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Comments 69551 to 69600:

  1. Schmittner et al. (2011) on Climate Sensitivity - the Good, the Bad, and the Ugly
    The sea level rise was used as an example of significant climate change. That will not happen now (maybe) but since we are heating up something else dramatic might happen.
  2. Schmittner et al. (2011) on Climate Sensitivity - the Good, the Bad, and the Ugly
    Dr. James Annan has some thoughts on the new paper.
  3. Schmittner et al. (2011) on Climate Sensitivity - the Good, the Bad, and the Ugly
    skept @2:
    "how do we know if a 2,5 K warming imposed on initial conditions of the LGM has the same effect that a 2,5K warming on the present conditions, concerning sea-level rise?"
    We don't, and I wouldn't expect them to have the same effect. I was just trying to give an example of the kinds of radical climate changes that occur during glacial-interglacial transitions. That's not to say a similar amount of warming now will cause the same climate changes, just that we might expect similarly radical climate changes to result from similar radical temperature changes.
  4. SkS public talks in Canada and AGU, San Francisco
    bon voyage ! and a lot of success!
  5. Schmittner et al. (2011) on Climate Sensitivity - the Good, the Bad, and the Ugly
    Healthy skepticism – I'm quite new here and I hope it is the case for all reconstructions! Your point is clear, this is just one sensitivity study among dozens already published, and one whose main result is very dependent of a new proxy data set for LGM. Even if it was nearly correct (only future debates and eventual replications of the results will tell), it would fall in the range of the IPCC AR4 sensitivity, with already 3 models out 17 in 2,1-2,3 K sensitivity for 2xCO2 (and the CMIP5 first results will probably keep this range of 2-4,5 K in the AR5). As Knutti et Hegerl 2008 pointed out in their review, most equilibrium sensitivity estimates with different methods are centered around 3K. "Another concern regarding the study is in the model they used..." I often read paleoclimate reconstruction with models of intermediate complexity. Maybe they are useful for approximate AO equilibrium on long period ("run faster" as Urban says), but far less realists than AOGCM on short-term variations (as Tamino showed)? See for example Claussen et al 2002 for explanations about EMICs, notably : "EMICs include most of the processes described in comprehensive models, albeit in a more reduced, i.e., a more parameterized form. They explicitly simulate the interactions among several components of the natural Earth system including biogeochemical cycles. On the other hand, EMICs are simple enough to allow for long-term climate simulations over several 10,000 years or even glacial cycles ." "If Schmittner et al. are right about climate sensitivity and LGM temperature change, then if we continue with business-as-usual GHG emissions, we will match the amount of warming between glacial and interglacial periods much sooner. Some of the differences between glacial and interglacial periods include 120 meter sea level rise" Here, a question : how do we know if a 2,5 K warming imposed on initial conditions of the LGM has the same effect that a 2,5K warming on the present conditions, concerning sea-level rise? For example, Vermeer et Rahmstorf 2010 found with a semi-empirical approach a 124 cm sea leval rise for 2,6 K in 2100 (see table 1), not 120 m. Even if it is transient climate response, it is hard to imagine that equilibrium response (for the same 2,6 K warming) would add 119 m. I suppose a complete Earth System Model (with A-O coupling on small grids, but also carbon cycle, vegetation, ice etc.) could tell us what would happen with a 2,6 K warming. If there is a high dependency to initial conditions, the previous LGM-Holocene transition is not necessary a good reference.
  6. What's Happening To Tuvalu Sea Level?
    skept.fr @ 2 - See Timmerman (2010), the full paper is linked to in the post. The projections indicate an El Nino-like trend (a weakening of the wind-driven water mass) in the 21st century, which will oppose sea level rise (SLR) in the Pacific Islands. Sadly it's nowhere near enough to counter the contributions to SLR by thermal expansion and melting land ice. Victull @ 5 - see SkS post: Hiding the incline in sea level William @ 8 - Thanks. See the SkS rebuttals on coral atolls. I hyper-linked to it in the post, but it's not conspicuous. Further reading on this related topic is in the SkS rebuttal on coral bleaching. It is incredibly simplistic to think that sand accumulation (indicated in your link) will alleviate problems. I'm sure you can see the flaws of such "skeptic logic." I don't even broach the issue of ENSO (La Nina/El Nino) effects on rainfall in the tropical western Pacific, nor the threat of storm surge intensification. Add ocean acidification into the mix, and I expect most rational people can connect the dots. Tuvalu is living on borrowed time.
  7. What's Happening To Tuvalu Sea Level?
    Hi Michael (@4) for all that interesting information. I was thinking in terms of detecting rising sea levels and understanding direct impacts in general. Sea level rises and falls with perhaps a decadal periodicity and AGW is adding an increasing trend on top of that. At the same time rain patterns change, there's irrigation, etc. That trend in aquifer salinity might not be easily detectable over short time scales. If saltwater contamination is an important prediction and outcome of AGW, then perhaps there should be a good baseline developed of the world's vulnerably coastal areas. I just briefly googled to see if there was a sort of global monitoring. I found this webpage for Tasmanian aquifer salinity. Looks to me as though good baselines probably aren't widespread.
  8. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    MA Rodger @42, thankyou. I believe that this graph shows conclusively that natural variation is the major component in changes from year to year in atmospheric CO2 concentration. To avoid misrepresentation it should be noted that the graph does not show the annual emissions of CO2, but the change in the emissions from one year to the next. Had it shown the annual emissions, they would clearly have been much larger than the year to year fluctuations. Indeed, the first graph in post 40 shows exactly that. Therefore, and without any doubt, anthropogenic emissions are responsible for the long term trend in the graph of CO2 concentration.
  9. Philippe Chantreau at 05:20 AM on 27 November 2011
    Climategate 2.0: Denialists Serve Up Two-Year-Old Turkey
    I'm not sure anyone can without more specifics Mikel. What are these "issues"? For a start, why don't you look in details at the various investigations that have already been conducted on these e-mails? The leftovers that are being served up now to attempt to derail the Durban talks have absolutely nothing new, so whatever "issues" are there were already there 2 years ago, I presume.
  10. Schmittner et al. (2011) on Climate Sensitivity - the Good, the Bad, and the Ugly
    I have been wondering about the very different climate sensitivities determined using sea surface temperature data, and land data, as shown in figure 1. In general, climate change occurs faster over land than at sea, but that is because of the large thermal inertia of the oceans. Over long time spans, the temperature change should equalize. Land temperatures should still show a greater day/night, seasonal and annual fluctuations, but should fluctuate about a mean that is close to sea surface temperatures. Once exception is if the SST freezes. In that event, "Sea Surface Temperatures" as measured by proxies will not actually be the Sea Surface Temperature, ie, the upper surface of the ice, but rather the temperature of the liquid water beneath the ice. That water will, of course, be just above freezing temperature. Consequently, sea surface temperatures have a floor below which they will not fall. The consequence of this is that the lower global means surface temperatures fall, and hence the more extensive the sea ice, the greater the discrepancy between global mean sea surface temperature and global mean Surface Air Temperature. Unfortunately, as temperatures rise, there is no ceiling on Sea Surface Temperatures (except for a runaway greenhouse effect). Ergo, with rising temperatures, SST will rise to match land Surface Air Temperatures. That being the case, the land only climate sensitivity (in green in figure 1) is probably a better predictor of future climate change with increased CO2 than are the ocean, or land and ocean values.
  11. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    Off-topic graph as requested @37. Image and video hosting by TinyPic
  12. Lindzen and Choi find low climate sensitivity
    Can I recommend that we take discussion of Schmittner et al across to the new post discussing it?
  13. Climategate 2.0: Denialists Serve Up Two-Year-Old Turkey
    What legal issues, Mikel ?
  14. What's Happening To Tuvalu Sea Level?
    No argument whether sea level is rising or not or where it is rising. You have the hard data which says it is and any reasonable person would have to admit that the rise will most likely accelerate over the coming years. However, we may be focusing on the wrong factor. It could be that sea level rise is the least of the worries of the coral atoll nations. http://mtkass.blogspot.com/2011/09/by-by-coral-atolls.html William
  15. Lindzen and Choi find low climate sensitivity
    There is also an informative interview with Nathan Urban (second author of the Schmittner et al paper) at Planet3.org. He is not too happy about the way some so-called skeptics have used the graph shown in les's comment above, especially mentioning Pat Michaels. The interview also mentions the double-think of the so-called skeptics in general, because they can highlight and praise this paper as being something they find easier to believe in (because of the possibility of lower climate sensitivity); even though it also makes it very unlikely that Lindzen and Spencer are right with their claims that sensitivity is even lower, i.e. under 1. So, are Lindzen and Spencer now to be dismissed by the so-called skeptics ? As soon as pigs can fly...
  16. Climategate 2.0: Denialists Serve Up Two-Year-Old Turkey
    64, Sphaerica Wow! I tried asking a polite question. Definitely did not expect such a response. I can answer your question, but I'll take the Moderator's advice before getting into a whole range of legal issues here. Perhaps someone else can answer my question.
    Response:

    [DB] Your original question:

    "Is there any site dedicated to legal matters that discusses the legal issues raised by the content of these emails?"

    You are ignoring the extremely large pink mamuk in the room: The theft of the emails was a crime currently under investigation.  Your continued focus on the content of the stolen emails is misplaced.

    Given that, Sphaerica's answer:

    "there is no evidence whatsoever of anything remotely close to criminal activity in the content of the e-mails"

    Is spot-on.

    Edit:  As is this quote from dhogaza over at RC:

    "Stealing private e-mail discussions and publicizing them is akin to bugging the supreme court during their private deliberations and releasing the recording"

  17. Memo to Climategate Hacker: Poor Nations Don't Want Your Kind of Help
    Thanks John. Good resources.
  18. Memo to Climategate Hacker: Poor Nations Don't Want Your Kind of Help
    As she surveys her small, bare plot in Zimbabwe's capital, farmer Janet Vambe knows something serious is happening, even if she has never heard of climate change. "Long ago, I could set my calendar with the date the rains started," the 72-year-old said. Nowadays, "we have to gamble with the rains. If you plant early you might lose and if you plant late you might win. We are at a loss of what to do." Paramu Mafongoya, a University of Zimbabwe agronomist, says Vambe's worries and those of millions of other poor farmers — most of them women — across Africa are a clear sign of the impact of climate change on a continent already struggling to feed itself. Changes have been noted in the timing and the distribution of rainfall on the continent. Zimbabweans say the rainy season has become shorter and more unpredictable, Mafongoya said. Climate change "is a serious threat to human life," Mafongoya said. "It affects agriculture and food security everywhere." Source: “Climate change hits Africa's poorest farmers” AP, Nov 26, 2011 To access this in-depth article, click here.
  19. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    #39 muoncounter : "That is not a little effect; it is plainly visible on the CO2 emissions curve, as are the Arab oil embargoes, the post-Gulf War recession and even the GWB recession of 2001. Zooming in further, changes in US emissions very visibly drop during these economic stress points" Oh so, we can go back to the real topic of perseus post: if (fossil-based) economic growth is the major driver of CO2 emissions' upward trend since 1850, can we break the correlation in the future (keep the growth up with CO2 down) and if we can't, should we break the growth itself? (But these core questions will probably be treated in the part 2, so may be it is better to wait for the next perseus post? I don't know when (s)he plans to post).
  20. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    Here's another look at the same graphic; this one by Ferdinand Engelbeen, via our very own Dikran Marsupial: Engelbeen also produced this graph, demonstrating a remarkably consistent slope (percentage of cumulative emissions remaining in the atmosphere) of 0.53:
  21. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    Tom C#37: "just how little major economic shocks actually effect the actual productive capacity (and production) of the global economic system." This graph (and others on more suitable scales) dispute that. "Even the great depression reduced CO2 annual emissions by only around 15%26%" That is not a little effect; it is plainly visible on the CO2 emissions curve, as are the Arab oil embargoes, the post-Gulf War recession and even the GWB recession of 2001. Zooming in further, changes in US emissions very visibly drop during these economic stress points: tamino addressed this entire question here. He models the CO2 growth curve remarkably well from a combination of the linear trend and MEI:
  22. What's Happening To Tuvalu Sea Level?
    Another thing to consider is that the human mind generally thinks in linear fashion on human timescales, which tend to be day-to-day. That makes it exceedingly difficult to grasp non-linear, or exponential changes. Like projected SLR vs that which already has occurred.
  23. Lindzen and Choi find low climate sensitivity
    An interesting contribution from the Azimuth blog, including a link to the paper, this graph and a link to an interview with one of the authors.
  24. What's Happening To Tuvalu Sea Level?
    @5 You can take any 10 year interval and see a leveling off a decline or even pink elephants. What in the "long-term rise" don't you get?? The same is true for temperatures droughts sea ice extent etc. False arguments and strawmen...
  25. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    Slight correction, during the Great Depression, CO2 emissions fell from 1.145 GTC in 1929 to 0.847 GTC in 1932, a fall of 26%.
  26. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    MA Rodger, would you please publish a graph showing: 1) The annual change in total emissions from year to year in GTC (GigatonnesCarbon); 2) The annual change in atmospheric CO2 from year to year in GTC; and 3) The annual change in atmospheric CO2 minus the change in total emissions in GTC. If you would do so, the argument between you and Sphaerica should be settled. I believe that such a graph will show conclusively that your interpretation is correct. I am unsure whether Sphaerica is misunderstanding you as saying natural variation dominates the long term trend (which is of course false), or whether he believes the short term variation in human CO2 production to be large. If the later, it would be because he is unaware just how little major economic shocks actually effect the actual productive capacity (and production) of the global economic system. Those shocks are not brought about by failings in fundamental economic capacity, but by failings in the superstructure of capitalism. As a result, unless they are left to fester (as in the Great Depression), they have little overall impact on actual production. Even the great depression reduced CO2 annual emissions by only around 15% (and hence involved only a 15% reduction in productive capacity). In terms of lost productive capacity, the Global Financial Crisis which still included massive economic growth in India and China, was barely a wimper. (This is not to downplay the real suffering it has caused for many people, but that suffering is not due to a loss of economic capacity, but due only to a loss of willingness to deploy that economic capacity by the holders of capital.)
  27. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    34, Tom, Yes. My simple complaint (without directly stating it) is that the atmospheric CO2 line appears to be detrended while the CO2 emissions line is not, and then they are presented with vastly different scales, masking the wobble in one while exaggerating it in the other. 35, MA Rodger, Picking one year is pointless. That's not how one does statistics. Honestly, your point isn't worth arguing, but you have had several posts with which to prove it and all I see evidence of there is an effort to sell your point rather than to clearly present the data. I'm not saying that you're wrong or right, I'm saying that you've used very unclear and ill-chosen graphics and numbers, with what appear to be rather arbitrary choices that wind up masking the relative factors, and so you have failed to prove your point. By this point, however, I'm simply bored with the issue. It's not worth this much discussion.
  28. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    My apologies Sphaerica @32. I never dreamt that what I'm saying here was either contentious or novel (It was however always off-topic, beginning as an innocent reply to the question @3.) So perhaps if I present a calculation of the maximum size of the blue wobbles that we should expect to see @28, that will settle this matter one way or the other (being off topic and all). If my calculation contains error, then I'm a blithering idiot and apologise. (I've no problem with that, but I'm not that often wrong.) (1)When shed of seasonal changes, the CO2 level MLO data exhibits a wobble and a rising trend. (2) The wobble's size is up to 2ppm peak to peak (as seen in graphs @12 (use left hand scale) & table @9). Less unusual in size, the 2006/10 wobble is some 0.75ppm peak-to-peak. (3) I contend that these wobbles are overwhelmingly natural. Three folk on this thread assert/suggest that I am wrong. (4) The largest variation in human emissions (twice the size of any other) is the change from 2009 to 2010 (as in red line in upper graph @8). This totals +512 - -122 = 634 million tons of carbon (or 0.634GtC). (5) Not all this carbon will remain in the atmosphere. The graph @28 uses 40% of all CO2. As land emissions are assumed for 2006-10 and treated as flat, I shall be very generous and use 60% in this calculation (so the wobble we are calculating here should be 50% bigger than the @28 graph). Thus Atmospheric CO2 wobble due to human emissions would be 0.634 x 0.6 = 0.3804 GtC. (6) It requires 2.13 GtC to raise atmospheric CO2 by 1ppm. So the 2009/10 wobble will be 0.3804 / 2.13 = 0.179ppm. (7) In comparison with the total wobble maximum p-t-p in graph @12, the maximum peak to peak wobble from emissions is thus 0.179ppm / 2ppm = 9%. The 2009/10 emissions wobble occurs during a total wobble of about 0.75ppm p-t-p, so for this one instance on the 50 year record, the human emission wobble almost manages a quarter of the total and would be less than a sixth if 40% was used in (5). The graph @28 does use this 40% & the graphed wobble is an expected 0.11ppm p-t-p. The impact on the residial wobble in the graph @28 is thus hard to spot. I do hope we can reach a resolution here in this off-topic point. (And I will leave it there without direct reply to @33 or @34) As ever, I am happy to own up to being a blithering idiot if I am in error.
  29. What's Happening To Tuvalu Sea Level?
    I don't quite follow the point of this article. The 2000-2010 sea levels from Fig 1 look pretty flat for all the islands. There is certainly a rise from 1950-2000, so what is happening over the last 10 years?
  30. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    Sphaerica @33, the black line @28 is the black line @12 minus the blue line @28. The blue line is the annual CO2 emissions scaled by 40% and reported in terms of change in ppmv to give it the same unit as the mauna loa data. As such, the two lines @28 break the annual CO2 increase into two components - a variation due to human emissions and that due to natural fluctuations. In order to do this, it is necessary that the human emissions be scaled to account for the average absorption of the emissions by the oceans and biosphere. That the 40% scaling is approximately correct is shown by the fact that the black line @28 looks like it has been detrended. As such MA Rodger's graph shows much the same information as Hansen and Sato's graph @17 except that MA Rodger shows the MEI, and also includes emissions from cement manufacture and land use change. I believe Hansen and Sato's presentation to be better. If MA Rodger was to continue graphing this data I would suggest he adopt the Hansen and Sato presentation, except showing the linear trend of the airborne fraction instead of the seven year mean. He could then show the detrended airborne fraction (mauna loa data) against the MEI, and idealy the VEI (and both together). Another interesting plot would be against the detrended global mean sea surface temperature.
  31. Climategate 2.0: Denialists Serve Up Two-Year-Old Turkey
    63, Mikel, What legal issues are you suggesting? Stealing private e-mails is a crime. Hacking into a computer system for any purpose is a crime. You can read about that anywhere. Otherwise, there is no evidence whatsoever of anything remotely close to criminal activity in the content of the e-mails, so even asking a question about it is a slight-of-hand insult. It's like asking someone "Do you still beat your wife?" Asking the question is the crime itself.
  32. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    MA Rodger, And what exactly is the point of "40% emissions subtracted?" That seems like a rather arbitrary and unnecessary adjustment. And why is this graph suddenly so very, very different from the one posted in comment 12? You have some explaining to do.
  33. Climategate 2.0: Denialists Serve Up Two-Year-Old Turkey
    Is there any site dedicated to legal matters that discusses the legal issues raised by the content of these emails? (this should not be construed as a criticism of the discussion here but I would like to separate out the legal from the scientific.)
  34. What's Happening To Tuvalu Sea Level?
    Steve, Indeed, Tuvalu has severe problems with salt water contamination of their groundwater. While there are some areas of Tuvalu that are three meters above sea level, the majority of the islands are less than 2 meters. When I visited Funafuti in 1989, there were large areas of some villages that flooded at king tides. I can only imagine how they are dealing with 10 cm more water (5.0 mm/yr times 20 years). Recent increases in wave heights cause substantial salt contamination of the aquafer by washing over the seaward sides of the island. If their stocks of ground water are contaminated they will have no water for their pigs and the coconut trees will stop producing. The recent La Nina related drought has caused stocks of rainwater (the primary drinking supply) to run low. Desalination is too expensive for the long run. How long will they be able to hold out? It is terrible. The Tuvaluans live a traditional lifestyle that they will not be able to replicate if they are forced to emigrate in masse. Tuvalu is a warning to the rest of us living in low lying areas. They do not have to be completely inundated to become uninhabitable. Miami will also run out of water (and storm drainage capacity) long before it is inundated.
  35. Lindzen and Choi find low climate sensitivity
    Perhaps the Schmittner et al sensitivity is low because their data are primarily sea surface temperatures: We combine recent syntheses of global sea surface temperatures (SSTs) from the Multiproxy Approach for the Reconstruction of the Glacial Ocean (MARGO) project and surface air temperatures over land based on pollen evidence, with additional data from ice sheets, land and ocean temperatures. The combined dataset covers over 26% of Earth’s surface (Fig. 1, top panel). In contrast to this balanced-sounding statement, the map in their Figure 1 reveals that there is actually very sparse data over land. Not surprisingly, their sensitivity is low because the find less cooling: Tropical Atlantic SSTs between 20°S–20°N are estimated to be only 2.4 K colder during the LGM in the new reconstruction compared to 3 K The MARGO 2009 results reveals an important caution, illustrated by this map: Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present.
  36. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    31, MA Rodger, If you are going to show CO2 atmospheric variation then you must also show CO2 emissions variation, and scaled proportionately to allow for a fair visual comparison. Compare apples and apples, not apples to miniaturized oranges rolling up a ramp.
  37. World Energy Outlook 2011: “The door to 2°C is closing”
    For charcoal substituting to coal, here a Hanrot et al 2009 study. Iron and steel industry accounts for 5% of total energy use, and 3-4% of GhG emissions according to Xu et Cang 2010 . Not the main issue for mitigation – if oil and coal could be used as commodities where they are strictly necessary in industrial processes rather than as energy sources for transport or electricity, it would be a great leap forward. I must emphasize (for all of us including me!) that if an energy-economy model is needful for simulating energy transitions, it is because in such discussions, we tend to poorly estimate the global quantities (requested for a certain level of production in the future) and furthermore, to add each energy solution in the mix a) without controlling that it is compatible with others in a certain land availability, b) without estimating the equilibrium cost of the energy in question and c) without ensuring that this energy can be implemented specifically where the needs (and workers!) are, or will be in 2050. Even energy-economy models have difficulties to track all the relevant factors, and this is probably one of the reasons for which they diverge in their conclusions about what we can and cannot do from now to 2050.
  38. Economic Growth and Climate Change Part 1 - Factors Influencing CO2 Emissions
    Sphaerica @29. Blue line = CO2 annual increase (or decrease), 12 month rolling average (after a fashion) x 40% & plotted as ppm of atmosphere. Thus it is a trace of annual changes in emissions. For total emissions annual change in GtC multiply by 2.5*2130. (Perhaps the line is less wobbly that you were expecting.)
  39. World Energy Outlook 2011: “The door to 2°C is closing”
    scaddenp @72, agreed that it is expensive to do it other ways. However the carbon for the CO can come from charcoal. As trees (the source of charcoal) draw their carbon from the atmosphere, iron reduction using charcoal as the reducing agent is carbon neutral. Again there is likely to be a cost in switching from coal to charcoal. I do not think it will be sufficient to have a major impact. More importantly, CO2 production in the reduction of iron is a small component of total industrial emissions and so can be one of the last areas of significant emissions reduction without significantly setting back the effort to reduce emissions. Just because something has to be done now does not mean everything has to be done now.
  40. World Energy Outlook 2011: “The door to 2°C is closing”
    Tom, you can forge with an arc furnace but it is CO that does the reduction from ferrous oxide to iron. Pretty expensive to do it other ways.
  41. Lindzen and Choi find low climate sensitivity
    If Schmittner et al 2011 low climate sensitivity depends on moderate warming from Last Glacial Maximum (LGM = peak glacial conditions) to the Altithermal (peak interglacial conditions), there will be debate among specialists. For example Shakun et Carison 2010 found a 4,9 K difference between the two periods. See also IPCC AR4 6.4.1.2 for a broader context on LGM.
  42. Lindzen and Choi find low climate sensitivity
    Sphaerica @476, I believe best estimates of the change in global temperature between the current era and the last glacial maximum are around 5 degrees C. Certainly that is the value Hansen uses in this calculation that appears to pop up in all of his papers of late: A link to a PDF of Schmittner et al can be found in my preceding post.
  43. Lindzen and Choi find low climate sensitivity
    Schmittner et al 2011 propose three possible reasons for their low climate sensitivity, or which the first is low estimates for the difference in temperature between the current era and the LGM:
    "We propose three possible reasons why our study yields lower estimates of ECS2xC than previous work that also used LGM data. Firstly, the new reconstructions of LGM surface temperatures show less cooling than previous studies. Our best estimates for global mean (including grid points not covered by data) SAT and SST changes reported above are 30–40% smaller than previous estimates (21, 23). This is consistent with less cooling of tropical SSTs (–1.5 K, 30°S–30°N) in the new reconstruction (12) compared with previous datasets (–2.7 K) (24). Tropical Atlantic SSTs between 20°S–20°N are estimated to be only 2.4 K colder during the LGM in the new reconstruction compared to 3 K used in (23), explaining part of the difference between their higher estimates of ECS2xC and ΔSATLGM (–5.8 K)."
    If there estimates of LGM temperatures where equivalent to past values, that would increase their estimate of climate sensitivity by about 50%, giving a climate sensitivity of around 2.5 to 3.9 (lower median of 3.45). Therefore Schmittner et al presents us with a dilemma. If they are correct about temperatures then climate sensitivity is lower than previously thought, but the impact of a given change in temperature is also much greater than previously thought. Alternatively, if they are wrong about temperatures, then their estimate of climate sensitivity is a significant under estimate, and the data actually supports a higher climate sensitivity than currently expected. Of these two possibilities, the second seems more likely. If the impacts of temperature are greater (as with the first alternative), then surely the feedbacks for a given temperature change are also greater contrary to that hypothesis. However, as always, more study will be needed to resolve the issues raised. Whatever the outcome, this is not a paper that can be considered conclusive, and nor is it capable of a simple interpretation. Unless, of course, you are prepared to declare all other papers on this and related topics wrong by fiat, solely on the basis that this paper suits your prejudices.
  44. Lindzen and Choi find low climate sensitivity
    I'm a little confused... without seeing the paper, how can a temperature swing of 10-12˚C since from LGM to present, with an increase of CO2 from 180 to 280... less than a doubling... translate into a climate sensitivity of 2C, or even 3C? Is the paper saying that most of that change was the result of orbital forcings, or that the bulk of the change is so asymmetric compared to today that very little of that will be felt? Is there a link to an open copy of the paper anywhere?
  45. Lindzen and Choi find low climate sensitivity
    I haven't still read the paper, but a 2,3 K sensitivity is among the IPCC range and three models of the IPCC AR4 find a 2,1-2,3 K sensitivity for 2xCO2. So, that one study among many others arrives to the same conclusion from a LGM reconstruction is not a surprise, and certainly not the last word in a domain where there are many publications each year. #474 skywatcher : do you think to sea level rise? If it is the case, I don't know if a 3.3 K warming on a glacial condition will have the same effect that a 3,3 K warming on an interglacial condition (like ours). Intuitively, I'd say there was much more ice to melt 20ka ago than now, at mid latitude and low altitude. We should observe what semi-empirical ice models obtain with an imposed 2,3K sensitivity.
  46. Climategate 2.0: Denialists Serve Up Two-Year-Old Turkey
    Skywatcher @61, not only had Watson been a chairman of the IPCC, the supposedly damning email was written in January of 2001, ie, while he was chairman of the IPCC. This highlights the desperation of the deniers on two points- That they would consider it untoward that a highly qualified chairman of the IPCC should have input into the writing of the IPCC Summary for Policy Makers; and That they are dredging up eleven year old emails to prosecute their case. Seriously, where it not for the fact that there is a "sucker born every minute" and that those suckers get to vote, the only suitable response to WUWT would be gales of laughter.
    Moderator Response: [Albatross] Fixed hyperlink tag.
  47. Lindzen and Choi find low climate sensitivity
    #473 oneiota, I think there's an SkS article in the pipeline about the relevant paper, but in this case it is intriguing to see what skeptics consider supports their position. This paper does not support their position at all, but I don't think they realise why. The paper uses a climate model to estimate a relatively low climate sensitivity - the climate model in question has a remarkably low temperature difference between LGM and present conditions (3.3C) compared to published estimates usually towards 5C or more. The consequence of this is that the paper implies a much greater impact on the climate system for every degree of warming. Although it suggests fewer degrees C per doubling CO2, we'll also need fewer observed degrees C to create a climate change as large as LGM to present. And we're already well on the way to doing that, if this paper is correct. To me, that make for particularly worrying reading, and not a cause for optimism, as various news outlets, including the BBC, have implied.
  48. What's Happening To Tuvalu Sea Level?
    When I started reading this article, I thought the "Tuvualuans have claimed detrimental sea level rise already" aspect would centre on salt infiltration of their ground water. The article was excellent, and Rob has done a good job describing the basics of sea level estimation. (I'm learning here, thanks.) But I wonder, what about measuring salinity in coastal aquifers. Obviously the modeling for the purposes of estimating sea level rise would be quite difficult. But in terms of detecting important impacts, wouldn't that be a helpful thing to monitor?
  49. World Energy Outlook 2011: “The door to 2°C is closing”
    An interesting article in Science (Express) by Williams et al. . The abstract : "Reducing greenhouse gas emissions 80% below 1990 levels by 2050 is the subject of vigorous policy debate but there has been little physically realistic modeling of the energy and economic transformations required. We analyzed the infrastructure and technology path required to meet this goal in a specific economy (California), using detailed modeling of infrastructure stocks, resource constraints, and electricity system operability. We find that technically feasible levels of energy efficiency and decarbonized energy supply alone are not sufficient. Rather, widespread electrification of transportation and other sectors is required. Decarbonized electricity becomes the dominant form of energy supply, posing challenges and opportunities for economic growth and climate policy. The transformation demands technologies that are not yet commercialized and coordination of investment, technology development, and infrastructure deployment." Their results from the Californian case (world’s sixth largest economy and 12th largest emitter of GHGs, per capita GDP and GHG emissions similar to those in Japan and Europe), converge with IEA WEO 2011 we're discussing : reducing 2050 emissions 80% below the 1990 level would imply to include nuclear power and CCS in the mix. Their energy scenario needs three steps : "Three major energy system transformations were necessary to meet the target (Fig. 2). First, energy efficiency had to improve by at least 1.3% yr−1 over 40 years. Second, electricity supply had to be nearly decarbonized, with 2050 emissions intensity less than 0.025 kg CO2e/kWh. Third, most existing direct fuel uses had to be electrified, with electricity constituting 55% of end-use energy in 2050, compared to 15% today." As for the IEA WEO scenario, sustained gains in energy efficiency are the necessary condition of success : "The rate of EE improvement required to achieve the target and enable feasible levels of decarbonized generation and electrification—1.3% yr−1 reduction relative to forecast demand—is less than the level California achieved during its 2000-2001 electricity crisis (22), but is historically unprecedented over a sustained period."
  50. World Energy Outlook 2011: “The door to 2°C is closing”
    "I don't know to which post by Perseus you refer" : This one . For Germany, see for example recent articles from Spiegel , either on cost of wind electricity from Baltic or on environmental and aesthetic concern about high voltage lines . Of course, it is not a technical problem per se. But as we translate the 2K/450 ppm objective in real energy decisions, there will be more political debates of this kind. (And, in my opinion, more pressure toward climate modellers and energy-economy modellers for reducing their remaining uncertainties.)

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