What Do We Think About Climate Change

[Guillermo]

Which is the best man to deal with –he who knows nothing about a subject, and, what is extremely rare, knows that he knows nothing, or he who really knows something about it, but thinks that he knows all?

—Thoreau, Walking

[Guillermo]

Atmospheric Carbon Dioxide Concentration Across the Mid-Pleistocene Transition
Bärbel Hönisch,1 N. Gary Hemming,1,2 David Archer,3 Mark Siddall,4 Jerry F. McManus1
Science 19 June 2009: Vol. 324. no. 5934, pp. 1551 - 1554
DOI: 10.1126/science.1171477


"The dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for as yet unknown reasons. Here we present a 2.1-million-year record of sea surface partial pressure of CO2 (PCO2), based on boron isotopes in planktic foraminifer shells, which suggests that the atmospheric partial pressure of CO2 (pCO2) was relatively stable before the mid-Pleistocene climate transition. Glacial PCO2 was ~31 microatmospheres higher before the transition (more than 1 million years ago), but interglacial PCO2 was similar to that of late Pleistocene interglacial cycles (<450,000 years ago). These estimates are consistent with a close linkage between atmospheric CO2 concentration and global climate, but the lack of a gradual decrease in interglacial PCO2 does not support the suggestion that a long-term drawdown of atmospheric CO2 was the main cause of the climate transition."

http://www.sciencemag.org/cgi/conten.../324/5934/1551

From the text:
"We therefore conclude that CO2 was unlikely to have been the main driver of the Mid Pleistocene Transition."

[Guillermo]

Stable Carbon Cycle–Climate Relationship During the Late Pleistocene
Urs Siegenthaler, Thomas F. Stocker, Eric Monnin,1 Dieter Lüthi, Jakob Schwander, Bernhard Stauffer, Dominique Raynaud, Jean-Marc Barnola, Hubertus Fischer, Valérie Masson-Delmotte, Jean Jouzel
Science 25 November 2005: Vol. 310. no. 5752, pp. 1313 - 1317
DOI: 10.1126/science.1120130

"A record of atmospheric carbon dioxide (CO2) concentrations measured on the EPICA (European Project for Ice Coring in Antarctica) Dome Concordia ice core extends the Vostok CO2 record back to 650,000 years before the present (yr B.P.). Before 430,000 yr B.P., partial pressure of atmospheric CO2 lies within the range of 260 and 180 parts per million by volume. This range is almost 30% smaller than that of the last four glacial cycles; however, the apparent sensitivity between deuterium and CO2 remains stable throughout the six glacial cycles, suggesting that the relationship between CO2 and Antarctic climate remained rather constant over this interval."

http://www.sciencemag.org/cgi/conten...;310/5752/1313

From the text:

"The lags of CO2 with respect to the Antarctic temperature over glacial terminations V to VII are 800, 1600, and 2800 years, respectively, which are consistent with earlier observations during the last four glacial cycles."

[Guillermo]

Transient simulations of Holocene atmospheric carbon dioxide and terrestrial carbon since the Last Glacial Maximum
Fortunat Joos, Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
Stefan Gerber, Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
I. C. Prentice, Department of Earth Sciences, University of Bristol, Bristol, UK
Bette L. Otto-Bliesner, National Center for Atmospheric Research, Boulder, Colorado, USA
Paul J. Valdes, School of Geographical Sciences, University of Bristol, Bristol, UK

GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 18, GB2002, 18 PP., 2004
doi:10.1029/2003GB002156
Received 24 September 2003; accepted 18 February 2004; published 3 April 2004.

Conflicting hypotheses are investigated for the observed atmospheric CO2 increase of 20 ppm between 8 ka BP and pre-industrial time. The carbon component of the Bern Carbon Cycle Climate (Bern CC) model, which couples the Lund-Potsdam-Jena Dynamic Global Vegetation Model to an atmosphere-ocean-sediment component, is driven by climate fields from time-slice simulations of the past 21 ka with the Hadley Centre Unified Model or the NCAR Climate System Model. The entire Holocene ice core record of CO2 is matched within a few ppm for the standard model setup, and results are broadly consistent with proxy data of atmospheric 13CO2, mean ocean δ13C, and pollen data, within their uncertainties. Our analysis suggests that a range of mechanisms, including calcite compensation in response to earlier terrestrial uptake, terrestrial carbon uptake and release, SST changes, and coral reef buildup, contributed to the 20 ppm rise. The deep sea δ13C record constrains the contribution of the calcite compensation mechanism to 4–10 ppm. Terrestrial carbon inventory changes related to climate and CO2 forcing, the greening of the Sahara, peat buildup, and land use have probably influenced atmospheric CO2 by a few ppm only. The early Holocene CO2 decrease is quantitatively explained by terrestrial uptake and calcite compensation in response to terrestrial uptake during the glacial-interglacial transition. The recent hypothesis by Ruddiman [2003] that anthropogenic land use caused a 40 ppm CO2 anomaly over the past 8 ka, preventing the climate system from entering a new glacial, would imply an anthropogenic emission of 700 GtC and a decrease in atmospheric δ13C of 0.6 permil. This is not compatible with the ice core δ13C record and would require an upward revision of land use emission estimates by a factor of 3 to 4.

[Guillermo]

Ice Core Records of Atmospheric CO2 Around the Last Three Glacial Terminations
Hubertus Fischer, Martin Wahlen, Jesse Smith, Derek Mastroianni, Bruce Deck
Scripps Institution of Oceanography, Geosciences Research Division, University of California San Diego, La Jolla, CA 92093-0220, USA.
Science 12 March 1999: Vol. 283. no. 5408, pp. 1712 - 1714
DOI: 10.1126/science.283.5408.1712

"Air trapped in bubbles in polar ice cores constitutes an archive for the reconstruction of the global carbon cycle and the relation between greenhouse gases and climate in the past. High-resolution records from Antarctic ice cores show that carbon dioxide concentrations increased by 80 to 100 parts per million by volume 600 ± 400 years after the warming of the last three deglaciations. Despite strongly decreasing temperatures, high carbon dioxide concentrations can be sustained for thousands of years during glaciations; the size of this phase lag is probably connected to the duration of the preceding warm period, which controls the change in land ice coverage and the buildup of the terrestrial biosphere."

(bolded is mine)

[Guillermo]

Following last series of deglaciations, atmospheric CO2 concentrations exhibit no net change for thousands of years, during which period air temperatures drop all the way back to values characteristic of glacial times for the next glaciation. Then, when CO2 finally began to decline, air temperatures remain constant for a few thousand years, after which they actually rose for some other thousands of years. And even when the two parameters increase in unison, as they did during the three most recent glacial terminations, temperature always rose first, followed by CO2 concentrations some 400 to 1,000 years later.

[Guillermo]

Now let's switch to other matters than the clear CO2 lagging of temperature.
Now we'll concentrate on the limited CO2 greenhouse effect and how feedback with water vapour is needed by the AGW proponents to explain the observed late temerature increase. This has been much discussed already in this thread, but there's always new information coming. This one is pretty interesting:

Trends in middle- and upper-level tropospheric humidity from NCEP reanalysis data
Garth Paltridge & Albert Arking & Michael Pook
Theoretical and Applied Climatology
DOI 10.1007/s00704-009-0117-x
Received: 21 July 2008 / Accepted: 4 February 2009

http://www.gerkynet.com/meteo/paltrigde08.pdf

Abstract

"The National Centers for Environmental Prediction (NCEP) reanalysis data on tropospheric humidity are examined for the period 1973 to 2007. It is accepted that radiosonde-derived humidity data must be treated with great caution, particularly at altitudes above the 500 hPa pressure level. With that caveat, the face-value 35-year trend in zonal-average annual-average specific humidity q is significantly negative at all altitudes above 850 hPa (roughly the top of the convective boundary layer) in the tropics and southern midlatitudes and at altitudes above 600 hPa in the northern midlatitudes. It is significantly positive below 850 hPa in all three zones, as might be expected in a mixed layer with rising temperatures over a moist surface. The results are qualitatively consistent with trends in NCEP atmospheric temperatures (which must also be treated with great caution) that show an increase in the stability of the convective boundary layer as the global temperature has risen over the period. The upper-level negative trends in q are inconsistent with climate-model calculations and are largely (but not completely) inconsistent with satellite data. Water vapor feedback in climate models is positive mainly because of their roughly constant relative humidity (i.e., increasing q) in the mid-to-upper troposphere as the planet warms. Negative trends in q as found in the NCEP data would imply that long-term water vapor feedback is negative—that it would reduce rather than amplify the response of the climate system to external forcing such as that from increasing atmospheric CO2. In this context, it is important to establish what (if any) aspects of the observed trends survive detailed examination of the impact of past changes of radiosonde instrumentation and protocol within the various international networks."


(bolded is mine)

[Guillermo]

Excuse me, this should have been posted before the last post. It's about the commented "ice cores permeability" to CO2 . Error because of this effect is no bigger than +/-100 years.

Timing of Atmospheric CO2 and Antarctic Temperature Changes Across Termination III
Nicolas Caillon, Jeffrey P. Severinghaus, Jean Jouzel, Jean-Marc Barnola, Jiancheng Kang, Volodya Y. Lipenkov
Science magazine. Submitted 25 September 2002; accepted 10 February 2003

http://icebubbles.ucsd.edu/Publicati...lonTermIII.pdf

Abstract:
"The analysis of air bubbles from ice cores has yielded a precise record of atmospheric greenhouse gas concentrations, but the timing of changes in these gases with respect to temperature is not accurately known because of uncertainty in the gas age–ice age difference. We have measured the isotopic composition of argon in air bubbles in the Vostok core during Termination III (+/-240,000 years before the present). This record most likely reflects the temperature and accumulation change, although the mechanism remains unclear. The sequence of events during Termination III suggests that the CO2 increase lagged Antarctic deglacial warming by 800 +/- 200 years and preceded the Northern Hemisphere deglaciation."

From the text:
"The best correlation (R2 = 0.88) was obtained when we shifted the CO2 profile by 800 +/- 100 years. Combining this uncertainty with the uncertainty introduced by ice accumulation (800 x 0.2, i.e., 160 years),we obtain an overall uncertainty of +/-200 years,indicating that the increase in CO2 lags Antarctic warming by 800 +/- 200 years, which we must consider a mean phase lag because of the method we used to make the correlation."

[Boston]

I like how none of these address the fact of rising temps in conjunction with the artificial alterations of the atmospheric chemistry caused by the burning of fossil fuels.

you are attempting to argue a natural process where there is none, what we have is a man made alteration that is causing reactions across the climate system in a way that is unprecedented in the natural climate history. Regardless of what happened in the past what is happening now and what is causing it, is clear.

I understand that you are having trouble grasping the concept of permeability and that you are unwilling to hear an explanation so maybe this article will help you out a bit.

Titre du document / Document title
CO2 diffusion in polar ice : observations from naturally formed CO2 spikes in the Siple Dome (Antarctica) ice core
Auteur(s) / Author(s)
AHN Jinho (1 2) ; HEADLY Melissa (1) ; WAHLEN Martin (1) ; BROOK Edward J. (2) ; MAYEWSKI Paul A. (3) ; TAYLOR Kendrick C. (4) ;
Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)
(1) Scripps Institution of Oceanography, University of California-San Diego, La Jolla, California 92093-0225, ETATS-UNIS
(2) Department of Geosciences, Oregon State University, Corvallis, Oregon 97331-5506, ETATS-UNIS
(3) Climate Change Institute, University of Maine, 303 Bryand Global Sciences Center, Orono, Maine 04469-5790, ETATS-UNIS
(4) Desert Research Institute, University of Nevada, 2215 Raggio Parkway, Reno, Nevada 89512-1095, ETATS-UNIS
Résumé / Abstract
One common assumption in interpreting ice-core CO2 records is that diffusion in the ice does not affect the concentration profile. However, this assumption remains untested because the extremely small CO2 diffusion coefficient in ice has not been accurately determined in the laboratory. In this study we take advantage of high levels of CO2 associated with refrozen layers in an ice core from Siple Dome, Antarctica, to study CO2 diffusion rates. We use noble gases (Xe/Ar and Kr/Ar), electrical conductivity and Ca2+ ion concentrations to show that substantial CO2 diffusion may occur in ice on timescales of thousands of years. We estimate the permeation coefficient for CO2 in ice is ∼4 x 10-21 mol m-1 s-1 Pa-1 at -23°C in the top 287m (corresponding to 2.74 kyr). Smoothing of the CO2 record by diffusion at this depth/age is one or two orders of magnitude smaller than the smoothing in the firn. However, simulations for depths of ∼930-950 m (∼60-70 kyr) indicate that smoothing of the CO2 record by diffusion in deep ice is comparable to smoothing in the firn. Other types of diffusion (e.g. via liquid in ice grain boundaries or veins) may also be important but their influence has not been quantified.
Revue / Journal Title
Journal of Glaciology ISSN 0022-1430 CODEN JOGLAO
Source / Source
2008, vol. 54, no187, pp. 685-695 [11 page(s) (article)] (1 p.1/2)

so this study shows; tentatively I might add because this issue is just recently being studied in detail ( article was only just published in 2008 ), that there may be a huge lag in stable co2 samples from ice cores at certain depths and certain temps.

if you want to read the whole article you are welcome to at

http://www.google.com/url?sa=t&sourc...w8zBbnTH8vuytQ

also there is a simple logic that unfortunately escapes most people who argue these glaciations and corresponding co2 levels

Im going to modify something that a denier wrote on another forum who actually had it right but left out a few key components so it would sound like it supported his diatribe

Ice core samples, by definition, must be taken on polar ice caps, because that's the only place where ice stays frozen year-round, and the only place where it can accumulate year after year. But polar ice caps are surrounded by millions of square miles of near-freezing water. Water absorbs carbon dioxide. In fact, the solubility of carbon dioxide in water increases, geometrically, as water temperature decreases, reaching maximum solubility at the freezing point. Of course, this is also true of nitrogen and oxygen, the two primary components of air. However, carbon dioxide is much more soluble than either of those at all temperatures. At the freezing point, carbon dioxide is 30 times more soluble than oxygen and 70 times more soluble than nitrogen. Now, if you have all this very cold, nearly freezing water surrounding these ice caps, sucking up carbon dioxide out of the polar atmosphere, at nearly the highest possible rate, 30 times faster than oxygen, and 70 times faster than nitrogen, doesn't it stand to reason that the air that remains might just have a lot less carbon dioxide in it than the atmosphere across the rest of the planet? This is the air that is being trapped in air bubbles, to be preserved in ice core samples. And it is not representative of the atmosphere as a whole. which is likely to contain higher concentrations of co2. So what happens during a glaciation period is that once things freeze over a wider area and less and less of the co2 is being absorbed by the area in the imediate vicinity of where we take the ice cores then it appears that the co2 level goes up "after" the glaciation whereas in reality it was the local conditions that influence the local levels of co2 that end up trapped in ice bubbles and provide us with sample from which to derive local conditions at the time

this combined with the issue of ice permeability which is only just now being studied is a key factor in why we must remain patient in determining which came first, the chicken or the egg, so to speak in regards to the palio climate, in regards to the alterations we are making in our present atmospheric chemistry the point is kinda moot because we have direct measurements a rising temp in virtual lockstep with rising co2 concentrations.

It was simply a mater of the science catching up to the measurement system, IE not all that wander are lost. Often times once the true complexities are understood similar readings and data sets can reveal entirely different results.

by the way just to show how these time scales have developed one of the first articles to address this issue came up with a time frame of only 10-50 years, since then its grown considerably as the science progresses

if you would like to read the entire article please see
http://www.igsoc.org/annals/10/igs_a..._pg141-145.pdf

ABSTRACT
The air trapped in the bubbles of natural ice is not
the. same age as the surrounding ice. This is due to the fact
that the air is enclosed in isolated bubbles only at the
depth of the firn-ice transition. Within the overlying porous
firn layer the air is able to mix and to exchange to a
certain degree with the atmosphere. The age difference
between ice and air is given by the age of the ice at pore
close-off, less the mixing delay. Also, there is an age
distribution due to diffusive smoothing and due to the
gradual enclosure of the air at the firn-ice transition.
Knowledge of this age relation is necessary for the
interpretation of climatic parameters measured on ice cores.
This work concentrates on the effect of diffusive mixing.
We report on measurements of the diffusivity of CO2 and
02 (in N2) in firn samples from Siple Station, Antarctica. It
is shown that the dominant mixing process is molecular
diffusion. The diffusion coefficient depends approximately
linearly on the porosity. A one-dimensional diffusion model
has been used to calculate the air mixing in firn at Siple
Station (Antarctica), at the South Pole, and at Station Crete
(Greenland). An exchange time of between 10 and 50 years
is obtained.

anyway I could go on but somehow I doubt I'm really getting through to you anyway so believe what you will its the readers I'm primarily interested in and I think they can clearly see that the issue of permeability pretty much precludes any snap decisions concerning the arctic ice records concerning co2

[fasteddy106]

It would appear that Boston the Weasel is still posting misinformation. Here is more from the taxpayer supported climate parasites and grant whores at NASA.


http://joannenova.com.au/2010/07/did...rn-hemisphere/

[Guillermo]

Continuing talking about CO2 and the allegued planet warming due to its greenhouse effect, I want to bring your attention back to my posts 4067, 4071, and 4659

There I posted about Dr. Qing-Bin Lu suggesting that the man-made cause of global warming is not CO2 and the international treaty that saved the planet is not the Kyoto Protocol but the Montreal Protocol of 1987. Rather, says Dr. Lu, the true cause of global warming has been CFCs, or chlorofluorocarbons, once widely used in aerosol cans and refrigeration. As CFC use soared in the decades following World War II, he explains, the globe started warming dramatically. The world stopped warming dramatically when government regulations began to phase out CFCs, an event that culminated in the western world in 2000. Almost immediately afterward, in 2002, the world began to cool as CFCs started to diminish in our atmosphere.

Professor Lu, a path-breaking scientist in the field of ozone protection, made his CO2 discovery by accident — he was looking for culprits in the formation of the ozone hole over Antarctica. A chief suspect was CO2: Climate models produced by climatologists showed that CO2 would have devastating effects on the ozone layer, significantly enlarging the ozone hole over Antarctica and dramatically enlarging it over the Arctic. But when Dr. Lu compared the imagined output of the climate models with the actual measurements taken real-time by satellites and weather balloons, the models turned out to be soaring failures.

“I didn’t see any CO2 effect on temperature or ozone depletion over the South Pole from 1956 to 2008,” explained Dr. Lu, surprised at how totally different the real-world measurements were from those that the climate model predicted. The real-world measurements showed CO2 to be largely irrelevant – “the global warming on Earth’s surface between 1950 and 2000 is pretty much due to CFCs,” he concluded. “The models say that CO2 is a major greenhouse gas but the facts show otherwise.”


This was the then cited paper:
Cosmic-ray-driven electron-induced reactions of halogenated molecules adsorbed on ice surfaces: Implications for atmospheric ozone depletion and global climate change
Qing-Bin Lu, Department of Physics and Astronomy and Departments of Biology and Chemistry, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
Accepted 26 November 2009. editor: S. Peyerimhoff. Available online 3 December 2009.

http://www.sciencedirect.com/science...ed15d17ad2037e


Now Dr. Lu has just published another paper on the matter (Journal of Cosmology, June 2010), available in PDF format here:

What is the Major Culprit for Global Warming: CFCs or CO2?

ABSTRACT
"A recent observation strikingly showed that global warming from 1950 to 2000 was most likely caused by the significant increase of chlorofluorocarbons (CFCs) in the Earth atmosphere (Lu, 2010). Here, three key questions are addressed: (1) How could CO2 play a negligible role in recent global warming in view of its extremely high concentrations of ≥300 ppm? (2) Is there other evidence from satellite or ground measurements for the saturation in warming effect of CO2 and other non-CFC gases? And (3) could the greenhouse effect of CFCs alone account for the rise of 0.5~0.6 K in global temperature since 1950? First, the essential feature of the Earth blackbody radiation is elucidated. Then re-analyses of observed data about global temperature change with variations of halocarbons and CO2, the atmospheric transmittance of the infrared radiation and the 1970-1997 change in outgoing longwave radiation spectra of the Earth are presented. It follows by new theoretical calculations of the greenhouse effect of halocarbons. The results strength the conclusion that humans were responsible for global warming in late 20th century, but CFCs, rather than CO2 ,were the major culprit; a long-term global cooling starting around 2002 is expected to continue for next five to seven decades."



P.S.: At RealClimate they made in dec 2008 their last of their usual scorning posts about Dr. Lu's work here: http://www.realclimate.org/index.php...d-cosmic-rays/ No new posts on this matter since then.

[Guillermo]

From the last Lu's paper:

5. Concluding remarks
In comparison with previous calculations on the greenhouse effect of CFCs, the present calculations give rise to a larger greenhouse effect. This is due to two factors: the former calculations significantly underestimated the amplification factor of water vapor feedbacks by using a much smaller β value of 0.15 (Ramanathan, 1975) and also overestimated the greenhouse effect of CO2 by assuming a logarithmical increase in radiative forcing of CO2 with increasing concentration (Ramanathan et al., 1985, 1998; IPCC, 2001, 2007). These should be revised with the present observations.

It should be noted that the application of the CO2-palaeoclimate relation to the recent anthropogenic warming is questionable. Some studies reviewed in the IPCC Reports (2001, 2007) showed that CO2 co-varied with Antarctic temperature over glacial-interglacial cycles, suggesting a close link between CO2 variation and temperature. Ice core records, however, indicate that the rise in atmospheric CO2 is the effect rather than the cause of surface warming in palaeoclimate. For instance, a rapid rise by 5 °C in global average sea surface temperature occurred during transitions from the last Glacial Maximum to the onset of Holocene times; detailed ice core studies by Smith et al. (1999) found that the concentration of atmosphere CO2 increased by about 80 ppm (from ~190 to 270 ppm). But the latter was due to the effect of the rise in global surface temperature on driving more CO2 emission predominantly from the ocean (Smith et al., 1999). If one reversed the sequence and took the CO2 increase as the cause of the 5 °C rise in global surface temperature, then it would be extremely difficult to understand why no global temperature increases were observed for the increases of atmospheric CO2 from 285 to 308 ppm and 310 to 330 ppm in the decades from 1850 to 1930 and 1950 to 1975, respectively. In fact, high-resolution ice core records of temperature proxies and CO2 during deglaciations generally show that Antarctic temperature started to rise about one thousand years before the rise of atmospheric CO2, as well observed by Fischer et al. (1999), Veizer et al. (2000), Caillon et al. (2003) and Stott et al. (2007). And despite strongly decreasing temperatures, high CO2 concentrations can be sustained for thousands of years during glaciations (Fischer et al., 1999). These facts indicate that atmospheric CO2 was not the main cause of these climate transitions (Smith et al., 1999; Fischer et al., 1999; Veizer et al., 2000; Caillon et al., 2003; Stott et al., 2007).

Finally, accurate and reliable analysis of satellite datasets are often affected by the climate models that investigators use. This is to some extent caused by the complexity of the scientific issue, which might require the use of a certain climate model to guide the data analysis. On the other hand, researchers should also be aware of the fact that used climate models may be incorrect or incomplete. An open opinion about different models may be instrumental in revealing the truth. This study did not aim to make precise calculations of global temperature change with a sophisticated climate model including multiple parameters and factors. But it does show that the warming effect of CO2 and other non-CFC gases had most likely saturated and CFCs and HCFCs could account for global warming observed in the late 20th century. A long-term global cooling starting around 2002 is expected to continue for next five to seven decades.

(bolded is mine)

[Guillermo]

Here a link to Dr. Lu's selected publications and conference presentations:

http://www.science.uwaterloo.ca/~qblu/publications.html


Just to avoid the usual idiotic commentaries about Big-Oil and the like, Dr. Lu's fundings come from:

Ontario’s Ministry of Research and Innovation (Dr. Lu was recently receiving an Early Researcher Award)

Canadian Institutes of Health Research (CIHR)

Natural Sciences and Engineering Research Council of Canada (NSERC)

Canada Foundation of Innovation (CFI)

Ontario Innovation Trust (OIT)

University of Waterloo

[Guillermo]

I cannot resist to post also this, about CO2 lagging temperature during the last deglaciation from NOAA's very own pages:

Southern Hemisphere and Deep-Sea Warming Led Deglacial Atmospheric CO2 Rise and Tropical Warming
Science Vol. 318. No. 5849, pp. 435 - 438, 19 October 2007, doi:10.1126/science.1143791.
Lowell Stott, Axel Timmermann, and Robert Thunell

ABSTRACT:
Establishing what caused Earth's largest climatic changes in the past requires a precise knowledge of both the forcing and the regional responses. We determined the chronology of high- and low-latitude climate change at the last glacial termination by radiocarbon dating benthic and planktonic foraminiferal stable isotope and magnesium/calcium records from a marine core collected in the western tropical Pacific. Deep-sea temperatures warmed by ~2°C between 19 and 17 thousand years before the present (ky B.P.), leading the rise in atmospheric CO2 and tropical-surface-ocean warming by ~1000 years. The cause of this deglacial deep-water warming does not lie within the tropics, nor can its early onset between 19 and 17 ky B.P. be attributed to CO2 forcing. Increasing austral-spring insolation combined with sea-ice albedo feedbacks appear to be the key factors responsible for this warming.

http://www.ncdc.noaa.gov/paleo/pubs/...stott2007.html

And this is not ice-cores based.

[Boston]

bla bla bla we have all seen this dog and pony show before

to which I have previously responded with ( for the benefit of our readers I will post it again )

The lag between temperature and CO2. (Gore’s got it right.)
Filed under:

* Arctic and Antarctic
* Climate Science
* Greenhouse gases
* Paleoclimate

— eric @ 27 April 2007 - (Italian) (Español)

When I give talks about climate change, the question that comes up most frequently is this: “Doesn’t the relationship between CO2 and temperature in the ice core record show that temperature drives CO2, not the other way round?”

On the face of it, it sounds like a reasonable question. It is no surprise that it comes up because it is one of the most popular claims made by the global warming deniers. It got a particularly high profile airing a couple of weeks ago, when congressman Joe Barton brought it up to try to discredit Al Gore’s congressional testimony. Barton said:

In your movie, you display a timeline of temperature and compared to CO2 levels over a 600,000-year period as reconstructed from ice core samples. You indicate that this is conclusive proof of the link of increased CO2 emissions and global warming. A closer examination of these facts reveals something entirely different. I have an article from Science magazine which I will put into the record at the appropriate time that explains that historically, a rise in CO2 concentrations did not precede a rise in temperatures, but actually lagged temperature by 200 to 1,000 years. CO2 levels went up after the temperature rose. The temperature appears to drive CO2, not vice versa. On this point, Mr. Vice President, you’re not just off a little. You’re totally wrong.

Of course, those who’ve been paying attention will recognize that Gore is not wrong at all. This subject has been very well addressed in numerous places. Indeed, guest contributor Jeff Severinghaus addressed this in one of our very first RealClimate posts, way back in 2004. Still, the question does keep coming up, and Jeff recently received a letter asking about this. His exchange with the letter writer is reproduced in full at the end of this post. Below is my own take on the subject.

First of all, saying “historically” is misleading, because Barton is actually talking about CO2 changes on very long (glacial-interglacial) timescales. On historical timescales, CO2 has definitely led, not lagged, temperature. But in any case, it doesn’t really matter for the problem at hand (global warming). We know why CO2 is increasing now, and the direct radiative effects of CO2 on climate have been known for more than 100 years. In the absence of human intervention CO2 does rise and fall over time, due to exchanges of carbon among the biosphere, atmosphere, and ocean and, on the very longest timescales, the lithosphere (i.e. rocks, oil reservoirs, coal, carbonate rocks). The rates of those exchanges are now being completely overwhelmed by the rate at which we are extracting carbon from the latter set of reservoirs and converting it to atmospheric CO2. No discovery made with ice cores is going to change those basic facts.

Second, the idea that there might be a lag of CO2 concentrations behind temperature change (during glacial-interglacial climate changes) is hardly new to the climate science community. Indeed, Claude Lorius, Jim Hansen and others essentially predicted this finding fully 17 years ago, in a landmark paper that addressed the cause of temperature change observed in Antarctic ice core records, well before the data showed that CO2 might lag temperature. In that paper (Lorius et al., 1990), they say that:

changes in the CO2 and CH4 content have played a significant part in the glacial-interglacial climate changes by amplifying, together with the growth and decay of the Northern Hemisphere ice sheets, the relatively weak orbital forcing

What is being talked about here is influence of the seasonal radiative forcing change from the earth’s wobble around the sun (the well established Milankovitch theory of ice ages), combined with the positive feedback of ice sheet albedo (less ice = less reflection of sunlight = warmer temperatures) and greenhouse gas concentrations (higher temperatures lead to more CO2 leads to warmer temperatures). Thus, both CO2 and ice volume should lag temperature somewhat, depending on the characteristic response times of these different components of the climate system. Ice volume should lag temperature by about 10,000 years, due to the relatively long time period required to grow or shrink ice sheets. CO2 might well be expected to lag temperature by about 1000 years, which is the timescale we expect from changes in ocean circulation and the strength of the “carbon pump” (i.e. marine biological photosynthesis) that transfers carbon from the atmosphere to the deep ocean.

Several recent papers have indeed established that there is lag of CO2 behind temperature. We don’t really know the magnitude of that lag as well as Barton implies we do, because it is very challenging to put CO2 records from ice cores on the same timescale as temperature records from those same ice cores, due to the time delay in trapping the atmosphere as the snow is compressed into ice (the ice at any time will always be older than the gas bubbles it encloses, and the age difference is inherently uncertain). Still, the best published calculations do show values similar to those quoted by Barton (presumably, taken from this paper by Monnin et al. (2001), or this one by Caillon et al. (2003)). But the calculations can only be done well when the temperature change is large, notably at glacial terminations (the gradual change from cold glacial climate to warm interglacial climate). Importantly, it takes more than 5000 years for this change to occur, of which the lag is only a small fraction (indeed, one recently submitted paper I’m aware of suggests that the lag is even less than 200 years). So it is not as if the temperature increase has already ended when CO2 starts to rise. Rather, they go very much hand in hand, with the temperature continuing to rise as the the CO2 goes up. In other words, CO2 acts as an amplifier, just as Lorius, Hansen and colleagues suggested.

Now, it there is a minor criticism one might level at Gore for his treatment of this subject in the film (as we previously pointed out in our review). As it turns out though, correcting this would actually further strengthen Gore’s case, rather than weakening it. Here’s why:

The record of temperature shown in the ice core is not a global record. It is a record of local Antarctic temperature change. The rest of the globe does indeed parallel the polar changes closely, but the global mean temperature changes are smaller. While we don’t know precisely why the CO2 changes occur on long timescales, (the mechanisms are well understood; the details are not), we do know that explaining the magnitude of global temperature change requires including CO2. This is a critical point. We cannot explain the temperature observations without CO2. But CO2 does not explain all of the change, and the relationship between temperature and CO2 is therefore by no means linear. That is, a given amount of CO2 increase as measured in the ice cores need not necessarily correspond with a certain amount of temperature increase. Gore shows the strong parallel relationship between the temperature and CO2 data from the ice cores, and then illustrates where the CO2 is now (384 ppm), leaving the viewer’s eye to extrapolate the temperature curve upwards in parallel with the rising CO2. Gore doesn’t actually make the mistake of drawing the temperature curve, but the implication is obvious: temperatures are going to go up a lot. But as illustrated in the figure below, simply extrapolating this correlation forward in time puts the Antarctic temperature in the near future somewhere upwards of 10 degrees Celsius warmer than present — rather at the extreme end of the vast majority of projections (as we have discussed here).

Global average temperature is lower during glacial periods for two primary reasons:
1) there was only about 190 ppm CO2 in the atmosphere, and other major greenhouse gases (CH4 and N2O) were also lower
2) the earth surface was more reflective, due to the presence of lots of ice and snow on land, and lots more sea ice than today (that is, the albedo was higher).
As very nicely discussed by Jim Hansen in his recent Scientific American article, the second of these two influences is the larger, accounting for about 2/3 of the total radiative forcing. CO2 and other greenhouse gases account for the other 1/3. Again, this was all pretty well known in 1990, at the time of the Lorius et al. paper cited above.

What Gore should have done is extrapolated the temperature curve according this the appropriate scaling — with CO2 accounting for about 1/3 of the total change — instead of letting the audience do it by eye. Had he done so, he would have drawn a line that went up only 1/3 of the distance implied by the simple correlation with CO2 shown by the ice core record. This would have left the impression that equilibrium warming of Antarctica due to doubled CO2 concentrations should be about 3 °C, in very good agreement with what is predicted by the state-of-the-art climate models. (It is to be noted that the same models predict a significant delay until equilibrium is reached, due to the large heat capacity of the Southern ocean. This is in very good agreement with the data, which show very modest warming over Antarctica in the last 100 years). Then, if you scale the Antarctic temperature change to a global temperature change, then the global climate sensitivity to a doubling of CO2 becomes 2-3 degrees C, perfectly in line with the climate sensitivity given by IPCC (and known from Arrhenius’s calculations more than 100 years ago).

In summary, the ice core data in no way contradict our understanding of the relationship between CO2 and temperature, and there is nothing fundamentally wrong with what Gore says in the film. Indeed, Gore could have used the ice core data to make an additional and stronger point, which is that these data provide a nice independent test of climate sensitivity, which gives a result in excellent agreement with results from models.

A final point. In Barton’s criticism of Gore he also points out that CO2 has sometimes been much higher than it is at present. That is true. CO2 may have reached levels of 1000 parts per million (ppm) — perhaps much higher — at times in the distant geological past (e.g. the Eocene, about 55 million years ago). What Barton doesn’t bother to mention is that the earth was much much warmer at such times. In any case, more relevant is that CO2 has not gone above about 290 ppm any time in the last 650,000 years (at least), until the most recent increase, which is unequivocally due to human activities.

and again this

What does the lag of CO2 behind temperature in ice cores tell us about global warming?
Filed under:

* FAQ
* Greenhouse gases
* Paleoclimate

— group @ 3 December 2004 - (Français)

This is an issue that is often misunderstood in the public sphere and media, so it is worth spending some time to explain it and clarify it. At least three careful ice core studies have shown that CO2 starts to rise about 800 years (600-1000 years) after Antarctic temperature during glacial terminations. These terminations are pronounced warming periods that mark the ends of the ice ages that happen every 100,000 years or so.

Does this prove that CO2 doesn’t cause global warming? The answer is no.

The reason has to do with the fact that the warmings take about 5000 years to be complete. The lag is only 800 years. All that the lag shows is that CO2 did not cause the first 800 years of warming, out of the 5000 year trend. The other 4200 years of warming could in fact have been caused by CO2, as far as we can tell from this ice core data.

The 4200 years of warming make up about 5/6 of the total warming. So CO2 could have caused the last 5/6 of the warming, but could not have caused the first 1/6 of the warming.

It comes as no surprise that other factors besides CO2 affect climate. Changes in the amount of summer sunshine, due to changes in the Earth’s orbit around the sun that happen every 21,000 years, have long been known to affect the comings and goings of ice ages. Atlantic ocean circulation slowdowns are thought to warm Antarctica, also.

From studying all the available data (not just ice cores), the probable sequence of events at a termination goes something like this. Some (currently unknown) process causes Antarctica and the surrounding ocean to warm. This process also causes CO2 to start rising, about 800 years later. Then CO2 further warms the whole planet, because of its heat-trapping properties. This leads to even further CO2 release. So CO2 during ice ages should be thought of as a “feedback”, much like the feedback that results from putting a microphone too near to a loudspeaker.

In other words, CO2 does not initiate the warmings, but acts as an amplifier once they are underway. From model estimates, CO2 (along with other greenhouse gases CH4 and N2O) causes about half of the full glacial-to-interglacial warming.

So, in summary, the lag of CO2 behind temperature doesn’t tell us much about global warming. [But it may give us a very interesting clue about why CO2 rises at the ends of ice ages. The 800-year lag is about the amount of time required to flush out the deep ocean through natural ocean currents. So CO2 might be stored in the deep ocean during ice ages, and then get released when the climate warms.]

To read more about CO2 and ice cores, see Caillon et al., 2003, Science magazine

so while the same old tired diatribe is trotted out once again the simple reality of it all is that this issue has been considered again and again and its another non issue that the deniers would love to pretend is

nice try but once again
the truth will out kids
the truth will out