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Comments 127151 to 127200:

  1. Is Antarctic ice melting or growing?
    Mizimi - " It is only because it is useful for our mathematical purposes that we lump all those variations into an 'annual mean variation' " Somewhat aside from my point; anyway, different ecosystems are not scattered about at random, so there must be some real tendencies in the factors that affect ecosystems (like rainfall).
  2. Are humans too insignificant to affect global climate?
    Leisureguy, tell your friend to reverse the axis to "demonstrate" a huge drop in CO2. Seriously, if one can not read a graph should not even try. Expanding the axis means let people see and judge. On the contrary, putting the origin of the y axis to zero means mask what people could (or should) read.
  3. Are humans too insignificant to affect global climate?
    %26 To have denialists complain about misleading chart axes is a bit rich. But this complaint is silly in its own right. Changing the origin to 0 would change (and "exaggerate") nothing else except that the graph would now sit half way up the axis. The difference between 275ppm and the present level is still 110ppm or so. It is quite a common graphical convention, when the low points are well above zero, to have the y axis starting at an appropriate level.
  4. How we know global warming is still happening
    Philippe, if the temperature dew point spread is unchanged and air cools the same amount (in degrees C) from a warmer maximum, then it will condense more water based on the Clausius-Clapeyron relationship(which is the basis of the assumption of constant RH). More water condensing should lead to more cloud IMO. This idea is not in contradiction with the other papers I have posted IMO, for the simple reason that it is hightly likely that other things than the **feedback** process I outline above influence cloudiness(on regional and global scales). This is really no different from allowing that we can have a period of cooler(or falt temperature) years, even while ever stronger CO2 feedback is (supposed to be) heating the climate. Something besides the feedback I have mentioned, may be forcing the clouds and, hence, obscuring the feedback signal. As for substantiation, I don't think it is at all difficult to find people supporting the idea that cloud feedback is negative. ROy Spencer is one prominent example. I suppose I can find a specific paper. IAC, RSVP quoted a paper above(which I haven't read yet) and I have just been laying out what I presume to be the theoretical underpinnings of their conclusion(I haven't read the paper yet). Cheers, :)
  5. Are humans too insignificant to affect global climate?
    Regarding the first chart: a denialist I correspond with violently objects to this chart: the left axis begins at 250, rather than 0, which greatly exaggerates the increase. Either give us a chart which starts at 0, or indicate with a jagged line that the Y-axis starts way up the scale. That will end that argument, I hope.
  6. Philippe Chantreau at 04:19 AM on 16 October 2009
    Comparing CO2 emissions to CO2 levels
    Actually no, E&E is not peer reviewed. Papers are submitted to the the editor, Sonja Boehmer-Christiansen, who then decides what gets published. Her own record of publications is extremely scant at best: I believe that around 4 papers were found in one of the largest database of science publications, mostly all elaborating on the same topic, and only marginally related to natural sciences. She also has a history of sympathy toward anti-evolution/creationist ideas. Someone posted a link in this blog to more info, but I can't recall in which thread at the moment. The journal has a self proclaimed vocation of offering a "platform" to "authors" critical or skeptical of AGW and that seems to be the only consistent criterion for selecting papers. E&E is by no means a reliable or even interesting source for any kind of scientific research. People who do real science and research do not even know of its existence. The ideal venue for Beck, really. I am not sure whether or not he actually published in it. Perhaps even Sonja B-C could not bring herself to pass such doctored graphs as the one mentioned by Ned. The trick is so thick that it wouldn't fool a junior high student, yet Beck seems to find it perfectly fine. Don't waste your time on stuff with which even McIntyre wouldn't compromise himself.
  7. Comparing CO2 emissions to CO2 levels
    Shawnhet - thank you for the link Ned - Thank you for the information. I agree with you about those claims being "ridiculous". the reason of my question was that I´d like to find something easy to understand at-a-glance, that could reach a denier´s mind. That paragraph you pasted is very interesting, and puts in perspective the wild claims that CO2 varied like crazy in the 19th century. But the link is not something that makes clear who´s saying that. A denier could say that it´s made-up. Maybe there´s a published paper confirming the stability of gases trapped in ice cores over long periods of time? Or some more official website (like the University´s) with that letter from Keeling? Philippe - Of course it´s a crock. But people cling to that kind of stuff. By the way, Energy & Environment is peer reviewed, right? even if it´s crap...
  8. Empirical evidence that humans are causing global warming
    RSVP Your questions seem to go to basic climate physics, electromagnetic radiation, light - energy, blackbody radiation, and greenhouse gas IR absorption - emission. I suggest that you read David Archer's excellent book, Global Warming - Understanding the Forecast to get a solid grounding in climate physics. The book is actually a text used at the University of Chicago for non-science majors. It is very readable and will help you understand what climate models do. Since Archer presents the subject in a systematic way, it will be easier to understand than a series of Q&As from a number of Skeptical Science readers. In addition to the book, Archer provides videos of his U of Chicago lectures and access to 8 on-line models. I've posted about Archer's book at this link.
  9. Empirical evidence that humans are causing global warming
    John, Yet another outstanding post. I will also be referring to the Wang 2009 article on my site. I have been using you as a source more and more frequently. BTW, I hope you do not mind but I have referred readers over at WUWT to your site quite a bit lately. :) You are doing a tremendous service to the general public!
  10. Empirical evidence that humans are causing global warming
    "Whatever energy is radiated into the atmosphere by the surface of the Earth, whether by sea or land, represents a LOSS of energy from the surface. There is no radiative heating of CO2 without cooling of the Earth's surface." I suppose this could make sense if there was no sun adding to the mix, but otherwise this sounds like me saying my stove top surface actually cools because it's loosing energy as it radiates heat.
  11. How do we know CO2 is causing warming?
    I don't see the point with the Pielke references, as Evans & Puckrin (2006, link is given above just after the Philipona paper) show that the change in DLR reported by Philipona et al. is caused by greenhouse gases.
  12. Empirical evidence that humans are causing global warming
    RSVP, You are having a problem with visualizing how the greenhouse effect works. Energy is not "trapped" by the greenhouse effect, the flow of energy is continuous but slowed in the outward direction. The surface is warmer with a greenhouse effect because it looses energy to space more slowly. The atmosphere is like the lithosphere or crust of the Earth in that the very high heat just several miles below Earth's surface only very, very slowly is allowed to escape the Earth's interior. Just think of how much cooler the Earth's interior or the interior of the Sun would be if the overlying matter were not opaque to outgoing radiation.
  13. Empirical evidence that humans are causing global warming
    RSVP, your comment did the impossible, being at the same time trivial and wrong. For sure you completely lack the concept of energy balance, which is (should be?) indeed trivial. I don't think this blog should be involved in such high school level, or maybe even common sense, discussions or teaching.
  14. Philippe Chantreau at 00:01 AM on 16 October 2009
    Comparing CO2 emissions to CO2 levels
    Beck rearing his ugly head again. Beck does not have any paper. He does not publish in real science journals. His "work" is irrelevant to any discussion of science.
  15. Empirical evidence that humans are causing global warming
    Whatever energy is radiated into the atmosphere by the surface of the Earth, whether by sea or land, represents a LOSS of energy from the surface. There is no radiative heating of CO2 without cooling of the Earth's surface. Any radiative energy that returns to the Earth from the atmosphere (having originated from the surface), would warm the surface, but at the same time be associated with equal COOLING of the atmosphere. This energy has essentially been reflected or could be considered as if it never left the surface in the first place. In terms of this type of accounting, the energy cannot be in two places at once. It is either on the surface or in the atmosphere. As a result, globally speaking, it does not seem possible for there to be a net positive offset DIRECLTY related to the operation of these radiative mechanisms. However, the portion of energy that is "trapped", due to reflection as described, would seem to accumulate, and cool through either conductive or convective mechanisms. Those which caused the air to warm would now depend ironically on greenhouse gases for expelling this additional energy. For those that may think this explanation is oversimplified, please take a look again at the diagram of the Earth's atmosphere, and remember that you cant get something for nothing, because if you could, we could solve the energy crisis by simply building greenhouses in our backyards. My last thought would also be to consider the temperature on the Moon's lightened surface, which has absolutely no atmosphere at all.
  16. Comparing CO2 emissions to CO2 levels
    "a cyclic patters" should obviously be "a cyclic pattern". Apologies for the typo.
  17. Comparing CO2 emissions to CO2 levels
    shawnhet writes: "Alexandre - here are some publications to Beck's papers. [...] Personally, I don't know what to make of them." E.G. Beck's claims are simply ridiculous. On CO2 measurement, he apparently thinks that the atmosphere used to show immense (unphysical) swings in CO2 that suddenly stopped just when we developed a more accurate method for measuring CO2: http://scienceblogs.com/deltoid/2006/10/more_nonsense_about_co2.php http://scienceblogs.com/deltoid/2008/03/remember_eg_becks_dodgy.php Ralph Keeling noted the absurd implications of Beck's supposed record of atmospheric CO2 from unreliable chemical measurement data: ============= "It should be added that Beck’s analysis also runs afoul of a basic accounting problem. Beck’s 11–year averages show large swings, including an increase from 310 to 420 ppm between 1920 and 1945 (Beck’s Figure 11). To drive an increase of this magnitude globally requires the release of 233 billion metric tons of C to the atmosphere. The amount is equivalent to more than a third of all the carbon contained in land plants globally. Other CO2 swings noted by Beck require similarly large releases or uptakes. To make a credible case, Beck would have needed to offer evidence for losses or gains of carbon of this magnitude from somewhere. He offered none." http://www.biokurs.de/treibhaus/180CO2/Response-Beck-by-R-Keeling-2.doc ======== Beck also makes completely unjustifiable claims about cyclic patterns in temperatures at the millennial scale. Check out this graph, where Beck plots a cyclic patters that supposedly represents a fluctuating climate signal ... but weirdly enough, the cycle continues smoothly across a discontinuity (and scale change!) in the X-axis of the graph: http://www.realclimate.org/index.php/archives/2007/06/curve-manipulation-lesson-2/ http://scienceblogs.com/deltoid/2007/06/another_dodgy_graph_from_eg_be.php#more There is a reason why, for example, Steve McIntyre refuses to allow discussion of Beck's work on ClimateAudit. Lending any credence to that kind of nonsense is probably the fastest way to demolish your own credibility.
  18. Empirical evidence that humans are causing global warming
    Sorry, I should have listed A Saturated Gassy Argument second. Your first stop, Paul, should be right here at Skeptical Science: Is the CO2 Effect Saturated?. If you need more convincing after that, click on the links in my comment immediately above this one.
  19. Empirical evidence that humans are causing global warming
    Paul, saturation has not been reached. See A Saturated Gassy Argument at RealClimate. That link is to Part I, but there is also a Part II.
  20. Empirical evidence that humans are causing global warming
    The only problem with this analysis is that beyond certain levels the carbon dioxide level gets saturated and very little extra warming occurs. Most of the climatologists I've consulted agree with this; it's just a question of at what level warming stops. Many sources seem to agree that 200 ppm sees the most warming; after that, warming declines and eventually becomes minimal. At 400 ppm, we've almost certainly reached the point of effective saturation, which might explain why the planet hasn't warmed in a decade.
    Response: I suggest you read through the post again. Two points to look for. One, the CO2 effect is not saturated because we're observing an enhanced greenhouse effect. The logarithmic relationship between CO2 and temperature has been confirmed by empirical observations. Secondly, don't be misled by erroneous arguments like 'global warming stopped in 1998'. The planet is still accumulating heat. Satellite measurements show more energy coming in than escaping back out to space. We have been warming over the last decade.
  21. pekka.lehtikoski at 11:47 AM on 15 October 2009
    Humans are too insignificant to affect global climate
    It would be interesting to have atmospheric CO2 and human emitted global carbon emissions plotted in same graph with time scale of last 200 years.
    Response: This is done in Comparing CO2 emissions to CO2 levels.
  22. pekka.lehtikoski at 09:58 AM on 15 October 2009
    A broader view of sea level rise
    Thank you for your comment. Yes, I meant the notion that humans, are causing global warming, and specifically by burning fossil fuels. First disclaimer, I am no expert, but only trying to learn. My problem is: If I look at period 1880-2005, and divide it to two parts: 1880-1950 and 1950-2005. About 90% of fossil fuel burning occurred on later part. Seal level and CO2 in atmosphere increased "roughly" linearly in both parts. Even it seems very likely that we are increasing atmospheric CO2 by burning fossil fuels, it is hard to believe that this is the whole truth. On the other hand atmospheric CO2 remained constant for long time before 1800, and it seems unlikely coincidence that exploding human population would have nothing to do with it. Could cutting down forests for agriculture have anything to do with it? Best regards, Pekka
  23. Comparing CO2 emissions to CO2 levels
    Tony The CDIAC site (Fig. 1 caption) reports these data as "fossil fuel" carbon, so I presume it does not include deforestation/biofuel burning. They give lots of references on sources and estimation techniques; not a literature with which I'm familiar. The slope by the end of the curve is pretty dramatic. No sign of any effective political/societal will yet.
  24. Comparing CO2 emissions to CO2 levels
    Thanks for that article, Chris! The Discussion section is an especially good summary to counter the argument that "CO2 stays in the atmosphere only for five years."
  25. Philippe Chantreau at 03:37 AM on 15 October 2009
    How we know global warming is still happening
    Shawnhet, you won't see more cloud formation if the temperature/dew-point spread is unchanged, as will likely be the case if relative humidity is conserved. If relative humidity decreases, you'll see less cloud formation, regardless of the absolute humidity. And you seem to assume that, as warmer air (i.e. containing a higher absolute humidity) will reach the dew point, all of its moisture content will condense and precipitate. I seriously doubt that it is that simple. This hypothesis (which you do not substantiate with science papers) is also very much in contradiction with references you provided on vegetal NPP, especially what has been observed over the Amazon basin: more sun exposure, due to lower cloud cover. Choose which hypothesis you want to defend, but keep in mind that the Amazon drying is based on empirical obervations.
  26. Comparing CO2 emissions to CO2 levels
    Alexandre - here are some publications to Beck's papers. http://www.biokurs.de/treibhaus/180CO2_supp.htm Personally, I don't know what to make of them. Cheers, :)
  27. It's the sun
    "What the science says... Solar activity has shown little to no long term trend since the 1950's." This is incorrect. Although the maximum amplitudes of sunspot numbers have gently declined since the 1960's, the short duration of the minima until the most recent has meant that the average sunspot number increased right up to 2001, shortly before the rapid warming ended. The measurement of TSI is a controversial area, with two teams disagreeing over the splicing and calibration of the data. The science is not settled here.
    Response:

    While there is some debate over the long term trend of solar activity, the debate is essentially over whether the sun is showing a slight warming trend or a slight cooling trend. Either way, the sun cannot have played more than a minimal part in recent global warming. Nevertheless, various independent measurements of solar activity all confirm the sun has shown a slight cooling trend since 1978. This means rather than contribute to global warming, solar activity has actually had a slight cooling effect on climate.

  28. It's the ocean
    "What the science says... Oceans are warming across the globe." This is incorrect, although you might get away with saying they are warming on a six year average, for a little while anyway. Cazenave et al 2008 concludes that the steric sea level has been falling since 2006. The ARGO data shows that there has been a recent swift fall in ocean heat content globally. (Oct 2009 prelim data)
  29. Comparing CO2 emissions to CO2 levels
    That's more politics than science RSVP We have a pretty good handle on how long it takes for atmospheric CO2 levels to "return to normal" after marked enhancement; e.g.: D. Archer & V. Brovkin (2008) The millennial atmospheric lifetime of anthropogenic CO2 Climatic Change 90:283–297 [abstract below **] http://www.atm.damtp.cam.ac.uk/mcintyre/archer-carbon-tail08.pdf The reason that well-informed people "support" the theory is that the evidence overwhelmingly "supports" the theory, and one should always base one's scientific understanding of the world on evidence rather than political notions. No one is suggesting that we stop burning fossil fuels. The mature and far-sighted point of view is to recognise the science, and consider the likely consequence of continued massive enhancement of the greenhouse effect. The aims are then to accelerate the transition towards replacing fossil fuels with renewable energy sources (we are already in the early stages of this process), to address possible technologies for carbon sequestration (not too hopeful right now, but there are some possibilities), and to consider policies for adapting to some rather serious warming should mitigation strategies be less succesful than we would like. The evidence indicates that there is only one major factor in global warming - it's huge enhancement of the atmospheric greenhouse gas concentrations (CO2, methane, N2O, CFC's). So we should obviously address that... [***] Abstract: The notion is pervasive in the climate science community and in the public at large that the climate impacts of fossil fuel CO2 release will only persist for a few centuries. This conclusion has no basis in theory or models of the atmosphere/ocean carbon cycle, which we review here. The largest fraction of the CO2 recovery will take place on time scales of centuries, as CO2 invades the ocean, but a significant fraction of the fossil fuel CO2, ranging in published models in the literature from 20–60%, remains airborne for a thousand years or longer. Ultimate recovery takes place on time scales of hundreds of thousands of years, a geologic longevity typically associated in public perceptions with nuclear waste. The glacial/interglacial climate cycles demonstrate that ice sheets and sea level respond dramatically to millennial-timescale changes in climate forcing. There are also potential positive feedbacks in the carbon cycle, including methane hydrates in the ocean, and peat frozen in permafrost, that are most sensitive to the long tail of the fossil fuel CO2 in the atmosphere.
  30. Comparing CO2 emissions to CO2 levels
    RSVP "those that believe CO2 is causing global warming support the theory because they assume we might actually stop burning fossil fuels" You should not presume what people think or believe. As for myself, but i bet for most, it's science that comes first. Then you try your best to avoid the unwanted outcomes of doing nothing. "Yet, one side is ONLY concerned with attacking a single element" Please read, for example, the greenhouse gases covered by the Kyoto Protocol http://en.wikipedia.org/wiki/Kyoto_Protocol and the too many times people here replied to you very same claim that only CO2 matters.
  31. Comparing CO2 emissions to CO2 levels
    If these curves are indeed accurate,(or even approximate), it does not bode well for the planet's biological health. The curves are not quite, but nearly one to one, which indicates little CO2 absorption. The difference in slopes between blue and red zones could be used to give an estimate of how many years it would take for CO2 to return to "normal" if humans stopped burning fuels immediately... which they wont. Maybe asphyxiations will precede heat strokes and take care of global warming all together. The funny thing about the CO2-global warming debate, is that those that believe CO2 is causing global warming support the theory because they assume we might actually stop burning fossil fuels over having the Earth's temperature rise a few degrees. That is not going to happen. You need a better reason than that. In fact, two or three degrees may just be the most reassuring reason to continue burning fossil fuels. We WILL however stop burning fossil fuels when it is all spent. That is for sure. And as far as the difference between positions of those that agree that CO2 is causing global warming, and those that do not. Neither side is saying that CO2 is the only factor, nor denying that it is not contributing somewhat. Yet, one side is ONLY concerned with attacking a single element of the problem, and its not even clear with what remedy.
  32. Comparing CO2 emissions to CO2 levels
    Keopele, i'd suggest to take a look at the many posts of this and other blogs run by scientists and convince yourself ;)
  33. Comparing CO2 emissions to CO2 levels
    I am new here and I just want to try to either deny or verify info I have on global warming. I want truth above all else, regardless of self-interest My father is a scientist at Battelle Labs and I trust his jugdment on many subjects, as he is very skeptical and objective by nature. I asked if he knew anything about Global Warming. He mentioned that there were several scientist that he knew personally doing research on global warming. Battelle Labs is a research organization I think most consider as a credible source of scientific information. He said that all the scientists he knew in the field at Battelle felt that global warming was primarily caused by humans. He said that this research was based on several differen't approaches, all reaching the same conclusion. My father is not a climate scientist, but he is a scientist and has been with Battelle for over 30 years. Do we have any research from Battelle Labs as reference for conclusions either for or against Global Warming? I ask this question, because I consider Science from Battelle a credible source. I know the PHD's at Battelle don't make the big money they can make with other organizations. Battelle is a non-profit of serious scientists. The scientists there work for love of what they do an not $$. If they wanted money they wouldn't be at Battelle, so that weeds out the ones who are motivated by ego and $$. I don't trust many sources as most are biased and masters as skewing data to reach the conclusions that meet there objectives or bias. I do believe in global warming I just want to see scientific consensus of serious scientists. Keopele
  34. How do we know CO2 is causing warming?
    @ J Cook “I'm surprised to hear you say global temperature has risen as fast numerous times over the last few thousand years”. here the graph of Moberg and Esper without instrumental data http://www.wpsmeteo.it/index.php?ind=news&op=news_show_single&ide=761 so that "apples and oranges" are not compared http://www.co2science.org/data/mwp/studies/l1_nhemis2090.php Philipona 2004? http://pielkeclimatesci.wordpress.com/2009/09/29/observational-evidence-of-a-change-of-surface-radiative-forcing-in-a-paper-philipona-et-al-2004/ http://pielkeclimatesci.wordpress.com/2009/08/29/remarkable-admission-by-james-annan-on-the-klotzbach-et-al-2009-paper/
    Response: Pielke isn't disputing the results of Philipona 2004 - I suggest you read the post you link to.
  35. How do we know CO2 is causing warming?
    TP100, regarding the overall benefits of more CO2, see the Skeptical Science post Global warming is good.
  36. It's cooling
    Not only does this site have depth and clarity, you're a model of how to present facts without demonizing those with contrary views. Thanks!
  37. How do we know CO2 is causing warming?
    TP100, you wrote "Lastly, if Co2 is so bad for our planet, why do people who own greenhouses increase Co2 levels to as much as 1000-1200 PPM? The reason is not because it causes harm, but because plants thrive in environments with higher Co2 levels." And then you wrote "Is it a myth that Co2 is a nutrient to plants and would would not survie without it?" Nobody is making that broad claim that CO2 is "bad for our planet." Instead there are claims about several specific effects of the warming and ocean acidification caused by extra CO2--CO2 beyond what we have now. The effects of CO2 itself on plants are some positive and many negative. For example, some weeds such as poison ivy will thrive with greater CO2--more so than many other plants--but we don't really want weeds to thrive. And plants do not just grow better with higher levels of CO2. They grow differently. For example, some put more of their materials into inedible stalks than into their fruits, making crops harder to process without a concomitant benefit. There is a U.S. Department of Agriculture report with handy fact sheets on the effects of global warming and higher levels of CO2, and the news definitely is not all good. Also see the comments starting with comment #9 on the Skeptical Science post "Are humans too insignificant to affect global climate."
  38. How do we know CO2 is causing warming?
    TP100, you wrote "Is it a myth that Co2 is only .04% of the atmosphere? ... Is it a myth that Co2 is a relatively weak greenhouse gas?" See my comment #17 to the post "How we know global warming is still happening."
  39. Philippe Chantreau at 05:40 AM on 14 October 2009
    Are humans too insignificant to affect global climate?
    What "might" happen might already be happening, as in the Amazon getting drier (observed and well documented). The rains in the Philippines and West Africa are weather events, so I won't go there. Once again, it's ironic that "skeptics" so often point to the tiny atmospheric fraction of CO2 but so generously impart it that tremendous fertilization power. I admit, however, that you are of a more sophisticated kind. Commercial GH routinely use 1200 ppm, or at least 800 ppm concentrations, since they don't see that much result below. And of course their water and nutrients are optimized 100% of the time.
  40. Are humans too insignificant to affect global climate?
    If CO2 isn't good for plants, why do greenhouses pump it in? That one simple question will put all your silliness in context. People whose livelihood depend on growing plants quickly disagree with you about the benefits of CO2. Most people whose livelihood depends on growing plants don't grow them in greenhouses. They grow them outdoors, in environments where nutrients or water are the primary limiting factor, not CO2.
  41. How do we know CO2 is causing warming?
    TP100, you wrote "However, the fundamental argument of AGW theory is that this trace gas (at slightly less than .04% of the atmosphere) is THE key ingredient to controlling a massively complex system such as climate. We can essentially dismiss the effects of solar variation, PDO, orbital changes, magnetic field changes, or hundreds of other variables and their interrelationships because we know for a fact that Co2 is the single most important component and it's interrelationships with other variables such as water vapor completely dominate or overshadow all other forcings. That is another myth. It's easy to get that misimpression, though, because climatologists tend to take for granted that everybody already knows the other forcings have been accounted for. As Chris and SteveL replied to you, there are many other forcings. Attention being focused on CO2 because the other forcings have small or no long-term changes (trends) at this time. At various times in the past, various of those other forcings have changed more than CO2 has. But not now. Another reason for our focus on CO2 is that it is one forcing we can do something about.
  42. How do we know CO2 is causing warming?
    TP100, you wrote "The explanation essentially says - "we can't think of anything else that could cause the warming over the last 30 years, so it must be Co2". That is one of the myths--that climatologists are merely casting about for an explanation. In fact the opposite thinking process is what got them to these conclusions: The fundamental physical causes were realized in the 1800s and very early 1900s, including the prediction that those physical mechanisms would cause global warming. That was decades before it was possible for anyone to observe global warming. Lo and behold, now that we have the ability to observe, we discover that the predictions are accurate. There are concrete, physical, experimentally verified mechanisms for the effects.
  43. Are humans too insignificant to affect global climate?
    Philippe, whatever the reason for the increased plant growth, the fact is that it apparently took place. I don't really feel the need to debate CO2 fertilisation as I feel it is well established science(backed up by the experience of nearly every commercial greenhouse). I agree that it was not the most important influence in the increase in NPP in recent years, but it was an important one. Whether there are some negative impacts from climate change(though I note that such negatives appear to be modelled impacts of what *might* happen), doesn't change the fact that there are also some positive impacts as well. Cheers, :)
    Response: To put the positive impacts of extra CO2 and global warming in perspective, compare all the negative impacts versus all the positive impacts.
  44. How do we know CO2 is causing warming?
    TP100, read more carefully. See comment #13 on this thread -- CO2 is not thought to be the only thing affecting climate. Nobody is claiming a runaway (runaways require positive feedbacks, but not all positive feedbacks yield runaways). Is there another forcing that has increased by 33% since 1750? Is there another forcing that might double over the next 100 years? Will solar forcing do that? But we can limit the amount of future forcing from CO2. That's not to say that we will "control" climate; rather it means that we can reduce the amount of anthropogenic forcing. I hope this gives you a clue as to why people tend to talk about carbon dioxide.
  45. How we know global warming is still happening
    WeatherRusty, I'm not sure what our disagreement is(if any) anymore. Your link appears to agree with my POV that higher levels of specific humidity are associated with higher(sustained) levels of precipitation. For instance"(1) No amount of rising air will produce precipitation unless moisture is present. The more **moisture that is present, the higher the potential for precipitation if uplift mechanisms are in place**." If atmospheric instability and uplift remain constant and the amount of specific humidity rises, we should expect more cloud formation. Cheers, :)
  46. How do we know CO2 is causing warming?
    re #54 A couple of your points: We don't dismiss the effects of solar variation (there has been negligible secular solar variation since the late 50's and so this has made a negligibile contribution to the very marked warming of this period; it's estimated by solar scientists that solar effects may have contributed around 0.1 oC of warming to the 20th century trend).. J. L. Lean and D. H. Rind (2008) How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006 Geophys. Res. Lett, 35, L18701 http://pubs.giss.nasa.gov/abstracts/2008/Lean_Rind.html ...or PDO (a recent analysis of ocean current effects indicates that these have modulated the warming during the 20th century but have made almost zero net contribution)... K. L. Swanson, G. Sugihara, and A. A. Tsonis (2009)Long-term natural variability and 20th century climate change. Proc. Natl. Acad. Sci. USA 106, 16120-16123 www.pnas.org/content/106/38/16120.abstract ...or orbital changes (these have obviously played a major role in ice age cyles, and have had a small contribution to Holocene temperature variations, but their contrbution to the warming of the 20th century has been essentially zero)... ..or magnetic field effects (these have been studied in detail and there is no evidence that these have made an impact to warming of the last 100 years). So we certainly don't dismiss these things (or any factors that are known to affect climate). e.g. see Figure 2 here: http://www.skepticalscience.com/The-CO2-Temperature-correlation-over-the-20th-Century.html We didn't have "run away warming back in the Carboniferous period when Co2 levels were into the thousands of PPM as opposed to the 380 PPM today", because, in fact during the Carboniferous CO2 levels were generally very low (even possibly lower than today during parts of the Carboniferous and early-mid Permian). That's why the earth had some major long-lived glaciations and otherwise cold periods during the Carboniferous and early/mid Permian. During some parts of the Carboniferous when CO2 levels were a bit higher, the evidence indicates that the earth was warmer. In general there is a rather strong relationship between proxies for atmospheric CO2 concentrations and earth temperature regimes right throughout the last 500 million years. http://droyer.web.wesleyan.edu/PhanCO2(GCA).pdf
  47. How do we know CO2 is causing warming?
    My apologies for posting twice. Tom Dayton - actually, I've read through the debate and I have found the AGW explanations lacking. The explanation essentially says - "we can't think of anything else that could cause the warming over the last 30 years, so it must be Co2". I am just not buying into that argument. There is a lot of information documenting that the earth is warming, and few people dispute those findings. The question is - is it really eing caused by man? While this website provides explanations, I can find equally if not better contrary explanations on skeptical websites. Re: my mythical questions - Is it a myth that Co2 is only .04% of the atmosphere? And, is it a myth that Co2 concentrations were much higher in prior geologic times? Is it a myth that Co2 is a relatively weak greenhouse gas? Is it a myth that Co2 is a nutrient to plants and would would not survie without it? My argument simply states that climate is massively complex, while when you boil down AGW theory to it's most basic level, it says climate is actually quite simple - if humans can control atmospheric Co2 levels, we can control climate. Nothing else matters, and that is an absurd argument. If that is an incorrect characterization of AGW theory, then why all the fuss about capping Co2 emmisions?
    Response: The argument "we can't think of anything else  so it must be Co2" is indeed inadequate. But that's not the argument being made. On the contrary, posted above is empirical evidence that increased CO2 has caused an enhanced greenhouse effect. Theory says more CO2 will trap more heat leading to global warming. Now we have observations that quantitatively confirm this.

    Is it a myth that CO2 is a relatively weak greenhouse gas? Yes, the empirical evidence confirms the amount of extra heat trapped by CO2. The numbers have spoken. Climate is certainly complex but the principle that CO2 traps heat - and that more heat in our climate leads to warmer temperatures - is straightforward.

    Anyway, this is the second time I've clarified that CO2 is not the only radiative forcing but it is the most significant source of warming. If you continue to persist with the strawman argument that we're claiming "nothing else matters", those comments will be deleted.
  48. Comparing CO2 emissions to CO2 levels
    John, Good post, as usual. I have a somewhat off-topic quiestion, though. Mauna Loa and the Law Dome Ice core seem to match nicely. There´s a "skeptical" claim about ice cores not being accurate samples of the atmosphere over long periods of time. Ernst Beck says that. I think Jaworowski too. Do you have any comments or known papers about that?
  49. How do we know CO2 is causing warming?
    Sorry, TP100, everything you wrote is a myth. You're on the right web site to get answers. Look at the top left of this page and click "View All Arguments." But from the phrasing of your post, I think you would still be frustrated by such a point by point approach to getting answers. So I suggest that you first read cce's The Global Warming Debate, which will tie together the threads. Then come back to this site to look for answers to specific questions.
  50. How do we know CO2 is causing warming?
    This discussion is quite interesting, but I have some basic observations that are pretty straightforward. First, just to state the obvious, no one disagrees that Co2 absorbs heat and helps keep the earth warm. However, the fundamental argumet of AGW theory is that this trace gas (at slighly less than .04% of the atmosphere) is THE key ingredient to controlling a massively complex system such as climate. We can essentially dismiss the effects of solar variation, PDO, orbital changes, magnetic field changes, or hundreds of other variables and their interrelationships because we know for a fact that Co2 is the single most important component and it's interrelationships with other variables such as water vapor completely dominate or overshadow all other forcings. The argument is absurd on it's face. Just reading through the posts from both skeptics and proponents provides a pretty good indication of the complexities surrounding this science. We hear that we are nearing a tipping point where we will have run away warming if we do not stop "polluting" our atmosphere with Co2. My quesion is - why didn't we have run away warming back in the Carboniferous period when Co2 levels were into the thousands of PPM as opposed to the 380 PPM today? Or for that matter in other subsequent periods when Co2 concentration was much higher than it is today? Instead, the earth went through several cooling and warming periods irrespective of the Co2 levels. Another observation that has been addressed to some degree in this discussion is that there is a diminishing return of warming caused by Co2, meaning that there is a non-linear relationship between Co2 levels and warming. Yet, what most models seem to show is a linear relationship that is not supported by the science. Lastly, if Co2 is so bad for our planet, why do people who own greenhouses increase Co2 levels to as much as 1000-1200 PPM? The reason is not because it causes harm, but because plants thrive in environments with higher Co2 levels.
    Response: CO2 is just one piece of the climate puzzle. However, as we're emitting so much CO2 into the atmosphere, it does happen to be a fairly large piece. We can theoretically calculate how much heat CO2 traps and taking into account all the various radiative forcings that cause warming, it is the greatest contributor:



    We're not ignoring solar changes. We know the forcing from orbital changes and they're insignificant compared to the radiative forcing from CO2. The PDO has no long term effect on radiative imbalance - it's an internal variation resulting from the exchange of heat between the atmosphere and ocean.

    You're right to point out that CO2 is not the only radiative forcing. It's important to keep this in mind when evaluating past periods where CO2 was higher than now. In some periods, the sun was less bright than now. In other periods, the planet had a completely different configuration with all the continents merged into a single continent so the radiation budget was much different.

    Models and theory do not use a linear relationship between CO2 and global temperature - it's a logarithmic relationship. And our theoretical understanding is confirmed by empirical observations. As explained above, satellite measurements of outgoing longwave radiation and surface measurements of downward longwave radiation both find an enhanced greenhouse effect. Both are independent empirical confirmations of theoretical expectations. The way CO2 is behaving, the amount of heat it is trapping, has been quantitavely measured.

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