Another paper for the Copenhagen train. This is an estimate according to the abstract. Here’s the abstract and the supplemental information, of course the publicly funded paper is behind the AAAS paywall.
From UCLA News: Last time carbon dioxide levels were this high: 15 million years ago, scientists report
By Stuart Wolpert October 08, 2009 Category: Research
You would have to go back at least 15 million years to find carbon dioxide levels on Earth as high as they are today, a UCLA scientist and colleagues report Oct. 8 in the online edition of the journal Science.
“The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland,” said the paper’s lead author, Aradhna Tripati, a UCLA assistant professor in the department of Earth and space sciences and the department of atmospheric and oceanic sciences.
“Carbon dioxide is a potent greenhouse gas, and geological observations that we now have for the last 20 million years lend strong support to the idea that carbon dioxide is an important agent for driving climate change throughout Earth’s history,” she said.
By analyzing the chemistry of bubbles of ancient air trapped in Antarctic ice, scientists have been able to determine the composition of Earth’s atmosphere going back as far as 800,000 years, and they have developed a good understanding of how carbon dioxide levels have varied in the atmosphere since that time. But there has been little agreement before this study on how to reconstruct carbon dioxide levels prior to 800,000 years ago.
Tripati, before joining UCLA’s faculty, was part of a research team at England’s University of Cambridge that developed a new technique to assess carbon dioxide levels in the much more distant past — by studying the ratio of the chemical element boron to calcium in the shells of ancient single-celled marine algae. Tripati has now used this method to determine the amount of carbon dioxide in Earth’s atmosphere as far back as 20 million years ago.
Aradhna Tripati
“We are able, for the first time, to accurately reproduce the ice-core record for the last 800,000 years — the record of atmospheric C02 based on measurements of carbon dioxide in gas bubbles in ice,” Tripati said. “This suggests that the technique we are using is valid.
“We then applied this technique to study the history of carbon dioxide from 800,000 years ago to 20 million years ago,” she said. “We report evidence for a very close coupling between carbon dioxide levels and climate. When there is evidence for the growth of a large ice sheet on Antarctica or on Greenland or the growth of sea ice in the Arctic Ocean, we see evidence for a dramatic change in carbon dioxide levels over the last 20 million years.
“A slightly shocking finding,” Tripati said, “is that the only time in the last 20 million years that we find evidence for carbon dioxide levels similar to the modern level of 387 parts per million was 15 to 20 million years ago, when the planet was dramatically different.”
Levels of carbon dioxide have varied only between 180 and 300 parts per million over the last 800,000 years — until recent decades, said Tripati, who is also a member of UCLA’s Institute of Geophysics and Planetary Physics. It has been known that modern-day levels of carbon dioxide are unprecedented over the last 800,000 years, but the finding that modern levels have not been reached in the last 15 million years is new.
Prior to the Industrial Revolution of the late 19th and early 20th centuries, the carbon dioxide level was about 280 parts per million, Tripati said. That figure had changed very little over the previous 1,000 years. But since the Industrial Revolution, the carbon dioxide level has been rising and is likely to soar unless action is taken to reverse the trend, Tripati said.
“During the Middle Miocene (the time period approximately 14 to 20 million years ago), carbon dioxide levels were sustained at about 400 parts per million, which is about where we are today,” Tripati said. “Globally, temperatures were 5 to 10 degrees Fahrenheit warmer, a huge amount.”
Tripati’s new chemical technique has an average uncertainty rate of only 14 parts per million.
“We can now have confidence in making statements about how carbon dioxide has varied throughout history,” Tripati said.
In the last 20 million years, key features of the climate record include the sudden appearance of ice on Antarctica about 14 million years ago and a rise in sea level of approximately 75 to 120 feet.
“We have shown that this dramatic rise in sea level is associated with an increase in carbon dioxide levels of about 100 parts per million, a huge change,” Tripati said. “This record is the first evidence that carbon dioxide may be linked with environmental changes, such as changes in the terrestrial ecosystem, distribution of ice, sea level and monsoon intensity.”
Today, the Arctic Ocean is covered with frozen ice all year long, an ice cap that has been there for about 14 million years.
“Prior to that, there was no permanent sea ice cap in the Arctic,” Tripati said.
Some projections show carbon dioxide levels rising as high as 600 or even 900 parts per million in the next century if no action is taken to reduce carbon dioxide, Tripati said. Such levels may have been reached on Earth 50 million years ago or earlier, said Tripati, who is working to push her data back much farther than 20 million years and to study the last 20 million years in detail.
More than 50 million years ago, there were no ice sheets on Earth, and there were expanded deserts in the subtropics, Tripati noted. The planet was radically different.
Co-authors on the Science paper are Christopher Roberts, a Ph.D. student in the department of Earth sciences at the University of Cambridge, and Robert Eagle, a postdoctoral scholar in the division of geological and planetary sciences at the California Institute of Technology.
The research was funded by UCLA’s Division of Physical Sciences and the United Kingdom’s National Environmental Research Council.
Tripati’s research focuses on the development and application of chemical tools to study climate change throughout history. She studies the evolution of climate and seawater chemistry through time.
“I’m interested in understanding how the carbon cycle and climate have been coupled, and why they have been coupled, over a range of time-scales, from hundreds of years to tens of millions of years,” Tripati said.
In addition to being published on the Science Express website, the paper will be published in the print edition of Science at a later date.
UPDATE: Bill Illis add this graph in comments, which brings up the obvious correlation questions.
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Vincent says:
And you are quoting the part of my post where I did not talk about direct empirical evidence, leaving out the part where I did, and then complaining about my not providing empirical evidence.
~snip~
alphajuno (11:39:35)
in short, they are correct results, as the process is a scientifically valid one. Beck only reconstructs using raw high density of raw data with broad geographic coverage. The process carries on today and chemical measurements produce similar measurements to the IR spectroscopic technique. With the IR technique the uncertainty is mapping where c02 bands cross with water vapour bands, which generally separate out at higher altitudes in the troposphere. from 1810-present, these results are in broad agreement of c02 concentrations. When ice core measurements are substituted instead, then a proxy is taken as ice cores at Vostok don’t give an exact replication of aerial co2 from its proxy. Due to various chemical processes, and the fact that c02 can deplete in compressed ice by a diffusion effect at pressure at the compressed area, which is 300 times that of normal atmospheric temperature. This, and other physical processes smooths out c02 variations to a fairly uniform level and minimises both peaks and troughs in the c02 legend. Furthermore – it is only at vostok. Other ice cores eg Greenland, show a greater amplitude of temperature variaton than vostok.
Its still useful for taking this as a barometer of past climate in one location, but not an accurate average of past antarctic c02.
Joel Shore,
“And you are quoting the part of my post where I did not talk about direct empirical evidence, leaving out the part where I did, and then complaining about my not providing empirical evidence.”
No, I am not complaining about you not providing empirical evidence. I am taking issue with your implication that because climate models fail to show negative water vapour feedbacks, that this somehow shows that such negative feedbacks do not exist in nature. If I am inferring incorrectly, then I don’t understand the point of your statement.
“Joel Shore
I.e., it could be that as you draw down CO2, H2O is drawn down enough that most of the greenhouse effect disappears…”
Again, you miss the consequences of a log response as opposed to a linear response. When you look at an h2o fraction and combined with temperature see a relative humidity, it doesn’t matter what that humidity is for radiative transfer. What matters is the density of the material and the fact that you are dealing with a log function where as the relative humidity is much more linear. Doubling or halving the amount of water vapor doesn’t double or halve the effect, it provides merely a small increment in the total h2o effect. Changing the total amount of ghg effect only shifts the point where things occur by a small amount.
When you consider even the current or recent history nominal conditions, you find that there isn’t a radiative only balance present. Convection (and the water vapor cycle) accounts for a substantial fraction of energy transfer near the surface.
Drawing down CO2 is not going to affect h2o concentrations, which depend upon the local availability of h2o (or transported h2o) and the temperature / incoming power necessary to generate it + a bit more. Essentially, whatever miniscule drop or rise in temperature caused by the CO2 change would then be reflected in relative humidity which is PRESUMED to remain unchanged. As stated above, it’s the absolute humidity or atmospheric concentrations that affect absorption.
I do not have a reference to offer as it’s unpublished concerning halvings. I think if you go to a modtran calculator online that you could get a reasonable facsimile of the result by going through a series of halvings and noting the difference between each at an altitude, like 45km. As long as the increment or decrement of transmitted power ranges between around 2.x and 3.x W/m^2, you’re still in the log region.
“…and, of course, the albedo effects change too. Clouds change but, probably more importantly, there is a lot more ice and hence significantly more reflection of solar radiation. This means that, in fact, a planet with all the CO2 removed and most of the water vapor locked out of the atmosphere could be considerably more than 33 C colder because it could be essentially a “snowball earth” scenario with a large albedo. (I am not sure how large the albedo could realistically get.)
”
The 33 degrees C ghg contribution assumes a 0.30 albedo average with today’s average global temperature versus a blackbody with 0.30 albedo. Venus is thought to have a 0.65 to 0.70 albedo with clouds that are perfectly opaque and not composed of h2o vapor. Snowball Earth is quite a different scenario than today – or even a typical ice age glaciation period. Fresh snow is quite high in albedo, rivaling that of Venus but clear ice is practically no better than ocean water which comes in at 0.035 or so. It matters little today as it’s all at the poles which receive light only part of the year and at a very high angle of incidence (relative to the Normal). Of course at these angles, even the ocean water starts to do a good job of reflection for whatever light is making it in. Glaciation means much lower lattitude coverage and so much lower net incoming power after albedo kicks it out. Snowball Earth is even worse than this. Glaciation periods are a shortcircuit to cloud feedback as in interglacial time periods, clouds account for about 80% of the total albedo, around 0.22 out of the nominal 0.30. Oceans cover around 70% and are extremely low in albedo, under 0.04 for low angles of incidence relative to the normal. The land surface is going to be averaging between 0.10 and 0.20, including all that ice and snow.
As for a maximum realistic albedo, rest assured it could get as high as Venus which is over 0.6 and perhaps over 0.7.
One of the problems with this is albedo measurement has not been done consistently for any significant length of time. It has been assumed constant yet measured to have changed substantially, enough to cause many W/m^2 more than all the CO2 ghg change currently attributed to man and perhaps as much as 10% over 20 years. Using this and the corresponding temperature change, one finds there to be less of a change than a simple radiative calculation would suggest – which means there is net negative feedback present.
Trying to compare a glacial maximum to cloud albedo is to acknowledge the importance of albedo and hence the effect of cloud cover. As stated, if you’ve got fresh snow below, cloud albedo has been shortcircuited as it doesn’t matter if there is a cloud present or not as there will be significant amounts of power reflected.
Part of the problem with understanding cloud cover and the variations involved is that where there is the most incoming energy, one has the daily water vapor cycle in operation where clouds build up, transfer heat, and dissipate in the evenings. This is not something that works with simple static type models and it is something that cannot happen with Venus – even if it did have lots of water and much less atmosphere. For clouds to have serious IR blocking effects greater than their albedo contributions, you’ve got to have night time presence when there is no incoming solar to reflect away. While there are some night time clouds, the average conditions are to provide a net negative feedback. Also, one must realize that clouds have solid or liquid h2o in them which can do continuum radiation, although at a much lower rate than the average surface due to lower temperatures.
Stefan’s law is empirical but it turns out to be the integration over wavelength (or frequency) and angle of the Planck blackbody radiation curve. The engineering fudge factor is totally incorrect (epsilon) as reflectivity is a function of wavelength. What appears to be shiney and highly reflective in the visible may be like a lump of coal in a dark room when it comes to another area of the spectrum.
From what I’ve seen over the years, the cagw groupies and even scientists are suffering from a mental defect of the human condition. The best example I know is from the earlier evolution proponents who became ‘true believers’ to the point that their understanding and dogma was that Earth had to be stable and unchanging for eons and that catastrophic events could not have happened. I don’t have a dog in that hunt but I suspect that there’s more likely a panspermia factor going on from the cold depths of space far from the influence of stars as compared to the usual biology dogma that still exists. Their denial of castastrophic activities to promote their slow cooker primordial stew project was clearly wrong yet it negatively impacted even other disciplines for quite some time. It took many decades of serious evidence and research elsewhere to overcome that unwarranted bias. The history of science is full of much lesser dogmatic problems and cagw isn’t one of the lesser.
Dennis (11:41:46) :
. . . I am struck by the upper bound of average global (I know, E.D.) temperatures that with 2 exceptions doesn’t seem able to break about a 22 degree C. boundary over the past 600 million(!) years, and that today is about half of that bound. I don’t know how this graph was derived but, if valid, would indicate that there is some very powerful feedback mechanism that doesn’t allow temps to go hog wild beyond a certain point. . . .
It would have to be a feedback that could keep the temperature stable for millions of years. Notice there’s something of a bottom limit to temperature too around 12C, about where we are now. Could be we’re just not close enough to the sun to get any hotter or far enough away to get any colder (given we’re a water planet).
Great post: cba (08:44:26) :
Since the theme of this thread is the following great quote from Bill Illis, I am posting again to see how long Joel Shore avoids it.
Trouble is, he does not have a good answer for it, so that is his method, avoid. Nevertheless it is being posted again here as it needs to be said over and over because it is the irrefutable truth.
Bill Illis (06:04:54) :
The important aspect about using the paleoclimate data is that there is no “lagged warming” explanation available for the Hansen’s of the world.
The lags in the climate system can only be as long as 1,500 to 3,000 years as a maximum.
The paleo data extends beyond those lags so when you see CO2 staying at 250 ppm for 10 million years, then one can be sure that other things are impacting the climate beyond CO2/GHGs and these other factors must, in fact, be far more important.
If CO2/GHGs were as dominant as the theory says, then the last 20 million years should have been one big long ice age. Maybe not as big as the last glacial maximum but the glaciers should have extended into the mainland of North America for the entire period. Well, they didn’t and, in fact, it was much warmer than today in the period.
I’m assuming the COGNITIVE DISSONANCE of actually looking at the data and seeing that it does not match up with the theory, means they just don’t look at it anymore (or believe it). Which means they are constantly trying to find ways to adjust it. This is another one of those.
This needs to be shouted from the housetops….
Chris
Norfolk, VA, USA
And this quote from Dave Middleton. So many good ones to choose from here…but they bear repeating:
“If fossil plant stomata-derived paleo-CO2 values are quantitatively correct – A century-scale rise from 280ppmv to 380ppmv CO2 is wholly unremarkable and has been the norm in every warming period since the early Holocene; including the MWP, Roman Warming and Holocene Thermal Maximum.”<cite
“So… Either CO2 didn’t cause the late 20th century warming; or the late 20th century rise in atmospheric CO2 levels was mostly caused by the late 20th century warming.”
“The fact that delta-CO2 lagged behind delta-T in the Pleistocene ice cores and that fossil plant stomata data suggest that Holocene CO2 levels have always risen to the mid to high 300’s ppmv… Coupled with the total non-correlation of temperature and CO2 throughout most of the Phanerozoic tells this geoscientist that the IPCC are barking up the wrong tree.”
Well said….
With that, this poster is off for a run in some forested “hills” (trans. former ocean boundary 5 to 8K year old sand dunes from the Holocene Climatactic Optimum) on the otherwise flat coastal plain of Virginia where I live.
Wonder what caused that sea level rise back then? Must have been space aliens injecting huge amounts of CO2 into the atmosphere.
Chris
Norfolk, VA, USA
Joel Shore (14:39:25) :
It is not primarily the CO2 levels that matter as the rapidity of the rise. CaCO3 from limestone rocks acts to neutralize the oceans but it is a slow process relative to the rate at which we are increasing CO2 in the oceans. There is one possible past analog to the current situation, which is the PETM event that occurred about 55 million years ago when there was a large release of greenhouse gases and significant warming.
As further evidence that the pro-AGW researchers just do not want to look at the PaleoClimate data, why do they spend so much time talking about the Paleocene Eocene Thermal Maximum.
This was a rather ordinary event in the history of the climate. Just 40 millions years earlier in the Cretaceous (when CO2 was a little lower in fact), temperatures were 2C to 3C higher than the PETM. Dinosaurs lived in Alaska and it was a little farther north than it is now. Sea level was so high that North America was flooded from Texas to Inuvik to Hudson Bay as well as all of Europe and North Africa.
It is just rather odd that a small ordinary peak like the PETM can have so much attention and all the other major events are never mentioned.
Where do you start with something likes this? Warm sea = high co2!!!!!!
If was warm than c02 was high! Its that simple. Stop confusing cause and effect!
Who burnt all the fossil fuels 15 millions years ago?
Plus comparing a observatory near the equator on a active volcanoe to somewhere where co2 is absorbed due to temperature (antarctic) is stupid. They are not the same and nor are co2 concentrations at both locations. Secondly, the algae is a proxy for disolved co2 in the ocean is it not, not the atmosphere? Because it compares to antarctica doesnt mean its right either!
Sheesh!
The Sun and CO2 share a common bond. Neither agrees well with climate reconstructed over millions of years. In fact, if AGW’ers persist in demonstrating a correlation with reconstructed CO2 and reconstructed climate, I would use the Sun’s correlation to show just how weak their connection is. If it’s good for the goose, it’s good for the gander. They would have to admit that CO2 is as good as the Sun in bringing about climate change when using reconstructed climate and CO2 or Sun correlation.
getting away from all the other problems of joel shore’s post, it looks like the underestimated importance of the impact and variability of cloud albedo combined with the internal variability of the various oscillations, like PDO provides the basis for the total foul-up with the CAGW/IPCC crowd. When one looks at their uncertainty chart, they’ve got cloud variability at about 10% in the albedo for some of the measured values which have been done. The fact that there are no measured values for albedo throughout most of history combined with its significant variability basically negates most of the estimates for sensitivity as well.
cba says:
What you stated is apparently wrong. Here is what the IPCC says about the 3.7 W/m^2 number ( http://www.ipcc.ch/ipccreports/ar4-wg1.htm , Chapter 2, p. 140):
I’ll try to comment on some of the rest of what you wrote later.
guess who was responsible for that chapter. no bias there. What’s more ramaswamy 2001 is the 3rd assessement report.
Ramaswamy, V., et al., 2001: Radiative forcing of climate change. In:
Climate Change 2001: The Scientifi c Basis. Contribution of Working
Group I to the Third Assessment Report of the Intergovernmental Panel
on Climate Change [Houghton, J.T., et al. (eds.)]. Cambridge University
Press, Cambridge, United Kingdom and New York, NY, USA, pp. 349–
416.
“IPCC (1990) and the SAR used a radiative forcing of 4.37 Wm−2
for a doubling of CO2 calculated with a simplified expression.
Since then several studies, including some using GCMs (Mitchell
and Johns, 1997; Ramaswamy and Chen, 1997b; Hansen et al.,
1998), have calculated a lower radiative forcing due to CO2
(Pinnock et al., 1995; Roehl et al., 1995; Myhre and Stordal,
1997; Myhre et al., 1998b; Jain et al., 2000). The newer estimates
of radiative forcing due to a doubling of CO2 are between 3.5 and
4.1 Wm−2 with the relevant species and various overlaps between
greenhouse gases included. The lower forcing in the cited newer
356 Radiative Forcing of Climate Change
studies is due to an accounting of the stratospheric temperature
adjustment which was not properly taken into account in the
simplified expression used in IPCC (1990) and the SAR (Myhre
et al., 1998b). In Myhre et al. (1998b) and Jain et al. (2000), the
short-wave forcing due to CO2 is also included, an effect not
taken into account in the SAR. The short-wave effect results in a
negative forcing contribution for the surface-troposphere system
owing to the extra absorption due to CO2 in the stratosphere;
however, this effect is relatively small compared to the total
radiative forcing (< 5%).
The new best estimate based on the published results for the
radiative forcing due to a doubling of CO2 is 3.7 Wm−2, which is
a reduction of 15% compared to the SAR…."
Sorry, but going over the description of the original 2001 paper doesn't seem to back up the later claim that it is a value that includes non clear sky effects. Note that IPCC doesn't appear to actually do peer review and it's under the overview of guess who again. In any case, the references to other papers takes you back into the 90s and gcms – which do still not properly handle clouds. They do state that they handle stratospheric temperatures and atmospheric concentrations but that doesn't relate to clear sky results versus cloudy or mixed. Again, you can ascertain the results for yourself using a modtran calculator – or you can spend a few months developing a line by line radiative transfer model using something like HITRAN for a one dimensional radiative model also using a model atmosphere such as the 1976 US Standard Atmosphere like I did. The results will be far more accurate than can be achieved in a GCM if reasonably well done as those become extremely time bound on supercomputers using relatively crude radiative calculations.
You'll note from the provided quote that their admitted error from their previous effort was too high by 15%.
I think if you dig enough that you will find the 3.7 W/m^2 is based upon clear skies and depends upon the altitude that you make your comparisons at. Cloudy skies are not used as clouds tend to be well above most of the CO2 effects, they tend to create their their own emission continuum with lower power radiated due to lower temperatures than the surface, and once above the lower arena of the atmosphere, the line broadening drops substantially, reducing the actual effects to very small bandwidths that actually absorb much less power.
Bill Illis says:
Well, for what it is worth, the chart on this website suggests the PETM was warmer: http://www.scotese.com/climate.htm Don’t know how accurate it is or where it or your info are from. However, I think the more important reason to look at the PETM was the rapidity of the warming event and the major release of carbon, which I believe make it the closest analog that we of for our current little experiment.
stumpy says:
Carbon dioxide is quite well-mixed in the atmosphere. Although the first measurements were made at Mauna Lao, it is now measured in several different places around the world ( http://cdiac.ornl.gov/trends/co2/sio-keel.html ) and, while there are small differences and different seasonal variations in the different places, they are quite small. We also now have a satellite mapping of CO2 concentrations in the mid-troposphere: http://geology.com/nasa/carbon-dioxide-map/ Note that the measured CO2 level (from July 2008) is ~381 +/- 5 ppm where the +/- seems to be essentially the entire range of variation on that map (the standard deviation is probably only a couple of ppm).
Joel Shore (19:08:07),
Pick the human induced CO2 forcing out of this. Be creative, you always are.
Folks, the climate is behaving naturally, as it always does. Human emissions may have a very *slight* effect. But for all practical purposes, they can be completely disregarded as inconsequential.
Bill Illis says:
Smokey says:
savethesharks says:
Bill,
The data that you show seems to be quite at odds with the recent paper of Kurschner et al. (2008) http://www.pnas.org/content/105/2/449.full , which in fact shows quite a tight linkage between CO2 and temperature during the time period of the Miocene that they look at (between 11 and 25 million years ago), with part of that period having CO2 levels of 400ppm or higher: http://www.pnas.org/content/105/2/449/F3.large.jpg (The general features for CO2 in this paper seem to agree with this new paper by Tripati et al. although the drop in CO2 seems to start a little earlier in the record in that paper than what Tripati et al. find.)
Of interest is also the paper in that issue by Royer further discussing these results and putting them into context: http://www.pnas.org/content/105/2/407.full
Smokey says:
It is good to see you still at your “skeptical” best, Smokey, picking random plots off of the web without bothering to ask if they are correct or incorporate the latest data! Yup, you certainly don’t call yourself a “skeptic” for nothing!
See a peer-reviewed paper that talks about your graph here: http://magee.vsb.bc.ca/dsheldan/climate/pdf/Laut_2003.pdf , especially Figs. 3 and 4.
Anthony
Here is the CO2 data from NOAA
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/paleocean/by_contributor/pearson2000
Joel Shore (20:16:00), I’ve posted hundreds of graphs from multiple sources here. You always find fault with them. Always, every one.
Cognitive dissonance.
Joel your worst problem is that you use sophistry to create a smokescreen and AVOID answering questions.
You could answer Bill’s post directly, as opposed to evading it by referring to another paper.
That really is a side issue.
What are you trying to prove, Joel?
That the AGW cause MUST be proved by science???
Seems rather DEDUCTIVE and conflicting with the Scientific Method.
I wish you well, the burden of proof is on you and your like-minded associates.
You still have not (and i think can not) show forth the evidence.
And I am not talking a logical fallacy through force of words.
I mean, simple, logical explanations.
Chris
Norfolk, VA, USA
http://infomotions.com/etexts/gutenberg/dirs/etext04/hdbrs10.htm
that was a poem learned in school. from line 55 reads the application of the nature of modern science
There is something about the Hudibras in your approach, Joel. Not a criticism. Just an observation
I think we can safely say that if CO2 does drive temperature, its impact is insignificant and non-threatening. The sensitivity of “average” global temperature to a doubling of CO2 is less than 0.5C, and probably less than 0.3C.
But we know so little about atmospheric CO2 (“atm.CO2”).
We think that atm.CO2 lags temperature by ~800 years in the Vostok ice cores, on a cycle of ~100,000 years. But diffusion of CO2 in ice and actual values may be unknowns, even if “trends” are known.
We think that atm.CO2 also lags temperature by ~9 months in a cycle of 3-5 years, but there is the uncertainty caused by huge industrial inputs of CO2.
But when we examine the AIRS satellite data on atm.CO2, the major sources appear to be distant from industry.
http://svs.gsfc.nasa.gov/vis/a000000/a003500/a003562/carbonDioxideSequence2002_2008_at15fps.mp4
It seems like the more we know about atm.CO2, the less we know.
Joel Shore
I’m interested to see that you apparently now embrace the use of stomatal indices for estimating CO2. Does this extend to more recent times when stomatal indices invariably indicate much more variable and usually higher amounts of CO2 in the atmosphere than ice-core data?
If you’re willing to accept Kurschner et al. (2008), then you’d also have to be willing to accept Wagner et al. (1999) – Kürschner was one of the “et al”…
Wagner et al. found that atmospheric CO2 levels were in the 350ppmv to 360ppmv approximately 9,500 years BP. Ice cores show CO2 levels to have been ~280ppmv at that time.
There’s also Kouwenberg et al (2005) – Once again co-authored by Kürschner… They found that CO2 levels have routinely oscillated from 260–275 ppmv to 300–320 ppmv over the last 1,000 years.
Plant stomatal densities can be empirically tested and shown to correlate with atmospheric CO2 levels. Wagner et al. (2005) found that plant SI data matched the instrumental CO2 rise from 310-370ppmv over a 60-year period in the 20th century.
So when do you choose to throw out the plant SI data and rely on ice cores? The SI data do show a better correlation between CO2 and temperature; but they also show that today’s CO2 levels are wholly unremarkable… And they also show that CO2 levels can easily rise and fall by more than 60ppmv per century as the Earth has warmed and cooled through natural climate cycles.
Do we only toss out the SI data when it creates an inconvenient situation wherein modern CO2 levels are only slightly, if at all, elevated when compared with prior Quaternary and Holocene warm periods?
Shaviv’s and Veizer’s reply to Royer (2004) was equally interesting. Royer’s pH correction for sigma-18O was a product of bootstrapping… The pH correction for temperature was essentially derived from RCO2… So it’s no surprise that Royer’s “corrected” Phanerozoic temperatures yielded a better match to CO2. Royer’s pH corrections to temperature also resulted in anomalously warm ocean temperatures during know glacial episodes.
Smokey says:
What can I say? That is because you specialize in going to websites that are created to deceive people and grabbing plots from there and then you accept them uncritically, without the slightest bit of skepticism. It ain’t my fault that you choose to do this.