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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 61501 to 61550:

  1. CO2 lags temperature
    Your article states "CO2 amplifies the warming which cannot be explained by orbital cycles alone." How do you square that with Roe, G. (2006), In defense of Milankovitch, Geophys. Res. Lett., 33, L24703, doi:10.1029/2006GL027817 "In other words, variations in melting precede variations in CO2. Thus, the relatively small amplitude of the CO2 radiative forcing and the absence of a lead over dV/dt both suggest that CO2 variations play a relatively weak role in driving changes in global ice volume compared to insolation variations." and "Furthermore, variations in atmospheric CO2 appear to lag the rate of change of global ice volume. This implies only a secondary role for CO2 – variations in which produce a weaker radiative forcing than the orbitally-induced changes in summertime insolation – in driving changes in global ice volume." Thanks!
  2. We've been through climate changes before
    "Humans survived past climate changes". Well, no, not really. Our "cousins" the Neanderthals didn't survive the last ice age.
  3. A Sunburnt Country
    JH inline @58 and @59, if a poster is identified as trolling, there should be no question of feeding them as their posting privileges should have been removed. However, while their posting privileges have not been removed, the correct policy for posters who care about truth and our future is to rebut their nonsense when it appears. It is intolerable that we should have a moderation policy that is both unable to silence trolls, but does silence the rebutals of the the myths they spread.
    Moderator Response: [JH] The current Comments Policy does not explicitly state that trolling is bannable offense. If you want to chase Norman's tail, that is your perrogative.
  4. A Sunburnt Country
    muoncounter @61, the previously linked (@57) Engdahl and Villsenor indicate that the centennial catalog is complete for magnitude 5.5 plus earthquakes from 1964 forward. Therefore the approximately 50% increase in magnitude 6 plus earthquakes since 1980 as shown by the USGS is almost certainly accurate. It is not statistically significant in that it does not show significant long term deviation from the centenial average of 150 earthquakes per year, but it is a real difference between the (historically low) number of earthquakes in the 1980s. What remains a mystery is why Norman thinks an approximately 50% increase in magnitude 6 plus earthquakes since the 1980s proves the inaccuracy of the 50% increase in geophysical catastrophes as recorded by Munich Re over the same period.
  5. We've been through climate changes before
    Lucas Verma#17: "During the Holocene Climatic Optimum... for the Northern Hemisphere, longer more intense summers and the same duration but more intense winters.... southern summers and winters were more moderate." Do you have any references to support this? "Were winters ten degrees colder and summers ten degrees hotter..." Do you see a mechanism that results in this combination?
  6. A Sunburnt Country
    Norman#58: Thanks for correcting my error; 2011 does indeed total 205 mag 6 or greater earthquakes. However, the question of statistical significance still stands. In addition, your position is based on half an hour with a spreadsheet and is without any published references. Until you can answer the challenge of finding some literature that supports your position, it remains unsubstantiated. There are factors that might explain your perceived trend: As others have pointed out, the impact on the numbers of improved detection systems worldwide is something professional seismologists are able to quantify. This post is about floods, droughts and impacts of climate change. Geophysical catastrophes are a sidebar. Until you produce suitable references, your excursion into armchair seismology has little weight and can be construed as an attempt to hijack this thread.
  7. A Sunburnt Country
    Norman @59, you are correct. I have not been following your posts as I find you to be a dishonest time waster. Never-the-less, you have acknowledged that there is no overall trend, so my previous post was beside the point, and the accusation of cherry picking was inaccurate I would say I apologize for that, except the accusation is inaccurate as to its basis, but not wrong. If your point is explicitly to criticize the Munich Re graph, there is no justification for your using a data base of hazards to criticize a data base of catastrophes. This is particularly the case in that the USGS provides several data bases of catastrophes which you could have consulted. You could have, for example, looked at the number of earthquakes causing 1000 or more deaths, which show half decade figures as follows: 1980-84: 6 1985-89: 5 1990-94: 5 1995-99: 9 2000-05: 4 2005-09: 4 2010- April 2011: 3 Hardly evidence of a rising trend. You might also have tabulated the significant earthquakes, not all of which are magnitude 6 plus, but of which there are a lot less than the 6 plus earthquakes. You may find a rising trend there, or you may not. Given that you have so vehemently argued in other threads that the Munich Re data is irrelevant because it measures catastrophes, not hazards, it is inexcusable (and very selective) for you to not make this distinction when you criticize their data now. What is more, and perhaps more important, is the fact that Munich Re show a 50% increase in geophysical catastrophes over the period since 1980. How then, can you by pointing at data which shows a 50% increase in earthquakes over the same period call their data into question? What is your argument here? That the rise in Munich Re's geophysical catastrophes matches the rise in earthquakes and therefore it must be inaccurate? Is that seriously your argument? Finally, Munich Re's data is based on insurance data and newspaper reports. It is known to understate catastrophes in areas with low take up of European (and US) insurance such as Asia, South America, and particularly Africa for that reason. This does not mean the trends they show are not representative, particularly as similar trends are shown in areas with high population density and extensive insurance take up over a prolonged period (such as Germany).
  8. Rob Honeycutt at 10:05 AM on 10 March 2012
    Peter Sinclair interview with Michael Mann
    One would think that if you were invited to conduct an inquiry at the invitation of a Congressman that you'd at least attempt to bring someone - at least one person - with some understanding of climate systems. Maybe that's just me. I remember back in the day when C Everett Koop was asked by President Reagan to do a study on the health effects on women who had had abortions. The expectation being that, if there were post-procedural impacts there might be reason to ban abortions. Koop, who was appointed by Reagan, stated that the results of the data did not support the position. There's a pretty good wiki account of this. http://en.wikipedia.org/wiki/C._Everett_Koop
  9. We've been through climate changes before
    Thanks John Russell @7 four giving us verbal strength in dealing with denialists. There is a saying "don't cut the branch on which you're sitting", invented I guess by loppers. It's becoming obvious that the "civilisation" is doing that by mining and burning fosils and altering the carbon cycle in unprecedented manner. The problem of altering carbon cycle with consequence of AGW is just one example. Another is land use change, forest destruction, chemical contamination, which all contribute to alteration of environment and ongoing mass species extinction. Overuse of DDT was one example. Coal Seam Gas mining is another emerging example (both chemical contamination and carbon cycle alteration is involved here). Until the economical balance of so called "civilisation & proggress" does not include the environmental sustainability, mankind will continue "cutting the branch on which it's sitting"
  10. We've been through climate changes before
    An impact powerful enough to vaporize all the world's oceans would do it, but I don't think it is possible to do it just with co2, and civilization would collapse long before. I think civilization could collapse as soon as 2100. Most major cities around the world are close to sea level.
  11. Peter Sinclair interview with Michael Mann
    Michael Mann seems to becoming more feisty and combative by the day. It is as if his shackles have been ripped off. Here's hoping we see and hear more from him.
  12. A Sunburnt Country
    Tom Curtis @ 56 I do not think you have read my previous posts based upon this comment. "Indeed, it is quite droll of you to cherry pick a short period which gives the appearance of a rising trend when no such rise can be seen in centenial records:" I think you are a very intelligent person but I do not think you have followed my line of thought at all or understand the point I was making with the earthquake data. So to get you in the loop. The Munich Re graph in the OT starts at 1980. I am not trying to make a conclusion that earthquake numbers are overall rising. (note the not). I was pointing out a simple fact that the Munich Re chart was showing a decline or at least a flatline geophysical related catastrophes. But from 1980 to 2011 the frequency of 6+ magnitude (considered strong and will damage populated areas if they strike there) has increased. If you actually read some of my posts you will have seen this. Please read post 41 and you will see me address this very issue you are bringing up.
    Moderator Response: [JH] Please do not feed this troll.
  13. A Sunburnt Country
    muoncounter @55 You did not look at the date on your source, it only goes to August 2011, it is not the full year. Completed list of 6+ earthquakes in 2011. 185+19+1=205
    Moderator Response: [JH] Please do not feed this troll.
  14. Peter Sinclair interview with Michael Mann
    Kevin C: The fact that we haven't all asphyxiated is pretty good evidence that CO2 is well-mixed in the atmosphere, and even the science-ignorant such as myself can figure that one out. :)
  15. Peter Sinclair interview with Michael Mann
    Caveat to the above: The number of total & 5-star reviews is as of the time of the posting of the above comment.
  16. A Sunburnt Country
    Sorry, I forgot to include the link to Engdahl and Villsenor in my previous post.
  17. Peter Sinclair interview with Michael Mann
    It's probably worth mentioning that Amazon indicates of the 96 reviews posted so far, 61 are 5-star reviews.
  18. A Sunburnt Country
    Norman @54, I cannot help but notice that you failed to indicate the annual average number of earthquakes of magnitude 6 or greater on your chart, according to the USGS (noted by the red line below): The annual average is that determined by the USGS from observations since 1900. Indeed, it is quite droll of you to cherry pick a short period which gives the appearance of a rising trend when no such rise can be seen in centenial records: Figure 3 a from Engdahl and Villsenor. The slight upward trend in 6.5 plus earthquakes from the 1900s to the 1940s is probably an artifact due to improved observations as is shown by a lack of such a trend in magnitude 7 and 7.5 plus earthquakes, which being larger can be detected on a sparser network.
  19. A Sunburnt Country
    Norman: Your source is a vanity blog site; the author is someone who has also written on 'the 10 most annoying English phrases.' But he at least poses a sensible question about this apparent trend and concludes: "To answer that, you'll have to ask a seismologist." The seismologists in question work for the USGS - and they say there's no statistically significant increase. "There was also 205 6> magnitude quakes in 2011" My source shows 149. "Regardless of standard deviation the trend is up." No. With as high a standard deviation and as poor a correlation as these data show, the trend is insignificant. This is a debate that has taken place on many threads. Statistical significance is paramount. People who make conclusions based on statistically insignificant data are just making noise out of the noise in the data. Once again, until you have the published research documenting this so-called trend, you have very little credible evidence. And you've pulled this thread into a relatively insignificant tangent. Again.
  20. Peter Sinclair interview with Michael Mann
    Actually, I don't find the CO2 point obvious. In response to a 'skeptic' who was claiming that CO2 formed a layer at the bottom of the atmosphere (yes, really!), I set out to demonstrate how CO2 should be mixed through the atmosphere using the equation for the entropy of mixing. The problem is that you get the wrong answer. If entropic mixing were the only thing going on, then the relative concentration of CO2 would decrease with altitude with a scale height of 5-10km. But it doesn't. Measurements show that it is pretty even throughout the troposphere. So there are other mixing effects going on. Clearly in the troposphere convection is going to be the big player. But I can't quantify the mechanism from first principles. I suspect that doing so is horribly complex. However, the fact that CO2 is well mixed should certainly be well known to anyone with any knowledge of the field.
  21. We've been through climate changes before
    @19 It is impossible to push the Earth's climate to a Venus like state.
  22. A Sunburnt Country
    muoncounter @53 I have to state I do enjoy your subtle and clever humor you put into your posts (205 in 1995 so earthquake increase has stopped...good one). Since I could not show my Excel sheet here someone has done it. source. There was also 205 6> magnitude quakes in 2011 so the graph will go up a bit from the image I have linked to. Now tell me how this does not show an upward trend from 1980? Regardless of standard deviation the trend is up.
    Moderator Response: [JH] Please do not feed this troll.
  23. We've been through climate changes before
    Unless we push the climate to a Venus like state, it is pretty certain we will survive as a species. It will be like the Roman Empire collapsing times two orders of magnitude. Our great great grandchildren will have Atlantean type legends of these god like beings that could talk to people on the other side of the world, that flew to the moon and who actually turned rock into metal. Science fiction keeps coming true.
  24. Peter Sinclair interview with Michael Mann
    Those of you who have read Dr. Mann's book might want to consider putting up your own review at amazon.com (in order to counter the "bad" reviews put up by those who clearly haven't read the book). If you don't have time to do that, consider leaving comments setting the record straight, or just vote up/down the reviews based on their quality and whether or not the reviewers appear to have read Dr. Mann's book. Dr. Mann really appreciates gestures of support like that. Linky here for convenience I did my part and posted a review entitled, "Attack of the C-Students".
  25. Peter Sinclair interview with Michael Mann
    Yeah, we live on a layer cake planet!
  26. We've been through climate changes before
    Chris G at 05:31 AM on 10 March, 2012 More abrupt indeed. PETM took a time of the order of 10,000 years to warm some 6ºC. Now we're talking about the potential of warming as large as that, happening in one or two centuries.
  27. We've been through climate changes before
    One must be careful with global averages. During the Holocene Climatic Optimum, global annual average temperatures may not have varied much from average. But that does not mean significant variation did not occur. But orbital variation meant for the Northern Hemisphere, longer more intense summers and the same duration but more intense winters. Conversely, southern summers and winters were more moderate. Were winters ten degrees colder and summers ten degrees hotter, the average might be the same, but the climate would be much more extreme.
  28. kampmannpeine at 05:44 AM on 10 March 2012
    We've been through climate changes before
    Thanks, Sarah ... this is just a super nice addition to my public lectures for "normal citizens" in our local area near Hannover, Germany, which I will give coming May ... but also lot of comments are very useful with all their knowledge and graphs ... The paleoclimate is one of the "Tummelplätze" (German for "play areas") for our friends the denialists ...
  29. Pete Dunkelberg at 05:35 AM on 10 March 2012
    Peter Sinclair interview with Michael Mann
    Duly noted in this video is a point in Congressional hearings where it becomes painfully obvious that Wegman is not a climate scientist and does not understand the most basic climate science, as he notes that CO2 is heavier than air and should, as a result, reside close to the planet surface.
  30. A Sunburnt Country
    Norman#49: "put the year and the number and generate a graph and select make a linear trend and tell me what you see." Yes indeed, a positive linear trend. With an R^2 of 0.42 "That would be the approach of a scientist to actually enter the data and see what comes out." Actually, a scientist (and perhaps the USGS has a few of them about the place) would be interested in a slightly more sophisticated treatment of these numbers. For starters, this list gives an average annual mag >6 count since 1970 of 135, with a standard deviation of 28. So any increase up to 163 per year is within one stddev. BTW, the max was 205 in 1995. So you have to say it hasn't increased since 1995; therefore this mysterious increase in number of earthquakes has stopped. I believe I asked here if this so-called increase in earthquake frequency been published. If not, why not? Or has an individual with internet access and a spreadsheet found something that no one else has recognized? Odds on that, anyone?
  31. We've been through climate changes before
    Indeed. We are probably looking at something like PETM II (a sequel, not a remake, more abrupt onset and other diffs). I wonder how our agriculture will do under a PETM-like climate.
  32. We've been through climate changes before
    "Human civilization is roughly 12,000 years old, as defined by the start of permanent settlements and agriculture. ... Global temperatures haven't varied by more than ±1 °C" This is a key point that buffoons like RPerry do not and cannot comprehend. Prior 'natural cycle' climate changes have not required much in terms of a global temperature change. There are many versions of this type of graphic floating around. It defines our very narrow (+/- 1C)'comfort zone.' --source Anthropocene climate change will push us out of that comfort zone, much to our peril.
  33. Dikran Marsupial at 04:47 AM on 10 March 2012
    The Independence of Global Warming on Residence Time of CO2
    @Sascha, cheers, glad to hear I have been of some use! @Rob, many thanks for the reference, it'll be useful if I ever find the time to write up an advanced version of the residence time rebuttal!
  34. Lindzen's London Illusions
    #58 Tom Curtis Glad to know someone was curious to go and see what I was talking about. However, you could have saved yourself a lot of trouble and just looked at the screenshot of this Keeling v Temperature graph on either of my first two Lindzengate posts ("Open Letter to Richard Lindzen" ... or "Prof. Lindzen try this instead"). Had you done this you might have been able to spot the caption I have inserted underneath the embedded image, which reads as follows: "If you stretched the temperature axis far enough, they would have correlated perfectly. Therefore, this [not now] 'missing' graph neither proves nor disproves anything." This is why re-inserting the graph into the PDF changes nothing. In fact, it implies that Lindzen doesn't even appreciate why it is so meaningless and misleading. This is why I was so gobsmacked by the whole thing. It was either complete incompetence or transparently disingenuous.
  35. Interactive mythbusting in Lane Cove
    Sapient Fridge, I agree entirely but it's fascinating to watch others go through the same process and come to the polar opposite conclusion. On more than one occasion I've come across someone who has claimed to have been reinforced in their 'scepticism' precisely because those they are debating with have an answer for everything. On the other hand I wonder if this is a deliberate tactic to avoid having to face reality. Are some of those who continuously challenge the deficit model doing so in order to impede effective communication?
  36. A Sunburnt Country
    A factoid worth remembering: "Typically, 1,300 tornadoes strike the U.S. a year. There were nearly 1,700 tornadoes in 2011, falling short of the record 1,817 tornadoes set in 2004." Source: "Warmest Spring in Years to Fuel Active Severe Weather" by Meghan Evans, AccuWeather.com, Mar 9, 2012 To access this timely article, click here.
  37. Lindzen's London Illusions
    Tom, this is precisely the point that too few are willing to push on RC, Gavin included. I know he, Gavin, and others want to keep accountability in-house, but this is an abuse of power issue that affects science across the board. Lindzen is smart. He knows just how far he can push the game before he starts to materially suffer (i.e. before the source of his power, his status as a respected scientist, suffers). Many are willing to give him the benefit of the doubt and accept his admission of error--and let the situation go. Lindzen depends on that water under the bridge. It allows him to make strategic "mistakes" again and again. The outcomes of these rhetorical moves on the projects of science (and climate science specifically) and representative democracy far outweighs the contributions that Lindzen could make (or would want to make) with the rest of his career. The evidence for that is the attention that Lindzen gets here and at RC. People respond to Lindzen with a lot of energy. That doesn't suggest he's harmless, and, indeed, empowers him further in the minds of the doubters. I know what Gavin and others fear: if scientists can be put over the legal barrel for making mistakes, then those who control law will begin to control science. The mess that might potentially create is indeed frightening--much like the current fight over education in the US (that few actual educators are allowed to take part in). Yet is the proper response then to write chastising blog posts that few in the democracy (voters or their "representatives") will ever see? Is it to win a local battle while the war goes to pot? It's a complicated situation, but I expected a stronger response from the people who have the power to counter this type of serial abuse. Imagine you visit a city you've never been to before. You have to be at a hospital in this city by a certain time, or you'll suffer some nasty health problems. You hail a taxi. The taxi driver begins driving you toward your destination . . . you think. The taxi has very darkly-tinted windows, and there is a barrier between you and the driver. The taxi driver calls in to the central garage and tells everyone he's driving this fare to the hospital, and the thousands of other taxi drivers can track the progress of the taxi on the big board. The taxi begins to make random turns. It's not going to the hospital, or if it is, it's not going directly. The driver is delaying arrival. You notice that it's taking a long time, but this is a big city, and you don't know the route. The driver says, "Yah, it's across town, and traffic is terrible." Other taxi drivers note that the route your driver is taking is not at all ideal. Some stay silent. Some blog about it. One driver standing next to the company president says, "I don't think the fare is really all that sick. Maybe a drive around the city will do him some good." Some call the taxi and tell the driver he's making a mistake. The driver responds by saying, "Yes, you're right, I'm sorry," and he begins driving toward the hospital. But then he starts going in circles again. Some try to call the fare (you) directly, but you don't speak the same language, and even when you can understand, you're not sure who to trust. Meanwhile, your body is deteriorating. The other taxi drivers don't want the police to get involved. What is the president of the taxi company doing? You're close to passing out. Yah, I know--an off-the-chest rant. Consider it a contribution to the analogy collection.
  38. Oceans Acidifying Faster Today Than in Past 300 Million Years
    We have emitted 500+ gigatonnes carbon so far and will emit another 300 gt carbon in the next thirty years. If the PETM resulted from a 2100gt carbon release we will be halfway there pretty soon. In 1950 there were 2.5 billion people and Co2 emissions at 5gt annually, there are currently 7 billion people and we collectively emit 30 gt Co2 each year. In order to get Co2 emissions back to 1950 levels every human on earth would need to reduce their individual contribution to less than one ton Co2. The oceans were acidifying even at the Co2 emission of the 1950s. Does anyone out there have any idea how to get 7,8, or 9 billion people to voluntarily comply? Is anyone reading this trying to live on less than one ton of Co2?
  39. Robert Murphy at 02:59 AM on 10 March 2012
    We've been through climate changes before
    @11 Milankovitch cycles
  40. We've been through climate changes before
    Do you mean the cycle of glacial and interglacial periods or the fact that we have an ice age containg these periods. The fact that there is an ice age is beieved to be a matter of continental configuration and CO2 levels. We have an ice age when warm currents can't get to the poles and CO2 is low enought to allow an ice build up. The glacial-interglacial cycle is believed to be controled by thre Milankovitch cycles, cycles in Earths orbital and rotational parametters. Thes affect the distribution of radiation recieved by the Sun. How much Summer sunlight is recieved in high Northern lattitudes seems to be what is important. This is greatly amplified by the albedo changes from glaciation and the sequestration of CO2 in the ocean as temperatures fall.
  41. We've been through climate changes before
    I was wondering if someone might explain why these periods of glaciation took place? Volcanoes? Vegetation sequestering CO2? Asteroid impact? Why? Just curious to know, thanks.
  42. We've been through climate changes before
    "Yes, our climates change. They've been changing ever since the Earth was formed." Or like the defendant of the serial killer: "Yes, they died. People die ever since they appeared on Earth."
  43. The Skeptical Chymist at 01:09 AM on 10 March 2012
    Interactive mythbusting in Lane Cove
    I'd like to second Gillian suggestion of a metaphor/ analogy archive. Using John's "open fridge" explanation would probably have saved a lot of time explaining the same issue to my father in law. As a scientist I like give science answers to science questions but appreciate that a metaphor/ analogy is a good way to help people grasp a concept. I remember Stephen Schneider had a good water level in a bathtub analogy to explain how human C02 emissions could raise atmospheric levels given the high level of natural flux occurring at the same time.
  44. A Sunburnt Country
    Re Norman@46 The reinsurance company data is based on well defined insured/insurable events.You expect and demand a granularity it does not necessarily have. yours Frank
  45. We've been through climate changes before
    We are going well outside anything homo anything has experienced. CO2 has not been this high in the time of man.
  46. Interactive mythbusting in Lane Cove
    Sapient Fridge, it's called consilience. The idea is that a unified set of laws underlies all of nature. Explanations obtained in one field of research will be consistent with explanations obtained in another field. That is why the more different lines of evidence support a conclusion, the more confidence scientists have in it. Evolution is a superb example. It undelies all of biology and results consistent with it turn up all over the place. The same applies in climate science. The same explanations that explain the heating now explain the amplification of the Milankovich Cycles to cause the glacial cycle. And they turn up all over the place in climate studies.
  47. Lindzen's London Illusions
    I was wondering what Martin Lack (@44) was referring to, so I finally had a look. What I found was a Wood for Trees graph, which I have recreated and shown below: Lindzen says of the graph that
    "Just to put this into perspective, a colleague took all the data sets he could find of temperature change since 1996, and, you know, this is the [incomprehensible] you could pick one or the other. It's about a tenth of a degree here or there. But basically if you compare it to the change in CO2 its pretty clear that, you know, by any normal standards this is pretty flat no matter which [incomprehensible] you pick, and arguing about the difference in these is probably a fools errand."
    That is pretty incomprehensible as an argument. It appears as though he is about to make the argument the graph is obviously designed for, ie, to argue that CO2 and temperatures do not correlate so that CO2 cannot be a causal factor in the temperature increase. But he never actually makes that argument! He has a ... I don't know - perhaps a seniors moment, perhaps an attack of conscience, and switches midstream to arguing that the differences between temperature indices is so small that it doesn't matter which one you pick for analyzing the data. Now that argument itself is obviously false. It may appear true if you carefully select just three temperature indices from twenty-two available from Wood-for-Trees. More importantly, it uses just two of three major global temperature indices. It is inconceivable that the Alfred P Sloan Professor of Meteorology at MIT should not know of the NCDC, GISS and UAH temperature indices. Particularly given that he had just been criticizing one of them just moments before. So when Lindzen say's that, "...a colleague took all the data sets he could find of temperature change since 1996...", he is knowingly misrepresenting the facts. More importantly, and Lindzen knows this as well, over such short (cherry picked) time periods, choosing other temperature indices, makes a significant difference: Martin may well accuse me of chasing of after a side issue on this, but I cannot criticize Lindzen for making an argument he did not in fact make, no matter what his intentions when setting up the slides. And Lindzen pulled out of making the "no correlation" argument at the last moment. It is well that he did not make that argument. If CO2 increase and temperature increase had been correlated on the graph, then (all else being equal) a 0.4 W/m^2 difference in greenhouse warming would have caused a 0.8 degree C change in temperature, which equates to a climate sensitivity of 8 degrees C per doubling of CO2. In fact it would be much worse, in that aerosol forcing and solar forcing are known to have been significantly negative over the period in question, while the ENSO trend was also cooling. Consequently, to achieve the sort of correlation that the graph suggests should exist according to the IPCC, the climate sensitivity for a doubling of CO2 must be much greater than 8 degree C, rather than the 2 to 4.5 degrees C commonly accepted. The conclusion is inevitable. Anybody who uses this or an equivalent graph (and they are common on the web) either knows nothing about climate science, or is a deliberate liar.
  48. Lars Karlsson at 21:34 PM on 9 March 2012
    We've been through climate changes before
    "Global average temperatures were 10-12 °C hotter than today" I believe that should be °F (see e.g. here).
  49. John Russell at 21:15 PM on 9 March 2012
    We've been through climate changes before
    I recommend that the instant, snappy, response when someone says,"...oh, the climate has always changed!", should be "...sure -- but not while civilised humans have been around!". Then if you get the opportunity to continue, go on to say, "...history suggests that a stable climate is necessary for a stable civilisation; that's why by changing the climate today we're playing a dangerous game that risks all the benefits of living in a civilised society". In my experience, in a verbal confrontation, this response works well with both the initiator and onlookers. You've not undermined your opponent, but you've just suggested that it's a lot more complex than the original bare denial statement would suggest. It's more difficult for them then to backtrack. It also makes it more difficult for them play the old "...you greens want us all to go back to the Stone Age", meme; as you can say, "No, by preventing climate change we're trying to stop society reverting to the Stone Age." I hope that helps. 'Climate's always changed' is such a common meme that it's worth memorising the snappy one line response. As we all know; it's rare that we can have a rebuttal which can be as short as the meme.
  50. Sapient Fridge at 21:13 PM on 9 March 2012
    Interactive mythbusting in Lane Cove
    Reading this thread made me wonder what makes me, myself, so convinced that AGW is happening. I've come to the conclusion that it's the fact that no matter how deeply one investigates one finds answers (or at least hypotheses). There are no big unknowns in the mainstream theory. If you look at some of the other "explanations" they quickly come to a halt with something unknown. For example anyone who accepts that it's warming but denies that GHG is responsible comes to big unknown when you ask where the extra energy is coming from, given that we can prove it's not the sun. People end up saying that they don't know (or care) where the energy is coming from, they are just sure that CO2 is not responsible. Evolution has a similar feel about it, and the talk origins web site has a similar purpose to this one. Including an "arguments" section.

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