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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 123901 to 123950:

  1. Is CO2 a pollutant?
    Bob Armstrong, on the issue of how long CO2 levels remain elevated (your other points having been addressed by carrot eater)... you should consider the ice core record. You dismiss estimates of centuries as ridiculous, but in fact every time there has been a CO2 increase of ~100 ppm (which is about where we are over the pre industrial revolution level) in the ice core records it has taken place over a period of a few thousand years... and then required ~100,000 years to return back down to the previous level. Mere centuries are thus a very 'hopeful' estimate when compared to every past instance for which we have data. It is unfortunate that you are so certain of the validity of your errors. Had you shown a more open mind you might have learned something.
  2. The Dunning-Kruger effect and the climate debate
    HumanityRules at 19:54 PM on 16 February, 2010 Helps to remember that over the long term climate variability one way or another imposed by solar fluctuation will dither widely while more or less exhibiting no net long term change (unless we go forward millions of years). On the other other, what we know of the behavior of C02 when it is illuminated by IR tells us it will impose a steady net increase in the amount of heat energy retained within our atmospheric envelope. I think it's easy to overlook this important difference between one driver of variability (or net variation) and another. what we know now tells us that given a few decades, added C02 in sufficient quantities will always win over solar forcing as a driver of climate change. Also, having noticed a common error creeping into this thread, I'm going to be redundant yet again (r2) and point out that we devote fanatical amounts of engineering expertise to controlling anthropogenic emissions of substances also found as natural constituents of the atmosphere. C0 is a prime example. So it's a fallacy to say that C02 in excessive amounts is not a pollutant. A quick check of the dictionary will help with this.
  3. Did Phil Jones really say global warming ended in 1995?
    suibhne @44 I think I'm right in saying that the CRU have pointed out that they do not generate any original data (records)-- that is, they don't go off to the South Pole, or wherever, to gather readings -- so if Jones said he is not very good at keeping records, it doesn't necessarily mean that he's lost original data, or not know where the original data exists. As I said -- in effect -- earlier, he's a dolphin that's found himself in a pool of sharks. He might be more intelligent and knowledgeable than they are, but his teeth are seriously inadequate.
  4. Is CO2 a pollutant?
    Bob Armstrong: Please review more carefully what Kirchhoff's law actually requires. It should be in any decent physics book. It does not require materials to be grey bodies, which is good because we can clearly see that they are not. Things do have different colors, after all. It only requires that the absorptivity and emissivity be equal to each other at a given wavelength. It does not require either quantity to be constant over wavelength. You can see this emipirically. Look up the emissivity of snow. In the wavelength range where snow might emit (long IR), the emissivity is close to 1. But of course snow is a poor absorber of visible light. Wavelength matters.
  5. Did Phil Jones really say global warming ended in 1995?
    But suibhne, the 2008 paper affirmed the conclusions of the 1990 paper, while lacking the possible flaws of the 1990 paper.
  6. Is CO2 a pollutant?
    suibhne: It isn't a matter of a time delay. The issues are that CO2 radiates back towards the Earth (the surface sees more radiation than it used to), and that the emission that finally makes it out to space is emitted from higher up in the atmosphere, where it is colder (less radiation is leaving the earth system than is arriving, so the system has to warm up). With nitrogen, you get none of that. By the way, CO2 doesn't always instantly radiate a photon as soon as it absorbs one. It can collide with neighboring molecules and thus warm up that pocket of air. But that's still fine; the CO2 will still emit at some rate set by the local temperature. These sorts of things are easily learned about in a textbook that covers radiation transfer in the atmosphere. I suggest simply getting one.
  7. Did Phil Jones really say global warming ended in 1995?
    angusmac @47, see the comments policy for how to post figures. Hopefully you can relate your graph to the discussion.
  8. Did Phil Jones really say global warming ended in 1995?
    Phil Jones may rewrite part of 1990 report. Nature online 16/2/2010
  9. Did Phil Jones really say global warming ended in 1995?
    oracle2world: Is it accurate? 'There has been no warming since 1995' is a very different statement from 'there has been no statistically significant warming since 1995'. In Jones' set there is a warming trend, and every year after 2001 has been warmer than 1995. There has been warming. It is not statistically significant because a certain combination of known noise could recreate that trend in 5%+ of cases. Of course, if you think my stats understanding is wrong, point me to where I can read up and fix it.
  10. Did Phil Jones really say global warming ended in 1995?
    Tom Dayton I Hope that you understand why I remain sceptical about the disputed Chinese readings. No doubt the issue will be examined by each of the two inquiries.
  11. Is CO2 a pollutant?
    Tom Dayton I was in part answering post 119, who if correct with instantaneous absorption and emission of IR, would imply almost that nothing had happened and since IR moves at 3*10^8m/s, then any delay is negligible. Water vapour is still in the atmosphere(in much greater quantities) and is an even better IR absorber. Further conduction from Earth surface by all atmospheric gases plus convection including wind will distribute and even out the Earths surface temperature
  12. Did Phil Jones really say global warming ended in 1995?
    Is it possible to post a chart on this site? I have an intersting graph based on current GISS data and a paper by Hansen et al, 2006, which I would like to post. This shows that we are currently tracking below the zero-emissions trajectory for global warming.
  13. Jeff Freymueller at 03:15 AM on 17 February 2010
    Did Phil Jones really say global warming ended in 1995?
    #41, oracle2world. Just one question. First, read post #21. If the warming trend from 1995-2009 is not staistically significant, but the trend from 1994-2009 IS statistically significant, as is the trend from any year prior to 1995 through 2009, what do you think the headline should be? #43, John Russell, I got a similar impression of Jones from the transcript. He was spin-free. Certainly it would have been better for him to have said, "the trend from 1995-2009 is not significant, but the trend from X-2009 is. The reason for the difference is that 1995-2009 is too short a time span." But we were not the ones sitting there in front of the TV cameras -- it's easy to second-guess.
  14. Polar bear numbers are increasing
    jasonblanchard, at least one species of seal is indeed at risk. But, controversially, the U.S. recently denied a request to list them as endangered.
  15. Increasing CO2 has little to no effect
    Matt, the implication of what Stuart just explained in his next-to-last paragraph is that the energy coming from the Sun to the Earth is in the wrong wavelengths to be much absorbed by CO2, but the energy being emitted by the Earth is very much in the right wavelengths to be absorbed by CO2.
  16. Did Phil Jones really say global warming ended in 1995?
    suibhne, regarding the "disputed Chinese readings," Phil Jones and colleagues have posted a response.
  17. Polar bear numbers are increasing
    "No sea ice means no seals which means no polar bears." No seals? Where's the outcry for that? Where's their endangered status? I guess they're not as cute as polar bears.
  18. Did Phil Jones really say global warming ended in 1995?
    Surely one of the most alarming part of the interview was when he(Phil Jones) indicated that he is not very good at keeping records. If one of my students said he had collected some temperature readings but the location of the the readings was uncertain then I would have to disregard them. It should now be obvious that the disputed Chinese readings have to be disregarded.
  19. Is CO2 a pollutant?
    suibhne, replacing all CO2 with N2 would result in much less slowing of the Earth's energy loss to space, because N2 is not a greenhouse gas. Technical explanations are easy to find, but here is a concise one from Wikipedia:
    Although contributing to many other physical and chemical reactions, the major atmospheric constituents, nitrogen (N2), oxygen (O2), and argon (Ar), are not greenhouse gases. This is because molecules containing two atoms of the same element such as N2 and O2 and monatomic molecules such as Ar have no net change in their dipole moment when they vibrate and hence are almost totally unaffected by infrared light.
  20. Increasing CO2 has little to no effect
    Matt, I think I see where your mistaken understanding is coming from. I think you're calculating the spectral radiance from Planck's law (if not, please explain where you get your figure of 180). I get about 150 by my calculations, but that's close enough to demonstrate the problem. The thing is that spectral radiance has a rather complicated definition: energy per unit time per unit surface area per unit solid angle per unit frequency The surface area of the sun is different to the earth - it's about 12000 times greater. 150 times 12000 is actually about 1.8 million. Hence the sun produces about 1.8 million times as much energy at 15 microns. It's hotter and larger, so this shouldn't come as a great surprise. But consider the fact that the sun is radiating this energy out in all directions, and that the earth captures only a tiny proportion of that energy because of our small size. Even Jupiter only appears as a tiny dot in the sky without a telescope. We can work out exactly how much we capture by dividing the area of a circle the size of the earth by the surface area of a sphere at the radius of the earth's orbit: pi*(6400^2)/(4*pi*(150 million)^2) = 0.00000000046 Taking this, and the 1.8 million value found before into account, the earth would (in the absence of atmospheric absorption) radiate out about 1200 times as much energy at 15 microns as we receive from the sun. This isnt true. Visible energy is let in, not heat. The heat of the sun is bloocked by the same GH gasses as block the heat going out. Visible energy IS heat. The heat we get from the sun is mostly within the visible and the near infrared, because the sun is hot and has a blackbody curve centred in the visible. When we absorb it, we radiate it back into space according to a much cooler blackbody spectrum, deeper into the infrared. This is all fairly basic greenhouse theory, and I don't think you've quite grasped the science behind it.
  21. Did Phil Jones really say global warming ended in 1995?
    Oracle2world @41 What you're confirming is that Phil Jones is a straightforward, uncomplicated (and perhaps politically-naive) scientist, rather than a politician with a lawyer's brain. Given that it's agreed by the vast majority of scientists that the world has been on a warming trend since temperature recording began, would it not be totally illogical for Phil Jones to mean, "there has been no warming since 1995"? Clearly, if he thought like a politician, he should NOT have said, 'Yes'; but should have said something like, "It has not been possible to separate a trend from the noise over that period". Surely logic suggests that we must assume that the long term trend continues, given that the noise over the last fifteen years has obscured any statistically-meaningful variation from that temperature trend, either higher or lower?
  22. Is CO2 a pollutant?
    CBDunkerso ...........As to your convection hypothesis... it fails because, amongst other things, greenhouse gases do not retain heat within themselves. They absorb and then immediately re-emit the infrared radiation..... Well surely if the IR radiation is immediately randomly re radiated and all this happens at the speed of light then the time delay introduced by CO2 in a 17Km troposphere would be completely negligible. A thought experiment If co2 were completely absent from the atmosphere and instead we had extra N2 to take their place what THERMAL CHANGE would this produce. (Ignore chemical and biological change for the moment] I have the feeling that the atmosphere would remain much the same.
  23. Arkadiusz Semczyszak at 01:39 AM on 17 February 2010
    Did Phil Jones really say global warming ended in 1995?
    Marcus "One final point, though not statistically significant, temperatures rose by 0.012 degrees per year between 2000 & 2009, yet average sunspot numbers fell by around 14.5 per year." O.K. Cyclical changes in solar activity do not (simple) coincide with the cycle of the Millennium. Agreed. But now we have a typical growth phase temperature in the Millennium cycles in a typical (for him) periods. It was not me saying that this cycle in some way depends on solar activity, and Rahmstorf. In many, many works and commentaries.
  24. Did Phil Jones really say global warming ended in 1995?
    Insofar as you can fit something into a headline, the text "there has been no global warming since 1995" is accurate. Now you can delve into the weeds about significance levels, time periods, datasets, overall trends, caveats, blah, blah, blah ... but the text speaks for itself: BBC: Do you agree that from 1995 to the present there has been no statistically-significant global warming Phil Jones: Yes Now if you want to start adding caveats to ALL global warming headlines ... that would be fine. Like the IPCC in its 2007 report said: "Eleven of the last 12 years rank among the 12 hottest years on record (since 1850, when sufficient worldwide temperature measurements began)." That last parenthetical statement seems to go by the wayside a lot. And maybe a mention of the Medieval Warm Period, and the Holocene maximum would be helpful. And satellite temps versus ground records that omit quite a bit of the earth's surface. Somehow the IPCC infactuation with 12 years of data was important and significant ... but the same years found to be not statistically significant don't really mean much of anything now. Any questions?
  25. The Dunning-Kruger effect and the climate debate
    Oracle2world, your citation of CO2 levels in greenhouses doesn't meet your own criteria for determining whether something is a pollutant or not. To quote, "any substance in excess that is a danger to human health and the natural environment is a pollutant". Greenhouses are demonstrably not the "natural environment". Observed shifts in pH from CO2 increases thus far indicate that humans raising atmospheric CO2 to 1000 ppm would be catastrophic for the oceans of the world... even without the effects of global warming. Ergo, yes... by your own definition CO2 IS a pollutant. As to there being no anomalies in AGW data... there have been plenty. Most (e.g. early UAH satellite temperature series or the first pass of ARGOS buoy ocean heat data) have been due to errors which were later corrected. However, there are some still outstanding... such as calculations of the factors contributing to sea level rise not adding up to the total observed increase. Likewise there is ongoing debate as to the causes of tree ring divergence over the past fifty years and fluctuations in the temperature record (such as the current period of decreased warming). That's not even getting into all the issues around proxies and climate sensitivity... particularly the complexities around clouds having multiple positive AND negative feedback impacts.
  26. Did Phil Jones really say global warming ended in 1995?
    Oops, forgot to include the link. http://sciences.blogs.liberation.fr/files/dix-ans-de-froid-dans-un-si%C3%A8cle-chaud.pdf
  27. Did Phil Jones really say global warming ended in 1995?
    Here's the full text of the Easterling/Wehner paper cited by DIkran Marsupial@24 for JonMoseley@3. DIkran's description:
    "Furthermore, the observed results are in conflict with the predictions of the computer models. Therefore, the computer models are wrong." Actually that is not correct either, see the paper by Easterling and Wehner, which shows that the internal variability of the climate means that there will be occasional decadal trends showing no warming or even cooling, and that these are seen in the output of the models.
  28. The Dunning-Kruger effect and the climate debate
    It would be really good news if people with little scientific training "conformed" to science, scientific consesus and peer review ...
  29. Did Phil Jones really say global warming ended in 1995?
    Regarding the amount of time needed to detect the warming signal against the noise: The statistician Tamino addressed that explicitly in his post How Long?. (That's the same post that Steve L linked to earlier.)
  30. Did Phil Jones really say global warming ended in 1995?
    John/40 Shades, without doing the full statistical analysis we can still use past variability as a general guide. For instance, there was a 30 year 'pause' of mild cooling in the warming trend from ~1940-1970. Thus, the current 15 year period of only mild warming doesn't seem particularly anomalous. For me, it'd have to run more than 30 years (say 40) without warming passing 95% certainty to 'give pause'. That hasn't happened before in the instrumental record so it would indicate something 'new'. Anything shorter than that is just consistent with past variations.
  31. Did Phil Jones really say global warming ended in 1995?
    Ricardo @31 I think you missed the point of '40 Shades of Green's' question. He's (she's?)asking if someone with the required knowledge has done the statistical analysis on the actual data, and what the result was? A fair question I would say. As a lay response I would say there's no magic level of data that must reveal a trend hidden in noise. Imagine looking at a newspaper photograph at a high level of magnification under a microscope: with a few dozen dots (data) visible you wouldn't have a clue what the picture was about. Now reduce the magnification. At a certain point -- and number of dots (data) -- one can start to make out the image and have a stab at what's being revealed. The lower the magnification, the more dots (data) and the more certain you can be of what you're looking at. I hope that helps.
  32. Did Phil Jones really say global warming ended in 1995?
    I just noticed something odd about the OHC chart. A frequently raised topic in AGW discussions is 'natural variability', particularly as it relates to cycles of oceanic heat transfer. The 'pacific decadal oscillation' (PDO) seems to be a particular favorite. Basically, the theory is that cyclical circulation of colder deep ocean water and warmer surface waters has a strong impact on climate. So, if the PDO, as one of the larger cycles observed, is pushing alot of cold water to the surface that is going to have a cooling effect on the atmosphere. Such is often used to explain cooling trends from 1880-1910 and 1940-1970. Then the cycle reverses and ocean heat is transferred to the atmosphere, causing warming. However, looking at the OHC graph it seems like there was a drop from 1960-1970... the same time the ocean was supposedly 'sucking up heat' from the atmosphere. Then from 1970-2000, when the ocean was supposed to be releasing heat into the atmosphere, OHC went through the roof. Does this disprove oceanic heat transfer as a major driver of climate? I suppose greenhouse warming could have overwhelmed ocean cooling from 1970-2000, but why did ocean heat decline from 1960-1970? Was there a solar decline in that timeframe which would explain both the atmospheric and oceanic heat declines?
  33. Did Phil Jones really say global warming ended in 1995?
    Sorry, Arkadiusz Semczyszak, but your claims are not borne out by the numbers. Consider the last 90 years, in 30 year increments: 1920-1949, 1950-1979 & 1980-2009. For 1920-1949, average monthly sunspot numbers increased by around 2.5 per year, & temperatures rose at an average of 0.0095 degrees per year during that time. For 1950-1979, average monthly sunspot numbers decreased at a rate of 0.5 per year (which is almost nothing at all), and temperatures rose at around 0.0016 degrees per year (which is also almost nothing at all). For 1980-2009, sunspot numbers declined an average of 2.7 per year, yet temperatures during that period rose by 0.016 degrees per year. So we are in fact seeing the fastest 30-year rise in global temperatures, this century, at a time when we're also seeing the most rapid 30-year decline in sunspot numbers this century. I can't see how that fits with an "its the sun" theory. One final point, though not statistically significant, temperatures rose by 0.012 degrees per year between 2000 & 2009, yet average sunspot numbers fell by around 14.5 per year.
  34. The Dunning-Kruger effect and the climate debate
    JonMoseley @ 69 You ask: 'Is the Earth's plant life capable of absorbing more CO2 than it currently does? Has the Earth's plant life reached a maximum cap, beyond which it cannot absorb any more CO2?' Well, as we know that atmospheric CO2 is rising and has been rising since the Industrial Revolution, it would seem that the answer is yes! And we know that the ocean has been absorbing around 50% of the carbon emitted. Rising temperatures aren't going to make things any easier either. There are a number of temperature-sensitive carbon sinks that are expected to to become carbon sources as temperatures increase. You also state: 'Just as increasing sugar as food to a culture will stimulate growth, it is reckless to ignore the effect of the Earth's plant life reacting dynamically to an increased presence of CO2.' Yes this is true, but as ideas go it is half-baked. Can you point to CO2 starvation ever being a growth limiting factor in the open air? [Citations from reputable journals only, please.] Now I can fully guarantee that this is only a partially-baked answer, but what do you expect in a blog post? The over simplistic relationship between plants and CO2 is often raised as one of those: 'CO2 isn't universally bad, it will result in more plant growth' arguments [so beloved of the Denial Industry, who just seek to confuse the public], but this is an area which has revealed a number of genuine surprises. Free Air CO2 Enrichment studies reveal that the effects of enclosures that were used in many previous studies typically overwhelmed the CO2 enrichment effect. Now I realise that this isn't the same as what you were aiming at, but it reveals that studies that suggested CO2 led to increased plant growth need to be reassessed since their findings may be an artifact of the test method. There are an increasing number of studies that show unforeseen effects of increase CO2 levels: Growth and nutritive value of cassava (Manihot esculenta Cranz.) are reduced when grown in elevated CO2 RoslynM.Gleadow 1, John R. Evans2, Stephanie McCaffery2 & Timothy R. Cavagnaro2,3 Plant Biology ISSN 1435-8603http://www.biolsci.monash.edu.au/staff/gleadow/docs/gleadow-2009-cassava-online.pdf Changes in Nutritional Value of Cyanogenic Trifolium repens Grown at Elevated Atmospheric CO2 RoslynM.Gleadow & Everard J.Edwards & John R. Evans J Chem Ecol (2009) 35:476–478 DOI 10.1007/s10886-009-9617-5http://www.biolsci.monash.edu.au/staff/gleadow/docs/2009-clover-cg-co2.pdf Food for Thought: Lower-Than Expected Crop Yield Stimulation with Rising CO2 Concentrations http://www.bnl.gov/face/pdfs/Long_2006.pdf "Climate Change Surprise: High Carbon Dioxide Levels Can Retard Plant Growth, Study Reveals ScienceDaily (Dec. 6, 2002) http://www.sciencedaily.com/releases/2002/12/021206075233.htm Nine further studies here: http://www.logicalscience.com/skeptic_arguments/CO2-fertilization.html Therefore the answer to: 'Just as increasing sugar as food to a culture will stimulate growth, it is reckless to ignore the effect of the Earth's plant life reacting dynamically to an increased presence of CO2.' is: It is reasonable to expect wild plants to respond in a variety of different ways, and not necessarily in a manner beneficial to human society or the ecosystems where the plants belong. Yes it is reckless to expect the biosphere to respond in a manner that will reduce our obligation to cease our destructive behaviour. Yes increasing atmospheric CO2 will affect ecosystems, but their response cannot easily be predicted and surprises are likely. Yes we should be cautious about large scale tampering with the energy budget of the earth, it may not be beneficial to us, the climate or other life on Earth.
  35. Did Phil Jones really say global warming ended in 1995?
    40 Shades of Green, there's no a priori time span. You need to perform statistical analysis on the actual data and determine it. Here's a draft of Von Shuckman et al. 2009..
  36. Did Phil Jones really say global warming ended in 1995?
    To revert to my analogy posted under another topic. It's like watching the last 14 waves that came in on the beach and trying to work out whether the tide is coming in or out. The variation in height of the last 14 waves does not give one enough information to produce a statistically significant trend (even less so the last 8 waves). The noise (waves) hides the trend (tide). After ten minutes and a hundred waves the direction of the tide becomes very apparent. I wonder why Phil Jones didn't think to use such a clear analogy? The lay audience would have got it in one and those with a basic scientific understanding would/could not have questioned the way he expressed himself.
  37. 40 Shades of Green at 20:37 PM on 16 February 2010
    Did Phil Jones really say global warming ended in 1995?
    To my mind the key question is this. If 15 years without statistically significant warming is not enough to give one pause, then how many years would be required. 20, 25, 30, 50, 100?
  38. 40 Shades of Green at 20:31 PM on 16 February 2010
    Did Phil Jones really say global warming ended in 1995?
    Hi Would you have a link to either a Non Paywall version or a discussion of either or both of Murphy 2009 and Von Schuckman 2009. Many thanks 40 Shades
  39. Dikran Marsupial at 20:26 PM on 16 February 2010
    Did Phil Jones really say global warming ended in 1995?
    Jon Moseley said: "To be valid science, one must state that a measurement that is not statistically significant is equivalent to ZERO." The thing to remember about statistical tests is that "absence of evidence is not evidence of absence". If you treat the trend as equivalent to zero you are saying that the lack of statistically significant evidence for a positive trend is evidence that the trend is zero, which is not correct. This is precisely the assumption you make when you criticized the models "Furthermore, the observed results are in conflict with the predictions of the computer models." For there to be a model-data conflict, the error bars of the observed trends need to be outside the spread of the modelled trends. If you did the comparison properly there is no conflict.
  40. Did Phil Jones really say global warming ended in 1995?
    jasonk: The reason a shorter time frame is less statistically significant for the same trend is that noise tends to average to zero at longer time scales. this also demonstrates the effect. Also, it's less likely that noise will always 'add up' to a trend over 20 years than it will do so for a shorter time period. If you think of it as flipping a coin each time with heads meaning noise goes warmer, tails cooler, then it's clearly less likely and you can claim higher statistical significance. As for +0.12 -0.12 = 0, that's not how it works in trends. If you take 1995-2009 you get +0.12K/dec and this includes the 'cooling' period from 2002. It just so happens that 1995-2002 is a trend of +0.26K/decade. And you can't add trends anyway unless they're for equal time periods. Eg if you raise temperatures at +0.2C/decade for 50 years you end up 1C warmer than you were before. If you then cool at 0.2C/decade for 10 years, you'll only cool by 0.2C and you'll still be 0.8C warmer than you were 60yrs ago. The 60 year trend will remain positive, even though +0.2 - 0.2 = 0.
  41. Did Phil Jones really say global warming ended in 1995?
    JonMosely: do you have a reference for that claim so I can check? As I understand it, your precision may be near perfect, but the system may be intrinsically 'noisy' (eg El Nino is a real physical phenomenon, but in the context of looking for warming it contributes to 'noise'). So your precision may be enough to detect a trend, but without knowing how to fully account for all of the noise, you must treat it as such and determine based on the known high frequency noise in the data whether it is statistically significant or not. So Jones is right; there is a trend, but there is a 5%+ chance that it could have occurred from noise. Which is unsurprising, given that an ENSO switch is 0.4-0.7C in a few months and 'global warming' is a trend of 0.1-0.2C/decade atm and so people tend to talk about longer time periods. Please correct me if I'm wrong and point me towards where I can fix my understanding.
  42. Dikran Marsupial at 20:01 PM on 16 February 2010
    Did Phil Jones really say global warming ended in 1995?
    JonMoseley says: "Any measured change or trend that is not statistically significant DOES NOT EXIST scientifically." No, that is incorrect (but a very common fallacy). If a measurement is not statistically significant it means there is insufficient evidence to reject the null hypothesis. In this case it means the trend is too small (w.r.t. the noise) to be confident that the trend is not zero. That is not at all the same thing as "the trend does not exist scientifically". Of course one would not build an argument solely on a non-statistically significant trend, but then again AGW theory has a much broader base of evidence and nobody (who understands statistics) would claim that a short term trend is proof of AGW. "Furthermore, the observed results are in conflict with the predictions of the computer models. Therefore, the computer models are wrong." Actually that is not correct either, see the paper by Easterling and Wehner, which shows that the internal variability of the climate means that there will be occasional decadal trends showing no warming or even cooling, and that these are seen in the output of the models. http://www.agu.org/pubs/crossref/2009/2009GL037810.shtml A common demonstration of the Dunning-Kruger effect in discussions of climate is a lack of understanding of what the models actually say.
  43. The Dunning-Kruger effect and the climate debate
    Chris #57 I did read the whole article, John started each small section with a skeptic question (quotes and italics). All very simplified but the question of uncertainty and poor understanding of some systems still needs to be raised. Based on the examples John raises. 1) CO2 - Few believe that CO2 levels aren't rising in the atmosphere yet there does appear a case for what that means for future climate and maybe more importantly it's impact on society going forward. Many of the non-peer reviewed source issues with the IPCC seem to focus on this later aspect. 2) Solar - Just from John's list of papers solar seems to have contributed between -1.3% to 50% of 20th century warming. Scope for improvement there. IPCC seem to go with negligable affect. There are other solar scientists that take a different approach such as Friis-Christensen and Henrik Svensmark. That solar breaks down some the present period is as true as CO2 and temp break down 1940-1970. The climate is a complex thing. 3) Paleoclimatology - Methods and conclusions have been critised in both blogs and peer-reviewed papers. And it appears the IPCC presentation of this shows signs of political (with a little 'p') interference. You have to question throwing away 75%+ of your data to come to a 'desired' conclusion. "Question everything"
  44. Arkadiusz Semczyszak at 19:49 PM on 16 February 2010
    Did Phil Jones really say global warming ended in 1995?
    1. "No Comments" may be used at most trends: 70 + / - 10 years x n. They include most cycles: Gleissberg's; AMO+PDO, THC, EN(LA)SO. 2. Marcus repeats: the sun "expire" ... and the warming continues. However, the present warming is consistent with the millennium cycle. I recall a diagram: http://www.rni.helsinki.fi/research/info/sizer/fig2big.jpg; and I am adding a new: http://mclean.ch/climate/figures/GISP_to_4Kbp.gif. Present Warming is greater in NH than the SH. Rahmstorf has repeatedly said, that the Millennium cycle is dependent on the cycles of the sun - but not directly. So far, created a few theories to explain this relationship.
  45. Working out future sea level rise from the past
    JonMoseley #86 i'm a bit confused. Are you claiming that sea level falls in a warmer world and rises during colder ages? Are you saying that in Antarctica there's not ice melting in summer? It seems to strongly contradict the evidence ...
  46. Arkadiusz Semczyszak at 19:09 PM on 16 February 2010
    Did Phil Jones really say global warming ended in 1995?
    Using the trend from 1995 - 2009 without the commentary is wrong. Because it covers the end of the transition from the cold phase in the warm AMO, which is always sharp. In turn, it is wrong to use the 1998-2009 trend - without taking into account the impact of EN(LA)SO.
  47. Working out future sea level rise from the past
    JonMoseley, do you think you've just discovered the concept of center of mass? Do you think that people here (let alone the climatologists) do not know about it? Come on ...
  48. Did Phil Jones really say global warming ended in 1995?
    The question asked by the BBC journalist had clearly the intention to be equivocal. Indeed, 1995 is the last year for which there is not a statistical significant trend. It's easy to make a trend not statistically significant, just make it short enough, but it can not disprove (nor prove) anything. If you want to clarify the recent apparent slow down of temperature increase a better question would be: "is the recent (apparent) slow down of the temperature increase statistically compatible with the long term trend?" The answer is a sound yes.
  49. Did Phil Jones really say global warming ended in 1995?
    Re #14, mazibuko -- good points. You might add that power analyses should be employed when trying to determine an appropriate choice of alpha prior to hypothesis testing. Hmmm, I can't find the reference I want right now. Here Tamino has some information on the amount of noise versus signal to expect for these kinds of tests. Another consideration is the issue of whether or not one is testing a one-tailed or two-tailed null hypothesis. The link above (hopefully it works) shows a two-tailed confidence interval. I don't know if Jones' test was one- or two-tailed, but really it should have been one-tailed. A one-tailed test is more powerful (more able to reject the null hypothesis). Almost finally, independent from the issue of signal versus noise, there is the issue of what's special about 15 years for this particular test. Hypothesis testing requires that the test be constructed a priori. It's invalid to watch as data are added, going forward in time, and then to make simple conclusions (ignoring the non-independent tests that have already occurred) when a calculated p-value finally goes above or below 0.05. That is, you can't cherry-pick the time frame. Finally, JonMoseley in #3 might do well to construct another hypothesis test: Ho = the rate of warming does not differ significantly from a rate of 0.2 C/decade. Failing to find significance there means, if you apply Moseley's funny interpretations of statistical rules, that differences with consensus expectations of AGW do not exist.
  50. Is CO2 a pollutant?
    JonMoseley, there is actually rather alot of science proving that CO2 warms the Earth's atmosphere... even outside of laboratories. Several examples can be found here. As to your convection hypothesis... it fails because, amongst other things, greenhouse gases do not retain heat within themselves. They absorb and then immediately re-emit the infrared radiation. Since this energy is re-emitted in an essentially random direction this means that some of the infrared radiation traveling from the Earth's surface up and out into space is instead reflected back down to the planet by greenhouse gases. If you refer back to the link above you will see that it includes direct evidence of this absorption and re-emission in that radiation escaping the atmosphere shows a reduction in the wavelengths absorbed by carbon dioxide while radiation coming down from the atmosphere shows an increase in those same wavelengths.

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