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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 108351 to 108400:

  1. Climate Change: Past, Present, and Future
    Albatross... I've actually used that very same video to turn a few skeptics into believers. The other one that always seems to get skeptics thinking is the electric dragster video.
  2. New temperature reconstruction vindicates ...
    Johnd, helps to remember that researchers in the topic are not primarily invested in policy outcomes, obsessive scrutiny of 12 year old papers, etc. Life moves on, there are new things to investigate. There's also the matter of money. Who's going to pay for repeating the research? The iconic Keeling lost his Antarctic sample continuity due to funding cuts.
  3. Climate Change: Past, Present, and Future
    Bamboozled @7, Was it this one?
  4. Climate Change: Past, Present, and Future
    I saw an interesting experiment/demonstration a while ago that rather neatly demonstrates to the dis-believers why CO2 causing warming is more than just a theory: Have a glass cylinder about e.g. a metre long and e.g. 10 cm diameter. At one end of it (outside the cylinder) put a candle or other heat source. At the other end (also outside the cylinder) put a thermal camera, pointing at the candle. On the camera's display, the candle should show up perfectly. Now fill the cylinder with CO2. You'll still be able to see the candle, but the IR camera will not. This proves that CO2 acts as blanket over the atmosphere - energy can still get to the surface as short wavelength light, but the longer wavelength IR radiation can't escape back out into space. I'm not sure where I saw it now. I've just checked on youtube and am unable to find it. Maybe someone who is better at writing and a little more scientifically literate than me can turn my summary into a simple demonstration? It seems to me that it is an approach that is not often tried: instead of using historical data (which people refuse to believe or say that it's just a coincidence), how about demonstrating the mechanics in a repeatable way?
  5. New temperature reconstruction vindicates ...
    Albatross at 08:19 AM, thanks I missed that early comment and only had the abstract to go on. However I am still not clear where the reconstruction ends and left wondering what proxies could provide data for all but the last couple of decades. Surely for the sake on continuity and validation of the proxies themselves, the same data should be continued to be progressively collected as time moves forward.
  6. New temperature reconstruction vindicates ...
    Johnd I think that we are getting our wires crossed. The authors are quoted @4 saying: "The proxy reconstruction itself does not show such an unprecedented warming but we must consider that only a few records used in the reconstruction extend into the 1990s." So the reconstruction (base don limited proxies) goes into the 90s. From the figures shown here, their reconstruction seems to compare very well with the thermometers over the remainder of the instrumented record before the 90s.. I do not know what calibration/training period they used (the paper is behind a pay wall). Maybe Ned can help?
  7. Climate Change: Past, Present, and Future
    miekol #2: "Maybe its a coincidence that the temperature is rising everso slightly and the CO2 content of the atmosphere has risen everso slightly." All reconstructions of past temperatures (even the skeptic ones) indicate that the recent temperature rise is the largest in the past few thousand years. In what way is that "ever so slightly"? The phrase is even LESS applicable to CO2, which has risen 40%... and is now at a level not seen for at least 800,000 years. ptbrown31 #3: Once atmospheric CO2 levels are elevated the natural processes which can reduce them take thousands of years to work. Thus, on the time scale of the graph the difference between 'human industry emitting just enough CO2 to keep the atmospheric level constant' and 'human industry emitting no CO2' would be insignificant.
  8. New temperature reconstruction vindicates ...
    Albatross at 07:56 AM, I have and unless I overlooked it, there is no mention that the higher temperatures of the last two decades ARE NOT reflected in the Ljungqvist 2010 reconstruction itself. Perhaps others missed the omission as well? That then brings us back to the point of whether reconstructions are being validated by recent instrumental data, and if not, why not?
  9. The Phony War: Lies, Damn Lies and the IPCC
    @CW: you're still missing the point that overall temperatures were lower than today. No. See figure 1: http://www.geo.lsa.umich.edu/~shaopeng/2008GL034187.pdf
  10. New temperature reconstruction vindicates ...
    Johnd @63, please read the thread (i.e., Ned's comment).
  11. Positive feedback means runaway warming
    hadfield: The argument in the intro is: "These alleged 'positive feedback' cycles supposedly will build upon each other to cause runaway global warming, according to the alarmists." That is what is being controverted.
  12. Climate Change: Past, Present, and Future
    You might even add that... "Average temperatures at high latitudes may be 3 times and much, AND individual summer high temperatures much more than even that." In other words, don't just go running north if you're looking to cool down.
  13. Climate Change: Past, Present, and Future
    Miekol @2, "But its still a theory that CO2 is the cause" Did you mean to say "hypothesis"? Regardless, you are grossly over-simplifying things. A quick perusal of this site (which discusses and presents the relevant scientific literature on the subject) demonstrates that there is overwhelming evidence from independent sources which support the theory of AGW. It is no coincidence as some might wish to presume-- the evidence (from different scientific disciplines) is far too coherent for that. GHGs are not the only cause of climate variability of course, but recently radiative forcing from elevated GHGs has become a primary forcing mechanism and that is only going to increase as GHG levels continues to increase. If you want to debate what the equilibrium climate sensitivity is for doubling CO2, then that is still an open question. As of now, multiple, independent studies point to +3 C warming (globally) being most likely response to doubling of CO2.
  14. Climate Change: Past, Present, and Future
    "In other words, what would happen if humanity had suddenly stopped emitting CO2 in the year 2000." This should really read something like: "In other words, what would happen if humanity suddenly started emitting just enough CO2 to balance natural sinks and thus keep atmospheric concentrations at 2000 levels".
  15. New temperature reconstruction vindicates ...
    Rob Honeycutt at 07:04 AM, the tree rings was just a mere example to illustrate a point. I was asking specifically about which of those reconstructions that are the subject of this thread, thus the question was very much ON topic.
  16. Climate Change: Past, Present, and Future
    Its a wonderful graph. But its still a theory that CO2 is the cause. Maybe its a coincidence that the temperature is rising everso slightly and the CO2 content of the atmosphere has risen everso slightly. Its just like I cannot prove to you God exists, but you cannot prove to me God does exist. Both theories God and CO2 are currently unprovable. It just needs for someone to put two and two together and come up with four.
    Response: That CO2 is causing warming is confirmed by multiple, independent lines of evidence. We have both a shorter intermediate version of the evidence for an increased greenhouse effect and if you're hungry for more meat, a more detailed advanced version. On top of that, we have an extensive list of the human fingerprints on climate change that provide further corroboration. There is no shortage of directly observed, empirical evidence and it's all given to you on a silver platter here at Skeptical Science.
  17. New temperature reconstruction vindicates ...
    Based on the second graph that shows the warmest part of the Med-evil warm period being near .3c above "0" or avg to todays global .8c above normal. So we're half a agree oC above the med-evil warm period. Also I was reading that we're very close to the Holocene climatic optimum of 5,000-7,000 years ago->"The Holocene Climate Optimum warm event consisted of increases of up to 4 °C near the North Pole (in one study, winter warming of 3 to 9 °C and summer of 2 to 6 °C in northern central Siberia)[1]. Northwestern Europe experienced warming, while there was cooling in the south.[2] The average temperature change appears to have declined rapidly with latitude so that essentially no change in mean temperature is reported at low and mid latitudes. Tropical reefs tend to show temperature increases of less than 1 °C; the tropical ocean surface at the Great Barrier Reef ~5350 years ago was 1°C warmer and enriched in 18O by 0.5 per mil relative to modern seawater.[3] In terms of the global average, temperatures were probably colder than present day (depending on estimates of latitude dependence and seasonality in response patterns). While temperatures in the Northern Hemisphere were warmer than average during the summers, the tropics and areas of the Southern Hemisphere were colder than average which comprised an average global temperature still overall lower than present day temperatures.[4" http://upload.wikimedia.org/wikipedia/commons/c/ca/Holocene_Temperature_Variations.png If we're now warmer then the midevil warm period and possibly the climatic optimum then we have to go back to the at least 115 thousand years to find possibly warmer temperatures then today. 3-4c would put us back to where we where 15+ million years ago?
  18. New temperature reconstruction vindicates ...
    Michael @57, you must be telepathic. John Cook just posted this:
  19. Hockey stick is broken
    GC, as you're still ignoring the point and restating your incorrect assertions, I can only presume you can't actually answer my question: Why would you assume that every local temperature variation is recorded in full in a global dataset? And can you point to detailed examples of where the regional reconstruction fails to pick out regional climatic variations recorded in local history, and show how that has fed into and distorted the meta-analyses? I doubt you can. The climate science community's credibility has certainly not been affected in the slightest by the historical record.
  20. beam me up scotty at 07:12 AM on 30 September 2010
    Climate Change: Past, Present, and Future
    Of course this is too optimistic now, right?
  21. New temperature reconstruction vindicates ...
    johnd... I think I'm going to leave this one alone. It would be off topic for this thread and an issue that has long been put to rest as well. If you wish to rehash this one I would suggest this thread.
  22. New temperature reconstruction vindicates ...
    Rob Honeycutt at 06:49 AM, yes, those based on tree ring proxies being a prime example. Perhaps you can identify those reconstructions that are tracking recent instrumental records to date.
  23. New temperature reconstruction vindicates ...
    Rob @56, I think he may be trying to make a straw man argument about the divergence problem in some of the dendro chronologies from 1960 onwards.
  24. The Phony War: Lies, Damn Lies and the IPCC
    "Of course not. Your severe bias agaisnt AGW theory won't allow you to believe otherwise." "bias agaisnt AGW theory"? I haven't written anything about radiative forcing. All I'm doing is pointing out that the extent of a warming rate is low as declared by the IPCC and by daily, annual, and millenial scales of change, not particularly significant. I would gladly like to see any evidence you can provide otherwise.
  25. New temperature reconstruction vindicates ...
    Could someone direct me to an image that shows temps from 0-2100 i.e reconstruction plus IPCC estimates.
  26. New temperature reconstruction vindicates ...
    johnd... Are you suggesting the reconstructions don't track the instrumental record?
  27. Blog review of scientific coherence
    @Argus, post 25 You are missing the point here. Nowhere in the article the claim is made that a coherent theory is automatically a correct theory. Of course a coherent theory CAN be wrong. What the article states however is that an incoherent theory cannot be correct. This is not an article about the correctness of AGW, it is an article about how skeptic theories can be proved to be wrong, if they are internally incoherent.
  28. Positive feedback means runaway warming
    It illustrates a mathematical fact that is irrelevant to the action of the fast feedbacks, which are what the introduction suggests the article is about. So what's the point?
  29. New temperature reconstruction vindicates ...
    kdkd@54, Maybe this will help KL out (and these data only go till 2009). I have posted before, but some people seem to choose to ignore the facts: An updated figure (Fig. 21a), can be found here (pg. 48).
  30. New temperature reconstruction vindicates ...
    KL #43: Oh, and all the temp charts in this thread seem to stop at year 2000 - missing the last 10 years of flattening at a time when claimed AGW forcing is 'the highest decade in history'. In a sense I can't believe that you're still peddling this misinformation. Can you explain how the fact that the decade 2000-2010 is the warmest decade on record is consistent with your assertion please? In fact, I think I've asked you that question before; you've never provided a satisfactory answer (you may have repeatedly ignored the question), and yet still wheel out the same old poorly thought out repetitive rubbish without justification.
  31. Blog review of scientific coherence
    HR, your post @19 is OT, and so is this. Just for balance, here is their entire abstract. Pay close attention to the last sentence of their abstract: "While the IMP [internal multidecadal pattern] can contribute significantly to trends for periods of 30 years or less, it cannot account for the 0.8°C warming trend that has been observed in the twentieth century spatially averaged SST." So, internal variability can explain some of the changes in global SSTs on a short-time scale, but not the underlying long-term warming trend. Nothing new there, researchers are well aware of the role of internal climate modes in modulating global temperatures. And SS does not attribute all of the observed warming to higher GHGs as you state HR. Instead of arm waving please provide a link to where this is stated, or better still go and argue on a relevant thread. I can't wait to see how WUWT "presents" these results.
  32. Blog review of scientific coherence
    Philippe Chantreau It's nice for a skeptic to acknowldedge the existence of that acceleration, when so many are saying that it's cooling, = = = = = = = = = = = = = = = = There are many skeptics who acknowledge this, especialy among the luke warmers.
  33. New temperature reconstruction vindicates ...
    Rob Honeycutt at 05:40 AM, on the other hand, unless the reconstructions track the instrumental data, then the assumptions made to enable the reconstruction have not been validated. The whole purpose I believe is that recent data should validate the proxy data.
  34. Blog review of scientific coherence
    Stephan, the use of the sheep analogy is a very very poor choice, though it may appeal to some, and that in itself may be telling. Those who are aware of how free markets work will say that in fact the person who offered that advice quite conceivably could be someone in touch with the real world. It could have been advice profferred on any commodity, even gold, or shares, and whilst the bean counters sit at their desks making all manners of predictions about future price directions, more often than not it is the contrarian who buys when others are selling or vice versa, or the those who have practical experience in the real world and can see the subtle signs of change that all others cannot, that offer the best advice. The apples example could perhaps be a valid analogy, but only for those who are susceptible to attracting such advice, whilst the bloke offering the sheep advice may well have his feet firmly on the ground, but unfortunately his advice may well be rejected by those without the practical knowledge of how markets work in the real world.
  35. New temperature reconstruction vindicates ...
    fydijkstra @ 39... "The red curves in the reconstruction graphs should be omitted, because the instrumental data are not comparable to the proxy records" Wouldn't that be a case of "hiding the incline?" The whole purpose, as I understand it, to looking at these reconstructions is to compare them to current warming.
  36. Philippe Chantreau at 05:39 AM on 30 September 2010
    Blog review of scientific coherence
    HR says "that the acceleration in warming during 1977-2008 is a consequence of natural variability." It's nice for a skeptic to acknowldedge the existence of that acceleration, when so many are saying that it's cooling, one of the most common skeptic arguments that this site addresses.
  37. The Phony War: Lies, Damn Lies and the IPCC
    @CW: "That is certainly not true for the Arctic or even the Northern Hemisphere, probably not true for the globe." By "overall" I clearly meant global averages. "Look at the noise in the whole Holocene ( plus or minus 1 degree C ). We haven't even exceeded that." It's not very useful to look at the proxy noise to determine averages were higher during the HCO than today. This is like looking at individual temperatures today and claiming such snapshots accurately reflect global temperatures (you know, what some deniers have done because it snowed a lot in their backyard last winter?) "And as I pointed out, the mean can be meaningless, as the seasonal variation was more extreme in the HCO." Not in the Mesopotamian settlements. The difference would have been barely noticeable at 30 degrees. "Extreme weather is caused by increased gradients." Define "gradient" in this context, I'm not sure I follow. Do you simply mean a higher difference between minima and maxima? My argument is that increasing global temps will disrupt long-phase natural fluctuations, and thus likely cause more extreme weather events. "To the extent that CO2 forcing is significant, as modeled it should REDUCE gradients and thus REDUCE storminess." Please provide some sort of science for these affirmations, and that "gradients" are a bigger factor in determining storminess than global temperature increases and the disruption to natural cycles this causes. You have yet to make that case. "I don't think it's that significant." Of course not. Your severe bias agaisnt AGW theory won't allow you to believe otherwise. "There have been weather disasters through out human history in 'warm periods' and 'cool periods'." True, but completely irrelevant.
  38. Hockey stick is broken
    gallopingcamel has kindly moved the discussion of Loehle and Ljungqvist over to the new thread, but I just want to make sure this doesn't remain here un-amended: gallopingcamel wrote This 2000 year reconstruction (Loehle 2008) shows temperature excursions greater than 1 degree Kelvin and Medieval temperatures higher than 2010. It does show a >1K temperature difference between the peak of the MWP and the bottom of the LIA. It does not, however, show Medieval temperatures higher than 2010. In fact, the warmest decades in Loehle's MWP are 0.5K cooler than 2010. Loehle's reconstruction is centered on its own 2000-year mean, and the final datum is from around 1930. In order to compare Loehle's MWP to current temperatures, it is necessary to re-center Loehle's reconstruction to match some other temperature series (e.g., the instrumental record) that actually shows the current temperature. An example of this is included in the update to this post.
  39. New temperature reconstruction vindicates ...
    KR: Yeah, it lacks context. Lots of people conveniently assume that the final point on Loehle's reconstruction is indicative of current temperature. Nope! The quote that Albatross cites a few comments back is rather illuminating. Loehle writes: my own reconstruction is set to a zero baseline for the entire 2000 yrs, so it is only possible to compare to other series that are centered likewise To be technically precise, it would only be possible to directly compare Loehle to other series that are centered on the 2000-year mean of Loehle's own reconstruction. That, of course, is probably the null set. If you want to see whether Loehle's MWP is warmer or cooler than the present, you need to re-center Loehle to match some other series that includes present-day temperatures. This is what we do in the update to the post (above).
  40. New temperature reconstruction vindicates ...
    Nice figure @ 50 Ned. It seems that now matter how you slice and dice the data (i.e., which baseline one uses), Loehle is the outlier. I agree the amplitude of anomalies the Loehle reconstruction are clearly too high for the excellent reason that you provided. If anything, going by that Figure @ 50, Ljungvist agrees best with Mann08, not Loehle08. WUWT should have a post saying that Mann08 has (yet again) been vindicated...not going to happen of course. Anyhow, IMHO, the important observation here is that current warm temperatures in the N. hemisphere are very likely to be unprecedented over the last 1500 years. Exactly how much is difficult to say, but I do not think that one can simply say "we can't be sure today's N. Hemisphere temperatures are warmer than those in the MWP". Zeke has demonstrated that current N. Hemi. temperatures are almost certainly warmer than those observed during the MWP, so has Tamino, apeescape, Ned and Alden......a nice coherent picture. The only incoherence that I can see is in the scrambling and weaseling going on by the "skeptics" and "lukewarmers".
  41. New temperature reconstruction vindicates ...
    OK, I've updated the post (see the "update" above). I particularly like the comparison of LIA and MWP in the various reconstructions, after recentering them all to match the instrumental record as closely as possible during the overlap period: Figure 4. Warmest decades of the Medieval Warm Period, and coolest decades of the Little Ice Age, after re-centering each reconstruction to match the instrumental temperature record during the period of overlap. Moberg is a bit on the cool side overall -- which might just mean it was anomalously warm during the calibration period used for centering. Mann and Ljungqvist agree very closely on the Medieval Warm Period, though Mann's Little Ice Age is not as cold. Loehle manages to be both too warm and too early on the Medieval Warm Period and on the cool side during the Little Ice Age. This difference would not be all that noteworthy, except for the fact that Loehle 2008 is supposed to be a global reconstruction ... and the magnitude of the MWP-LIA difference should almost certainly be smaller for a global reconstruction than for a Northern Hemisphere one. The other obvious point is that when we compare these to the current instrumental temperature record, the Medieval Warm Period seems to be about 0.7 degrees C cooler than the 2000-2010 mean temperature.
  42. Blog review of scientific coherence
    One the one had I like to call the gulliable belief in anything but AGW, the ABCers (anything but CO2). But to put a devils advocate hat on, it is possible to explore alternative ideas without endorsing them. There is a defence of being 'open minded'. It is even possible within science to have to remain open to contradicory ideas while the evidence is built up on which is right. But I think in the cases of the more prominent ABCer blogs this defence fails with the tabloidesque enthusism each idea is greeted with and the lack coherent narrative do weaken such a defence.
  43. Does Climate Change Really Matter?
    Another way of asking, "does climate change really matter?" Just another coincidence in the weather, surely. Graph from this article, which makes today's coverage of the Powell-Mead system in the NY Times look optimistic.
  44. A detailed look at the Little Ice Age
    As I understand it, Milankovitch forcing would strongly indicate that the past 300 years should have been the coolest period of the past 6000.
  45. The Phony War: Lies, Damn Lies and the IPCC
    "you're still missing the point that overall temperatures were lower than today." That is certainly not true for the Arctic or even the Northern Hemisphere, probably not true for the globe. Look at the noise in the whole Holocene ( plus or minus 1 degree C ). We haven't even exceeded that. And as I pointed out, the mean can be meaningless, as the seasonal variation was more extreme in the HCO. Extreme weather is caused by increased gradients. To the extent that CO2 forcing is significant, as modeled it should REDUCE gradients and thus REDUCE storminess. I don't think it's that significant. There have been weather disasters through out human history in 'warm periods' and 'cool periods'. http://www.disastercenter.com/disaster/TOP100K.html
  46. Is Greenland losing ice? (psst, the answer is yes, at an accelerating rate)
    Roger, Do you think that the gulf stream is the exact same thing as the AMOC?
  47. New temperature reconstruction vindicates ...
    Hi Ned, Thanks. That is what I understand reading this (I was trying not to "lead" you). But Loehle seems to be invoking the above quote as evidence that when done his way, his reconstruction is vindicated. Worse still, some are now using that quote above to suggest that people who are trying to realistically compare Loehle's reconstruction with Ljungqvist's are not being honest. But what the heck does one do when Loehle's poor methodology has made it almost impossible to properly compare his reconstruction with those from other paleo groups? IMO, people are nevertheless sincerely trying (despite all the hurdles). Besides why should we take Loehle's word for it? That is how scientists test/validate their colleagues work/hypotheses. Scientists "A" (Loehele) makes an assertion, and others then test said assertion. Well, going by the evidence submitted here and elsewhere Loehle's assertion/hypothesis fails horribly.
  48. Blog review of scientific coherence
    I like where you are going with this but as a non-scientist working to understand it all there is some phrasing that grates a little bit on these American ears. Part of it might be eased by using synonyms in a couple places for "coherence" and "incoherent". I would especially add a short synonymic phrase after this sentence to add emphasis. "Your kids’ future, and the future of their kids, very much depends on logical coherence"... And a suggestion for the last ..instead of "That" use This is the science knowledge that is coherent, backed by peer-reviewed science, and endorsed by all major scientific organizations in the world.
  49. Does Climate Change Really Matter?
    The present Tory UK Foreign Secretary delivers reasons why climate change matters, from a foreign policy perspective: I will first argue that an effective response to climate change underpins our security and prosperity. Second, our response should be to strive for a binding global deal, whatever the setbacks. And third, I will set out why effective deployment of foreign policy assets is crucial to mobilising the political will needed if we are to shape an effective response. To learn more about what a usefully functional conservative grounded in reality sounds like when confronted with facts, click the link.
  50. New temperature reconstruction vindicates ...
    Albatross, my take on that is that there's no direct and uniquely correct way to compare Loehle's reconstruction to anything else (other reconstructions, instrumental temperatures, anything). It's just centered on a value of 0. To compare it to anything else, you have to pick a period of time and assume that both Loehle and whatever-it-is should have the same mean during that period of time, then recenter Loehle's reconstruction to match that mean. Loehle chooses to assume that his reconstruction and Ljungqvist's have the same mean over the entire 2000-year period (I basically did the same in Fig. 2). Alden Griffith's very nice graphic here is based on the assumption that Loehle should have the same mean as the instrumental data during their period of overlap. Both of these are probably defensible choices but it's important to understand the differences. If you're most interested in comparison to the instrumental record, it's probably best to recenter Loehle's reconstruction to match that. Unfortunately, the period of overlap is only 80 years, since Loehle ends so early (1930s).

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