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Comments 126701 to 126750:

126701. HumanityRules at 13:11 PM on 17 November 2009
        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
126702. Steve L at 10:50 AM on 17 November 2009
        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.
126703. Riccardo at 09:30 AM on 17 November 2009
        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.
126704. David Horton at 07:00 AM on 17 November 2009
        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 :-)
126705. Henry Pool at 06:03 AM on 17 November 2009
        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
126706. Mizimi at 05:51 AM on 17 November 2009
        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.
126707. chris at 04:46 AM on 17 November 2009
        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!)
126708. Steve L at 03:43 AM on 17 November 2009
        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.
126709. Henry Pool at 03:04 AM on 17 November 2009
        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.
126710. chris at 00:39 AM on 17 November 2009
        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
126711. chris at 00:15 AM on 17 November 2009
        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
126712. HumanityRules at 23:41 PM on 16 November 2009
        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. :-)
126713. Mizimi at 23:23 PM on 16 November 2009
        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"
126714. Riccardo at 19:17 PM on 16 November 2009
        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.
126715. HumanityRules at 18:52 PM on 16 November 2009
        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/
126716. HumanityRules at 18:32 PM on 16 November 2009
        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.
126717. HumanityRules at 17:39 PM on 16 November 2009
        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.
126718. HumanityRules at 14:47 PM on 16 November 2009
        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.
126719. Steve L at 09:51 AM on 16 November 2009
        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.
126720. DrMike at 05:14 AM on 16 November 2009
        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.
126721. Riccardo at 04:08 AM on 16 November 2009
        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 ...
126722. Riccardo at 03:52 AM on 16 November 2009
        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.
126723. Sam Spade at 03:21 AM on 16 November 2009
        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
126724. Tom Dayton at 02:54 AM on 16 November 2009
        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?".
126725. RSVP at 02:45 AM on 16 November 2009
        An overview of Greenland ice trends
        chris, I take it you didnt like the fact that the exact same data leads to two completely different predictions, (i.e., 436 years and 11,400 years). All I did in the first case was to use the acceleration derived from the data, and in the second case ignored the acceleration completely, but used the overall slope. In this sense, whatever information my calculations could possibly convey are equivalent to the graph,.. except that I was also considering the overall mass, which I assume is significant. So you may not find any of this helpful, but there is a certain usefulness in knowing what you cant know.
126726. Mizimi at 02:18 AM on 16 November 2009
        An overview of Greenland ice trends
        "A recent study by Peter Chylek et al. (2006) put all of these Greenland temperature records together in one place (Figure 8 ), and commented: Although there has been a considerable temperature increase during the last decade (1995 to 2005) a similar increase and at a faster rate occurred during the early part of the 20th century (1920 to 1930) when carbon dioxide or other greenhouse gases could not be a cause. The Greenland warming of 1920 to 1930 demonstrates that a high concentration of carbon dioxide and other greenhouse gases is not a necessary condition for period of warming to arise. The observed 1995–2005 temperature increase seems to be within a natural variability of Greenland climate" http://www.worldclimatereport.com/index.php/2007/10/16/greenland-climate-now-vs-then-part-i-temperatures/ The GISS temperature graphs on this site ( covering coastal stations..the warmest bits) show annual means which rarely go above 0C. Given that the average height of the ice sheet is, as Chris points out, over 2000m, and add a lapse rate of 6C/km the annual avergae temp inland is not going to be far off -10 to -12C. Not much melt there I think. Also we do not know how much of that 300m depression was there before the ice (if any) so it is not possible to attribute all of it to the weight of the ice.
126727. commonman313 at 01:43 AM on 16 November 2009
        There is no consensus
        The important question here is, how important is concensus to science. Lets face facts, a huge portion of people holding any type of degree will simply parrot back what thier professors taught them. This is understandable as they trust their professors and paid a high price for thier education. However, this does not reduce the need to point out that a very small minority actually go beyond their classroom assignments and validate for themselves what they learned. In summary, as long as man made GW is taught in our schools from elementary through college, few should expect any different result than what was pointed out here; concensus only proves what is being taught and can not be used as scientific proof of any theory. Science is proved by evidence not by degrees. Those on both sides of the debate should focus on the scientific evidence so the general public can have a reason to believe/not believe besides "those smart people say its so". Here's my part: http://earthobservatory.nasa.gov/Features/SORCE/sorce_05.php There is a 5% error in our knowledge of the absorption of solar radiation and a 1% error would throw off all the climate models. So how sound is the evidence for the present consensus?
126728. ProfMandia at 23:42 PM on 15 November 2009
        An overview of glacier trends
        From WGMS: In 2005 there were 442 glaciers examined, 26 advancing, 18 stationary and 398 retreating. 90% of worldwide glaciers are retreating. In 2005, for the first time ever, no observed Swiss glaciers advanced. Of the 26 advancing glaciers, 15 were in New Zealand. Overall there has been a substantial volume loss of 11% of New Zealand glaciers from 1975-2005, but the number of advancing glacier is still significant. Tamino also has a very good image that shows the absurdity of the cliams that galciers are advancing: http://tamino.files.wordpress.com/2009/08/glaciers.jpg?w=500&h=295
126729. Tom Dayton at 23:37 PM on 15 November 2009
        The albedo effect
        Steve L, you might have given up on that long prior discussion with Henry Pool before I threw in my two cents about his CO2 reflection assertion. I don't know how else to explain it to him.
126730. ProfMandia at 23:29 PM on 15 November 2009
        An overview of glacier trends
        John, A few more good images include: http://www.wgms.ch/mbb/mbb10/Abb1.pdf (This is just a bar chart of the same image you showed in comment #1) http://www2.sunysuffolk.edu/mandias/global_warming... Source: http://www.grid.unep.ch/glaciers/graphics.php
126731. HumanityRules at 20:34 PM on 15 November 2009
        An overview of Greenland ice trends
        #14 i)I think that was my point that the review looked at multiple points not just the salt marsh data which you originally quoted. I don't know where you get smallish (generally 1-10 cm per century) rates for natural sea level change from. Table two shows max rates for some of the more recent measurements (last 10,000years) at 0.1-0.2metres/century. Am I mis=understanding that table? The historical data is by it's nature local and for that matter sporadic. But it remains the best data we have i)If you take the 3 more accurate measurements for the past decade the review suggests between 1-3mm/year (thats 10-30cm/century if you extrapolate) see this long quote from Milne. Yhat is what I understand from this long quote from Milne "After applying corrections for these biases, several studies14-16 have shown greatly improved consistency, in one case14 finding a tightly-closed sea-level budget for interannual and seasonal cycles, but a significant imbalance of over 3 mm/yr in the trend. In the second case15, a smaller net imbalance of about 1 mm/yr was found (this is within the estimated error bars). In the third study16 GRACE data were used in two different ways, in one case using a larger geodetic correction over the oceans than in other studies, and in the other using it only to estimate Antarctic and Greenland mass loss, and combining with other datasets to estimate the total mass entering the ocean. These two methods both result in a balance to within a small fraction of one mm/yr." ii) a) I'm not sure which is correct. The Netherlands data could be correct for the local changes while the Grinsted paper could be accurate on a wider level so both figures could be right. Without accepting Grinsted's figure there does seem to be an error in your interrution of it. Grinsted is a simplified model which identifies a trend based on a relationship between temperature, ice melt and sea levels. There are other processes which cause short term speeding up and slowing down of the ice melt. I'd suggest you're wrong to try to give an averaged rate for the MWP. Similarly it would be wrong to give an average rate between two widely spaced data points as you have no way of knowing if the rate of sea level change remained constant over that time period. Especially when you are comparing it to a decade of detailed global data which by it's nature contains all that detail. I'm starting to think the whole process is invalid. b)Back to the Milne paper. If you take my answer to i) that puts the most recent decades increase well within historical changes or at worst twice historical rates, I don't see where you get the 50x value. iii) I'm pleased to here that graph wasn't lonely but I did find that article lacked logic.
126732. iskepticaluser at 17:40 PM on 15 November 2009
        An overview of glacier trends
        Here's an interesting graphic from the IPCC: http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/fig2-18.htm
        Response: That is an interesting graphic. Note that the New Zealand glacier Franz Joseph is included at the bottom:
        
        
126733. Henry Pool at 17:10 PM on 15 November 2009
        The albedo effect
        Steve, maybe you must attempt to answer the question I asked in 127 of "How do we know CO2 is causing warming?" You can also check any good solar radiation spectrum graph. It will tell you that ozone, water vapor and CO2 cause reflection of sunlight. It seems pretty obvious to me that that nobody did the right testing that would prove that CO2 causes warming, i.e. how much warming (by trapping earth's radiation) and how much cooling (by reflecting sunlight) is caused by CO2, i.e. what is the net effect? http://www.telegraph.co.uk/earth/earthnews/6553592/Climate-change-scep. Look at my comment at 3:43 pm on 13/11/09. I am (still) not convinced that CO2 causes global warming. But if you have the proof from actual measurements made during actual tests I am (still) willing to be convinced. (I am a believer turned skeptic - I am not saying global warming is not happening, I am saying that I do not know if CO2 is the cause). In any case, it looks to me now that ozone is increasing and if this trend continues this will/could wipe out a lot of the sun's energy coming to earth.
126734. David Horton at 09:49 AM on 15 November 2009
        An overview of glacier trends
        Great work as always John, clear and succinct. Are there no NZ glaciers included? I don't see Franz Joseph there which is the one Australian denialists always like to mention. And Steve at #2 - yes, that would be interesting, but you may find that the ones they cherry picked are still gaining. My understanding is that glaciers (the vast majority) are shrinking because of rising temperatures at their site. On the other hand in some situations, particularly (solely?) those near coasts, rising water temperatures may result in increased snow fall which will counteract the melting. Franz Joseph is a case in point. The same thing applies, on a much larger scale, to Antarctica.
126735. Steve L at 08:58 AM on 15 November 2009
        An overview of glacier trends
        The first thing I noticed from this post was the small number of glaciers that have a long term record. I was sure we had longer term data on more glaciers. But I guess mass balance is more difficult to estimate than some other metrics regarding recession. So I wonder if data from these photo projects (eg: http://www.nrmsc.usgs.gov/repeatphoto ) can be compiled into something useful for quantitative analysis. I visited the Burgess Shale (Canadian Rockies) about a decade ago and saw two glaciers across a valley and could make a comparison to photos taken from the same spot approximately 80 years earlier. Surely there are many such instances around the world.
126736. chris at 07:09 AM on 15 November 2009
        An overview of Greenland ice trends
        The notion that future melt can be assessed/dismissed by back of the envelope numerology and false arguments, isn’t very helpful. There has actually been substantial recent investigation of this problem: (i) Recent analysis indicates that 21st century sea level rise is likely to be well in advance of the IPCC estimate. Projected 21st sea level seems to be closer towards the 1 metre level and this requires “non-linear” effects on ice sheet dynamics that are consistent with elements of “collapse”. HumanityRules brought a recent paper on sea levels to our attention. This projects a 1 metre 21st century rise based on an analysis of temperature-dependence of past sea level rise [1]. A recent analysis of the contributions of ice sheet dynamics to sea level rise supports a projection of 0.8-2.0 metres of 21st century sea level increase [2], although rises towards the lower end of the range are considered more likely. These all support very substantial attenuation of the Greenland ice sheet in the 100’s of years timescale. [1] A. Grinsted et al. (2009) Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD Climate Dynamics; in press [2] W. T. Pfeffer et al. (2008) Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise. Science 321, 1340-1343 (ii) Mizimi suggests that the 300 metre depression of the central Greenland ice sheet resulting from isostatic depression precludes ice sheet collapse. However the average height of the Greenland ice sheet is over 2100 metres, and there is obviously plenty of scope for major Greenland collapse yielding substantial (several metres) contributions to sea level rise. Analysis of the Greenland bedrock topography identifies multiple outlet channels (460 of these), of which only around 36% have been activated up to the year 2000 [3]. These potentially allow increasingly rapid rate of outlet flow from the ice sheet. Likewise an analysis of rapid retreat of the Sam Ford Fjord glacier during the last glacial to Holocene transition 9500 years ago suggest that glaciers with very similar topologies in Greenland and West Antarctica can undergo rapid retreat (10’s to 100’s of kilometers in the coming centuries) [4]. [3] Lewis S. M. et al. (2009) Hydrologic drainage of the Greenland Ice Sheet Hydrol. Process. 23, 2004-2011 [4] Briner J. P. et al. (2009) Rapid early Holocene retreat of a Laurentide outlet glacier through an Arctic fjord Nature Geosci. 2, 496-499 (iii) While Mizimi suggests that the central regions of the ice sheet “has not changed for over 100,000 years” we know that isn’t true since the deepest (3000 metres) central Greenland cores reach bedrock at a bit over 100,000 years ago. So a large proportion of the central parts of the Greenland ice sheet have only been deposited during the last 100,000 years. As we know, during the last interglacial 125,000 years ago when Arctic temperatures were ~2 oC warmer than now, sea levels were 4-6 metres higher [5]. Much of this was from massive Greenland melt. [5] Allison I. et al. (2009) Ice sheet mass balance and sea level Antarctic Sci. 21, 413-426 (iv) Analysis of rates of sea level rise in the past are instructive about how ice sheets might respond to forcing from very fast temperature rise. During the transition to the present interglacial there was a period of very rapid sea level rise (meltwater pulse 1A, 14,600 years ago) when sea levels rose 20 metres in 500 years [6]. During the last interglacial 125,000 years ago when the situation was more comparable to the present, the transition to sea level highstands that were 4-6 metres above current sea level, occurred at rates of 1.6 metres per century [7]. These rapid large melts occurred during climate transitions with overall warming that was slower than current warming. [6] A. J. Weaver (2003) Meltwater Pulse 1A from Antarctica as a Trigger of the Bølling-Allerød Warm Interval Science 299, 1709-1713 [7] Rohling, E. J. et al. (2008) High rates of sea level rise during the last interglacial period. Nature Geoscience, 1, 38–42 (v) The Greenland ice sheet is pretty much committed to major melt already at current greenhouse gas levels. We know that ice sheet disintegration/melt in a warming world generally occurs much faster than ice sheet growth in a cooling world, since disintegration/melt can occur through dynamic processes, whereas growth is limited by the rate of precipitation. The evidence suggests that dynamic processes (flow transition from ice sheet to floating ice shelf; the dynamics of rapidly flowing ice streams and outlet glaciers; the effect of basal melt water on ice dynamic processes [5]), are likely to cause Greenland (and the West Antarctic ice sheet) to melt much more quickly than “back of the envelope” guesswork might imply…
126737. PeterPan at 06:26 AM on 15 November 2009
        Are humans too insignificant to affect global climate?
        Re. #31, Now a new paper in GRL claims that the ariborne fraction has stayed constant since 1850: Knorr 2009
126738. chris at 06:04 AM on 15 November 2009
        An overview of glacier trends
        pdt, the World Glacier Monitoring Service seems to do periodic updates and are currently collating data for the next update incorporating the period 2007-2008: http://www.geo.unizh.ch/wgms/datasub.html We spent some time in Switzerland this summer, and visited some glaciers. We found this site covering Swiss Alpine data through 2008 pretty interesting: http://glaciology.ethz.ch/messnetz/ While worldwide updated mountain glacier data might not be available through 2008, the increasing rates of polar ice sheet mass loss supports the expectation that mountain glacier retreat is continuing through the last couple of years (as it is in the Swiss Alps): Velicogna, I. (2009), Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE Geophys. Res. Lett. in press http://www.agu.org/pubs/crossref/2009/2009GL040222.shtml abstract: “We find that during this time period [April 2002 and February 2009] the mass loss of ice sheets is not constant, but accelerating with time, i.e. that the GRACE observations are better represented by a quadratic trend rather than a linear one, implying that the ice sheets contribution to sea level becomes larger with time. In Greenland, the mass loss increased from 137 Gt (gigatonnes)/yr in 2002-2003 to 286 Gt/yr in 2007-2009, i.e. an acceleration of -30 +/- 11 Gt/yr^2 in 2002-2009. In Antarctica the mass loss increased from 104 Gt/yr in 2002-2006 to 246 Gt/yr in 2006-2009, i.e. an acceleration of -26 +/- 14 Gt/yr^2 in 2002-2009."
126739. Steve L at 05:03 AM on 15 November 2009
        An overview of glacier trends
        I think Fred Singer and others have been doing this cherry-picking for years. I wonder if it would be a worthwhile project to go back and find the glaciers they were identifying, say, 6 or more years ago and see how those glaciers have fared since.
126740. pdt at 04:47 AM on 15 November 2009
        An overview of glacier trends
        Is there data available for 2006 - 2008?
        Response: Not quite but I dug a little deeper on the WGMS website and found data through to 2007:
        
        
126741. hank at 03:11 AM on 15 November 2009
        ACRIM vs PMOD, the rematch
        Clayco, look at the cites in that paper. It's speculative. It ends with a supposition, a what-if. What remains is for someone to find a way to establish the existence (measure, identify, show, detect) of those supposed effects. Show they happen, measure them. Remember, for a "god-in-the-gaps" explanation, you need two of them, you need _both_ 1) show the hidden cause working, and 2) find an explanation that counteracts the known causes already accounted for. You need to subtract the known causes with some unknown force taking them out, then replace them with the same amount of effect from the newly revealed cause. ----excerpt----- ... Its effect on climate is supposed to be through modulation of the cosmic rays flux which affects stratospheric ozone and small constituents (Veretenenko S.V., Pudovkin M.I., J. Atm. Solar-Terr. Phys., 61, 521, 1999), and/or aerosol ionization (Marsh N., Svensmark H., Space Sci. Rev., 107 (1), 317, 2003), and/or the global electric circuit (Tinsley B.A. et al., Adv. Space Res., 40 (7), 1126, 2007), and finally the transparency of the atmosphere. However, the mechanism is not quite clear, and is not included in any climate simulation model ...." If you go and look at each of those papers, follow the "citing papers" forward in time. The supposed mechanisms are less than "not quite clear" in each case. The unstated supposed mechanism that counteracts the known forcings is also not discussed at all.
126742. RSVP at 19:53 PM on 14 November 2009
        An overview of Greenland ice trends
        John, Sorry if I came across that way. My comment was only in reference to the math error, and I appreciated Mizimi's pointing it out. By the way, he also says something later that seems reasonable, implying that the ice mass acceleration is not necessarily a constant, and would tend to diminish as soon as the bulk of the peripheral ice fields disappear. I am sure the problem is much more complex, and even the simplest models would depend on a series of functions that reflect the dynamics of various stages. Personally, I dont think it is at all realistic to extrapolate to 436 based on a second derivative extracted from the fuzz of nine samples. It is however useful to give some feel of a worst case scenario and perhaps what is possible. However, another very simple calculation with the same data leads to very different conclusion. That is to assume acceleration is zero or neutral, but that the ice loss rate (slope) is constant at the current rate. From the curve, we see about 1500 x 10e9 T/year over a 6 year period, which equals 250x10e9 T/year. Using the same value for total ice... 2.85 x 10e15 T / 250 x 10e9 T/y = 11,400 years.
126743. Philippe Chantreau at 18:56 PM on 14 November 2009
        An overview of Greenland ice trends
        Mizimi, as ice is shed, isostatic rebound could bring the underlying land quite a bit higher, so all that ice might not be as safely land locked as you say.
126744. Riccardo at 07:49 AM on 14 November 2009
        An overview of Greenland ice trends
        RSVP, i didn't want to say that the GIS might collapse altogether. There might be partial collapse along the slopes at the edges. How comes that GIS cannot release all of it's ice? Given that we are heading toward temperatures never seen in the last several hundreds thousands years (not just 100,000), the GIS is definitely capable of releasing all of its ice and allow a 7 m sea level rise. It's just a matter of how much warming and how much time it takes.
126745. Mizimi at 04:51 AM on 14 November 2009
        An overview of Greenland ice trends
        The Greenland ice sheet cannot 'collapse'. The ice sheet sits in a basin around 300m below sea level surrounded by mountains...whether the basin is due to the weight of the ice or was there originally is not clear. What is clear from core samples is that the central and most massive portion of the ice sheet has not changed for over 100,000 years. What we are seeing now is increased melt and ablation at the edges of the ice sheet which ,if it continues, will diminish as the central sheet becomes unable to sustain the flow outwards. So there cannot be a collapse and no 7m rise in sea level.
126746. Steve L at 04:50 AM on 14 November 2009
        The albedo effect
        At the risk of encouraging nonsense, Henry Pool (#20) -- where do you find CO2 reflecting a lot of sunlight? My understanding is that it is mostly invisible to visible light but opaque to infra-red.
126747. Riccardo at 03:44 AM on 14 November 2009
        An overview of Greenland ice trends
        RSVP, i've never thought of doing this rough calculations. This means that assuming not even partial rapid collapse of the ice sheet we'd get 16 mm/yr, 1.6 m in a century, from Greenland alone. Pretty scaring, indeed; let's hope it will slow down. Take it easy Greenland!! :)
126748. RSVP at 02:09 AM on 14 November 2009
        An overview of Greenland ice trends
        To Mizimi Thank you for pointing out my error. You are right about the exponent, which was also missing in the denominator. Plugging new values in gives us... years = sqr(2 x 2.85 x 10e15/30 x 10e9) = 436 years hmmmm... how long do you have to boil a hat to optimize digestion?
        Response: You're remarkably blase about the potential 7 metres sea level rise from the collapse of the Greenland ice sheet not to mention a similar contribution from the Antarctic ice sheet. Surely you realise the impact of such a sea level rise on humanity.
126749. chris at 01:58 AM on 14 November 2009
        An overview of Greenland ice trends
        today's Science has a relevant paper: M. van den Broeke et al. (2009) Partitioning Recent Greenland Mass Loss Science 326, 984-986 (November 13, 2009) http://www.sciencemag.org/cgi/content/abstract/326/5955/984 abstract: Mass budget calculations, validated with satellite gravity observations [from the Gravity Recovery and Climate Experiment (GRACE) satellites], enable us to quantify the individual components of recent Greenland mass loss. The total 2000–2008 mass loss of ~1500 gigatons, equivalent to 0.46 millimeters per year of global sea level rise, is equally split between surface processes (runoff and precipitation) and ice dynamics. Without the moderating effects of increased snowfall and refreezing, post-1996 Greenland ice sheet mass losses would have been 100% higher. Since 2006, high summer melt rates have increased Greenland ice sheet mass loss to 273 gigatons per year (0.75 millimeters per year of equivalent sea level rise). The seasonal cycle in surface mass balance fully accounts for detrended GRACE mass variations, confirming insignificant subannual variation in ice sheet discharge.
126750. chris at 22:57 PM on 13 November 2009
        An overview of Greenland ice trends
        re #10 (i) Your first point is incorrect HumanityRules on two levels (I think you've misread Milne et al.) Firstly the data isn't from one type of measure, from one locality. Milne is using the Maine salt marsh data as a detailed illustration of local relative sea level variability. However their paper is a review, and their conclusions come also from other papers cited(specifically, as they indicate, from coral microattols from the Cook Islands; foraminifera from peat deposits on the Connecticut coast; salt marshes on the coast of Denmark). And there are many other examples including the papers I cited on relative sea level variation in NW Europe in post #9. The bigger error, is to mistake local relative sea level for global eustatic sea level. Milne et al present the evidence that even considering local variation in sea level (that may have post glacal isostatic and land subsidence contributions etc.), this is smallish (generally 1-10 cm per century). (ii) Let's look at global eustatic sea level. You've linked to another unattributed picture in your post. This turns out to be a model of past and projected sea level rise from this paper [*]. Presumably you want us to take it at face value, so let's do so: (a) Grinsted et al use historical temperature data to estimate possible sea level variation during the last 2000 years. For example, they suggest that during the period from around 600 AD to 1150 AD in the Medieval Warm period), sea levels might have risen by around 25 cm. This is about 15% of the sea level rise during the same period in the earlier picture you linked to in your post #3 (which presumably you now reject; they can’t both be correct). It corresponds to a bit over 2 cm per century. If one takes the Grinsted analysis at face value we may well expect around 1 metre of sea level rise during the 21st century. (b) So the data you’ve presented to us indicates the sea level rise of the 21st century may occur at close to 50 times the rate of sea level rise associated with what is considered to be the transition to the warmest period in the previous 2000 years before the middle of the 20th century (sea levels are already rising around 15 times more quickly than during the period pictured in the graph you linked to). If you were to put the projected 21st century rise on the same horizontal time scale as the previous 2000 years in your picture, it would be near vertical. Isn't this all pretty consistent with Milne et al.? They review data that shows rather little preindustrial variation in eustatic sea level; that current measurements show sea levels are already rising much faster (by more than 10-fold) that even during the rise to the MWP; and that we are pretty certain to get significantly increased rates during the current century. It's certainly inconsistent with the old graph you linked to from that dodgy web site (your post #3). (iii) In a previous post (#8) you asked the question "Would you put 100% of the sea level rise this century down to AGW?". If you look more widely at the NERC Planet Earth site from which you cut and pasted that lonely figure from Grinsted et al (2009) you would have found an analysis that addresses your question: http://planetearth.nerc.ac.uk/news/story.aspx?id=551 Jevrejeva et al determine that almost 80% of sea level rise during the 20th century is as a result of anthropogenic greenhouse forcing. In fact they point out that the anthropogenic contribution to sea level rise was likely suppressed somewhat by volcanic eruptions: "If no volcanic eruptions had happened since 1880, then sea-level rise over the last century would've been seven centimetres higher than it was," explains Jevrejeva. [*]A. Grinsted et al. (2009) Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD Climate Dynamics; in press. [**] Jevrejeva, S et al (2009) Anthropogenic forcing dominates sea level rise since 1850 Geophys. Res. Lett., doi:10.1029/2009GL040216, in press.

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