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

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Comments 104401 to 104450:

  1. Animals and plants can adapt
    CBDunkerson, if you can tell me how reducing CO2 emissions can help reforesting the destroyed rainforests all over the world and help to regain the lost top soils (destroyed due to monoculture farming) and regain the lost wildlife habitats destroyed in the process I would like to believe you.
  2. Are ice sheet losses overestimated?
    John Kerr, Another way to approach this question is that the maximum amplitude in sea level change from the MWP potential maximum (21 cm greater than present) to the LIA potential minimum (26 cm lower) is 47 cm and can be as small as 31 cm over the last 2000 years (Grinsted et al 2010). The expected sea level rise according to Grinsted et al (2010) if there is NO additional warming (this doesn't include 2010s warm year) is between 21 to 44 cm by 2100. So not even including any additional warming we see, we will sea a sea level rise which is as great as the amplitude between the highest of the MWP and the lowest of the LIA by 2100. Kinda supercedes your natural variability theory doesn't it? Lets dive a little deeper. You may not be a glaciologist but i'm sure you have heard about dynamical ice changes which are underway in Greenland and West Antarctica correct? These ice changes are irreversible in West Antarctica (particularly in Pine Island Bay) where the bed slopes downward into the interior of West Antarctica. The losses from this region ARE accelerating, the same as they are from portions of Greenland grounded below sea level. The mechanisms are WELL-UNDERSTOOD and continued oceanic and atmospheric warming will hasten the removal of buttressing ice shelves/grounding lines and thereby accelerate flow into the oceans. But back to your initial premise. It is true that climate throughout the holocene has been to some degree variable. And it is true that the timing of the hypsithermal is different in different regions thereby causing periods of warming in the past. But since the Hypsithermal you DO NOT see spikes in sea level of 2 meters. You see *relative* stability. Oscillating climate patterns superimposed on a downward orbital signal. You can pick a core or two out as much as you want, but unless you are able to give some sort of comparison to current temperatures then its irrelevant. I could take your GISP2 core and do this: http://www.skepticalscience.com/pics/Gisp2Graphedited.png but that doesn't make it right. Showing half the evidence doesn't either... Finally, Nowhere in the article does it talk about AGW. We don't use ice losses to diagnose and attribute AGW. We use empirical evidence from a multitude of places. Just because ice losses are able to detect associations with warmth does NOT mean that we are saying this is how we PROVE it is man-made.
  3. Are ice sheet losses overestimated?
    Daniel (#15), Hmm, maybe, but your understanding of GRACE is a little different from mine. I was under the impression that the primary measurement taken by the satellites was the distance between them rather than the altitude above the surface. Differences in the distance between the satellites is primarily caused by the lead of the pair accelerating into an area of more mass and 'decelerating' as it leaves the area, and the same for the other in the pair. As far as I can tell, altimetry has little to do with it. I'm sure a mountain range affects GRACE, but I'm not sure how it would distinguish between a mountain range and a large deposit of iron ore near the surface. It is affected by local variations in mass.
  4. Climate cherry pickers: cooling oceans
    KL #37 "kdkd makes an interesting point. Clearly we have to try and pick winners here. Sort which data is crap and which might be close to correct. When there is conflicting data - the method is to look at its nature and try to find logical reasons why one might be good enough to be useful and the other not so." Indeed I do. Concentrating on the lame horses (with good genes) at the back of the field instead of the front-runners seems to be a strange way to pick winners. Or in other words, the lack of precision of the OHC and TSI measures do not falsify the other strong coherent evidence for anthropogenic global warming.
  5. It's the ocean
    #17: "As the earth's crust is thinnest below oceans this may heat the water above." Not by much. Here's what Douglass and Knox 2009 have to say about tectonic heating: The geothermal contribution is constant [certainly over human time scales], but cannot be ignored because it contributes directly. The flux into the ocean and trenches averages 101 ± 2.2 mW/m2 and that into the land and shelves averages 65 ± 1.6 mW/m2 (globally averaged, 87 ± 2.0 mW/m2) --emphasis added Compare to solar heat flux, same source: The mean solar flux S0 at the earth’s orbit is assumed to be 340 W/m2±1 W/m2 A sizable difference in favor of solar heat.
  6. Are ice sheet losses overestimated?
    John Kerr, What the mass loss for Greenland "should be" is completely irrelevant. We are not arguing that the Greenland Ice Sheet should be stable or should be in a state of continual mass balance. What you are ignoring is that the current trends from Greenland show a distinct acceleration that is far greater than what was predicted by the IPCC. Estimates of Greenland's ice losses fit an exponential curve better than a simple linear estimate. This suggests a destabilization process is occurring. If you would like to talk about the MWP and Greenland losing ice, it is pretty well understood that sea level was likely higher during the MWP. Grinsted et al. (2010) show that sea level over the past 2000 years reached its maximum around 1150 AD at around 12–21 cm greater than present. This number is much smaller than the predicted range of 0.9 to 2m (Rahmstorf 2010) that is expected by the end of the 21st century. The reason the MWP was able to have a higher sea level compared to today is because it lasted for a long time thereby allowing for the Greenland Ice Sheet to continually contribute to sea level rise. Furthermore, because of the length of the warm period the thermal inertia of the oceans was fully fulfilled. It should be noted that Grinsted et al (2010) find that if there is no further warming (from 2009 onwards) that sea levels will still surface the MWP by up to 20 cm from the MWP maximum (remember, no additional warming).
  7. Naomi Oreskes' Merchants of Doubt Australian tour
    JohnHarrington: There's another, very simple, explanation - the possibility that the woman you were talking to is incompetent, and has chosen to blame circumstances and other people rather than face up to the reality. I'd say that it's far more likely than the entire field of archeology being corrupt and incompetent. Also ... archeology is far more subjective than physical sciences like atmospheric chemistry, etc. We're unlikely to ever know just when or how the horse was domesticated, but we know for certain that CO2 absorbs long-wave IR.
  8. It's the ocean
    h-j-m #17 But more evaporation equates to more water vapour in the atmosphere (aka latent heat) which will result in warming the atmosphere. This is incorrect, I believe. The amount of water vapour that the atmosphere can hold is determined only by the temperature of the atmosphere. Factors that increase only the rate of evaporation will simply increase the rate of condensation out as well. In the atmosphere that means clouds form faster and then more precipitation. 1. Marine as any other life needs energy to build its biomass. By now we are next to successful clearing our oceans of it. In consequence that energy is not used for this purpose and heats the water instead. I would think the main route for marine life to obtain energy is photosynthesis and respiration. Indeed, given biochemistry, I would expect respiration inside marine animals to keep them at a higher temperature than the water (blubber in marine mammals would seem to corroborate this). Therefore I think denuding the oceans would most likely have a nett cooling effect. 2. There may be spots where the earth crust has grown thinner over time and therefore more of the earth's interior heat gets transferred to upper layers. As the earth's crust is thinnest below oceans this may heat the water above. This is beyond my realm of expertise, but I would note that what is actually required is a nett thinning of the crust for the oceans to get warmer. "some spots" is not, of course, sufficient. 3. Not only are we clearing out next to all marine life from the oceans we are using them as garbage bins as well. I recall reports stating that all over the oceans probes were taken that revealed a higher content of plastics than phytoplankton. I think it is rather likely that these areas when hit by visible light will absorb more of it and in return emit more infrared radiation aka heat. Phytoplankton photosynthesize (by definition) which is the absorption of visible light, I would imagine they are better at it than plastic, unless perhaps most of the plastic is black ...
  9. Are ice sheet losses overestimated?
    Whoops, Berger and Loutre is of course 2002, not 2009.
  10. Are ice sheet losses overestimated?
    TIS - "supposed to be" has with it - "expectation from a particular model". Which model do mean? Real world climate models that consider all forcings would say that Greenland should be losing mass because northern temperatures are rising and sea warming. I assume you mean fantasy models where you explain climate without the need for GHG and ice-ages can be explained by milankovitch forcings and albedo alone? Well milankovitch forcings are declining which suggests Greenland should be gaining ice (and maybe should have over last 6000 years), but of course that change in forcing is insignificant compared to GHG forcings. For a more realistic view, A. Berger and M. F. Loutre, 2009 argue for a very long inter-glacial.
  11. Dikran Marsupial at 06:56 AM on 17 November 2010
    How significance tests are misused in climate science
    I'm happy to third KRs comment. It is staightforward to show that it is reasonable to talk of the probability that a hypothesis is true. If BP and I were to bet on the number of times a coin I took from my pocket came up heads and I flipped six heads in a row, then BP might well hypothesize that my coin was biased. However, no matter how many times I got a head one after another, he could never know for certain that the hypothesis were true, as (infinitely) long runs of heads are possible, just (infinitely) improbable. But does that mean he is limited to saying "I don't know" when asked if his hypothesis is true? Of course not, most people would have no difficulty in quantifying their belief in the truth of BPs hypothesis. Indeed that is exactly what gamblers do whenever they make a wager, which IIRC is where the Bayesian approach to probability (a mathematical framework for quantifying belief in the truth of an uncertain proposition) originated. BTW - as I belive Donald Rumsfeld (sort of) said - there are things you know, there are things you know you don't know and there are things you don't know you don't know. Statistics of any framework is a good way to deal with the things you know. Bayesian statistics also has a good way of dealing with what you know you don't know - you introduce a minimally informative prior (using techniques like MaxEnt and transformation groups to decide what is minimally informative) representing your ignorance of that element of the analysis and integrate it out (Marginalisation). The things we don't know we don't know, we can't do too much about, other than adopting a cautious approach, avoiding overstatement of our findings and being willing to recognise when we are wrong.
  12. Animals and plants can adapt
    h-j-m wrote: "Reducing CO2 emissions (unless they stem from deforestation) will not help a bit." CO2 emissions are causing global warming, which is causing habit loss for species all over the planet. Thus, reducing CO2 emissions definitely would help, and more than 'a bit'. Also: "Therefore I completely fail to see how rising temperatures may cause general losses in biodiversity." Which is happening faster, climate change or the evolution of new species? That is, unless you think that evolution happens over the course of a few decades, it should be entirely obvious that 'warmer = more biodiversity' is an invalid assumption. Species which cannot adapt to the warmer conditions will become extinct and new species will not evolve at the same rate... ergo declining biodiversity.
  13. The Inconvenient Skeptic at 06:43 AM on 17 November 2010
    Are ice sheet losses overestimated?
    @ Yooper, Where is the source for your data? 0.0 +/- 0.5 °C for the past 10,000 years? Seriously... Vostok, Taylor Dome Not arguing the error of Rohling, but the data shows significant variation, you would have to assume the error ALWAYS went towards no variation to not get a few meters of variation. Also, you avoided my question. What is the mass loss of Greenland supposed to be? I can be specific. What should the mass loss be for Greenland in an interglacial at the current state? Should the mass loss be zero? Should it be increasing or decreasing?
  14. The 2nd law of thermodynamics and the greenhouse effect
    Michele, a similar argument about wave interference was made by another commenter a while ago on another thread. I posted links to explanations and animations that help illustrate the responses by muoncounter and KR. See these comments on that other thread: 206, 207, and 208. See also Riccardo's comment there.
  15. Are ice sheet losses overestimated?
    Re: "The Inconvenient Skeptic" (16)
    "The paleoclimate data does not show long periods of stability, even in the Holocene period and the Holocene is unusual in the duration of the stability. There is still plenty of evidence that the sea levels were 2-3 m higher in the past few thousand years. (Rohling)"
    Your claim about the Holocene not being stable is countered by this: Your claim that your linked Rohling source shows sea levels 2-3 meters higher in the past few thousand years is countered by your linked source, wherein this statement is found:
    "The first two arrays in the attached spreadsheet concern all the compiled raw data. The latter two arrays concern a simple smoothing (3-pt moving average), to reduce sample-to-sample noise. The 1 sigma interval around this 3-pt moving average smoothing is +/- 6.5 m (see Rohling et al., 2009 Nat. Geosci.)."
    How you deduce 2-3 meter higher sea levels from a dataset with +/- 6.5 m accuracy and at best a 500-year resolution is beyond me. Did you not even look at it?
    "It is probable that there were many periods in the past few thousand years that Greenland was losing mass at a greater rate than it is now. Even if the MWP was isolated to Greenland, it would have been losing more ice then."
     Any source for this claim? Conflations with regional/localized events like the MWP belong on a different thread. Please use the search engine in the UL corner of every SkS page to search for a more appropriate thread. Frankly, little in your comment indicates genuine skepticism or acts as a positive contribution to the discussion on this thread. The Yooper
  16. How significance tests are misused in climate science
    BP, I second KR's comment. Relevant also are my responses to Eric (skeptic)'s claim that science has no place for probabilities of the the correctness of theories other than 100% certainty, on the thread The Science Isn't Settled. Start with my most recent comment and work backward by clicking the embedded links to the previous comments.
  17. The 2nd law of thermodynamics and the greenhouse effect
    Michele - I've seen this constructive/destructive interference argument before. However, this kind of interference does not destroy any energy, merely displaces it at most a half-wavelength of the beat frequency. And it only occurs with coherent light and the boundary conditions muoncounter pointed out, neither of which applies in atmospheric IR. Constructive/destructive interference is a red herring. It's simply not relevant to Earth climate energies.
  18. It's the ocean
    h-j-m - Do you perhaps have any evidence that one of your alternative theories is true? You've put forward three different hypotheses, without numbers or supporting evidence - as opposed to the article this thread is based upon. And to quote Christopher Hitchens, assertions without evidence can be dismissed without evidence. As to warmer water leading to evaporation and more warming, well, that's absolutely true, one of the basic positive feedbacks to temperature change. That's well understood basic physics, and doesn't lead to a runaway situation, if that's what you're implying.
  19. The 2nd law of thermodynamics and the greenhouse effect
    #121: "The sum of two counter - propagating waves (of equal amplitude and frequency) creates a standing wave" That's true when there are requisite boundary conditions (such as a pair of reflecting or nonreflecting surfaces). If this is the atmosphere, what boundary conditions are you suggesting?
  20. The 2nd law of thermodynamics and the greenhouse effect
    I would remind something about what occurs when two waves traveling in opposite direction interfere between each other, taking into account the simplest case 1-D. 1- The sum of two counter - propagating waves (of equal amplitude and frequency) creates a standing wave and there isn’t propagation of energy. In other words, using the principle of superposition, the resulting wave may be written as: R = Asin(kx+wt) + Asin(kx-wt) = 2Asin(kx)cos(wt) that is no longer a travelling wave because the position and time dependence have been separated. 2 – If the two waves haven’t equal amplitude, then the global effect is: R = (A + B)sin(kx+wt) + Asin(kx-wt) = 2Asin(kx)cos(wt) + Bsin(kx+wt) that corresponds to a standing wave 2Asin(kx)cos(wt) plus a traveling wave Bsin(kx+wt) which has the propagating sense of (A+B). In other words, the strong wave (A+B) blocks on the way the weak wave (A) and there rests acting only the difference between the two waves. That’s, the traveling effect of counter wave Asin(kx-wt) (for us, the back radiation) vanishes on the way and there’s a reduced traveling effect of stronger wave (A+B). Of course, the energy that don’t travels isn’t destroyed but simply turned into potential energy of the stationary wave. There is nothing strange. In all phenomena of nature only the strongest survive and it always stifles the weaker, that however isn’t suppressed but only captured because Nature always selects for to operate the most elegant and economic way.
  21. It's the ocean
    Claims that the warming of the planet is due to heat being released from the oceans into the atmosphere are not supported by any empirical evidence or peer-reviewed science. Thus ends the article. But if I am not mistaken the temperature of the water is one of the dominant factors determining the rate of evaporation (i. e. the warmer the water the higher the rate of evaporation). But more evaporation equates to more water vapour in the atmosphere (aka latent heat) which will result in warming the atmosphere. Else a lot of physics text books need rewriting. In a previous post I complained about mentioning alternative explanations for rising ocean temperatures. I will give just three with the humble request to be shown how or where these are debunked. 1. Marine as any other life needs energy to build its biomass. By now we are next to successful clearing our oceans of it. In consequence that energy is not used for this purpose and heats the water instead. 2. There may be spots where the earth crust has grown thinner over time and therefore more of the earth's interior heat gets transferred to upper layers. As the earth's crust is thinnest below oceans this may heat the water above. 3. Not only are we clearing out next to all marine life from the oceans we are using them as garbage bins as well. I recall reports stating that all over the oceans probes were taken that revealed a higher content of plastics than phytoplankton. I think it is rather likely that these areas when hit by visible light will absorb more of it and in return emit more infrared radiation aka heat.
  22. The Inconvenient Skeptic at 05:21 AM on 17 November 2010
    Are ice sheet losses overestimated?
    Ok, lets flip this around a little bit. What should the ice loss be? Was the ice loss greater in the late 1940's? What would the ice loss be if there had never been an increase in CO2 emissions? The paleoclimate data does not show long periods of stability, even in the Holocene period and the Holocene is unusual in the duration of the stability. There is still plenty of evidence that the sea levels were 2-3 m higher in the past few thousand years. (Rohling) It is probable that there were many periods in the past few thousand years that Greenland was losing mass at a greater rate than it is now. Even if the MWP was isolated to Greenland, it would have been losing more ice then. Nothing I have seen indicates multi-century stability in glaciers, sea level or temperature. That mankind now has the ability to monitor the tiny changes does not mean that increased CO2 is causing them. John Kehr The Inconvenient Skeptic
  23. How significance tests are misused in climate science
    Berényi - Two comments. (1) You state that weather is in a state of Self Organized Criticality - SOC. I have been unable to find any references that indicate this; do you have a paper to link to on this subject? A statistical analysis of unforced noise in the climate? While water vapor, ice, and condensation are critical point transitions, weather doesn't seem to display the same behavior as a whole. In particular, a pink noise 1/f relationship would indicate the largest variations on low frequencies, where what we observe (glacial cycles, for example) is a fairly direct tracking of climate variables (temperature, ice cover, etc.) to historic forcings. (2) The universe is what it is - that's the final arbitrator of our theories. However, our knowledge is imperfect, and our hypotheses are probablistic, as per the first definition of probability. We can only state that a particular hypothesis is more probable than others given the evidence, the statistics of our data. And whether using Bayesian or frequentist methods, we can estimate from the statistics the probability (second definition) that our hypotheis is supported by that data. That's how induction works, and how we can learn something new. We can be pretty sure, but we can only work with the evidence we have - we don't have perfect knowledge of anything. At a certain point we become certain enough to label a particular hypothesis a fact. Gravity, evolution, and it appears climate change falls into that category as well. But even the strongest "fact" is supported by our inductive conclusion that the laws of physics are consistent over space and time, and won't change on us - incredibly well supported, but the rules could change tomorrow. Crystalline proofs of the type you describe would be nice, but they don't exist.
  24. A detailed look at galactic cosmic rays
    #23: The Harrison and Ambaum 2009 paper you cite is about earth's electric field; it has nothing to do with this topic. The words 'cosmic ray' appear in the abstract, keywords and a non-specific reference to a 1989 paper. The statement in the abstract ... arising from the combination of distant thunderstorms, Earth’s conducting surface, a charged ionosphere and cosmic ray ionization is utterly inconclusive. Neither 'GCR' or 'galactic' appears at all.
  25. Dikran Marsupial at 04:45 AM on 17 November 2010
    How significance tests are misused in climate science
    Maarten Ambaum @ 46 wrote "Also a frequentist would agree with the statement that the p-value does not contain enough information to calculate the probability of the truth of a hypothesis, or the null hypothesis (such statements can be perfectly well framed in frequentist terms)." The first part is certainly true, however the second is not; the frequentist framework does not allow probabilistic statements to be made concerning particular hypotheses. Frequentist statistics can assign probabilities to the ocurrence of errors in repeated application of statistical tests, but that is not the same thing (I checked this with my vastly experienced frequentist colleague and he concurs). If it were true, frequentists could construct a credible interval, rather than a confidence interval by considering the hypothesis that the true value of a statistic lying within a particular interval. But as far as I know, frequentists cannot construct a credible interval - however I'd be very interested to hear otherwise.
  26. Ice-Free Arctic
    #75: "distinguish between BC absorption in the atmosphere and on the ice surface." I'm suggesting that the presence of BC in the Arctic, traced to sources in Europe and Asia, is the key; not where the BC winds up once it is in the Arctic. With BC comes CO, CH4 and CO2 from fossil fuel and biomass burnings. The relative weight of melting due to GHG-induced warming vs. surface BC-induced heat retention isn't the question.
  27. CO2 limits will harm the economy
    Would Cap-and-trade be an effectual way of significantly reducing greenhouse gase emissions? Or do we need a much more aggressive bill to make large differences in greenhouse gas emmisions
  28. Animals and plants can adapt
    The article starts quite factual with stating that biodiversity is under constant thread from direct human interference, Most prominently by destroying (slowly but surely) land for industrial use (food industry) with the latest addition of biological fuels as well as destroying the oceans by depleting them of marine live and using them as trash bins at the same time. In my opinion that needs to be stopped and as far as possible reversed. Reducing CO2 emissions (unless they stem from deforestation) will not help a bit. Besides, if I am not mistaken it is still the tropical rain forests that boast the richest biodiversity which happen to occur where this world counts the highest temperatures. Therefore I completely fail to see how rising temperatures may cause general losses in biodiversity.
  29. Naomi Oreskes' Merchants of Doubt Australian tour
    I wanted to add that in this interview Oreskes is really pithy and bang-on. Clearly she has benefitted from practice honing her responses over time. Soon after the book was published her interviews tended to be a bit more rambling -- now she is sharp as a tack.
  30. Are ice sheet losses overestimated?
    Re: Chris G (12) GRACE measures its altitude above the surface to then deduce mass lost or gained. Isostatic rebound can introduce error into the calculations, so proper adjustments for rebounding of the basement rocks as the ice overburden is removed must be made. There is no "replacement of mass" by the mantle in the mass-portion of the calculations per se...but the rebound adjustment must be done properly for the correct altimetry data to be obtained that can THEN be used in the mass lost/gained calculations. Hope that's more clear. The Yooper
  31. Are ice sheet losses overestimated?
    Agnostic (#8), IDK, but IMHO... Rising sea levels will result in property loss and in some areas mass migrations, and this will take place over many decades to centuries. In contrast, shifts in temperature and rainfall patterns, and ocean acidification will affect, and almost certainly in a negative way, where, and how much, food can be grown. The latter changes are taking place now and can change in just a few decades, or even less if a tipping point is reached; personally, I see the latter as a larger threat. I should probably defer any follow-up to the topic of climate change costs.
  32. Naomi Oreskes' Merchants of Doubt Australian tour
    @ John Harrington #32 Some personal perspective... There is an old truism that holds that academic debates can get as vitriolic as they do precisely because there is so LITTLE at stake. I can imagine that in certain corners of certain fields there can be a bit of bullying primarily because the outcome concerns very few people and bullying pays. The same scenario is possible in any walk of life with similar paramters(although it doesn't really occur often if you think about it). That said, in my 25 years in science I have never seen anything on the scale you describe. I have certainly seen personal biases and conflicting personalities play a role in scientific exchanges (some much more unjustifiably aggressive than evident in those darn climategate emails) - but in the end it is the intellectual/empirical side that eventually holds the field in those exchanges. That's what matters. That result is possible because in my science, as in climate science, it is impossible for one person to gain much control over opinion precisely because there are a reasonable number of peers working in the field. Scientists hate despots more than most people -- scientists are usually fierce individualists, and the abuse of power conflicts with the free flow of scientific ideas. I also know that if I work on a problem or an approach that is outside the mainstream, I have to work a bit harder to gain acceptance. I don't complain about it -- that is as it should be given that scientists should be critical. But, in the few times I have followed that less trodden path in the past, I have never once felt that I have been blackballed or censored for my positions. Not once. It is very hard to get any consensus in science on anything without overwhelming evidence in one direction or the other. Those who claim that there is some conspiracy among scientists regarding AGW (by which I mean CO2 effects on climate) have no clue how the process works or how fiercely independent scientists are in general (or they depend on others not knowing).
  33. Are ice sheet losses overestimated?
    Oh, maybe it is the case that previous studies have larger estimates for isostatic rebound than Wu, et al, 2010.
  34. Are ice sheet losses overestimated?
    I'm having a problem at the conceptual level with all this; maybe someone can help. Let's say you assume no isostatic rebound and you measure a certain loss of ice mass, I, using GRACE. Under this assumption, Total loss = I. If the mantle is rebounding, some of the ice mass lost is being replaced by mantle mass; let's call the mantle mass M. Under this assumption, T = I - M. That is, the total measured mass loss is whatever is lost in ice, minus whatever has been replaced by rock. If the mantle mass rebounded perfectly with the ice mass lost, there would be zero measured mass lost. Changing the formula around trivially, you can say, I = T+M. The data regarding mass loss from GRACE (T) hasn't changed; so, I don't yet understand how introducing a rebound effect can reduce the estimate of how much ice has been lost.
  35. How significance tests are misused in climate science
    In Schmidt and Manns response to Mcshane and Wyner, Schmidt and Mann calculate a 99% probability of the last decade being the warmest in the record using the Lasso stastical technique from MW. They then discount that probability to likely (66-90%) claiming unidentified measurement uncertainty and possible systematic errors (page 3). When they discount their statistics that much, does the difference between Bayesian and Frequentist really amount to anything? If climate scientists use frequentist statistics and then discount the result to account for unknown errors they will still have conservative estimates of the actual effects.
  36. Naomi Oreskes' Merchants of Doubt Australian tour
    @David Horton, I had meant to make clear, but apparently didn't, that the conversation happened in the course of discussing global warming. No, I certainly don't intend to imply that that's what is happening with global warming science. That was her implication, not mine. I'm not a denialist of any kind. I accept the science, and always have. I came here because, as I said, I wanted to hear from practicing scientists who could offer their experience to counter the claims of my scientist-manque acquaintance. I wanted this because a friend was present who was taken in by her description of "modern science" and I'd like to offer him another perspective.
  37. Berényi Péter at 01:59 AM on 17 November 2010
    How significance tests are misused in climate science
    Maarten, statistics is never used in natural sciences in a way you put it. That is, it simply does not make sense to talk about the probability of hypotheses being true (or false). It's either true or false. Of course it is entirely possible we are ignorant about its truth value; in that case one should say I do not know (a perfectly legitimate scientific stance), but it surely has a truth value, even if no one was able to determine it so far (provided of course the hypothesis makes sense in the first place). The Bayesian method you describe could only serve as a heuristic device, but only if we had clear (quantifiable!) picture of prior probabilities regarding our own ignorance. That's almost never the case. If we knew how ignorant we were (having a reliable structural model of our own ignorance), most of the job required to overcome this ignorance would already be completed. However, when heuristics is most needed, we are at the edge of utter darkness, just feeling our way around, not even equipped to make educated guesses about Bayesian priors of our own state of mind regarding the subject matter. In cases like that almost any fractional understanding is better than fake formal methods to arrive at a reasonable conclusion regarding the way forward. It may be different for decision makers (like politicians or business people) who rely on expert advice in certain matters, but are not equipped to actually understand and evaluate the detailed reasoning behind those expert opinions (they only digest the executive summary, anyway). They may well wonder how likely it is the experts have got it right, and in complicated cases it makes perfect sense for them to seek a quantified description of uncertainty. To ask an independent group of experts to give an estimate of prior probabilities and build a Bayesian model to evaluate reliability of expert propositions may be a way forward. However, in practice extra rounds like that are seldom better than honest expert meta-opinion, expressed in plain language. There is a more restricted domain where statistics can (and do) come into play in natural sciences. That's measurement laden with noise. However, in this case there is no room for theoretical ambiguity. We should know pretty much everything how the signal we are looking for is supposed to look like along with the statistical properties of noise behind which it is hiding. This knowledge should take the form of a bunch of true propositions about the phenomenon under scrutiny, neither of which has a dubious truth value expressible in a probabilistic form. If this knowledge is given, we should be able to build an adequate statistical model which enables us to recover the signal from noise as much as possible. Of course the first thing to do is not to rely on statistical speculations, but to improve the signal to noise ratio of measurement whenever it is practicable. Unfortunately in climate studies most of the noise is not from the measurement procedure itself, but it is weather noise, that is, an inherent property of the system itself. There is no way to get rid of it during the measurement phase. Weather is an open thermodynamic system, and as such it works on the edge of chaos, in other words it is always in critical state (by way of SOC - Self Organized Criticality). Systems like this are characterized by system variables with pink noise characteristics (the noise has random phase and the same power in each octave). Pink noise is scale invariant with no lower cutoff frequency, therefore system variables like this do not make a natural distinction between weather and climate, no matter how long is the averaging window used (how low the upper cutoff). Pink noise is never stationary, it has an arbitrarily long autocorrelation scale. This is why it is a bit tricky to look for trend (as signal) in a climate variable laden with weather noise. A simple model of a linear trend plus some stationary noise would surely not do (even if mainstream climate science is almost always guilty of using such simplistic models). Pink noise can have spontaneous excursions on all scales, including extremely low frequency ones (well in the supposed climate range of 30+ years). You say "A standard answer [to the question if temperatures are rising or not] is to calculate a temperature trend from data and then ask whether this temperature trend is “significantly” upward; many scientists would then use a so-called significance test to answer this question. But it turns out that this is precisely the wrong thing to do." Yes, but it is not wrong just because the result of an otherwise correctly applied significance test is misused, but in most cases people also apply the wrong significance test (that fails to take into account the very long autocorrelation timescale). The above statements on weather (or climate) noise, critical state, self-organized criticality, pink noise, etc. are simply true statements with no further qualification whatsoever. It is not likely they are true, not even 100% sure, they are simply adequate descriptions of certain aspects of the behavior of open thermodynamic systems with many degrees of freedom. Still, they are entirely missing from IPCC reports, prepared by experts for decision makers. Phrases like "pink noise" (or "1/f noise") are not even mentioned under http://ipcc.ch. Funny.
  38. A detailed look at galactic cosmic rays
    On the issue of GCR Cloud Seeding You seem to have completely ignored the body of work by Harrison and others who have made in situ cloud observations which "are consistent with enhanced production of large cloud droplets from charging at layer cloud edges." There's an example of their work below but also many more from what I can see in literature searches. Harrison and Maarten 2009
  39. Naomi Oreskes' Merchants of Doubt Australian tour
    @John Harrington #32 (BTW I am not a practicing scientist, I am an engineer and speaking from my point of view) In view of all technological progress made in the last centuries, I would say in general the scientific process seems to work pretty well. If we only look back 100 years, we can see how much our world has changed thanks to the new insights developed by the scientific community. This is not so much due to individual scientists – although of course talented scientists can have a big impact – but it is mainly due to the scientific process, that validates, connects and consolidates knowledge. Many things we take for granted nowadays wouldn’t be around without this scientific process. For instance: cars, airplanes, spaceships, television, cell phones, computers, robots, all sorts of electronics, medicines, operating equipment, power plants, … Non-scientists generally don’t have a clue as to what tremendous combined effort in various disciplines has been necessary to develop these products. I am thinking of materials science, crystallography, astronomy, mechanics, electronics, information theory, electromagnetism, quantum mechanics, thermodynamics, chemistry, biochemistry, chaos theory, etc. If it were true that "science is about dominant factions of science bullying those who disagree" you would never see this kind of progress. Actually, you would see no progress at all. I rest my case.
  40. How significance tests are misused in climate science
    Thanks for the insights Maarten. I searched your work on Web of Science. It looks like you'd have heaps to contribute if you felt so inclined. The cloud ionisation work with Harrison caught my eye. The most recent article on SkepticalScience about GCRs seems to have neglected the insights from Harrison's work. (Apologies for going OT)
  41. Are ice sheet losses overestimated?
    Cryosat-2 *should* be able to help very much although it will still have its downfalls like the other methods. Ultimately what you will see is that Cryosat-2 data will be probably the most important dataset in the future for ice sheet change detection. That being said, I could never see radar interferometry not being useful as it is the only method that can actually detect and measure when flow increases from outlet glaciers. The problem with radar interferometry though is that you can measure the outputs, but knowing the thickness of glaciers and how much snow comes in, is more difficult. All in all, cryosat-2 is going to be a great tool but there will probably be hiccups initially.
  42. Are ice sheet losses overestimated?
    Re: oamoe (9) Yes. Cryosat-2's primary mission:
    "ESA’s Earth Explorer CryoSat mission, launched on 8 April 2010, is dedicated to precise monitoring of the changes in the thickness of marine ice floating in the polar oceans and variations in the thickness of the vast ice sheets that overlie Greenland and Antarctica."
     The calibration phase should be complete and full-service data collection begun. The Yooper
  43. Are ice sheet losses overestimated?
    Will Cryosat be able to clarify this situation?
  44. Climate cherry pickers: cooling oceans
    "What we do know, and have measured, are not absolute TSI's and forcings, but rather time-resolved points of deltas in forcings; when they have changed to some extent." Even our knowledge of TSI has been based on significant and invalid assumption. Haigh et al. using the new SIM data show that where we thought a decrease in "TSI" should mean decreased radiation reaching the surface, the makeup of the TSI matters and is non-intuitive and not previously measured. This new knowledge could have significant ramifications to climate science.
  45. Climate cherry pickers: cooling oceans
    KR #35 & kdkd #36 Had a look at the ACRIM and PMOD satellite TSI series. It is a somewhat confused picture with ACRIM Composite being written up as the best of the ACRIM 1,2,3 satellite reconstructions compared with PMOD which is somehow model based. Even then ACRIM produced a positive trend over the last 30 years equal to about +0.1W/sq.m (0.04%)solar radiation at the surface, whereas PMOD seems a negative or no trend. My main point was that none of these reconstruction uses SORCE TIMS or can explain the -4.5W/sq.m absolute difference in TSI. In fact the SORCE people produced their own Earth's energy flux balance chart (a la Dr Trenberth's famous chart) based on a TSI of 1361.5 W/sq.m rather than 1366 W/sq.m. Apparently it was crap according to a leading climate scientist. Your point about differences and deltas being the important determinant of trends is correct, provided we know what is happening at start time T1 with the particular forcing we are examining. Overriding this is BP's point that when you look at the satellite TOA imbalance data for the 2002-04 period there is no significant delta at all, see here: http://www.skepticalscience.com/news.php?p=2&t=107&&n=178#12580 when OHC content charts quoted above show a big leap. That is why high precision (month-month or year-year with same instrument) but low accuracy satellite data must be looked on as much more reliable than transitional XBT-Argo data measuring OHC. kdkd makes an interesting point. Clearly we have to try and pick winners here. Sort which data is crap and which might be close to correct. When there is conflicting data - the method is to look at its nature and try to find logical reasons why one might be good enough to be useful and the other not so. Satellite deltas verses XBT to Argo transition is a no brainer I would have thought.
  46. Naomi Oreskes' Merchants of Doubt Australian tour
    The message of the book is that these people that do things for their (weird) ideological reasons. These people are good enough for the special interests. In fact, any denier voice is good enough for the special interests. The special interests are not in for the science. They just want to keep polluting and getting away with it.
  47. Climate cherry pickers: cooling oceans
    KL #34 You can't have your cake and eat it you know. Making (correct) claims that particular measurements are too imprecise to be terribly useful is one thing. Following on from that your argument then assumes that these measurements have a very high degree of precision (or at least we can ignore the uncertainty). This by itself invalidates your argument. There may be a useful contribution you can make here, but at present it appears to be through (like BP) being a useful case study of the faulty reasoning of so-called climate sceptics.
  48. How significance tests are misused in climate science
    Dear Eric L., In my opinion you are making too much of the frequentist vs Bayesian discussion. I think it is not that central to whether you think significance tests are useful or not. Also a frequentist would agree with the statement that the p-value does not contain enough information to calculate the probability of the truth of a hypothesis, or the null hypothesis (such statements can be perfectly well framed in frequentist terms). Regarding the dendrochronologist, this is an example that is very interesting. Equation 6 in my paper states how to view this. It is simply Bayes equation written in terms of prior and posterior odds: posterior odds = prior odds x p(M| not N) / p(M|N) where I used the notation as in the post above (note the p(M|N) is the p-value). So whether your confidence in the global warming hypothesis has been increased by your tree work depends on whether the p-value is smaller than the probability to see your measurement in situations that we know there is global warming. This statement is independent of the prior odds; the actual posterior odds of course do depend on the prior odds. In other words, every single measurement increases our knowledge (changes our confidence in a hypothesis) in the same way; this is independent of whether you were a "believer" or not to start with. This discussion is getting quite long now. I will probably write another post with some of this stuff in sometime soon where I can also comment on the suggestion by HumanityRules. I think John Cook agreed that I could send in another guest post about this subject anyway. Best wishes to all and thank you very much for your interest in this post and for an interesting discussion, Maarten Ambaum
  49. Ice-Free Arctic
    muoncounter you should distinguish between BC absorption in the atmosphere and on the ice surface. I was referring to the latter which directly influences the ice melting.
  50. Naomi Oreskes' Merchants of Doubt Australian tour
    Oh and John Harrington at #32 - why, I wonder, would you repeat an anonymous anecdote like that, and, what's more, to use it as an example of "how science works" in general? It couldn't be, could it, that you are intending the reader to say "Oo yes, that must be what is happening with global warming, all the honest skeptics are being bullied, so the truth can't come out." That wouldn't be the intention would it John? I have been a scientist for over 40 years - the scenario you suggest is nonsense.

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