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Comments 67851 to 67900:

  1. The Media & Global Climate Science Communication
    Thanks for an interesting article Brian. It will be interesting to compare this study of the reporting of climate policy with the soon to be released study of the reporting of climate science. I expect the results will make the Australian print media look rather dismal.
  2. The Media & Global Climate Science Communication
    I think the political situation in Australia with respect to AGW is quite different to that in US. Here, not only the gov but also the opposition accept that the globe is warming and that sth must be done about it. If you look at the liberal policy here you find not a single word denying the climate science. The disagreement is only about the policy: liberals favour their "direct action" and try disproving the carbon tax method being implemented by govs. If Tony Abbott digress sometimes that "science is not settled yet", that's because Tony's mind is influenced more by some external events like 'lord' Monckton speaches rather than his own reasoning. Look at other liberal leaders, like Malcolm Turnball for more reasonable representatives. So, this report, as confirmed by Brian, is about the climate policy. The one about climate sicence will be different. IMO.
  3. Foster and Rahmstorf Measure the Global Warming Signal
    #37 Sphaerica : AMO, on the other hand, is a black box. We're not even sure that it really is periodic or even exists at all. It may be a mere artifact of coincidence with actual, distinct forcings that in the past 100 years first temperatures down, then up (increase in TSI), then down (increase in human aerosols overpowering GHGs) and then up again (less aerosols, more GHGs) in a seeming cycle that does not actually exist. We have logical evidence to accompany changes in global temperature, and the AMO then mirrors those changes in global temperature. I suggest you're a bit "extreme" in your presentation of AMO. IPCC AR4 3.6.6 (2007) has presented the AMO among other "patterns of atmospheric circulation variability", including the Southern Oscillation, and what I read here from climate scientists is not exactly what you say. I mean, there are 17 years of publication on AMO since the first description in Schlesinger and Ramankutty, 1994, so it not just "a black box". Furthermore, if your prefer to speak about other patterns, why not : my question would be valuable for the better defined NAO or NAM, for example. I've no fixed idea on AMO. My point is a question of logical coherence rather than empirical evidence on such or such oscillation. If you think that oscillations (or patterns of variability or teleconnections) do not change surface temperature on long term, beyond interannual variability, you have no particular reason to include any oscillation in a 32 yrs analysis. It will oscillates around the zero mean on such a long period, by definition. This is quite independent of our exact level of understanding about ENSO, AMO, NAO, and so on. But if you include one oscillation, you must at least explain the statistical / physical reasons for excluding all the others. Why would one then go looking at the AMO as a cause rather than an effect? In fact some scientists do. So you should ask to them, not to me! For example in J Clim, Ting 2010 : "Comparing the results to observations, it is argued that the long-term, observed, North Atlantic basin-averaged SSTs combine a forced global warming trend with a distinct, local multidecadal “oscillation” that is outside of the range of the model-simulated, forced component and most likely arose from internal variability. This internal variability produced a cold interval between 1900 and 1930, followed by 30 yr of relative warmth and another cold phase from 1960 to 1990, and a warming since then." (My emphasis on produce) Also in J Clim, DelSole 2011 : "An unforced internal component that varies on multidecadal time scales is identified by a new statistical method that maximizes integral time scale. This component, called the internal multidecadal pattern (IMP), is stochastic and hence does not contribute to trends on long time scales; however, it can contribute significantly to short-term trends. Observational estimates indicate that the trend in the spatially averaged “well observed” sea surface temperature (SST) due to the forced component has an approximately constant value of 0.1 K decade−1, while the IMP can contribute about ±0.08 K decade−1 for a 30-yr trend. The warming and cooling of the IMP matches that of the Atlantic multidecadal oscillation and is of sufficient amplitude to explain the acceleration in warming during 1977–2008 as compared to 1946–77, despite the forced component increasing at the same rate during these two periods."(my emphasis) I've no idea of the value of these studies, but they suggest internal variability (and particularly AMO here) can be something like the cause of some mutlidecadal warming / cooling. That's why I speak previously of a debate among climate community on the origin, cause and effect of these oscillations, and particularly on relatively short period like 1979-2011. See also Latif and Keenlyside 2011 for a recent review on decadal climate variability and predictability.
  4. Foster and Rahmstorf Measure the Global Warming Signal
    36, skept.fr, To put it another way, you find a bullet embedded in the wall. You trace the angle of entry, look across the room, and see a smoking gun lying on a table. You now conclude that the bullet must have thrown the gun across the room onto the table. The correlation between the two is obvious. The expectation of cause and effect is absurd.
  5. Foster and Rahmstorf Measure the Global Warming Signal
    36, skept.fr, You also neglect the fact that much of the mechanics of ENSO are understood. We know, physically, what happens to cause the warming and cooling. We don't yet know what controls the transition between states so we can't predict when any state will appear or how strong it will be, but we do understand how and why it affects temperatures, and this allows us to understand that it could not possibly have a long term effect on global mean temperature. AMO, on the other hand, is a black box. We're not even sure that it really is periodic or even exists at all. It may be a mere artifact of coincidence with actual, distinct forcings that in the past 100 years first temperatures down, then up (increase in TSI), then down (increase in human aerosols overpowering GHGs) and then up again (less aerosols, more GHGs) in a seeming cycle that does not actually exist. We have logical evidence to accompany changes in global temperature, and the AMO then mirrors those changes in global temperature. Why would one then go looking at the AMO as a cause rather than an effect? This has nothing to do with statistics. It has to do with misinterpreting the correlation and so putting the cart before the horse.
  6. The Media & Global Climate Science Communication
    I am amazed at these statistics. Julia Gillard is an unusually courageous politician to take on this type of print media opposition. It is surprising that climate change science retains a hold on the Australian public. Is this repeated in other media? Or have bloggers and science communicators been unusually effective by other means?
  7. The End of the Hothouse
    A quick look at GeoCarb revealed another tool that I had forgotten - Sr isotopes as a proxy for weathering rate. eg this paper. Quite definitely a himalayan signal here.
  8. The Media & Global Climate Science Communication
    Thanks Brian and also John for the interesting links.
  9. Arctic settles into new phase – warmer, greener, and less ice
    John et al, thank you for the additional lecture. Btw I noticed the authorship of the title but only responded to the title's content. #18, that's what is sharpening the annual cycle of anomalies. Catastrophe theory (the mathematics/physics interpretation) is imo a useful concept. E.g. around a threshold average thickness below which, in summertime, ice cover breaks up and melts vastly more quickly. Positive feedback like open sea area, menacing the protective fogs and low stratus over the pack.
  10. Foster and Rahmstorf Measure the Global Warming Signal
    #34 Stephen - Sorry, I miss your second point : "On a more abstract statistical level, it's a little problematic trying to fit a cycle with a period twice as long as temperature record being used. It's also hard to know how to correct the AMO for the influence of AGW without seeming a little arbitrary. " I think this point partly answers my question: a purely statistical approach has no tool for a physical detection-attribution (contrary to climate models, like Huber et Knutti 2011), so its prior assumptions for detrending must rely on robust features in literature. ENSO is considered as the principal mode of high frequency variability for surface / LT trends (for the moment with a null hypothesis concerning an effect of GHG forcing), whereas AMO is still under discussion.
  11. The Media & Global Climate Science Communication
    AussieinUSA - the charts show negative/positive policy response. There is a second report due out soon on climate science coverage. Details are in the study.
  12. The Media & Global Climate Science Communication
    Chris Mooney is also a regular contributor on DeSmog Blog. Most of his posts focus how climate science is communicated and how it is received – particularly in the USA. His most recent DeSmog Blog post “The Climate-Media Paradox: More Coverage, Stalled Progress” is particularly provocative when juxtaposed with Brian Purdue’s excellent article. To access Mooney’s “The Climate-Media Paradox: More Coverage, Stalled Progress”, click here.
  13. Foster and Rahmstorf Measure the Global Warming Signal
    #34 Stephen Here is a AMO index (c) which is calculated as a substraction of (a) global STT anomaly from (b) NA SST anomaly, image from the Knudsen 2011 paper. So, concerning the anomaly we're debating, AMO is supposed to exhibit a warming trend from beginning of the 1990s to the present period, with no particular trend for 1979-1990. I don't understand why this signal, relative to one basin and not all the hemisphere nor the globe, would be immediately identifiable in the detrended global signal from FR2011. I think it is your point (if I correctly understand) but in fact, we've just here a local warming trend (AMO or North Atlantic STT) in a global warming trend (global T). If this trend is partly natural ("noise" in the FR2011 sense), to remove its natural part permits to gain the correct forced signal. A natural (unforced) part of AMO would probably be a low value in the global mean. My point is not to say a huge part of warming come from AMO (non sensical), or any other oscillation in particular, but to understand the rationale for detrending natural variability in three decades series (that is to assess what is natural variability and what is forced variability, even if a particular oscillation just produces 0,01K/dec, for example). As I said in #13, I think FR get the broad picture correctly with their choices, but details are still amazing for me (either the ENSO independency from forcings or the other "Os" except ENSO).
  14. The Media & Global Climate Science Communication
    Chris Mooney hit the nail squarely on the head when he wrote: “You can follow the logic to its conclusion: Conservatives are more likely to embrace climate science if it comes to them via a business or religious leader, who can set the issue in the context of different values than those from which environmentalists or scientists often argue. Doing so is, effectively, to signal a détente in what Kahan has called a ‘culture war of fact.’ In other words, paradoxically, you don't lead with the facts in order to convince. You lead with the values—so as to give the facts a fighting chance.” Source: “The Science of Why We Don't Believe Science: How our brains fool us on climate, creationism, and the vaccine-autism link,” by Chris Mooney, Mother Jones May/June 2011 Issue To access Mooney’s insightful article, click here
  15. The End of the Hothouse
    "The science on this subject is very clear. There is every scientific reason to dismiss claims that CO2 drop triggered the temperature drop of the Southern Ocean and Antarctica. Well I find the "science" somewhat lacking. Faced with Hypothesis 1 - development of ACC caused sufficient ocean cooling to draw-down CO2; and Hypothesis 2 - increased weathering from orogenesis caused CO2 drawdown, the scientific approach would be look for data that could separate them. Off the top of my head, I can think of a couple of things to check. Firstly, as others have done, there is the question of timing. Which event preceded the CO2 drop? Second, if ocean cooling was cause of CO2 drop, then do ocean temperature proxies support sufficient cooling to match the CO2 draw down? Since the same core would yield both the CO2 proxy and temperature proxy, then dating shouldnt be a major issue. Finally, if orogenesis is the cause, then a proxy for weathering would be sediment flux into ocean basins (if you are eroding then the sediment has to go somewhere). My own databases on the basins do not have sufficient time resolution to answer this (oh for some more funding), but I would imagine that the basins are sufficiently well known to at least do a back-of-the-envelope calculation. Sadly full-blown sedflux studies are very expensive but its possible that data is there. GeoCarb III might have done this - bound to have tried it at first order anyway. Both approaches require arithmetic rather than handwaving. I would find this more convincing.
  16. Foster and Rahmstorf Measure the Global Warming Signal
    BTW...much of my reasoning for discounting the effect of the AMO can also be applied to the PDO, which has exhibited several distinct shifts since '79 - including a late 90s shift to an extended negative phase. None of those shifts are apparent in the corrected temperature data in F&R. And again, the exact mechanism by which the PDO would affect global temperatures is not clear to me. Again, maybe others can help me there.
  17. Foster and Rahmstorf Measure the Global Warming Signal
    skept.fr My point @9 is that, were the AMO index influencing global temperature, the evidence for such an effect should have become clearer after Foster and Rahmstorf statistically removed the influence of other factors from the times series. All of those other factors have very distinct temporal signatures from the AMO index and could have obscured the influence of the AMO. However, there is no apparent trace of the AMO in the temperature data once those factors have been accounted for. The AMO index shifted sharply from a cold to warm phase starting in the 90s (see the Knudsen 2011 paper). By contrast, F&Rs corrected temperature series during the 90s shows a steady linear increase. There is not even a hint of a change in rate of warming during and after the 90s, as would be expected were the AMO important. On a more abstract statistical level, it's a little problematic trying to fit a cycle with a period twice as long as temperature record being used. It's also hard to know how to correct the AMO for the influence of AGW without seeming a little arbitrary. From what I can tell that's because we don't understand it well - it's not even clear to me that there is a consensus that it is actually a regular feature of the ocean-climate system. On a more general level...I understand the mechanism for how ENSO affects global balance of heat distribution between the atmosphere and the ocean - through its effect on intensity and distribution of deep water upwelling. But, what is the mechanism proposed for any influence of the AMO on global atmopsheric temperatures? Is there one? As far as can tell it's just an SST index. Is it supposed to be related to the intensity of meriodional overturning circulation, or some other process that could affect storage of heat in the ocean?
  18. Foster and Rahmstorf Measure the Global Warming Signal
    skept.fr Certain statistical conventions in scientific publication aren't necessarily the best means of determining the 'weight' of evidence. Foster illustrates that when this particular event (which appears to pass the 99% 'significance' level) is given more context, it doesn't seem quite as compelling (roughly 7 times less compelling). The difference between 95% and 93% should not simply be the difference between yes and no. Unfortunately a lot of university courses teach just that.
  19. It's the sun
    dana, Here is a slightly different version of your Figure 3 (in the advanced rebuttal) from a slide talk by Dr. Nathan Schwandron, a professor/researcher in space and plasma physics at the University of New Hampshire. The peak value was in the early 80s. The figure shows a compilation of 45 years of satellite-era total solar magnetic flux (Note: that is not the same usage of flux as in radiative flux (Watts/meter2); it is magnetic field flux, Phi-B = B.A, where B is field strength in Tesla, A is a cross-sectional surface area and . is dot product. Phi-B is thus measured in webers = Tesla meter2). Dr. Schwandron demonstrates that magnetic field flux is an excellent proxy for solar corona temperature - which dropped precipitously during the cycle 23/24 minimum of 2009. The reduced magnetic field flux has also driven the strength of the IMF (inter-planetary magnetic field), as measured at the earth, to a deep low. This point from Dr. Schwandron's talk is very interesting: Space age context shows 1970’s also an era of lower coronal temperatures We know that the 70s was a cool decade (and not just because of all this cool stuff). The reconstructed solar coronal temperature shows 2005-2009 to be even cooler. And yet, and do not show this cooling (on earth) in any way, shape or form. So no, it's not the sun.
  20. The Media & Global Climate Science Communication
    Quick question regarding the graphs......'Negative' means that it is anti-AGW article?
  21. Foster and Rahmstorf Measure the Global Warming Signal
    #30 Tom Curtis : OK, that's not rhetoric, I'm not specialist at all of statistics, so I neglected the nuance between 93% / 95% confidence. You're right. But from the exchanges between Tamino and the authors, I understood they agree that the method used by Knudsen is a kind of standard in the literature, even if too imprecise. Dr Knudsen : "We are not completely happy about this way of describing significance. It may easily create a feeling by the average reader that significances are higher than they really are. But we have adhered to this standard used in other literature on the subject." Tamino answer : "Honestly, I agree that their approach is perfectly valid, and that it is in accord with the way this kind of analysis is treated in the literature. I’ll also agree that it is easy for these results to be misinterpreted." So, for a layman (again, I'm dull in that matter), the point is totally unclear, if Knudsen et al did what is usually done in paleoclimate or oscillation studies, does it mean that Tamino critics would lessen significance of most results in theses fields? Anyway and beside Knudsen 2011, there are currently many discussions on AMO periodicity (or reality) on different timescales, for example Vincze 2001 , Marullo 2011 , Wyatt 2010, etc. (A lot of hits in Google Scholar, just give here some recent results about these discussion, I think the first one from Vincze is a pdf of interest for persons with a good knowledge of statistics.) So, for my initial point, unless there is a clear proof that AMO signal is an artifact, or 100% produced by AGW, or without any effect on a 32 years period of T, I suggest the opportunity of removing or not removing this signal could be a matter of debate among climate community. Would you agree with this cautious conclusion or do you think I still miss a point that justifies with certainty or near certainty the ignorance of AMO as a partial noise (like ENSO but not with the same magnitude and not the same statistics of lag/lead response to T)?
  22. The End of the Hothouse
    TIS @23, thankyou for the correction on the Drake Passage (and serves me right for relying on my faulty memory). With regard to your two hypotheses, the first Antarctic glaciation occurred 34 million years ago, at which time CO2 levels had fallen from less than 1000 ppmv. At that time, the Drake Passage looked like this: Although there is some evidence of Pacific water flowing through to the Atlantic at that time, there is no evidence it was anything but surface water passing through narrow channels. In the words of Lyle et al, 2007:
    "The Antarctic Circumpolar Current (ACC) is a key feature of the Southern Ocean. Its development may have helped cool Antarctica and initiate Southern Hemisphere glaciation. The deep circulation of the ACC must have been established after both the Tasman gateway (between Antarctica and Australia) and the Drake Passage (between South America and Antarctica) opened. However, estimates for ACC initiation range over 20 m.y., from the middle Eocene to early Miocene. A new piston core of upper Oligocene to Holocene sediments from the South Pacific has allowed us to delimit the formation of the ACC to the late Oligocene (ca. 25–23 Ma). Upper Oligocene, current-worked sediments and a hiatus to the upper Miocene result from the beginning of the modern ACC flow; i.e., when strong currents and mixing throughout the water column were established. Previously published Nd isotope data date the first intrusion of Pacific water into the Atlantic much earlier. The discrepancy with our results can be reconciled by the different methods measuring different flow regimes. Tracer methods such as Nd are sensitive to relatively small and shallow incursions of water, whereas pelagic erosional regimes require vigorous deep flow."
    (My emphasis). By 25-23 million years ago, the first time for which we have firm evidence of a circumpolar current, the Drake Passage looked like this: And here is the full progression of its development: So, on the evidence, Hypothesis 1 is that the geography of the Earth changes so as to cause a change in ocean currents, which causes the CO2 levels in the atmosphere to decline 10 million years before hand, by amounts which exceed the capacity of oceanic temperature changes to account for. Personally, I prefer the real hypothesis two, not your strawman version, ie, that mountain building in the Rockies and Himalayas results in increased erosion, which results in increased sequestration of CO2, thus drawing down CO2 levels over a period of millions of years.
  23. The End of the Hothouse
    TIS#23: "The science on this subject is very clear. " So a hand wave is sufficient to dismiss the content of the paper that is the subject of this post. Perhaps that is because it is necessary to be dismissive of this particular point, rather than be truly skeptical. As noted here, this paper and prior work by the authors suggest that if CO2 drove temperature drop, it becomes very difficult to avoid a re-examination of the CO2-lags-temperature meme. A meme that is vital to pseudo-skeptic posturing over 'its not CO2.' BTW, if you look into that, the uncertainty in dating CO2 in ice cores is quite large (an oft-quoted lag of 800+/-600 years ought to make any true skeptic curious). Or is 75% uncertainty good enough for what passes as 'very clear science' in the world of pseudo-skepticism?
  24. Foster and Rahmstorf Measure the Global Warming Signal
    skept.fr @29, with respect, Tamino's purpose in 8000 years of AMO blog post was specifically to dispute the statistical significance of the results. He writes:
    "Although their results are both correct, and computed according to standard practices, an extreme caveat applies. A result which is reported as passing 99% significance, does not mean that it’s actually a 99% confidence periodic result! It would be, if and only if the test were applied only to a single, precisely determined, pre-defined test period. But the spectral analysis tests a wide range of periods (i.e., of frequencies), covering at least the plotted frequency range from 0.01 to 0.02 cycle/yr (periods from 50 to 100 yr). This means that there are lots more chances to get an apparently “significant” result — just by chance."
    (Original emphasis) Later he analyses one "apparently significant result", and finds:
    "But what are the odds of finding a peak that strong when we scan the frequency range from 0.01 to 0.02 cycle/yr? I generated 500 white-noise data series with the same time sampling as the Agassiz d18O data from 6000 to 8000 yr BP. Then I computed the strength of the strongest peak in the DCDFT spectrum over the frequency range from 0.01 to 0.02 cycle/yr. This sample of 500 simulated noise spectra enabled me to define the probability distribution for the strongest peak in this case, and therefore to define the true significance level for the result from the Agassiz ice cap. It turns out that the peak which passes 99% confidence for a single-frequency test, is only significant at 93% confidence when taken in the context of having scanned a range of frequencies."
    By convention, of course, results are only considered statistically significant if they are significant at 95% confidence level, so the Agassiz ice cap data for a 68 year period between 6 and 8 thousand years ago is tantalizingly close, but it is not statistically significant. Tamino continued:
    "I did similar tests (defining the probability distribution for the tallest peak by Monte-Carlo simulations) for the entire time span of the GISP2 d18O data. It turns out that all the plotted results fail to pass 90% significance except for a brief outburst of the 63-yr band between 6500 and 7000 yr BP."
    In the face of this specific technical discussion, I think taking once rhetorical turn of phrase as defining Tamino's opinion is not warranted.
  25. Foster and Rahmstorf Measure the Global Warming Signal
    #27 Tom You’re right for AO ! (Decidedly, acronyms are perturbing for readers.) For AMO, I slightly disagree with your interpretation of Tamino-Foster point concerning the long term (8000 yrs for Knudsen et al. 2011) trend. In fact, as your link shows, Tamino concludes: «I will emphasize that the results are less “significant” than they may appear at first sight, so they should be treated as more tentative than definitive.» But this does not mean that there is «no statistically significant evidence of quasiperiodicity» (your point). So, the basic result of Knudsen (distinct ~55- to 70-year oscillations characterized the North Atlantic ocean-atmosphere variability over the past 8,000 years) is not contested, its statistical robustness is rather relativized by Tamino analysis. This 55-70 yrs AMO periodicity, if it really exists and is not a statistical artifact (to be confirmed, so), would imply the signal-noise analysis of 1979-2011 (32 yrs) period have to deal with it. The other Tamino-Foster article you linked (T leads AMO whereas ENSO leads T) probably explains the choice to include ENSO and ignore AMO in FR2011. But as the graph shows, peak correlation for the 2 months lag is just 0.4 and the distribution of time series suggest sometimes T lags AMO. Maybe this ‘sometimes’ is part of natural periodicity discussed in the previous point?
  26. Foster and Rahmstorf Measure the Global Warming Signal
    Arkadiusz Semczyszak, even in Polish, 1979-2010 does not equal 1901-2000. Therefore Viereck's claim is entirely consistent with Foster and Rahmstorf's result. Assuming they are consistent, we would expect (relatively) large increases in TSI prior to 1980, with a (relatively) small decline after 1980. And that indeed is what we see:
  27. Foster and Rahmstorf Measure the Global Warming Signal
    skept.fr @24, as you correctly not Tamino (Foster) discusses the Atlantic Multidecadal Oscillation (AMO) on his blog. He has shown that the AMO is just detrended North Atlantic Sea Surface Temperature (SST) Anomaly, and that there is little evidence of anything more (your link). However, he has also shown that there is no statistically significant evidence of quasiperiodicity in the variations in North Atlantic SST of over the last 6000 years. He has also shown that the AMO lags temperatures land temperatures, rather than leads them, arguing against a causal role for the AMO. In his words:
    "Now the peak correlation is at lag -2 months (again temperature leads AMO) and the difference from the lag 0 correlation is larger. I think this suggests two things. First, ... Second, the argument against causality from AMO to temperature is stronger. It’s still very weak — but based only on the time series, the argument for causality is even weaker."
    In fact, rather than causality, I would suggest the lag is simply a consequence of the quicker response time of land surface temperatures relative to SST for a given forcing. With regard to the Pacific Decadal Oscillation (PDO), when Tamino first performed this analysis for his blog, the PDO was brought up in comments, so Tamino regressed against the PDO as well. The PDO did not show any significant effect. I believe only the AMO and PDO have been suggested as causes of a (purportedly) spurious anthropogenic warming signal by deniers. As a side note, AO is often used to refer to the Artic Oscillation, so its use to refer to Atmosphere/Ocean circulations while discussing various oceanic "oscillations" can be confusing.
  28. Foster and Rahmstorf Measure the Global Warming Signal
    For the record: I have great admiration and respect for Dana's analytic and communication skills. My apologies to him and to all for going overboard in making a point about the need to define scientific acronyms and terms.
  29. Foster and Rahmstorf Measure the Global Warming Signal
    PS : "LT T trend" better than "Ts trend" for Santer et al 2011. (For the acronyms, LT = lower troposphere, Ts for surface temperature).
  30. Foster and Rahmstorf Measure the Global Warming Signal
    #17 scaddenp # 19 skywatcher On his blog , Tamino have explained for example that the AMO signal is nothing but the AGW signal (so there is a trend) as North Atlantic temperature trend results of forcing : "Therefore global warming is the cause, not the effect, of much of the variation in the AMO". But why this would be true for AMO and not for all the other "O" including ENSO? Forcings and feedbacks act permanently on lapse rate, clouds, surface and vertical temperature profiles, wave propagation, etc. so I see no physical reason to suggest the frequency / intensity of oscillations will not be affected. Even a negative trend on a particular basin could be interpreted as a local and temporary effect of negative feedbacks – at least ‘theoretically’, this is what an AOGCM model is needed to analyse the possibility and probability of such event. You're right, models have no convergence on ENSO as recall Vecchi et Wittenberg 2010 for example : "the extent and character of the response of ENSO to increased in greenhouse gases are still a topic of considerable research, and given the results published to date, we cannot yet rule out possibilities of an increase, decrease, or no change in ENSO activity arising from increases in CO2. Yet we are fairly confident that ENSO variations will continue to occur and influence global climate in the coming decades and centuries.". Also of interest for readers Pierrehumbert and Benestad's point on Real Climate . For PDO, I've no particular information. Anyway, PDO, ENSO and AMO are probably not the only modes of variability (I’m pretty ignorant about the details of what climate scientists consider as ‘real’ quasi-periodic oscillations and their teleconnection in AO circulation). For example, Swanson and Tsonis 2009 have analysed what they called "shifts" in multidecadal variability (see Swanson’s op-ed on Real Climate) and M. Latif have some similar conclusions with GEOMAR model's team (see this page for GEOMAR publications, with many articles on this variability either natural or forced, particularly the Atlantic basin). That's why, for a period like 1979-2011 rather than a long term analysis 1900-2100 for example, I see the very precise distinction between noise and signal as a difficult exercise. There are many other convergent lines of evidence to consider the ~0,15 K /dec signal as the very likely result of GHGs forcing, but to say for example this GHG decadal signal is really 0,15 K rather than 0,11 K or 0,19 K seems to me very difficult, the removal of MEI-TSI-AOD noise being just a broad approach for that. And even without statistical work on signal and noise, we know that the stability of Ts trend in the 2000s is not a problem for AOGCMs, as they can obtain in their runs 17 years without trend (Santer el al 2011).
  31. It's not bad
    Under "Sea Level Rise" it would be good to specifically mention coastal erosion. Rising sea level threatens not just those who will find themselves beneath the waves, it also threatens those atop the tall cliffs. Basically rising sea level changes the mass balance of sediment on beaches. By creating new room ("accommodation space") for sediment storage, sea level rise can quickly drain a beach of sediment, exposing the surface protected by the beach. Also it obviously provides more ready access for storm waves to the base of erosional bluffs. To better understand the messy nature of marine transgression during sea level rise, one could look to areas where subsidence has simulated this effect such as on the Mississippi delta (size warning - 2 mb pdf): I don't know of a nice paper that looks at cases like this and uses it as an analogy for climate-change related sea level rise.
  32. The End of the Hothouse
    I'll also quote from the end of Anderson et al 2011 (link in text of post above): "Whereas changing atmospheric CO2 concentrations undoubt- edly contributed to the abrupt cooling that occurred across the Eocene/Oligocene transition, continued cooling and gla- cial expansion in the AP region is best explained by gradual de- velopment of ocean passages, extended isolation of the continent, and development and expansion of the Circum Antarctic Cur- rent. The formation of a complete circum-Antarctic passage has been a continuous process spanning the past 50 million years. That's as up-to-date as I can find.... Cheers - John
  33. The End of the Hothouse
    Here's a fairly recent summary of research into the development of the ACC following the opening and then deepening of the Drake Passage: http://geoweb.princeton.edu/people/swanson-hysell/Papers/Barbeau2009a.pdf I'll just quote the final paragraph of the discussion therein: "While an open marine gateway between South America and Antarctica is required for the development of the ACC, evidence of a zenith of Eocene tectonic activity in the Scotia arc alone is insufficient to constrain the ACC onset that may have caused or contributed to Oi-1 glaciation because of the significant sill depths required to allow such circulation (Livermore et al., 2007). However, the ~5 Myr lag between the timing of the provenance shift recorded herein (ca. 39 Ma) and the Oi-1 glaciation (ca. 34 Ma) may have allowed time for the development of sufficient sill depths. The sediment provenance data and kinematic interpretations presented herein are temporally consistent with independent evidence of a middle Eocene onset of Drake Passage opening (Scher and Martin, 2006). Whether sufficient opening and associated subsidence occurred to allow ACC development in time for the Oi-1 glaciation remains to be seen. Considering the ACC's dominant influence upon modern global ocean circulation and temperature distribution (Barker, 2001), constraining the timing and nature of its onset remains vitally important. It appears that at least one part of the gateway's development involved the Eocene kinematics of the Fuegian Andes." Note the caution expressed in this. As ever, more research is needed! Yes, it is also possible that increased oceanic CO2 drawdown was a factor - but until we have a more definitive timing for the onset of the full ACC then it remains a "possible". However, what we DO know is that at full-on Eocene CO2 levels, i.e. 1000-1500ppm, the planet is ice-free, so we ought not to be heading anywhere in that direction! Cheers - John
  34. Dikran Marsupial at 20:28 PM on 20 December 2011
    Sea level fell in 2010
    mace@14 Scientific discussion is best served by having a high signal to noise ratio, so sanity checking theories before putting them forward (or better still performing some background research) is vital in making sure that ones contributions are signal rather than noise (which is why I only contribute to discussions where I have some background and merely lurk on discussions where I don't). It takes a long time to understand even the basics, so reading the articles on SkS before posting is a good idea. If in doubt, posing the theory as a question is probably a better approach, e.g. "what effect has the recent floods in Australia had on global mean sea level?". There is nothing wrong with not knowing the answers to such questions (I would deinitely defer to Tom on this one!). It is true that other countries have had floods this year, however I suspect that is true of most years (the places in question may vary from year to year), and that the volume of the oceans means this variability has relatively little effect on sea levels. In guaging the effect of these floods on mean sea level, we ought to extend the discussion back in time to get an idea of what effect we should expect to see (I don't know the answer to that).
  35. The End of the Hothouse
    TIS, The opening of the Drake Passage was a progressive process: it is by no means certain that it was sufficiently deep (i.e. oceanic) at the time this piece is discussing: however as I note in the piece, it is believed to have been of importance later in the Oligocene and Miocene, which is when the ice-sheets themselves developed. By that point you have three things at work, namely thermal isolation due to ocean currents, steadily-increased albedo and decreasing CO2 - but not at the same rate as in the massive drawdown in the latest Eocene. Interestingly, orogenesis has been linked to other sudden coolings - e.g. the Hirnantian glaciation and the Taconic Orogeny that came a little before. The isotopic signature for weathering then is one of the biggest in the entire Phanerozoic. Similar studies would be useful in this case and I have suggested this to the paper's authors. Cheers - John
  36. The Inconvenient Skeptic at 19:32 PM on 20 December 2011
    The End of the Hothouse
    Tom #20, The Strait of Magellan is inland of Argentina. It is the Drake Passage that is the land between South America and Antarctica. That is what opened up at the same time that Antarctica froze over and the CO2 dropped. Hypothesis #1: The geography of the Earth changes the ocean currents and this causes: Southern Ocean to Cool and Antarctica to start freezing. This in turn lowers the level of CO2 in the atmosphere because cold water absorbs more CO2 than warm water. The snippet that was politely cut showed the science of solubility of CO2 in water, it was just inconvenient science. Hypothesis #2: The level of CO2 drops for no particular reason, but this causes everything BUT the geographical change and the ocean current change..... The science on this subject is very clear. There is every scientific reason to dismiss claims that CO2 drop triggered the temperature drop of the Southern Ocean and Antarctica.
    Response:

    [DB] "The snippet that was politely cut showed the science of solubility of CO2 in water, it was just inconvenient science."

    Actually it was just giving publicity to a non-science website, as was politely delineated before.

    "The level of CO2 drops for no particular reason"

    Now you posit magic.

  37. Arctic settles into new phase – warmer, greener, and less ice
    Re the first few comments on seasonal behaviour of ice cover: it has seemed to me that the closer track of anomalies to the changing seasons in recent times is mostly a result of thinner ice responding more quickly. If so, this should be more evident in the melt season than during recovery, and I think that can be seen in the CT graphic.
  38. Foster and Rahmstorf Measure the Global Warming Signal
    @Tom Curtis: I stand by my assertion that Tomino's analysis is more understandable to the average person than is Dana's because of the way Tamoino weaves in very straightforward descriptions of terms and acronyms.
    Response: [dana1981] Your opinion is noted. Can we talk about some science now?
  39. The End of the Hothouse
    12, Ger, I think you have cause and effect reversed. The methane is being released because temperatures are rising and things are thawing, not vice versa.
  40. The End of the Hothouse
    Ger - the height of South pole and the circumpolar current would be the major factors in the difference.
  41. Foster and Rahmstorf Measure the Global Warming Signal
    John Hartz @21, the section in which Foster and Rahmstorf defines terms reads as follows:
    "Our analysis includes the five best-known global and hemispheric temperature time series. All data sets are combined land/ocean temperature estimates. For surface temperature, we use GISS: the land + ocean temperature data from NASA’s Goddard Institute for Space Studies (Hansen et al 2010 and references therein), NCDC: the Smith and Reynolds data set from NOAA’s National Climate Data Center (Smith and Reynolds 2005, Smith et al 2008), and CRU: the variance-adjusted HadCRUT3v data sets from the Hadley Centre/Climate Research Unit in the UK (Brohan et al 2006, Jones et al 2006). For LT temperature, we use RSS: data from Remote Sensing Systems (Mears and Wentz 2008), lower-troposphere data version 3.3, and UAH: that from the University of Alabama at Huntsville (Christy et al 2000), lower-troposphere data version 5.3. We characterize the ENSO by the multivariate el Nino˜ index, or MEI (Wolter and Timlin 1993, 1998). For volcanic influence we use the aerosol optical thickness data from Sato et al (1993), or AOD. To characterize the solar influence on temperature we use the total solar irradiance (TSI) data from Fröhlich (2006). To test whether the results might be sensitive to these choices, we also did experiments characterizing el Nino by the southern oscillation index (SOI) rather than MEI, characterizing volcanic aerosols by the volcanic forcing estimate of Ammann et al (2003) rather than the AOD data from Sato et al, and using monthly sunspot numbers as a proxy for solar activity rather than TSI. None of these substitutions affected the results in a significant way, establishing that this analysis is robust to the choice of data to represent exogenous factors."
    (Links to convenient access points for the data substituted for footnotes. Not all links are identical to those in the footnotes from F&R 2011.) They do not mention or define the PMOD TSI index, although Frölich 2006 does indeed detail the PMOD TSI index. PMOD stands for the Physikalisch-Meteorologisches Observatorium Davos, and my writing that represents the first time I have seen it referred to as anything other than PMOD except on its own website. That raises the point that the only acronym's Dana left undefined where acronyms for institutitions (used as short hand for their related indices). In all cases the use of the acronym is far more common than the use of the full name, so confusion is unlikely to arise. Therefore, I think your criticism of Dana on this point is excessive.
  42. Models are unreliable
    scaddenp, you are right, I was confused. Fig 2a shows both the raw observation which is -0.5 peak cooling and the ENSO-adjusted which is -0.7 UAH shows a bit over -0.4: http://www.drroyspencer.com/wp-content/uploads/UAH_LT_1979_thru_November_2011.png
  43. The End of the Hothouse
    TIS @18, a more likely cause of the drop in CO2 was the collision between the Indian Sub-continent and Asia which was occurring at that time. The consequent raising of the Himalayas resulted in massive erosion, a process which absorbs CO2. The cooling of the Ocean due to the opening of the Magellan straight (the gap between Antarctica and Australia) would also have resulted in increased absorption of CO2 into the ocean, but based on the correlation between temperature and CO2 levels observed in the Vostock Ice Core, that would have reduced atmospheric CO2 levels by around 150 to 250 ppmv, and could not account for all, or even most of the 700 - 1200 ppmv reduction observed.
  44. The End of the Hothouse
    There is a more likely candidate for the faster melting than GHG alone and that would be the dumping of the heat which will be transported to the poles. Not only dumping but also the release of methane and its reduction in the air to carbondioxide + water will release quite an amount of heat. If permafrost is escaping lots of ch4 that might be quite a good reason why the north cap is melting faster than the south pole.
  45. Foster and Rahmstorf Measure the Global Warming Signal
    @chriskoz: Tamino did an excellent job of defining the scientific terms and acronyms in his analysis of the same paper. I believe his approach was superior's to Dana's in this particular regard.
  46. The Inconvenient Skeptic at 11:23 AM on 20 December 2011
    The End of the Hothouse
    So what caused the CO2 to drop? Could it be the formation of the Southern Ocean that was taking place as the Antarctic Circumpolar Circulation started at the same time. Interesting that a 10 C drop in the 100m of the Southern Ocean would be enough to absorb large amounts of CO2 and cause the levels to drop.
    Response:

    [DB] Link to non-science blog snipped.

  47. Foster and Rahmstorf Measure the Global Warming Signal
    Chriskoz @19: AOD is aerosol optical depth, and is a measure of the reflectivity of the atmosphere due to sulfate aerosols including those emitted by volcanoes. TSI is the Total Solar Irradiance, and is a measure of the total power received from the sun across the full range of the electromagnetic spectrum falling on a one meter squared area in orbit and held at right angles to the incoming sunlight. ENSO is the El Nino Southern Oscillation and is the actual physical phenomenon observed in the equatorial Pacific ocean. MEI is the Multivariate ENSO Index, and is one of many measures of the strength of the El Nino Southern Oscillation.
  48. Foster and Rahmstorf Measure the Global Warming Signal
    John Hartz @1 Frankly, of all of acronyms on the figures above, the only one I clearly understand is ENSO (I didn't enven know ENSO could still be double-abreviated to MEI when talking about its measure!) rest of them are pure magic. But I can deduce their meaning from the context, i.e.: TSI must be the sun output variability (? Sun Index) and AOD must be the volcano eruptions. Even without those guesses, the term 'exogenous factors' makes the things understandable. Overall, Dana's article and the statistical analysis in the paper are well understandable, even by untrained people like me. I have a suggestion about those acronyms: make a list of them, for example in Newbie's section, in alpha order. Could be explained, if required, in one sentence each. Or even if not explained, it's nice to have them here at SkS, rather than looking up at wikipedia, discriminate them from incidental idents, etc. Has anyone got such list? If not, I can start sth up: AGW - Anthropogenic (man-made) Global Warming OA - Ocean Acidity ENSO- El Niño Southern Oscillation GHG - Greanhouse Gases SST - Sea Surface Temperature
    Moderator Response: [DB] A list of acronyms is in the works already. But thanks anyway for the suggestion!
  49. Foster and Rahmstorf Measure the Global Warming Signal
    #13 skept.fr, I'm not sure I agree with you on your point #1. ENSO is the variability, not the rising trend, and so removing the ENSO signal will not remove any of the increasing trend in global temperatures. It would only do so if ENSO showed a trend over the same period. GHG forcing might affect the pattern and strength of ENSO, but that would show up in the ENSO signal oscillations, which are then removed. For your #2, AFAIK, AMO and PDO are not large enough to have a significant effect on global temperatures. For example, when PDO is in a 'cool' phase, a significant part of the North Pacific is in a 'warm' phase as part of the oscillation - the net effect on global temperatures is thus very muted. The PDO is also likely the integrated product of ENSO variations, and so is not a forcing in its own right. The AMO's definition has a linear global warming signal removed from it too. But this discussion (if there is one) is probably best on another thread.
  50. Arctic settles into new phase – warmer, greener, and less ice
    ManOfFireAndLight: The Independent(UK)article that you have provided a URL for is based on the paper "Recent changes in shelf hydrography in the Siberian Arctic: Potential for subsea permafrost instability" which I cited in my post #14.

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