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Comments 127201 to 127250:

  1. 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.
  2. 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.
  3. 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?
  4. 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).
  5. 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?
  6. 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?
  7. 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.
  8. 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.
  9. 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.
  10. 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/
  11. 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
  12. 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.....
  13. 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.
  14. 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 ;)
  15. 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.....
  16. 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.
  17. 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.
  18. 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.
  19. 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.
  20. 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.
  21. 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.
  22. 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??
  23. 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.
  24. 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
  25. 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.
  26. 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.
  27. What does past climate change tell us?
    Thanks Philippe, So we're now moving into the cooling phase of the Milankovitch cycle correct?
  28. 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.
  29. 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.
  30. What does past climate change tell us?
    batsvensson, luckly the CO2 we release with respiration does not come from fossile carbon ;)
  31. 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.
  32. 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!
  33. Empirical evidence that humans are causing global warming
    Correction to above "The clearest fig to my mind is Figure 3 from chen 2007"
  34. 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?
  35. 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.
  36. 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.
  37. 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
  38. 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?
  39. 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
  40. 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)
  41. 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.
  42. Comparing CO2 emissions to CO2 levels
    You DO need to include deforestation and other "land use" emissions, which are clearly not present in your dataset. Note that your curve shows some rise of atmospheric CO2 in the 18th-19th century before industrial emissions became strong. This is due to the deforestation of North America and other regions. All this is well covered by the work of William Ruddiman (for references, look him up in Wikipedia). By the way, Ruddiman's work is even more important for cumulative methane emissions.
  43. How do we know CO2 is causing warming?
    @Henry Pool I'm a little bit confused by what you call the cooling effect of CO2. Do you refer to the part of the radiation that is re-emitted toward space after absorption? If this is what you mean, the point is that the process of absorption and re-emission happens through the whole atmosphere, true, but at very different temperatures and pressures going from the surface up. At some point (altitude), the radiation will escape to space and it's the temperature and pressure at this point that matters for the energy balance.
  44. What does past climate change tell us?
    @RSVP "What I dont understand is how the "non-skeptics" somehow think it is possible to lower CO2 contamination without addressing population growth and the other sources of global warming?" If i get your thoght right, i think you should focus a little bit more. Given that poor people emit enormously less CO2 than rich, the question should be how can they improve their condition without a catastrophic increase of GHGs? This point is made clear and addressed in the UNDP Human Development Report 2008. This little step will change the view that the problem is population by itself, the raw number. And also again underline that the problem is global as global has to be the solution.
  45. What does past climate change tell us?
    Reply to HumanityRules I am in agreement with you, which I will explain, however, you have confused my point with content added by "Response". In fact it was "cbrock" who originally cites Monbiot. I agree with you in that I do not see Monbiot as being correct in, as you imply, holding up some of the worst living conditions as the way forward. On the contrary, my assessment is that the only viable solution is to work on curbing population. What I dont understand is how the "non-skeptics" somehow think it is possible to lower CO2 contamination without addressing population growth and the other sources of global warming?? What do they think got the CO2 contamination to these levels in the first place? And to be quibbling about who exactly is responsible is hypocritical when you consider the extended influence of the globalized economy. Aside from CO2, isnt it clear that there is no energy delivery system that does not pollute heat directly in some form or another, starting with nuclear energy??? Example http://en.wikipedia.org/wiki/Heat_engine And getting real... behind every solar cell, there is a automobile in a chip plant parking lot used everyday for a 25 mile commute. Behind every wind farm, there are trucks (as you read this) used in transport and maintenance burning diesel. ETC. Getting back to my original point. I wasnt addressing man-made global warming. I was referring to the historical data that indicates potential for global warming or cooling whether man-made or not. And the fact that so many people live on the fringes of habitable terrain. ------------------------ By the way, in the news yesterday, an AP article terms greenhouse gasses as "global-warming gases"... fait accompli. http://www.google.com/hostednews/ap/article/ALeqM5jZFyOvC-Hn8ZRKlbw2eJKukIRmHAD9BFKLT00
  46. What does past climate change tell us?
    @ RSVP You include this "Monbiot: "A paper published yesterday in the journal Environment and Urbanization shows that the places where population has been growing fastest are those in which carbon dioxide has been growing most slowly, and vice versa. Between 1980 and 2005, for example, Sub-Saharan Africa produced 18.5% of the world’s population growth and just 2.4% of the growth in CO2. North America turned out 4% of the extra people, but 14% of the extra emissions." I'm not sure what point you are trying to make. That population can expand ith limited impact on CO2 levels? Sub-Saharan Africa has just about the worst living condition for human being than any place on earth. Life expectancy, child mortality, education, infrastructure I could go on and on and on. It seems you (or more accurately Monbiot) are holding these people up as examples to us all. You want all of us to have quality of life similar to sub-saharan africans? I'd prefer to fight for an improvement in their quality of life and the inevitable increase in their carbon footprint than champion extreme poverty as some way forward. Unpleasant decadence from privileged western liberals
    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.
  47. What does past climate change tell us?
    There seems to be a leap in this article that is unexplained and leaving me confused. Many things can absorb the suns energy and many things can reflect the suns energy and maybe the amount of energy from the sun can vary. And maybe the way processes (currents, continents, winds) move that energy around the global alters things. You show an equation, very sciencey. Then make the comment "The most common way of describing climate sensitivity is how much global temperature would change if CO2 is doubled." and from then on it seems everything is explainable by CO2 levels. I don't get that last jump. Just because some people simplify the process down to CO2 levels doesn't mean that CO2 is the main cause. Or have other factors been corrected for? How would you know albedo, volcanic activity, cloud cover, ocean currents etc for this whole period? Few other things. 1) So there was a Medieval Warm Period? Because I thought this was expunged from history by Mann as an inconvinient truth. 2) "Hegerl 2006 looks at global temperatures spanning both periods, using 4 different temperature reconstructions." Isn't it northern semishpere temperature not global temperature in that publication?
    Response: In its most fundamental terms, climate sensitivity means "if climate experienced a radiative forcing of 3.7 Wm-2, global temperatures would rise 3°C". This is the case whether the radiative forcing came from CO2, methane, solar variations, changes in albedo, etc. Or more accurately, all those factors added together.

    CO2 is not the only driver of climate. When you add them all together, then you have the net radiative forcing that is driving climate. I've gone back and tweaked the wording of that paragraph, hopefully clarifying the language somewhat. In fact, I'm currently working on a post coincidentally titled "CO2 is not the only driver of climate" :-)

    The main controversy with the Medieval Warming Period is whether it was global or a regional phenomenon. However, bickering over how widespread the MWP was underlies the irony of arguing about past climate change. If, as skeptics say, the MWP was a global phenomenon and temperature change was greater than currently thought, that would mean climate is more sensitive than previously thought. Hence the climate reaction to current CO2 radiative forcing would be even larger.

    Re Hergerl 2006, you're right, it did use NH reconstructions, not global. Thanks for spotting that, I've updated the post.
  48. Alberta Clipper at 15:22 PM on 22 October 2009
    How do we know CO2 is causing warming?
    Co2 is not CO2. Co2 is molecular cobalt (Co). Why didn't the moderator pick up on that?
  49. How do we know CO2 is causing warming?
    It appears no one ever seemed to have come up with the thought that carbon dioxide also causes cooling. I did not receive an answer to my question at post 67.perhaps I still get an answer. But I doubt it. It seems everyone forgot to look at the cooling aspect. In my view, especially with CO2, the way for radiation from the top to the bottom is the same as for the bottom to the top because the CO2 is almost 100%diffused into the air, so this question is and must be relevant. Why did no one ask it before? The cooling does not happen just in the upper air, it happens anywhere. I am busy carefully analyzing the graphs that I posted at 67, and all in all, it looks to me pretty much evens up, In other words: the cooling effect might in fact be just as much as the warming effect. If you enlarge it big enough you will notice that there are a few small gaps caused in the sun’s radiation which is due in part to the two absorptions of carbon dioxide between 2 and 3 um. It seems to me that the spectral intensity at the 4-5 um absorption is pretty much the same for both the sun and earth, although it is probably not on the same scale. But let us say this cancels each other out, more or less. It seems there is a small corner of radiation not being emitted by earth due to the CO2 absorption, at 14 um. (note that water is also absorbing here). This is the warming effect. Without someone doing some experimental testing, I think it will be difficult to quantify which is the biggest: the cooling or the warming. But if you ask me, it looks to me that the nett effect is or will be close to zero
  50. Philippe Chantreau at 11:04 AM on 22 October 2009
    How do we know CO2 is causing warming?
    TS, all the science used by the IPCC is done "outside" of the organization. You say you like the science papers presented in this site. Did it occur to you that most of them are part of the body of science used by the IPCC in its work?

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