Comments

1. #1 Luboš Motl

   2007/09/24

   There exist much more robust ways to show that gas concentrations were not the driving force in the relationship, especially the fact that gases are correlated with one another.

   At any rate, you seem to be missing the important event of today, namely the UN summit where the proposal to split the IPCC was finally suggested.

   http://motls.blogspot.com/2007/09/vaclav-klaus-in-united-nations_09.html

   [I think the hat was a Big Mistake. But VK's cliamte science remains as poor as ever - its almost as if he's been reading your blog - and we still await a credible writing down of his "theories". Or perhaps he doesn't care to commit himself in too much detail? -W]

2. #2 SteveF

   2007/09/24

   Thats interesting, good scoop. If CO2 might even be leading (or synchronous), what does that say for the role of Milankovitch in this transition….

   [Not much really. The most plausible scenario is solar change -> t change -> co2 feedback -> more t change. But if you needed it, you could probably manage solar focring -> co2 change (via plant respiration or somesuch) -> t change ... -W]

3. #3 Thomas Palm

   2007/09/24

   The pessimistic view of this is that we have a lot less time before positive CO2 feedbacks get up to speed and accelerate the warming than earlier interpretations of ice core data suggested. (To the extent that the current situation is analogous to what happened then, which is debatable)

   [Could be. +ve feedbacks doesn't feature very highly in anyones analysis of the next 100 years so far, in part because they are so uncertain -W]

4. #4 Luboš Motl

   2007/09/24

   Let me be more specific. CO2 can’t be leading because of additional arguments that don’t depend on the lag. The temperatures are beautifully correlated with CH4, N2O, and other gases as well. If you assume that CO2 (or some mixture of gases) is the primary driver, you wouldn’t be able to explain why CO2 and CH4 are so tightly correlated with each other.

   Thomas Palm about positive feedbacks is also wrong and it has been explained many times. Look at one glaciation cycle. The temperature surely influences the CO2 in some part of the cycle. If the net influence in the opposite direction during the glaciation cycle exceeded the influence of temperature on CO2, then we would deal with a genuine positive-feedback system whose initial perturbations would be increasing exponentially.

   Such a property would cause the system to be unstable, and during 5 billions of the history, the Earth would have already run out of control. Because this hasn’t happened, it follows that the system doesn’t suffer from this kind of instability, and the net influence of gases on temperatures has been smaller than the influence of temperature on the gases.

   To summarize, the ice core data prove that the greenhouse effect was negligible at least during the last 650,000 years.

   [Hi Lubos. Stop and think a moment. You want to say that +ve feedback (or lack of runaway thereof) proves that Co2 doesn't influence T. But you're happy for T to influence CO2, and feel no need to worry about runaways in that direction.

   Why exactly does CO2 top out at 280 (when we're not influenceing it) and bottom at 200 (for the last 400 kyr; a bit different before then?). No-one really knows. We don't pretend to have all the answers by any means. But we have got rid of many of the wrong answers that you cling to -W]

5. #5 Alexander Ac

   2007/09/25

   William,

   as a plant eco-physiologist I am not sure about this: “…you could probably manage solar focring -> co2 change (via plant respiration or somesuch) -> t change ” – why should plant respiration change, if temp. don’t? :-)

   [Because plant CO2 balance probably depends on sunlight -W]

   Once again to my previous question, why do the CO2 “decrease” in cooling world iniciated by orbital changes? Is it the sink capacity of cooler oceans? That’s just because from the physiological point of view, the plant should *add* carbon in the cooling world…

   [I don't think that this is well known. But: the decrease is more likely associated with the oceans rather than land (partly because of what you say and partly because its hard to stuff enough C onto the land). Then you get into changes in up/downwelling, largely in the southern ocean (hurrah!) and maybe also the response of the plankton and other bits. I think people were once enthusiastic about ice age -> drier -> more dust -> ocean fertilisation, but not sure they still are -W]

   BTW, who and how could *misuse* the sentence, that CO2 increase could lead over the temp. increase?
   Sen. Inhofe? :-)

   [Presumably "they haven't got a clue" would be one way to use it -W]

6. #6 Alexander Ac

   2007/09/25

   Lubos,

   why should the correlation of CO2/CH4/NO2 rule out the effect of CO2 on temp.? Is it impossible that CO2/CH4/NO2 increase-decrease is driven by different processes, though these processes have similar relation to temp.? Let’s take modern example – methane release from Siberia driven by warming.

   BTW, I think it’s VK who welcomes the warming of Siberia for fruit planting (in the mud??). ;-)

7. #7 Alexander Ac

   2007/09/25

   I’have just calculated…

   if every person on Earth was average American (i.e. 5 tons of carbon/year), assuming we have 6 billions (we have actually 6.6)- i.e. 30 bil. tons od carbon per year (i.e. 120 bil. tons of CO2) – it is around 10 ppm a year – in 6 years we have 450 ppm CO2. Just interesting…:-/

8. #8 Alexander Ac

   2007/09/25

   Plant Carbon balance is issue complicated just as the issue of climate change ;-) increasing sunlight also increases the carbon assimilation, but still, can you have increased irradiation and const. temp?
   *
   There is much more to say for different ecosystems – e.g. new research says tropics like drought and sunlight, at least in the short-term – unless there is enough water in the soil – e.g. here – http://earthobservatory.nasa.gov/Study/AmazonEVI/amazon_evi.html

   for some the message is clear – more CO2 – greener tropics :-)

9. #9 Luboš Motl

   2007/09/25

   Jesus Christ, William…

   The influence of temperature on concentrations itself cannot cause any runaway behavior. You can only get a runaway behavior if you have influences in both directions, so that the initial perturbation of one quantity X is translated to a much higher increase of the same quantity X later.

   If the influence is essentially only in one direction, it just means that temperature – that was dictated by orbital variations or chaos – also determines the gas concentrations. There is no amplifying feedback here, and it’s my point. If there were a relation in both ways, we would have already seen a runaway behavior.

   The CO2 concentrations seem to stop around 200 and 280 ppm exactly because regulating negative feedbacks were becoming important at 200 or 280 ppm, or because 40 ppm around 240 ppm is simply the natural typical scale of the fluctuations.

   If you allow me to assume the first thing, it is pretty clear that the regulating effects that are sparked at 280 ppm are initiated even more strongly at 385 ppm or higher as long as they depend on CO2. And if they don’t depend on CO2, then CO2 is not too important for the dynamics that starts and ends ice ages and we shouldn’t be spending much time talking about CO2.

   [Holy Moses, Lubos! So you believe in no feedback at all? CO2 has no impact on planetary temperatures? This is an odd thing to believe, practically everyone accepts the natural GHE. Anyway: no-one thinks you can get the observed T changes from orbital forcing alone, the forcing is too small. Your stuff around 200/280 is good handwaving but meaningless.

   A relation both ways - a feedback - doesn't imply a runaway, of course, so all this is chasing strawmen. BTW, does your theory account for the change in CO2 cycles before 400 kyr? -W]

10. #10 Lee

    2007/09/25

    Lubos has made this argument, that positive feedback necessarily means runaway, many times – he seems to actually believe it.

    I find it inconceivable that a Harvard professor of physics has never heard of positive feedback with limited gain – amplifiers, anyone? – but there it is.

11. #11 Magnus W

    2007/09/26

    On the top of my head “plant” growth is manly limited by water and nutrient supply (which partly is effected by global warming). Can’t remember reading anywhere that the ocean have played a major part in global climate change in any other way then equilibriums and sink of carbon shells but that mainly as a type of feedback, not that big… and I guess you all know but usually weathering is the most frequently discussed on longer timescales.

12. #12 maksimovich

    2007/09/28

    “Anyway: no-one thinks you can get the observed T changes from orbital forcing alone, the forcing is too small. Your stuff around 200/280 is good handwaving but meaningless.”

    Not quite no-one.

    “Deep-sea temperatures rose 1,300 years before atmospheric CO2, ruling out the greenhouse gas as driver of meltdown, says study in Science.”

    Carbon dioxide did not cause the end of the last ice age, a new study in Science suggests, contrary to past inferences from ice core records.

    “There has been this continual reference to the correspondence between CO2 and climate change as reflected in ice core records as justification for the role of CO2 in climate change,” said USC geologist Lowell Stott, lead author of the study, slated for advance online publication Sept. 27 in Science Express.

    “You can no longer argue that CO2 alone caused the end of the ice ages.”

    The link between the sun and ice age cycles is not new. The theory of Milankovitch cycles states that periodic changes in Earth’s orbit cause increased summertime sun radiation in the northern hemisphere, which controls ice size.

    However, this study suggests that the pace-keeper of ice sheet growth and retreat lies in the southern hemisphere’s spring rather than the northern hemisphere’s summer.

    http://www.eurekalert.org/pub_releases/2007-09/uosc-cdd092507.php

    [Interesting article, thanks for pointing it out. I shall have a look at Science. But "You can no longer argue that CO2 alone caused the end of the ice ages." is confused - no-one is arguing that anyway. I don't think these people are arguing that all the T comes from orbits, either -W]