Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Donate

Twitter Facebook YouTube Pinterest

RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
Keep me logged in
New? Register here
Forgot your password?

Latest Posts

Archives

CO2 levels during the late Ordovician

Posted on 12 March 2010 by John Cook

One argument used against the warming effect of carbon dioxide is that millions of years ago, CO2 levels were higher during periods where large glaciers formed over the Earth's poles. This argument fails to take into account that solar output was also lower during these periods. The combined effect of sun and CO2 show good correlation with climate (Royer 2006). The one period that until recently puzzled paleoclimatologists was the late Ordovician, around 444 million years ago. At this time, CO2 levels were very high, around 5600 parts per million (in contrast, current CO2 levels are 389 parts per million). However, glaciers were so far-reaching during the late Ordovician, it coincided with one of the largest marine mass extinction events in Earth history. How did glaciation occur with such high CO2 levels? Recent data has revealed CO2 levels at the time of the late Ordovician ice age were not that high after all.

Past studies on the Ordovician period calculated CO2 levels at 10 million year intervals. The problem with such coarse data sampling is the Ordovician ice age lasted only half a million years. To fill in the gaps, a 2009 study examined strontium isotopes in the sediment record (Young 2009). Strontium is produced by rock weathering, the process that removes CO2 from the air. Consequently, the ratio of strontium isotopes can be used to determine how quickly rock weathering removed CO2 from the atmosphere in the past. Using strontium levels, Young determined that during the late Ordovician, rock weathering was at high levels while volcanic activity, which adds CO2 to the atmosphere, dropped. This led to CO2 levels falling below 3000 parts per million which was low enough to initiate glaciation - the growing of ice sheets.

Last week, another study headed by Seth Young further examined this period by extracting sediment cores from Estonia and Anticosti Island, Canada (Young 2010). The cores were used to construct a sequence of carbon-13 levels from rocks formed during the Ordovician. This was used as a proxy for atmospheric CO2 levels, at a much higher resolution than previous data. What they found was consistent with the strontium results in Young 2009 - CO2 levels dropped at the same time that sea surface temperatures dropped and ice sheets expanded. As the ice sheets grew to cover the continent, rock weathering decreased. This led to an increase in atmospheric CO2 which caused global warming and a retreat of the glaciers.

Thus arguments that Ordovician glaciation disproves the warming effect of CO2 are groundless. On the contrary, the CO2 record over the late Ordovician is entirely consistent with the notion that CO2 is a strong driver of climate.

0 0

Bookmark and Share Printable Version  |  Link to this page

Comments

1  2  Next

Comments 1 to 50 out of 87:

  1. Can someone please give the real scientific explanation why CO2 drives global warming? Correlation does not guarantee cause. Put C)2 in a large glass chamber and measure the change in the rate of heat dissipation compared to nitrogen and it will not alter the rate of heat transferrance. Can someone create a valid scientific experiment to prove or disprove this?

    Thanks.
    0 0
    Response: The first scientific experiment proving the warming effect of carbon dioxide was conducted in 1861 when John Tyndal published laboratory results identifying carbon dioxide as a greenhouse gas that absorbed heat rays (longwave or infrared radiation). Since then, the absorptive qualities of carbon dioxide have been more precisely quantified by decades of laboratory measurements (Herzberg 1953, Burch 1962, Burch 1970, etc).

    Of course, there's no substitute for measurements made in the real world. Satellites have measured less infrared radiation escaping to space at the same wavelenths absorbed by greenhouse gases (Harries 2001, Griggs 2004, Chen 2007). The authors concluded this was "direct experimental evidence for a significant increase in the Earth's greenhouse effect".

    In science, the only thing better than direct measurements are multiple sets of independent measurements finding the same thing. Surface measurements also find an increase of infrared radiation heading back down towards Earth, confirmation of an enhanced greenhouse effect (Philipona 2004, Puckrin 2004Wild 2008, Wang 2009). A close analysis of the downward infrared spectrum finds more energy coming back down at the same absorptive wavelengths of carbon dioxide and other greenhouse gases, thus concluding "this experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming." (Evans 2006)
  2. From everything I've read on the subject, though, the temperatures at which glaciation occurred during the Ordovician Era were higher than the temperatures at which similar glaciation occurred during the entirety of the Quaternary Era.
    0 0
  3. nerndt at 17:10 PM on 12 March, 2010

    Also see

    The Carbon Dioxide Greenhouse Effect

    for more history about how C02 was identified as a substance that can alter the radiative transfer properties of the atmosphere. The link points to a chapter of Dr. Spencer Weart's excellent book on the topic.
    0 0
  4. Some earlier work in this field:
    Press release - http://researchnews.osu.edu/archive/earlyice.htm
    Paper itself - http://geology.geoscienceworld.org/cgi/content/abstract/33/2/109
    Seems the argument hasn't held much weight for a few years now.
    0 0
  5. While John Tyndall (1820-1893) gave us the first picture of the effect of the absorption of heat radiation by gases, his contribution should be taken in context. In 1896 Svante Arrhenius published his calculations on a basic heat budget for the earth based on his estimate and projection of anthropogenic CO2 being introduced into the earth's atmosphere. Broadly, the Arrhenius estimates remain valid today well over 100 years later.

    In his classic 1949 text Radiative Transfer, Subrahmanyan Chandrasekhar gave us a comprehensive view of the behavior of light radiation passing through a planetary atmosphere and how the gas mixture of that atmosphere would capture some of the radiation and re-release some or all as heat while some would be reflected back into space.

    A classic journal article that illustrates the contribution of CO2 to climate change must be "Carbon Dioxide and the Climate" by Gilbert Plass (American Scientist, 1956).

    Dr. Plass describes CO2 sources and sinks and makes salient predictions about their impact to our environment. For this and other contributions, Dr. Plass is considered the 'father' of modern greenhouse gas theory.

    From Jean-Baptiste Fourier to today we have a mountain of literature and journal articles but none of this in total can counterbalance a passionate "believer" because the "believer" is not constrained by calculus or physics or the aerosol and gas chemistry of our atmosphere.

    The "believer" chooses to not see the thermodynamics of our cryosphere where the arctic ice cover is now so reduced that German and Russian merchant vessel traffic is free to execute a polar transit cutting thousands of miles of travel off a voyage from Asia to Europe.

    The general public has been misled to the "belief" that anthropogenic global warming is an issue of public discourse and that in that discourse they can legitimately influence the outcome of changes in the earth's climate when in fact the outcome is influenced by physics and chemistry.

    If there is a 'problem' it is the in the public view the scope and impact of anthropogenic global warming has been reduced to a question that has a 'single answer'.

    Unfortunately, science in its essence subdivides any question into smaller, more fundamental questions and in answering those myriad of smaller questions assembles and answer which is a tapestry.
    0 0
  6. For nerndt:

    Can someone please give the real scientific explanation why CO2 drives global warming.. Can someone create a valid scientific experiment to prove or disprove this
    "

    There are 2 parts, and I can only answer one. This is the explanation of how CO2 adds radiation at the earth's surface. For the subject of "global warming" - well, everything else in the climate has to be taken into account.

    But I think your question is about the first issue - how in the first place does CO2 add heat at the earth's surface?

    Take a look at CO2-An Insignificant Trace Gas - Visualization

    What you see there, amongst other concepts, is the longwave radiation leaving the earth's surface - at 390W/m^2 on average, and yet at the top of atmosphere this outgoing longwave radiation is only about 240W/m^2. Where has this longwave radiation gone? It has been absorbed and re-radiated both up and down.

    This "earth experiment" should demonstrate the reality of the theory of how CO2 adds warming at the earth's surface.
    0 0
  7. Where you say: "Strontium is produced by rock weathering, the process that removes CO2 from the air."

    I think you probably mean "Strontium is mobilised by rock weathering, the process that removes CO2 from the air."

    Sorry if that sounds a bit nit-picky - to me (a geologist) it read as if rock weathering results in an element coming into being!! Instead, Sr is present as a minor element in certain minerals e.g. feldspars, and upon their prolonged weathering it is taken into solution.

    Interesting piece: here in Mid Wales there are several localities that show the abrupt chance in sedimentary facies marking the transition from shallower to deep-water conditions that mark the end of this glaciation. The Cwmere Formation, mostly black, hemipelagic pyritic graptolitic organic-rich mudstones, represents the time following the major sealevel rise and cut-off from coarse sediment sources. It is an important marker-horizon across Central Wales, as things controlled by major eustatic sealevel changes associated with deglaciation tend to be!

    Cheers - John
    0 0
  8. Oops - for "chance" read "change"! Damn this old keyboard!
    0 0
  9. It seems a lot of things started happening in the Ordovician period:
    first primitive plants colonized land *
    Volcanoes went rampant *x*
    Continental submergence *x*


    [*] http://geosci.uchicago.edu/~rtp1/ClimateBook/ClimateWorkbook.pdf

    [*x*]http://library.thinkquest.org/20886/ordovician.htm
    0 0
  10. Chris Colose has a great tutorial called Greenhouse Effect Revisited

    Another good tutorial that is less mathematical is:
    The Greenhouse Effect & Greenhouse Gases (UCAR)

    My personal favorite is from theoretical physicist Arthur Smith here:

    Proof of the Atmospheric Greenhouse Effect
    0 0
  11. So what if CO2 is the cause of warming. Bring it on I say. Providing its not going to poison us then where's the harm?

    We can only benefit by it.

    It will turn the Earth into a garden of Eden :-)

    As a child I loved visiting my uncle's green house. All the luscious plants both vegetables and flowers. I thought then, wouldn't it be wonderful for the whole world to be like this. Now we have the opportunity to make so and feed the whole world :-)

    The only problem is that coastal low lying land will be flooded. However I don't see it as a problem only an opportunity to engage all the world's unemployed in construction to rebuild on higher land and to turn the coastal cities into Venice's. Providing the existing buildings' foundations are on bedrock there will be no subsidence and new roadways and pavements can be constructed at new levels.

    The difference between a pessimist and an optimist is one sees problems in every opportunity, the other sees opportunity in every problem !
    0 0
  12. Excellent response, John. This is one of the Denier talking points that I've not had a good response to - but now I do! :)
    0 0
  13. Ok Miekol,

    I'm assuming that your tongue is firmly in your cheek, but I'll bite anyway.

    What cost would you put on this mammoth re-building task? Is it likely to go ahead for the inhabitants of the Maldives, Seychelles, Bangladesh, Micronesia? What highlands do those people have. Each time Bangladesh floods 100s die, thousands suffer from epidemics from contaminated water and millions are made homeless.

    What happens when rainfall patterns are disrupted causing problems for food growers, or when plants are ready for pollination too early for the insects that traditionally pollinate them?
    0 0
  14. 1. Never in the history of Earth is not observed (clearly proven) first increase in CO2 concentration and then the temperature rise. Has always been the opposite. Often, the first temperature and then decreased CO2 content.
    2. As to the true RF CO2 in the atmosphere, even without Lindzen'a, opinions are more than different. I remember a graph based on the IPCC Fourth Report: http://www.americanthinker.com/Attachment%202.PNG. Currently, most researchers believe that the direct RF of CO2 doubling is up to circa 1 deg C, the rest is very hypothetical feedback.
    3. K.E. Trenberth, J. Fasullo, L. Smith, 2005: Trends and variability in column-integrated atmospheric water vapor. Climate Dynamics 24: 741–758, DOI 10.1007/s00382-005-0017-4, fig. 11 - Is parallel to the increase of CO2 content of water vapor - also a greenhouse gas; in the atmosphere. So it is possible to reverse the sequence of events - increase: 1 temperature - 2 water vapor and 3: CO2.
    4. "This led to an increase in atmospheric CO2 which caused global warming and a retreat of the glaciers." - It is only a hypothesis, to prove that there is sufficient evidence. Equally, it could be the result of the cause.
    5. Conclusion: The data from the Ordovician does not give any evidence both for and against.
    0 0
  15. "What happens when rainfall patterns are disrupted causing problems for food growers, or when plants are ready for pollination too early for the insects that traditionally pollinate them?"

    The current species of insects and plants have existed for hundreds of thousands of years and survived a much more violent changes. In addition, cold = reduction of species; warm = evolution of radiation.
    0 0
  16. nerndt at 17:10 PM on 12 March, 2010
    "Can someone please give the real scientific explanation why CO2 drives global warming?"

    Response:
    "...Of course, there's no substitute for measurements made in the real world. ..."

    To nerndt...
    The right way to prove this would be to compare the cooling profile of a large mass (perhaps a heavy anvil at 100 C.) shrouded within a chamber filled with a controlled gas. The comparison would be made to see the difference in cooling of the mass with air mixed at 250ppm CO2 and another with 350ppm CO2.

    All "real world" references I have seen of this experiment focus on how the gas with a higher percentage of CO2 warms more than than the one with a lower percentage of CO2, which proves very little since the amount of mass associated with the extra CO2 is miniscule.

    This is similar to viewing problems of conservation of momentum with an inelastic collision. If two bodies m1 and m2 collide, for instance, the velocities after collision will depend on the masses. In this case, the anvils heat capacity is huge, that of CO2 is tiny. CO2's capacity to absorb energy becomes "saturated" and all the IR goes right through. This is the grand flaw of AGW. Very good question. There is your answer.
    0 0
  17. Arkadiusz Semczyszak,
    there has been no CO2 leading an increase in temperature just because there has never been humans around able to produce it in such large quantities. The only notable exception is the coming out of the earth from the so called snowball state. But anyway, now we are here. If the CO2 acted as a feedback in the past, it means that it is able to trap heat; there's no reason to believe that because now it is emitted by human activities it stops doing his job.
    If you are not convinced by this simple fact, look at how the concentration of CO2 is related to temperature during, for example, the glacial cycles. Plot one against the other yourself and put current values in the graph. To get to 380+ ppmv temperature should be several degrees higher than we are experiencing today. This rules out that CO2 is now increasing as a response to a temperature increase.
    0 0
  18. RSVP,
    the experiment you propose has not been done for a reason, it would not tell us anything about the greenhous effect on earth. Indeed, in an hypothetical atmosphere with no lapse rate you would not get any greenhouse effect.
    0 0
  19. there has been no CO2 leading an increase in temperature just because there has never been humans around able to produce it in such large quantities.


    Actually, the picture painted for the Ordovician appears to be such a case, just with limited precision and details in the beginning.

    i.e. high volcanic activity led to high levels of CO2 and a warmer world. Volcanic activity lessened, weathering of rocks lowered CO2 and the earth cooled to the point where extensive ice sheets grew.

    This led to less weathering, thus a growth in CO2 (presumably due to volcanism???), and warming.

    This picture clearly shows CO2 as being the "control knob" during the Ordovician.
    0 0
  20. Arkadiusz Semczyszak writes: Never in the history of Earth is not observed (clearly proven) first increase in CO2 concentration and then the temperature rise. Has always been the opposite. Often, the first temperature and then decreased CO2 content.

    This is a strange and illogical argument. When was the last time that people extracted large quantities of fossil carbon and injected it into the atmosphere?

    During the Pleistocene, CO2 changes have lagged temperature changes, because the temperature changes were driven by orbital forcings. Everybody understands this. It would be very hard to explain if CO2 didn't lag temperature in the ice core records! And the magnitude of the warming/cooling can't be recreated without inclusion of the CO2 feedback.

    Claiming that the CO2 lag during glacial/interglacial cycles proves that CO2 can't drive temperature in other circumstances is like arguing that the existence of fires caused by lightning proves that some other fire couldn't be caused by arson.

    Finally, there have probably been a number of cases in the climate record where CO2 increases led to temperature rises, rather than just serving as amplifying feedbacks. Flood basalt outbreaks are one example:

    Ganino 2009: "Most mass extinctions during the last 500 m.y. coincide with eruptions of large igneous provinces [...] Contact metamorphism around intrusions in dolomite, evaporite, coal, or organic-rich shale generates large quantities of greenhouse and toxic gases (CO2, CH4, SO2), which subsequently vent to the atmosphere and cause global warming and mass extinctions. The release of sediment derived gases had a far greater impact on the environment than the emission of magmatic gases."

    Saunders 2009: "Volcanism released large masses of sulphate aerosols and carbon dioxide, the former triggering short-duration volcanic winters, the latter leading to long-term warming. Whilst the mass of CO2 released from individual eruptions was small compared with the total mass of carbon in the atmosphere-ocean system, the long ‘mean lifetime’ of atmospheric CO2, compared with the eruption flux and duration, meant that significant accumulation could occur over periods of 10^5 years. Compromise of the carbon sequestration systems (by curtailment of photosynthesis, destruction of biomass, and warming and acidification of the oceans) probably led to rapid atmospheric CO2 build-up, warming, and shallow-water anoxia, leading ultimately to mass extinction."

    Svensen 2009: "The end of the Permian period is marked by global warming and the biggest known mass extinction on Earth. [...] Heating of organic-rich shale and petroleum bearing evaporites around sill intrusions led to greenhouse gas and halocarbon generation in sufficient volumes to cause global warming and atmospheric ozone depletion. Basin scale gas production potential estimates show that metamorphism of organic matter and petroleum could have generated > 100,000 Gt CO2. [...] The results indicate that global warming and ozone depletion were the two main drivers for the end-Permian environmental crisis."

    Kürschner 2008: "Our results demonstrate that this climate optimum was forced significantly by elevated CO2 levels similar to those, for example, during the early Eocene. A likely source of the late, early, and middle Miocene CO2 increases was extensive volcanic activity during the Columbia River Flood Basalt volcanism and the Central European volcanism. The marked CO2 drop during the Miocene, in turn, may be the result of increased Corg burial resulting from the Himalayan uplift and/or of enhanced marine productivity in the Pacific ocean and the global occurrence of vast brown-coal-forming basins."
    0 0
  21. Arkadiusz Semczyszak, even setting aside that the current CO2 increase preceded the current temperature increase AND that the climate record shows MANY cases of CO2 decreases preceding temperature decreases AND that the majority of EVERY major temperature increase in the record has been preceded by CO2 increases (that is, only a small portion of the temp increase preceded the CO2 rise)... your root principal would still be wrong. Around 700 million years ago nearly all of the water on the planet froze. This prevented the oceans from absorbing CO2 and thus allowed the atmospheric CO2 content to skyrocket... which then led to warming which brought the planet out of the 'Snowball Earth' state.

    The claim that CO2 changes always come AFTER temperature changes is simply false.

    RSVP, your model for testing the existence of the greenhouse effect seems to be lacking a Sun. Put in a visible light laser being continuously fired at the anvil to heat it up and make sure that the energy flows are significant enough for instruments to detect and you'd have a valid comparison.
    0 0
  22. dhogaza,
    true enough. I only find the snowball earth case clearer because it has puzzled scientist for a long while. There's no other plausible way to come out from an almost fully glaciated state and there are no other concomitant effect to possibly invoke.
    0 0
  23. RSVP at 01:37 AM on 13 March 2010

    Lest anybody who read RSVP's post regarding saturation wonder if the saturation argument is worthy, I recommend reading

    A Saturated Gassy Argument

    by Spencer Weart.

    Executive summary: RSVP's argument is too simple to capture the details of how this system functions. Weart is singularly gifted with explanation and explains how this RSVP's simple model is incorrect in a way all of us can understand.
    0 0
  24. Miekol conveniently forgets the increasing acidification of the ocean's and its consequent destruction of aquatic life.

    We can't survive with dead oceans.
    0 0
  25. @Arkadiusz Semczyszak,
    Both are true: Temperature rise releases CO2 and CO2 increases temperature rise. This is known as a "positive feedback loop", and it's very unfortunate. But if past warming events always preceeded CO2 increases, it wouldn't matter (even though you are wrong, they don't). Today we are increasing CO2 levels, which will increase temperatures, which will further increase CO2 levels beyond which we are directly responsible for.
    Your argument is A) Wrong and B) Not relevant.
    0 0
  26. @John Cook
    Is rock weathering factored in to CO2-rise predictions in the current models? As glacial retreat ends because the glaciers are gone, rock weathering will be at it's maximum. How similar in scale is this CO2 absorption compared to human output? (A century from now--[shudder])
    0 0
    Response: That's a good question. Rock weathering is a negative feedback - as temperature gets hotter, rock weathering activity increases so more CO2 is removed from the atmosphere. In fact, this is one of nature's "control knobs" to ensure climate doesn't get too hot or cold - when it gets colder, there's less CO2 removal which leads to CO2 rising and warming the earth. When the Earth gets too hot, rock weathering removes more CO2 which has a cooling effect.

    But unfortunately this process occurs over geological periods - over periods of thousands of years or greater. The process is way too small to offset our CO2 emissions (some hard numbers would be nice - can anyone help here?) So rock weathering is not a magic bullet that will save us from ourselves. However, there is research into accelerating rock weathering process as a way of sequestering CO2.
  27. "true enough. I only find the snowball earth case clearer because it has puzzled scientist for a long while. There's no other plausible way to come out from an almost fully glaciated state and there are no other concomitant effect to possibly invoke."

    Yes, the snowball earth case is great, I just found it ironic that Arkadiusz Semczyszak made his claim in response to a top post showing his claim to be false!
    0 0
  28. "Is rock weathering factored in to CO2-rise predictions in the current models? "

    This happens on geological timescales, as I understand it. However, speeding the process artificially is one of the geoengineering ideas kicked around out there.
    0 0
  29. I can throw in a few ideas regarding deep weathering and the timescales involved - if people are interested. I've researched & published on same over here in the UK. But right now, my tea's ready!

    It'll be UK-centric but I think I made some useful conclusions in my work. Be back later - likely in the morning UK time.

    Cheers - John
    0 0
  30. I've got another example of CO2 change fully preceding temperature change. The Azolla event.

    The relatively recent history of orbital cycles driving small warming/cooling trends that are amplified by CO2 (and thus giving the appearance of temperature leading CO2) might just be the exception, not the rule. It's all about what mechanisms are present.
    0 0
  31. paulgrace said: "@Arkadiusz Semczyszak,... if past warming events always preceeded CO2 increases, it wouldn't matter"

    The analogy I give skeptics is that just because a car accident usually precedes a broken car doesn't mean a broken car can't cause a car accident.
    0 0
  32. I can throw in a few ideas regarding deep weathering and the timescales involved - if people are interested


    Oh ... please! please! please! :)
    0 0
  33. While we are talking about the Snowball earth, I thought i'd post some paraphrased excerpts from the "Principles of Planetary Climate" the book John recommended to explain it a little better:

    The Snowball phenomenon is pregnant with Big Questions, the most obvious of which are:
    How do you get in? And how do you get out?...

    Most theories for the entry into a Snowball involve the drawdown of whatever greenhouse
    gas had previously been maintaining the planet’s warmth – usually CO2 and CH4 in some combination....

    Assuming for the moment that the cooling process caused a Hard Snowball, the next question
    is how to deglaciate the planet...Based on rather
    simple reasoning of the sort that will be covered in the remainder of this book, Kirschvink proposed
    that once the Earth freezes over, the weathering of silicate to carbonate (which requires liquid
    water washing over weatherable rocks) ceases, so that CO2 outgassed from the Earth’s interior
    accumulates in the atmosphere until it reaches concentrations sufficient to cause a deglaciation.


    I highly recommend this book to fellow n00bs!

    RE#32 dghozza: yes please!
    0 0
  34. John you don't mention in the first paragraph what method (or a reference) for the 5600ppm CO2 in the Ordovician era. Could you give us a heads up on that?

    If you are to accept the new estimates it shouldn't just make us re-appraise the conditions in the Ordovician it should also make us re-appraise the methodology used to derive the 5600ppm estimate. What implication does this have for other theories based on this method?

    As Young says in his 2010 paper while his observations and theory may possibly explain the glaciation period they can't explain the initiation of cooling through the preceeding era's. Based on Young's theory CO2 levels are still too high to explain the initial phase of cooling. This means there are still major holes in this theory.


    Finally I'm not sure that your final statement is totally accurate. Even if Youngs research were correct what we now have are competing theories in what happened during the Ordovian era. As Young aknowledges in the intro to his papers there are even competing theories to explain how the process occured. The science of this period seems to still be under debate, the work of this group may add to our knowledge but doesn't seem to totally re-orientate the field.

    This leads me to my major worry with John's article. While being selective in his choice of time periods, Late Ordovian, ignoring the early and mid periods he is able to make such a strident statement in his last two lines.

    Finally the original estimate of 5600ppm is still out there in the literarture it will take time for the geology profession through further publications, conferences and debate to decide which becomes the accepted best estimates. I don't see this has happened. Simple publication of this paper does not overturn the science.
    0 0
    Response: The 5600 ppm value comes from Royer 2006. In this paper, Royer discusses how the data for CO2 levels over this period is very coarse with poor time resolution. Therefore, there is no contradiction or competition between Young 2010 and Royer 2006 - Young 2010 is filling in the gaps.
  35. 19.dhogaza at 02:16 AM on 13 March, 2010

    Your wrong Young is far from clear when the whole of the ordovian period is analysed.

    Here is a graph showing SST



    My reading of Young is he is completely unable to explain the temp drop from 490-460 mya when CO2 levels remained high (above 5000ppm).

    To paraphrase you. This picture clearly can't explain the first half of the Ordovian?
    0 0
  36. J.C. - {But unfortunately this process occurs over geological periods - over periods of thousands of years or greater. The process is way too small to offset our CO2 emissions (some hard numbers would be nice - can anyone help here?) So rock weathering is not a magic bullet that will save us from ourselves. However, there is research into accelerating rock weathering process as a way of sequestering CO2.}

    I like Prof. Dyson's idea about genetically engineering carbon eating trees!
    0 0
  37. Mikemcc and Tenney Naumer

    Thank you both for responding.

    Mikemcc first, you said....

    Ok Miekol,

    I'm assuming that your tongue is firmly in your cheek, but I'll bite anyway.

    What cost would you put on this mammoth re-building task? Is it likely to go ahead for the inhabitants of the Maldives, Seychelles, Bangladesh, Micronesia? What highlands do those people have. Each time Bangladesh floods 100s die, thousands suffer from epidemics from contaminated water and millions are made homeless.

    What happens when rainfall patterns are disrupted causing problems for food growers, or when plants are ready for pollination too early for the insects that traditionally pollinate them?

    ********************************************************
    Yes Mikemcc you did read me correctly, i did have my tongue in cheek but only lightly not firmly :-)

    Firstly get use to idea that no matter what we do the climate is going to change. Its alway has and always will. Better we persue increasing the worlds wealth and more evenly share it, not condemn the 3rd world to permanent poverty and cause much of the 1st world to join them.

    Yes it can go ahead for the Maldives and others. All it needs is the will. The will to create greater wealth and to plan the necessary construction required.

    Google .... Globalism World of Plenty

    miekol@bigpond.com

    Cheers Michael Smith

    *******************************************************

    Tenney Naumer , you said...

    Miekol conveniently forgets the increasing acidification of the ocean's and its consequent destruction of aquatic life.

    We can't survive with dead oceans.

    *******************************************************
    Tenney, please supply me a link regarding the increasing acidification of the ocean's and its consequent destruction of aquatic life.

    I recall reading an article that the atmosphere has contained 10 times the current level of CO2 in the past, and aquatic life must have survived, its still with us.

    Google ... Globalism World of Plenty

    miekol@bigpond.com

    Cheers Michael Smith


    *******************************************************
    0 0
  38. HumanityRules - what is the source of your graphic?

    Hopefully you realize that the thrust of the two new papers is that earlier reconstructions don't have sufficient resolution to determine what happened during the timescales of actual glaciation.

    Showing a graph of low-resolutions won't rebut the newer papers.

    So, really, the provenance of the graph is crucial.

    Thus far, you've posted a random graph hosted by arstechnica (good enough at what they do, which is not science) without provenance, and saying "nya nya proves published papers wrong!"

    I could draw and post any graph I choose here and say the same.

    You don't refute published work by showing a cute graph with no provenance provided, sorry. Just doesn't work that way.

    Oh, and your green line is labeled "biodiversity", what does that have to do with geological weathering causing sequestration of CO2???????????????????????????????????????????????????????
    0 0
  39. Did John Cook omit some relevant papers from C.R Scotese, R.A. Berner, R. Lindzen and others?

    It appears that CO2 concentrations were very high in the Ordovician with comparatively little variation and yet the temperature swung from hot (no ice at either pole) to cold (extensive glaciation) and then back to hot again. Hardly a ringing endorsement for the canard that CO2 drives global temperatures.

    My understanding is that CO2 concentrations were in the range 4,000 to 6,000 ppm for the entire Ordovician period. Given that the radiation forcing due to CO2 follows a logarithmic relationship one would not expect variations in this range to have a significant effect on radiation capture. Once you have captured 95% of the outgoing energy in the 15-16 micron bands the remaining 5% won't make any noticeable difference. To claim that CO2 caused the wild temperature swings in the Ordovician fails the sanity test.

    Ned (#20), are you saying that CO2 in the atmosphere does not matter unless it is caused by humans? Sorry, if there is any illogical argument going on here it is not from Arkadiusz Semczysza.
    0 0
  40. Since 3000 parts per million CO2 (as compared to 389 parts per million today) apparently sufficed to initiate glaciation, what are projected CO2 levels over what time scale using a 'business as usual' scenario?

    In short, do we envisage an anthropogenic CO2 and other greenhouse gas 'hockey stick' as opposed to 'just' a temperature hockey stick? And what would be the time scale for such projections? I note the comment from John as quoted by Leo G @ 36 - do we know of any other negative feedback loops apart from acceleration of rock weathering? Incidentally, I recall reading about proposals for geosequestration of CO2.

    As matters stand, Ordovician CO2 levels were more than eight times higher than today's.

    I ask because people tend to resist making changes when not faced with immediate profits, costs, or like consequences. Moreover, we find it very difficult to consider consequences extending beyond our lifetimes (and perhaps our immediate offspring's').

    Even so, I'm not totally pessimistic about our species' prospects for survival - our capacity for foresight (ie, respond to future consequences) is part of our remarkable adaptability. The problem lies in our inability to agree on future consequences.
    0 0
  41. gallopingcamel writes: Ned (#20), are you saying that CO2 in the atmosphere does not matter unless it is caused by humans? Sorry, if there is any illogical argument going on here it is not from Arkadiusz Semczysza.

    That's not even remotely what I said in that comment. How on earth did you take that message? Please go back and re-read my comment, more closely. Do you see the four papers I link to? Every one of them is about a time (or times) in the Earth's history when CO2 levels increased and the planet then warmed in response.

    It's mind-boggling that you could be so confused about what was written in fairly clear words. (If English isn't your first language, I apologize.)
    0 0
  42. I see Chris Canaris and others up-thread alluding to the average levels of CO2 in the Ordovician, which were much higher than today's. Even the new estimates (~3000 ppm) for the late Ordovician are, as Chris points out, about 8 times the current concentration. What's up?

    As John Cook mentions in the very first paragraph of this post, the sun has been getting brighter over time. While the largest variations in total solar irradiance in recent decades have been around 0.1%, over the lifetime of the Earth the Sun's brightness has increased something like 25-30%.

    So, with a Sun that was much, much dimmer than today, life (and liquid water) could only exist on Earth in the Paleozoic with much higher levels of CO2. Likewise, a drop in CO2 to levels that seem high today was enough to produce glaciation. See the "faint early Sun" paradox.
    0 0
  43. "Strontium is produced by rock weathering, the process that removes CO2 from the air. "

    Current deforestration is causing soils to wash away and exposing large areas of fresh rocks in the tropics to the atmosphere. This increaes the rate of rock weathering and therefore c02 is also being removed from the air at greater rates due to current deforestation. Never heard this mentioned from pro AGW advocates.


    "Consequently, the ratio of strontium isotopes can be used to determine how quickly rock weathering removed CO2 from the atmosphere in the past. "

    Unfortunately, Sr isotope ratios are also affected by amount/type of volcanism, so the correlation is not perfect.

    "Using strontium levels, Young determined that during the late Ordovician, rock weathering was at high levels while volcanic activity, which adds CO2 to the atmosphere, dropped."

    It is well known that a vast belt of subduction -related increase in volcanism occurred fromn the middle to late ordovician from the stratigraphic record, so the inference of reduced volcanism based on Sr ratios above is wrong.

    "This led to CO2 levels falling below 3000 parts per million which was low enough to initiate glaciation - the growing of ice sheets".

    This is an inferance based on chicken and egg arguments, c02 could have dropped because ocean temperatures dropped first, causing increased solubility of c02, not the other way around. This is why c02 rises and drops throughout geological hitory,it follows ocean temperatures (eg recent glacial/interglacials) rarely the other way around.

    "Young 2009 - CO2 levels dropped at the same time that sea surface temperatures dropped". As expected from the above, and consistent throughout the geological record and from simple chemistry. The resolution from Young 2009 is not sufficient to determine cause and effect, however the resolution from recent ice ages is, and they show c02 closely follows ocean temperatures.

    Your conclusion that c02 within the ordovocian is consisent with c02 as a strong dirver of climate is academic gymnastics. No such conclusion can be made from the data.
    0 0
  44. thingadonta writes: "Current deforestration is causing soils to wash away and exposing large areas of fresh rocks in the tropics to the atmosphere. This increaes the rate of rock weathering and therefore c02 is also being removed from the air at greater rates due to current deforestation. Never heard this mentioned from pro AGW advocates."

    That's because (a) the timescales are too short so far, and (b) it's counteracted by much faster releases of stored carbon into the atmosphere from fossil fuels and land use change.

    If you kept up our increased rate of weathering for the very long-term future, and eliminated our fossil-fuel and land use CO2 fluxes, then yes, the CO2 concentration in the atmosphere would begin to decline.
    0 0
  45. As offered last night - here are some notes about Tertiary-Recent weathering of lead-bearing lodes in Central Wales - a little O/T but it's interesting to see what weathering can do:

    There is compelling evidence for two separate phases of supergene alteration of galena in the metalliferous veins (upper Palaeozoic Pb-Pb ages) of Central Wales. Firstly, deep sub-tropical leaching in Tertiary times resulted in the formation of large quantities of oxidation products occurring as coarsely-crystalline masses with consistent, highly evolved parageneses (cerussite - PbCO3 - overgrowing uncorroded pyromorphite - Pb(PO4)3Cl) and indicative of a system which is relatively evolved and where there has been time to reach a point very close to chemical equilibrium. Strong bleaching of the normally dark grey late Ordovician to early Silurian turbidite wallrocks to pinkish or buff-yellowish colours is a frequent observation in association with this assemblage.

    Glacial erosion, that in some cases has left fresh sulphides (including minerals, such as marcasite, that are particularly unstable) today exposed at the surface along the sides of U-shaped valleys, must have physically removed the evolved supergene assemblage from many lodes, exposing new horizons at which supergene chemical processes once again began to operate. This scenario produced microcrystalline secondary minerals (this time without obvious wallrock bleaching), again in a well-defined paragenesis, but in this case reversed i.e. pyromorphite overgrows corroded cerussite in a system that is clearly some way from approaching equilibrium.

    The source of the phosphate in the coarse-grained assemblage is likely explained by the consistent spatial link between such mineralisation and severely-leached turbidite wallrocks. In these strata, phosphatic concretions and phosphate-rich hemipelagites are common. Although carbonate, both from dissolved CO2 in meteoric water and leached from the wallrocks and hypogene vein carbonates, would also have been readily available, in the presence of the enhanced phosphate concentrations in the fluids low down in the supergene zone, pyromorphite would appear first in the final paragenesis.

    The overgrowth, in the coarsely crystalline supergene assemblage, of pyromorphite by cerussite, presents an interesting problem. The underlying pyromorphite shows no signs of corrosion during this process, so there is no question of destabilisation of pyromorphite. Most likely, following the thorough leaching of the wallrocks, the available phosphate supply literally dried up, so that the supergene system defaulted back to a meteoric carbonate-dominated process causing cerussite to precipitate.

    In the close-to-surface, post-Quaternary microcrystalline assemblage, the carbonate activity in meteoric water is clearly sufficient for the first stage of alteration of galena to be to cerussite. Regular flushing with rainwater, which would have little time to leach phosphate from the surrounding rocks, but already be in equilibrium with CO2 in the atmosphere would ensure that galena altered to cerussite. Over time, however, in the presence of even small amounts of phosphate in solution pyromorphite would eventually replace cerussite simply due to the relative solubilities of the two minerals. In other words, if phosphate is available, the more stable pyromorphite will invariably form.


    Mason, J.S. 2004. The development and preservation of supergene lead mineralisation in Central Wales. UK Journal of Mines and Minerals, 24, 35-46.
    0 0
  46. Should have added.... the pervasive leaching that led to the bleached wall-rocks clearly took a very long time indeed.... in post-glacial times the lead-bearing lodes have had ~12,000 years worth of weathering but with only modest results.
    0 0
  47. Thanks for pointing out the reference to the lower Ordovician insolation. I chased up the reference to the Royer 2006 paper - sorry but I haven't yet mastered the hyperlinks. However, it says:

    ‘Global climate models calibrated to mid-Cenozoic conditions suggest a threshold of 560–1120 ppm (DeConto and Pollard, 2003; Pollard and DeConto, 2005), however during the Late Ordovician surface conditions were different, most notably in having an ~4% lower solar constant. A consequence of this decreased luminosity is that if all other thermal forcings were held constant, the CO2 threshold for initiating glaciations would be higher.’

    I guess we are not that far away from 560 ppm, which could be a worry.

    However, how does this 4% lower insolation compare with insolation as per the Maunder Minimum? The thread ‘What would happen if the sun fell to Maunder Minimum levels?’ started on 19/02/10 argues inter alia for the very weak influence of solar forcing. The use of very different units - percentages as per Royer and Watts/M2 in the Maunder Minimum thread - makes it difficult to know how much weight to give the 4% insolation figure.
    0 0
    Response: This is very rough figures, eyeballing the numbers from a Maunder Minimum graph and yes, I'm aware the eyeballing does not constitute scientific proof. But the difference in solar output from the Maunder Minimum (around 1364.7 W/m2) to the solar maximum in the late 20th Century (around 1366 W/m2)  is roughly 0.1%.
  48. We should probably keep in mind that there is only so far that climates can be compared between vastly different geological eras.

    Our current glaciation/deglaciation cycles apply to continents and, more importantly, oceans as they are configured today.
    http://www.whoi.edu/oceanus/viewArticle.do?id=2508

    Under different conditions, especially different oceanic circulations, tresholds for climatic regime changes would likely be different.

    So, really, what should preoccupy us is how different our current CO2 levels are from anything seen during the whole glaciation/deglaciation record of the past few hundred thousand years.
    0 0
  49. Current deforestration is causing soils to wash away and exposing large areas of fresh rocks in the tropics to the atmosphere. This increaes the rate of rock weathering and therefore c02 is also being removed from the air at greater rates due to current deforestation. Never heard this mentioned from pro AGW advocates.

    Thingadonta ... as regards global warming per se, we don't need to understand the carbon cycle. We *measure* the rate of increase of CO2 directly, and we have quite solid figures on how much CO2 we spew into the atmosphere. The difference between the two tells us that carbon sinks take up about half of the CO2 we emit, and apparently that relationship's been quite constant for decades.

    I'm not saying that people don't study the carbon cycle, it's a hot area of research, primarily because of interest in what happens in the future. Will sinks continue to absorb CO2 at the same rate? Faster? Slower? Plus just the general curiousity that science brings to the study of the world - we should know precisely how the carbon cycle works because it's our species' nature to try to understand questions of this sort.

    So there's lots of work going on in the area under the umbrella of research related to climate change, and of course a lot is known, i.e. the amount of CO2 absorbed by the oceans, etc.

    But it's just not terribly relevant to the broader discussion of CO2-forced global warming. CO2 goes up by a measured rate, sensitivity lies between 2.5-4C, so we can expect a range of warming in the future, the significance of which depends on the actual sensitivity. Narrowing the uncertainty of sensitivity is more crucial for policy then the understanding the full details of the carbon cycle, along with things like sea level rise and other impacts.
    0 0
  50. One of the main points of this post is that our understanding of temperature and CO2 levels over the past few million years has evolved and become much more detailed over the past few years. As we look more closely at new higher resolution data we find that the linkage between temperature and CO2 is very tight, and it seems previous ideas about high temperatures concurrent with low CO2 levels were based on incorrect interpolations over huge geological time periods. We also find that some other higher estimates of ancient CO2 levels need to be revised. For example the 2010 paper by Breecker reports “Atmospheric CO2 concentrations during ancient greenhouse climates were similar to those predicted for A.D. 2100”. It appears that for paleosols, (fossil soils, one of the main proxy sources for estimating ancient CO2 levels) previously assumed soil CO2 concentrations during carbonate formation were far too high (by factors of around 2 or more). If this is taken into account it follows that ancient climates did not involve variations of 1,000s of ppmV of CO2, and past greenhouse climates were accompanied by concentrations similar to those currently projected for A.D. 2100. In addition the corrected paleosol record agrees more closely with other independent proxy paleo-evidence (such as that from fossil plant stomata) which adds confidence in both results. Obviously this gives some perspective on current rising levels of CO2 and temperature.

    Breeckers work has been commented on by Dana Royer in 2010, Fossil soils constrain ancient climate sensitivity . Here she follows up on estimates of CO2 sensitivity up on her earlier work summarized graphically (2009) in Climate Sensitivity during the Phanerozoic: Lessons for the Future . This shows that recent revisions of climate sensitivity (change of temperature due to doubling of CO2) derived from paleo records have been converging on values around 3 degrees C.

    Some have asked about CO2 rise preceding temperature rises in the past, and to add to what Ned at 02:18 AM on 13 March, 2010 has listed:

    “The Paleocene-Eocene Thermal Maximum (PETM) occurred approximately 55 million years ago, and is one of the most dramatic abrupt global warming events in the geological record. This warming was triggered by the sudden release of thousands of gigatons of carbon into the atmosphere and is widely perceived to be the best analogue for current anthropogenic climate change” This is quoted from Productivity feedback did not terminate the PETM Torfstein 2009. It has also been argued in Carbon dioxide forcing alone insufficient to explain PETM warming. (Zeebe 2009) that either current estimates of climate sensitivity are underestimates (as Breeckers work suggests), or that other positive feedbacks or causes are operating. In Ocean chemistry and atmospheric CO2 sensitivity to carbon perturbations throughout the Cenozoic (2010) Stuecker and Zeebe add that recent work indicates an increased sensitivity to carbon cycle perturbations and state “we expect much more severe effects in the near future than during the PETM because of the likely higher anthropogenic release rate (even at the same total carbon input)”.
    There is also earlier evidence (120 million years ago) of dramatic negative consequences of rapid increases in CO2 from Méhay 2009, “A volcanic CO2 pulse triggered the Cretaceous Oceanic Anoxic Event 1a and a biocalcification crisis”.

    We must also appreciate (as John pointed out) that the gradual increase in solar output over the past 4 billion years (which we can estimate from looking at similar stars at various stages in their evolution) is likely to lower the threshold of CO2 levels at which the transition between glacial (we still have ice caps on Greenland and Antarctica, as well as the Himalayas) and essentially ice free conditions will occur, as well as other temperature sensitive thresholds or tipping points.

    The link between glaciation (obviously related to temperature) and CO2 levels, and the effects of positive feedback, lags, etc are covered comprehensively in the scientific literature, but I list some recent work Flower 2009 ,
    Langebroek 2009, (for middle Miocene, 13.9 million years ago)
    Tripati 2009 (covering the past 20 million years), Westerhold 2009 “the crossing of a critical pCO2 threshold may have led to the formation of the first ephemeral ice sheet on Antarctica as early as_50 Ma ago”

    None of this work precludes other drivers (lesser or greater) for global temperature and climate, and in geological history as well as now, other factors must be taken into account (such as insolation, plate tectonics, etc) but the weight of evidence for rising/falling CO2 levels being a significant cause as well as an effect of temperature rising/falling is overwhelming and increasing, and explanations for climate change which do not include CO2 have so far either been falsified or have been diminished in significance due to conflicting, ambivalent or updated evidence.
    0 0

1  2  Next

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.



The Consensus Project Website

TEXTBOOK

THE ESCALATOR

(free to republish)

THE DEBUNKING HANDBOOK

BOOK NOW AVAILABLE

The Scientific Guide to
Global Warming Skepticism

Smartphone Apps

iPhone
Android
Nokia

© Copyright 2014 John Cook
Home | Links | Translations | About Us | Contact Us