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

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Comments 127001 to 127050:

  1. What does past climate change tell us?
    re #27: HumanityRules, let me go back to my vision for a future and compare it with yours, since we seem to share the ideal of economic and societal advance in poor countries. I suggested that a huge investment in sustainable energy sources (especially solar power, with some carefully considered biofuel production etc.) is the likely way that economic advance might be realised in these countries. You consider that unworthy of comment. So let’s be a little more specific. Solar power is a truly massive potential source of power. Despite the fact that it’s in relative infancy, it produces around 16 GW of power worldwide. This is a tiny proportion of the total human energy use (~15 TW), but the potential for expansion, especially in regions of the world with high surface solar flux, is huge (the solar flux at the surface is equal to ~10,000 x the total world energy use, so we need to tap a tiny proportion of this to make massive inroads into replacing fossil fuels with solar, not to mention other sustainables). There are already solar power plants in the US, Spain (lots), Germany, Portugal, Korea….when completed the solar thermal power station in Gujarat in India will be the largest in the world…a 2GW solar plant is being built in Mongolia; there are major projects approved for large solar plant in Egypt, Mexico, Morocco….etc. etc. I’d like to know why you consider that these technologies should be left out of the equation for sub-Saharan Africa. Likewise, careful approaches to biofuel production has considerable potential. Brazil gets nearly 20% of its automotive fuel from (bio)ethanol…the production of ethanol in the US is now a large industry employing many hundreds of thousands of people. Again I’d like to know your reasons for dismissing this (and geothermal, wind, hydroelectric where this is still untapped, wave …) from your future for economic expansion in sub-Saharan Africa. The countries in this region are starting from a very, very low base in terms of current energy use – expanding this with a strong focus on sustainable energy is an obvious means of economic advance. On the other hand, your vision is seemingly based on a truly massive expansion of fossil fuel use. Speaking of the poor regions of the world you say you “aspire to see them have everything we have, and more”. Fine, but what specifically do you mean by that? At present each US citizen releases 19 metric tons (mt) of CO2 into the atmosphere each year. Is that level of fossil fuel consumption in your aspiration for the world? If so, CO2 emissions will rise to around 5 times current emissions, and our civilizations will be committed to a hellish short future with extremely rapid warming and sea level rise, unstoppable destruction of the tropical rainforests, until we run out of oil (in around 10 years), gas (30 years) and eventually even coal (~80 years). Then we’re pretty much back to the stone age… Or might your aspirations be more along the lines of Switzerland (5.6 mt CO2 per person per year). Then CO2 emissions would only double, the rate of adverse consequences would be slowed somewhat, and we’d have a rather larger number of decades before the fossil fuels were used up and the populations return to the stone age… So you have to be a bit clearer about your vision. I don’t think yours (massive expansion of fossil fuel use to promote industrialisation such that everyone has “everything we have, and more”) can avoid apocalyptic scenarios. On the other hand we know without any doubt whatsoever that the only long term future for mankind is one based on sustainable energy production. I’d like to know why you don’t consider it appropriate to consider the latter.
  2. How do we know CO2 is causing warming?
    Riccardo #86 You wrote"You should consider the background (the parts of the spectrum where there is no absorpion) and the absorption peaks separately. Indeed, they are due to different processes: the former is an emission process and is related (among other things) to temperature, the latter is an absorption process and is related to CO2 concentration." Thanks for this. I am in learning mode. If I consider a very simple model of completely constant solar irradiation, an Earth in radiative balance with constant albedo, and I perturb the system by throwing in additional CO2 and then allow the system to re-establish radiative equilibrium, then I would expect that integrating across the resulting TOA emission spectrum to obtain total outgoing flux should yield by definition a value equal to the (constant) incoming solar flux. If one finds a dip in flux at the principal frequencies of CO2, then it must be compensated by an increase in other parts of the spectrum for the integral to balance. The Harries papers appear to show a net reduction in flux over the bandwidths examined and a large dip at the absorption frequencies of CO2 and methane (author's comments on the problem noted). My confusion is arising in part because I would not automatically expect to see a dip in TOA emissions at the CO2 frequencies. (The increased path length should slow down radiative transfer at those frequencies, but yield the same number of photons and the same net flux at top of atmosphere (TOA). I would expect the flux to be the same or even marginally higher because of the increased emissive presence of CO2 in the drier upper atmosphere (Kirchoff?). My question can then be summarised as follows: if there is in reality a net loss of flux at the CO2 frequencies at TOA, where do you expect to see the compensating gains in the rest of the spectrum and WHY?
  3. How do we know CO2 is causing warming?
    Thanks Tom! I will study all this and get back to you.
  4. How do we know CO2 is causing warming?
    Henry Pool, I linked specifically to section 1, Primer and History. In that section, the third figure from the top is a greatly simplified diagram of incoming and outgoing energy. Regarding your comment 87: "Page 9": Al Gore did not analyze ice cores. Al Gore is not a scientist. He just does a good job of educating people about scientists' research. You wrote:
    So when there is more volcanic activity, should we not expect a temperature rise? There is an awful amount of heat released when volcanoes explode. So that explains that correlation.
    No, it doesn't; see the "Skeptic Argument" list at the top of this page you are reading right now? That's where you'll find a response to the argument It’s volcanoes (or lack thereof). You wrote:
    Page 7: Why always measure carbon dioxide at Mauna Loa - so nearby an active volcano? Are there no other places? The graph does not have 0 ppm on, so it gives a bit of an extra slope upwards that should not be there.
    In fact, CO2 is measured in lots of other places; one list of the locations and ways of measuring is at the web site of the Carbon Dioxide Information Analysis Center at Oak Ridge National Laboratory. Mauna Loa is the most frequently listed when a short, simple explanation is the goal, because it is one of the most pristine and continuously measured sites, and its values well match the average of all the other sites. As for the graph's lack of a 0, in fact that is completely inconsequential--literally, inconsequential--with regard to the slope. Maybe you're confused because you think what matters is how sloped the line looks to the human eye. But in fact the visual appearance is irrelevant, because the statistics describing the line are what are actually used. You wrote:
    Page 6: Almost 100 years ago, Svante Arrhenius predicted that carbon dioxide in the atmosphere would cause warming up. In the meantime, carbon dioxide has increased even more than he expected, but the Earth hasn't warmed as much as he thought it would (applying his formula). Why did no one check his eperiments with modern day equipment?
    It seems you are not really reading the material, but only skimming very superficially. This very page you are reading right now is filled with exactly that modern, empirical, evidence. Maybe what you're wanting is something like The Carbon Dioxide Greenhouse Effect section of Spencer Weart's history of The Discovery of Global Warming. You wrote:
    It seems to me what they did in the IPCC report is to compare the concentrations of the gases in 2005 with 1750. Then they assigned a measure of relative radiative forcing to the so-called greenhouse gasses depending on the increase in concentrations measured. But this is like working at the problem from the wrong end! That is assuming that you are 100% sure what the cause is (of global warming) and then trying to work your way backwards to find a solution to the problem. They took all the gases that absorb infra red as positive forcing. "This must be the cause, what else can it be?"
    No. That's what this entire post by John Cook is about. Read it again. Click on the links he provides to his earlier posts. Don't just skim. You wrote:
    So here is how best to describe the greenhouse effect:Where we have absorption the molecule can except one or two photons from the radiation (and it gets a little warmer), but once this transaction is completed the molecule at that frequency becomes sort of like a mirror: it blocks any further radiation forcing it backwards to where it came from. It cannot allow the radiation to pass through anymore. Don't make it more difficult or confusing than what it is.
    You are incorrect. It does not block futher radiation. It is not in any way like a mirror. That's just not how it works. Really. See The CO2 effect is saturated. If you want a detailed explanation, start with A Saturated Gassy Argument and then read its Part II: What Angstrom Didn't Know. You wrote:
    So my question to all the scientists who worked on this problem is still the same: what is nett effect? How were the tests done to determine that the warming effect of carbon dioxide is greater than its cooling effect? Where are those figures?
    The answers to those questions have been right in front of you all along. That's what all these web sites describe. The empirical measurements described in John Cook's article at the top of this very same page you are reading right now, have been used to find the net effect. The diagrams of the Earth's incoming and outgoing energy show exactly those factors, with the resulting net effect--the Earth's "energy balance." (A more detailed diagram is in the IPCC's FAQ 1.1. See the Skeptical Science article Measuring Earth's Energy Imbalance.
  5. How do we know CO2 is causing warming?
    Henry Pool, you jumped off science all in a while; indeed, you're inventing a new one. I stick on the good old one and there's no answer I can give you. But i don't want to be told that i do not motivate what i say, i'll give you a few example. Just a few, going through all of them is not worth the effort. Page 9: correlation between volcanoes emissions and glacial cycles. Blatantly false, look at the numbers of CO2 emission from volcanoes; and also at how the earth orbit works. Page 7: CO2 measured only at Mauna Loa. Ridiculous, there are stations all over the world. Ad the slope of a curve is its first derivative whatever the axis you choose, it's just a metter of showing or hiding something. Page 6: the very same Arrhenius experiment has been performed countless times. We now know the abosrption coefficient with great precision over several order of magnitudes. Page 3-4: the picture you give of the basics of spectroscopy (you used this word) are naive. Two photon processes, "act like a mirror", come on ... i'm making it as difficult as it is in any standard undergraduate textbook. And so on, and on, and on ... But I can answer to the simple question "what is the net effect?": no matter which freak processes you immagine are at play, it's warming, no doubt.
  6. How do we know CO2 is causing warming?
    PS: Sorry Tom, I did not understand you here: "Take special note of the third figure" - what figure were you referring to? I did not see anything in this paper like that.
  7. How do we know CO2 is causing warming?
    OK, Let us take Tom's paper "(The Global warming debate") and work it through backwards to front. pages: 10-13: there is no doubt that global warming is happening. I do not doubt it. Page 9: ice core analysis:Al Gore and them apparently analysed ice cores going back to as far as 650000 years. Then they said, and I quote (from the movie): " whenever the carbon dioxide was higher the climate was warmer." So I asked myself: but why were there periods in history (before man and any kind of major human activities) when the carbon dioxide was higher? Well, where does all carbon dioxide come from? It comes from volcanic activities! That is why life came into existence. Water and carbon dioxide are like our father and mother. So when there is more volcanic activity, should we not expect a temperature rise? There is an awful amount of heat released when volcanoes explode. So that explains that correlation. Page 7: Why always measure carbon dioxide at Mauna Loa - so nearby an active volcano? Are there no other places? The graph does not have 0 ppm on, so it gives a bit of an extra slope upwards that should not be there. Page 6: Almost 100 years ago, Svante Arrhenius predicted that carbon dioxide in the atmosphere would cause warming up. In the meantime, carbon dioxide has increased even more than he expected, but the Earth hasn't warmed as much as he thought it would (applying his formula). Why did no one check his eperiments with modern day equipment? Anyway, it appears to me that subsequent followers have always assumed that his theory must have some truth in it. Eventually, the whole theory really became something like this: let us have a planet, add more carbon dioxide, see if the temperature goes up, it did, so that must be it! I also studied the IPCC report. It seems to me what they did in the IPCC report is to compare the concentrations of the gases in 2005 with 1750. Then they assigned a measure of relative radiative forcing to the so-called greenhouse gasses depending on the increase in concentrations measured. But this is like working at the problem from the wrong end! That is assuming that you are 100% sure what the cause is (of global warming) and then trying to work your way backwards to find a solution to the problem. They took all the gases that absorb infra red as positive forcing. "This must be the cause, what else can it be?" Page 5: The beaver story can apply to other possible causes - I touched on one possible other cause for global warming in my post at 80. Page 3-4: The graphs are familiar, they are the same ones that I have been referring you to before. Do place these two graphs on top of one another. Now for example: Look at the absorption of oxygen and ozone at 10 um. At this wavelength there is no absorption coming from either the water or carbon dioxide. Can you see that this absorption at 10 causes a dent in the radiation at 10 coming out from earth? So here is how best to describe the greenhouse effect:Where we have absorption the molecule can except one or two photons from the radiation (and it gets a little warmer), but once this transaction is completed the molecule at that frequency becomes sort of like a mirror: it blocks any further radiation forcing it backwards to where it came from. It cannot allow the radiation to pass through anymore. Don't make it more difficult or confusing than what it is. Page 2: the solar Radiation graph is very important. I have a slightly better one that goes a bit into more detail. The explanation given on page 2 is very poor. Let me re-write this a bit: The top of the yellow is the radiation what has been measured above the atmosphere (it follows a lobsided curve). The top of the red is what was measured at sea level on a clear day. The difference (=yellow surface area) is the radiation that was either absorbed (i.e. turned into heat), reflected (or 'blocked") or scattered by the atmosphere before reaching the surface of earth. The gaps (= yellow surface area - I refer to this as cooling or the anti greenhouse effect) are caused by the combined efforts of ozone, oxygen, water and carbon dioxide. So the same gases that cause the greenhouse effect are also causing the cooling (or anti greenhouse) effect. Without it, even more radiation from the sun would be slammed into heads and into our oceans. Note that the absorption of a molecule at a certain wavelength does not have to be strong to cause a blocking or "mirror" effect.The width is important. So now let us look at the absorptions of carbon dioxide together: Cooling: We have the first absorption at 1.4um.It shows a blocking effect (= yellow surface) on my graph. We have a 2nd absorption at 1.7 or 1.8 um. It shows a blocking effect (= yellow surface) on my graph. We have another absorption at around 2 um. It shows a yellow area being caused in my graph and your graph of page 2. We have another absorption of carbon dioxide at just before 3 - it shows a cooling effect (i.e. yellow surface area) on my graph We have strong absorption between 4 and 5 um. It falls of the scale on both (solar radiation) graphs, but we know that between 4 and 5 um there is still about 0.5% radiation coming from the sun (according to my table). We now go to warming (greenhouse effect) We have strong absorption between 4 and 5 um. It appears that a little bit of earth's radiation is being blocked by this but the spectral intensity of earth is still low between 4 and 5. There is strong absorption at 14-15. It leads to some of earth's radiation not being emitted. Note that oxygen also has a very weak band here and water also absorbs here. These 2 gases have much higher concentrations than carbon dioxide so it is difficult to see or know exactly what the influence of the carbon dioxide on its own. So my question to all the scientists who worked on this problem is still the same: what is nett effect? How were the tests done to determine that the warming effect of carbon dioxide is greater than its cooling effect? Where are those figures?
  8. What does past climate change tell us?
    "Ironically, when skeptics cite past climate change, they're in fact invoking evidence for climate sensitivity and net positive feedback. Higher climate sensitivity means a larger climate response to CO2 forcing. Past climate change is actually evidence that humans can affect climate now". No, large climate response to CO2 doesnt necessarily follow from higher climate sensitivity. Note that skeptics agree with high climate sensitivity (eg ice ages as a result of small solar/orbital changes etc), they just think that c02/greenhouse gases are not a major part/factor in it, ie they think greenhouse gases are being articifially enhanced in past (and present) climate analyses(largely as part of an agenda). EG. Please explain how c02 was up to 5000ppm in the Jurassic and there was no significant change in earth temperatures/runaway greenhouse?. (the argument on this site earlier of c02 'thresholding' for various periods in earth climate history is weak, because you could just as well say the earth has 'c02-thresholded' now in its current climate state).
    Response: To answer your question re higher CO2 levels in the Jurassic, during this period, solar activity was also lower than current solar levels. The combined effect of sun and CO2 matches well with climate.
  9. Working out climate sensitivity
    Re #8: No, it just means that hotter things give off more heat, which is the answer to your second question in #2.
  10. Working out climate sensitivity
    PaulK, it's not an a priori assumption; it is consistent with at least three thing (the first three i can think of :) ) 1) it's consistent with what is known on paleoclimate 2) it's what you expect in a strongly coupled system 3) this behaviour is reproduced in climate models Having said this, it's clear that it's just a usefull aproximation with a limited range of validity to compare different forcings.
  11. How do we know CO2 is causing warming?
    PaulK, I'll give my take assuming i understood your question correctly. You should consider the background (the parts of the spectrum where there is no absorpion) and the absorption peaks separately. Indeed, they are due to different processes: the former is an emission process and is related (among other things) to temperature, the latter is an absorption process and is related to CO2 concentration. As for the background, it is a blackbody-like emission and is contaminated by various effects (listed in the paper). In principle, it is expected to increase with warming, as you correctly say. As for the peaks, you expect more absorption as CO2 concentration increases (roughly independent on temperature for small increases) and then a reduction of the intensity reaching the detector. Here, instead, you apparently think in term of emission as well and then expect an increase.
  12. Working out climate sensitivity
    Regarding Lindzen/Choi: "Increased ocean temperatures do increase the amount of radiation lost to space - if the Earth is in positive energy imbalance, the planet will accumulate heat, oceans will warm, the earth will radiate more energy to space until it approaches radiative equilibrium again. This is discussed in more detail in the Climate Time Lag post. ]" Does that mean that Lindzen/Choi is correct when they calculate sensitivity to be 0.5 degrees C?
  13. Does model uncertainty exagerate global warming projections?
    The graphic posted above is entertaining but does not reflect the possiblity of a negative feedback effect. Lindzen (2009) deduces a negative feedback from empirical observation (OLW vs DeltaT). The Dessler and Zhang paper deduces a negative feedback based on a two point comparison (in a period of decreasing temperature), but uses a model-derived kernel of flux derivatives to support the conclusion, making the argument somewhat circular. What other empirical evidence is there to counter Lindzen's argument?
    Response: Here is a summary of empirical evidence for positive feedback systems. Here is a summary of the peer reviewed literature on net positive feedback (aka climate sensitivity).
  14. Working out climate sensitivity
    I would ask a simple question: why is there an assumption that all forcings should result in the same climate sensitivity? At the simplest level, I could suggest that if a large part of a change in TSI is absorbed as additional (UV absorbed) energy in the stratosphere, and an internal forcing results in ocean heat release and hence cloud formation, and a GHG forcing results in an increased pathlength for photons riding a CO2 principal frequency, then why shold we assume that the power to temperature ratio is the same for all three?
  15. How do we know CO2 is causing warming?
    Thanks to all for this blog. I am grateful for finding it, in that it appears to be able to accommodate dissenting views without immediately resorting to abuse and non-sequiturs. I read the series of Haries papers, and have a serious question about the interpretation of the results. I should first of all offer my congratulations to the succession of authors who have heroically tried to reconcile and calibrate three different datsets into a meaningful composite comparison. My question is this: if it is CO2 causing the warming why would one expect a signature that shows a dip in OLW flux at peak CO2 frequency and an overall reduction in the MODTRANS integral of emissions? My understanding of the theory of AGW was that increasing CO2 should slow down emission at the principal frequencies of CO2 and increase the temperature at TOA to bring the radiative balance back into equilibrium. This suggests that the integral should be about greater over the period measured after 27 years of temperature increase, rather than reduced as the graph implies. It further suggests to me that the radiation at CO2 principal frequencies should be increased rather than reduced, since under the "saturated gassy argument" we should have more CO2 in the upper stratosphere - implying greater emission at the principal frequencies. Can anyone clear up my confusion here? On a separate point, it seems to me that we should now have several years of high quality satelite data across a broad frequency band. Why have we not yet seen a "3D picture" showing 2-D waveband vs time and temperature. This would surely help to close the conversation one way or the other?
  16. How do we know CO2 is causing warming?
    Henry Pool, your terminology definitely confuses me. I can not understand what an anti-greenhouse effect is nor what you mean by "blocking" or absorption or "mirror". Also some concepts appear to be messed up. You say "But now for you to say to me that the radiation from the sun that is being "blocked" by carbon dioxide is irrelevant surely is the same as saying that the greenhouse effect is irrelevant?" Can you see any difference between the light coming from the sun and the radiation coming from the earth surface and atmosphere? Also reflection, scattering and absorption appear to be used out of context. Probably following Tom Dayton advice is the best you can do.
  17. How we know global warming is still happening
    Chris, the trouble with these arguments is that they rapidly get much too detailed for me to debate effectively in the time I have available. Your position holds together fairly well for now, but will become tricky if the temperature stasis lasts for too much longer(if it does, then you will be forced to grant more power to natural variations than you have been willing to do so far). "These observations are not surprising shawnet; the movement of waters around the world simply cannot “magic” heat generation, even if they can redistribute this due to long term oscillatory shifts in currents. " The movement of water may not be able to generate heat, but it will definitely allow it to be dissipated and radiated more or less efficiently. Think about it.
  18. How do we know CO2 is causing warming?
    Henry Pool, regarding the net of reflection and absorption, try reading cce's section 1, Primer and History. Take special note of the third figure. If you want to dig deeper, look at the references listed for those figures.
  19. Working out climate sensitivity
    re #4 HumanityRules, you've done an interesting bit of quote mining, but it doesn't really reflect current understanding. In relation to your highlighting some papers on solar contributions to early 20th century warming, it's useful to know that in the 10 years since the work cited in your quote (from the Introduction to Andronova and Schlesinger (2000) Geophys. Res. Lett. 27(14), 2137-2140), that there has been a significant reassessment of solar irradiance changes as indicated from a number of methods. The contribution of solar irradiance to early 20th century warming is small (of the order of 0.1 oC or less). This is taken into account in more recent analyses of climate sensitivity and is likly part of the reason that the low end of the climate sensitivity is rather better constrained now than in the past, as indicated in John Cook's summary: see for example: Wang YM, Lean JL, Sheeley NR (2005) Modeling the sun's magnetic field and irradiance since 1713 Astrophys. J. 625, 522-538. http://www.iop.org/EJ/abstract/0004-637X/625/1/522/ Krivova NA, Balmaceda L, Solanki SK (2007) Reconstruction of solar total irradiance since 1700 from the surface magnetic flux Astron. Astrophys. 467, 335-346 Lean JL, Rind DH (2008) How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006 Geophys. Res. Lett. 35, L18701 http://www.agu.org/pubs/crossref/2008/2008GL034864.shtml Benestad RE, Schmidt GA (2009) Solar trends and global warming J. Geophys. Res. 114, D14101 http://www.agu.org/pubs/crossref/2009/2008JD011639.shtml Steinhilber F, Beer J, Frohlich C (2009) Total solar irradiance during the Holocene Geophys. Res. lett. 36, L19704 http://www.agu.org/journals/gl/gl0919/2009GL040142/
  20. How we know global warming is still happening
    It's not about what people think, shawnhet; it's about what the evidence shows. And now you're changing the point into vague generalities and allusion. If we can assess in quite a bit of detail the attributions to 20th century warming (see posts 77/79), why shift the argument to other periods where these are less accessible (MWP to now)? That sounds like an attempt to take the argument back into a comfortable uncertainty where misrepresentation and conspiracy theorising thrives. As for "anomalous jump in temperature in ~ 1976", that turns out to be an artefact of a set of expendable bathy-thermographs (as identified for example, by the Willis that you mention in your post [*]), and described recently by Domingues et al [**] and subsequently others. It’s got nothing to do with the PDO. [*] Wijffels SE, Willis J, Domingues CM (2008) Changing Expendable Bathythermograph Fall Rates and Their Impact on Estimates of Thermosteric Sea Level Rise J. Climate 21,5657-5672 [**] Domingues, CM et al (2008) Improved estimates of upper-ocean warming and multi-decadal sea-level rise Nature 453, 1090-1094
  21. How do we know CO2 is causing warming?
    Quote from Wikipedia (on the interpretation of the greenhouse effect); "The Earth's surface and the clouds absorb visible and invisible radiation from the sun and re-emit much of the energy as infrared back to the atmosphere. Certain substances in the atmosphere, chiefly cloud droplets and water vapor, but also carbon dioxide, methane, nitrous oxide, sulfur hexafluoride, and chlorofluorocarbons, absorb this infrared, and re-radiate it in all directions including back to Earth." Because of the random position of the molecules we may assume that at least 50% of the infra red from earth is radiated back to earth. The process repeats itself. Did you have a close look at the graphs (web link) that I posted in 67? You can clearly see that the greenhouse efect is relevant for carbon dioxide at about 14 um. But water absorbs there as well. But note that there is also an anti greenhouse effect - especially at between 2-3 um and between 4-5 um where we still have the sun's radiation. Interestingly at between 4-5 we also have some radiation from earth.So it looks to me these two cancel each other out. But it seems you still do not understand. For example: Look at the absorbtion of oxygen and ozone at 10 um. At this wavelength there is no absorption coming from either the water or carbon dioxide. Can you see that this absorption at 10 causes a dent in the radiation coming out from earth? You can say the ozone/oxygen is "blocking" (mirror?) some of the radiation going out from earth at 10. That is why even oxygen and ozone are greenhouse gases. But now for you to say to me that the radiation from the sun that is being "blocked" by carbon dioxide is irrelevant surely is the same as saying that the greenhouse effect is irrelevant? Both are relevant. But what is the nett effect? Is the cooling more or is the carbon dioxide warming more? I am not interested in what a lot of people are saying or thinking. I am only interested in what I can see is happening. Please try to understand my thinking here and make a big print-out of that weblink that I gave in 67, I am sure you will begin to understand what I am saying when you follow the example that I gave with the gap in the radiation from earth at 10 um caused by the oxygen and ozone absorption at 10.....
  22. Working out climate sensitivity
    A few general comments on Lindzen and Choi paper. The paper, in the first part, focus on the comparison between ERBE data and model predictions. The simulations used were taken from the AMIP project which are atmospheric only GCM with prescribed sea surface temperature. The goal of the project is model intercomparison, not state of art simulations of real climate for which a fully coupled AOGCM is required. Hence the use of AMIP models is at least questionable. Another weakness of the paper is the use of ERBE data for the tropical latitude band to infer a global climate sensitivity. This is aknowledged by the authors themselves in the conclusions. Finally, there are already many different values of the climate sensitivy in the scientific litterature, as clearly pointed out in this post. Only rarely a single piece of work makes huge differences. So, scientifically this work should be first confirmed and then compared to other data and pluged in the big picture; and I'm sure this is exactly what the science community will do. People should then refrain from simply stating that the climate sensitivy is half the accepted value.
  23. How do we know CO2 is causing warming?
    Henry Pool, the lifetime of the excited state is very short, expecially at high temperature and pressure. There is no significant "mirror effect" (sic) at all. What is true, instead, is that the photon might be re-emitted at the same wavelength, but it's too simplistic to assume that it's irradiated back to space. You need to consider the atmosphere as a whole so the chances that the photon gets re-absorbed are high near the ground and progressively reduce going up. And here comes the concept of which i wrote a few comments back; it's the altitude at which the photons might actually escape to space that matters for the energy balance. You might want to read a little bit more on this in a standard climate textbook (e.g. Principles of Planetary Climate available online). Be sure that there's lot people around able to take all of this into account ;)
  24. How do we know CO2 is causing warming?
    Hi Riccardo, I refer to my post 73. Please read this first. It seems there is a general misconception about the term absorption. Absorption is a term that came from spectroscopy. What happens is that that at these wavelengths where absorption occurs, one or two photons are accepted. What then happens (at these wavelengths)is that the molecule turns into a mirror and the rest of that radiation (at these wavelengths)is then re-emitted. Because of the random position of the molecules you may assume 50% beamed back to earth or back to space, depending on where the radiation came from in the first place. Now there is a limited amount of carbon dioxide (i.e. ca. 350 ppm) in the air, so it not possible for that much "energy" to be taken up before it starts re-radiating. See the definition of the greenhouse effect in Wikipedia. This may be unlike the oceans and the seas. There is virtually an unlimited amount of salts that may be able to accept photons. And on a macro scale humans are busy taking water from the oceans (rain), collecting it in dams and using it up for irrigation and consumption.. What flows back into the seas might even have more salt than the oceans.....
  25. Working out climate sensitivity
    Some issues. Hansen 1993 - This is a National Geographic publication? Not peer-reviewed? I can't access it as a journal thru my university. I've nothing against non-peer review but it is often a stick used to beat 'deniers' quote from this article "you get a clearer idea of our understanding of climate sensitivity by perusing the whole range of peer reviewed scientific literature on the subject." hegerl 2006 in their abstract "A number of observational studies3–10, however, find a substantial probability of significantly higher sensitivities, yielding upper limits on climate sensitivity of 7.7K to above 9 K (refs 3–8)." Looking at some of these references (often written in less politically ardent times) you get the following quotes more quotes from hegerl "The dominant uncertainty in the calculation of climate sensitivity is clearly that pertaining to the estimates of radiative forcing" radiative forcing is the mechanism most strongly accosiated with climate change from CO2? "Improved understanding of physical processes of climate change and refinement of climate models is essential to reducing uncertainty in climate prediction." Speaks for itself. and from some of hegerls references "Recently Tett et al. [1999] found the increase in global mean near-surface temperature during the first half of the twentieth century may be due to variations in the sun's irradiance. This supports the earlier findings of Kelly and Wigley [1992] and Schlesinger and Ramankutty [1992]; further support is provided by Marcus et al. [1999], Drijfhout et al. [1999] and Beer et al. [2000]." I wonder if you include those 6 sun irradiance papers in your 'whole range of peer reviewed scientific literature' "Radiative forcing is the greatest source of uncertainty in the calculation; the result also depends somewhat on the rate of ocean heat uptake in the late nineteenth century, for which an assumption is needed as there is no observational estimate." "climate sensitivity......is estimated to lie between 1.5 and 4.5K (Cubasch et al. 2001), largely on the basis of experiments with general circulation models (GCMs)." This wikipedia entry en.wikipedia.org/wiki/Satellite_temperature_record discusses some "potentially serious inconsistencies" with these models many of the papers are also full of words like assumption, maybe and uncertainty. Yet you seem to go to definite statements based on these papers. Remember all these quotes come from the climate change science papers not deniers.
    Response: I gleaned two "take-homes" from Hegerl's paper:
    1. Despite the many determinations of climate sensitivity, there hasn't been much progress in constraining the likely values - it's gone from initial estimates of 2 to 4°C to current estimates of 2 to 4.5°C. You call that progress?! A large part of this is uncertainties associated with radiative forcings, as you point out.
    2. At least there has been progress in constraining the lower bound being very likely greater than 1.5°C. Anything over 1.2°C. indicates the climate has net positive feedback.
    It's interesting you should mention the uncertainty with radiative forcing in relation to CO2 forcing - I will be posting on that very subject in the next post.

    Re the sun irradiance papers, I'm fairly confident they would be included in the 'Instrumental Period' results but feel free to check this out yourself (and report back please). We examine elsewhere the role of the warming sun in the early 20th century.
  26. What does past climate change tell us?
    @Chris #25 In response 1. False Logic Medical clinics are meagre and have no drugs not because of global warning. Infrastructure is poor not because of global warning. People earning next to nothing not because of global warming. Child mortality is not because of global warming. These are the real problems I am concerned with now. There is no false logic in worrying about real issues rather than being alarmist about future problems. I thought it was a fact that that region of the world does produce sufficient food to feed itself and has the potential to produce more it's the complicated (and screwed) relationship it has with the global economy that has kept that region in the state its in. Nothing about it's past, present or future climate. 2Crocidile tears I have no problem with your first paragraph, I totally agree. I've been an active anti-imperialist most of my adult life. But I don't see the jump of going from blaming the west and it's institutions to giving them cheap solar panels. Imperialism has thru the ages changed but it has always been morally justified. The civilizing of the savage argument came to look out-dated and racist after the war but during the 19th centuary was absolutely mainstream, as you say the more recent IMF/world bank form of fiscal imperialism played on the protection of the african people from their corrupt leaders. My worry is the next moral reasoning for western control of the poor will be environmental protection. It does appear one country is breaking the mould in Africa. China is doing what has never really been done investing in infrastructure. It's big, dirty and has a high carbon footprint but it has the potentially of shifting some african countries into the industrialized world. Many african commentators see this as preferrable to either western conservative fiscal control or western liberal charity. You can give african villages free solar panels. I aspire to see them have everything we have, and more.
  27. Working out climate sensitivity
    djb95054, Increased ocean temperature absolutely increases the amount of radiation emitted by the oceans. According to the Stephan-Boltzmann Law the energy emitted across all wavelengths by a black body increases as the 4th power of the temperature. A portion of this is lost directly to space out what is called the infrared window where greenhouse gases do not intercept the radiation, while a much larger portion is absorbed by the atmosphere. Thus, warmer ocean's maintain a warmer lower atmosphere which expands due to the added warmth. The layer of emissivity, where Earth's effective temperature of 255K is met, reaches to greater height where the radiation balance between incoming and outgoing radiation is attained, no extra energy is lost from there. So, most of the additional energy emitted by a warmer surface (oceans) goes to warming the atmosphere to higher temperature, while an increased but much smaller amount is lost out the atmospheric infrared window.
  28. How do we know CO2 is causing warming?
    Henry Pool, you have to consider the different wavelength range in the two cases. In the visible range (sunlight coming in) the CO2 effect is definitely negligible, there's no significant absorption nor scattering. No cooling, as you call it. As for the radiation coming from the earth surface (infrared going out), there's no significant scattering as well but there's absorption (at certain characteristic frequencies). Again, no cooling. More generally, as in the case of aerosol, you can have a net cooling effect due to the combined effect of absorption and scattering. But this is a much more complicated matter and infact is the biggest single contribution to the uncertainty in the estimates of the total net forcing.
  29. Working out climate sensitivity
    What about the latest study by Lindzen/Choi (see http://climaterealists.com/index.php?id=3932) that pegs sensitivity at .5 degrees C? Is there any validity to the theory that increased ocean temperatures increases the amount of radiation that is lost to space?
    Response: Increased ocean temperatures do increase the amount of radiation lost to space - if the Earth is in positive energy imbalance, the planet will accumulate heat, oceans will warm, the earth will radiate more energy to space until it approaches radiative equilibrium again. This is discussed in more detail in the Climate Time Lag post.
  30. How we know global warming is still happening
    Chris, all of the issues involved are massively complex, so it is easy to find people on different sides of any issue. If you want to assume that anyone who agrees with you must be right and anyone who disagrees with you wrong, that's fine. The fact remains that many people feel that PDO shifts have the capacity to accelerate or deccelerate the warming trends. If this is true, then the fact that there are (essentially)two PDO warming periods and one PDO cooling period in the last 100 years must reduce the anthro contribution to warming. One does not have to accept that the PDO can change the rate of warming, of course, but this leads to its own problems (like the anomalous jump in temperatures in ~1976). It is widely supported including by Josh Willis(who is no stranger to ideas of OHC). There are other comparisons one could make of course, to try and guage the natural component of climate change. Comparing the temperature now to the temperature at the height of MWP or comparison of temp change(or sea level increase) from 1800-1900 and 1900-2000 or of the rate of temp change from 1910-1945(the previous positive PDO period) to the 1976-2000 period). "These observations are not surprising shawnet; the movement of waters around the world simply cannot “magic” heat generation, even if they can redistribute this due to long term oscillatory shifts in currents. " The movement of water may not be able to generate heat, but it will definitely allow it to be dissipated and radiated more or less efficiently. Think about it.
  31. How do we know CO2 is causing warming?
    Yes Riccardo!- I am glad you understand. I am talking about both directions. The cooling is coming from the top to the bottom, the warming is going from the bottom to the top, or rather, from the bottom up back to the bottom - i.e. the greenhouse effect!! Your argument that carbon dioxide is a "small particle" surely applies both ways. i.e. both for earth and the sun. I therefore would like to see the actual figures or measurements from experiments -do you have them? What is the nett result of the cooling and the warming effect of CO2??
  32. What does past climate change tell us?
    I'd like to respond to Humanity Rules. First, I don't think we need cheerleaders on a science blog. That's a comment on your net name, but it's also a comment on your attack on John Cook. You say that in 17, John "hold up the Sub-saharan life as the way forward for humanity". I don't think he does any such thing. I think he merely points out that human population by itself doesn't increase CO2 content of the atmosphere -- that requires liberation of fossil carbon (as Ricardo makes clearer in 22). It's really very simple: CO2 added to the biosphere = (human population) x (environmental consumption per capita) x (CO2 emissions per unit of environmental consumption). So you could say that CO2 added to the biosphere = (N x E x C). To limit increases in atmospheric CO2, it doesn't matter if you manage to reduce population (N) by 20%, per capita consumption (E) by 20%, or CO2 required to provide that consumption (C) by 20%. If you hold the other two components constant, then you end up with a 20% overall reduction. But, one must be aware that these components interact in a complex manner, and focusing on one of them (especially a difficult one, like population) will likely not result in the CO2 limitation one might have simply imagined (China's population didn't stop growing via one-child policy; their CO2 production went up greatly at the same time). Nobody here is advocating "back to the stone age" policies, so please leave that rhetoric at home.
  33. How we know global warming is still happening
    come on shawnet. You've just been demonstrating that one can fabricate the pretence of a "debate" by saying "stuff" for which there isn't any evidence! In fact there actually isn't much scientific debate about the attribution of natural and anthropogenic factors to 20th century and contemporary warming....the scientific evidence from a number of different analyses (see for example my post #76) indicates that the natural contribution is small and the anthropogenic contribution is large. I prefer to follow the science on these issues. Your "simple argument" is meaningless, isn't it, without recourse to evidence. There has been significant scientific investigation of the contribution of ocean current regime shifts on the 20th century temperature trend. The evidence indicates that the nett effect is unlikely to have been much above zero, despite the fact that these effects have likely modulated the time course of warming significantly. For example Swanson et al, who have addressed this exact question, find that while ocean current effects have modulated the pattern of 20th century temperature, the nett warming contribution has been negligible (well below 0.1 oC). Lean and Rind (cited in my post above) find much the same. These observations are not surprising shawnet; the movement of waters around the world simply cannot “magic” heat generation, even if they can redistribute this due to long term oscillatory shifts in currents. Swanson KL, Sugihara G, Tsonis AA (2009) Long-term natural variability and 20th century climate change Proc. Natl. Acad. Sci. USA 106, 16120-16123 Rather than use a form of Aristotelian syllogism where you choose the conclusion you desire and bind this into a “logical” “argument” based on false premises (the Shaviv chap you keep referring to does this too), it really does help to look at the evidence. Apart from the abundant science that informs us of these issues, I find it rather compelling that even though we’re apparently within a cooling ENSO regime (your PDO shift which your hopeful guess gives “0.2-0.25 oC” of cooling), and the sun is smack at the bottom of a rather extended solar minimum (which according to your mate Shaviv should give a highly amplified cooling!), we’ve had the warmest September on record [*] and the second warmest June-July-August on record [**]. Of course one can’t draw major conclusions from short time periods, but our current global temperatures are well above the 1990’s average [*,**]. So where’s the marked cooling that your (and Shaviv’s) syllogism is attempting to trick us with? [*] http://www.cru.uea.ac.uk/cru/data/temperature/crutem3vgl.txt [**] http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts+dSST.txt
  34. Working out climate sensitivity
    The caption for Fig 1 is confusing: how could the thicker bars represent higher integrated probability than the thin bars (which cover a broader range)? Surely it's the narrower range that is "likely" and the broader range that is "very likely". I also find interesting the circles for the most likely value. Instrumental record, last millenium proxy, and combined lines of evidence are less than 3 Celsius; only general circulation models indicate more. So it's hard to see why the IPCC point estimate is 3 C rather than, say, 2.8 C (like for "combined lines of evidence"). Finally, it's interesting to see that "expert elicitation" gives exactly the same likely range as IPCC (I don't really see how they would differ) while surely with several estimates producing similar ranges the confidence in that range should increase (and thus the narrow bar for "combined lines"). And finally, er, really finally, I think we must be over 384 ppm in CO2 equivalents now. Just CO2 was 385 ppm http://tinyurl.com/yz783a9 so I imagine adding anthropogenic methane and such would push us to ... maybe 395?
    Response: The caption for Fig 1 was confusing because it was wrong - I've updated the text, swapping thicker and thinner. Thanks for pointing that out.
  35. What does past climate change tell us?
    HumanityRules, there's a strong dose of false logic combined with crocodile tears in the sorts of argument you are presenting. I’m not saying they necessarily apply to yours specifically, but they hint in that direction! 1. False logic. Large parts of sub-Saharan Africa are (and will continue to be) regions of the world that are most susceptible to the effects of global warming. It's established that the effects of global warming has produced increasing drought in these regions, and as warming progresses the region of reduced precipitation will spread Northwards and Southwards from the mid latitude bands already suffering from drought [*]. The global areas classified as "severely dry" by the Palmer Drought Severity Index (PDSI) more than doubled from 12% to 30% in the period 1970-2002 with surface warming as the dominant cause post-1980 [**]. This is the major cause of current, and near and medium-term food limitation that is the source of much of the problems in these and other areas in the middle latitude bands of the earth. The notion that this situation can be eased by beefing up the carbon footprint of these populations (and similarly low-carbon footprint populations elsewhere) is simply fallacious. What these increasingly drought-ridden regions need is a reduction in global warming. The obvious means of addressing this problem is to make a large investment in providing sustainable energy for these people, while we do the same for ourselves. This has to happen sometime (our civilizations are untenable into the future on the centennial timescale without this), and it should be happening with increasing urgency now (it is to some extent). [*] Zhang XB, Zwiers FW, Hegerl GC, et al. (2007) Detection of human influence on twentieth-century precipitation trends Nature 448, 461-465 [**] Dai AG, Trenberth KE, Qian TT (2004) A global dataset of Palmer Drought Severity Index for 1870-2002: Relationship with soil moisture and effects of surface warming J. Hydrometeorology 5, 1117-1130 2. Crocodile Tears One wonders where the concern for sub-Saharan Africa has suddenly sprung from! During the past 40-odd years this part of the world has suffered enormously from economic mismanagement a large extent of which was perpetrated by Western governments in support of their own economic advantage, largely in relation to extraction of raw materials. This encompassed major political interference in support of despotic or otherwise compliant leaders, and imposition of severely unfavourable trade and social conditions by the IMF/World Bank in which economic assistance was built around a system of enforced restructuring involving easing access of Western corporations to commodities and infrastructure, and dismantling of social structures. The World Bank ultimately admitted that it had caused huge social damage through these policies. That's happened and it can't be easily undone. However if we are truly concerned about those people (rather than using them for convenient hand-wringing in fallacious arguments to avoid doing anything about global warming), then we should address the problem directly. For example, cheap solar panels of the sort that China can producing in large amounts could be distributed, so villages could power fridges to keep medicines and run basic systems to power educational facilities and peripherals and so on. Major efforts to make local use of the abundant solar power in the central latitudes for more widespread industrial and social applications could be promoted. Properly planned programmes for sustainable biofuel generation in the so-far drought-free regions south of the equator could be developed…and so on. The notion that the well-being of populations can only be improved through burning fossil fuels is not only wrong...it's an admission of an essential futility of future progress.
  36. What does past climate change tell us?
    Thanks Philippe, So we're now moving into the cooling phase of the Milankovitch cycle correct?
  37. Philippe Chantreau at 03:00 AM on 23 October 2009
    What does past climate change tell us?
    Kevin, if anything the Earth would be cooling, if left only Milankovitch cycles. That would be a slow process though, leading to cold conditions within 25 to 50000 years.
  38. How do we know CO2 is causing warming?
    Henry Pool, my reasoning was upside down, the IR radiation leaving the earth surface. Instead, you're are talking about scattering of visible light from the sun, a completely different issue. No problem about Copenhagen, we can go safely. Scattering is a old and well known phenomenon. The intensity of the scattered light depends on the size of the partiicle and CO2 is quite small; on the contrary, water vapour tends to form liquid droplets (or ice crystals) which are several order of magnitude bigger than a single molecule. Hence droplets suspended in air scatter incoming sunlight much more efficiently than CO2 molecules, the latter being negligible. As a take away message, don't think scientists (and i'm not one of them) are not smart enough to account for the known physics.
  39. What does past climate change tell us?
    batsvensson, luckly the CO2 we release with respiration does not come from fossile carbon ;)
  40. What does past climate change tell us?
    RSVP, i'm sure you know the per capita emissions in poor country, what you say has not been confronted with reality. And it's worse than that, in what even in poor countries there are rich and the industrial system is much less efficient than ours (compare emission per unit GDP). And yes, global ecology is definitely a luxury as well as the possibility to plan a relatively far future. But this points in the very same direction, it's not over-population but over-consumption.
  41. What does past climate change tell us?
    As a non scientist I read your comments with great interest and would like to ask what many of you would consider rather basic question I'm sure. Another article I read on Skeptical Science dealt with Milankovitch cycles - how increased temperature causes CO2 rise. http://www.skepticalscience.com/co2-lags-temperature.htm So relative to this blogs emphasis of past change I would like to propose a hypothetical and hear your thoughts. The question: If we humans were not here, thus not pumping out C02, and when considering the Milankovitch cycles, would temperatures still be rising, albeit at a bit slower rate? As a non scientist I'm having a hard time quantifying what I've read, that warming started again in the late 19th century following the little ice age. Did the earth basically shrug off the short term effects of the little ice age during this period to begin its relentless march towards warming because of the Milankovitch cycle? If so, I would assume we humans are just juicing this effect now, but that it started before we contributed much C02? If this is the case, I would be curious hearing a hypothesis looking into the future of the difference where sea levels would be without humans versus with humans. Excuse my layman thinking!
  42. Empirical evidence that humans are causing global warming
    Correction to above "The clearest fig to my mind is Figure 3 from chen 2007"
  43. Empirical evidence that humans are causing global warming
    I also got a question about the (Harries 2001, Griggs 2004, Chen 2007) papers on radiation observations. The clearest fig to my mind is Figure 3. This figure is a subtraction 1970 radiation from 2006 data. I see the drip (negative values) in radiation at the wavelength for CO2 so energy at that wavelength is being retained more in 2006 compared to 1970. But I see positive readings at other wavelengths. My understanding would be that relatively more energy is being lost from the earth at those wavelengths in 2006 compared to 1970. Why is it possible to ignore the the energy at these different wavelengths and only focus on the wavelengths associated with CO2?
  44. What does past climate change tell us?
    "...poor people emit enormously less CO2 than rich" You probably will find your "poor" closer to template climates for starters. And for however closer they may be, they tend to burn and destroy more forests per capita than anyone on the planet. This does not make industrialized nations any less guilty, however, if anything is going to help us get through this it is science and technology. And to contrast human values, historically, one of the strongest incentives to having more children in these "poorer" countries is tied to a desire for more hands in the fields, while "global ecology" (if it even registers on the mental radar) is some strange luxury of the rich. Monboit's thesis is kin to the concept of the "nobel savage" of the 18 and 19 centuries.
  45. Empirical evidence that humans are causing global warming
    I can't find the "earth total heat content Figure 3 in (murphy 2009) are you referring to the paper "An observationally based energy balance for the Earth since 1950"?
    Response: Yes, the data from my Figure 3 (Earth's Total Heat Content) comes from the energy storage element of Figure 6b in "An observationally based energy balance for the Earth since 1950" (Murphy 2009). Dan Murphy very generously sent me his data.
  46. dopeydoctorjohn at 00:25 AM on 23 October 2009
    The growing divide between climate scientists and public opinion
    I discussed on the "there is no consensus" debate that the Doran paper comes to an invalid conclusion comparing the earth scientists views to that of the general public because the question asked of the earth scientists in the Doran survey was substantially different to the question asked of the general public in the Gallup poll. Undoubtedly most scientists in the field agree with the current dominant paradigm. Undoubtedly some do not. Sometimes the majority are wrong; but usually not. However, the Doran study is seriously flawed and tries to exaggerate the degree of consensus that exists. Because it does this clumsily and amateurishly, and is easily exposed with a little further research and thought, it actually undermines (rather than firms) belief in the consensus. There must be better "consensus" papers around than this. Regarding the extent to which there is a cultural dimension to science, I believe Kuhn's work was highly influential and some of the posters might like to have a look at it http://en.wikipedia.org/wiki/The_Structure_of_Scientific_Revolutions
  47. How do we know CO2 is causing warming?
    Yes, I am talking about the the radiation from the sun hitting on the carbon dioxide. A large portion of that radiation must be scattered away to outer space. You can observe same effect if you stand in the sun (here in Africa) - you will notice that the heat coming directly at you from the sun definitely decreases as the humidity increases. You can feel it. So, the same observation must be true for carbon dioxide. At all levels of the atmosphere. Notice (from the graphs) that at quite a few points the water vapor and carbon dioxide work together to keep us cool. I don't understand how we can go to Copenhagen with this and nobody studied what the nett effect is of the cooling and warming caused by the carbon dioxide. How do we know for sure that the warming effect is bigger if nobody did some experimentation on this? I don't think that temperature and pressure (have to)come into this at all? The CO2 is diffused in the air, therefore you can see it behaves the same as does oxygen.It keeps us cool (during daytime, 12 hours per day) and it keeps us a bit warmer (all of the time) but what is the nett effect?
  48. Empirical evidence that humans are causing global warming
    The OP claims that the if "Humans are raising CO2 levels" and "CO2 traps heat" and "our planet is accumulating heat" then the conclusion "human are causing global warming" must be taken under seriously considerations. The OP proves the premises, and then states the conclusion. But does that mean the conclusion is true? Not necessarily. Why? Because it is also equal true to that the conclusion from "If apples are fruits and there is no air on the moon and Mondays comes after Sunday then the moon is made of cheese" is true as well. That implication, plus an infinite many other implications of the same type, has exactly the same logical structure as the implication the OP has proven to be true. So what is wrong with the conclusion which the OP has present? First of all, the premises is only based on observational fact that are true, therefore the conclusion follow as a necessity but it doesn’t say anything about weather the conclusion is correct or not. Secondly the implication contains hidden assumptions, which turns out to be implications as well, which are assumed to be true – therefore unless this can be shown to be true the conclusion must be regarded as postulated by the OP. The hidden assumed condition is the strong statement "CO2 drive temperature changes". The question to ask is: did or did not the OP address this assumed statement? My answer to that question will be that the OP failed to address this assumed statement. The OP address a weaker a form of the strong statement that can be formulated as "CO2 level follows changes in temperature". The weaker form is very interesting because it makes us able to formulate testable hypothesis of the form "If CO2 level changes then temperature will change accordingly" which under certain condition is the same as the statement "CO2 drive temperature changes" as implication also are causal relation. Formulated this way we realize why the statement "CO2 drive temperature changes" is a much stronger statement than "CO2 level follows changes in temperature", this because the strong statement is in fact a law, while the weaker statement "CO2 level follows changes in temperature" is simply a matter of observing measurements. Now, if we can show this stronger statement, the law, to be true, then it will follow from the evidence that the conclusion ‘humans causes global warming’ according to empirical data (observations) is in fact correct. However the OP never shows this but stop at the weaker statement. Why the OP has decided to exclude the stronger statement from the article remains a mystery to me. But just because the OP has decided to exclude it, the OP is guilty of having jumped to the conclusion that human causes global warming
  49. What does past climate change tell us?
    "we have to work pretty hard to send 29 gigatonnes of CO2 into the atmosphere every year." Only by breathing humans releases approximately 2 gigatonnes of CO2 every year into the atmosphere. (The calculation is based on that one(1) human release about 1 kg of CO2 per day)
  50. What does past climate change tell us?
    Response: The point is to address the argument that it's increasing population that is causing increasing CO2 emissions. On the contrary, the cause is over-consumption more than over-population. If we're going to hit CO2 emissions, best to be pointing in the right direction. You didn't answer the point I made you you hold up the Sub-saharan life as the way forward for humanity. Along with empty bellies, disease, illiteracy and wasted potential they also have a small carbon footprints. Well done the sub-saharan africans. Humanity isn't just about a head count its about a quality of life which requires consumption. Briefly forget about emission and think about the life of the people you are talking about.

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