A Few Things Ill Considered

A layman's take on the science of Global Warming featuring a guide on How to Talk to a Climate Sceptic.

Sunday, January 29, 2006

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Water Vapor is Almost All of the Greenhouse Effect

(Part of the How to Talk to a Climate Sceptic guide)

This article has moved to ScienceBlogs

It has also been updated and this page is still here only to preserve the original comment thread. Please visit A Few Things Ill Considered there. You may also like to view Painting With Water, Coby Beck's original fine art photography.

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posted by coby @ 1/29/2006 04:20:00 PM  

35 Comments:

  • At March 27, 2006 6:14 PM, Anonymous Anonymous said…

    It's important in this context to compare the atmospheric lifetimes of CO2 and H20. A molecule of water vapor spends about a week in the atmosphere where carbon dioxide can stay in the atmosphere for 5-200 years. Water vapor fluctations are significant but, unlike CO2, they are rapidly precipitated out of the atmosphere. The carbon dioxide that we release into the atmosphere now will be around for your great grandchildren's children.

    Here's a list of the atmospheric lifetimes of various greenhouse gases on the IPCC site
    http://grida.no/climate/ipcc_tar/wg1/016.htm
    and plenty of information about water vapor from the American Geophysical Union.
    http://www.agu.org/sci_soc/mockler.html

     

  • At March 27, 2006 6:55 PM, Blogger coby said…

    Thanks for the links, Aaron. I get into that in the scientists hide water vapor's role article. You correct to bring it up here too.

     

  • At April 01, 2006 11:46 PM, Anonymous Anonymous said…

    Why would "atmospheric lifetimes" be of any importance to global climate dynamics? One H20 molecule drops down in a rain drop, but the other, with identical properties, gets evaporated and is back doing its regular job, re-absorbing or reflecting radiation. You can't tell the difference between the two molecules. Same with CO2. Therefore, your great grandchildern's childeren will continue to see those water and CO2 molecules in the air, still not being able to distinguish which is which.

    However, what you are trying to say is that the effective reaction time of water subsystem to changes in insolation conditions is of the order of 10 days, while the CO2 system reacts in 100 years. So, effectively, the water subsystem is a much better regulating agent in GH condencer, while CO2 is considered as a constant parameter, "forcing", shift. As models (which are just that, approximate models) show, this shift is relatively weak, so it's global importance is questionable, which is quite consistent with historical climate data. What is important (in bigger context) is that 10 days or 100 years scale is still insignificant on the megascale of global glaciation-deglaciation ages, and this is the core of the whole AGW vs. NGW debate.

     

  • At April 02, 2006 1:16 PM, Blogger coby said…

    That's right, "atmospheric lifetimes" are important when discussing the effect of perturbations to the system. Volcanic suplphates can have very string cooling effects but these sulphates only persist for a few years, long enough to lower annually resolved global mean temperature but not long enough to effect multi-decadal trends. H2O perturbations (in the troposphere) last only a matter of days, not long enough to show up on any climate indicators at all. CO2 lasts decades to centuries and this is long enough to cause persiitent trends and long enough to cause sea ice feedbacks and also ice sheet feedbacks.

    What models show a relatively weak shift? We need to define what you mean by weak. A recent Science paper by Annan et al. has placed the climate's sensitivity to 2x CO2 at 3oC +/-1.5 with a 95% probability it is less than 4.5oC. This was a statistical treatment of a wide variety of models.

    I question by what metric you place greater importance on 100K yr timescale changes than those we and our children and grandchildren will have to live through. Even so, if, as seems very likely, CO2 forcing persists long and strong enough to melt significant ice sheets like Greenland, West Antarctica and some or eventually all of East Antarctica, then we will have disrupted that timescale. This may be the ending of this multi-million year old ice age.

     

  • At April 02, 2006 11:17 PM, Anonymous Anonymous said…

    No, that's not right. I just told you that the paradigm of "atmospheric lifetime" sends a wrong message about what is important, and what is not. I reiterate: H2O acts like a fast feedback agent in the self-regulatory climate system, adjusting temperatures in responses to small shifts caused by trace gases and other slower parameters. The H2O is not something like unwanted "perturbation", it actually regulates our life, and that's very important.

    About the shifts, it has to be seen how big or small they are. Averaging models that are likely all wrong does not make any better estimations of our reality. Calibrating models on allegedly "stable" LGM ("last glacial maximum") is a clear absurd - any maximum is locally flat over appropriate (narrow) timespan, and that does not mean that the system was not in a heavy dynamical swing, which will make all "response" equations substantially different.

    What metrics I am using by placing greater importance on 100ky cycles? Simple: the fact of existence of 100ky cycles and lack of their explanation within current models is an indication that the real global climate dynamics is not consistent with current "informed prior believes" of most vocal environmental scientists. According to historical data, the global climate dynamics is more consistent with a motion on a self-sustained quasi-periodic attractor, obviously with "rich dynamics", and regardless whether it might be weakly syncronized with Minakovic forcing or not. "Response equations" (if you wish) on those attractors are different from response equations near simple equilibriums; therefore, all current "linear sensitivity" models are likely severely deficient, and cannot be used for any forecast purposes.

    That's why the 100ky issue is critically important in understanding of what the result of a small CO2 perturbation is: in systems with rich dynamics, the direction of system trajectory may not obviously follow the direction of perturbation, it could be quite opposite. For example, Vostok ice core data revealed that the CO2 concentrations continue to raise at the end of deglaciation cycles while the global temperatures already peaked out and are on a global tendency to decline into new ice age. So, without a correct global model, you never know. That is my point.

     

  • At April 03, 2006 1:19 PM, Blogger coby said…

    "No, that's not right. I just told you that the paradigm of "atmospheric lifetime" sends a wrong message about what is important, and what is not."

    Alexi, you're arguing instead of listening. The topic of this page is the role of water vapor in climate. A commenter brought up the issue of H2O's role in climate change. In this context, atmospheric lifetimes of gases and particulates are important for the reasons I have already stated. There is no contradiction between that and what you mention about the speed of feedback response, which I quite agree is also important.

    I will not claim any high degree of certainty about what the very long term (ie 100K-1m yr)response of our disturbance will be, I only will repeat that it is not important from a socio-political point of view. That timeframe is centuries to millenia and I believe we can predict this timeframe with considerably more confidence.

     

  • At April 03, 2006 11:30 PM, Anonymous Anonymous said…

    I'm sorry, but I would submit that the points I tried to make have obviously escaped your attention. Again, the role of water wapor is to regulate, and regulate fast, with a high-gain feedback loop, which means precise positioning (in temperature) according to general concepts of control theory. The contradiction is that this is the fundamentally-important role, and the paradigm of "lifetime" is just silly and irrelevant to this main function. In short, water vapor is the dominant agent in climate formation.

    About importance of correct 100ky models, again, it does not seem that you really made any effort to follow my point. Again, the linear forcings and feedbacks in current models are perturbations near a WRONG STATE. This initial state is not an equilibrium, but something non-stationary, something cycling nonlinearly along those 100ky orbits, in continuous trends and disbalances. You cannot get right parameters for approaching a state which does not exist. It is not about 100,000-year response time, it is about getting correct dynamics of our current state today. Advocating economical policies based on wrong models is a very sensitive socio-political issue. There is some possibility that the local topology of climate attractor has some resemblance to current linear response models, but aggressive denial of the concept that real climate dynamics is much richer than ordinary equilibrium is alarming.

     

  • At June 09, 2006 10:23 AM, Blogger coby said…

    Hi Ed, glad to help, I think... ;-)

    No, CO2 is not the main contributor to climate, it is however the main contributor to the current climate change.

     

  • At September 16, 2006 9:30 AM, Anonymous Anonymous said…

    If CO2 is responsible for 9 to 30% of the total 33 degree green house effect, how do you explain 30% increase in CO2 only resulting in a 0.6 degree rise? This doesn't pass the laugh test.

     

  • At September 16, 2006 11:12 AM, Blogger coby said…

    Hi steven,

    The reason you can not infer the final impact of the CO2 rise thus far from the temperature rise thus far is because the is a great deal of thermal inertia in the climate system. This is mostly due to the large heat capacity of the earth's oceans and results in a lag of several decades between imposing a radiative imbalance and reaching a new equilibrium temperature. You can read a more thorough explaination in this article. There is the additional impact of negative forcing from aerosol pollution (Global Dimming) to consider as well.

    Thanks for the comment, but try more thinking and less laughing! ;-)

     

  • At November 06, 2006 4:59 PM, Anonymous Anonymous said…

    How about the effects of increased water surface area from farming and irrigation? Shouldn't the relative humidity will be related to the local temperature and availability of water? If so, then I would expect that farmland would contribute water to the atmosphere in locations that would otherwise be inaccessible to natural water sources such as the ocean or lakes. Why aren't we considering anthropogenic sources of water, such as water pumped from aquifers? Since water is such a powerful greenhouse gas, shouldn't we be more worried about well-water as a threat to our climate?

    -- Matt

     

  • At November 06, 2006 8:04 PM, Blogger coby said…

    Hi Matt,

    How about the effects of increased water surface area from farming and irrigation? Shouldn't the relative humidity will be related to the local temperature and availability of water?

    Sounds like some interesting questions.

    If so, then I would expect that farmland would contribute water to the atmosphere in locations that would otherwise be inaccessible to natural water sources such as the ocean or lakes.

    Personally, I would be surprised if it is an at all significant effect. How far on average does irrigation water travel from source to farmland? What is the magnitude of the local effect and how quickly does it disperse due to wind? The atmosphere is an absolutely huge volume, the air surrounding just the farmland that is far removed from natural water/air interfaces must be quite tiny relatively. Unlike CO2 which accumulates, water vapour does not, so any anthropogenic changes in relative humidity would be very local and very short lived.

    Why aren't we considering anthropogenic sources of water, such as water pumped from aquifers? Since water is such a powerful greenhouse gas, shouldn't we be more worried about well-water as a threat to our climate?

    Who says no one has looked into this in detail? Regardless, I am confident in my earlier answer, the effects are too localized, small and short lived.

    Thanks for the thoughtful comment!

     

  • At November 13, 2006 12:25 PM, Anonymous Anonymous said…

    Hi Coby,

    Thanks for the response. Do you have any links to anybody who might have accounted for the effects of increases in available surface water on climate? At the very least, we know the amount of irrigated land is increasing (http://www.worldwatch.org/node/4237). The graph shows the area growing at around 1% per year. 250MHectares (irrigated area) is 1/60 the world's land area. This is not a small amount, nor very localized. As far as the fact that the water is not long-lived in the atmosphere, this does not matter: the irrigated farmland (the driver of the increased amount of water vapor) is long-lived and continues to increase the surface area of water from rivers or aquifers exposed to the air. And if it's not precipitating actively in a given region, the atmosphere can always absorb more water. I'd like to see somebody account for this before I disregard the contribution of water on climate...

    Thanks for your input!

    -- Matt

     

  • At November 13, 2006 12:45 PM, Blogger coby said…

    Hi Matt,

    1/60, well I'm impressed by the size of that number! But, don't forget, that is area of land and we are dealing with volume of atmosphere, the troposhpere where water vapour lives being 6-17 km thick. We need to figure out how much the effect of irrigtion spreads in the air.

    I don't have any references for your other questions, did you try looking through the RealClimate link and references therein?

     

  • At November 19, 2006 9:49 AM, Blogger Hank Roberts said…

    Matt believes:

    > if it's [water is] not precipitating actively
    > in a given region, the atmosphere can
    > always absorb more water.

    Why would you believe that? Can you give us a reference supporting this belief? It contradicts what is observed -- relative humidity is well understood.

     

  • At November 29, 2006 9:42 AM, Anonymous Anonymous said…

    How about anyone explaining how humans contributed to global warming during the period 900-1,200 a.d. (or so) when Greenland had virtually no ice cover? Or for that matter, the melting that occurred at the end of the last ice age?

    Eric the Red of the Vikings (Norse) settled in Greenland because it was green with a moderate climate that lent itself to farming. In fact, over 400 farms have been identified in Greenland. Notwithstanding that snow/ice cover was about 15-20% during the Norse period, and it is about 85% today, I have yet to meet someone who can explain how mankind was responsible for the significant 'global warming' in effect at that time.

    Many supposedly knowledgeable people ('experts', or those simply repeating what they hear over and over again) fail to understand that water vapour is by far the only significant greenhouse gas due to the massive amounts of energy it transfers globally from the earth to space.

    In conjunction with incident solar radiation, which is the driving force for all weather, climate, and climate change effects on a large scale, water vapour rapidly restores equilibrium to earth's climate, although it does so in a highly-variable manner that is constantly in flux.

    It is important to note that as more water vapour is produced due to surface warming, more clouds are produced which restrict incoming solar radiation - which in turn reduces surface heating (hence the 'self-cooling' effect that takes place during the movement back to equilibrium).

    Also, since the astrophysical community has determined that 'global warming' has been occurring on planet Mars, does that not give anyone a clue as to what the source of Earth's current 'warming' is?

    Maybe someone can explain how humans are responsible for global warming on Mars also.

     

  • At December 07, 2006 4:51 PM, Blogger coby said…

    Please see:
    http://illconsidered.blogspot.com/2006/02/medieval-warm-period-was-just-as-warm.html
    http://illconsidered.blogspot.com/2006/03/global-warming-is-nothing-new.html
    http://illconsidered.blogspot.com/2006/03/greenland-used-to-be-green.html
    (Greenland is 85% ice sheet, and ice sheet that is ~120K years old)
    http://illconsidered.blogspot.com/2006/01/water-vapor-is-almost-all-of.html
    http://illconsidered.blogspot.com/2006/02/climate-scientists-hide-water-vapor.html
    http://illconsidered.blogspot.com/2006/02/theres-global-warming-on-mars-too.html

    As for Lindzen's Iris effect hypothesis, it is just that, and it is not finding any support in empirical observation of today's changes or the glacial records. It is very old now, and even he has not published anything about it for many years (in scientific journals that is).

     

  • At February 20, 2007 2:47 AM, Anonymous Anonymous said…

    "Water Vapor is only in atmosphere for a short time, CO stays up for a bajillion years."

    Uhhhhuh. Suuuure.

    Water Vapour is part of the Hydrosphere and is the largest factor in the planet's albedo.

    You guys are trying to make Meteorological predictions with a slide ruler.

     

  • At March 22, 2007 8:34 PM, Blogger Unknown said…

    Why would "atmospheric lifetimes" be of any importance to global climate dynamics? One H20 molecule drops down in a rain drop, but the other, with identical properties, gets evaporated and is back doing its regular job, re-absorbing or reflecting radiation. You can't tell the difference between the two molecules. Same with CO2. Therefore, your great grandchildern's childeren will continue to see those water and CO2 molecules in the air, still not being able to distinguish which is which.


    If H2O molecules precipitate out in days and CO2 molecules hang around for decades, then your children will see the last few days worth of H2O molecules and the last few decades worth of CO2 molecules.

     

  • At April 20, 2007 12:25 PM, Anonymous Anonymous said…

    Water contributes about 90 percent of the materials involved in the greenhouse effect, in the form of water vapor and ice (clouds). Carbon Dioxide contributes most of the other 10% of the materials, along with Methane and Ozone and others.

    However, the effects of Carbon Dioxide (a forcing) are greater than that of Water (a feedback), and the effects of Methane (a forcing) are greater than that of Carbon Dioxide. You don't need as much Carbon Dioxide to change things, and you need even less Methane.

    It's not just the amount, it's the effect that amount. For example, Methane warms 23 times as much as Carbon Dioxide, but there's 220 times as much CO2, so it warms more than Methane, overall. We don't really count Water, since it's a feedback (or basically the amount and effect is controlled by other factors)

     

  • At July 20, 2007 12:35 PM, Anonymous Anonymous said…

    I believe an earlier post was headed in the right direction with the "Why would atmospheric lifetimes be of any importance to global climate dynamics?" question. The residual time of a gas in the atmosphere is irrelevant to climate equilibrium unless there is an increase or decrease in the amount. There does seem to be a minor increase of CO2 in our atmosphere but it can not be statistically proven to be due to anthropogenic processes with current data.

    This is the problem with the current debate today. Anyone can spout of numbers as to residual times of a gas in the atmosphere. It is scary to think that CO2 stays in the atmosphere many thousands of times longer that water vapor. residual times are simply irrelevant without an increase or decrease to go along with it and the general public does not know that. All it means is that the amount of CO2 in the atmosphere takes longer to reach equilibrium with change. With the maximum residual time given above all of the CO2 from the beginning of the industrial age is about gone. We may continue to input more CO2 but it is beginning to reach equilibrium.

    So forget about "atmospheric lifetimes" as a counter argument. You will just show your ignorance unless you give a rate of increase and potential equilibrium point.

    I also believe that the scientific argument is that 95% of the anthropogenic contribution is H2O, not that 95% of the "greenhouse effect" is caused by H2O vapor.

     

  • At July 24, 2007 7:11 PM, Blogger coby said…

    ...unless there is an increase or decrease in the amount...

    Well this is exactly the point. If there is an increase in the level of a very short lived gas (ie one whose residence time is shorter than the time it takes for climate to change) then it will return to its former equilibrium level before it can cause climate change. This is the case with H2O but not with CO2.

    There does seem to be a minor increase of CO2 in our atmosphere but it can not be statistically proven to be due to anthropogenic processes with current data.

    It is no minor increase, it is over 35% in a mere 150 years. It s also not a matter of statistics determining the origin. Please see this article, it is irrefutably anthropogenic.

    We may continue to input more CO2 but it is beginning to reach equilibrium.

    I don't at all follow the logic that brought you this conclusion, but it is clearly a conclusion at odds with observed reality. CO2 is rising faster now than at any other time in the historical record, this includes geologic history though there are many limits to how much we know for sure at this time.

     

  • At August 02, 2007 5:11 AM, Anonymous Anonymous said…

    Want the math see http://mysite.verizon.net/mhieb/WVFossils/greenhouse_data.html

     

  • At December 04, 2007 1:56 PM, Anonymous Anonymous said…

    "From a socio-political point of view?"

    Good grief. This explains it all. "Professor of Political and Environmental Science."

    I mean, why not?

    "Environmental Science is the latest 'soft science.' I mean, not really a science at all.

    Fun for your spare time: ask any 4th year PolitySci major the apparently impossible task of defining the word 'politics.'

    Apparently, stops them cold in their tracks. I tried with both a Syracuse and Duke student, same result. The best I got was 'You know, politcal parties and such.'

    But you can't blame them. I mean, the UNESCO educators site starts off with the assertion that there is no accepted workable definition of the word 'politics'--and then proceeds to attempt to define it.

    If it looks like Cargo Cult Science, if it smells like Cargo Cult Science, then guess what?

     

  • At December 13, 2007 2:19 PM, Blogger Will Nitschke said…

    What a sceptic really wants to understand is:

    Why is there a significant discrepancy in the theory of CO2 impact on climate (9%-30% range)if the science is well understood?

    How can climate models be accurate if this number isn't pinned down precisely?

    It is explained to us that CO2 itself does not appear capable of explaining the increases in temperatures measured, but rather that CO2 increases cause feedback effects in other parts of the climate system that increase its overall impact. Possibly these less well understood interactions account for the different estimates in the scientific literature?

    The other sceptical question you need to answer in your article, is why historically CO2 levels were significantly higher than they are now, but this did not cause a runaway green house effect as (apparently) predicted by current computer models? There could be perfectly reasonable explanations for this but unless you try to offer suggestions on how this may be resolved (with appropriate references to the relevant articles) I do not think your reply sounds sufficiently plausible to convince a sceptical thinker.

     

  • At December 15, 2007 1:01 PM, Blogger coby said…

    Hi Will,

    The reason for a large range is mostly because it is an ill-posed question. The better metric is called climate sensitivity to CO2 and that number is getting better and better constrained by models and accumulating observational data from now to millions of years ago.

    Climate sensitivity is around 3oC warming per doubling of atmospheric CO2. This does not include longer term feedbacks from changes in ice sheets or the carbon cycle.

     

  • At February 20, 2008 9:48 AM, Blogger snorbert zangox said…

    I do not see an answer to Will’s question in your response. It is a good question; please answer it.

    In case you have forgotten Will asked, “ . . . why historically CO2 levels were significantly higher than they are now, but this did not cause a runaway green house effect as (apparently) predicted by current computer models?”

    In other words, why is our present situation so significantly different from previous periods of high carbon dioxide concentrations?

    May I add a question? The AGW hypothesis must invoke feedback from water vapor to approach the 2 or 3 Celsius degrees temperature rise that the CCMs predict. Why would a small warming caused by an increased solar output not cause identical feedbacks from water vapor?

     

  • At February 20, 2008 11:13 AM, Blogger coby said…

    In case you have forgotten Will asked, “ . . . why historically CO2 levels were significantly higher than they are now, but this did not cause a runaway green house effect as (apparently) predicted by current computer models?”

    current computer models do not predict a runaway GHE, even at extremely high CO2 concentrations (eg 10,000ppm)

    In other words, why is our present situation so significantly different from previous periods of high carbon dioxide concentrations?

    So, in terms of model expectations, it is not different. In other terms, the most significant differences are that the carbon we are injecting into the carbon cycle was sequestered over a period of 100's of millions of years, for all practical purposes removed until now, and that we are changing this balance on a scale orders of magnitudes faster than any other known event.

    May I add a question? The AGW hypothesis must invoke feedback from water vapor to approach the 2 or 3 Celsius degrees temperature rise that the CCMs predict. Why would a small warming caused by an increased solar output not cause identical feedbacks from water vapor?

    It would. The 2-3oC sensitivity is really a sensitivity to a forcing of some W/m^2 (I think 1.5 or so...? should check...) The changes measured in solar forcing are very much smaller than this.

    BTW, also included in that sensitivity are feedbacks from sea ice changes. Not included are additional carbon cycle feedbacks, ice sheet melting and biosphere changes.

    Thanks for the questions!

     

  • At March 05, 2008 6:12 AM, Blogger barry said…

    Water vapour gets a lot of mention in the IPCC documents (Intergovernmental Panel on Climate Change).

    If you want to corroborate this, you can open the pdf files for each of the IPCC chapters at the links below, type 'vapour' (note the European/Australian spelling) in the search box, and click the appropriate button to search through each document (different versions of pdf have different search buttons).

    IPCC 2001:

    http://www.grida.no/climate/ipcc_tar/wg1/index.htm

    Don't bother with the HTML pages on the left of that web page. They're just summaries of the chapters. Open the pdf files on the right hand side of that page and have a good search.

    IPCC 2007:

    http://ipcc-wg1.ucar.edu/wg1/wg1-report.html

    I chose 3 chapters for 2007, the 3 I thought most likely would discuss water vapour (2, 3 and 8, from memory).

    I also ran a search on 'carbon dioxide' and 'CO2' and compared the results.

    Again from memory, there was 273 hits for 'water vapour', and 295 for 'CO2' from those three chapters, including the studies referenced at the bottom of the page.

    I chose 3 chapters from 2001 and did the same thing. There were tons of hits for water vapour in that one, too. I then checked all the chapters but didn't bother to count, as it was obvious that water vapour was discussed again and again. Some chapters only mention it a little.

    Also, both the 2001 and 2007 reports had sections specifically dedicated to water vapour.

    This says nothing about the focus or quality of the science, of course, but it completely dispels the myth behind this simple statement:

    "Climate Scientists don't talk about water vapour."

    It is true that the function and maths of water vapour as a GHG isn't discussed much (except for new areas of learning, like how it operates in the stratosphere), but that is because the science on it is relatively settled. The IPCC doesn't lay out basic physics or detail the monthly statistics for weather stations. This stuff is too fine a resolution for a document dedicated to describing the state of the science and current best knowledge, rather than the underpinnings. A report that did it all, that laid out the case in fine detail from go to whoa, would be hundreds of times larger than the already large report.

    For finer detail, one needs to backtrack through the studies referenced, and backtrack through the studies referenced by those studies and so on. It's years of work. Basically, you'd have to become a physicist (5 years study) and specialize in the areas you want to know about (more years).

    Ultimately, at this level of the debate, people lean on the authority of others' work. Very few (myself included) have the patience or inclination to really learn what they're talking about. In which case, one has to be very judicious about what work is cited. Within the popular debate on this issue, precious little consideration is given to that. People mostly refer to whatever they come across that supports their view.

    Not saying much new there, I suppose. :-)

    Cheers,

    barry.

     

  • At May 25, 2008 7:49 AM, Anonymous Anonymous said…

    Can I have a link to a credible scientific study which compares the greenhouse effect (or the ability to reflect certain Radiation) of water vapour and Carbon Dioxide, molecule to molecule...

    I think study in that context would solve a lot of problems

    thnx...

     

  • At May 27, 2008 11:14 PM, Anonymous Anonymous said…

    Can I have a link to a credible scientific study which compares the greenhouse effect (or the ability to reflect certain Radiation) of water vapour and Carbon Dioxide, molecule to molecule

    Hello sachithvida,

    Assuming by comparing 'molecule to molecule', you mean weighing up the various optical properties of CO2 and H2O (water vapour), and determining a comparative budget for their contribution to heat retention in the atmosphere, there are numerous studies. Of the two links below, the second is by far the more technical - and is I hope what you're looking for.

    http://www.atmo.arizona.edu/students/courselinks/spring04/atmo451b/pdf/RadiationBudget.pdf

    http://www-ramanathan.ucsd.edu/publications/Ramanathan%20and%20Coakley%20RevGSP%201978.pdf

    The greenhouse effect is based on how much radiation is absorbed (and re-emitted) by gas molecules in the atmosphere, although calculating the radiation budget for the atmosphere also requires accounting for radiation reflected back out to space by atmospheric elements.

    For the layperson, realclimate has a post on how to calculate the radiation budget.

    http://www.realclimate.org/index.php/archives/2006/01/calculating-the-greenhouse-effect/

    barry

     

  • At June 02, 2008 11:02 AM, Anonymous Anonymous said…

    So, in other words the "answer" is not to address the (correct) thrust of the assertion (that water vapor overwhelms CO2 as a greenhouse gas), but rather to try and confuse the challenger because their numbers may/may not add to over 100%? That seems pretty weak...

     

  • At June 03, 2008 9:31 PM, Anonymous Anonymous said…

    I don't think that this appraisal of the semi-popular literature is remotely accurate.apkova

     

  • At July 08, 2008 6:25 AM, Anonymous Anonymous said…

    www.physorg.com/news11710.html

    There's another theory for you to deride...

    It is plausible that damage to ice crystal structure in the mesosphere has increased solar irradiation reaching the Earth's surface. Much like the hole in the ozone layer caused by CFCs did.

    GW is happening, we all know that. It's just to what extent our activities affect the process that people are having trouble with, and if the effect is significant, how best to reduce it.

    Reduce emissions, you say. Well, okay, but find a viable alternative fuel source to power our homes, schools, factories and offices (read economy). The truth is we're still a few decades from that. Nuclear power can be used in the short to medium term, but it takes 3-5 years to build a reactor and a further year to get it 'fired up', then we have to dispose safely the waste fuel afterwards. Reducing fuel available is not viable either, just look at the current situation with oil prices.

    383ppm, 190bn tons of the troposphere is CO2, of this we have contributed 3%, 6.5bn tons, roughly 12ppm. Temperature rises are only 50% prediction made by the IPCC in 1991.

    Maybe the solution is not to reduce the number of barrels of oil pumped per day, but more, how to utilise them more economically.

     

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