Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Relationship between CO2 and Global Warming

  1. is the primary driver

    0 vote(s)
  2. is an important factor

    9 vote(s)
  3. There is only a weak correlation, if at all

    6 vote(s)
  4. Global temperature is the driver of CO2

    2 vote(s)
Multiple votes are allowed.
  1. Jul 21, 2005 #1
    The vote of the majority may say more about the convincing power of the ideas than provide an good understanding of the reality. But what do we think?
    Last edited: Jul 21, 2005
  2. jcsd
  3. Jul 21, 2005 #2
    If CO2 is not the cause of the recently observed warming then what is?
  4. Jul 21, 2005 #3
    Century-millenium scale oceanic oscillations?
    Decadal atmospheric oscillations?
    Interacting oscillations all in warm phase currently?
    Solar activity, influencing cosmogenic condensing nucei?
    land albedo changes due to changed land use?
    Oceanic albedo changes (algae) due to anthropogenic disturbing of the food chains?
    Airliner water vapour emission in the stratosphere?
    Soot, haze?

    I found http://segovia.mit.edu/publications/2002/sretoc.pdf [Broken] interesting.
    Last edited by a moderator: May 2, 2017
  5. Jul 21, 2005 #4
    Century-millenium scale oceanic oscillations? - Far, Far, Far, to slow to account for the current warming.

    Decadal atmospheric oscillations? - Why not apparent in the past? You'd need to tie it in with the next one* to make a workable hypothesis.

    Interacting oscillations all in warm phase currently?* - Good one!! EXTREMELY difficult to disprove. But by the same token extremely difficult to prove. Occams Razor >> We have a mechanism that will increase net global energy balance - CO2 forcing. So I'll be sticking with that until this alternate is proven.

    Solar activity, influencing cosmogenic condensing nucei? - Do you mean Vizier? I thought that work had been withdrawn. In any case would not a 11 year climatic cycle be apparent in our climate if it were so sensitive to solar flux variation. Furthermore I'd thought that there was no evidence of a significant* trend in solar energy flux. (*i.e. a significant proporation as compared to the 11 years sunspot cycle - were a long term trend less than the sunspot cycle it'd be less apparent than the sunspot cycle).

    land albedo changes due to changed land use? - Warming from gound up, so how can this explain the strato cooling. And would it account for polar amplification? Most of the earth is ocean, and were such massive albedo to blame then it should be apparent from sattelite measurements.

    Oceanic albedo changes (algae) due to anthropogenic disturbing of the food chains? - Again from the surface up heating, stratospheric cooling should not be an indicator. How massive would this need to be for even a 0.5 degC global temp increase? I've never heard of evidence for this. Once again albedo should be apparent with the technology available.

    Airliner water vapour emission in the stratosphere? - This should be apparent by a shift in the lapse rate, i.e. a particular layer sources the heating would mess up the exisitng profile. In any case following 9/11 aircraft were grounded and a study showed a warming, not a cooling. Implying that aircraft contribute to cooling by increasing albedo, not to warming.

    Soot, haze? Again increase in albedo, not a warming issue. And as areas such as Europe and US have cleaned up their air quality in the latter part of 20th century, why have we not seen a net cooling?

    Thanks Andre, I'll stick with CO2, causing a net increase in global energy balance and amplified by water vapour. Off now, will reply tomorrow.
  6. Jul 21, 2005 #5
    But the cumulative feedback is negative :yuck: which James Lovelock could have predicted :biggrin: :

    Some examples of negative feedback in the Earth climate system, Olavi Kärner

  7. Jul 21, 2005 #6
    Water vapor is a strong infrared absorber and is extremely abundent as pointed out.

    I vote for H20.

    Edit: Cosmic rays can seed cloud formation. Condensed clouds are much
    more effective at absorbing IR than the concentration of CO2 which we
    have. Solar and Extrasolar events probably underlie our global thermal
    epochs, not backyard barbecues, cattle and the unfortuante burning of
    our limited oil resources.
    Last edited: Jul 21, 2005
  8. Jul 22, 2005 #7
    Hi Andre,

    If H2O does not amplify the small CO2 warming then the models must be wrong. In that case how do you account for http://www.gfdl.noaa.gov/reference/bibliography/2002/soden0201.pdf [Broken]

    Hi Antiphon,

    To the best of my knowledge there is no major ongoing trend in cosmic rays that would account for the observed warming trend. Do you have such infor?

    Again I refer you to my point regarding the 11 year solar cycle. Why, if the sun is causing the recent warming does the climate not exihibit an 11 year cycle. After all the 11 year cycle is far greater than and +/- trend in solar radiation (agin to the best of my knowledge - but I could be wrong!)
    Last edited by a moderator: May 2, 2017
  9. Jul 22, 2005 #8
    As always the caveats are hidden somewhere:

    Now it happens to be the scholar view that volcanic aerosols do act as condensation nuclei, increasing the cloud cover.

    http://www.open.ou.nl/dja/Klimaat/System/crucial_role_of_aerosols_a.htm [Broken]
    http://www.newmediastudio.org/DataDiscovery/Aero_Ed_Center/Category/A_sulfate.html [Broken]

    But not a single reference to that process.

    Well, nice try.
    Last edited by a moderator: May 2, 2017
  10. Jul 22, 2005 #9
    "Well, nice try." Ditto Andre, you've missed the point...

    You selectively quoted:

    "Although it is possible that other processes, such as clouds, could act in place of water vapor to provide the strong positive feedback necessary to amplify the cooling..."

    This is where you left it. But this paper is about water vapour and the model's ability to correct the predict level of water vapour given that Clausius-Capeyron only specifies an upper limit, and that the process that govern relative humidity have uncertainty associated with them.

    So here's the penultimate para in full.

    "To reproduce the observed temperature record after the eruption of Mount Pinatubo,
    the model requires a strong positive feedback, equivalent in magnitude to that predicted for water vapor. Although it is possible that other processes, such as clouds, could act in place of water vapor to provide the strong positive feedback necessary to amplify the cooling, (but this time let's finish that statement) the observational evidence clearly indicates a reduction in water vapor that is consistent with the model predictions."

    i.e. the model is able to reproduce the water vapour levels due to a well observed global temperature change event. So the doubts that some express about CO2 amplification by water vapour, are looking a bit less founded. What actually caused the change is secondary, the correct prediction of the water vapour response is the key issue.
  11. Jul 22, 2005 #10
    Actually Andre, to be fair I should own up that you nearly got me there. Whilst trawling around for data of the strato and tropo residence times for Pinatubo's suphate aerosols (which bear out your contention re the duration of cooling) I realised that wasn't the issue, a kick-self moment for me there! I should have been more specific as to why I'd posted the link to Soden, it wasn't a deliberate trap - just me being vague. :)
  12. Jul 22, 2005 #11
    I think not that I missed the point being:

    Now, nowhere in the article the authers acknowlegde the role of aerosols (notably sulphates) in providing condensation nuclei. More aerosols, more clouds? They don't account for that in the model.
  13. Jul 22, 2005 #12
    Last edited by a moderator: Apr 21, 2017
  14. Jul 22, 2005 #13
    To quote from the final para of the study. "We note, however, that Mount Pinatubo does not provide a perfect proxy for global warming, because the nature of the external radiative forcing obviously differs between the two. Nevertheless, the
    results described here provide key evidence of the reliability of water vapor feedback predicted by current climate models in response to a global perturbation in the radiative energy balance."

    What Soden was doing was trying to demonstrate only that the models showed a good correlation with the observed levels of water vapour.

    The aerosol induced increase in atmospheric albedo is the driving force that causes the change in water vapour that THEN amplifies the initial change in radiative forcing. That aerosols lead to the global decrease in temperature is not in any doubt. But being able to show that the models can replicate the change of water vapour is crucial for demonstrating the underlying model behaviour that leads to projections amplifying the initial positive forcing of anthropogenic CO2. As water has a short residency time, 10 days or so in the troposphere, it's not a forcing but a feedback.

    I accept that there may be some effects of cloud that are not understood, the conflicting work of Richard Lindzen and Big Lin throws some interesting light on this. (Iris Hypothesis). BUT that is not the main issue being investigated here. It's the relationship between forcing and it's effect on temperature on a global scale, and the subsequent impact of temperature on water vapour concentration.

    Off for the weekend now, will reply on Monday
  15. Jul 25, 2005 #14
    You left out the terracalories of heat generated by human activity. Some human technology operates at temperatures over twice the temperature of the air as measured in degrees Kelvin. The internal combustion engine operates above the boiling point of water. The catalytic converter can be hot enough to start fires in dry grass.

    That heat has to go somewhere and the air is a ready absorber of heat.

    I have heard that it is actually low temperatures that are increasing. If that is the case a likely cause would be an increase in the water vapor content of the air(which can result from combustion of hyrdrogen containing fuels or increasing evaporation of surface water) which places a floor under air temperature. The water vapor content sets the dew point which normally is the lowest temperature air at the surface can fall to.

    Changes in heat circulation are another potential factor considering that the main change seems to be in temperatures in the northern areas of the northern hemisphere.
    Last edited by a moderator: May 2, 2017
  16. Jul 25, 2005 #15
    If one area, of the atmosphere or surface areas, is warming and another cooling it would be likely that changes in heat distribution rather than net warming is occurring.

    I have yet to see any numbers indicating that it is possible for CO2 to generate the necessary 500 to 700 calories per gram necessary to heat the atmosphere. CO2 only absorbs a narrow band of IR that is not widely produced.
  17. Jul 25, 2005 #16


    User Avatar
    Gold Member

    Im not even going to pretend i know whats the real science behind the global warming issue
  18. Jul 25, 2005 #17
    Yes that's correct. We did the calc's on that and it turned out to be negliglible. Besides we're focussing on CO2 here. There can be another anthropogenic cause indeed like the change in water vapor and cloud cover.
  19. Jul 25, 2005 #18
    Hi Reasonmclaus,

    "If one area, of the atmosphere or surface areas, is warming and another cooling it would be likely that changes in heat distribution rather than net warming is occurring. "

    I don't quite get what you're getting at here. The global average temp is increasing. CO2 will increase the net energy of the Earth and then this minimal net energy increase (warming) will increase humdity (water vapour concentration) thus increasing the 'greenhouse' capture of heat. Thus the globe warms on average.

    "I have yet to see any numbers indicating that it is possible for CO2 to generate the necessary 500 to 700 calories per gram necessary to heat the atmosphere. CO2 only absorbs a narrow band of IR that is not widely produced."

    See IPCC Third Assesment Report Part 6 (I think), there's a table which contains the equations used to account for the increasing saturation of absorption bands as CO2 concentration increases. CO2 increases from current atmospheric concentrations are still able to increase absorbed energy.

    PS http://www.gfdl.noaa.gov/reference/...2/soden0201.pdf [Broken] demonstrates the ability of models to correctly reproduce water vapour levels under changes of forcing. Thus the models can be viewed as more robust in their projections of water vapour amplification of CO2 driven warming.
    Last edited by a moderator: May 2, 2017
  20. Jul 25, 2005 #19
  21. Jul 26, 2005 #20

    Try the following:


    http://science.msfc.nasa.gov/ssl/pad/solar/sunspots.htm [Broken]

    I believe the following requires AAAS membership for access.

    Last edited by a moderator: May 2, 2017
  22. Jul 26, 2005 #21
    The global average temp is mathematically worthless. It is derived by adding only the high and low temperatures which may not be representative of temperatures for an entire 24-hr period. Any average temperature should use temperatures taken at specific intervals during the day, preferably at 10 minute intervals or less. The figures for global changes indicate only a .5 C change during the 20th Century which translates to about a .16% change(the per centage has to be determined using the Kelvin scale to avoid the abritrary "0" point of the C and F scales.)

    the amount of water vapor in the air exists independently of the amount of CO2. Combustion of hydrogen containing fuels and variations in evaportation rate(which is affected by the amount of water not covered by ice among other factors) affect the amount of water entering the atmosphere. Variations in particles upon which water can condense to form water droplets affect the amount of water leaving the atmosphere. Water will condense on solids with temperatures below the dew point.

    Does the assessment include actual measurement of the energy in the radiation CO2 absorbs along with experimental data showing that CO2 in fact generates heat that is transmitted to other atoms? Science is based on verification through expermentation and observation. Even Einstein's theories have been tested with actual observations when possible.

    The link doesn't work.
    Last edited by a moderator: May 2, 2017
  23. Jul 26, 2005 #22
    Sorry the link should be http://www.gfdl.noaa.gov/reference/bibliography/2002/soden0201.pdf [Broken]) That should work.

    I'm not sure exactly how the 3 equations given in table 6.2 or chapter 6 of the IPCC Third Assesment Report are produced. However that's where they're listed. And I have no reason to doubt them. They are, after all, in IPCC TAR.
    Last edited by a moderator: May 2, 2017
  24. Jul 26, 2005 #23
    Hi Reasonmclucus, (got the name right this time)

    "The global average temp is mathematically worthless. " Do you mean mathematically or realistically? I really don't know where to start here. Obviously the temperature of an object can be determined by taking mean temperatures and averaging. As to the time of day issue, I don't know how exactly met stations do their work. But we have sondes, ground stations, and satelite all showing a warming. Furthermore this warming appears to be backed up by the pattern of glacial retreat at altitude in the tropics and temperate lattitudes, for just one observation. So that suggests that the measured increase is, at least in trend real.

    "the amount of water vapor in the air exists independently of the amount of CO2. " Correct, but CO2 in the atmosphere increases temperature and THAT is what increases water vapour level. In Soden et al, it is shown that the models correctly account for changes in water vapour due to the reduction in solar forcing by aerosol driven albedo changes from Mt Pinatubo.

    PS the 2 first links you post to appear to support my contention that Solar activity does not account for the current warming. I can't access the 3rd one, does that stand against what I'm saying?
    Last edited: Jul 26, 2005
  25. Jul 27, 2005 #24

    An average of the numbers in a set needs to represent all the members of the set. Using only a high and low number may distort the result. For example, determining the average age of people living in a census district by only using the ages of the youngest and oldest residents would not guarantee an accurate result.

    In temperature fluctuations, the low or high temperature at any given location might be the same for a long or short period. For example, in summer the overnight temperature might drop slowly reaching a low point just before dawn. In winter the temperature might drop to the dew point within a few hours after sunset and remain there until morning.

    The article you referred to doesn't measure the actual energy being radiated which is necessary to determine if there is sufficient energy to warm anything. If you'll look closely at the graphs, the models only come close in situations of slow gradual change. In situations with fluctuations the models fail with the slopes of the curve moving in different directions. The model may show an upward slope when the actual measurement has a downward slope.

    The main impact of water vapor on atmospheric temperature doesn't involve radiation. Instead in involves the fact that water vapor contains 540 calories of heat per gram that must be released if it condenses. With water's much higher coefficient of heat than air the result is that the condensation of a gram of water vapor releases sufficient heat energy to warm over 2 kg of air by 1 C. This characteristic is the reason the water vapor content of air sets the lowest temperature that the air can fall to called the dew point.
  26. Jul 27, 2005 #25
    So let's investigate that in detail:

    So we compare the temp dip with the average of the previous values. Now let's have a http://home.wanadoo.nl/bijkerk/Pinatoba.JPG [Broken] at the MSU data prio to and after Pinatoba.

    And yes Pinatoba is clearly preceeding a trophosphere temperature dip. No surprise there but we see similar sort of dips in 1982, 1984, 1989. This makes it very clear that without the Pinatoba eruption a similar dip could have occured. So comparing the dip with average values has no meaning as we don't know what the real driver behind this cyclic behavior is. So, we don't know which part of the post-Pinatoba cooling is Pinatoba related and which part is natural cycle. Conclusion, the water vapor feedback is based on very shallow observations and cannot be considered proven.

    And I keep wondering how this kind of papers passes the peer review.

    Data source: http://vortex.nsstc.uah.edu/data/msu/t2lt/tltglhmam_5.1 [Broken]
    Last edited by a moderator: May 2, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook