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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 126551 to 126600:

  1. Record high temperatures versus record lows
    Failing to look closely enough before my last comment regarding Pinatubo, I now notice that Pinatubo in Figure 2 didn't result in a large number of new lows. It just caused very few new highs (blue dot still a ways below expectation, red dot the lowest in the sequence).
  2. Record high temperatures versus record lows
    Another late night John! My father-in-law didn't believe in anthropogenic global warming, and we had a very animated and ineffective arguments about it. Now I'm told he has changed his mind! You might wonder, was it some new analysis or pedagogy or social attitude that got to him? Naw, it was hot where he lives last summer. I should tell him he's wrong to change his mind on that basis, but that probably won't do any good (we don't share any language in common, and I don't know how to mime the concept). I see Figure 1 and I first notice that the data appear to be distributed below the modeled expectation. Is there less stochasticity now (better measurements, for example), or is this just an artifact of the ln scale? Looks to be real to me. Also, is the number of stations constant throughout the study period? In Figure 2 there seems to be more interannual variation in later years (even excluding the obvious effect of Pinatubo). Perhaps when dealing with ratios, that's expected too, since it should be relatively easy to return to 1 or even less after a really hot year in the US. Or, hmmm, actually it would be interesting to remove the effect of Pinatubo from the trend, because that one cold year might really mute record cold temperatures going into the future. Sorry for the messy comment.
  3. High CO2 in the past, Part 2
    Actually, I think we are in agreement, as I have been using the coefficients calculated by Myhre et al (1998 and later papers) and used by the IPCC in 2001. Those are slightly lower that previously used figures. One possible explanation for Spencer's figure may be that he uses surface temperature instead of "effective temperature" for the calculation of his version of "Planck-lambda" to arrive at 0.18 instead of 0.27. But, in any case, he seems to be flatly wrong in asserting that it is not a controversial statement. And, as a climate scientist, is it possible not to know that.. For me, the most interesting about Royer's data is that the maximum basic net forcings hundreds of millions of years ago seem to be comparable to what we may be entering into now.
  4. Why is Greenland's ice loss accelerating?
    RSVP: to me it appears that you are trying to move your goalposts now. You initial post was obviously in regards to the globe and said nothing about the local temperature. I agree, it may have an impact on the local temperature (I would calculate the area of the sea around Greenland and compare it to the area of the whole ocean, but John Cook might make fun of my sums again ;-) ). However my main point was that no one is avoiding anything. Regards, John
  5. High CO2 in the past, Part 2
    Just a correction to the units in the last post: F of course is in W/m^2, and lambda in K/(W/m^2). Sorry for the typo!
  6. High CO2 in the past, Part 2
    Just a correction to the units in the last post: F of course is in W/m^2, and lambda in K/(W/m^2). Sorry for the typo!
  7. High CO2 in the past, Part 2
    I have a question about the basic CO2 forcing, as I would guess basic forcing may have been relatively more important as compared to the feedbacks at those high CO2 concentrations. As I have understood it, we have, as first order approximations and ignoring interactions, the two basic relations (C1 and C0 initial and final CO2 concentrations, respectively, 5.35 the coefficient used in IPCC AR3) forcing: F = 5.35 * ln(C1/C0) and temperature change: DT = lambda*F where lambda = 0.27 W(Km^-2)^-1. approx Giving about 1.1 degree K per doubling of CO2 as equilibrium effect of pure forcing. Is this the right way to do it? At CO2 concentrations of 5600 ppm, it would produce a (non-feedback) forcing of about 4.3 deg K, compared to recent pre-industrial levels, right? And, if it is, how, then can Roy Spencer write on his website (http://www.drroyspencer.com/global-warming-101/): "Now, you might be surprised to learn that the amount of warming directly caused by the extra CO2 is, by itself, relatively weak. It has been calculated theoretically that, if there are no other changes in the climate system, a doubling of the atmospheric CO2 concentration would cause less than 1 deg C of surface warming (about 1 deg. F). This is NOT a controversial statement…it is well understood by climate scientists. (As of 2008, we were about 40% to 45% of the way toward a doubling of atmospheric CO2.)" What have I (or, possibly, Roy Spencer) missed here?
    Response:

    The warming from doubling of CO2 is around 1.2°C (Lorius 1990) so you're not that far off. How does Roy Spencer arrive at "less than 1 deg C"? Unfortunately he doesn't cite how he arrives at that figure so I wouldn't know.

  8. Why is Greenland's ice loss accelerating?
    reply to John Cross Isnt it oversimplifying (and a bit unfair) to compare heat of ice melt in localized northern seas to that which is distributed throughout the entire planet's oceans? The energy can only cancel when these waters mix. This doesnt happen instantaneously, and less due to stratification. From any and all references Ive seen on the subject of Artic currents, if anything cold water seems to move outwardly away from poles. And these actually are changing over time as well. Ref example, "Arctic ocean currents shown to affect polar climate more than global warming" http://www.tgdaily.com/trendwatch-features/34866-arctic-ocean-currents-shown-to-affect-polar-climate-more-than-global-warming
  9. The albedo effect
    I have frequently asked the question as to where the 1.7 comes from, and did not get an answer. I read the IPCC report but did not get much the wiser other than to think (but I donot know) that it is a weighted figure. They look at the conc. of gases in 1750 and then do a weighting to 2005. Of course you can only do a weighting (=calculate proportional blame)if you are 100% sure what the cause is of a problem. If you donot have proof that CO2 is the problem (e.g. some stupid scientist like myself could not find it) you could be making a big mistake. At this stage I am not even sure if greenhouse gases are the cause of global warming.It seems to me no one did the right kind of testing. As to the integration problem: I was never any good at it, but should someone not have done a whole investigation into this and come up with a relationship that shows the net effect of the cooling and warming of CO2 at 0.01-.05%? The conc. is also important as relationships may change in certain concentration ranges. I think that is where ol Svante went into the mist. Also I think you cannot compare the radiation of the sun with earth, surely it cannot possibly on the same scale? Apart from the radiation trapped and reflected by CO2 we also sit with the problem that cooling may occur higher up the atmosphere (CO2 freezes at -40 degrees C I think?). Obviously where it freezes it must reflect a lot more sunshine. (compare water vapor with water droplets - I am sure the droplet reflect more sunshine.
    Response: The radiative forcing from CO2 is calculated using line-by-line models in two papers:

    Collins, W.D., et al., 2006: Radiative forcing by well-mixed greenhouse gases: Estimates from climate models in the IPCC AR4. J. Geophys. Res., 111, D14317, doi:10.1029/2005JD006713

    Forster, P.M.F., and K.E. Taylor, 2006: Climate forcings and climate sensitivities diagnosed from coupled climate model integrations. J. Clim., 19, 6181–6194.

    Of all the forcings considered to drive climate, CO2 forcing is one with a higher level of understanding. As for the evidence that CO2 is causing warming, this has been observationally confirmed both by satellites and surface measurements of downward longwave radiation.
  10. The albedo effect
    Henry, Integrate the incoming and outgoing radiation distributions for Earth over the actual absorption spectra and atmospheric concentrations, taking into account re-radiation etc. See what version of the radiation "discussion" is supported. Then compare with actual measurements, to see where consistencies and inconsistencies are to be found. It might also be illuminating for you to take a look at what the IPCC actually has to say, in scientific terms, when you are able to write such things as "the 1.7 assigned by IPCC to CO2 is from the idea: let us have a planet, let us add some CO2, see if the temp. goes up, it did, so that must be it." And the IPCC is of course open to new factors explaining the observed phenomena, if they can be rigourously established. But because we are always (Occam's razor) looking for the simplest models able to explain the phenomena, scientists may seem more arrogant towards new factors then they really are - it's just that is is the business of the proponents of new theories to furnish the evidence, not the opponents. This also makes science in a sense very conservative: When repeated attempts at falsifying a new theory fail, and it is both theoretically and observationally consistent with the existing body of knowledge, it will usually be incorporated in that body. Thereafter, it will be the business of opponents to point out errors, inconsistencies or wrong predictions. When you write "..the point is: you cannot go on the assumption that CO2 is the problem, because what else can it be? You have to provide me with scientific evidence," you seem to have overlooked these facts about how the scientific process works. The evidence is there, and the references cited on this blog is, I think, a great place to start. It's great if you can come up with even better explanations, but don't expect the proponents of an established theory to be very interested in working out your ideas, as long as they seem to work fruitfully within their paradigm.
  11. The albedo effect
    In the abstract it is explictly stated that they are comparing two nearby regions, one intact and the other after the fire. Other people made the observation that boreal forests reduces albedo and that cutting them down have a cooling effect. True, in the short term; and indeed the calculations in the extended abstract are done for one year only. But what is not considered in this kind of analysis is the time it takes to absorb again the emitted CO2. Indeed, in relatively few years, the regrowth of vegetation will bring the albedo back to the original value while the emitted CO2 will be in the air for many more years. If the forest was on average 100 years old it will take the same 100 years to bring the CO2 balance to equilibrium. In the meanwhile the excess CO2 will continue to have a warming effect and the older the forest the worst the impact.
  12. An overview of glacier trends
    "Honestly with a lag time of 4-36years you can fit just about any pattern to a data series which is less than 100 years" why does this sound familiar? Hmm, I know, because on an earlier thread a denialist was insisting that some mechanism involving the sun (decreasing in activity in recent years) was causing climate change because there was a time lag, using an analogy which seemed to involve hot plates and watched pots if I remember correctly. And yet here the whole concept of time lag, perfectly valid for glaciers whose form reflects a balance of losses and gains, is rejected out of hand by another denialist. Cherry picking, in denioworld, is not restricted just to data.
  13. The albedo effect
    Hi I'm looking for an explanation. I don't really get radiative forcing. Take this abstract on the nett radiative forcing effect of an Alaskan forest fire. The negative affect was 8 W/m2 while the positive affact was 21 W/m2. This seems a lot when "change of just 1% to the Earth's albedo has a radiative effect of 3.4 Wm-2" Is the abstract describing the nett radiative forcing for the area of the forest fire (7200hectares) while the 1% albedo figure is for the whole surface of the earth?
    Response: I haven't read the paper but I'm guessing the forest fire radiative forcing would be just for that region, not the whole globe. It would also be temporary. A global radiative forcing of 13 Wm-2 would be huge and have an immediate, sharp effect on global temperatures.

    The radiative forcing from a large volcanic eruption is quite large, particularly if it's located in the tropics so the aerosols from the eruption can spread through both hemispheres. For example, as discussed above, the global radiative forcing from Mt Pinutabo was  2.5 Wm-2. This is approximately equivalent to the radiative forcing of all human CO2 emissions since pre-industrial times. Global temperatures immediately responded to the negative forcing with global cooling happening. However, the effect was temporary - the aerosols washed out of the atmosphere and global temperatures bounced back after a few years.
  14. An overview of Greenland ice trends
    #28 Your right there was a lot of misunderstanding on my part. So from what you tell me the sparse historical data can tell us very little because it is only local relative sea level change. The potential for land movement means we can not rely on those measurements to tell us anything about absolute global sea level change. Then why continue to repeat the 1-10cm figure when it tells us nothing? Why not say we have no reliable measurable data before the 20th century. I now understand where you got the 50x figure from. I had misread the 21st for 20th. You didn't do what I asked and ignore the apocylyptic future. The point I was making with regard to the Grinsted graph was to do with the period upto the 20th century not into the future. This suggests that global sea levels were higher in the MWP than presently. Looking at the graph from Grinsted again there are areas of the graph at the run into the MWP were the slope (i.e. the rates of change of global sea level) looks very similar to the slope in the recent period. This rate slows up to the point that sea levels reach a peak. So there maybe periods in the MWP where rates of sea level change approached the rates of the last two decades. You suggest that sea level changes have been around 3.2mm/year for the past two decades with an average of 1.8mm/year for this century. Unless I misunderstand this, then that would mean a total of 18cm sea level rise for the 20th century? Back to Grinsted's graph. He shows about 30cm rise from 600AD to 1200AD. >40cm drop from 1200AD to 1700AD and then maybe >25cm rise from 1700AD to present. I'm unsure how you can square that with "The evidence simply doesn't support large variation in rates of global absolute eustatic sea level during the last 2000 years" when we are comparing that with the 18cm rise in the 20th century. (There is a little confusion for me in your quote above. Do you mean absolute changes or rate of changes?)
  15. An overview of glacier trends
    #21 This is from your #15 post "The dominant effect on mountain glacier recession/advance, polar ice sheet recession/advance and sea level rise and fall is temperature. This relationship is obvious to the extent that it’s possible to assign rather crude correlates of glacier advance/recession and historical temperature" I'm not sure whether the words crude and obvious should have been in the same sentance given the context but there is a suggestion in that remark that there was a correlate. Your points i) and iii) seem to suggest that local, specific factors may dominate individual glaciers. If you accept that then really you can't make any general points about glaciers whether the data is to support one arguement or another. I'm unsure what you mean in point ii) Honestly with a lag time of 4-36years you can fit just about any pattern to a data series which is less than 100years. How does lag work taking into account the often huge intra-seasonal variation in glaciers? Heres my crude understanding. This is a general scheme. Ice in glaciers can exist in areas where the air temperature will allow this. During the warming (summer) months the glacier retreats and in the cold winter months the ice can again flow further to regain some of the lost ground. Given that Fig5 in this Report suggests that intra-seasonal variation can be many multiples of the final nett annual change then how does lag work. In series of years with warming temperature how can glaciers ignore the warming weather to regrow each year and show no annual nett change. I can accept that for individual glaciers there may have specific local conditions that may allow deviation from a strong correlation of warmer air = retreating glaciers but its difficult to see how that occurs as a generalized phenomenon averaged of the global data (and this is what we are talking about). Your quote about European Alps in many ways sum up things for me. 1) An extreme summer of 2003 can be directly associated with 5-10% mass loss, where is the lag? 2) Many glaciers are responding quickly but conviniently some are taking upto 100 years to respond. 3) How do we every draw reliable averaged, global data when we continue to dismiss anything that doesn't fit into the theory with arguments ground local conditions. As a scientist I'd love to be able to dismiss the data that doesn't fit my theory it would make the whole process a lot easier.
  16. An overview of glacier trends
    #20 HR you're throwing out everything that we know about the phenomenon (glacier responses to forcings), and then trashing a simplistic caricature (your "simple relationhips"), which no one considers to be valid (i.e. that there should be a one-one contemporaneous correspondence between temperature variation and glacier response measurement). So in considering the relationship between glacier advance/retreat and global temperature, at least three relevant factors should be considered: (i) glacier response times to temperature change, (ii) the levels of volcanic aerosols to which glaciers are particularly sensitive and (iii) local geometric and climatic conditions that influence local glacier responses. Just considering glacier response times (since you tried to "head off" discussion of this rather obvious point!): Glacier recession will occur well after temperatures have levelled off from a warming phase, and recession can continue for a long time afterwards. This is because the glacier response is to the temperature difference from the previous "equilibrium", rather than to the temperature as it changes (see my post #15). Oerlemans recently estimated glacier length response times (which is somewhat similar to the time constant for an e-fold change for an exponential decay/rise), for several European glaciers, to be in the range between 4 years and 36 years (partly depending on the steepness of the glacial valley) [*] It's likely that the post 1940's glacial retreat that you mention was a continuing response to the warming to the 1940's, as the glaciers continued to respond to the temperature rise above the early 20th century temperature, even as the temperature rise stopped. Likewise, speaking of the European Alps, Solomina et al. (2007) [**] state:
    After a transitional time of modest gain since the 1960s, mass balances become strongly negative after about 1980. Most glacier tongues have started to react to this signal but are still far from a full dynamic response. Today – here in the sense of the year 2005 – tongues of medium-sized valley glaciers still reflect climatic conditions towards the end of the past century. In the meantime, average volume loss of Alpine glaciers has increased to about 2 to 3% per year. For a full geometric adjustment to the climatic conditions of 2000–2005, most glacier tongues and ice margins would require a farther retreat of a kilometer or more; and with repeated conditions of the extreme summer of 2003, most glaciers would disappear completely.
    "Simple relationships" do "begin to breakdown" if we pretend not to know what we know about them! [*] J. Oerlemans (2007) Estimating response times of Vadret da Morteratsch, Vadret da Palu¨, Briksdalsbreen and Nigardsbreen from their length records. Journal of Glaciology, Vol. 53, No. 182, 2007 [**] O. Solomina et al. (2008) Historical and Holocene glacier–climate variations: General concepts and overview. Global and Planetary Change 60, 1-9
  17. Why is Greenland's ice loss accelerating?
    The Labrador sea, for example, is warming. We can safely conclude that the influx of cold water from the extra melting of the Greenland ice sheet is not the dominant effect. It should be expected, indeed. The Labrador sea is pretty cold and adding water only a little colder does not change much. Also, it should be compared to the concomitant melting of the winter ice of the whole region; it's just a tiny fraction. Need to put "significant melting" into context. What is true is that it's not included in any of the current GCM models, given that to my knowledge none of them predicted this fast melting. What matters, instead, is the different salinity which is the driver of deep circulation. Very much like the whole arctic ocean, the Labrador sea is more salinity stratified than temperature stratified, being the temperature gradient small.
  18. Why is Greenland's ice loss accelerating?
    A more often put forward idea is that freshwater from the melted ice sits on top of the ocean water, stratifying it more, and it refreezes more readily. This may also be a bit of a negative feedback mechanism. Where did I read about it? http://www.skepticalscience.com/Why-is-Antarctic-sea-ice-increasing.html RSVP, I think the "gloomandoomer" comment was uncalled for.
    Response: Note that the stratification in the Southern Ocean may be unique to the region. When first researching increasing Antarctic sea ice, I encountered Zhang 2007 who explained that the warming Southern Ocean paradoxically could lead to less warm water upwelling to melt sea ice. I wondered why a similar effect didn't occur with Arctic sea ice which is sharply falling and contacted the author about it. He informed me that the stratification of water in the Arctic is different to the Antarctic, hence sea ice reacts in a different way to warming waters.

    Agreed re RSVP's comment - I would've deleted it due to the unconstructive tone but there were several interesting comments posted in response which I didn't want to waste (John Cross went to so much effort with his sums) :-)
  19. Why is Greenland's ice loss accelerating?
    3# "Going to a previous post by John we see that the increase in heat content of the ocean is about 18*10^(21) J/year." Yes, but not all round Greenland, whereas the ice melt is.
  20. Why is Greenland's ice loss accelerating?
    RSVP: looking at the Ice Mass Loss graph above and doing some quick calculations I get an average of about 222 Gt a year of ice loss over the past few years (when loss is the most). If you don't mind my long hand math, this works out to 222,000,000,000 tonnes per year of ice melted. Now, the latent heat of fusion of ice is about 334 J/gram or (again I apologize for the notation) 334,000 J/kg = 334,000,000 J/ton. we multiply this by our ice loss from above and get an annual heat required to melt the ice of 222,000,000,000*334,000,000=74*10^(18) J. Going to a previous post by John we see that the increase in heat content of the ocean is about 18*10^(21) J/year. Looking at the ratio it requires about 1/250 of the heat accumulating in the oceans to melt the ice. Nothing more than a drop in the bucket ;) Regards, John
  21. Why is Greenland's ice loss accelerating?
    With all that has been said about how much ice is melting, I have not seen any mention of how this might cool the oceans. If the volume of ice is so significant, the energy absorption it brings with it should also have some impact (at least in the short term), and thus to some degree provide a cooling feedback mechanism. I can understand how this topic might be avoided as it would not help gloomanddoomer positions.
  22. Skeptical Science housekeeping: Comments Policy
    How do you set up hyperlinks?
    Response: A HTML hyperlink is set up like this:

    <a href="http://www.website.com/">Hyperlink Text</a>
  23. The albedo effect
    1) you just don't want to understand. the atmospheric absorption bands (that shows the difference between the radiation measured on top of the atmosphere and the radiation that is measured at sea level) clearly shows you that oxygen/ozone and water vapor and carbon dioxide cause reflection of light (back to outer space!). 2) it is not I that is confused about what happens when a few photons are absorbed by the molecule. I notice you did not answer the question I raised on 127! Light has to keep moving. "absorption" is the word that confuses people because they donot understand that once the max. amount of photons are absorbed, the molecule becomes like a mirror at that wavelength band where it absorbs and has to reflect the light back in the band where is absorbs. The position of the molecule is random so you can expect at least 50% of the light in that wavelength band to be sent back to space. I am asking: what is the net effect of the cooling and warming properties of CO2 especially in the CO2 range of 0.01 -0.05%. Where are the test results? the 1.7 assigned by IPCC to CO2 is from the idea: let us have a planet, let us add some CO2, see if the temp. goes up, it did, so that must be it. And some viking who lived 100 years ago and whose calculations have been proven wrong. If he was right, earth should have been a lot warmer. There is no proof that CO2 causes warming. 3) Plimer might be right. Most volcanic activity takes place underneath the seabeds. CO2 comes from volcanic activities (which also produces heat to the water). the point is: you cannot go on the assumption that CO2 is the problem, because what else can it be? You have to provide me with scientific evidence. 4) one day you will find out you are wrong...
  24. An overview of glacier trends
    Steve "HR, it seems to me like you're trying to say that recent/current mass loss in alpine glaciers is a continuation of a prior process." I'm certainly saying that is a possibility. Lets split the past century up into sections based on global mean temperature change and glacier retreat. 1920s stable glaciers 1940s strong retreat 1970s stable glaciers 1980s onwards strong retreat 1915-1935 rising temperatures 1935-1975 steady temperatures 1975-1995 rising temperatures how can you directly relate these two processes? In the 1940s glaciers were retreating right in the middle of a period of stable global mean temperatures while glaciers were stable in the 1920s during a period of global rising tamperatures. Before anybody says there is a delay in the glacier reaction to global mean temperatures the state of glacier retreat nicely coincides with changes in mean global temperature from 1970s onwards. Something I guess John and Chris have been pushing. I just think that once one goes back in time past the 1970s simple relationships begin to breakdown.
  25. An overview of glacier trends
    HR, it seems to me like you're trying to say that recent/current mass loss in alpine glaciers is a continuation of a prior process. That's an analog of this argument: http://skepticalscience.com/coming-out-of-ice-age.htm but I think this argument is even worse when applied to alpine glaciers.
  26. An overview of glacier trends
    Mmmmm. See what I can do John!
  27. An overview of glacier trends
    #14 response So your presentation is "The answer to that is relatively simple - some are growing, most are shrinking, the overall trend is accelerated shrinking." An alternative way to present the recent history of glaciers would be " Evidence of general glacier retreat since the 1700's. detailed data for the last century identifying period when this retreat has been quicker (1940s and 1980 onwards) and other times when the retreat has slowed or even reversed (1920s and 1970s)" Both would be generally correct for the data available but the first would emphasise the past few decades as something standout (accelarated shrink) with the inherent implication that AGW is involved while the second version paints a picture of general, variable natural retreat of several centuries. Further on the accelarated shrinking. Just from eyeballing the Zemp graphes you present the slope of the graph between 1945-1955 and 1995-2005 look to be very similar so rather than accelerating shrinkage one could argue that glacier retreat has returned to its previous rate before the pause associated with the 1970s. This is not just semantics but important in shaping how we respond to the data. I'm interested in the Zemp macro-region data unfortunately I can't get free access to that paper. I think it would be interesting to see if glaciers in different macro-regions show generally similarly or different patterns of retreat/pause/advance of the last century. Presenting the mean of the regions obscures that. The reason I say that is because the WGMS (http://www.grid.unep.ch/glaciers/) does attempt to breakdown the data into regions. The NZ data (6.3) presents front variation on 12 glaciers for 2000-2005 which shows no nett retreat in these 12 glaciers. While some of the graphs you present in your article suggest this is a time of global retreat. Just on #16 It is not just advancing glaciers that can or need to be explained by local conditions. Take for example Kilimanjaro the following paper suggests glacier retreat here is down to changes in humidity/precipitation not air temperature http://www3.interscience.wiley.com/journal/107630666/abstract?CRETRY=1&SRETRY=0
  28. The albedo effect
    Henry, your #1 is about measurements from a single night and in no way supports your assertion that "those studying albedo have identified CO2 as one of the ingredients as to why Albedo has increased". Your #2 is about your "gut-feeling", some confusion between reflection and absorption I think, and ignoring visible light being turned into infra-red after it hits the Earth. I don't have to do the actual testing -- it has been done and is integrated into the IPCC's forcing chart (see here, for example: http://skepticalscience.com/CO2-is-not-the-only-driver-of-climate.html ). If you disagree with the IPCC's summary of the science, I think it's up to you to show why. You'll need to do more than assess what your gut thinks. #3. Plimer is wrong. Your comment Nov 13 there is just repitition of what you've said, except you cite WUWT. #4. Measurements contradict your assertions. Sorry Henry, but I don't think our discussion is going anywhere.
  29. The albedo effect
    Henry Pool, i'm not going to open again the discussion on the presumed "reflectivity" effect of CO2, but the first reference you quote has nothing to do with it. Indeed, the very same sentence you copied here refer to the absorption properties of CO2 in the IR, hardly a breaking news.
  30. An overview of glacier trends
    John it occurs to me, looking at the interesting graphic at #6 that you could do an interesting look at why certain glaciers are bucking the trend. Franz-Josef is the obvious one, but in the graphic there seem to be several others. An eyeball suggests that these were all dropping but around 1980 turned around. My guess would be that these actually provide further evidence of the effect of global warming on glaciers. Looks as if they lose ice as temperatures slowly rise, but then about 1980 this effect is overtaken by the effects of warming seas giving more precipitation of snow, and then the warmer it gets the bigger they get.
    Response: David, that's an excellent idea. It would require tracking down studies examining each of the growing glaciers. I'm not sure I have the time to do it myself as I have a specific list of topics I need to get through at the moment. But if you're interested in tracking down the papers, I'd be happy to host a guest blog post from you :-)
  31. The albedo effect
    Steve, to answer your questions: 1) The Astrophysical Journal, 629:1175–1182, 2005 August 20: quote from abstract: Water vapor and molecular oxygen signals in the visible earthshine, and carbon dioxide and methane in the near-infrared, are more likely to be powerful probes. 2) You can study carefully the sun's solar radiation spectrum and the earth's upgoing radiation spectrum and the atmospheric absorption bands. Put them on top of each other. It will show you that ozone reflects a lot of the sun's radiation where the area below the sun's curve is the biggest. Nevertheless, ozone also traps some radiation of earth at exactly 10 um. My gut feeling from these graphs is that the net effect of ozone is cooling. So the more ozone, the cooler it will get. The same argument goes for CO2 although here my feeling is that it is pretty much evens. There is reflection at 1.4, 1.8; 2.3 um and even at 4 (because the sun is still emitting there). Recent discoveries also show that CO2 absorbs in the UV. Some entrapment of earth radiation of CO2 can be seen at 14 um but water also absorbs here. I think you cannot really say for sure what the net effect is of the cooling and warming properties unless unless you have done some actual testing 3) http://www.telegraph.co.uk/earth/earthnews/6553592/Climate-change-sceptic-Ian-Plimer-argues-CO2-is-not-causing-global-warming.html
  32. Why is Greenland's ice loss accelerating?
    Greenland's climate is strongly influenced by the NAO; during periods when this is positive, Greenland and Canada experience colder winters but the N America east coast has milder winters. Conversely, when NAO is negative, Greenland has milder winters and eastern US colder ones. Europe and the mediterranean climates are also affected. The graph at http://www.cpc.noaa.gov/products/precip/CWlink/pna/nao.timeseries.gif (covering 1950 - 2009) shows more negative phases 1950-1971/2, more positive phases from 1971/2 to 1995 , more positive 1995-2005 and more negative 1995- 2009. Eyeballing the graph it appears the phase change is increasing in frequency and intensity. Since 2005 the NAO has been mostly, and strongly, negative, thus giving Greenland milder ( relatively!!) winters with increased precipitation. As the NAO is driven by permanent pressure differential between the Azores HP zone and the Icelandic LP zone, I would expect that differential to increase as the tropics warm in advance of the higher latitudes, so favouring negative phases, thereby accelerating ice loss at the margins.
  33. An overview of glacier trends
    re #9; The dominant effect on mountain glacier recession/advance, polar ice sheet recession/advance and sea level rise and fall is temperature. This relationship is obvious to the extent that it’s possible to assign rather crude correlates of glacier advance/recession and historical temperature (i.e. using global glacier records as a crude thermometer for global temperature change) [*], and between global temperature change and sea level rise [**]. In relation to the ice/sea level response to temperature, it’s not so much the rate of change that’s important as the degree of temperature rise above the temperature where ice sheet/sea levels have roughly come to equilibrium [**]. It’s temperature change that dominates ice and sea level change. So considering glacier recession since the depths of the Little Ice Age around AD 1600-1700), we aren’t surprised that this is associated with a temperature rise to the pre LIA temperature by the mid-late 18th century, followed by a further warming that accelerated in the 20th century [e.g. see Moberg et al (2005) which is the Northern hemisphere temperature reconstruction that is often used as a (possibly extreme) measure of temperature change during the last 2000 years; this can be freely downloaded: http://coast.gkss.de/staff/storch/pdf/moberg.nature.0502.pdf So the question is what are the dominant influences on temperature rise since the LIA (say to the middle of the 20th century where temperatures might be around 0.6 oC warmer than the bottom of the LIA according to Moberg’s reconstruction, and remembering that this is a NH reconstruction)? A number of analyses of the solar records, indicate that the temperature contribution to the LIA was around 0.1 oC of cooling relative to the mi-20th century (e.g. [***]). Likewise analysis of the record of volcanic activity indicates that this was likely causal for some of the low temperatures during the LIA (say another 0.1 oC). So some of the temperature change from the bottom of the LIA to mid-20th century, that obviously influenced land ice recession and sea level rise was a recovery from negative (solar and volcanic) forcing. The anthropogenic component was rather significant too, since it produced a rise in atmospheric CO2 from 280 ppm at the end of the 18th century to 300 ppm by 1900, and 310 ppm by 1940. It’s easy to calculate using the mid-range of climate sensitivities of 3 oC of warming per doubling of atmospheric CO2, that the equilibrium temperature response from this raised [CO2] is 0.3 and 0.44 oC of warming, respectively. Since the pre-20th century anthropogenic CO2 increase was slow, the earth temperature response likely came close to equilibrium with the forcing, and we might have expected to have realised 0.3 - 0.35 oC of warming associated with the anthropogenic forcing by the mid-20th century. In other words, considering the temperature rise due to fairly established forcings, a considerable amount of the pre 20th century glacier recession, polar ice sheet recession and sea level rise since the LIA is likely anthropogenic. It’s often not realized that there was a very significant anthropogenic component to global warming pre-20th century… [*] J. Oerlemans (2005) Extracting a Climate Signal from 169 Glacier Records Science 308, 675 – 677 http://www.sciencemag.org/cgi/content/abstract/308/5722/675 [**] S. Rahmstorf (2007) A Semi-Empirical Approach to Projecting Future Sea-Level Rise Science, 315, 368 – 370 http://www.sciencemag.org/cgi/content/abstract/1135456 [***] Y.M. Wang et al. (2005) Modeling the sun's magnetic field and irradiance since 1713. Astrophys. J. 625, 522-528. http://sun.stanford.edu/LWS_Dynamo_2009/61797.web.pdf (not the most accessible paper in the world!)
  34. The albedo effect
    Henry: "those studying albedo have identified CO2 as one of the ingredients as to why Albedo has increased". Citations please. "I am sure the balance is that ozone reflects more radiation than what it traps from earth." Why are you sure? Citations please. Other facts (regarding wavelengths detected at the surface and in space) contradict your assertions about albedo. We won't get very far if you ignore them. The link you provided to the Telegraph (of all places) did not work.
  35. The albedo effect
    This post is about albedo, not CO2. I am not sure if we can carry on with this here. Dear Steve, the problem is that nobody did the right kind of tests. We know where CO2 absorbs and those studying Albedo have identified CO2 as one of the ingredients as to why Albedo has increased. We even know that CO2 absorbs in the uv range (thus also reflect UV light). With these particular wavelengths they can see if there is CO2 on other planets. It does not matter in what wavelengths the light is reflected because if it does not land on earth than surely it cannot bounce back in the IR range, i.e. it cannot cause warming. To say that we need less CO2 is perhaps just as non-sensical as to say that we need less ozone.Ozone also traps earth radiation. Luckily for us, ozone is now increasing. I am sure the balance is that ozone reflects more radiation than what it traps from earth. The argument with CO2 is likewise, unless you have done the relevant testing that would show me that the warming effect is greater than the cooling effect.
  36. An overview of Greenland ice trends
    re #24,27 It's worth looking at Box et al (2009) [*] since these authors make a more detailed analysis of Greenland temperatures during the 20th century. Greenland warmed very significantly between 1919 and 1930 to an extent that has been larger than the 1990-present warming. The dominant influence (according to Box et al) is the effect of cooling sulphate aerosols from volcanic activity, to which Greenland is very sensitive. So the high degree of volcanic activity especially from the mid-late 19th century into the early 20th century suppressed Greenland temperature more that the global response. When this volcanic activity ceased, Greenland temperatures recovered rapidly and the suppresed anthropogenic and solar forcing was unleashed very quickly in the 1920's. A similar degree of suppression of Greenland warming occured due to the relatively high volcanic activity in the 1960's through 1980's. When this calmed down, Greenland warmed up to recover the warming represented in the rest of the world. In fact Box et al consider that Greenland warming has quite a bit to go (1 - 1.6 oC) to "catch up" with globaal scale warming.
    Over the 1840–2007 time span, two multidecadal low temperature periods (1861–1919 and 1963–84) in Greenland coincide with periods of multiple major volcanic eruptions. Greenland is most sensitive to volcanic (sulfate) cooling during the dynamically active winter season and along the western ice sheet margin, that is, when the equator-to-pole temperature differential is strongest and owing to the ice sheet topographic and baroclinic effect of planetary wave anchoring, respectively. Considering also that Northern Hemispheric cooling in 1940–70 is attributable to the ‘‘global dimming’’ effect of increasing sulfate aerosols, the sulfate cooling effect is, again, felt more strongly in Greenland, and indirectly via altered atmospheric dynamics not via local radiation budget modification.
    and
    In the early twentieth-century warming, Greenland anomalies surpassed the Northern Hemisphere anomalies in 1923, with close phase agreement between the two time series. In contrast, recent (1994–2007) regional warming around Greenland has not surpassed the hemispheric anomaly. Using the empirical relationships between Greenland and the Northern Hemisphere surface air temperature data, we calculate that if Greenland was to become in phase with the hemispheric pattern, as it did after 1923, an additional 1.08–1.68C warming would occur. In light of this prediction and global climate model forecasts for continued high-latitude warming, the ice sheet mass budget deficit is likely to continue to grow in the coming decades.
    [*] J. E. Box et al (2009) Greenland Ice Sheet Surface Air Temperature Variability: 1840–2007 J. Climate 22, 4029-4049
  37. An overview of Greenland ice trends
    re #23 You’re misunderstanding Milne et al again HumanityRules: (i)(a): The data you’re discussing from Milne et al is local, relative sea level change. Milne et al indicate that even taking into account the changes from postglacial isostsatic effects and land subsidence/uplift etc, that local relative sea level changes have been small during the few millennia before the industrial period, generally between 1-10 cm per century. The maximum local, relative sea level rates might be 20 cm per century, and perhaps larger as a consequence of major land slip or rise e.g. following large tectonic events like the one that resulted in the tsunami of a few yeas ago. But these are local, relative sea level changes that incorporate isostatic and vertical land motion effects as well as any eustatic absolute global sea level changes. It could hardly be clearer, since Milne et al say as much! Obviously if we’re interested in comparing anthropogenic warming induced contributions to sea level rise to that in the past we should consider the absolute global sea level change. We can look at that in point (ii) below. (i)(b) You’ve also misunderstood the long quote that you cut and pasted from Milne et al. This refers to an attempt during the past few years (when GRACE satellite measures have been available to estimate ice sheet mass loss), to partition the ~3.2 mm/yr sea level rise to its mass (land ice melt) and steric (warmth) components. There isn’t much uncertainty about the overall trend in sea level rise (~3.2 mm/yr) over the last decade or two (see: http://www.skepticalscience.com/Are-sea-levels-rising.html); a different uncertainty is being discussed in the bit of Milne et al. you cut and pasted. This results from uncertainties in “closing the budget”, whereby the GRACE altimetry-determined mass contributions and enhanced ocean heat steric contribution should sum to the observed sea level rise. This has been subject to confusion resulting especially from errors in ocean heat measures, but these seem to have been largely resolved very recently. So the evidence is quite strong that current absolute global eustatic sea levels are increasing around 3.2 mm/yr now. The paper on the site you liked to earlier indicates that the absolute global eustatic 20th century sea level rise was around 1.8 mm/yr overall (almost 80% of which was anthropogenic) [*]. So the rate of sea level rise is increasing and will continue to do so as temperatures continue to increase. That seems very straightforward. (ii) The evidence simply doesn't support large variation in rates of global absolute eustatic sea level during the last 2000 years (see papers/reviews cited in my post #2). You've shown us an analysis of sea level variation during the last 2000 years [**] that is quite consistent with the observations from paleoanalysis of eustatic sea levels. This paper indicates that the rate of sea level rise in the 21st century may well be around 1 metre/century, a rate that is broadly consistent with independent analysis (see Pfeffer et al (2008), cited in my post #22). The graph you showed us indicates that the warming during the very slow temperature rise into the MWP was around 2 cm/century. In otherwards, the graph that you brought to our attention indicates that the 21st century sea level rise might be around 50-times faster than the rate of warming to the MWP, the warmest period of the last 2000 years before the mid-20th century. You suggest now that you don’t like the paper. Specifically you suggest with respect to temperature-induced ice melt and sea level rise that “there are other processes which cause short term speeding up and slowing down of the ice melt”. But what might these be? Long lived temperature change is by far the dominant contribution to changes in sea level. It’s valid to consider this in relation to independent evidence for long term changes in temperature. In fact Grinsted et al use the rather extreme paloetemperature profile of Moberg et al [***] to determine their sea level changes. The temperature change to the MWP was very slow and long term, and the sea level rise was not-surprisingly likely similarly slow and long term. Now we're having a very rapid rise in temperature, that is taking global temperatures to levels already well above those of the MWP. So land ice is melting more quickly, the oceans a re warming more quickly, and sea levels are rising more quickly. [*] Jevrejeva, S et al (2009) Anthropogenic forcing dominates sea level rise since 1850. Geophys. Res. Lett., doi:10.1029/2009GL040216, in press. [**] A. Grinsted et al. (2009) Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD Climate Dynamics; in press. [***] Moberg A et al.(2005) Highly variable northern hemisphere temperatures reconstructed from low-and high-resolution proxy data. Nature 433, 613–617
  38. An overview of glacier trends
    #13 Accepted but the 'global' data set admits there is a "strong bias" towards the northern hemisphere. From the summary page of http://www.grid.unep.ch/glaciers/ from where this article takes some of it's data. "The moraines formed towards the end of the Little Ice Age, between the 17th and the second half of the 19th century, are prominent features of the landscape, and mark Holocene glacier maximum extents in many mountain ranges around the globe. From these positions, glaciers worldwide have been shrinking significantly, with strong glacier retreats in the 1940s, stable or growing conditions around the 1920s and 1970s, and again increasing rates of ice loss since the mid 1980s. However, on a time scale of decades, glaciers in various mountain ranges have shown intermittent re-advances. When looking at individual fluctuation series, one finds a high rate of variability and sometimes widely contrasting behaviour of neighbouring ice bodies." It may well be coincidence that the shift in the PDO occured in the 1920s and 1970s around the same time the glacier retreat slowed/stopped/reversed. But also maybe significant. I see the obvious truth in warmer world = melting ice but that may not be the whole story. And finally while it is not always stated directly that this is about AGW the implication is there otherwise we are wasting our time here and this is only an issue for glaciologists(?) to argue over.
    Response: Through trial and error on this website, I find it more productive to take baby steps rather than try and bite off more than I can chew. Eg - rather than try to answer the entire AGW question in one go (although I did have a crack at that once), I address specific points that skeptics bring up. Eg - "glaciers are growing". The answer to that is relatively simple - some are growing, most are shrinking, the overall trend is accelerated shrinking. We then take the next step, combining glacier's relatively quick response to climate and glacier equilibrium in the 1960s, to deduce that post-1970s warming is causing the recent acceleration in glacier shrinkage. As to the next step of what is causing the warming, the gorilla in the room if you will, that is addressed elsewhere.

    However, you also mention that the database of glaciers is heavily biased towards the Northern Hemisphere which is quite true. In fact, I've been waiting for someone to bring that up. Zemp 2009 goes into much detail about the geographical distribution of the glacier data and ways to account for this.

    The figure below is from Zemp 2009 and demonstrates various ways to estimate global glacier mass change. The solid black line is the average mass change of the 30 reference glaciers. The dashed line is the average mass change of all glaciers and the dashed-dotted line is all glaciers excluding the reference glaciers. There is also the consideration that the observed glaciers are located in the Northern Hemisphere and tend to be clustered in Europe. So another method to determine the global mean is to calculate average mass changes over macro-regions (thick grey line) or area-weighted averages of the macro-regions (thin grey line).



    My first draft of this glacier overview included this graph and that mouthful of an explanation above of the 5 different time series. I agonised over it for a while but decided in the end to go for the easier to understand (and yes, more colourful) Figure 3 above (from WGMS 2008). But I spent a lot of time in Zemp 2009 so you've given me the opportunity to dredge up all that work for which I'm thankful. :-)
  39. An overview of Greenland ice trends
    Riccardo: I think Chylek was referring to the warming of Greenland rather than warming in a global sense, although this is not specifically stated, I infer it from the fact that it is all one sentence. Also ( as John keeps telling us) climate is not about seasonal variations but long term trends, so those graphs are relevent. Only 2 out of the 6 graphs show coastal temps ever rising above 0C (for the periods covered). There is a distinct T rise 1920 -1940 followed by a cooling period and then another warming from 1990 on. But the average T is still below 0C. Box (SURVEY OF GREENLAND INSTRUMENTAL TEMPERATURE RECORDS:1873–2001)does a more detailed survey and notes the large effect of NAO, vulcanic activity and sea ice extent "Temporal and spatial variability are analysed in Greenland instrumental temperature records from 24 coastal and three ice sheet locations. Trends over the longest period available, 1873–2001, at Ilulissat/ Jakobshavn indicate statistically significant warming in all seasons: 5 °C in winter. Trends over the 1901–2000 century in southern Greenland indicate statistically significant spring and summer cooling. General periods of warming occurred from 1885 to 1947 and 1984 to 2001, and cooling occurred from 1955 to 1984. The standard period 1961–90 was marked by 1–2 °C statistically significant cooling. In contrast to Northern Hemisphere mean temperatures, the 1990s do not contain the warmest years on record in Greenland. The warmest years in Greenland were 1932, 1947, 1960, and 1941. The coldest years were 1918, 1984, 1993, and 1972, several of which coincide with major volcanic eruptions. Over 1991–2000, statistically significant 2–4 °C warming was observed in western Greenland, 1.1 °C warming at the ice sheet summit (3200 m), although this is statistically insignificant. Annual temperature trends are dominated by winter variability. Much of the observed variability is shown to be linked with the North Atlantic oscillation (NAO), sea ice extent, and volcanism. The correlation of coastal temperature anomalies with the NAO is statistically significant, in autumn and winter at western and southern sites. Warming from 1873 to 1930 and subsequent cooling persists after the removal of the NAO signal. Temperature trends are often opposite between west and east Greenland. This apparent teleconnection is spurious, however, given insignificant east–west correlation values. Frequency peaks correspond with periods of 3.7, 14.3, 9.1, 5.5–6.0, 11.1, and 7.1 years in both temperature and NAO"
  40. An overview of glacier trends
    HumanityRules, my impression is that you are mixing an aspect of local (although large scale) climate variability with a global trend. As stated explicitly by John Cook, glaciers respond do temperature, whatever the cause of the temperature increase might be. So the global retreat of glaciers is just a sign of global warming as opposed to _anthropogenic_ global warming.
  41. An overview of glacier trends
    In fact it looks as though deglaciation rates (certainly in northern hemisphere) change with PDO cycle more than increased CO2 caused warming. http://climate.gi.alaska.edu/ClimTrends/Change/TempChange.html http://jisao.washington.edu/pdo/
  42. An overview of glacier trends
    I'm going to keep at this. i looked for papers that had cited Greene's work. Only 2 came up, an important measure of the importance other scientists put on his work. Here's one of them Changes of Glaciers and Climate in Northwestern North America during the Late Twentieth Century Anthony Arendt John Walsh William Harrison Journal of Climate Volume 22, Issue 15 (August 2009) His general conclusions are a general increasing rate of mass loss from glaciers since the 1970's. But as you (really I) say the 1960-1970s represent a pause in the deglaciation process so any measurement afterwards is really likely to see an increasing rate of retreat. He makes this point "a warm period occurred between about 1920 and 1940 that would have put the glaciers in a state of negative balance prior to the 1950". Some data in those old papers I linked to suggested this as well. Why not do a comparison of rates in 1920-40 with 1970-2010. Identifying a rapid increase from a time when things are in stasis doesn't necessarily tell us much. And seems destined only to confirm an already held theory. Some further quote from this paper. "Additional complications arise when considering the fact that glaciers, because they have a delayed response to climate, may be changing due to climatic events that occurred prior to the measurement period" I guess the pause in the 1970s can't wholly be explained by the brief cold snap in the 1970s if this is the case. Just as a extra I'm puzzled by this quote which is discussing temperature records for Alaska based on weather station data. "Most of the change in temperature was attributed to a large temperature increase that occurred in 1976. Examination of the periods before and after this climate shift show that average annual temperatures decreased by 0.72°C during 1949–75 and increased by 0.3°C during 1977–2005." Given that the overall temperature change for 1949-2005 is ~2.5oC that means there was a sudden shift of >2oC in 1976 in average annual temp. that has remained ever since. It just seems fairly bizarre to me if irrelevant.
  43. An overview of glacier trends
    Sorry webmaster the outlandish claims wasn't directed at you more the publishers of papers. I've noticed a tendancy in this field at this present time for authors to add comment to their data usually giving it more media appeal. But I guess they have the to speculate on their data. I have no problem with what's written on this website. I guess the point is to stress there was a process of deglaciation going back to before industrialization which maybe continuing today. The 1960s-1970's information you present is informative. I take your presentation is similar to the original authors. He see equilibrium in 1960-1970s followed by retreat which must be global warming, I guess the real point being AGW. Whereas looking at a longer series of data might only see a pause in a much longer process of deglaciation. The data doesn't change but the distinction in terms of the impact on our thinking is important. "CO2 is imposing an energy imbalance on climate now. The CO2 radiative forcing is well understood and observationally measured. So citing past climate change is actually citing evidence for our climate's sensitivity to CO2." ....or other factors that affect deglaciation/temp/climate.
    Response: I appreciate your response. It's not like you hurt my feelings or anything (I cop a lot worse, believe me). I would just prefer, in the interest of conducting respectful, constructive discussion, that we refrain from such characterizations, whether talking about me, climate scientists or skeptics.

    In regard to the notion that current glacier shrinkage is part of the continued deglaciation since the Little Ice Age (or further, from the Last Glacial Maximum), I gleaned several points when researching on glaciers:
    1. Zemp 2009 looks at how glacier mass balance is a direct and undelayed response to atmospheric conditions. It reacts to climate change relatively quickly.
    2. Keeping that in mind, Greene 2005 notes that as glaciers were in near equilbrium from 1960 to 1970, glacier shrinkage in the late 20th Century is essentially a response to post-1970 global warming
    3. The trend in glacier mass balance is not a gradual return to equilibrium as part of a long term deglaciation. Glacier shrinkage been accelerating over the past few decades.

    "past climate change is actually citing evidence for our climate's sensitivity to CO2... or other factors that affect deglaciation/temp/climate"

    You're correct. Any radiative forcing will affect global temperatures and hence glacier mass balance. Every climate scientist will tell you CO2 is not the only driver of climate. But the reason for the focus on CO2 is because CO2 is the most dominant radiative forcing and it's also increasing faster than any other forcing.
  44. An overview of glacier trends
    I hate to keep repeating myself but how does this all fit into historical data. If glaciers have generally been receding since before the industrial age then how should we interpret the recent data. Some early pioneers in the field, papers taken from the WGMS literature section. http://iahs.info/redbooks/a039/039053.pdf looked at 12 glaciers in the Canadian Rookies and found all had been receding from before 19th century. What about this delicious paper on American glaciers http://iahs.info/redbooks/a039/039056.pdf which includes the following quote "It's [the paper's] primary purpose is to aquaint the listener (reader) with the factual data that has been obtained for the several glaciers mentioned rather than to make interpretation thereof". Imagine a publication that just presents the facts and doesn't attempt outlandish claims, wow. Anyway they find Nisqually glacier retreating from when records began (1857) and 4 other again receding from when records began (1920s-1930s). Only one (Coleman Glacier) was advancing and the report is accompanied by this comment "This, as far as known, is the only glacier where factual data are actually available to show that a terminal advance is in progress". Interesting that advancing glacier where rare back in the 1950's. A further paper put the maxima point for the Nisqually glacier at around 1750 http://www.wgms.ch/downloads/Harrison_RB039_1954.pdf. I see the table above suggests this glacier is now advancing. How about this gentle paper fron the 1940's on Columbian glaciers http://iahs.info/redbooks/a030/03040.pdf. More deglaciation. Steve L you may get your comparative photos from the likes of this guy. Or this report in the 1940's of "dying glaciers" http://iahs.info/redbooks/a030/03037.pdf Or this from 1940s that show mainly receding Alaskan glaciers http://iahs.info/redbooks/a030/03038.pdf. Or these receding Peruvian glaciers in the 1940's http://iahs.info/redbooks/a030/03039.pdf How about this paper which suggest Norwegian glaciers have been retreating for 200 years http://iahs.info/redbooks/a030/03042.pdf Or this paper that puts the start of the retreat in European glaciers in the 1700's http://iahs.info/redbooks/a030/03043.pdf Maybe I could go on and on. Anybody interested could keep looking at pdfs from that website, just keep changing the number at the end of the address. These are all old, many include measurements and photographs but all seem to tell the same story. General retreat of glaciers and in many cases this begins in the 1700's.
    Response: Just letting you know, in my new phase of curmudgeon webmaster, even terms like "outlandish claims" gets you close to deletion. Do we really need to resort to such hyperbole in a constructive discussion?

    How should we interpret recent data? Considering the correlation between air temperature and glacier extent (Greene 2005), it's hardly outlandish to link the last few decades of warming temperatures with shrinking glaciers.

    Could current glacier trends be just the result of coming out of an ice age? Around 1960 to 1970, glaciers were in near equilbrium which indicates glacier shrinkage in the late 20th Century is essentially a response to post-1970 global warming (Greene 2005).

    Lastly, thanks for the links to glaciers receding as far back as the 1700s. What does this prove? That climate has changed in the past, with only a minimal or no influence from CO2. Does this mean humans can't affect climate? Quite the contrary. Natural climate change in the past proves that climate is sensitive to radiative forcing. If the planet is in energy imbalance, global temperatures will change.

    CO2 is imposing an energy imbalance on climate now. The CO2 radiative forcing is well understood and observationally measured. So citing past climate change is actually citing evidence for our climate's sensitivity to CO2.
  45. The albedo effect
    Hi Henry, So, quantitatively, you're saying that the prevention of solar energy from reaching the Earth's surface is as great as (or greater than) the amount that is kept in by greenhouse gases. I would like to see a scientific citation of that. Later on, I'll dig into what you've said about this elsewhere, but for now it seems to me that you're ignoring a few things. First, visible light makes up a lot of incoming solar radiation and hits the Earth, but a lot of it is converted to longwave radiation (so outgoing longwave radiation can be more important than incoming for temperature implications). Atmosphere_Transmission_Blackbody_Only.png Second, with increasing greenhouse gases we're seeing less of the pertinent wavelengths leaving the Earth and hitting satellites (so GHGs don't reflect the incoming infra-red effectively). Third, more of those same pertinent wavelengths are hitting sensors on the ground (your idea would suggest that less reaches the Earth). Support for the last two items can be found on Skeptical Science, here: http://www.skepticalscience.com/empirical-evidence-for-global-warming.htm Look for the heading "The Planet is Accumulating Heat" and then read the prior 4 paragraphs, and the citations therein. When I have a moment later I'll try to look further to make sure I'm not misunderstanding you.
  46. CO2 lags temperature
    If the data were truly being analyzed at face value, as the author of this site suggests, then the only conclusion that can be drawn from the data is the following: Some mixture of greenhouse gases (H2O, CO2, Methane, etc), where the ratio of H2O vapor to the others is unknown, but important, MAY contribute to a fixed magnitude amplification of Milankovitch heating, which does NOT produce a positive feedback cycle. Our lack of understanding of the mechanism that drives such temperature amplification without leading to a positive feedback is testament to the complexity of the interactions taking place, and the need for more study. The fact is that the data do not support positive feedback, as there is no acceleration in the temperature trends, and as other posters have pointed out, the climate has indeed reversed substantial warming trends while greenhouse gas content continued to rise. What I sense is that as a group, CO2 warming supporters are having a hard time admitting to themselves, and to others, that we just don't have a sufficient understanding of all the relevant mechanisms at play to substantially prove our hypotheses. I think it's arrogance, personally.
  47. An overview of Greenland ice trends
    Mizimi, "a high concentration of carbon dioxide and other greenhouse gases is not a necessary condition for period of warming to arise". I know, this kind of trivial findings sometimes pass peer review. It pairs the logically false claim that becuase climate has changed in the past it cannot be the human influence this time. As for the graphs you quote, you should look at seasonal temperatures; you don't need yearly averages above 0 °C to melt ice during summer and for sure no one has ever claimed that there's melting in Greenland in winter ...
  48. There is no consensus
    commonman313, at classroom level it might be true (although sad) that "they trust their professors and paid a high price for thier education". But here we are talking about a plethora of distinguished sscientists in many different fields; i strongly doubt that just "a very small minority actually go beyond their classroom assignments and validate for themselves". As for "your part", you are missing that what matters for the attribution studies are the trends, not the absolute values.
  49. It's freaking cold!
    RECORD HIGH TEMPERATURES FAR OUTPACE RECORD LOWS ACROSS U.S. ...The ratio of record highs to lows is likely to increase dramatically in coming decades if emissions of greenhouse gases continues to climb... If temperatures were not warming, the number of record daily highs and lows being set each year would be approximately even. Instead, for the period from January 1, 2000, to September 30, 2009, the continental United States set 291,237 record highs and 142,420 record lows... The study also found that the two-to-one ratio across the country as a whole could be attributed more to a comparatively small number of record lows than to a large number of record highs. This indicates that much of the nation's warming is occurring at night, when temperatures are dipping less often to record lows. This finding is consistent with years of climate model research showing that higher overnight lows should be expected with climate change... "One of the messages of the study is that you still get cold days...Winter still comes..." ...analyzed several million daily high and low temperature readings taken over the span of six decades at about 1,800 weather stations across the country....a quality control process at the data center..looks for such potential problems as missing data as well as inconsistent readings caused by changes in thermometers, station locations, or other factors... Meehl et al, ucar.edu Press Release, November 12, 2009
  50. There is no consensus
    Commonman313 asked "So how sound is the evidence for the present consensus?" A good answer is in Naomi Oreskes's "Consensus in Science: How Do We Know We're Not Wrong?".

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