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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 106801 to 106850:

  1. Do critics of the hockey stick realise what they're arguing for?
    chriscanaris, I'm afraid I'm not following you. The IPCC AR4 section you link to doesn't seem to suggest that CO2 is not the driver of anthropogenic climate change. It merely states the probable range of uncertainty around the best estimate for climate sensitivity, and lists some of the major feedbacks that contribute to climate sensitivity. CO2 is the largest anthropogenic forcing, unless you have something to suggest that everybody's been missing: Anthropogenic and natural radiative forcings (IPCC AR4 Section 2.1) The feedbacks mentioned in the IPCC text you link to are not independent actors. They are in fact the mechanism by which the forcings (shown in John Cook's figs 2 and 3 above) translate into temperatures (shown in JC's fig 1). The point of this thread is that we know pretty well what the forcings have been for the past millennium. If it turned out that the amplitude of the MWP-LIA difference was larger than expected, that would necessarily imply that climate sensitivity is also larger than expected. Nothing in the IPCC section that you cite contradicts this (or even particularly relates to it).
  2. Despite uncertainty, CO2 drives the climate
    Joel #28: "IPCC projections are no better than the economic models they use for inputs. The science can be perfect, but with a bad economic model it is GIGO." All of which is smoke since the IPCC projections span a range of emissions scenarios that extends both above and below what you consider likely. They covered everything from impossibly high (i.e. continuous population and economic growth) to impossibly low (i.e. immediate cessation of all fossil fuel use). In short, it's covered.
  3. Do critics of the hockey stick realise what they're arguing for?
    John Cook "Technically, climate sensitivity is defined as the change in global temperature if the planet experiences a climate forcing of 3.7 Watts/m2" Should'nt sensitivity be related in some way to units of time? If something responds slowly, it is described as being less sensitive. If something responds faster, more sensitive, etc.
  4. Do critics of the hockey stick realise what they're arguing for?
    Always assuming that you believe anthropogenic climate change as originating *overwhelmingly* with CO2. If some of the uncertainties acknowledged in at least one authoritative source are taken seriously, the picture may be somewhat more complicated and hence close scrutiny of the palaeoclimate record and climate sensitivity and its sources may still be warranted. CO2 is *very* important but it may not be the whole story. I do not buy arguments that suggest that a robust MWP would justify 'business as usual' on an indefinite basis. However, ”The last temptation is the greatest treason/ To do the right deed for the wrong reason.” Pedantry aside, doing the right deed for the wrong reason may cause us to overlook vital elements in planning for an uneratin future. Philip64 @ 4: Interesting that you mention Venice, which has been subsiding because of exploitation of aquifers. Tidal factors seem to be of lesser signhifcance than is commonly supposed.
  5. It's the sun
    I wouldn't waste your time with Howard's site. An example of its 'thinking' : "Ever so Clever Alarmist Tricks of Trade There seems no end to the assemblage of clever tricks and blockades which the bretheren of the alarmist church can dream up. And since they hold pretty much all the top jobs all over their global diocese they for the most part go undetected and unreported." Hm, nice...
  6. Do critics of the hockey stick realise what they're arguing for?
    John, this is a really clear and well-written post. Just the kind of thing that SkS is known for. Nice work. Philip64's point is a good one. With the MWP being a long, slow rise rather than the steep increase in temperatures from AGW, more of the slow responding components of the climate system should have had time to adjust. That means sea levels, alpine glaciers, alpine/arctic tree lines, etc.
  7. Do critics of the hockey stick realise what they're arguing for?
    Excellent piece with a clear enough message, I think, even if the explanation behind it is (inevitably) complex. I don't know the answer to this, but if the MWP really was longer and warmer than the climate today, shouldn't it have seen a significantly larger rise in sea level than ours to date? Are there any reliable measures of sea level back then? (Anecdotally, I note that Venice was mainly built between the 12th and 15th Centuries, at sea level. No evidence that it was sitting high in the water during the subsequent little ice age, when Canaletto was endlessly painting it!)
  8. Do critics of the hockey stick realise what they're arguing for?
    I don't think the so-called skeptics are actually bothered about any of this because they hold those two propositions in totally separate compartments in their heads. I.E. the MWP was warmer than today, because, well, just because. That's what they are being told by their blog scientists and that is what they believe. Separate from that, climate sensitivity is lower (almost zero, in fact) because Lindzen says it is, and they believe him above all other scientists. To a so-called skeptic, the above can be held and believed at the same time without contradiction - well, to them, at least.
  9. Do critics of the hockey stick realise what they're arguing for?
    Whoa John, you might want to further add that the MWP was local to the northern hemisphere and had little to do with global climate forcing. While as a thought exercise it is an interesting idea that an increased Global MWP would infer greater climate sensitivity, you wouldn't want to inadvertently confuse people about the actual relationship to a Local MWP.
  10. Lars Rosenberg at 19:36 PM on 19 October 2010
    Do critics of the hockey stick realise what they're arguing for?
    It may be of some interest to quote the conclusion of Moberg et al. (2005), whose graph You reproduce: ”We find no evidence for any earlier periods in the last two millennia with warmer conditions than the post-1990 period—in agreement with previous similar studies. The main implication of our study, however, is that natural multicentennial climate variability may be larger than commonly thought, and that much of this variability could result from a response to natural changes in radiative forcings. This does not imply that the global warming in the last few decades has been caused by natural forcing factors alone, as model experiments that use natural-only forcings fail to reproduce this warming. Nevertheless, our findings underscore a need to improve scenarios for future climate change by also including forced natural variability—which could either amplify or attenuate anthropogenic climate change significantly.”
  11. It's the sun
    If you want to know the answer to sun spot production and the link to global temperature variation, then see this site, the answer will surprise you!! http://www.solarchords.com
  12. An underwater hockey stick
    Jumping around linksd brought me back to this page. I'm just curious if people are happy with the >1.5oC increase in temperature since 1900 seen in this underwater hockeystick?
  13. Explaining Arctic sea ice loss
    THe difficulty I find is that there are lots of predictions of tipping points such an ice free Arctic in the summer which will be the thing that convinces everyone that the models of climate change are correct. The problem with this is that when year after year it does not happen, the warning begin to look like one of these chaps walking around with a billboard saying "the end is nigh" and it has the opposite effect on peoples perceptions. The other issue is that although the long term trend is obviously down, the short term trend is up from the 97 low. If this continues for another year or two the graph will start to look curiously like a hockey stick.
  14. Throwing Stones at the Greenhouse Effect
    gpwayne "Some climate change skeptics dispute the so-called ‘greenhouse effect’, which keeps the surface temperature of the Earth approximately 30 degrees C warmer than it would be if there were no greenhouse gases in the atmosphere." Hmmm. No water vapor means no clouds. So with an open sky consisting only of N2 and O2 after millions of years of steady sunshine, you are saying that the oceans would remain frozen? No water vapor also means no snow or rain, so the land is now a dry powder as on the Moon. The dry air in contact with the dry land would receive heat via convection and rise and mix. This air has no GHG, so it cannot radiate heat... only accumulate it via convection with the surface, or release it back via convection to cooler locations on the surface. But this convection is limited to only the cooler air that has circulated downward. The hot air would rise and the stratosphere would get warmer and warmer. All this may sound like nonsense, yet it is no better than the picture you have painted.
  15. Throwing Stones at the Greenhouse Effect
    @HR: do you have figures that would justify this change in terminology to show us? After all, "Very Few" is more precise than "Some", so you must be basing this on some kind of empirical evidence, right?
  16. Throwing Stones at the Greenhouse Effect
    Shouldn't "Some climate change skeptics..." be "Very few climate change skeptics..."
  17. Throwing Stones at the Greenhouse Effect
    TIS: However, this article is inaccurate as I am not aware of anyone claiming that the atmosphere doesn't have an effect. Logically speaking, your (admitted) ignorance does not and cannot make this article "inaccurate."
  18. Throwing Stones at the Greenhouse Effect
    Roger A. Wehage, The relationship between the amount of CO2 in the atmosphere and the effect it has in terms of direct retention of energy is logarithmic. A fair number of 'skeptics' become aware of this and try to argue that it means that the effects will be minimal. However, it's no secret to anyone who knows anything about the science. Remember, the central prediction is that, with feedbacks included, there will be a roughly 1% change in the earth's absolute temperature with doubling of CO2. That's 3 Kelvin / ~300 Kelvin which in about 1%.
  19. Throwing Stones at the Greenhouse Effect
    Bibliovermis "she has over a decade of peer-reviewed field research under her belt" eh? Care to elaborate?
  20. It's the sun
    KL #693 The multiple regression on the climate karaoke confirms your analysis rather nicely - after the mid-20th century, co2 is the main driver of warming (as expressed in that case by temperature anomaly as the dependent variable). I can't remember offhand what the precision of the prediction is, but it was reasonable, although regression assumptions were violated somewhat. Who'd have thought - convergent evidence. I can't see this supporting your 'sceptic' argument at all though. It more confirms the opposite.
  21. Throwing Stones at the Greenhouse Effect
    AHHH 12C or 20C
  22. Throwing Stones at the Greenhouse Effect
    I shall clarify my position. During a hot house period, where the average surface T may be 20k, or a glaciation when the surface T maybe around 12k, at equilibrium, the amount of energy leaving the top of the atmosphere will be the same, and equal to the amount of energy entering the system. During transitions between these states there will be an imbalance between incoming and out going, with more leaving than entering during a decline in T, and more entering than leaving during a rise in T. The difference in the surface T is a result of the amount of energy contained in the system at their respective equilibriums, and is a result in a shift in the amount of energy in the system, but the "quantity" of energy leaving the system, on its own, is not necessarily representative of the energy contained in the system(T o the climate).
  23. Explaining Arctic sea ice loss
    Peter Can you tell me how you made your detrended HADCRUT series. I looks like AMO leads HADCRUT in some cases, lags in others. I'd like to reproduce your chart and take a look at how they vary.
  24. Throwing Stones at the Greenhouse Effect
    doug_bostrom at 09:04 I dont disagree, equilibrium can and does change, its the first sentence that just reads to me as though its saying proof of the GHE is that less energy leaves than enters the system... The proof is in the amount of energy contained in the system. Im being pedantic, i admit it, but that first sentence is misleading.
  25. Throwing Stones at the Greenhouse Effect
    Some net amount of energy is trapped or lost over time, Joe, or the collective ocean/atmosphere system could not become warmer or cooler over time.
  26. Throwing Stones at the Greenhouse Effect
    Good to the point article, but being a bit pedantic, i would agree with alkemist in regards to this paragraph. "By comparing the Sun’s heat reaching the Earth with the heat leaving it, we can see that less long-wave radiation (heat) is leaving than arriving (and since the 1970s, that less and less radiation is leaving the Earth, as CO2 and equivalents build up). Since all radiation is measured by its wavelength, we can also see that the frequencies being trapped in the atmosphere are the same frequencies absorbed by greenhouse gases." The climate may never be in perfect equilibrium, And the instrumental record certainly does suggest a build up of energy in the system, but energy in will equal energy out approximately . Energy is not trapped, its path length out of the atmosphere is increased, increasing the amount of energy in the system... Just with the way thats written it sorta comes across as suggesting that proof of the GHE is that less energy leaves than comes in... only during transition to a higher equilibrium is this true, and in something as chaotic as climate, its more a case of on "average".
  27. Tai Chi Temperature Reconstructions
    #69 Peter Hogarth at 08:01 AM on 19 October, 2010 Thanks for the comments- I am fully aware that your originial post isn't supposed to withstand much scrutiny. Neither are my reconstruction here. As a side note, I was able to replicate your plots to a satisfying eyeball degree. I wanted to highlight that Ljungqvist 2010 is using a much more simple approach than e.g. Mann 2009. I would like to try and redo my global reconstruction using some kind of gridding or area weighting, but to do that I need some tips on how-to-do. Even better some Matlab code. By the way, how did you use those proxies given as z-scores? I just run them through the same averaging process as the temp proxies. For baseline I use the years, 1000-1900, as Ljungqvist 2010.
  28. Tai Chi Temperature Reconstructions
    SRJ at 22:24 PM on 14 October, 2010 Thanks for this work. On first read through the Ljungqvist 2010 paper I would have to agree with you, but I would have to spend some time checking. The 2010 work is decidedly Northern Hemisphere above 30N whereas the Ljungqvist 2009 data has a fair proportion of tropical and Southern Hemisphere data also. I suspect that gridding will make some difference, but my original post wasn't meant to be a reconstruction that would withstand too much scrutiny! Your chart above is very interesting, and in my view further supports the idea of enhanced variability of the higher latitude Northern Hemisphere temperature anomalies, compared with the global average. There is some evidence of this high relative variability in paleo data going back through the ice ages.
  29. Throwing Stones at the Greenhouse Effect
    For the benefit of those who aren't familiar with Dr. Marohasy, her PhD is in Biology from the University of Queensland and she has over a decade of peer-reviewed field research under her belt.
  30. New temperature reconstruction vindicates ...
    # 166 See my comment another thread here elaborating on this.
  31. Tai Chi Temperature Reconstructions
    To elaborate on myself in #67: Peter Hogarth's approach is mostly similar to Ljungqvist 2010 except that Ljungqvist matches the variance of his composite series to the variance of the instrumental record. But there is no gridding or area weighting, all proxies contribute with equal weight. I have implented Ljungqvist approach and made a reconstruction using all proxies from Ljungqvist 2009 - note since the original post was written a few more have been added, the total number is now 71. The resulting graph is below, plotted together with Ljungqvist 2010. This graph allows one to compare the Tai Chi approach of the original post with the result of Ljungqvist, 2010. Disclaimer: I have also used my implementation of Ljungqvist 2010 approach on the original data from that article (data kindly provided by the author). I don't get a perfect match so there must be some small differences in the methods of me and Ljungqvist.
  32. Despite uncertainty, CO2 drives the climate
    #24 Obviously this graph is way out of date. The reactors they have under construction already would exceed that number. http://www.world-nuclear.org/info/inf63.html The article expects 80GWe by 2020, but since I started following the Chinese energy issues this number keeps getting revised upwards every month or two. If you scroll downward they have detailed information on the plants under construction, scheduled and proposed. The 80GWe only includes planned and under construction plants. It takes the Chinese about 48 months to build a reactor, so anything started by 2016 should be online by 2020. The Chinese government is projecting their carbon emissions to flatten out by about 2040. From what I can see they are totally serious about meeting that goal. Understanding these points is vital. IPCC projections are no better than the economic models they use for inputs. The science can be perfect, but with a bad economic model it is GIGO.
  33. Explaining Arctic sea ice loss
    The Inconvenient Skeptic at 01:49 AM on 14 October, 2010 It seems I may have pre-empted your potential comments on Arctic temperature here. I also responded to a comment you made on AMO there. To add to what D Kelly O'Day has done I will re-post the chart below for readers of this post, to save some effort for once. The AMO is de-trended North Atlantic SST from NOAA ESRL and I have de-trended the HadCRUT3 surface temperatures also to allow comparison. It is easy to see correlation, as we might expect from coupled Sea Surface Temperature (SST) and Surface Air Temperature (SAT), but causation (sea to air) is not evident from the relative phases.
  34. Despite uncertainty, CO2 drives the climate
    Joel #25: The baseline used in the graph is, in this case, completely immaterial to the point being made by the graph. Should it also have specified the data source? And the full details of the compilation methodology? And all of the base temperature station results? The fact that more information exists does not mean it is "misleading" to cite only the information relevant to the point being made. Again, your objections are picayune.
  35. DMI and GISS Arctic Temperatures: Hide the Increase?
    bgood2creation at 16:02 PM on 18 October, 2010 Yes, latent heat is the reason the air temperatures reach a plateau just above melting point rather than rising further in Summer. Some more references on increasing melt season over the last thirty years: Markus 2009, Howell 2009, Rodrigues 2009.
  36. Explaining Arctic sea ice loss
    @Inconvenient Skeptic I followed your link and found "The All Natural Cause of Global Warming". Here's my critique on your AMO - Global Warming post. Since you are commenting on this site, I thought that other Skeptical Science readers would like to comment on your AMO - Global Warming conclusions. Kelly O'Day
  37. Despite uncertainty, CO2 drives the climate
    #18 You need to google the term Capacity Factor. If you want to compare Wind to Nuclear, take the Wind number and divide by 5. In the U.S., at least, wind turbines run at 20% of capacity and nuclear plants are in the high nineties.
    Moderator Response: Reminder to everybody, please do not delve into issues of competing energy technologies here on Skeptical Science.
  38. Throwing Stones at the Greenhouse Effect
    TOP, JMurphy linked to the section of this site that answers your question, but here it is more explicitly. Links for 'Greenhouse effect has been falsified' One of those links is to Jennifer Marohasy's blog where she talks about "fictitious atmospheric greenhouse effects".
  39. Despite uncertainty, CO2 drives the climate
    #21 As I have already said (#12), the problem was with dana1981 reproducing the graph without the caption explaining in the first sentence that the baseline was 1950-80. Dana1981 made the graph proofy by using Figure 3 instead if Figure 1.
  40. DMI and GISS Arctic Temperatures: Hide the Increase?
    muoncounter, regarding, "Lots of red except in the summer, where one would have expected the most red. " You'll want to be careful not to confuse temperature anomaly with absolute temperature. If the baseline is -30 C, a plus 5 C anomaly is still colder than a +1 anomaly on a -1 C baseline. I would expect the Arctic to show a greater anomaly in the winter than the summer. The frozen Arctic Sea has a very high albedo; this means that less of the light in the visible spectrum and above will be converted to infrared in comparison to other, non-ice-covered parts of the world. CO2 acts on infrared (and a some microwave), not visible and UV. Albedo means nothing in the dark. You might also consider that an enhanced greenhouse effect results more in higher relative nighttime temperatures than in higher daytime temperatures, and the arctic winter is more or less one long night.
  41. Despite uncertainty, CO2 drives the climate
    @muoncounter: considering there are 8760 hours in a year, 150 billion KWh (or 150 TWh) gives approximately 17 GW or power, not 17 MW. 150,000,000,000,000 ÷ 8760 = 17,123,287,671.23
  42. Throwing Stones at the Greenhouse Effect
    Also: "The sun's powerful high frequency ultraviolet radiant energy can easily pass through the windows to warm the house" Not all windows let through UV rays. However, since a lot of the radiated energy is transmitted through visible light, your overall point still stands.
  43. Throwing Stones at the Greenhouse Effect
    @Roger (20): "Why are nearly 75% of Americans, American news media, and American politicians deniers?" Take comfort in knowing that, outside the US, the proportions are pretty much reversed.
  44. It's the sun
    I'm sorry, Ken, can you explain this to me in layman's terms? This site does a great job at explaining concepts in everyday language, you should follow that example.
  45. Throwing Stones at the Greenhouse Effect
    Just out of curiousity, who is disputing the Greenhouse Effect to point where it is in dispute?
  46. Throwing Stones at the Greenhouse Effect
    "By comparing the Sun’s heat reaching the Earth with the heat leaving it, we can see that less long-wave radiation (heat) is leaving than arriving (and since the 1970s, that less and less radiation is leaving the Earth, as CO2 and equivalents build up). Since all radiation is measured by its wavelength, we can also see that the frequencies being trapped in the atmosphere are the same frequencies absorbed by greenhouse gases." This is not accurate. One needs to compare the sun's and the earth's radiant intensities across their respective spectra. I can imagine the earth as a converter of higher frequency, shorter wavelength solar photons into lower frequency longer wavelength terrestrial photons.
  47. Throwing Stones at the Greenhouse Effect
    It seems a simple question, but teh question of the Moon's temperature does come up. It usually takes the form: "You tell us that without the greenhouse effect, Earth would be -18C average temp. But the moon has no atmosphere and is roughly the same distance from the sun. Its temperature varies wildly from extreme cold to extreme heat. Earth would be the same if it had no atmosphere, so the greenhouse effect must be false". SoD has a long explanation involving averages and heat capacity. Is there a shorter explanation for the non-physics major?
  48. Throwing Stones at the Greenhouse Effect
    Overall, this is a good post. Yet oddly, after making its basic point so well, the post suffers from a fit of diffidence that deprives it of much of its potential vigor. I refer to the 'might' in "What the Earth might be like without an atmosphere that sustains the greenhouse effect". 'Might'? Isnt' the whole point of the post that the greenhouse effect has NOT been falsified? Isn't the whole point that there is no serious doubt about it? For this reason, it should read 'would' not 'might. Look yourselves at how much more vigorous it is with this change (and a minor tense change, too): "We only have to look to our moon for evidence of what the Earth would be like without an atmosphere that sustains the greenhouse effect. While the moon’s surface reaches 130 degrees C in direct sunlight at the equator (266 degrees F), when the sun ‘goes down’ on the moon, the temperature drops almost immediately, and plunges in several hours down to minus 110 degrees C (-166F). "
  49. Despite uncertainty, CO2 drives the climate
    Joel, I have the opposite problem from you. I think the baseline should be set at 1850 so that the rise reflects all the temperature increase from the start of the idustrial era. We can compromise by choosing the time frame when the graph was originally started, say 1950-1980. That corresponds to when I was a child so it makes sense to me. Oh wait, that is what they did.
  50. Throwing Stones at the Greenhouse Effect
    Strangely enough, one of the best resources on the greenhouse effect is on Dr Ray Spencer's blog. He is a skeptic, but only on feedbacks, not on the greenhouse effect. See here

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