the “sensitivity” factor/calculations re human GHG emissions, but if it were or could be, then we’d be talking a much higher order of sensitivity.)
I wish some sincere policy-makers more concerned about people living the world than corporations amassing huge bank accounts in the very short run are out there reading about this serious issue, so that we can quit stalling and put forth massive efforts to reduce human GHGs — which by contrarians’ own admission are much more dangerous than merely causing increased warming (as previous thought), but that increased warming then causes increased GHG emissions, which cause further increased warming, which causes further increased GHG emissions, which cause….an so on.
The emperor is really wearing no clothes on this one. Contrarians better stick to the current fashionable cloak that AGW is happening, but it’s cheaper to adapt to it than mitigate it (I also have my arguments against that, as well).
26 novembre 2005 at 6:21 PM
Re: #24, “The emperor is really wearing no clothes on this one. Contrarians better stick to the current fashionable cloak that AGW is happening, but it’s cheaper to adapt to it than mitigate it (I also have my arguments against that, as well).”
Forgive me for injecting a tiny bit of black humour amongst the gloom into this discussion. If we keep to a business-as-usual scenario, we may all be joining the emperor and be wearing no clothes, as well, since it may be far warmer in the future and many of us won’t be able to tolerate the heat.
26 novembre 2005 at 7:57 PM
I thank Gavin for addressing my questions (no.19). However, I do not feel they are answered. Yes, there is a very strong correlation between historic temperature and CO2 concentrations, which seems to explain the success of predictions on the core results. I presume the reason for discussing the study was that it is assumed to support the case for AGW. I just don’t see this, but am happy to be enlightened. What am I missing? Milankovitch is not mentioned in the article or any of the links, so I don’t see why “he” is so significant in the response. My main point is that I do not see how the quoted study contributes to the case for AGW (regardless of what ’separate’ studies may show).
26 novembre 2005 at 11:32 PM
What this graph shows.
CO2 levels have been as high or higher than they are now four times in the last 400K years.
There is a regular pattern of rises and falls eight times over the last 650K years.
The most recent low point, 180 ppm was about 35K(thousand) years ago.
CO2 levels have risen steeply over that 35K year period, starting well before human
civilisation, and about 35K years before any significant human intervention in the
environment.
This graph shows conclusively that the CO2 levels at present are part of a long term trend
pattern on which humans have had no input or effect.
It is clear that our worry for the next 30 thousand years is what we are going to do, if anything
can be done, about the next ice age.
This graph is the end for the man made CO2 global warming theorists.
[Response: Errr…. not really. Current CO2 380ppm, highest value on graph ~290 ppm. Care to reconsider? - gavin]
27 novembre 2005 at 12:23 AM
#27 - “CO2 levels have been as high or higher than they are now four times in the last 400K years.”
Ah, right. Got it.
27 novembre 2005 at 1:03 AM
Re #27: The graph in question is on a scale of thousands of years. The rise in carbon dioxide levels from 270 ppm to 370 ppm in the last hundred years simply does not show on such a scale. This rate of increase is unprecedented (200 times as fast) for the time period of this graph, and clearly has a different cause than the Earth’s orbital variations. Global warming theory is not contradicted in any way by this information.
27 novembre 2005 at 1:26 AM
Gavin
You don’t have any ice core data that shows 380ppm.
You have Mauna Loa, but that is not really comparing apples with apples, is it?
[Response: I have Law Dome which overlaps and matches both Mauna Loa and the other pre-industrial ice core data. Highest value measured in an ice core 323 ppm, corresponding to around 1969 levels. So even the pure ice core data show values higher than any seen in 650 kya. -gavin]
27 novembre 2005 at 1:29 AM
Re 29
“This rate of increase is unprecedented (200 times as fast) for the time period of this graph”
As you put it, it’s such a big increase that it’s almost…..unbelievable?
27 novembre 2005 at 3:37 AM
This new ice core data has recieved much more media attention than the Vostok ice cores did when that ground breaking research was made public. Perhaps Katrina, and all the other storms this year will be marked as a tipping point that led to the American media waking up from the “some scientists” trance that they’ve been in for 10 years.
My question is: If one were to still be doubtful of the reliability of climate models and wanted to extrapolate from the ice core data, what result would today’s and projected greenhouse gases give?
27 novembre 2005 at 4:26 AM
Law Dome, the one where the age of the air is adjusted by 30 or 58 years depending, but not the 83 years like Siple?
You know it’s hard to believe that air and ice and CO2 can behave so differently, and yet the one thing that remains constant in all this is that the adjusted CO2 data from the latest ice cores always matches exactly the starting data from Mauna Loa.
Spooky that.
Especially when according to Richard Courtney http://www.john-daly.com/bull120.htm
“I recently visited Hawaii and observed the Mauna Loa site, and this has convinced me that measurements of carbon dioxide from that site are not indicative of “the well mixed background.” Mauna Loa emits carbon dioxide and is adjacent to Kileaua (the most active volcano on Earth). It seems very likely that Keeling’s carbon dioxide measurements are significantly affected by variations in emissions of carbon dioxide from Mauna Loa and Kileaua together with wind direction relative to Kileaua. Indeed, Keeling adjusts his data for effects of Mauna Loa activity and deletes data from his time-series for the periods when Mauna Loa was especially active (of itself, an admission that his data are not direct measurements of “well mixed background”). But his reports do not mention any adjustments made for effects of Kilaeaua’s activity.”
In November 1998 I had correspondence with Dr Curtis Covey (an IPCC author) concerning my severe doubts at the ice-core data. Referring to my dispute that it was correct for the IPCC to have transposed the ice-core data by 83 years, he said;
“… such displacements might be considered a somewhat arbitrary calibration that diminishes the significance of the fit between ice-core and modern measurements. At last week’s IPCC meeting I raised this general question with Haroon Khesghi of Exxon. Haroon referred me to Fortunat Joos of the University of Bern, who told me that this calibration is no longer used in recent work, and yet the remarkable agreement between ice-core and modern measurements continues.”
and more:
“I responded that I did not accept the 83 year transposition was acceptable. Diffusion occurs from regions of high to low concentration and, therefore, incomplete sealing of snow over an 83 year period would act like an 83 year running mean; it would not transpose all the carbon dioxide a similar amount in one direction. Also, if the IPCC has stopped using the transposition, what correction method is now used? And when will the IPCC publish this newly corrected data in place of the graph of historic atmospheric carbon dioxide concentration that it published in both its 1992 and 1994 reports ? I received no answer to these questions.”
[Response: Funny stuff. Generally speaking cutting-and-pasting from the wackier of the sceptics sites is not a very credible line of argument, but let me take this as a teaching moment. Law Dome and Siple Dome have different accumulation rates (which are much higher than from Vostok or EPICA). Air mixes through the firn down to the depth at which bubbles are closed off. Therefore new air is trapped in ice that is significantly older. This depth occurs in ice of different ages - i.e. younger ice in higher accumlation cores, and this leads to the ‘ice-age/gas-age’ difference, which will be different in different cores (it would be ’spooky’ only if it were the same). This age difference has nothing whatsoever to do with the filtering of the atmospheric CO2 concentration - that instead is related to the strength of the wind-pumping in the firn and the process of bubble formation and is much much shorter (around 20 years). Oh and by the way, the Mauna Loa record started in 1957 when CO2 was only around 315ppm, and shows almost the same annual values and trend as the South Pole data started at the same time. Spooky that…. -gavin]
27 novembre 2005 at 5:18 AM
Re 11: Gavin, you may be interested in this thread:
http://www.ukweatherworld.co.uk/forum/forums/thread-view.asp?tid=25682&posts=1#M299767
27 novembre 2005 at 5:58 AM
Re #30: I don’t mean to pile on (much anyway), but strictly speaking those would need to be snow core data to show 380ppm.
Re #31: Mark, we are putting a bunch of CO2 into the atmosphere very quickly indeed. Nature doesn’t do that. Ironically, the current rate of CO2 increase has been described by at least one skeptic site as so small as to be trivial. It’s all a matter of what you’re comparing it to, I suppose.
[Response: Mark ought to read our earlier post on “How we know that recent CO2 increases are due to human activities”. -eric]
27 novembre 2005 at 2:02 PM
Can anyone direct me to references which describe how EPICA deals with the storage and transport of ice cores to analytical labs in Europe? I am particularly interested in steps they took to reduce ambient air contamination. The earlier EPICA article does not address this.
[Response:There were a bunch of studies, some 20 years ago, looking into the possibility that CO2 concentrations in ice cores change with storage and transport of cores. The findings are that as long as the cores remain below -10C (which all of us who work with ice cores lose sleep over, and are very careful about), there is no measureable change, even after many (10+) years. Consequently, for gases, the major concern is simply the preservation of the ice at cold temperatures, and the avoidance of breakage. I doubt the EPICA folks have bothered to publish anything new on this, as it is all very well established protocal, which is why the papers you are looking at don’t address it directly. You can no doubt find references to the methods for CO2 measurements within the references sections of the papers though. I’ll take a look and get back to you on this site. Basically, the rules are: keep it frozen; do your analyses on ice that is in the center of the core, after removing the outer part of the core, to miminize any possible contamination that might result from handling.–eric]
27 novembre 2005 at 2:51 PM
Where is the supposed “water vapor feedback” in the ice cores temperature record? As CO2 concentrations rise, aren’t we supposed to see a magnified effect on global temperatures because the GHG warming is supposed to cause the atmosphere to hold more water vapor?
27 novembre 2005 at 6:04 PM
Re: #37, “Where is the supposed “water vapor feedback” in the ice cores temperature record? As CO2 concentrations rise, aren’t we supposed to see a magnified effect on global temperatures because the GHG warming is supposed to cause the atmosphere to hold more water vapor?”
This may be identified by the thickening of Antarctica and Greenland’s existing ice cap, as a result of increased precipitation due to surface temperature and SST increases.
As for a “‘water vapor feedback’ in the ice cores temperature record”, water vapour cannot be identified in ice cores since the water vapour condensed and precipitated, allowing the annual layers of ice to form.
27 novembre 2005 at 8:26 PM
After carefully matching the CO2 gas age to the nearest ice age, the change of CO2 is some 8 ppmv for each change of 1 K in reconstructed temperature (or vv.) for the Vostok ice core over the full 420,000 years period, see regression here. The Dome C record seems to confirm this correlation between CO2 and temperature.
About the chicken-and-egg question, there is little doubt that in the Vostok ice core, there is a lag of several hundreds of years of CO2 after the start of the temperature increase during a deglaciation and several thousands of years after the start of a glaciation. See: Fischer ea.. For more recent time periods, before the industrial revolution, I have only found lags of CO2 after temperature changes: for the 60-20 kyr BP period in the Taylor Dome ice core, for the Younger Dryas event (comment on stomata data, not on the Net anymore), for the past 1,000 years (Law Dome, a lag of app. 50 years after temperature changes - temperature data not available in the Law Dome database).
But in many cases, there is an overlap of temperature and CO2 trend changes. That is e.g. the case for all deglaciations, where the lag is 600 +/- 400 years, but the total transition period is some 3,000 years.
There is one exception in the whole Vostok trend: after the onset of the last glaciation (some 120,000 years ago), the CO2 levels remained high, until the temperature was near its minimum, before CO2 levels started to decline (see trend and data at NOAA. There is no measurable influence from a change of 50 ppmv CO2 on temperature, while, according to climate models, halve of the 6 K cooling (and thus also for a 10-12 K warming during deglaciations) should be attributed to the change in GHGs (and their feedbacks).
[Response:This analysis is out of date. First, while the CO2 data are very precise measurements of exactly what is of interest (CO2 concentrations), the stable isotopes provide only a fuzzy estimate of temperature. This has been looked at very carefully, and the best evidence (Cuffey and Vimeux, Nature, 2001) shows that the supposed lag at 120,000 is an artifact of the changing relationship between isotopes and temperature. Their calculations pretty much kill of this much-loved example of the climate change skeptics — eric.]
The lag of CO2 is probably not an artefact of problems with matching of ice age with gas age, as CH4 (methane) levels more closely follow the temperature trend. Neither does the recent correction of the reconstructed temperature by Jouzel ea. (last page) change the timing of the events, only the amplitude of the temperature trend is changed.
This doesn’t mean that the CO2 increase in recent times has no influence on temperature, only that relative small changes in CO2 level have no measurable influence on reconstructed temperature from ice cores, and that current models probably overestimate the influence of CO2 (+ feedbacks) and thus probably underestimate solar influences.
27 novembre 2005 at 9:30 PM
#39 Points out..”This doesn’t mean that the CO2 increase in recent times has no influence on temperature, only that relative small changes in CO2 level have no measurable influence on reconstructed temperature from ice cores, …” I am not sure what small changes are in your mind but in recent times we are hardly talking about small changes in CO2 levels as noted by Thomas Stocker “We find that CO2 is about 30% higher than at any time, and methane 130% higher than at any time; and the rates of increase are absolutely exceptional: for CO2, 200 times faster than at any time in the last 650,000 years.” Look at how slowly CO2 rose at the end of each glacial period compared to now. In the Dome C core EPICA 17,000 BP it was 190 ppm and took 5400 years to rise to 250 ppm.
27 novembre 2005 at 10:55 PM
“This may help address some of the ideas put forward by Ruddiman (2003, 2005), and also help assess how long our current warm period is likely to last.”
How may it “help assess how long our current warm period is likely to last”?
I think this current warm period will become warmer and warmer, and hotter and hotter, for tens of thousands of years.
What do you think?
27 novembre 2005 at 11:20 PM
For scientific purposes the graph is excellent and exciting; for public communication purposes it could be better.
Al Gore drew the anthropogenic CO2 perturbation on a 100KA graph in his book Earth In The Balance. Al Gore is a politician, not a scientist. In this case, I don’t intend that as a criticism. Politicians’ skill is to communicate to a very broad range of people.
There is an extraordinary spike in CO2 that is essentially vertical at the present century on the scale of the graph shown. It would already double the range of the graph. It’s not shown on ice cores because it’s too young to appear in ice cores.
Comment #27 shows how thoroughly misunderstood the GHG situation is, and how eager some people are to misunderstand it. A helpful thing that realclimate could do in this case would be to publish the graph with the addendum of the observational record.
[Response: For instance, the wikipedia image here -gavin]
28 novembre 2005 at 4:19 AM
Two points.
The CO2 measure from the ice cores is an estimate. There is no actual data from prehistoric periods. The Vostok and other samples may be useful in showing long time scale fluctuations, but they are not absolute evidence of the actual CO2 level at any time.
The CO2 measurements from Moana Loa and the others depend on the accuracy of the measurement, and the equipment used. As many people have commented, the relative change in detected CO2 is very rapid, and not explicable in terms of any naturally occurring phenomena.
Therefore, look at the actual collection and calibration of the CO2 data.
It has been pointed out that there are several sites measuring CO2, but the oldest is Moana Loa.
I was interested to find that the Moana Loa measurements from 1991 to 1996 have recently been re-calibrated.
WMO/IAEA Experts Meeting Boulder 19-22 September 2005
Revision of the international calibration scale for CO2-in-air: WMO-X2005.
Pieter Tans1, Conglong Zhao2, and Kirk Thoning1
1 Climate Monitoring and Diagnostics Laboratory, NOAA
2 Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder
Also that “….that there has been no drift of the mole fraction, cannot be rejected for any of the Primaries with the statistics we have.Therefore, we assume that,there has been no drift until now, and the assigned value for each primary is the average obtained for that cylinder during all CMDL calibration episodes. The above does not imply that the defined WMOScale has not drifted“.
…”In June 2002 CMDL received revised numbers from Scripps for the four calibrations by them of our fifteen WMO Primaries that they had carried out from 1991 to 1999. Their revised scale was called X99A.”
…..”Based on the assumption that the fifteen WMO Primaries have been stable, we have re-assigned a constant value (the average of the measured values during the six CMDL calibration episodes) to each of them going back to 1994. We call this revised scale WMO-X2005.”
Report here
I doubt if anyone can say any of this data is robust enough to make billion dollar life changing decisions on.
[Response: Hmmm… serious stuff. A revision of the scale based on better absolute measurements. And how much is this difference? a maximum of 0.16 micromol/mol. - In a more usual unit, that is 0.16 ppmv, compared to an observed change since 1957 of over 60 ppmv. So less than 0.3% error…Hmm. - gavin]
28 novembre 2005 at 4:40 AM
The statement that CO2 levels today are higher than those found in the ice cores,highlighted in the press, ignores the effect of long term diffusion which would have the effect of lowering and smoothing out the peaks. It is noticeable that the peaks and troughs are less sharp in the older data. I have failed to find data on the diffusivity of CO2 in ice, apart from comments on the effect of partial consolidation, the so-called time lag effect.It is probable that diffusive spreading has smoothed the concentrations to some extent, and raises doubts about statements about exeptional levels and rates today.
[Response:The smoothing you see is because of the thinning of ice layers through time, so that for each fixed amount of ice in a sample, it represents a longer amount of time. Higher resolution data is possible, but as seen in Delmotte et al, 2004, for Vostok, that increases the amount of variability, but does not affect the long term means seen in the current data. -gavin]
28 novembre 2005 at 5:06 AM
More on calibration.
Department of Commerce, Mountain Administrative Support Center, Procurement Division, MC3, 325 Broadway, Boulder, CO 80303-3328
“The calibration shall consist of a determination by the Scripps manometer of the mole fraction of CO2 in each NOAA reference gas cylinder…”
“…it is the intent of the Government to award a sole source contract under the authority 41 U.S.C. 253 (c)(1) to the University of California at San Diego. Scripps Institute of Oceanography, 2314 Ritter Hall, LaJolla, CA 92093, as this source is considered to be the only responsible source and no other type of supplies or services will satisfy agency requirements.”
Not only were Scripps AKA Moana Loa the only collector of data, they were the only calibrator of the equipment.
If Scripps was wrong, then there was no independent check of the calibration, because they did it themselves, and all the other later CO2 measurers presumably had their equipment calibrated from Scripps.
The average increase Moana Loa measured was 1.3 parts per million by volume. That is 0.00013%.
Anyone confident that their measurements and calibration errors weren’t responsible for that?
[Response: Yep. since the calibration uncertainties are an order of magnitude smaller, plus they are uncertainties on the absolute scale - uncertainty in a difference between two samples is much smaller. You are really grasping at straws here. -gavin]
28 novembre 2005 at 6:33 AM
Re #40,
All depends of the influence of CO2 (and other greenhouse gases) on temperature (and in the case of CO2 on ocean pH and carbonate level).
From the ice cores we can learn that a temperature increase of 1 K is correlated with a CO2 increase of 8 ppmv. Thus the current temperature increase since the LIA (0.2-1 K, depending on the chosen reconstruction) is only responsible for a small portion of the near 100 ppmv increase in CO2 since the start of the industrial revolution.
The direct influence for a CO2 doubling is some 0.68 K (or 0.23 K for the current level), based on its absorption bands. All the rest is feedbacks, of which water vapour is the main positive response. But clouds (depending on thickness, height, season, latitude) seem to give a general negative response. That makes any projection of the climate models rather problematic, as clouds are the main origin of the large variation in range for a CO2 doubling.
As the start of the last glaciation indicates, if the influence of 50 ppmv CO2 + feedbacks is not measurable (direct influence: some 0.12 K, which is within the measurement error margins), that points to an overestimate of the feedbacks in most of current models. The real influence of a CO2 doubling on climate thus probably is at the low side of the IPCC range…
28 novembre 2005 at 6:43 AM
If I recall correctly Andre, you spent a considerable amount of time on the BBC boards attempting to tell me that the Younger Dryas wasn’t all that cold after all. I pointed you in the direction of a number of multiproxy studies that showed you to be wrong. Have you looked up the Gerzensee and Krakenes articles yet? I guess not.
Oh and if you are ever in the UK, why not pop over to East Anglia. We have Younger Dryas age sites, in southern England, that have evidence for frost shattering. I’m no periglacial expert, but I think this means it was pretty cold. As I told you last time.
28 novembre 2005 at 6:50 AM
The paper to which eric refers:
Atkinson, T.C., Briffa, K.R. and Coope, G.R. (1987) Seasonal temperatures in Britain during the past 22,000 years, reconstructed using beetle remains. Nature, 325, 587-592.
It was cold here in the Younger Dryas. End of story. The only way you can argue otherwise is by cherry picking the odd study that suggests a slightly more complex spatial response.
Oh and while I remember, we had ice sheet growth in Scotland and Wales during the Younger Dryas. This tends to occur when its cold. I recommend checking out the literature. Its only been around since the 1920s.
[Response:Thanks! I couldn’t find that reference. A nice paper.-eric]
28 novembre 2005 at 7:22 AM
Re 43. There are ice wedge casts of younger Dryas age in the British Isles. For ice wedges to form at this time would require mean annual temperatures of below -6 C.
28 novembre 2005 at 1:53 PM
#44 A study (van Hoof et al., Tellus, 2005) on the D47 core claims a possible short term diffusion effect of about 20ppm (short term CO2 amplitude hidden by firn diffusion) depending on accumulation and temperature. The recent 80ppm raise is very hard to hide in ice cores if this is what you suggest.
Georg
28 novembre 2005 at 3:02 PM
Re #46 — where did “The direct influence for a CO2 doubling is some 0.68 K (or 0.23 K for the current level), based on its absorption bands” come from? According to Houghton (2004) the direct influence for a CO2 doubling alone is 1.2 K. And that’s down substantially from Manabe and Wetherall’s (1967) estimate of 2.0 K.
28 novembre 2005 at 4:45 PM
On the subject of ice cores, I saw a talk by JP Steffensen recently on the current status of the NGRIP timescale. The results are pretty bloody exciting - they’ve got major Deuterium excess changes at the onset of the Younger Dryas occurring in a year. A year!
28 novembre 2005 at 5:36 PM
Gavin #43
I think you may have missed the point.
“….that there has been no drift of the mole fraction, cannot be rejected for any of the Primaries with the statistics we have.Therefore, we assume that,there has been no drift until now…… The above does not imply that the defined WMOScale has not drifted”.
They are talking about an unknown amount of “drift” possibly (probably?) over and above the amount they have recalibrated for.
Their own page (extracts shown as follows) on preparation and stability is littered with examples of drift potential, and those are only the ones they know about now. What others remain as yet undetected?
The manufacturing target of the CO2 test canisters is “within 5 umol/mol for near ambient concentrations.” But this appears to be greater than the annual measured change of 1.3 ppmv.
“The zero air from both trapping agents was tested and found to be less than 5 umol/mol for CO2.”
“Aquasorb is phosphorus pentoxide (P2O5). However, CO2 was found to increase by 2-5 umol/mol with this new drying material. This problem and the safety issue of cycling phosphoric acid in a high pressure system prompted the decision to discontinue use.”
“The steel cylinders used in the past exhibited too much drift in CO2 mixing ratios, with half of these drifts on the order of 0.05 umol/mol CO2 per year [Komhyr, 1985] could be at different rates or of a different sign in each cylinder.”
“There are some cases (8%) with evidence of drift greater than 0.045 umol/mol per year. For this reason, it is recommend that standards be recalibrated during long use and at the end of their useful volume. The drifts, as shown in the histogram, cannot be predicted. Drift in most of our standards is often undetectable for histories of less than 2.5 years. In some documented cases the drift was attributed to H2O mixing ratios greater than 5 umoles mole-1, stainless steel valves, or valves with packing materials, which preferentially absorb trace gases. There may be an increasing trend in the CO2 with decreasing cylinder pressure below 20 atmospheres. This is different in each cylinder or may not be present at all.”
“There have been some cases of major drift (0.05 per mil 13C per week) of the CO2 stable isotopes, attributed to the Teflon paste used as the cylinder valve sealant and also to unknown regulator contamination. There may be some evidence for long-term drift of CO in aluminum cylinders as exhibited in smaller high-pressure cylinders [Paul Novelli, CMDL, personal communication, 1999]. This drift, however, is on the order of the measurement precision and has not yet been well quantified.”
“Drifts have persisted for months due too evacuating the cylinder down to vacuum before filling. Drifts due to spiking, discussed below, have been eliminated by filling the cylinder immediately after spiking and filling the cylinder laid down. There is no evidence to show drifting due to the filling process described below. As a result of these experiences and to remain conservative about long-term unknown effects, the following steps have been adopted by CCGG…”
“The zero air is created with specific chemical traps for each trace gas. Carbon dioxide can be removed with sodium hydroxide, Ascarite (Thomas). Carbon monoxide is removed with Schutze reagent. The zero air from both trapping agents was tested and found to be less than 5 umol/mol for CO2..”
“Occasionally the targeted concentration is missed by an amount that requires adjustment. If the concentration of the standard is closer to ambient than the target concentration, it is easiest to blow this off and start over. Experimenting with introducing small volumes of high pressure (high or low concentrations) into the air stream have proven very time consuming due to the time necessary for the cylinder to become evenly mixed before obtaining a usable measurement from the standard.”
“There is evidence that as the volume of pressurized air is used up, the trace gas can come off the walls in disproportionate amounts. This has sometimes been seen in cylinders with CO2 when a standard is used at pressures below 20 atm. Thus CO2 mole fraction may increase with pressure loss. This effect is variable and may not be measurable in all tanks.”
NOAA Technical Memorandum ERL-14
CMDL/CARBON CYCLE GREENHOUSE GASES GROUP STANDARDS
PREPARATION AND STABILITY
Duane Kitzis
Conglong Zhao
http://www.cmdl.noaa.gov/ccgg/refgases/stdgases.html
Remember they are claiming to show accurately changes of 1.5ppmv over a year.
If they have made a mistake, or there is drift in the primary calibration, then all the figures produce by this method may be wrong.
Science should be about independent testing and replication, but if all the testers are using the same equipment, using the same calibration of the primary, then there is in fact no independent verification of the method or the calibration.
See also http://www.cmdl.noaa.gov/ccgg/refgases/reg.guide.html Guidelines For Standard Gas Cylinder and Pressure Regulator Use, for how complicated all this is to work in practice.
28 novembre 2005 at 8:35 PM
One comment and one question:
Comment: Aren’t we fighting Occam’s Razor here? We keep coming up with reasons to explain away the obvious: There is a reason for the CO2 / temperature lag that still supports man-made climate change. There is a reason that even though CO2 and temperature patterns clearly are cyclical, this time it is different. Even though many scientists a priori believe in man-made climate change but design, run, and analyze their own data, their results are still considered objective. At what point do we say enough is enough and that we really don’t know?
Question: We know that large volcanic eruptions can cause 1+ year winters and yet nature adapts. We know that the earth makes large swings in temperature on its own, albeit over a long period of time. We know that another ice age is all but inevitable. So isn’t it plausible that IF there is man-made global warming, nature will adapt? For all we know, in 500 years, the bigger concern could be a new ice age, right?
[Response:Of course “nature will adapt”. But this is like saying that during the Great Depression, the economy “adapted”. If you are the particular working stiff or particular plant, animal, or economic system affected, you might not personally benefit from the long term adaption. Indeed, your argument is a bit like saying there is no reason to fight infectious disease, as eventually evolution will take over and some people will survive — i.e. society will adapt. Your suggestion is neither a scientific idea, but a philosophical idea and not a very well thought out one at that. Sorry to be harsh, but you are trodding on very well covered and uninteresting ground. As for the point about volcanoes, you are confusing high frequency forcing with low frequency forcing. If I hit my car, it shakes but doesn’t move. If I apply slow, steady pressure, I can move it. That’s the difference between high and low frequency forcing. The anthropogenic excess greenhouse effect is all about the latter. –eric]
28 novembre 2005 at 9:52 PM
Re #53
Most of the cited drift discussion is irrelevant as it pertains to particular cylinders, not the overall measurement system. In any case, there are multiple lines of independent corroborating evidence (like isotope ratios) as well as good physical reasons to expect atmospheric concentrations to rise (burning 6e9 tons of fossil carbon per year). It is healthy to consider the possibility of drift, but silly to postulate it in absence of any evidence. You might as well argue that all our measurements have drifted because the standard meter in Paris shrank.
[Response:Agreed. Furthermore, one can take an off-the-shelf diode laser system (and there are hundreds of these in circulation and measure CO2. You will get 375+ ppm CO2 if you do this outdoors. If you had done it 100 years ago you would have gotten 300 or so. There is a huge huge change, easily measureable even on a poorly calibrated instrument. This is not a difficult measurement. For context, in our lab we regularly measure differences that are 1000 times smaller. –eric]
28 novembre 2005 at 10:10 PM
#54 - “For all we know, in 500 years, the bigger concern could be a new ice age, right”?
Wrong.
http://en.wikipedia.org/wiki/Paleocene-Eocene_Thermal_Maximum
28 novembre 2005 at 11:07 PM
Re #46: Ferdinand, what is the basis of your statement that “The direct influence for a CO2 doubling is some 0.68 K”? The IPCC 2001 report (section 1.3.1) claims 1.2 K, before feedbacks. If you have different information showing the real value is only half that much, I would like to know what it is.
28 novembre 2005 at 11:30 PM
Re #54
Check google scholar and you’ll find that the time scale for the next ice age is more like 500 centuries than 500 years. From the perspective of immobile species and long-lived infrastructure, there’s a huge difference between a rapid multidecadal temperature increase and the transient from a volcanic eruption. Nature always adapts, but the process may not be painless.
29 novembre 2005 at 12:02 AM
Re 55
So you accept that some of the drift discussion is relevent. Thank you.
Some you say is irrelevent because it relates to particular cylinders, but particular cylinders are what are used in the measuring process.
As to corroboration by isotope ratios, it seems also to be an inexact science::
Hitoshi Mukai (NIES, Japan)
Many laboratories…are analyzing carbon and oxygen isotope ratios of atmospheric CO2 to study carbon cycle on the earth….However, previous inter-comparison activities like CLASSIC clearly showed difficulty in obtaining the same results when different laboratories analyzed the same sample1). Although there are many laboratories involving CO2 isotope analysis, there has been no handy reference material to compare their scales to each other. http://www.members.aol.com/mhmukai/WMOreport.htm
As to the “good reason to expect”, if one goes into these things prejudging the outcome then it is no surprise that the expected outcome is achieved.
“You might as well argue that all our measurements have drifted because the standard meter in Paris shrank.”
Well if we were still using the original Paris meter without knowing it had shrunk, then we would indeed be getting our sums wrong.
29 novembre 2005 at 1:32 AM
re #54: Your perception that things are in doubt which in fact aren’t in doubt at all seems to be causing your razor to cut the wrong way.
We know from first principles that all else equal, a planet with more greenhouse gases in its atmosphere will be a warmer one at its surface. We know from simple mass conservation arguments that we are causing a huge relative shift in the concentration of such gases.
The simplest expectation is a warming surface and a cooling stratosphere. We also observe about the right amount of surface warming and stratospheric cooling. People who allege that this is mere coincidence have a whole lot of ’splainin’ to do. Why didn’t the CO2 cause warming, and if it didn’t what else did? And what about that stratosphere?
I am glad you appeal to Occam, but I suggest you not appeal to willful ignorance in the process. You need to look for the simplest explanation that actually accounts for the evidence. Throwing away evidence is not the idea at all.
Finally, I think scientists, by definition, have no a priori beliefs in anything, and am very disappointed that you make an argument based on an assertion to the contrary.
Scientists, actually, rather like surprises. It gives us something to think about.
29 novembre 2005 at 1:45 AM
re #53; Your argument might carry more weight had you not signed it with the same name as you used in the demonstrably uninformed comment #27. It’s clear you are inexpert about the basic facts of climatology. So why, then, are you making assertions rather than asking questions? Are you interested in the facts of the matter, or have you already chosen a policy position and therefore seek to get the facts to conform?
Anyway, exactly where do you propose the excess carbon flux from fossil fuels is going, and why do you suggest the measurement curve is trending sharply upward even though the excess carbon is going some mysterious somewhere? (Obviously measurement error won’t account for the consistent trend.)
29 novembre 2005 at 5:57 AM
Re: #56 and #58
500 years was a a number I rather rashly through out there - my mistake. What I am referring to is the belief among some scientists that we are in a brief warming period between glacial advances. I believe there was an article in Nature several years ago about a European study that stated the next ice age may occur within the next 10k to 20k years. If interested, I can dig it up in my web bookmarks and post it.
Re: #59
Starting with last first: the definition of a scientist doesn’t create reality, and I find it naive to believe that all (or even most) scientists start with no a priori beliefs, especially those involved with climate change research. Why do many students in college choose to study environmental sciences in the first place - isn’t it because many are concerned about climate change and the affects man is having on the environment? While admirable, this also means that these people do have preconceived ideas, and hence strict, structured scientific methodologies need to be followed in order to help ensure objective results.
And while there are charges that global warming skeptics receive funding from mining and oil companies and are therefore biased, scientists on the other side of the fence receive funding from environmental groups and government organizations, both of which gain publicity and power when research supports the existance global warming - it gives reason for these organizations existance. Would Al Gore have pushed for funding for scientists who repeatedly had solid research that showed global warming wasn’t occuring?
Let me state that I used to believe man-made global warming was fact. However, when I started looking at more and more historical data from different studies, my skepticism grew. Perhaps I am ignorant in my observations, and I am surely not aware of all the research that exists on climate change. So I propose this: I will list the data / research that has influenced my current position, and perhaps others can post reasons / links that discredits this research.
1. Vostok data: to me, it looks like we are in an upwards swing of a warming pattern that will eventually turn the other way. albeit we are talking in 10k’s of years.
2. Temperature data from the NOAA (http://www.ncdc.noaa.gov/paleo/pubs/briffa2001/briffa2001.html): In both plates 2 & 3, many of the trendlines don’t show anything different from what we see over the last 1000+ years. While some do, it hardly seems conclusive. Am I missing something?
3. Other things such as the earth’s orbit, tilt, and electromagnetic fields also can play into global temperatures, along with volcanic eruptions, solar events, etc. Have these all been ruled out? And if not, isn’t it possible that temperature increases caused by these factors also increase greenhouse gas levels, ala the “lag theory”?
4. How do we know at what point temperatures will level off, even with a continual increase in greenhouse gases? Will it increase linearly forever? And how can we really measure this, given all the elements at play?
5. Assuming humans are creating an increase in greenhouse gases, isn’t it possible that the earth will counter balance these actions? For example, there is a theory that an increase in CO2 would cause an increase in plant life, which then reduces the CO2, etc. Is this not realistic?
6. Large volcanic eruptions like Krakatoa in the late 1800’s reduce temperatures by a signifcant amount for several years, but temperatures right themselves shortly thereafter.. Hence, the argument that by slightly affecting temperatures over a period of several hundred years humans could cause long term damage to the earth seems less plausible to me.
8. From a philosophical perspective: if the goal of fighting global warming is to help mankind live well on planet earth, wouldn’t we be better off using our economic, political, and scientific resources to fight the preventable diseases that cause the deaths of millions of chilldren every year?
29 novembre 2005 at 7:57 AM
Re: 62
In terms of being between glaciations, that is pretty much the point of the whole article. It appears that the current interglacial would come to an end in 10-20,000 years were there no man made pertubations.
When it comes to scientific bias; this is why we have the whole peer review process. Science does abandon cherished ideas when they are demonstrated to be false. But as an opposite argument - given the stance of the current US government on climate change, I would strongly suspect that any national lab that started coming out with countervailing evidence would get a big funding hike. And this whole point is irrelevant until someone actually comes up with evidence that climate scientists are systematically modifying their results to support a given conclusion.
TO your numbered points:
(1) If you go out and find a temperature record of the past 10,000 years, you will see that temperatures maxed out arounf 5-6,000 years ago and went into a very slow decline from then. You can see this in the graph attached to this article - the highest temperatures are attained just after deglaciation. It is incorrect to think that we are surrently in a natural long term warming pattern.
See: http://www.aip.org/history/climate/xCampCent.htm
(2) You are missing the point that local temperatures don’t all have to change.
(3) All of the things you mention (Apart from ‘electromagnetic fields’) are included in current models, although thinhgs loke orbital changes are far too slow to account for the observed warming. The idea that GHG concentrations can lag warming that started from other causes is actually very bad news, since it implies that human induced warming could lead to even more natural GHG release.
(4) Temperatures will not increase in a linear fashion, and we don’t know if they will level off. Of course, most of the uncertanty here is on the upside.
(5) There is a vast amount of evidence showing that humans are increasing GHGs (Including some older articles on this site). About half of the emissions are taken up by the biosphere. It is highly unrealistic to think that all emissions could be taken up; that would imply that CO2 concentrations could never change for ANY reason.
(6) Most species can survive short term transient effects; long term climate zone shifts are a different matter. However, for Humans, the biggest problem is that many of our cities - representing vast investments of capital and materials - may either vanish below sea level or lose their water supply and become uninhabitable.
(8) That is in many ways a false dichotomy; it assumes that reducing GHG emissions actually costs money, to start with.
Here is something that occurs to me on reading your post - in a series of points, you are making some fairly scattergun arguments. Is this a real position, or simply using the rhetorical tactic of flinging as much mud as possible in the hope that some sticks?
29 novembre 2005 at 1:16 PM
Re #62, #63: “flying as much mud as possible”. Exactly the problem.
There is no coherent intellectual or scientific position with which we find ourselves arguing. Indeed, we don’t want to “argue” in any sense commonly understood by legal and political types. We want to consider and present the bulk of scientific evidence, including the parts that are well-understood and the parts that are in question.
That is why it is a good idea for the editors of the site to refrain from making any policy recommendations. As a community it is our obligation to help the policy sector and the public to understand the evidence. In the face of deliberate opposition to this goal, it is our obligation to try harder and in a more sophisticated way. While as individuals we may prefer one policy or another, as scientists our obligation ends once the state of knowledge is reasonably well perceived by the policy sector and by the general public. On the other hand, as long as confusion abounds, history clearly shows that we are morally required to try to correct it. Unfortunately, we have not been doing a good job of this. The culture of the geophysical sciences did not emerge in the context of deliberate obfuscation in which we find ourselves today, and so we find ourselves needing to develop new skills.
The main tactics of the obfuscation are 1) to try to present the appearance of a scientific debate on matters where there isn’t any and 2) to try to attribute political motives to the scientific community, where any effort to elucidate the high degree of confidence that has emerged in various important matters of immediate policy importance is deliberately conflated with advocacy.
People who use expressions like “scientists on the other side of the fence”, or “used to believe in global warming” or other such nonsense tend to spend a great deal of attention quibbling with various points. Most of the quibbles are of marginal importance (did Mann et al keep sufficient records of their work in the mid-90s to replicate their results exactly?) or are utterly without rational support (could the abrupt increase in CO2 in the 20th century somehow be a measurement artifact?). The objective of this nonsense is to create the appearance of a debate. Many people, as a result, believe in good faith that there is a debate, and may in good faith propagate the confusion. Something debate-shaped emerges, but it’s a travesty of a debate.
The exact import of all the evidence continues to be a fascinating scientific field and one with a gerat deal of both intellectual merit and practical consequence. We would like ot discuss these matters here. Instead, we get a barrage of disconnected and hostile questions.
The most important point is that there really is no fence to be on the other side of. There will always be outliers in the distribution of scientific opinion on any open question. It does very little good, morally or intellectually, to draw a fence around those outliers whose opinion expects the least impact from anthropogenic change and cast this as some sort of meaningful debate between opposing schools of thought.
It’s certainly possible that a scientific question can have a lumpy distribution, and that there might be competing schools of thought, but it simply isn’t the case in the climate sciences today, especially as regards the policy related questions that the public seems to think are our only obsession.
The few remaining well-informed people who are outliers on the question as to whether restraints on net CO2 emissions are timely do not form a meaningful cluster of opinion and they present no coherent theory. Fossil fuel interests who are motivated to delay the policy response make the best of their dwindling intellectual resources. (That they are dwindling is unsurprising, as evidence continues to pile up that the mainstream view that emerged in the ’80s on anthropogenic climate change is essentially correct.) They try to drum up a ‘debate’ so that they can continue to extract value from their property as long as possible without restraint. One could imagine more sophisticated ways for these interests to protect their financial positions, and indeed some corporate energy interests are doing so, but in fact it is clear that some of them are resorting to a rather crude and morally dubious approach of muddying the waters of honest debate based on facts with the pollutant of manipulative argument designed to support a particular political agenda.
The reasons for their unfortunate success in creating something that looks at first glance like a legitimate debate are well outside the range of topics appropriate for RealClimate, but the fact of their success is obvious from the sorts of discussions that appear here.
There is currently no serious competing theory to the scientific mainstream on this question. That is why the critiques of the policy-relevant aspects of the science are inconsistent and incoherent.
Even more striking is the complete absence of sensible critiques of any aspects of the intellectual core of the discipline. If we were so deeply wrong as many wish to believe, there would have to be some very fundamental and interesting core error in our reasoning. No one tries to find any such a thing. There is only tedious sniping.
29 novembre 2005 at 1:49 PM
RE #62, point 8: I’m in favor of recycling, but in the case of this and other specious arguments deriving fron Bjorn Lomborg I’m thinking source reduction might be the better approach.
On the point, though, it might be worth considering that we have the resources to deal with the disease problem you describe right now, and simply choose not to. You may be interested to know that one of the near-term impacts of global warming is to make this disease problem worse.
29 novembre 2005 at 3:24 PM
RE: 64
Thanks for your responses - I appreciate the discussion and my intention is not merely to ruffle feathers but rather to foster open debate.
I agree with your comment that this should not be a policy discussion, but a data-centric discussion. While most of my points were regarding existing data and theories/models, some were of a policy nature, and I apologize for this.
However, I take issue with your comment in which you say there aren’t relevant or meaningful opposing views among scientists. There are many scientists who express sceptism about current global warming theories. Morever, I refuse to accept consensus as the standard by which I measure whether or not a theory is accurate. Hard data, as you suggest, is the best method. And if it is so clear that their is man-made climate change, my rantings should be easy to refute
Data: I direct your attention to a graph of temperature change trendlines from multiple studies that seems to pop up a lot: http://www.ncdc.noaa.gov/paleo/pubs/briffa2001/plate3.gif . All but one trend line show recent temperature changes that are not drastically different from what the earth has experienced in the last 1000 years, and the one trend line that shows a spike only goes back 150 years.
As I am obviously
not a member of the scientific community, please explain these results.
29 novembre 2005 at 3:59 PM
Re 64
And if it is so clear that their is man-made climate change, my rantings should be easy to refute
So far they have been.
Graphic All but one trend line show recent temperature changes that are not drastically different from what the earth has experienced in the last 1000 years, and the one trend line that shows a spike only goes back 150 years.
Check the various hockey stick and ocean heat posts here. All but one of those lines are reconstructions that stop somewhat short of the most recent warm decade. The one with the spike is the instrumental record. The key is not that the instrumental record isn’t too far outside history, but that there’s no natural forcing to explain its spike.
29 novembre 2005 at 3:59 PM
#59 I just want o be sure that I get this right. You are saying that hundreds of labs around the world with very different techniques are all making an error because they are in one way or another linked to the NOAA standard and so they are all consistently but erroneously measuring a drift of 80ppm. Is this right?
I just told this over lunch to the boss of our CO2 lab, she is still a bit frantic and I am not sure if I understood her answers correctly.
29 novembre 2005 at 4:33 PM
Re 59 (CO2 measurement drift)
So you accept that some of the drift discussion is relevent. Thank you.
Some you say is irrelevent because it relates to particular cylinders, but particular cylinders are what are used in the measuring process.
I only said “most” because I didn’t feel like rereading the article three times to be sure of “all.” While there might be some way to construct an argument for overall drift, it would have to be miniscule. Individual cylinders don’t matter because they get swapped out and recalibrated from time to time. If there was a long-term drift in a cylinder, it would get noticed by differences at swap time or across labs. This would be especially obvious for high drift rates (which had short durations) or inconsistent signs. Even if the year-to-year drift of a particular cylinder were as great as the atmospheric trend, that doesn’t mean the whole measurement system would miss a 30% change over 30 years.
As to corroboration by isotope ratios, it seems also to be an inexact science::
Since the 13C trend is at least 3x the size of the interlab error it again seems implausible that drift could account for the difference.
As to the “good reason to expect”, if one goes into these things prejudging the outcome then it is no surprise that the expected outcome is achieved.
Noting agreement between independent lines of evidence is not the same as prejudging the outcome. I seriously doubt that scientists setting up monitoring at Mauna Loa in 1958 fooled themselves because they were looking for a particular trend. The burden is on you to identify a plausible mechanism for a long-term drift of >30% in multiple instrument types and a plausible way for sink uptake to increase by 6 GtC/yr without any increase in atmospheric concentration.
29 novembre 2005 at 4:52 PM
Re: #66
You’re misreading the graph. Only one of the datsets in the NGDC graph (the observed temperatures) extends until 2000–the others stop around 1980 or earlier. This leads to the illusion that only one record shows an unusual trend. Every dataset in the graph shows higher temperatures in the 20th century than any other time in the record.
29 novembre 2005 at 5:06 PM
Michael, thank you for that powerful #64; I like the way your argument is developing, esp. wrt our work did not emerge in the context of deliberate obfuscation. I’d like to think Shellenberger and Nordhaus have come up with a coherent response to this condition. In addition, I’d explicitly say that responding to deliberate obfuscation/mendacity/FUD spread so far and wide in comment threads is not “debate”.
Best,
D
29 novembre 2005 at 5:11 PM
RE: 66
I’m not sure if the graph you were posting (which needs to be cleaned up by deleting the ). at the end of the link) really shows what you say it would. While writing that “All but one trend line show recent temperature changes that are not drastically different from what the earth has experienced in the last 1000 years” I see a temperature shift from -0.35 to +0.25 degrees Celsius or of 0.7 K since the year ~1920. There is no comparable period showing such a big change in such a short time in any of the graphs - except when you look at the graph of Crowley & Lowery between 1850 and 1950 perhaps. But compared to the obersvation this seems to be on of the most unreliable calculations for that period (or the obersvations would have to be flawed).
And you might have to get a look on this:
http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png
29 novembre 2005 at 5:36 PM
Re #39 (comment),
Eric, the work of Cuffey and Vimeux was used by Jouzel ea. to correct the Vostok reconstructed temperature curve derived from the deuterium data. This only affects the amplitude of the temperature change, not the timing of the start and end of the cooling period, neither does it affect the timing or amplitude of the CO2 lag. The Cuffey and Vimeux correction (btw, data not available at the NOAA Vostok database) gives a somewhat longer high temperature level (which increases the covariance between CO2 and temperature), followed by a faster decrease until the minimum is nearly reached at the moment that the CO2 level starts to decrease. Thus there is simply no measurable influence of 40-50 ppmv CO2 on the temperature drop, even with a corrected temperature curve.
To make it clear, here the time periods for the different changes:
Temperatures in K, uncorrected (between brackets for corrected temperature data, as far as can be deduced from the coarse graph in Jouzel ea.), compared to current temperature and BP (before present):
128,000-118,000: +2 -> -1.5 (+2 -> 0)
118,000-112,000: -1.5 -> -6 (0 -> -4)
112,000-108,000: -6 -> -7 (-4 -> -4.5)
108,000-107,000: -7 -> -4 (-4.5 -> -2)
107,000-103,000: -3.5 +/- 0.5 (-2 +/- 0.5)
CO2 levels
128,000-112,000: 270 +/- 10 ppmv
112,000-106,000: 270 -> 230 ppmv
106,000-95,000: 230 +/- 7 ppmv
In addition, the CH4 (methane) levels:
128,000-118,000: 700 -> 560 ppbv
118,000-112,000: 560 -> 460 ppbv
112,000-106,000: 460 +/- 20 ppbv
106,000-105,000: 460 -> 590 ppbv
105,000-102,000: 590 -> 490 ppbv
As you can see, CH4 closely follows the temperature changes, while CO2 lags so much that it can’t have any influence on the temperature drop…
29 novembre 2005 at 5:50 PM
Re #51,
See Hans Erren’s calculations…
29 novembre 2005 at 6:00 PM
Re #66: “There are many scientists who express sceptism about current global warming theories.”
Disagreement about the details? Sure, lots. Disagreement with the consensus (anthropogenic GHGs causing significant global warming) by scientists qualified to make the judgment? Very, very little. “Many (skeptic) scientists?” Palpably false. If you want your other points taken seriously, it’s probably best to not make assertions of that sort.
29 novembre 2005 at 6:35 PM
Re #66; There are simple answers to each of your eight points, but together your eight points do not constitute the basis for a contrary theory. It is to this that the conclusion of #63 referred, and with this that I agreed.
Regarding your eight queries, I would say that (aside from the last question which is rather off topic) you don’t raise any issues that aren’t already in the basic repertoire of geophysics. So while it may be worth taking the time to address them, the result can only be a painstaking effort to convey geophysical understanding in a didactically disorganized way.
Like a toddler playing the “why” game, you can always find more elementary questions to ask. Producing this sort of question is dramatically easier than formulating a correct and compelling answer.
If you are genuinely interested, perhaps we can discuss your background and then we can recommend a course of study. Otherwise, it doesn’t really pay to address these questions one by one and in depth.
I would rather focus on your third paragraph in #66, which betrays, I think, a misundertsanding of the scientific method and of the extraordinary community that enables it to work.
You say: I take issue with your comment in which you say there aren’t relevant or meaningful opposing views among scientists. There are many scientists who express sceptism about current global warming theories.
While the truth of this assertion depends sensitively on the meaning of “many”, you are arguing against a point I did not make. What I said was that among the skeptics, no one has produced a coherent alternative explanation of how things might work such that greenhouse gas accumulations would be a matter of small consequence. That is, as regards anthropogenic climate change, there is a consensus position and there is some number of doubters, but there is no alternative school of thought, no coherent alternative theory.
You say Morever, I refuse to accept consensus as the standard by which I measure whether or not a theory is accurate.
While I’ve heard this sort of thing lately, I find it disturbing and peculiar in the extreme. Any scientist will attest to the value of asking other scientists questions in neighboring disciplines. The probability of a single scientist making an assertion regarding his or her own field with very little qualification that turns out to be unfounded is quite small. The probability that unanimous unqualified agreement among several scientists turns out to be unfounded is vanishing. This is exactly the basis on which science can proceed, because far more is now known than any individual can check. We have confidence in this methodology because some of us do wander from one field to another, and when we do check, we find that assertions that are claimed to be on a sound basis in a rigorous science almost invariably turn out to be true.
Without consensus, we have no science, and so we must proceed blindly on what we can each figure out alone.
In the present case, we have fifteen year old predictions of climate changes that are highly unlikely within natural variability that essentially show every indication of being basically correct. We have a community of scientists that finds this outcome unsurprising, if perhaps disturbing. We have a formal international consensus process that continues to refine the predictions but finds little basis to question it. We have a detailed report issued by that consensus body along with numerous references to the primary literature. We have essentially unanimous agreement from relevant scientific organizations ( e.g., the American Meteorological Society, the American Geophysical Union, the American Association for the Advancement of the Sciences, the National Academy of Sciences).
On the other side, we have a contingent of political organizations and opinionated publications that call this consensus into question. This group is the more politically sophisticated, but it draws on perhaps two dozen arguably qualified scientific professionals, among them having nothing resembling an alternative theory with explanatory or predictive power.
In this situation, arguing from authority must carry some weight. Human progress is built on intellectual and moral trust. Consensus in science is not achieved lightly and shouldn’t be challenged as if it were a mere intellectual fad. Let’s see some alternatives with equal explanatory power before we go throwing out the opinions of established science. At present there are not two equal sides to “the issue”. In a scientific sense, what the public sees as “the issue” has been framed by nonscientists. At present, there really is nothing in science that resembles “the issue” usually framed as “believing in global warming”.
Public discourse is not advanced by what can only be called impertinent questions. If we were in a more civilized phase of society, we would see far less of both credulity and incredulity here, more trust in the scientific community to converge upon truth and give honest evaluations of uncertainty. Then we might get more exploration of the nature of the relevant evidence and its consequences, ideally leading to responsible and informed policy debates and policy decisions.
29 novembre 2005 at 6:51 PM
RE: #75 and all my other friends here
In deference to Mr. Tobis’s comment, perhaps we should take this to another forum, if others are interested. Any suggestions? I have a blog that I am willing to open up for comments without censoring, or perhaps a more neutral forum?
29 novembre 2005 at 7:05 PM
Re 46, 51, 74
Hans Erren’s napkin is hardly an authoritative source. I find it quite bizarre that he can neglect feedback, the atmosphere, and most of the available data, and then write “That’s physics. All the rest is models and hype.” His calculation is physics about as much as tossing a coin is economics. And what is physics anyway, if not testing of models with data?
29 novembre 2005 at 7:19 PM
Re #51 and #57,
I used Hans Erren’s calculations to give a fast response, but now derived it from the on-line Modtran calculation program:
View downward at 70 km, no rain or clouds, water vapour scale at 1 (= no increase) and CO2 levels on 280 and 560 ppmv. By adjusting the ground temperature offset with 560 ppmv, we could increase the outgoing radiation back to the original radiation at 280 ppmv, thus get it all again into dynamic equilibrium. The result:
Tropics: +0.88 K
Mid-latitudes: winter +0.76 K, summer +0.84 K
Sub-arctic: winter +0.63 K, summer +0.71 K
1976 US standard atmosphere: +0.86
(I suppose that the latter is a kind of world average)
If one includes clouds in the US standard atmosphere, the increase in temperature, necessary to reach the equilibrium is lower: +0.62 K for cumulus and +0.81 K for standard cirrus (the latter rather unexpected, as cirrus clouds are thought to increase temperature by reflecting more IR energy back down than they reflect incoming light back to space?).
Thus based on spectral absorption, a doubling of CO2, including clouds, seems to be very near what Hans Erren calculated and lower than what the IPCC proposes. I don’t know what the cause of the difference is.
29 novembre 2005 at 8:02 PM
I am still reading this dense thread. However, initially, let me offer the following casual remarks: Looking at the graph of CO2 cycles over 600 kYears I would tend to draw parallels as some of your contributors have done, like the architect drawing layers with acetate transparencies, to look at alignments with geologic and archeologic milestones which are familiar to me.
Purely from a math perspective I was tempted to assess the acceleration which the width of one dot on the graph represents, understanding that the epica core shows mostly newly discovered older CO2 cyclical data as a way of highlighting the astounding new rise many hundreds of ppm over historical levels over so short a timeframe; which is to say to this novice reader it appears that adding 60 dots above the 0th kYear would yield the current CO2 level in 2005; however, it would appear that the cycles usually take 20 kYears instead of 0.1 kYear, making our curve exceedingly steep in 2005.
It is probable this distinguished assemblage of scientific thinkers already has engaged in a thermodynamic analysis as well: my first concept was to measure the total energy output of all the fossil fuels humans have combusted in the past 0.1 kYears and then compare that total energy release figure to the archeologically known past times when other large energy releases occurred, as for example with volcanic activity, meteor impact in the atmosphere, and other events which revealed similarly large quanta of energy into the atmospheric system.
I will study your data with earnest interest. You have my congratulations and heartfelt appreciation for the arduous effort it has required to arrive at this new look at another 200 kYears of past history from a climatologic perspective.
29 novembre 2005 at 8:09 PM
Re #79: Hans Erren’s calculation does not make any sense to me. He starts with the standard formula for calculating the radiative forcing for a change in carbon dioxide levels:
dE = 5.35 * ln([CO2]/[CO2 orig), in watts per square meter.
Fine, but then to calculate the temperature change this will cause, he substitutes this into the derivative of the Stefan-Boltzmann equation, producing
dT = ( [5.35 * ln([CO2]/[CO2 orig) ) / (4[sigma] T^3), where T is the Earth’s average surface temperature.
The amount of radiative forcing due to carbon dioxide has nothing to do with the Earth’s original temperature, but here it seems to depend on its cube. This is clearly incorrect.
Can someone give me a link to the on-line Modtran calculation program so I can understand what Ferdinand is doing with it?
29 novembre 2005 at 10:26 PM
#77 - I have just set up a talkshop forum at
http://www.lifeform.net/talkshop
It’s wide open, and anyone is welcome, for a lively flame war, or whatever. I’ll be working on hacking a bigger post_form box for it soon, as the one that came with it is quite small. It’s also HTML compatible.
Thomas Lee Elifritz
http://cosmic.lifeform.org
29 novembre 2005 at 10:31 PM
Re #51 and #79: I believe that one thing that Hans Erren’s calculation is neglecting is that the earth is not a blackbody. Rather, its albedo is ~0.3 which means it only absorbs about 70% of incoming radiation. If one corrects for that, the 0.7 C that Hans calculates becomes about 1.0 C.
In reality, it would probably be more accurate to use the absorptivity in the infrared spectrum and I am not sure what that is. I would assume that Houghton’s estimate of 1.2 C comes from some sort of more careful calculation of this sort. It would probably be wise to learn more about it before believing any derivation that gets a different result.
Re #81: Well, as f