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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 111551 to 111600:

  1. Arctic sea ice... take 2
    CBW, I think that NSIDC and other scientists prefer to use ice extent because the errors in measuring it are lower. The sensors have difficulty telling apart melt ponds on top of ice and open ocean so that adds to the error of area measurements. They prefer to use extent data dealing with the public because they are more sure of those numbers. see this link: http://nsidc.org/arcticseaicenews/faq.html#area_extent In any case, all of the measures of ice are going down. It is just a question of how fast they are going down. Once the new ice volume satellite comes on line that data will be much more useful. That should be sometime this fall.
  2. Arctic sea ice... take 2
    I realize that this is a basic post, but it makes no mention of ice area. Ice extent is a fundamentally flawed measure of ice because loose ice is subject to being moved around by wind and currents, and shows suppressed variability because thicker ice spreads out as the ice that restrains it disappears. The only reason it is used is because it has value for navigation, and hence a longer historical record. Ice area, on the other hand, tells you how much of the ocean surface is actually covered with ice, and so is a much better measure of the albedo and the potential feedback effects it implies. Extent tells you where there are chunks of ice floating around. Volume and area tell you how much ice there is and how much of the planet's surface it covers.
  3. Can humans affect global climate?
    Arkadiusz Semczyszak, both E.G. Beck and Jaworowski are very poor sources. Citing them tends to weaken rather than strengthen your case.
  4. Comparing volcanic CO2 to human CO2
    Berényi Péter writes: At the same time there is about 40,000 Gt carbon dissolved in the oceans in the form of various carbon compounds. That's equivalent to 145,000 Gt of CO2. We also have several tens of million Gt carbon buried in carbonate rocks. Yes ... so? What's the point, BP? CO2 has been remarkably stable over the past 800,000 years, ranging from ~180 ppmv at glacial maxima to ~280 ppmv during interglacials. But since 1850 we have raised the atmospheric CO2 concentration by 112 ppmv, roughly equivalent to the maximum fluctuation in the entire ice-core record ... but starting at what was already a high point. Over the course of this century we will almost certainly be adding another 150 to 300 ppmv on top of today's level. Nothing like this has happened any time in the past 800,000 years. Figure 1: CO2 concentration over the past 800,000 years from ice cores at Dome C, Vostok, Taylor Dome, and Law Dome.
  5. Comparing volcanic CO2 to human CO2
    Speaking of C12/C13 ratio. This is an analysis of Spencer that clearly shows its imcompetency. http://wattsupwiththat.com/2008/01/28/spencer-pt2-more-co2-peculiarities-the-c13c12-isotope-ratio/ Check the comments, there are as coherent ;)
  6. Hansen etal hit a Climate Home Run -- in 1981
    Shouldn't Hansen's prediction be compared to some naive/null prediction?
  7. Arkadiusz Semczyszak at 00:53 AM on 28 August 2010
    Can humans affect global climate?
    CO2 and oceans. Natural forcing of climate during the last millennium: fingerprint of solar variability, Swingedouw et al., 2010: “We argue that this lag is due, in the model, to a northward shift of the tropical atmospheric convection in the Pacific Ocean, which is maximum more than four decades after the solar forcing increase. This shift then forces a positive NAO through an atmospheric wave connection related to the jet-stream wave guide. The shift of the tropical convection is due to the persistence of anomalous warm SST forcing the anomalous precipitation, associated with the advection of warm SST by the North Pacific subtropical gyre in a few decades. Finally, we analyse the response of the Atlantic meridional overturning circulation to solar forcing and find that the former [AMOC] is WEAKENED when the latter increases. Changes in wind stress, notably due to the NAO, modify the barotropic streamfunction in the Atlantic 50 years after solar variations. This implies a wind-driven modification of the oceanic circulation in the Atlantic sector in response to changes in solar forcing, in addition to the variations of the thermohaline circulation.” Dr Fraser (Southern ocean carbon sink weakened, 2007) says: “The increase in wind strength is due to a combination of higher levels of greenhouse gases in the atmosphere and long-term ozone depletion in the stratosphere, which previous CSIRO research has shown intensifies storms over the Southern Ocean.” „The increased winds influence the processes of mixing and upwelling in the ocean, which in turn cause an increased release of carbon dioxide into the atmosphere, reducing the net absorption of carbon dioxide into the ocean.” “A new hydrographic section across 25° N was taken in 2004, and comparison with measurements from 1957, 1981, 1992 and 1998 reveals a slowing [AMOC] of almost a third between 1957 and 2004.” (Atlantic Ocean trends, Nature Journal, 2005.) ... Solar activity increased, AMOC weaken - CO 2 increased - it’s "pure" The Nature ... Extreme deepening of the Atlantic overturning circulation during deglaciation, Barker et al., 2010.: “We conclude that the rise in atmospheric CO 2 concentrations and resultant warming associated with an especially weak overturning circulation are sufficient to trigger a switch to a vigorous circulation, but a full transition to interglacial conditions requires additional forcing at an orbital scale.” “... i.e., the AMOC is stronger when the north is cooler ...” (Toggweiler, 2010) D’Orgeville & Peltier (2009), CCSM3 T31x3 pre-industrial control, 60 yr: Similar in-phase T and S contributions to density, less role for NAO, but suggest gyre – bathymetry interaction. Results: min. AMOC - reduced sea ice, increased upwelling ...
  8. Arkadiusz Semczyszak at 00:44 AM on 28 August 2010
    Can humans affect global climate?
    “a significant decrease in water vapour in the atmosphere” I recall, the reasons may be different. “We have measurements, that in 1970-90s water vapour was on the rise in the stratosphere. As soon as SOLAR ACTIVITY STARTED TO DROP in 1990s, WATER VAPOUR ALSO STARTED TO DROP. In 2000-2009 water vapour content in the troposphere dropped by 10%. [...]” (Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming,Solomon,2010.). With this, beautifully, correlates decline of NPP: Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009 – Zhao & Running (2010): “The past decade (2000 to 2009) has been the warmest since instrumental measurements began, which could imply continued increases in NPP; however, our estimates suggest a reduction in the global NPP of 0.55 petagrams of carbon. Large-scale droughts have reduced regional NPP ...” “A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production.” "This is a pretty serious warning that warmer temperatures are not going to endlessly improve plant growth, [...???]" Running said. “... that the additional CO2 can only be the result of human activity.” “Burning fossil fuels produces carbon dioxide enriched with carbon isotope C12 and reduced C13 and essentially no C14, and it decreases atmospheric oxygen, exactly as observed.” First, for the record once again remind you: of course CO2 from respiration is the same as the ratio of ratio13C/12C from fossil fuels. And 14C? If we base on it (tree ring, np. Eddy, 1976), then we would have to conclude that, for example in the MWP - it was similar or even more CO2 in the air than now ... 14C ... ... formed in the upper atmosphere of Earth as a result of the impact of cosmic rays with nitrogen (14N). Particle flux of radiation is greatest during periods of minimum solar activity - the weakening of its magnetic field, which shields the Earth and is a barrier to cosmic radiation. Arises more isotope 14C, which, diffuses into the lower areas of the atmosphere, among other things aside in annual increments of trees. So the greater the activity of the Sun, the less 14C falls on Earth ... “Nonetheless, it is confirmed with the new palaeomagnetic series that the Sun spends only 2–3% [!] of the time in a state of high activity, similar to the modern episode. This strengthens the conclusion that the modern high activity level is very unusual during the last 7000 years [...].” (Usoskin, IG , SK Solanki, and M. Korte (Geophys. Res. Lett., 2006 ), Solar activity reconstructed over the last 7000 years: The influence of geomagnetic field changes.) Now, in recent decades have seen increased by 15% increase in soil respiration (especially the Arctic) than predicted were the best models, also decreased to CO2 absorption by the oceans ..., ... and as we add to this the current decline in NPP ... Jaworowski Z. (2007) Carbon Cycle. Working materials for Seminar of Nongovernmental International Panel on Climate Change, Vienna 14 April, 2007. NIPCC Seminar, p. 1-21. annual fluxes of CO2 into the atmosphere: all natural ~ 170 Gt C Human total 7.97 Gt C = 4.7% of the natural stream, 0.16% of "greenhouse effect" I also recommend the latest work Beck for discussion; and the web article and his best criticism.
  9. Berényi Péter at 00:23 AM on 28 August 2010
    Can humans affect global climate?
    #18 Dappledwater at 22:16 PM on 27 August, 2010 what's the 30 year trend at Armagh? For the last 30 years it's +0.21°C/decade. However, for the last 20 years it is only 0.06°C/decade and for the last 80 it's 0.046. Should measurements be finished at the end of 2002, facts would not get in the way and the accelerating trend stands out clear. 20 years: 0.48°C/decade 30 years: 0.35°C/decade 80 years: 0.06°C/decade
  10. Humans are too insignificant to affect global climate
    You're welcome. :) Of course there's never much 13C to begin with (only 1.1% of Earth's carbon is 13C), but the preference plants have for 12C makes their 13C/12C ratio about 2% lower, causing (by burning fuel) the atmospheric 13C/12C ratio to drop 0.15% since 1850. Now this may not look like much, until you realize this 0.15% drop comes from just a 2% lower ratio of just a 1.1% isotope, and then it's suddenly quite a lot. Still, I think it's quite amazing someone actually thought of it. :D
  11. Comparing volcanic CO2 to human CO2
    BP writes: No. 337 Gt carbon is equivalent to 1236 Gt of CO2. You are of course right -- I reversed the conversion. Sorry about that. However, it doesn't affect the rest of the calculations in my comment. 337 GT carbon is approximately equivalent to 158 ppmv in the atmosphere. Comparing this to the observed 112 ppmv increase in the atmosphere shows that, in answer to RSVP's question, there's nothing really large that needs to be explained -- most of the CO2 increase from fossil fuels is still in the atmosphere, but a fraction of it has gone into the oceans. Anyway, thanks for the correction, Berényi Péter. It's been a long week.
  12. Humans are too insignificant to affect global climate
    So, by burning fuel/plants, we add more 12C to the atmosphere. Aha! Thank you!
  13. Can humans affect global climate?
    Speaking of C12/C13 ratio. This is an analysis of Spencer that clearly shows its imcompetency. http://wattsupwiththat.com/2008/01/28/spencer-pt2-more-co2-peculiarities-the-c13c12-isotope-ratio/ Check the comments, there are as coherent ;)
  14. Berényi Péter at 22:33 PM on 27 August 2010
    Comparing volcanic CO2 to human CO2
    #5 Ned at 21:23 PM on 27 August, 2010 Total emissions since 1750 from fossil fuels and cement production are 337 GT carbon (from ORNL-DAAC). Note that this is equivalent to 92 GT of CO2. No. 337 Gt carbon is equivalent to 1236 Gt of CO2. Currently we have about 3000 Gt of the stuff in the atmosphere. That's equivalent to 823 Gt carbon. At the same time there is about 40,000 Gt carbon dissolved in the oceans in the form of various carbon compounds. That's equivalent to 145,000 Gt of CO2. We also have several tens of million Gt carbon buried in carbonate rocks.
  15. Can humans affect global climate?
    HR @ 12 - wouldn't we really need to plot temperature data prior to the Industrial Revolution, to really understand "natural" natural variability?. Once humans start to pump larges amounts of greenhouse gases into the atmosphere, how natural is that?.
  16. Arctic sea ice... take 2
    HR, ummm... yes, and I quoted the part of that 'scientists in planes' paper where they said the volume of older ice may have decreased. You're trying to use a small area study to advance a conclusion that the study itself contradicts based on insufficient data.
  17. Climate Models: Learning From History Rather Than Repeating It
    9.Dappledwater There is a new paper in JGL-Oceans (presently it's flagged as the most popular download) which uses a new method for calculating 20th SLR. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 115, C08013, 15 PP., 2010 doi:10.1029/2009JC005630 Reconstruction of regional mean sea level anomalies from tide gauges using neural networks Manfred Wenzel and Jens Schröter While they find similar 20th C SLR to other papers, such as Church & White 2006 they do not see any late 20th C acceleration. They explain this as follows "This is obviously due to the missing depression in sea level prior to 1950 that is the main difference of our result to CW06" I can't comment on the neural network method used in their calculations but it does suggest there is still more to learn about this particular metric.
  18. Can humans affect global climate?
    BP, what's the 30 year trend at Armagh?.
  19. Arctic sea ice... take 2
    HR @18 - that's not what those passages suggest, however who knows?, it's not discussed in the paper. Pete Hogarth - the multi year ice ain't what it's cracked up to be either
  20. Comparing volcanic CO2 to human CO2
    RSVP, also 250 ppm was indeed the 'pre-Industrial Revolution' CO2 level... if you are talking about ~13,000 years before the Industrial Revolution. Immediately before industrialization began it was around 280 ppm.
  21. Climate Models: Learning From History Rather Than Repeating It
    johnd #26: Yes, I mentioned that I was skipping over the details of feedback effects entirely since 'at' was asking about the '3 C per doubling of CO2' estimate specifically. However, the broad strokes of the hydrological cycle aren't really as much of a mystery as you seem to suggest. Where and when a particular precipitation incident will occur, aka 'weather', is much more difficult to predict than average precipitation, aka 'climate'. The increased water vapor content of the atmosphere is the single largest positive feedback included in that '3 C per doubling' estimate. Rain, snow, clouds, and other incidental effects of that increased atmospheric water vapor have been studied and found to have fairly negligible effects... to the point where it isn't clear whether they are a net positive or negative feedback, but IS clear that they are a tiny fraction of the positive feedback effect of the water vapor itself.
  22. Berényi Péter at 21:44 PM on 27 August 2010
    Can humans affect global climate?
    #14 John Chapman at 15:03 PM on 27 August, 2010 Why doesn't the Armagh Observatory have records since 2002?? They have them, it's just data beyond 2002 are not processed like this. In fact daily data in the archive are in a reasonable format only since July 2000, prior to that date they only have the scanned images of handwritten forms. Anyway, it is imperative not to go beyond 2002, because monthly temperature anomalies (relative to 1930-1989 means) recovered from the archive look like this between July 2000 and 2010: As you can see, after 2002 Armagh Observatory is cooling at an alarming rate of 13.2°C/century.
  23. Arctic sea ice... take 2
    HumanityRules at 09:43 AM on 27 August, 2010 There is also an update (to April 2010) of the Maslanik and Fowler 2007 "age of ice" animation which these guys kindly did for me in the second article on Arctic sea ice. As older ice is generally thicker, this is pertinent.
  24. Comparing volcanic CO2 to human CO2
    RSVP: Total emissions since 1750 from fossil fuels and cement production are 337 GT carbon (from ORNL-DAAC). Note that this is equivalent to 92 GT of CO2. If all of this accumulated in the atmosphere, it would represent an increase of 158 ppmv CO2 (2.13 GT carbon per 1 ppmv CO2). However, quite a bit goes into the ocean, so the actual rise has only been about 112 ppmv so far. It's still quite an increase over the pre-industrial conditions: Figure 1: CO2 levels (parts per million) over the past 10,000 years. Blue line from Taylor Dome ice cores (NOAA). Green line from Law Dome ice core (CDIAC). Red line from direct measurements at Mauna Loa, Hawaii (NOAA).
  25. Arctic sea ice... take 2
    HumanityRules at 09:43 AM on 27 August, 2010 There are some more post 2007 articles in Arctic ice, a reality check. I have a small amount of even more recent information, but will try to collate this. There are however multiple smaller scale studies for ice thickness, using all sorts of methods, but difficult to draw arctic wide conclusions as thickness and melt rate are not uniform over the sea ice area.
  26. Comparing volcanic CO2 to human CO2
    The presentation is straighforward and informative, yet something seems to be missing.. (i.e., another cloud graphic that represents some other major, yet natural source(s) of CO2). Supposedly, pre-Industrial Revolution CO2 levels were around 250 ppm, whereas now they are around 380 ppm, an increment ratio of 1.5:1. On the otherhand, according to the above, man-made fossil fuel emission is around 100 times that of volcanos. If one assumes nature is only equipped to absorb the CO2 emitted by volcanos, one would expect current CO2 ppm to be much higher. What exactly is not being explained here?
  27. Increasing CO2 has little to no effect
    Stylo, "more longwave radiation returning back to Earth" means "more than previously." The atmosphere still radiates in all directions, and John actually is referring to absorption/emission rather than reflection. Imagine an Earth with no greenhouse gases in its atmosphere. 100% of the thermal radiation leaving the surface and passing through the atmosphere goes upward and out into space. Now add a small concentration of greenhouse gases. A small part of that longwave radiation will be absorbed by GHG molecules, which will then emit energy in all directions, including downward. So now somewhat less than 100% of the thermal radiation within the atmosphere is moving in an upwards direction. And as you increase the concentration of GHGs, the downward component becomes correspondingly larger. The downward thermal IR flux is indeed caused by emittance, not reflectance.
  28. Greenhouse effect has been falsified
    Will writes: The problem lies in the lack of understand of the fact that the atmosphere both radiates and insulates at the same time. Insulates what? From what? The only way that the Earth loses heat is by radiating to space. The only way that I can see the word "insulation" being relevant in this process is ... the effect of greenhouse gases repeatedly absorbing and re-radiating energy from the surface, slowing its outward flux and raising the temperature of the Earth system. But that's exactly the process you claim doesn't occur, so you presumably mean something else, right? In addition, I'm still curious about this remark from an earlier comment of yours: Thermal radiation is heat. Vibrating matter. Gas molecules are vibrating matter. [...] In the vacuum of space full spectrum EMR produces no thermal radiation, heat. Thermal infrared radiation is just another part of the electromagnetic spectrum; it's called "thermal" because it's the range at which normal Earth-surface objects radiate. It obviously does propagate through space (we use thermal sensors operating in the 8-14 micrometer window to measure this from satellites). Oh, and not to overload you with questions, but it would be nice if you could answer the questions from this comment. At what wavelength ranges does nitrogen in the Earth's atmosphere absorb and emit radiation? Thanks. muoncounter writes: Note: Any rumors that I have started a 'Ned Fan Club' are categorically false. Hey, I like that idea.
  29. Climate Models: Learning From History Rather Than Repeating It
    Thanks, Dappledwater, CBDunkerson, Ned, CBW, nigelj, for your responses to my questions about sea level and CO2! Sea level was an example of what models try to predict. Now back to the posted text about models in general. The following is stated: "The models used to predict future global warming can accurately map past climate changes." This measure of accuracy is, of course, important. The next sentence reads: "If they get the past right, there is no reason to think their predictions would be wrong." No reason? That sounds, to me, a bit too optimistic. What if the model is wrong on some points, but repairs these errors by being wrong on other points as well? Then, even if the model fits known historical data, it will not necessarily fit future data. Recently some preliminary results of a study of the atmosphere, undertaken this year, were presented. It seems that some assumptions about both greenhouse gasses and black carbon may have to be modified. See article here! Two quotes: Among the surprises to come out of HIPPO data are nitrous oxide concentrations that consistently seem to increase with altitude. "Yet the models all show concentrations decreasing with altitude," says Wofsy. The implication, he adds, is that models are either not properly accounting for the transport of nitrous oxide or they are missing a source of the greenhouse gas.Wofsy and his colleagues report that the first HIPPO flight in January 2009 found levels of black carbon that average about five times lower than predicted by an ensemble of 14 global aerosol models […] The models underestimated how much black carbon is being scrubbed out of the air by precipitation, says lead author Joshua Schwarz, […].
  30. Increasing CO2 has little to no effect
    Poor Roy Spencer doesn't understand that what he is measuring is the temperature of the night air not the absorption of IR from the ground. He (perhaps subconsciously) confuses the phenomenon of emission with reflection. The IR emission of CO2 downwards depends only on the temperature of the air not on how that temperature was achieved; whether though IR absorption, convection, water condensation or sunlight. In this above article it says:
    "... Satellite measurements confirm less longwave radiation is escaping to space...Surface measurements find more longwave radiation returning back to Earth at these same wavelengths."
    If the atmosphere is warmer, then it should emit more IR in both the down and up directions. If it's in fact radiating more IR downward but less upward, then this phenomena is reflection not absorption and emission.
  31. Comparing volcanic CO2 to human CO2
    Great article. Maybe now the disinformation Rush Limbaugh inflicted on the public will finally die the slow, agonizing death it deserves.
  32. Climate Models: Learning From History Rather Than Repeating It
    CBDunkerson at 05:02 AM, calculating CO2 levels is only a small part of the complete picture. That complete picture has to include water vapour. Each degC rise equates to a 6-7.5% increase in water vapour, or about 20% for each doubling of CO2. If those relationships are linear, then during the ice age water vapour would have been about 15,000ppm, currently about 20,000ppm and with a doubling of CO2 about 24,000ppm. How all that extra water vapour transforms back to a liquid or a solid, and what it means in terms of cloud cover is I think the most interesting, and perhaps the most important process that needs to be understood..
  33. Comparing volcanic CO2 to human CO2
    This is nice, especially the graphic. The obvious reply to the Plimer madness is to observe how remarkable it is that the postulated increase in invisible volcanic activity, gradually, decade by decade over the last 40 years, should so precisely match the known increase in CO2 from industrial activity.
  34. Polar bear numbers are increasing
    I would add this item about the bears. We stopped shooting the crap out of them in 1973 due to a treaty.
  35. Comparing volcanic CO2 to human CO2
    A nice and simple explanation, but might the impact of the Terry Gerlach article in Earth Magazine be somewhat diluted by its footnote?
    Gerlach is an emeritus geologist at the U.S. Geological Survey, Cascades Volcano Observatory, in Vancouver, Wash. E-mail: tgerlach@usgs.gov. The views expressed are his own.
    Of course, any that proceed to read the USGS reference will see that essentially the exact same observations are made, but with more references to the science. I'm ambivalent concerning the best approach, because I liked the Gerlach article and it's vitally important to hammer-home that Plimer's factually challenged book is useless as a guide to the science. But I'm glad that you provided the USGS as confirmation. Might a one sentence Gerlach biography might be useful?
  36. actually thoughtful at 15:40 PM on 27 August 2010
    Climate Models: Learning From History Rather Than Repeating It
    Wow - I feel like a butterfly flapping it's wings along a fractal coastline (said butterfly being blissfully unaware of the complexity it's simple actions represent) - I had no idea how much complexity lived behind "3C/doubling of CO2" - thanks CBDunkerson, KR and Riccardo for the insights. If anyone wanted to try a post fully explaining this bit in layman's term (hint: Guassian and Lorentzian don't qualify ;-)) - I at least would be grateful. I have enough to be happy with "3C/doubling" - but I could not defend an attack on that (although I have never seen an attack that realized how complicated the concept of climate sensitivity was (other than to say "no support for anything more than .75C/doubling - ie no positive feedbacks)). Back to muttering and puttering - perhaps I will awaken tomorrow and suddenly understand that which eludes me today (and too, perhaps all deniers will succumb to logic and facts - both outcomes are highly doubtful).
  37. Can humans affect global climate?
    In answer to #13, the words of David Karoly ... Burning fossil fuels produces carbon dioxide enriched with carbon isotope C12 and reduced C13 and essentially no C14, and it decreases atmospheric oxygen, exactly as observed.
  38. Can humans affect global climate?
    nerndt - To put 2ppm/year into the atmosphere would require an additional years growth of the Amazon burning every year. That's every year for the last 100 or so. It would closely match the observed isotope ratios, but... At that rate we would have lost ~10 Amazons (assuming plant ages ~10yrs on average) in the last century. That simply hasn't happened. And as to natural variation, take a look at the last 425Kyr, from the Vostok ice core data: The current 390ppm of CO2 simply isn't in the range of natural variations for the last half million years. On the other hand, we know we're currently adding 29Gtn of CO2 to the air every year (enough for 4ppm increase), of which half seems to be sticking around in the air (2ppm yearly increase), the rest going into sinks like the ocean. So we would have to disregard our CO2 output and believe that a few Amazons we haven't been tracking have burned/decayed? Or perhaps we can conclude that it's our CO2 output?
  39. Can humans affect global climate?
    Why doesn't the Armagh Observatory have records since 2002??
  40. Can humans affect global climate?
    Can someone truly explain how you can determine when CO2 is produced by humans burning fossil fuels versus natural decomposition of vegetation that would occur naturally as the temperature increases? The signature for all decomposing vegetation is the same (where atmospheric gases are slightly different because of the concentration of the Carbon isotope (C14 vs C15). I can not tell how you could separate the CO2 emitted by just more decomposition of plants when the planet warms up during natural oscillations.
  41. Can humans affect global climate?
    Isn't H2O the most common GHG? (This is maybe unrelated but I like it so I'll try a tenuous justification) I don't disagree that we can affect many aspects of our planet, your example of atmospheric CO2 is a strong candidate for that argument. But I wonder if in considering that we aren't blinding ourselves to natural variability. Here's the official data from a long temperature record at Armagh Observatory stretching back to 1800. This will take you 5-10 minutes but grab the annual data and graph it. Smooth it with 25 year running mean. What you get is a warming trend stretching back to the start of the record with low frequency oscillations. The most recent 'extreme' warming doesn't even show up as anything out of the ordinary. Tell me how humans have caused this and it is not natural variability? Humans can change our planet doesn't mean they have changed it in all the ways we think.
  42. How we know global warming is still happening
    All these short term charts don't mean squat. go back a few thousand years at least. We have been in a warm period for about the last 10K. Look at all of them rather than just the last 100 or so. How in the world can you call CO2 the dominant forcing when you know that if Water vapor was cut by 10% we would probably go into and ice age.
    Moderator Response: In the Search field at the top left of this page, type "Climate's Changed Before." Also "Water Vapor is the Most Powerful Greenhouse Gas."
  43. NASA-GISS: July 2010-- What global warming looks like
    And why would you expect a one to one ratio? Nature seldom does that over thew short haul. Besides that, these records are for the last 100 years. Of course if you come up with couple warm decades you'll see high records fall. These records in a short time set, climatologically speaking. The longer you keep records the more likely you are to see it even out and records decrease in number.
  44. Can humans affect global climate?
    muoncounter at 11:45 AM, the chart below shows that the 440 + 260 +70, total 770 Gigatonnes released by natural means is roughly 30 times the 26 Gtonnes indicated as being released primariliy by fossil fuels.
  45. Medieval Warm Period: rhetoric vs science
    I disagree with steve's take on Moberg versus loehle. Loehle was clearly flawed whereas Moberg brought something new to the field with his novel wavelet technique. I think anyone who would give loehle's analysis the same credibility as Moberg's clearly has an agenda as methodologically the difference is clear.
  46. Can humans affect global climate?
    //"Of course we can’t influence a single weather event, but we can and do have a long term influence on the climate that causes it."// Lorenz would be rolling in his grave...
  47. Climate Models: Learning From History Rather Than Repeating It
    actually thoughtfull - The CO2 absorption band shape is between a Gaussian and a Lorentzian in shape (Riccardo posted about this here). The peak is saturated, but with every doubling the band blocked broadens enough to add an additional 3C. Not intuitive, perhaps, but if you think of it as scaling a clipped Gaussian it kind of makes sense.
  48. Can humans affect global climate?
    #8: "But natural sources far exceed human emissions by a factor of about 30. " Please substantiate that claim. Fossil fuel sources produced 30 Gtons (that's metric tons) CO2 in 2008. Perhaps you found it here?
  49. actually thoughtful at 11:41 AM on 27 August 2010
    Climate Models: Learning From History Rather Than Repeating It
    Thank you CBDunkerson - I see that it is still 3C per doubling, and I can accept that I don't completely understand why it isn't 3C/280ppm (I kind of do - once you double the CO2 the marginal harm of an additional ppm is lower, but the relationship of 3C/doubling still holds). I am thinking you need a given BTU to bump into twice as many CO2 molecules as the baseline to yield the 3C increase. I think I am proving my (lack of) mental powers here. Thanks again for clarifying the log bit.
  50. Climate Models: Learning From History Rather Than Repeating It
    Argus I think its good that as a sceptic you look at long term trends presented as a straight line rather than short term noise. I note the long term temperature trend since around 1880 to 20009 is a straight line pointing up.

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