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Chris Colose at 07:27 AM on 16 September 2010Why positive feedback doesn't necessarily lead to runaway warming
The scale height for water vapor is quite small, about 2 km so abundance-wise you are correct. This is one reason why water vapor doesn't overwhelm the CO2 greenhouse effect, as water vapor is relatively leaky high up. CO2 has a very little effect in an atmosphere that is really wet up into the stratosphere, as you might get prior to a runaway scenario, but Earth is quite far from this regime. CO2 is pretty well-mixed until the stratosphere or so; I'm not sure how the CO2 mixing ratio changes once you get above the stratosphere (clearly water vapor is not really existent here) but for radiative transfer purposes there isn't really much greenhouse influence this high anyway because the air is so thin. One you get above the so-called "photosphere" at a given wavelength you become pretty optically thin, and below it pretty absorbing. If you use David Archer's model (which I plotted a few example diagrams in my link in the last comment) you can convince yourself that right at 15 microns the CO2 emission comes from the stratosphere (and in the wings, closer to the surface), since there appears to be an upwards blip inside the ditch in the spectrum itself (this becomes really obvious if you put like 100,000 ppm of CO2 into the model). The reason for this is that the temperature of the stratopsphere becomes isothermal or increases with height. Numbers of a spectrally averaged "photosphere" is about 5 km, since 288 ~ 255 K +(5 km)(6.5 K/km) Hope that helps -
Skepticalenergyguy at 07:20 AM on 16 September 2010Human CO2 is a tiny % of CO2 emissions
muoncounter, with H2S being around .0000002% of our atmosphere, I'm not too worried about your 380ppm. The real question is, Is CO2 really causing global warming? Or is it the scapegoat for earth's natural cycle of weather change? -
johnd at 07:02 AM on 16 September 2010Climate change: Water vapor makes for a wet argument
michael sweet at 07:18 AM, I'm not sure whether you were claiming expertise as a psychic or as a comedian, but your claim regarding the Spencer's articles left me ROTFLMAO. On the contrary I have read about Spencer's experiment and it should have been obvious that this discussion was leading towards it being introduced, and I thank you for doing so. I was reluctant to introduce it myself as invariably, as often witnessed on this site, whenever Spencer is referenced to support an argument, Spencer's credibility is questioned and thus by association, used to question the credibility of the argument being put. With the Spencer experiment having now been introduced, it allows what he measured to be compared to what BOM measure and record as the terrestrial minimum temperature. The obvious difference is that BOM only record the minimum whilst Spencer tracked it continuously. However Spencer claims that his insulated box is a crude IR thermometer and that he is measuring infrared radiation of heat energy resident in the sky, whilst BOM are measuring ambient temperatures at ground level with a simple thermometer totally exposed on all sides. The first question is really whether or not Spencer is measuring anything different then what a simple thermometer lying on the ground measures? The second question relates to the principle of back radiation which has it that the heat contained within any body also radiates outgoing energy even though it is receiving incoming energy. If the temperature on the ground falls below the temperature of the air just 1.2m above it, why then is not the outgoing, or back radiation of that body of air received by the air just immediately below it? The theory of the transfer of thermal energy by radiation does not explain it, however the principle of convection does. The other point that Spencer's experiment is relevant to relates to earlier points made about how the high temperatures that the direct solar radiation produces at the surface are a greater force driving evaporation than back radiation. In his experiment he found that during the day the solar radiation caused temperatures that flat-lined for about an hour at the limit of the instrument, that being 158F. He expressed surprise at seeing temperatures so high, which in turn really surprised me. I would have thought that EVERYBODY knew just how hot anything receiving direct solar radiation can get. This is really school-kid stuff with most people learning early by burning their hand picking something up off the ground. This perhaps relates to another of my concerns, that being that despite all the claimed knowledge of the physics and theories, a large number of people have little or no knowledge of how it all manifests itself in the real world on a daily basis. -
Daniel Bailey at 06:47 AM on 16 September 2010It's not bad
Re: Johngee (39) Welcome aboard. There's room for all here. At Real Climate, Climate Progress, Deep Climate, Rabett Run, Open Mind, Only In It For The Gold (the list of quality science blogs is very long). I lurked for about 18 months before I started chiming in. There's a ton of basal and ancillary background material to digest. If you're interested, go to Real Climate to the Start Here tab & find your comfort level. Any questions I can help with, just post. Welcome aboard. The Yooper -
The contradictory nature of global warming skepticism
@Baz >Would you be choosing it too, if it was saying what you want to hear? I'm not "choosing" anything, I'm looking at all the data as a whole, including the HadCRUT and the ECMWF data. You on the other hand are choosing one particular time frame of one particular dataset on which to base your entire position. The best "rational" justification you can provide for this logic is because it is from "where you live". Sorry, but that's pathetic. Either you are a troll, or you lack a basic understanding of how scientific reasoning works. -
Michael T. at 06:43 AM on 16 September 2010European reanalysis of temperature confirms record warmth in 2010
Global Temperature Anomaly Map - August 2010 http://data.giss.nasa.gov/cgi-bin/gistemp/do_nmap.py?year_last=2010&month_last=8&sat=4&sst=1&type=anoms&mean_gen=08&year1=2010&year2=2010&base1=1951&base2=1980&radius=1200&pol=reg -
Daniel Bailey at 06:34 AM on 16 September 2010The contradictory nature of global warming skepticism
Re: Baz (204) Thank you for re-centering and distilling your position. If I understand you correctly, you wish to know from the readership here:1. How the "AGW hypothesis" may be proven false. 2. What length of time is needed in time series data involving temperatures to be statistically significant?
Am I reasonably close? I will assume I am, at least for now. Question 1. Reasonable question. Let me first offer up a clarification: it is something of a misnomer to refer to it as the "AGW Hypothesis" when in reality we are discussing the greenhouse gas effects of CO2, whether naturally-occurring or produced by man via the combustion of fossil fuels. Let's break it down, a step at a time:1. The greenhouse effect of certain gases was discovered by Joseph Fourier in 1824. Without the effects of greenhouse gases raising the Earth's temperature, the average surface temperature would be about -18 degrees C (i.e., no liquid water and thus no life). Based on that effect, increasing the level of a greenhouse gas in a planet’s atmosphere, all else being equal, will raise that planet’s surface temperature. 2. CO2 is a greenhouse gas (first reliably experimented with by Tyndall 1858 and first quantitatively reported by Svante Arrhenius in 1896) . Arrhenius, BTW, predicted a temperature response (sensitivity) due to a doubling of CO2 to be about 3 degrees C (the mid-point of the accepted range of 2.0 - 4.2 degrees C currently accepted). He was right in the magnitude, but had some details wrong (but in his defense, the sum errors mostly cancel out. Translation: he got it right because he was lucky). 3. CO2 is rising (Keeling et al. 1958, 1960, etc). Well established. Being a well-mixed gas, stable global concentrations are reached quickly. Monitored for over 50 years, seasonal variations and all. 4. Therefore (given 1-3 above) the Earth should be warming. Multiple, independent lines of evidence shows that this is the case. Listed in next line item. 5. From multiple converging lines of evidence, we know the Earth is warming (NASA GISS, Hadley Centre CRU, UAH MSU, RSS TLT, borehole results, melting glaciers and ice caps, etc., etc., etc). Looking at all of the data we have, over time, we know the Earth is warming. 6. The warming is moving in close correlation with the carbon dioxide (r = 0.874 for ln CO2 and dT 1880-2008). Based on the known physics of greenhouse gases, all computable by hand (i.e., no computer needed) the amount of warming predicted by the radiative physics of GHG's and the physical relationships of solids, liquids and gases, very closely matches observed increases. I cannot emphasize this point enough: this is basic physics, not some fancy GCM. 7. The new CO2 (as shown by its isotopic signature) is mainly from burning fossil fuels (Suess 1955, Revelle and Suess, 1958). We can reliably differentiate between naturally-occurring CO2 present in the carbon cycle and that produced by the burning of fossil fuels. And that produced by volcanoes (fossil fuel emissions of CO2 are 100 times greater every year than that produced by all the volcanoes in the world). 8. Therefore the global warming currently occurring is anthropogenic (caused by mankind).
So, in order to disprove the "AGW Hypothesis" one merely needs to provide a physical basis for why the fossil fuel CO2 concentrations chemically don't interact with our physical world like CO2 that is already a part of the natural carbon cycle. Looking back into the paleo record, we see a tight relationship between temperatures and CO2 concentrations. The only thing different today is that fossil fuel CO2 contributions have raised CO2 concentrations 40% above the highest levels occurring during the interglacials of the past several hundred thousand years. And the world is warming. And it continues to this day. And will continue to do so (with normal seasonal variability/noise), as long as man continues to raise CO2 concentration levels. Question 2. 30 years. Here's one source for that. If you want something a little less "math-ey", look up the World Meteorological Organization (WMO) definition of climate. 30 years: anything less is weather. So there you have it. Quibbles about atmospheric temp increases (warming) vs ocean (warming) vs North America (warming) vs the Arctic (warming vs the Antarctic (warming) are just that: quibbles. If you have a physics-based alternative to the observed & predicted effects of CO2 and GHG's that explains what we can see and measure that ALSO explains why CO2 derived from fossil fuels DOESN'T act as a GHG, then I'm all ears. And I also expect a formal submission of that alternative to a reputable, peer-reviewed (which eliminates E&E) publication for scientific review. Exxon Mobil will pay you billions, if you can do so. If, at this point, you have genuine concerns that you wish my help on, I'm here. Otherwise, all we have left is debate. And we both agree on the pointlessness of that. I look forward to our next chat. And if we don't, have a good life. The Yooper -
nealjking at 06:29 AM on 16 September 2010Why positive feedback doesn't necessarily lead to runaway warming
ClimateWatcher: I'm not really following the discussion on Dessler & Davis, but I did notice your following remark: "4. The statement: 'And finally, we point out that there exists no theoretical support for having a positive short-term water vapor feedback and a negative long-term one.' "I take this as saying: The observations must be wrong because they don't match the theory." I think it's perfectly reasonable for a paper to point out that a certain set of observations doesn't make any sense within current theory. First, it raises the stakes for the cited paper - which is not a bad thing for the authors, provided they're professional enough to know that their results were going to raise some eyelids. Other readers will focus a little more attention on it, see if it's compatible with their own experience. This is good. Second, it not infrequently happens that the experimental data ARE wrong. The UAH measurements on tropospheric warming/cooling were discrepant with ground-level temperature measurements for over 10 years, and all the climate community could say for sure was that it didn't make any sense - until the UAH team finally figured out their data analysis was in error. Likewise, I remember talking to Richard Feynman about evidence for solar neutrino oscillations, and he pointed out that the question of whether there was a real question had to do with the size of the error bars on some optical solar measurement, and if the uncertainties were just a bit more than the experimenters thought, the whole thing would be a non-issue. He said that part of the game of theoretical physics was knowing whose error estimates you could rely on. -
muoncounter at 06:19 AM on 16 September 2010Human CO2 is a tiny % of CO2 emissions
#60: " whatever we do to reduce the CO2 in the atmosphere is so negligible that it won't be seen. " How do you know that? Please cite such a claim with a reputable source. If you can find any to back it up. Consider the flip side: We've done plenty to increase atmospheric CO2 that is not negligible and can easily be observed. So your argument makes no sense. Please look more carefully at the plentiful information on this subject: Fossil fuel burning now emits CO2 on the order of 30 Gigatonnes each year, whereas the number you quote for volcanoes is in Megatonnes. Fossil fuel burning produces about twice the annual rate of atmospheric increase (after converting metric tons to ppm by volume). The remainder is stored in the oceans and/or biosphere. As far as "low" concentrations necessarily not having an effect, try hanging around an environment of 380 ppm H2S for a while. -
Adam C at 06:16 AM on 16 September 2010The contradictory nature of global warming skepticism
Dear Baz; If you don't want to be accused of making "strawman" arguments, don't make them ("Scientists claim to KNOW the future"). If you don't want to be accused of cherrypicking, don't do it (the last 10 years support my argument but the last 15 don't, so I'll stick with 10). Also, if you don't want to be accused of "argument from authority", don't base your claims on being a self-proclaimed expert ("I work with acids, so you're wrong"). And if you don't want to be accused of "appeal to the people", don't pretend that the "man-on-the-street" is more knowledgeable than the experts - especially when you have no evidence that popular opinion agrees with you anyway. The reason these are all termed logical fallacies is that they represent faulty reasoning. You don't impress anyone here by saying "I work with acids", and it doesn't convince anyone when that's the basis for your argument. -
nealjking at 06:05 AM on 16 September 2010Why positive feedback doesn't necessarily lead to runaway warming
Chris, - I used the 4-micron band for illustration, because CO2 doesn't share it with H20, unlike the 15-micron band. So it's a conceptually clearer example to discuss. - I started to use the term photosphere to describe the (radial) altitude level at the "atmospheric edge" for a specific frequency, because of seeing solar-physics photos. I'm not against using standard terminology; but I don't particularly care for "height level" because it sounds so "flat-Earthish", whereas I want to convey the mental image of a photon doing a random walk through a spherical space (well, a spherical space with a big rock in the middle! 3-dimensional equivalent of an annulus). - Yes, when I write something up, I may run it past you. In the meantime, maybe you would know the answer to this question: It's my impression that CO2 is quite significant up to 100 km, whereas H20 vapor quits at around 10 km. Is this true? And at about what altitude does the optical path length = 1 for the 15-micron band? (Where is the 15-micron "photosphere"?) -
Albatross at 05:56 AM on 16 September 2010The contradictory nature of global warming skepticism
e @217, Maybe I can help. Someone seems to be under the impression that GISS uses "proxies" for their Arctic temperature data-- what they mean by that they have not said. For someone accusing others of being close-minded I find it ironic that the person in question refuses to consider other datasets. Anyhow, the HadCRUT data show statistically significant long-term warming, as do the other data. -
The contradictory nature of global warming skepticism
e. I don't 'reject' their conclusions as such. They MAY be right, but it's not a certainty! It's just a conclusion! Yes, the UAH and RSS is interesting. As I understand it, both have suffered as a result of satllite drift, and there has to be corrections made for altitude drop (IIRC). They don't measure temperature, remember, but oxygen - and they're not calibrated. I have already explained that I choose HadCRUt merely because it is from where I live! Would you be choosing it too, if it was saying what you want to hear? Oh, I think you would! If HadCRUt showed a huge incline that even embarrassed GISS, then I know that it would be being massively exposed! -
The contradictory nature of global warming skepticism
Baz >Would you have drawn attention to ECMWF's report if it had concluded that Hadley's range was at the upper end? You have evaded my question, or are you saying you reject the ECMWF's conclusions because you believe AGW is false and will reject anything that contradicts that belief? I accept the conclusions of the ECMWF because they are consistent with multiple other data sets and because they are endorsed by the Met Office itself. In short, I can see no rational reason why I would reject it, so I am curious, why do you? You mentioned the GISS again, how about the UAH and RSS satellite data? Both show the past ten years continuing along approximately the same trend line as before. Again, how do you justify picking the data set you did while ignoring all others, including the analysis of that same data set? -
The contradictory nature of global warming skepticism
archiesteel. Ask yourself why I'm answering EVERYONE else but not you. Is it because your points are more clever than theirs, and that I have no counter-arguments to your points? Is it, mate? Really? -
angliss at 05:33 AM on 16 September 2010The Pacific Decadal Oscillation and global warming
There's a problem with this explanation, I'm afraid. The PDO index can't be directly compared to rising temperatures because the index is detrended first. From the header to the PDO data, "The monthly mean global average SST anomalies are removed to separate this pattern of variability from any 'global warming' signal that may be present in the data." -
The contradictory nature of global warming skepticism
KR. Five years was mine alone. I'm evidently not a scientist, but that '5 years' was typical of the man-in-the-street whether it's acceptable to those in the field of the sciences or not. As I stated, I jumped off the horse early. There were people who got off the Titanic when it sailed from Belfast to Southampton, before it voyaged across the Atlantic - but they weren't scientists. I accept your 30 years - thanks for answering. -
The contradictory nature of global warming skepticism
e "What more do you want?" NO MORE! I am merely responding to questions - I have pointed out many, many times that the figure is 15-20 years - how did you miss it? -
The contradictory nature of global warming skepticism
KR, I take your point. However, I don't claim scientific evidence, statistical significance, from such a short time frame! As I have stated many times, I was looking for time frames from those here! -
The contradictory nature of global warming skepticism
Baz - If you want a time period, I would say (given the noise in temperature variations and data) that if we saw statistically significant flattening or better yet cooling (because I really don't like the implications of ongoing temperature rises), that would be 15 years for considering the idea, 20 years for cautious agreement, 30 years for strong agreement, if the statistics hold up (i.e., no big changes in data variability - that would require considering the data on those merits). Note that this would include both atmospheric and total ocean heat content cooling; consistent signs of less energy accumulation in the entire Earth/air/water system, as opposed to oscillations between different heat stores or the PDO. Note that this timeframe is not a linear scale! The shorter the time frame the faster the statistical confidence drops. 10 years doesn't tell you much at all (impossible to conclude anything of significance), 5 years is just laughable. -
The contradictory nature of global warming skepticism
e at 202. I don't think you can say that HadCRUt is "flawed" yet allow GISS with its proxy Arctic data to be any more valid! Would you have drawn attention to ECMWF's report if it had concluded that Hadley's range was at the upper end? No, of course not! For a very good reason, because you believe that AGW is totally real and that HadCRUt is under-reporting it. I'll stop using their data when they do! -
Skepticalenergyguy at 05:21 AM on 16 September 2010Human CO2 is a tiny % of CO2 emissions
Okay, since CO2 is only about 0.0360% of the atmosphere, is it really that big of a deal? Come on now, whatever we do to reduce the CO2 in the atmosphere is so negligible that it won't be seen. People continue to breathe and fart. What goes in, must come out. How about carbonated sodas, beer, and paintball guns? What effect do those have on the atmosphere? "Iceland volcano causes fall in carbon emissions as eruption grounds aircraftCooling effect from volcano ash cloud will be 'very insignificant', but flight ban stops emission of estimated 2.8m tonnes of CO2" but from the same article, "Worldwide, the US Geological Survey says volcanoes produce about 200m tonnes of carbon dioxide every year." I better stop now, turn off my computer and put a gun to my head, so as to not upset the balance of CO2. Oh wait a second, firing a bullet produces CO2!, I better hang myself. -
archiesteel at 05:20 AM on 16 September 2010The contradictory nature of global warming skepticism
@Baz: nice try. There is no reason to believe temperatures are "flat" when looking at a non-statistically significant 10-year period, and then refuse to acknowledge temperatures have been going up dramatically in the non-statistically significant 3-year period. The fact you're refusing to respond to me directly isn't because I wasn't polite. Rather, it's because you have *no* counter-argument that wouldn't also damage your own position. Checkmate, mate. -
The contradictory nature of global warming skepticism
Baz > However, you should recognise that I came on here looking for an answer from those present on what they would accept as 'the' period to conclude that the AGW hypothesis may be false. We're dealing with statistics here, so there is not going to be a single hard number. In any case, you've gotten your answer multiple times: 15 years to establish a bare minimum of statistical significance, and enough to perhaps cast doubt, 25-30 years to establish a long term trend with high confidence. What more do you want? -
The contradictory nature of global warming skepticism
Daniel, your ra-ra support of archiesteel's "3-year trend" is mis-placed, as it shows that your question to me of what was I trying to achieve now holds no credibility. -
archiesteel at 05:16 AM on 16 September 2010The contradictory nature of global warming skepticism
@Baz Oh, and before you point out Berenyi Peter's comments in that thread, you should know he refuses to address the accusations of scientific fraud leveled at him, accusations that put his entire credibility at risk. If you are truly objective, and value actual research over BP's cherry-picking antics, then you have no real option but to acknowledge that oceans have continued to accumulate heat over the past decade, and have increasingly done so over the past three years. -
citizenschallenge at 05:14 AM on 16 September 2010The Pacific Decadal Oscillation and global warming
I always thought > but never see anything on it - that the PDO is related with Pacific Ocean water mixing dynamics. Can anyone speak to that? -
archiesteel at 05:12 AM on 16 September 2010The contradictory nature of global warming skepticism
@Baz: "Perhaps you would feel more at ease if we looked at ocean temps instead. I'm sure you understand that we could talk about them, and that I may be on safer ground (given the lack of heat content over the past few years)." But the oceans *have* been warming over the past few years! Here is the article on SkSc Also, you haven't told me what you think about the warming "restarting" with a vengeance in mid-2007? "Daniel, I certainly don't have the time for pointless debate, and that's exactly why some on here haven't had their 'questions' answered." How convenient. -
The contradictory nature of global warming skepticism
Paul Daniel Ash. There was only one question mark in your 177, and I responded. Do you want to debate rising ocean heat content, or falling ocean heat content? Or do you want to debate the fact that it's still unclear, and that it may falsify the AGW hypothesis long before surface temperatures do? -
The contradictory nature of global warming skepticism
Daniel Bailey. Thank you for your post. Yes, of course I understand the importance of using long time spans for revealing trends in surface & sea temperature change. However, you should recognise that I came on here looking for an answer from those present on what they would accept as 'the' period to conclude that the AGW hypothesis may be false. Perhaps you would feel more at ease if we looked at ocean temps instead. I'm sure you understand that we could talk about them, and that I may be on safer ground (given the lack of heat content over the past few years). However, it is the surface & sea temps that politicians and journalists use, so I simply wanted to pose that question. I could equally have said, 'For how long should we observe no increase (or even decrease) in ocean heat content before we conclude that the AGW hypothesis is false?' I assume you're referring to realclimate when you ask about the contributions of publishing professionals - is that correct? Having read the site on many ocassions then I conclude it's not worthy. However, if you are referring to something particular I've said, then please say precisely. In short, I certainly require to learn more, but I feel there are far too many closed minds in both camps. The subject of AGW is often likened to Creationism. However, there are totally closed minds in Creationism, again on both sides, but neither is provable. Of course, Creationism is a nonsense, and not worthy debating. But with AGW a period of time should 'prove' the issue one way or the other. What I've been exploring here is that time period. But as I said, we could look at the heat store (oceans) rather than the time-lagged result (atmosphere) and ask ourselves if heat is being accumulated. Daniel, I certainly don't have the time for pointless debate, and that's exactly why some on here haven't had their 'questions' answered. I find this sort of poking extremely tiresome, and surely for another forum entirely. -
The contradictory nature of global warming skepticism
Baz - In regards to statistical significance, you might benefit from looking at the Phil Jones says no global warming since 1995 thread. There are some useful discussions there on what timeframe is appropriate for statistical significance, and what time periods are usable for drawing conclusions. As headlined in a British paper early this year, Phil Jones (climatologist) stated that the warming since 1995 was not statistically significant. By this he pointed out that the statistical chance of the null hypothesis (no warming) was at 8% - it should be under 5% for the 95% confidence generally used in statistical significance tests. Given the noise (weather, yearly variations) in the temperature trends, 30 years is considered the appropriate period, not 15. And the global warming trend from 1980 to 2009 (just over 1 degree Fahrenheit) is statistically significant at the 99.9999 percent level. That is to say, given the data, there is only a 0.0001 % chance that it wasn't warming over that 30-year time frame; that the resulting data was due to a noisy but not trending signal. You can certainly make claims of personal belief from 10 years of data - that's up to you. However, you cannot claim scientific evidence, statistical significance, from such a short time frame. The numbers don't support it. -
Johngee at 05:00 AM on 16 September 2010It's not bad
All taken on board Dan. Watched the lecture. Very good indeed! I'd like to comment on Monckton/congress thing myself but everytime I try my voice gets lost in a scream of discombobulation. -
The contradictory nature of global warming skepticism
@Baz, Multiple posters have pointed out that the HadCRUT data has been shown via independent analysis to be underestimating warming over the last decade due to low arctic coverage. So not only do you have only one temperature series out of many (not just the GISS) that even barely suggests flattening temperatures, but in addition that temperature series has been shown to be flawed. According to this analysis, it is irrelevant at this point whether a 10 year flattening is statistically significant or not, because such a flattening did not happen. This is a critical issue for your argument, since you've decided to rest your entire position on this single data set. Is it any wonder you've been accused of cherry picking? How exactly do you justify using this single flawed data set while ignoring all others? Note that the press release I linked to above came from the Met Office, the parent organization of the Hadley Centre. The Met Office clearly agrees that their own data is incomplete. How do you justify putting your trust in the Hadley Centre when their data shows flattening temperatures, but dismissing them when they claim that same warming was underestimated? What do you call this if not cherry picking? -
Chris Colose at 04:29 AM on 16 September 2010Why positive feedback doesn't necessarily lead to runaway warming
Tim The Tool Man, I'll try another way. Imagine you are looking down at the planet from outer space and you are wearing some sort of glasses which allow you to see in the infrared. Furthermore, you also have the ability to distinguish between different wavelengths of infrared radiation. Just for the thought experiment we'll ignore water vapor and other greenhouse gases and focus on CO2. What you'll see if the planet has no greenhouse gases (from space) is all of the infrared radiation emanating from the surface and being received by your glasses. For a no greenhouse atmosphere, this radiation will roughly correspond to the surface temperature (as given by the Stefan-Boltzmann law). Now if we bump up the CO2 amount to, say, 10 ppmv then from space still you will see a lot of Earth's radiation from space coming up from the surface. These are the window regions where CO2 is a poor absorber. But in regions where CO2 absorbs strongly, you will see some radiation coming from near the top of the atmosphere. It is much colder here and so the emission you are seeing is "weaker" than the surface radiation. The dominant CO2 feature for Earth is actually the 15 micron region, not 4 (The 4-micron region is actually a stronger band, but this really can't be that crucial because Earth's Planck-weighted emission at this wavelength is very small, although it matters more for a planet like Venus). If you keep the temperature fixed, the Earth is now emitting less radiation to space, because now the OLR is the original minus the "bite" in the spectrum due to the CO2 band. The Earth's goal is radiative balance, and so the only way to get the original back (to compensate for the loss due to CO2) is to increase the temperature, which increases the whole area under the curve of a Planck radiation plot. This means the decrease in emission from the 15 micron spectral flux is compensated by an increase from window regions such as at 10 microns. This spectral selectivity is also key to understanding stratospheric cooling by the way. Eventually (at relatively low concentrations) at the center of the CO2 band, the emission from space is coming from as high as you can really get. In fact, at current concentrations of CO2 near the band center right at 15 microns, your glasses are seeing emission from the lower stratosphere. So, generally the OLR is greatest for regions of a warm surface that is overlaid by a dry, cloudless atmosphere and least in the polar regions or regions where you have cold cloud tops. Outside of the 15 micron center (but still within where CO2 strongly absorbs, at the edges) you are seeing emission somewhere between the surface and tropopause. This height of emission will clearly increase as you add more and more CO2. This "height level of emission" is what neal is referring to as the photosphere (it's not generally a term you'll see in the literature or conversation, but I don't suppose there's anything wrong with it...it's usually applied to the outer layer of the sun when climatologists talk). The key to the saturation arguments out there are that there's always more absorption waiting out in these wings, and depending on the wavelength you can always have an impact by increasing the height of emission to space, which reduces the OLR for a given temperature. So if you're doing government work and don't need super-fancy science you can model the emission from a planet with a greenhouse effect as something like T to the 3.9th power or whatever. To summarize, the best way to think about the greenhouse effect without getting into all the subtle spectral details is that for a given temperature, the outgoing radiation to space is reduced when you add GHGs. So if you don't change the incoming part of the radiation from the sun you need to warm up by a certain amount to get back in that radiative equilibrium. Note that a lot of the basic internet descriptions focus on the enhanced downward infrared emission to the surface but this is not really a good way to think about it because it's not necessarily inevitable more CO2 will directly increase the downward emission (like if you have a lot of water vapor in the boundary layer so it's already a blackbody at a given temperature) so most of the increased downward emission will actually come from increased temperature. Then, the surface energy budget is also linked to evaporation and other fluxes, so the enhanced CO2 problem is really a top of atmosphere centric focus. I've done a more complete post on this here (and if neal wants help with his future guest post I will be glad to!) -
werecow at 03:36 AM on 16 September 2010Does more extreme rainfall mean more flooding? Answer: Not always
Very interesting post and topic. I look forward to future installments. -
Daniel Bailey at 03:19 AM on 16 September 2010The contradictory nature of global warming skepticism
Re: archiesteel (200) Nice point with that three-year trend. Ouch. The Yooper -
archiesteel at 03:13 AM on 16 September 2010The contradictory nature of global warming skepticism
@Baz: one last point, since you seem not to care about statistical significance. What do you think about the fact that there has been a tremendous warming increase for the past three years? Isn't that enough to tell you that global warming has restarted? -
Paul Daniel Ash at 03:11 AM on 16 September 2010The contradictory nature of global warming skepticism
All that I require is that global temperatures resume - that's it! You'll forgive me if I find this an unserious reply. As Daniel Bailey says above "The explanation that is best representative of the whole of the data is most credible." Can you explain what you find lacking in this approach? Any response to the other information in my comment? -
archiesteel at 03:07 AM on 16 September 2010The contradictory nature of global warming skepticism
@Baz: Daniel Bailey explained it better that I could. Personally, it seems clear to me you are not interested in a rational exchange of ideas since you continue to estimate the slower warming in the last 10 years is significant enough to warrant you "changing your mind," when from a statistical standpoint it clearly isn't. *You* don't get to decide what is statistically significant. You've made your case. People have provided counter-arguments. You've ignored the counter-arguments, restating your initial position. In other words, you are not here to learn, but to push your opinion. This isn't the right forum for this. Please go repeat your debunked claims elsewhere, thanks. -
archiesteel at 03:01 AM on 16 September 2010The contradictory nature of global warming skepticism
@Eric: "The populations you listed as not threatened by hunting (e.g Baffin Bay) clearly are." Actually, *only* the Baffin Bay population is cited in the study as being over-harvested. Meanwhile, Taylor claims there is no decline, and that the population as a whole is not over-hunted (thereby destroying your argument): "For the most part, polar bear populations have increased or remained stable under the current regulatory regime. Reductions to some populations due to over-hunting were identified, and these populations appear to have recovered or are recovering." So Taylor argues there is no reduction, which puts him at odds with both the Norwegian researchers (who claim populations are going down due mainly to CC) and you (who claim populations are decreasing due to over-hunting). This is exactly what I mean by cherry-picking: the only reason you'll cite Taylor is not because you agree his methodology is sound, but simply because you can mine his letter for a single instance where he appears to support your position (when in fact he doesn't, as the Baffin population is the only one he mentions suffered from over-harvesting). So, again, you have utterly failed to indicate that over-harvesting is the main factor responsible for the decline in polar bear numbers. Sorry. -
ClimateWatcher at 03:01 AM on 16 September 2010Why positive feedback doesn't necessarily lead to runaway warming
>"I really can't make sense of the rest of your >argumentation, no one else seems to be paying >much attention, and it clearly does not derive from >the relevant scientific literature so I'm just going to >take it as an ill-supported opinion and leave it at >that." If you have a specific question, I will gladly answer it. >For those who can't access this in press article, >this is the abstract: [re "Dessler and Davis in JGR"] Thanks for the link. This paper does provide some evidence of alternate humidity estimations that indicate increasing trends in water vapor aloft. That differes from the trends than the NCEP analysis, the ICCSP analysis, and the NVAP analysis: http://www.google.com/url?sa=t&source=web&cd=6&ved=0CC0QFjAF&url=http%3A%2F%2Fams.confex.com%2Fams%2Fpdfpapers%2F84927.pdf&rct=j&q=nvap%20paper%20von%20der%20haar%20water%20vapor&ei=x_SQTKf8M4OesQOv0cGyDg&usg=AFQjCNGSAZn3mjAW50coTgiXDs1bVnC4VQ&cad=rja The exceptions I would take to the paper are: 1. The focus on El Nino fluctuation to validate long term variation is not relevant - El Nino is a known internal DYNAMIC variation. It could easily be that the DYNAMICs which change the temperature also change the humidity and not the thermodynamics. In other words temperature and humidity are both forced by dynamic changes and are just co-variants. 2. The differing periods of the various analyses. 3. The analysis which indicates the greatest increases in humidity, the MERRA, is the high outlier, with the greatest variance from not just the NCEP, but the JRA as well. That doesn't mean it is not correct, but it bears watching. 4. The statement: "And finally, we point out that there exists no theoretical support for having a positive short-term water vapor feedback and a negative long-term one." I take this as saying: The observations must be wrong because they don't match the theory. -
Daniel Bailey at 02:58 AM on 16 September 2010The contradictory nature of global warming skepticism
Re: Baz (198, et al) I am on record as according you time to present your case, backed by references, before any label-attachments are made to your name. You haven't helped me out much. You cite one data source (HadCRU) which has the known weakness of omitting the Arctic, where other temperature series reflect the significant warming there. To form an opinion based on partial data doesn't reflect well on credibility. Hence some calling you out on a "cherry pick". The explanation that is best representative of the whole of the data is most credible. You also need to understand that, when dealing with noisy datasets such as temperature anomalies, short time series (5, 10, 15, 20 years) simply fail to achieve statistical significance relative to time series' of greater than 30 years or more length. The bare minimum, under theoretical optimum low-noise conditions, to achieve significance significance is 15 years (Tamino did a post on this some time back). The scientific consensus for significance in temperature changes is 30 years or more of data. Look it up. Help me out here and show you understand this much. No one here wants to see anyone come here and "not get it". We're here to help, that's why we try very hard to understand (we each have differing abilities in communication skillsets as well). This site is about outreach. You also state that you don't value the contributions of publishing professionals in the field. Help me understand, why are you here if not to either:1. Increase your knowledge on the subject Or to 2. Waste our time with pointless debate?
Let me know which. If you choose #1, I'm here to help. The Yooper -
Alexandre at 02:48 AM on 16 September 2010The Pacific Decadal Oscillation and global warming
Here's a proxy based reconstraction of the PDO over the last thousand years. The correlation between global temps and PDO is not there in the last century, and it's not there in the last millennium. McDonald & Case 2005 Variations in the PDO over the pas millenium -
Scrooge at 02:41 AM on 16 September 2010The Pacific Decadal Oscillation and global warming
Very clear and easily understood post. What speaks volumes is the cool phase being caused by warm temps in the north. Something I didn't realise but makes perfect sense even to a layman like myself. For 2 the South Florida Regional Planning Council is studying that with a grant from I think the EPA -
Daniel Bailey at 02:31 AM on 16 September 2010Video update on Arctic sea ice in 2010
Re: Berényi Péter (41)"As you can see the ice is less than a foot thick (in March!). It can't be multi-year ice, can it?"
Back then the subs circled to find iced-over leads to break through. Attempting to surface through the 10-20' standard thicknesses of the multi-year ice may have exceeded the design tolerances of their construction, so it wasn't an advisable risk. An attempt had been made by the Skate to surface at the pole a year earlier, in 1958, but had to settle for a lead 40 miles from the pole. While your picture is of the Skate in 1959 in the Arctic, read the crew description of the weather that day at the pole in my earlier comment (34 above). It is likely taken at another location on another day on that selfsame trip. While there would've been some light at or near the pole even though the first sunrise of the year came 2 days later, the level of blue in the sky implies a more southerly locale. For comparison purposes, an example of artic sunset (low light-level conditions). The Yooper -
The contradictory nature of global warming skepticism
scaddenp 178. I don't value either of them! -
The contradictory nature of global warming skepticism
"Troll", "Strawman", and "Cherry-picking" so far. Oh dear! Now I know this site is better than that, because I've been reading it. Please people, I may frustrate you because I don't know as much as you, and I may fail to see your point, and I'm on the border of scepticism, but please try and not trot out the same tired old forum cliches. I won't answer your 'question' if you cannot write in a polite manner without using hackneyed phrases. -
The contradictory nature of global warming skepticism
VeryTallGuy. Can you spot your own error? I was referring to the last 10 years temp as being remarkably stable. I read the (very) few answers I got from those here on what THEY believe is a reasonable period to show that AGW is 'not a problem'/'does not exist to any great degree'. It was THAT which is 15-20 years. You may have to read all the contributions again! -
The contradictory nature of global warming skepticism
kdkd 188. You say you posed a previous question. I clicked on that link of yours and the only question mark was against a sentence where you were 'wondering' something. If you have a question then please pose it. As you'll see going right back here, if there was a question presented in a polite way then I most likely answered it. If it was smart-assed, then I did not. Some people just like to read their own words, rather than engage in a worthy debate. -
The contradictory nature of global warming skepticism
Ann, see above.
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