Recent Comments

Prev  2465  2466  2467  2468  2469  2470  2471  2472  2473  2474  2475  2476  2477  2478  2479  2480  Next

Comments 123601 to 123650:

123601. suibhne at 07:41 AM on 22 February 2010
        Is CO2 a pollutant?
        Philippe Chantreau carrot eater The definition of heat is most important and you will fall into error if you use a "pass with a shove loose definition". That's why I asked you to look up the definitions in a thermodynamics textbook. Where in the Trenberth diagram is there a violation of the Second Law? A above the Stratosphere 342w/m2-agreed? B Just above the Earths surface 390w/m2 up + (168+324)w/m2down = 882w/m2-agreed? You agree, do you not think this is rather odd? This diagram shows that the available energy at surface is almost three times that supplied by the Sun.
123602. Riccardo at 07:31 AM on 22 February 2010
        It's cosmic rays
        Turboblocke, you friend is making some confusion between Mie scattering and Twomey Effect. The latter appears to be interpreted as the explanation of the dependece of clouds albedo on droplet size. I assume this is correct. Twomey (e.g. Twomey 1977, J. Atmos. Sci. 54, 1149) did infact apply Mie scattering (with some aproximations) to clouds and not what your friend said ("greater surface area gives greater 'reflectivity'". What your friend appears to be missing is that as far as clouds are concerned one need to consider that: 1) the total mass of water is kept constant, so smaller drops means larger concentration. 2) in real clouds the droplet size is much larger than the wavelength of light (several microns and more vs rougly half a micron) 3) most of the clouds (low and medium level clouds) are optically thick and therefore single scattering aproximation breaks down. This means that the polar distribution of the scattered intensity varies only slowly, almost flat indeed. This contradicts the claim that "satellites don't measure true albedo". I'd like to add a few other comments on his claims. "models significantly over-predict temperature rise for a given level of CO2 and have to be corrected by an assumed aerosol cooling". Yes, if you give incorrect input to the models you'll get garbage for sure. Indeed, no one denies (i hope) that pollution from aerosol (sulfides in particular) has increased till roughly the '60s. Why the models should not consider this given that they do have an effect on climate? "One paper points out that there is no 'albedo' difference between southern and northern hemispheres when it is known that the aerosol concentration is much higher in the north." This is really a miopic point of view. Is albedo determined just by aerosol? No for sure. You have clouds, oceans, ice and several types of land. It is surprisingly enough that the mean albedo turns out to be almost equal in the two emisphere.
123603. Philippe Chantreau at 05:41 AM on 22 February 2010
        Is CO2 a pollutant?
        So what, you can quote a textbook with one definition and that's a big gotcha? I'm unimpressed. Heat is used loosely in many circumstances and often refers to enthalpy as well, since it can be readily translated in terms of heat. You're just playing on words, just like G&T. The wiki on heat is more informative than your definition: http://en.wikipedia.org/wiki/Heat You still haven't told us what the double sided panel was about, or where the violation of the 2nd law is. If anything you're proving that G&T are confused since they equate heat with IR in their paper. There is no heat transfer between the atmosphere and the surface. The heat transfer occurs between the surface and the atmnosphere. G&T say that, because there can be no heat transfer between atmosphere and surface, there can be no IR flowing from atmosphere to surface and that's simply stupid. The atmosphere's radiative properties owed to GH gases constrain the heat transfer, but the net heat transfer is still from surface to atmosphere. I don't know what your problem is and frankly I don't care any more.
123604. suibhne at 04:45 AM on 22 February 2010
        Is CO2 a pollutant?
        carrot eater Philippe Chantreau It has just occurred to me that perhaps you don't have any Physics text books to consult. From University Physics by Harris Benson page 382 Modern definition of Heat Heat is energy transferred between two bodies as a consequence of a difference in temperature between them. Hope that helps.
123605. Ned at 04:31 AM on 22 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        BP writes: Also, recent "global warming" is a myth. To illustrate this proposition, consider the following graph: [ snip lengthy description of DIY analysis ] Rather strange that satellites, surface stations, and measurements of ocean heat content (link 1, link 2)all perpetuate this same "myth". It's also strange that sea level continues to rise (link) due in large part to thermal expansion. Maybe you should inform the ocean that "global warming is a myth"? These are just a few examples of evidence that global warming is non-mythical. John put together a longer list back in December:
        What happened to the evidence for man-made global warming?
        • Our planet is suffering an energy imbalance and is steadily accumulating heat (Hansen 2005, Murphy 2009, von Schuckmann 2009, Trenberth 2009)
        • Animal and plant species are responding to earlier springs. Eg - earlier frog breeding, bird nesting, earlier flowering, earlier migration of birds and butterflies (Parmeson 2003)
        • The distribution of tree lines, plants, birds, mammals, insects, fish, reptiles, marine invertebrates are shifting towards the poles (Parmeson 2003)
        • Arctic permafrost is degrading (Anisimov 2006) plus warming at greater depths in the permafrost (Stieglitz 2003)
        • Global sea level rise is accelerating (Church 2006)
        • Antarctic ice loss is accelerating (Velicogna 2009), even from East Antarctica which was previously thought to be too stable to lose ice mass (Chen 2009)
        • Greenland ice loss is accelerating (Velicogna 2009, van den Broeke et al 2009)
        • Glaciers are shrinking globally at an accelerating rate (WGMS 2008)
        • Arctic sea-ice loss is accelerating with the loss rate exceeding model forecasts by around a factor of 3 (Stroeve 2007).
        • The height of the tropopause is increasing (Santer 2003, press release)
        • Jet streams are moving poleward (Archer 2008, Seidel 2007, Fu 2006)
        • The tropical belt is widening (Seidel 2007, Fu 2006)
        • There is an increasing trend in record hot days versus record cold temperatures with currently twice as many record hot days than record cold temperatures (Meehle 2009, see press release).
        • A shift towards earlier seasons (Stine 2009)
        • Lake and river ice cover throughout the Northern Hemisphere are freezing later and breaking up earlier (Magnuson 2000, Hodgkins 2005)
        • Changes to physical and biological systems across the globe are consistent with warming temperatures (Rosenzweig 2008)
        • Cooling and contraction of the upper atmosphere consistent with predicted effects of increasing greenhouse gases (Lastovicka 2008)
        • Pitcher-plant mosquitoes are genetically evolving to adapt to shifting seasons (Bradshaw 2001)
        • Distribution of plants are shifting to higher elevations (Lenoir 2008)
        See John's post for the links.
123606. carrot eater at 04:21 AM on 22 February 2010
        Is CO2 a pollutant?
        Heat transfer is the transport of thermal energy, through conduction, convection or radiation. I don't know why suibhne is trying to play with semantics, but it won't go anywhere. But let's not have that distract from the main question. Where in the Trenberth diagram is there a violation of the Second Law?
123607. Philippe Chantreau at 04:12 AM on 22 February 2010
        Is CO2 a pollutant?
        Heat, in our context is IR radiation. It is a form of energy. How exactly do you disagree with this? G&T very clearly states that no IR radiation (heat) can flow at all from the atmosphere to the surface, as a matter of principle, not degree. They have been quoted already. If you continue saying that nobody has pointed you to where they say so, you will display an obvious lack of interest for a real exchange and your posts will probably be deleted.
123608. carrot eater at 03:48 AM on 22 February 2010
        Is CO2 a pollutant?
        This is truly bizarre. Suibhne, it's been pointed out to you before. "A machine which transfers heat from a low temperature reservoir (e.g., stratosphere) to a high temperature reservoir (e.g., atmosphere) without external work applied, cannot exist — even if it is radiatively coupled to an environment, to which it is radiatively balanced. A modern climate model is supposed to be such a variant of a perpetuum mobile of the second kind." Again, this is not an argument about magnitude. It is a clear statement that G&T think there is a violation of the Second Law in here. Where is the violation of the Second Law, suibhne?
123609. suibhne at 03:11 AM on 22 February 2010
        Is CO2 a pollutant?
        carrot eater ..... The text in question in G&T has been pointed out several times already, including the figure. I asked you to show me the text and you did not. So I can only guess that you also are getting mixed up between the definition of heat and energy. If this is the case, I think that you do need to look this up in a reputable thermodynamics textbook because you obviously don't agree with me when I say it is not.
123610. suibhne at 03:03 AM on 22 February 2010
        Is CO2 a pollutant?
        Ned Steve McIntyre is very good at analysing data, he famously showed that the hockey stick graph was a joke. His site is famous for subjecting data to a more rigorous investigation than the original authors were capable of. His site does not highlight any other theories about climate change such as the solar models etc. Ned do you think that heat is exactly the same as energy? If so I think that you do need to look this up in a reputable thermodynamics textbook because you obviously don't agree with me when I say it is not.
123611. Ned at 02:27 AM on 22 February 2010
        Is CO2 a pollutant?
        I wrote: It's perfectly possible for some heat to flow from a lower temperature to a higher, as long as there's a greater flow in the opposite direction. This is the point that G&T fail to understand (or one of the points). suibhne responded: I think you are mixing up heat and energy definitions. A good thermodynamics text book will clarify the issue. No, I meant precisely what I said. The fact that the cooler atmosphere contributes to heating the warmer earth does not violate the 2nd LOT because the net heat flux is still in the opposite direction. G&T are spectacularly wrong on this, which is one (but only one) reason why their paper was greeted with such ridicule. Persisting in arguing this point, and citing G&T as if there was some merit to their nonsense, reduces your credibility and weakens the "skeptic" case. Steve McIntyre understands this, which is why he bans any discussion of G&T from his site. Here are a few examples of Steve's response when commenters have tried to bring this paper up for discussion there: "I do not want to discuss Gerlich on this site. I am not interested in expositions why the effect is impossible – it isn’t. Can people simply STOP posting 'skeptic' references on this." "Folks, I do not wish to get involved in a discussion of this paper by Gerlich and Tscheuschner. It would be far more worthwhile to discuss a good exposition of mainstream theory." Et cetera. McIntyre is smart enough to understand that hosting discussion of topics like G&T would significantly impair the credibility of his blog.
123612. carrot eater at 02:24 AM on 22 February 2010
        Is CO2 a pollutant?
        suibhne: The text in question in G&T has been pointed out several times already, including the figure. They think the greenhouse effect is in theory impossible. This is not an argument of magnitude, but of principle. And again, you can see the magnitude of the measurements. They are in line with the Trenberth diagram that you find to be absurd.
123613. Dikran Marsupial at 02:18 AM on 22 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        Berényi Péter @ 52 says: "The very concept of "forcing" is flawed. Different kinds of "forcings" act on different parts of the climate system, so they are NOT interchangeable (even if they happen to have the same number as expressed in W/m2). CO2 makes stratosphere colder, increased solar activity (20% more UV) makes it hot. Forget about forcing as a unified concept, please." The fact that the forcings act differently on the stratosphere does not mean that a direct comparison of the forcings is unreasonable in judging the effects at the surface (if only as a first order approximation). "Also, it does not make much sense to use models to predict the long term effect of some input variable if those very models are proven lacking in postdiction." As GEP Box said, "all models are wrong, but some are useful"; the models have shown useful skill at hindcasting, see chapter 8 of the IPCC WG1 report and here: http://www.skepticalscience.com/climate-models.htm "Also, recent "global warming" is a myth." Can you explain the trend in the UAH satelite data then, which shows a clear warming trend over the last 30 years? http://woodfortrees.org/plot/uah/plot/uah/mean:13/plot/uah/trend "I have pulled global land surface data from ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/v2/ and did some rather obvious things to it. Anyone can replicate. 1. selected northern hemisphere stations (82% of all) 2. considered temperature data for each month separately 3. used only uninterrupted series at least 20 years long, with no data missing 4. computed least square linear fit for all such 20 years interval 5. assigned slope to mid-year of 20 years run 6. averaged slopes for each (year;month) pair over set of stations 7. integrated slopes backwards in time, getting temperature anomalies relative to present" It is not at all obvious that this is a sound methodology: 2. Considering temperatures separately by month introduces quite a lot of extra variability into the analysis, especially as the data are temporally correlated, and separate analysis by months ignores that correlation. 6. Simple averaging of the trends will introduce a bias into the trends as the stations are not uniformly distributed around the Northern Hemisphere. An area weighted averaging (as used in the standard datasets) is required to get a real picture of the NH temperatures. 7. Integrating the slopes backward in time to get a temperature timeseries is not likely to be a robust procedure, as it will be very sensitive to any bias in the computation of the trends. There is a good reason why the standard datasets don't use this methodology, and I suspect that is it. A simple way to see this is to consider the error bars on the reconstruction, you are adding a new term for each step back, assuming the error bars are independent for each estimate of the trend, the error bars are the sum of the error bars on each trend estimate, which will get wider and wider the further back you go. "The findings are robust" Not making an adjustment for UHI makes the results less robust not more as you have not corrected for a known bias. Also robustness implies that you have analyzed the results to make sure they are sane, e.g. by checking that the average error between your reconstruction and the original data is the same at the start as it is at the end. "If anything, northern hemisphere climate is getting milder during last century, winters less cold, summers cooler. Exactly the pattern leading to long term ice sheet buildup, new glacial period coming." rather at odds with the satellite observations of arctic ice cover which show a significant decline in the arctic ice-sheet. Science requires self-skepticism (such as looking at the data to see if it is inline with your theories). It also takes a lot of hard study, which is why we have climatologists that have made it their lifes work to understand issues such as this. Having said which, I am no expert on time-series, you'd be better off asking tamino for his views on your reconstruction; he obviously does have a good grasp of time-series analysis. http://tamino.wordpress.com/
123614. joseph449008 at 02:16 AM on 22 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        @Berényi Péter:

        and did some rather obvious things to it. Anyone can replicate. 1. selected northern hemisphere stations (82% of all) 2. considered temperature data for each month separately 3. used only uninterrupted series at least 20 years long, with no data missing 4. computed least square linear fit for all such 20 years interval 5. assigned slope to mid-year of 20 years run 6. averaged slopes for each (year;month) pair over set of stations 7. integrated slopes backwards in time, getting temperature anomalies relative to present

        That's not obvious at all. How do you get temperature anomalies by "integrating slopes backwards" and what's the rationale? Isn't it easier to subtract a baseline from the mean temperature? Your claim to have found no warming trend is extraordinary, and I'm willing to bet your calculations are mistaken.
123615. suibhne at 02:04 AM on 22 February 2010
        Is CO2 a pollutant?
        carrot eater ..... The text of G&T simply does not support that. G&T are saying zero radiation from .... I think you must be reading a different copy from me. Where do G&T say that there is Zero radiation from Atmosphere to Earth! The main point I picked up was that the Woods experiment showed that radiation from the Earth to atmosphere is very small part of the total energy transfer. It then follows that re-radiation back to the surface is even smaller so that for practical purposes it can be ignored. This is quite common in Physics. A typical problem might be: A stone is dropped vertically from a cliff and lands 3seconds later. How high was the cliff.(ignore air resistance) On another tack and nothing to do with the previous discussions. What is the average path length travelled in the atmosphere by a suitable IR photon before it is absorbed by a CO2 molecule? I have heard quotes from 10m to 10 Km
123616. carrot eater at 00:42 AM on 22 February 2010
        Is CO2 a pollutant?
        suibhne So you accept both walls will absorb radiation emitted by the other wall. And that's it. The end. You've just refuted G&T. We have shown you that it is this basic concept that G&T are refusing to accept. You think it's a matter of magnitude, of just how much radiation from the atmosphere is absorbed by the surface. The text of G&T simply does not support that. G&T are saying zero radiation from the colder atmosphere is absorbed by the Earth. It's a matter of principle, and as such, the game is over. And anyway, the magnitudes are fine. They have been measured.
123617. suibhne at 00:38 AM on 22 February 2010
        Is CO2 a pollutant?
        CBDunkerson G&T have no problem with your blanket analogy -stops heat loss due to conduction and convection. The consider that heat loss by radiation is much smaller and that re radiation from the atmosphere is so small that it can be ignored. Even for radiation the heat flow is always from higher to lower temperature.
123618. RSVP at 00:24 AM on 22 February 2010
        Visual depictions of CO2 levels and CO2 emissions
        Alexandre This issue can be made as complicated as one wants. On the other hand, one can also construe a model with minimal simplicity for the purpose of making convincing arguments about AGW, or at least leave people with a proper sense of its significance. The way it stands now, with snow blowing in my face every winter, I have to see myself as a frog that needs to jump out of a pot that is going to boiling ever so slowly. Perhaps you can help me ignore the snow, and instead visualize the boiling pot in which I sit. And as you offer to answer questions, I appreciate the offer. I asked one question above. It was whether the atmosphere itself acts as a poorer radiator than solids or liquids? (in other words the ground or the oceans) And I asked this because this is the only way that the Earth could accumulate more thermal energy. (Even then, this piece of data is not sufficient, given that if nights and winters are long enough to allow a complete discharge, this would still have no incremental effect.) In either case, would you know the answer to the question? Thank you.
123619. CBDunkerson at 00:18 AM on 22 February 2010
        Is CO2 a pollutant?
        Suibhne, no Ned is completely (and obviously) correct. THINK about it. How would heat 'know' not to flow in a given direction? It doesn't... it radiates equally in all directions. There is no 'magical quantum traffic cop' preventing heat from traveling from a cold substance to a hot one. It happens all the time. However, since the hot substance is giving off MORE heat the amount flowing from it to the cold substance is greater and the NET change is always from the hot to the cold. The amount of heat coming up from the Earth is greater than the amount absorbed and reflected back (obviously, since the latter can only be a subset of the former), and thus the NET flow >is< from hot planet up into cold space... but the downward heat is greater than it would be without GHGs. It should be painfully obvious that this is true. Otherwise blankets could not work... clearly the blanket is colder than the human body so if G&T weren't liars or fools they're postulates would mean that since the human body is generating all of the heat in the 'blanket & body' system the heat MUST all flow from the body up to the blanket and the body will never be any warmer than it was without the blanket. That is, of course, complete nonsense. Some of that body heat is retained by the blanket and returned back down to the human, flowing from colder blanket to warmer human and making the human warmer than they would have been without the blanket.
123620. suibhne at 00:09 AM on 22 February 2010
        Is CO2 a pollutant?
        carrot eater ......Say you've got one wall at 25 C. Directly facing it is another wall, at 50 C. We are probably not in disagreement about this . Both walls will radiate to each other but the flow of heat is from the hotter wall to the colder. Where there does seem scope for disagreement is in the respective size of the heat loss from the surface of Earth by conduction convection and radiation
123621. suibhne at 23:54 PM on 21 February 2010
        Is CO2 a pollutant?
        Ned That's the net flow of heat. It's perfectly possible for some heat to flow from a lower temperature to a higher I think you are mixing up heat and energy definitions. A good thermodynamics text book will clarify the issue.
123622. suibhne at 23:48 PM on 21 February 2010
        Is CO2 a pollutant?
        carrot eater Thanks for posting these leads will look at them in more detail later. I realise that the diagram are discussing is averaged over say one year and you did not disagree that the readings I assumed that the thermopile would take. Yet you find nothing odd with them! Philippe Chantreau Given that we are talking about properly obtained and averaged values are you still happy with these readings?
123623. Ned at 23:37 PM on 21 February 2010
        Is CO2 a pollutant?
        suibhne writes: The flow of heat will always be from a higher to a lower temperature unless work is done. That's the net flow of heat. It's perfectly possible for some heat to flow from a lower temperature to a higher, as long as there's a greater flow in the opposite direction. This is the point that G&T fail to understand (or one of the points). Thus, the atmosphere is cooler than the surface, so there's a net flow of heat from the surface to the atmosphere. That net is a result of a large flux from the surface to atmosphere and a smaller one from the atmosphere to the surface. Warming the atmosphere will increase the latter, therefore warming the surface. The fact that G&T fail to understand this completely non-controversial and very basic point ought to clue you in to the lack of merit in their paper as a whole.
123624. HumanityRules at 23:27 PM on 21 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        Ned 26# I raised the point of regional nature of solar affects because I've seen this used to dismiss the impact of other climate processes. I agree with you on the CO2 pattern of warming, if it exists. I guess this argument can be ignored in the future as all climate change has a regional nature? Marcus #32 Graphs tend to show the MM spanning 50years within a period of 100+years of low sunspot activity rather than the 300years you suggest. There also doesn't appear to be 250years between the end of this minima period and today. Whatever the time periods are you suggesting that the LIA produced 1.5oC of cooling (given a recovery of 25*0.06)? Because even this seems higher than the modelling would allow. GFW 34 On volcanos do you have a reference for that work? I found this review which lists volcanos from 1500 on ward with DVI greater than 500. There are 3 in 1500's, 7 in 1600's, 7 in 1700's and 7 in 1800's. Given that 1750 is about the time when this cold period was ending it seems there wasn't any significany drop off in volcanic activity after this period to allow warming. Interestingly they only list 3 for 1900's, although you mention several more after the publication date, seems if you are looking for unusually low levels of volcanic activity look to the 20th C. Volcanoes and climate: recent volcanological perspectives. D. K. Chester (1988) Progress in Physical Geography 12, 1-35
123625. Berényi Péter at 23:26 PM on 21 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        #0 Posted by John Cook at 14:14 PM "it's helpful to compare the radiative forcing from a cooling sun to the radiative forcing from anthropogenic greenhouse gases" No, it is not. The very concept of "forcing" is flawed. Different kinds of "forcings" act on different parts of the climate system, so they are NOT interchangeable (even if they happen to have the same number as expressed in W/m2). CO2 makes stratosphere colder, increased solar activity (20% more UV) makes it hot. Forget about forcing as a unified concept, please. Also, it does not make much sense to use models to predict the long term effect of some input variable if those very models are proven lacking in postdiction. Also, recent "global warming" is a myth. To illustrate this proposition, consider the following graph: http://kign.org/Northern_hemisphere_temperature_anomaly.jpg I have pulled global land surface data from ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/v2/ and did some rather obvious things to it. Anyone can replicate. 1. selected northern hemisphere stations (82% of all) 2. considered temperature data for each month separately 3. used only uninterrupted series at least 20 years long, with no data missing 4. computed least square linear fit for all such 20 years interval 5. assigned slope to mid-year of 20 years run 6. averaged slopes for each (year;month) pair over set of stations 7. integrated slopes backwards in time, getting temperature anomalies relative to present Findings: 1. No warming for summer since mid thirties of last century. In fact, there is a 0.2°C/century cooling trend. 2. No warming for July. In this case the cooling is 0.6°C/century. 3. Springtime warming stopped in mid eighties 4. Only winters are getting consistently warmer, even this trend is flatting out recently (since 1995) 5. Otherwise annually averaged temperature anomaly trend looks like advertised The findings are robust. 1. Have not made any adjustment for UHI (Urban Heat Island) effect. Warming is overestimated. 2. Gregorian calendar effect is not corrected for. Since 1900 spring equinox is moving to ever earlier dates which introduces a spurious springtime warming trend. It will be reset only in year 2100 with no 29 February in that year. If anything, northern hemisphere climate is getting milder during last century, winters less cold, summers cooler. Exactly the pattern leading to long term ice sheet buildup, new glacial period coming. GHCN data go back to mid eighteenth century. It is not shown on graph (more cranky, wider margins of error), but looks like winters were even colder back then (up to 3°C) while there is no trend in summer temperatures. Little ice age was not uniformly colder, perhaps. At he end of 1820s summer temperatures were just as warm as they are today, winters much colder. How do models replicate this pattern for reduced solar activity?
123626. suibhne at 23:25 PM on 21 February 2010
        Is CO2 a pollutant?
        doug_bostrom The flow of heat will always be from a higher to a lower temperature unless work is done. Heat can be prevented from flowing by addressing conduction convection and radiation issues I think we are all agreed on that I hope. Where the disagreements arise is on the overemphasis on radiation. I have a Physics degree and even my Thermodynamics textbook by Adkins(1985) gives the now abandoned Greenhouse explanation. Apparently he was not aware of the experiment by Woods. It was therefore important that G&T should clear up any doubts on the matter.
123627. BC at 23:17 PM on 21 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        I've just figured it out. It'll be a randomly placed volcano.
123628. ThosThos at 22:57 PM on 21 February 2010
        Did Phil Jones really say global warming ended in 1995?
        Can I try and clarify for the non-statisticians the importance, or otherwise, of statistical significance. Statistical significance, in the current context, means that 95% of the time we can be satisfied that our trend is valid. The uncertainty lies in the fact that we are not looking at all possible data, either because we do not have it, or because we are choosing a subset. As Jones says, the longer the period we are looking at data, the more certain we can be that trend is meaningful, and the less stringent the significance level has to be. Lack of statistical significance can be overcome by choosing a lower significance level. For example, at the 90% level, we can say that trend is valid 90% of the time. Obviously, lower values of trend will meet this weaker test. So, statistical significance is a statistical artifice, a means of measuring uncertainty. Lack of it does not mean a physical relationship does not exist, in this case rising trend, just that it does not pass the chosen test level. This is a major weakness of statistical relationships, particularly over a short period of time.
123629. BC at 22:35 PM on 21 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        Does anyone know why there's a fairly substantial dip in the graph, fig 2, in about 2020?
123630. Alexandre at 22:33 PM on 21 February 2010
        Visual depictions of CO2 levels and CO2 emissions
        RVSP, There's another part of the story that wasn't brought about so far, which is the energy received by the planet (that's a limitation of a blog debate as compared to a proper class, with a qualified teacher). There's the energy received from the sun, and there's the energy emitted by the planet. When both are equal, the system is in an equilibrium. The planet always "leaks" (i.e., emits energy). When you increase the CO2 you reduce that leakage. This retains energy, and causes the temperature to rise. This higher temperature, in turn, rises the emmission of energy (the Iout you saw on the mnodel) *until* it is in equilibrium with the received energy again. The leakage continues, as always. But now the temperature does not rise anymore, having reached a new balance, in a warmer planet. As always, feel free to ask any further questions. As I said, this is my pleasure. But if you have the time or energy for this, I would suggest one of the many tutorials online there are on the subject, for example: University of Chicago - the actual classes of the Global Warming Physics basics (for non-science students) on video. Online Textbook from the Université Catholique de Louvain, Belgium (in English). A slightly different, historical approach, on Spencer Weart's Discovery of Global Warming.
123631. CBDunkerson at 21:48 PM on 21 February 2010
        Visual depictions of CO2 levels and CO2 emissions
        Has anyone ever seen one of those 'energy in vs energy out' greenhouse effect charts for the estimated greenhouse at the end of the last ice age (~180 ppm CO2) and/or double the pre industrial revolution value (~560 ppm CO2)? I think a comparison of such charts (and heck, throw in a +/- variation for solar activity to show how small that is) would go a long way towards explaining things to folks like RSVP... but I've only ever seen charts for the current situation. Basically, a comparison would show how 'back radiation' is increasing and the impact that has on surface heat.
123632. Turboblocke at 21:29 PM on 21 February 2010
        It's cosmic rays
        Riccardo, this is what he says,"Reportedly, the models significantly over-predict temperature rise for a given level of CO2 and have to be corrected by an assumed aerosol cooling from the 'Twomey Effect': the apparently greater brightness ['diffuse albedo'] of clouds with smaller droplets. Twomey's explanation, greater surface area gives greater 'reflectivity', is wrong physics but plausible: I saw it recently in NASA literature so it appears to be taught in climate science as if it were a fact. The correct physics is 'Mie scattering'. Smaller droplets do lead to earlier onset of diffuse radiation. However, unless the measurement is done exactly coaxially with the sun's illumination, the backscattered contribution to the energy loss to space is not quantified. ... So, the satellites don't measure true albedo. The physicists know all about Mie scattering. One paper points out that there is no 'albedo' difference between southern and northern hemispheres when it is known that the aerosol concentration is much higher in the north." It isn't a subject I'm competent in, so I don't know if what he says makes sense.
123633. RSVP at 19:57 PM on 21 February 2010
        Visual depictions of CO2 levels and CO2 emissions
        Alexandre "There. CO2 stopped some of the radiation to escape, total energy emitted got lower, the retained energy caused the temperature to rise,..." Does the atmosphere hold on to this energy forever? Does it not also radiate? Why doesnt the tool also account for this leakage?
123634. RSVP at 19:16 PM on 21 February 2010
        Visual depictions of CO2 levels and CO2 emissions
        Riccardo at 21:23 PM on 20 February, 2010 "RSVP, indeed the atmospheric greenhouse gas effect is often (popularly) described as a blanket. Below the blanket it will definitely be warmer" Consider what happens to the heat. Instead of residing in the surface (asphalt, trees, houses, people, ocean water, etc.), some portion that would otherwise escape to infinity, is instantaneously coupled into the atmosphere and thus raising its temperature. Whatever heat is picked up by the atmosphere for GHG, is actually lost on the surface. This implies, ironically, that the Earth's surface is actually a little cooler because of the GHG. Only the air has warmed up some. The net energy stays the same however. And all of the above is only true if the radiative cooling efficiency of a transparent gas such as our atmosphere is equal to those of the surface. If the efficiency is lower, than yes, the steady state energy level will be raised for more GHG. So with this, while I am conceding a theoretical raising of atmospheric temperature. However, accumulation of heat is a separate and possibly more important question, which depends on the comparative cooling efficiency between the surface and the atmosphere.
123635. Philippe Chantreau at 18:24 PM on 21 February 2010
        Is CO2 a pollutant?
        To summarize what a couple of posts before mine say, your thermopile will never "read" these numbers because they are globally/temporally averaged flows.
123636. Pierre-Normand at 16:17 PM on 21 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        "The research was done on the Metolius River Watershed in the central Oregon Cascade Range, where about one-third – or 100,000 acres – of the area burned in four large fires in 2002-03. Although some previous studies assumed that 30 percent of the mass of living trees was consumed during forest fires, this study found that only 1-3 percent was consumed." http://www.newwest.net/...impacts_often_overestima/
123637. Ned at 14:43 PM on 21 February 2010
        Water vapor is the most powerful greenhouse gas
        A year ago, Mizimi wrote: A few sums ....various sources give our annual energy usage from FF as around 14 terawatts. That's almost certainly the power directly associated with combustion of fossil fuels, not the radiative forcing from the CO2 produced by that combustion. But, more or less coincidentally, the annual increase in radiative forcing is probably pretty close to that 14 terawatts worldwide. (Based on these data from NOAA, it looks like the annual increase is 0.03 watts/m2 which works out to about 1.5E13 watts over the planet as a whole. Mizimi continues: Looking around the Australian Bureau of Statistics gives the following population figures.... People 21 million Horses 400,000 Kangaroos 23 million Camels 400,000 Cattle (dairy and beef) 26 million Sheep 20 million Rabbits 250 million Simple maths - multiplying numbers by the basal metabolic rate at rest of each species gives a daily heat emission of 315 x 10E9 watts or 114 x 10E12 watts per annum. Whoa, do you understand the meaning of the word "watt," Mizimi? A basal metabolism of 1 watt is 1 watt, whether you measure it over a period of days, weeks, years, or millennia. If you're going to convert the metabolic data to watt-years, you need to do the same conversion for the radiative forcing! Let's redo those calculations. I can't find actual data on the metabolic rates of kangaroos etc., but I see that sheep are about 50 watts, cattle about 330, and humans about 78. Using Mizimi's population figures, that works out to a total basal metabolism of 1.1E10 watts, several orders of magnitude less than the figure that Mizimi quotes. I don't think adding in the kangaroos and rabbits would make up the difference :-) The annual increase in radiative forcing from greenhouse gases is 1360 times larger than that. In other words, every 6.4 hours we're adding a radiative forcing to the climate system that's approximately equal to the combined metabolism of all the people, cattle, and sheep in Australia. Two caveats in closing: (1) If that seems like a silly comparison, blame Mizimi not me. (2) Apologies for responding a year late ... but Mizimi's original post was so severely erroneous and had gone uncorrected for so long that I thought it would be good to set the record straight.
123638. lepton at 14:23 PM on 21 February 2010
        Water vapor is the most powerful greenhouse gas
        Ned at 13:23 PM on 21 February, 2010 writes: "More than anything else, it was studies of the process of CO2 uptake by the oceans that set off alarm bells about global warming in the 1970s and early 1980s. Until then people thought most of the CO2 we emit would end up in the oceans. When it became clear that this would take a long, long time to happen, people began to realize that this is a big problem that we're facing." Thank you for valuable references. However - as a physicist (not climatologist) - I can hardly understand why the time scale of the process of the CO2 reaching equlibrium between atmosphere and ocean concentrations process might be any different from that of WV evaporation rate due to ocean-air temperature differences. Both processes are based on the same molecular mechanisms. Perhaps the culprit is the ocean surface layer - warmer than the bulk, so evaporating more willingly, at the same time accepting less CO2?. Might it be that the significant factor is the mixing of ocean? Both on surface by waves and in bulk by currents?
123639. lepton at 13:39 PM on 21 February 2010
        Water vapor is the most powerful greenhouse gas
        to villar at 20:21 PM on 2 December, 2009 Any positive feedback is the source of instability, by definition. I do regret that so many climatologists have so minimal knowledge of process control. Not every positive feedback blows a sytem up. It can also make it oscillate, like in simple systems with phase delay. In climate - an obvious complex set of interwoven processes - a positive feedback like VW induced GH effect - generally will drive conditions to the point when other (up to then dormant) processes will activate, possibly turning on some negative feedback. The very fact that Earth's ecosphere still exist after so many evidences of past climate extremities proves that (regardless of any positive feedback) our globe can always find equilibrium (if only local).
123640. Ned at 13:23 PM on 21 February 2010
        Water vapor is the most powerful greenhouse gas
        lepton writes: Antropogenic CO2 will in consequence mostly go to the oceans, and again - taking into account their far greater capacity then that of atmosphere - it should not accumulate to significant long-term levels in atmosphere making its impact on climate transient. Well, that's true, as long as you can accept a timescale of tens of thousands of years as "transient." Yes, most of the CO2 we add to the atmosphere will end up in the ocean but given the thinness of the mixed layer and the slow rate of movement from the atmosphere to the mixed layer to the deep ocean, that will take a long time to happen. In the meantime, atmospheric CO2 will almost certainly exceed 2X preindustrial levels, if not 3X. How than can be explained the rising concentrations of CO2 in the air - observational fact beyond doubt? Either it is really of antropogenic origin and then it seems to be a small problem (as it is on its way into ocean) or - CO2 is released by the warming ocean (for which I - and perhaps we - miss information), a process that can be of far more dangerous consequences. Actually, it's quite clear that CO2 is going from fossil fuels to the atmosphere to the ocean, not the opposite direction. See, e.g., the following papers: Takahashi et al. 2009. Climatological mean and decadal change in surface ocean pCO2, and net sea–air CO2 flux over the global oceans. Deep Sea Research Part II: Topical Studies in Oceanography, Volume 56, Issues 8-10, April 2009, Pages 554-577. Sabine, et al. 2004. The Oceanic Sink for Anthropogenic CO2. Science, Vol. 305. no. 5682, pp. 367 – 371. Yes, as it warms the ocean can hold less CO2, but CO2 is rising faster in the atmosphere, so there's a net flux from the atmosphere to the ocean. More than anything else, it was studies of the process of CO2 uptake by the oceans that set off alarm bells about global warming in the 1970s and early 1980s. Until then people thought most of the CO2 we emit would end up in the oceans. When it became clear that this would take a long, long time to happen, people began to realize that this is a big problem that we're facing.
123641. Leo G at 13:13 PM on 21 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        John, just read that you are a solar physicist, Nice! One of your peers, Dr. Svalgaard, is quite adamant that the change in TSI is so minute that it has no discernable relationship to cooling or warming of the planet. He even points out that at the "coldest" point of the LIA, the sun was actually on its active side! I would love to get your thoughts on this. By the way, if I addressed you as Dr. Cooke, would that be right? :)
        Response: It wouldn't be correct, I'm not a Dr (and there's no e in my surname :- ) and the Guardian was incorrect in labelling me a solar physicist (which unfortunately has spread throughout the blogosphere). I did a physics degree and majored in solar physics in my post grad honours year but I am not a professional scientist now. I'm pretty clear about this on the About Us page.
        
        I haven't looked too much into Svalgaard's work but I have actually downloaded an Excel collection of TSI reconstructions of his website - it shows a number of reconstructions revealing his version is somewhat of an outlier compared to other works.
123642. Leo G at 13:06 PM on 21 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        One other thing Ranger, remember that forest/grassland fires only have about 40-70% complete combustion. As opposed to say a good wood burning stove which can get to the 85% area. In a perfectly controlled burn scenario, most of the oxygen would combine with the carbon to form CO2. Natures own fertilizer. But in forest/grass fires, the combustion process is affected by variables that produce not only CO2 but CO. As well as NOx's, Butyls, etc. Our internal combustion technology attains a much higher percentage of complete combustion, then the open fires on ranges. Therefore they paradoxically produce more CO2! Also, perhaps the biggest thing that needs to be pointed out is that forest/grass fires are very "messy". They tend to throw a lot of soot and aresols high into the atmosphere. Now if the soot happens to fall on ice or snow, we can have a strong warming effect. But if it falls on plant covered land, we have a fertilizing effect. But the aresols that have been pushed miles high into the atmosphere will and do act as reflectors of the incoming energy from the sun. Thus from these fires, we may actually get a regional net cooling effect over the next few years. Right now in Canada, B.C. has the highest output of GHG's of any province in the country. This is from the rotting of all the pine beetle killed trees. All that bacteria that is turning the trees back to soil and energy are farting a lot. It probably would be better for the climate, from a warming/cooling viewpoint, to have let these forests burn 20 years ago. But you know, hindsight is 20/20.....
123643. lepton at 12:17 PM on 21 February 2010
        Water vapor is the most powerful greenhouse gas
        If I can comment the discussion of Chris G and Mizimi: It is very interesting and I am amazed by the level of details being analyzed. Nonetheless my impression is that keeping an eye (and mind) focused on details prevents sometimes from noticing more relevant obvious facts which can render the details insignificant. The neglected factor seem to be the stabilising impact of oceans. While it is true that raising temperature of atmosphere increases its capacity to hold more WV thus raising its potential for more efficient GH effect - to fill this capacity requires liquid water reservoirs of elevated temperature. Primary source of globe's VW are oceans, whose heat capacity is several orders of magnitude higher than that of atmosphere and it would take millenia for the air to warm them up. Over the lands water sources are less massive and thus can more readily make use of raising evaporation conditions. However - taking into account high mobility of atmosphere and effective mixing - the warming effect will be diluted (with the probable net effect being enhanced removal of moisture from lands to oceans). As to the C02 - again it is the temperature of the oceans that determines water-air equilibrium concentrations. Antropogenic CO2 will in consequence mostly go to the oceans, and again - taking into account their far greater capacity then that of atmosphere - it should not accumulate to significant long-term levels in atmosphere making its impact on climate transient. How than can be explained the rising concentrations of CO2 in the air - observational fact beyond doubt? Either it is really of antropogenic origin and then it seems to be a small problem (as it is on its way into ocean) or - CO2 is released by the warming ocean (for which I - and perhaps we - miss information), a process that can be of far more dangerous consequences.
123644. RedFishBlueFish at 10:17 AM on 21 February 2010
        There's no empirical evidence
        "Gradually the models seem to agree more and more with each other, which is hardly surprising since consensus is the key to progress here: you get your report published if it gives similar results as all the other reports, and if you don't agree you will be an outcast in the world of climate science." Actually Nobels, and other types of recognition, are not awarded for confirming previous work. Another interpretation of why the models are converging, is that they are converging on a demonstrable phenomenon - much as models of the structure of matter converged on the atomic, vs continuous, nature of matter at the end of the 19th century.
123645. Peter Hogarth at 09:36 AM on 21 February 2010
        Visual depictions of CO2 levels and CO2 emissions
        Here's a leading question which may well display my ignorance, but please answer (skeptically or otherwise!) if this is your area of expertise. Assuming a significant fraction of the global CO2 sink is (for example) the high Northern latitude forests and vegetation in the growing season, and a significant Global Methane source is high Northern latitude wetlands in Summer/Autumn, then how much of the Anthropogenic Carbon drawn down as CO2 then makes its way back into the atmosphere as CH4 through decay of some of that "extra" growth, - with potentially 21 times the Greenhouse effect??? I'm not sure if this carbon rectification/GHG amplification idea is original or even significant, but it would be interesting to run the math...
123646. Doug Bostrom at 08:19 AM on 21 February 2010
        There's no empirical evidence
        Argus, thanks for reading those. You and I differ on our interpretations of outcomes of the narrative, particularly as regards conformist thinking infecting science, but I'm really glad you took the time to grind through it all. As to email, reputations and the like, physics and mathematics are oblivious to such things; inconsistencies and errors will inevitably reveal themselves if such there are and that process will not take place via newspaper articles.
123647. joseph449008 at 08:12 AM on 21 February 2010
        What would happen if the sun fell to Maunder Minimum levels?
        

        the authors conclude the most likely impact of a Maunder Minimum by 2100 would be a decrease in global temperature of 0.1°C

        I estimated this once based on the solar irradiance reconstruction from Lean (2000). What I came up with is 0.2°C. It's not very difficult. Assume emissivity and albedo are constant. If this is the case, absolute temperature is directly proportional to solar irradiance to the 1/4th power.
123648. Argus at 08:01 AM on 21 February 2010
        There's no empirical evidence
        Doug, thanks for the interesting links to essays on climate model history! I have read it all, and learned that modelling has been a challenging area for more than 100 years. Also that the models have all been very different from each other, full of flaws and weaknesses, and afflicted with serious simplifications that diminished their value. Gradually the models seem to agree more and more with each other, which is hardly surprising since consensus is the key to progress here: you get your report published if it gives similar results as all the other reports, and if you don't agree you will be an outcast in the world of climate science. I am not much comforted, though. Climatologists don't have a very good reputation anymore, after recent scandals with emails, and the glacier bluff. I predict more awkward revelations to be made in times to come.
123649. carrot eater at 07:57 AM on 21 February 2010
        Is CO2 a pollutant?
        To clarify: the map on the last page of http://www.sciencemag.org/cgi/data/308/5723/850/DC1/2 is estimated from satellite data, but from the preceding figures you can see that the calculations from satellite data match up very nicely with actual measurements at the surface.
123650. GSW at 07:52 AM on 21 February 2010
        It's cooling
        nice article, very clear what you are getting at. Question: Don't the models take the Oceans (as a heat sink) into account? If so, how have they got it so wrong?

Prev  2465  2466  2467  2468  2469  2470  2471  2472  2473  2474  2475  2476  2477  2478  2479  2480  Next