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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Comments 74051 to 74100:

  1. Lessons from Past Climate Predictions: IPCC AR4 (update)
    Jonathon#72: "Without sufficient data, any model, hypothesis, or prediction can be "reasonably accurate."" Really? It only takes one data point to falsify some hypotheses. You seem to be objecting here to the ambiguity in the phase "reasonably accurate." Yet you now introduce the equally ambiguous qualifier 'sufficient'. So we now have a statement virtually devoid of practical meaning, as we will only have the necessary data to certify a prediction as 'accurate' after the fact. That is the perfect excuse to do nothing -- or as we used to say in the oil business, 'I never lost any money on a well I didn't drill.' Has this level of scrutiny been equally applied to predictions made on both sides of the climate change argument? Or do we have a data point for a hypothesis about the motivations for these objections?
  2. Dikran Marsupial at 02:06 AM on 25 September 2011
    Lessons from Past Climate Predictions: IPCC AR4 (update)
    Jonathon wrote: "To claim as Dikran suggests that this model is "as accurate as there is reason to suggest it should be," is more of a statement about the uncertainty of the model rather than its accuracy." No, you are completely missing the point. The ensemble mean is an estimate of only the forced component of climate change. The observed trend is a combination of the forced change and the unforced change (i.e. a realisation of the effects of internal climate variability). Thus to directly compare the ensemble mean and the observations, is comparing apples with pears. To know whether the ensemble mean is "reasonably accurate" you need an estimate of the plausible effects of climate variability on the observations. Currently the spread of the models is the best estimate of this available. Thus it is not a statement about the uncertainty of the models, but of the uncertainty in estimaing the forced component of the trend in the observations, which is what you need in order to be comparing like-with-like when comparing the observations with the model ensemble. As I said "reasonably accurate" is a good summary, if you understand that the ensemble mean is only an estimate of the forced component of the trend. Saying that the models appear "reasonably accurate" is in no way "validation" of the models, and I don't think anyone is claiming that it is.
  3. Lessons from Past Climate Predictions: IPCC AR4 (update)
    Charlie A at 01:06 AM on 25 September, 2011 I don't see the importance of each decade's trend as you seem to see. As noted by others, in such short periods there's a lot of noise, and starting and ending points make a big difference in your results. Are you saying that this decade's trend is less steep than projected, so warming scenarios are exaggerated?
  4. Ocean Heat Content And The Importance Of The Deep Ocean
    @#14 Adelady -- I recognize that the SkS author made comments regarding observations. I just wanted to verify that Figure 2 is a model vs. model comparison before I go off looking to see if there is any observational data related to that. I am also looking for observational data to support or contradict the SkS summary point of "The surface layers, even down to 700 metres, are not robust indicators of total OHC." It seems that many studies have shown that the majority of variations in OHC are indeed in the upper 700 meters, and so therefore there is good correlation (although not perfect) between the 0-700m OHC and total OHC. Does anybody have any links for articles discussing the correlation between total OHC and 0-700m OHC? Or alternatively, perhaps Rob Painter can cite the source for his statement that 0-700m OHC is not a robust indicator of total OHC.
    Moderator Response: [grypo] If I'm understanding your question, IPCC Ch 5.2.2.2 discusses this in the paragraph starting:
    There is a contribution to the global heat content integral from depths greater than 700 m as documented by Levitus et al. (2000; 2005a). However, due to the lack of data with increasing depth the data must be composited using five-year running pentads in order to have enough data for a meaningful analysis in the deep ocean...
    The link for Levitus

    While 0-700 m has the most robust data, I do not believe there is anything physically important about that depth. Rob likely has more up to date information.
  5. Lessons from Past Climate Predictions: IPCC AR4 (update)
    Charlie A - there is no "bogus data" in the graph. You disagree on the choice of baseline - that's fine, you're entitled to your opinion (and that's all it is, your opinion), but don't start claiming that the data is bogus. In another comment, lucia posted a graph with a very different baseline which frankly I think is rather deceptive. But I didn't comment on it, because baselines don't really matter in this case. She's entitled to her presentation, I'm entitled to mine, and you're entitled to yours. You really need to accept that and move on. Or feel free to continue arguing about it with Zeke and lucia on their site, since they seem to disagree with you as well.
  6. Lessons from Past Climate Predictions: IPCC AR4 (update)
    Dana, Without sufficient data, any model, hypothesis, or prediction can be "reasonably accurate." In such a situation, the statement is essential meaningless. Based on the AR4 trend of 0.2C/decade, then the model would predict warming from 1/1/2000 to date of ~0.25C. The GISS observations yield 0.14C increase; HadCRU yields -0.04C. The simple conclusion is that not one of these trends is significantly different from each other. Since 2000, the monthly temperature range is 0.7C To claim as Dikran suggests that this model is "as accurate as there is reason to suggest it should be," is more of a statement about the uncertainty of the model rather than its accuracy. The model no more validates a climate sensitivity of 3 any more than it validates a sensitivity of 5 or 0. This whole exercise appears to be a vain effort to prove (falsify) something that is unprovable to date. At some point in the future, we will be able to ascertain the validity of this model.
  7. Ocean Heat Content And The Importance Of The Deep Ocean
    Rob #7 "because his simple model soaks up heat very quickly he claims climate sensitivity is low" But isn't this mixing up the concepts? If the ocean soaks up more heat it doesn't change the climate sensitivity, just delays the time to the equilibrium. Equivalently, a slower temperature rise might not mean lower climate sensitivity. The heat stored in the ocean might not be visible at the surface for a couple of hundred years but the TOA imbalance is still the same.
  8. Ocean Heat Content And The Importance Of The Deep Ocean
    i could have phrased that question better... What I mean is, is this energy into the deep ocean effectively "lost" (ie it won't come back up in the next 100 years)? Or does the opposite happen (energy from deep ocean comes up) which if it did would cause OHC in the top 700m to rise very quickly during such a period (the greenhouse gas forcing plus the upwelling from the deep ocean)? I guess this might be covered in the next part. Thanks for the article!
    Response:

    [DB] One can surmise that the mechanisms that transfer heat between the upper, mid and deep oceans have always been existent rather than a new development.  In that regard, the extra energy is not being "lost" per se but more than is "normal" is being transferred to the deeps at this juncture.

    Trenberth warns that it is when this mode shifts that we may experience decadal periods when this sequestered "heat" comes roaring back out of the deeps, making the recent period of "cooling" (aka, the hottest decade in the instrumental record) seem very cold indeed.

  9. Lessons from Past Climate Predictions: IPCC AR4 (update)
    #62 Grypo, "The models inability to model the cooling effects will mean the models will overestimate warming. If they didn't, it would be more worrisome for the modellers." Well, I agree with your statement, but it introduces a bizarre argument in a conversation about validation. What weight should we attribute to a model that is missing a substantial known forcing, and which gives rise to a warming bias of untested magnitude? If the model is only partly formed, then the obvious solution is to drop the model from the CMIP suite until it is ready to be validated.
  10. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    Eric#26: Thank you. I meant to link to the full report. A similar figure is at the end of the Gulledge presentation.
  11. Ocean Heat Content And The Importance Of The Deep Ocean
    What if this bleed of energy to the lower ocean keeps up though? (not permanently - I mean it just keeps happening). Wouldn't that raise the response time to a doubling of CO2 meaning that potentially it takes a lot longer for 2C warming to be realized?
  12. Lessons from Past Climate Predictions: IPCC AR4 (update)
    #55muoncounter "Do you accept charlie's graph here?" Note that the realclimate graph at the end of comment #18 shows the GISS rebaselined to 1980-1981. The model data in that graph is for A1B scenario, but the GISS data does match up with my figure from comment #46. I see all sorts of justifications and excuses for showing bogus data. Showing the correct data does not affect the rather vague conclusions of this article, so I don't understand why there is so much reluctance to correct the figure. again.
    Response:

    [DB] "I see all sorts of justifications and excuses for showing bogus data."

    So if someone has an alternative approach to something than one you favor then the other approach is "bogus"?

    One thinks that the skeptical thing to do would be to first understand the other approach (which you say you do) and either agree that there is no meaningful difference in results (which you do) or show why the other approach is invalid (which you don't).

    Suggestion: since you agree that it doesn't matter, perhaps it would be best to drop this line of discussion as your persistence in this reflects poorly on you.

  13. Lessons from Past Climate Predictions: IPCC AR4 (update)
    @66 Alexandre --- my comments in both this article and the previous one have been with the sole focus of trying to understand what is being presented in Figure 3. I have not made any statements about model validation or trends, other than questioning whether Dana1981's assertion that the AR4 A2 model mean trend from 2000-2010 is 0.12C/decade. I did not even comment upon his related assertion that the A2 model mean from 2010 to 2020 is 0.28C/decade. Obviously offsets do not affect trends. The IPCC could have forecast global surface temperature anomaly of 55C going to 55.2C by 2010 and the trend would not be inconsistent with observations. While a projection of 55C might seem ridiculous, it is an anomaly not a temperature and the trend, as others have pointed out, would be correct. The AR4 projections, however, contain more information that just trends. The projections are anomalies, with a specific baseline of 1980-1999 (See caption of Figure 2 in the article). This allows us to determine not only the error in the projected trend, but to also estimate the rms error of the projection. The RMS difference between GISS and AR4 A2 projection anomalies, using a common baseline of 1980-1999 is 0.09C -- or about 1/2 of the expected difference over a decade. The rms difference between GISS data as plotted, and the AR4 A2 annual series using the link of the article is 0.21C. I cannot directly calculate the rms difference between the two time series as plotted in Dana's Figure 3, because I still cannot figure out how that figure was generated. It appears that the GISS data, after being passed through some sort of spline filter, is plotted using the standard 1951-1980 baseline, but it is unclear how the AR4 A2 projections have been modified. They appear to have been moved upward about 0.2C. This is what would happen if, after the fact, the difference between the projections and the observed data is used to adjusted the projections to minimized the rms difference.
  14. Lessons from Past Climate Predictions: IPCC AR4 (update)
    Maybe I'm being obtuse, but I don't see the contradiction in the conclusion. So far, the models and data are in reasonable agreement [falling within the spread of model runs, and not too far off from the average]. At the same time, it's not enough data to say anything meaningful.
  15. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    #25, muoncounter, I agree with your assessment that the shift of the distribution is an oversimplification. My argument has always been that the shape of the distribution is a function of climate change and local weather. For example we could see large changes in the shape and position of the distribution of precip and temp in Alaska but not much in San Diego (perhaps only a small shift). Your link however doesn't seem to contain to the graphic you show. In fact, the full report http://goo.gl/KLpwL shows the shifted distribution in fig 6.4
  16. Galactic cosmic rays: Backing the wrong horse
    Paul D: The headline of the press release stated: "Cloud formation may be linked to cosmic rays." OK, they may be, but that is not what Kirkby actually says. Writers ranging from Nigel Calder to the Forbes 'science' blogger picked this up and turned it into 'Hooray! Its proven that cosmic rays cause climate change!' in spite of the Kirkby quote. One has to suspect (and in Calder's case, it is a certainty rather than a suspicion) that is what they wanted to hear. Worse still, they started throwing around the sham argument that 'there's a conspiracy to keep Kirkby quiet' or some such twaddle. But I suppose there are some who still believe the moon is made of cheese.
  17. Ocean Heat Content And The Importance Of The Deep Ocean
    Thanks for your thoughts, Adelady. I totally agree that what happens TOA is the prime factor. But my musing is about the geography of thought on the subject. The reason I strongly approved of SkS side of the attempt at a conversation with Dr. Pielke Sr. was that he argued for a single value indicating global warming, whereas the consensus position of the contributors on the SkS was that multiple indicators were important. To make more of the example I started- Suppose for some reason the GCMs are not doing a good job with ice melting. For whatever reason they park the heat the lower atmosphere, and thus over-predict both climate sensitivity and the future temperature record. But the ice keeps on melting and sea levels rise and so forth. If we get too stuck on GCMs and the accuracy of GMT scenarios, we are guided away from action because we can't incorporate the sea level rise properly into the picture. At the end it IS the effects that motivate for change. Given the impressive ability of the denialsphere to change topics, shift goal posts, invent ad hoc goals and so forth, I'm wrestling with how to communicate around that...hence also the concern for the boarderlands of skepticsm and denial.
  18. Lessons from Past Climate Predictions: IPCC AR4 (update)
    Has Lucia left the building?
  19. Ocean Heat Content And The Importance Of The Deep Ocean
    charlie, check the summing up "Current observations of the 700 metre surface layer have shown little warming, or even cooling, in the last 8 years; but the surface layer down to 1500 metres has shown significant warming, which seems to support the modeling." So figure 2 does represent model runs and the text below talks about the various features of those models. But the features they remark on are about how well the models match observations.
  20. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    Another relevant graphic is Fig 2.4 in 'Degrees of Risk.' This suggests that rather than the simple linear shift to the right of the symmetric probability curve shown in Fig 1 above, we may see a flattening and broadening of the probability spectrum, shapes better represented by Poisson distributions: Along the horizontal axis, plot a 'severity' index; the vertical is probability of occurrence. The m=0.5 curve might represent historic conditions; m=1 or 2 or 4 might be where we are heading. By flattening the distribution, extreme events start showing up under the long tail to the right. That doesn't mean that everyone sees the same extremes; it simply means there are more possibilities. The metaphor of 'rolling 13s' is a very good one.
  21. Ocean Heat Content And The Importance Of The Deep Ocean
    Dave123 "... at the same time I think ice melt, extent, precipitation, and GMST with appropriate weightings as an objective function might be more useful. " Maybe so. But we have to go with a)what we've got b) the most straightforward link to the physics possible. For a), we have to acknowledge that meteorologists, geographers, governments and other observers of 50 years ago weren't aware that a later generation might be interested in long-term data-sets of items that were of only peripheral interest to them at the time. So temperature is really the only consistent record we have for most of the globe. For b), the big issue now and for a long time yet to come, what's happening at TOA. The physics tells us that heat that does (or doesn't) escape to space from there is the major determinant for total heat content of the atmosphere and the ocean. We might as well face that fact. The heat might show up in winds and weather locally or it might go into melting glaciers and icecaps we've never seen. (Apart from the hardy souls who venture into remote, inhospitable realms, that is.) The items you mention are good evidence for the effects of warming, but temperature is the central issue.
  22. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    15, Norman, It is very important to note that the current warming trend only covers the last three bars (out of sixteen) in that 1850-2000 bar graph, and of those, only that last 1 or 2 demonstrate enough warming to tease out a climate change impact. As such, I find the reference of no value whatsoever. A proper verbal interpretation of the graph would say "the overall trend for the period prior to the impact of anthropogenic climate change is downward, but there is not yet enough data to determine if the 'climate change tail' will be definitively upward -- i.e. yet another hockey stick."
  23. Dikran Marsupial at 23:53 PM on 24 September 2011
    Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    John Russell that is pretty much why "climate change" is a more accurate term than "global warming". Physics sas the globe will warm on average as a result of increasing atmospheric CO2, but that doesn't mean it will warm uniformly everywhere, or that there won't be anywhere tht cools rather than warms. The thing to do is point them toward the regional projections for Europe in the IPCC reports, which suggests that the U.K. is somewhere where it is unlikely to see that much warming. I can't remember what it says about extremes or precipitation off-hand. I'd also point out that internal variability (i.e. weather) is increasingly dominant over short timescales and on small spatial scales, so weather over a decade or two in the U.K. (which is tiny) says virtually nothing about climate, changing or not. It's good we are in basic agreement though, it would be nice if there were more of that generally! ;o)
  24. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    chris, the first thing that people need is to change the reference from 'global warming' to climate ... 'change' or 'disruption' or, for the unlucky ones in some places at the wrong times, 'crisis'. I know that it is global warming, but as soon as people start thinking about themselves or their own location, they drop the 'global' without even noticing. As for Britain's last 2 winters. Those cold winters, below 71-2000 average for temperature, were both accompanied by above average hours of sunlight and below average rainfall. No idea if those things are significant. As for your 'unreliable summers', I remember reading a gardening magazine a few years ago talking about growing some plant or other which grew a lot better with England's consistent rainfall than Oz's long, dry, hot periods. They referred to England's "terrible weather but wonderful climate" for gardeners.
  25. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    Norman#15: "an interesting link to Texas climate. " This graphic produced by Texas' state climatologist, John Nielsen-Gammon is very relevant here: It's easy to say that the big red dot (2011's hot and dry weather) is exceptionally odd. But note the years 2006, 2007, 2008, 2009, 2010 and 2011 are all above the curve, with 2004 and 2005 on it. That is starting to scare people, including the same John NG, who doesn't see it ending any time soon: ... we have heightened drought susceptibility during this period, and, according to some studies, the effect of La Niña is likely to be amplified. So this coming year looks very likely to be another dry one, and consequently it is very likely that next summer will have water shortages and drought problems even more severe than this summer. That's what I take the concept of a 'new normal' to signify: Higher probabilities of 'extreme,' 'severe,' 'more intense,' 'never been like this,' etc. But I find it unreasonable to believe that everyone, everywhere will be seeing the same warmer, drier summers at the same time: I'd love to know where that idea got started. My suspicions are that oversimpliers gave the suggestion and deniersphere picked it up with ignorance like this. I apologize to John R and any others who took exception to my brusque turn of phrase, but if a certain governor gets his party's nomination next year, ya'll will be hearin' a lot more of that.
  26. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    Chris, I agree with everything you say. And I don't really disagree with anything Dikran says -- or muoncounter for that matter. The problem I was addressing -- based on the subject of the post -- is in explaining climate change to people in the UK who do not perceive themselves to be experiencing extreme weather: and what they are experiencing seems not to be connected with 'warming'. Now, if they were in Texas, it might be more obvious.
  27. Ocean Heat Content And The Importance Of The Deep Ocean
    Please clarify whether the total energy in the graphs of figure 2 are observed total energy or the total energy as simulated by a model. My understanding is that what is shown is the correlation between two outputs of the model and that none of the data in Figure 2 is measured, observed data. Correct?
  28. Galactic cosmic rays: Backing the wrong horse
    12, Paul D, The first sentence says the rebuttal features his own words, not contradicts. Here are those specific words:
    "At the moment, it actually says nothing about a possible cosmic-ray effect on clouds and climate, but it's a very important first step" -- Dr. Kirkby
  29. Ocean Heat Content And The Importance Of The Deep Ocean
    Actually, average depth of the oceans is 3.8 km, not 4.3. Otherwise, a good post. In terms of the short term climate sensitivity, yes, putting heat into the ocean slows down warming but in turn means that the eventual cooling will not be fast.
    Moderator Response: [John Hartz] Source please.
  30. Lessons from Past Climate Predictions: IPCC AR4 (update)
    Charlie A at 12:29 PM on 24 September, 2011 What's the difference between the trends in your graph, and the trend in Dana's graph?
  31. Dikran Marsupial at 23:01 PM on 24 September 2011
    Lessons from Past Climate Predictions: IPCC AR4 (update)
    Jonathon "reasonably accurate" is not a "strong conclusion" and hence is supportable by the evidence. To my eyes "reasonably accurate" means "as accurate as there is reason to suggest it should be". As I have said before, even if the model is perfect, there is no reason to expect anything more than for the observations to lie within the spread of the model runs. If the observations (considering their uncertainty) lie within the bulk of the model runs, rather than right out in the tails, then "reasonably accurate" would be an excellent summary. In order to work out whether the models are accurate, you first need an estimate of the variance that can be caused by internal climate variability. We can't get a good estimate of that as we have only one realisation of the observed climate. So the best estimate we have of climate variability is given by the spread of the model runs. If you have a better estimate, lets hear it, the models mean cannot be expected to be any closer to the observations that that.
  32. Lessons from Past Climate Predictions: IPCC AR4 (update)
    John Hartz asked: John Hartz (at 06:42 AM on 24 September, 2011) asked:
    @All commentors At this juncture in the comment thread, do you have any reason to believe that the conclusions stated in the final paragraph of Dana's article are incorrect? If so, why?"
    The last section is very problematic to me, and seems to contain logical incompatibilities. In the space of a few sentences it states (concerning IPCC AR4 projections), that "it's difficult to evaluate the accuracy of its projections" and that the projections are "reasonably accurate thus far"..... ....and that it will take another decade before we know what the projections will say about climate sensitivity, but that their "reasonable accuracy thus far" indicates that this will provide evidence that climate sensitivity is near 3 oC. This seems a semantic and logical mess. I don't see how one can say at the same time that it's difficult to evaluate the accuracy of projections, and that they're reasonably accurate! Nor can we say at the same time that we consider that the accuracy of the projections so far (which is supposed to be difficult to evaluate) will indicate that climate sensitivity is around 3 oC, and that we won't know what the projections will say about climate sensitivity for another decade. I don't think I'm being overly obtuse (if I am I'm sure you'll say so!). I would have thought that the justifiable conclusions are that the AR4 simulations are not inconsistent with the surface temperature progression since 2000, and that they are not inconsistent with the broad consensus of evidence that the climate sensitivity is near 3 oC (plus/minus a bit). However so far comparison of the AR4 models with the surface temperature progression of the last decade doesn't really tell us anything very much at all about climate sensitivity at all. One the other hand if one were to consider the comparison of climate model projections since the late 1980's, for example, with the subsequent temperature progression, then those models and the empirical data would give us confidence that our understanding of atmospheric and ocean physics and climate sensitivity are quite well supported. Overall I have a few concerns about the perception and use of model data in an out-of-science context. In my experience models are very useful for systematising large amounts of independent physical understanding into a useable predictor (through parameterization), for testing the reliability of our parameterizations through comparison of model output with empirical data, for suggesting possible interpretations and experiments (not quite so useful in the case of climate models) and providing a focus for independent study (for example, by identifying arenas where models and empirical observations are seemingly incompatible; good examples are model success with respect to MSU tropospheric temperatures; tropospheric water vapour uncertainty). There's no question that climate models are important for projecting multi-decadal consequences of specific emission scenarios. However we should be very careful in considering the value of decadal model-empirical comparisons, when it's very well understood that we don't have any expectation that models will necessarily do a good job of this (at least with respect to tropospheric or surface temperature progression).
  33. Lessons from Past Climate Predictions: IPCC AR4 (update)
    Michael, I agree that the data set is too short for strong conclusions. It appears that there are two beefs with Dana's conclusion that the AR4 models are reasonably accurate. First, that the time frame is too short to draw an accurate conclusion. Second, that the trend for the observational temperatures does not reflect the most recent data. Either way, the statement that the AR4 projections are reasonably accurate is not supported (nor falsified) by the recent temperatures.
  34. Lessons from Past Climate Predictions: IPCC AR4 (update)
    Paulk The next line abstract for JoC paper is important
    This is consistent with the fact that CCSM4 does not include a representation of the indirect effects of aerosols, although other factors may come into play. The CCSM4 still has significant biases, such as the mean precipitation distribution in the tropical Pacific Ocean, too much low cloud in the Arctic, and the latitudinal distributions of short-wave and long-wave cloud forcings.
    The models inability to model the cooling effects will mean the models will overestimate warming. If they didn't, it would be more worrisome for the modellers.
  35. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    Dikran/John I also live in the UK. I agree that one might not perceive much in the way of temperature change in relation to our notoriously variable summers (the one just past being pretty pathetic warmth/sunshine-wise, 'though we did have a fantastic summer in March-April!). However the earlier onset of Spring is quite noticable on a personal level, and I believe that what I perceive to be an increase in extreme rainfall events is a reflection of real changes in rainfall (increased during Autumn and Winter) that are consistent with expected global changes in precipitation regimes in a warming world. Likewise at a personal level I am aware of the problems in Scotlands skiing industry over the last 25 years with Glencoe shutting down, Glenshee being put up for sale and Cairngorm being taken into public ownership and skier days plummeting in the last 20 years ('though again 2008-2009/10 were very good years snow-wise in Scotland!), and am concerned about global warming related effects on the ecology of some unique habitats e.g. the Cairngorms, etc. Obviously some of these problems are exacerbated by non-climatic factors (continued paving/cementing over of urban centres reducing soil absorption of rainwater; tendency for skiers to head for more glamerous locales). But global-warming related impacts are already occurring and will undeniably bite deeper. Whether that's going to have much of an impact on our unreliable summers is a moot point!
  36. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    @Dikran Here in the SW of the UK, we've not had a good summer for the last four years. Instead we've had a lot of rain and it's been very difficult to find a slot for bringing in the hay. Because I grow trees on a large scale, the state of the ground is very high on my radar and it's been on the whole much wetter that it was a few years ago. I accept that in some areas of the UK, say the SE, that's not been the case and certainly a farming colleague in East Anglia has been moaning about drought. As far as the winters go, since the cold spells of my childhood in the 50s and 60s, as you know, winters have on the whole been very mild. Until 2 years ago most people under, say, 40 had not experienced snow drifts that come up to your waist. Most snowfalls in the south of the country seemed to melt within a day or so. The last two winters however have shown us how cold it can get and have caught many people out as they didn't consider it normal (ask your plumber!). You'll be aware that denialist writers like Delingpole and Booker have been making hay with this in the popular press, and will probably do so again this winter. Note that overall I'm talking about perception rather than the facts. I'm well aware that, considered annually, our average temperatures have been slowly rising: but that's not what people notice -- they don't experience weather through a thermometer. In this situation convincing some people that global warming is real, based on their experiences, can be difficult in the UK -- that's why the concept of climate change, with its redistribution of weather patterns, is the idea to push in the UK. I'm sure a shift towards higher temperatures (as illustrated by the temperature 'shift' bell curve) is probably a lot easier to sell in the US and Oz.
  37. Lessons from Past Climate Predictions: IPCC AR4 (update)
    There are several posters on this thread who are making nit-picks about how data has been presented. The lead post clearly states that the data set is too short for strong conclusions. These posters are making arcane arguments that there is some problem with the graphs in the post. Can they please post a proper graph that shows the conclusions are not correct? So far the "corrected" graphs argee with the lead post's conclusions. If the changes do not affect the conclusions, why bother? If you think that you are proving doubt by questioning the baseline of a short term graph you are wrong (0.05C!! who cares). Read a book about analyizing data with a lot of noise. There is always more than one way of properly presenting data of this type. If the conclusion is not affected by the change, it is not important. Please post data that shows the conclusion is not correct.
  38. Ocean Heat Content And The Importance Of The Deep Ocean
    Rob, [indirect ad-hominem deleted] I've been trying to build in my mind a geography of climate change thought, wondering about the boarderlands of denial vs legitimate skeptcism. The business with both Lucia and Dr. Pielke Sr. sounding 'lukewarmist' was a bit of a trigger. So I see a distinction in this mental geography betweeen the statements- "We have a climate sensitivity of 3 C nearterm and this results in the rapid ice loss at the poles and greenland" and "We have a X w/m2 energy excess that will result in a Y degree GMS temperature rise and a Z rate of ice melting". I know this isn't the topic of this thread...I'm not even sure there is a thread for this...but I'm starting to wonder about the use of GMST as a singular objective function for GCMs and whether Dana is going in the right direction with his historical series on that account. I do not buy into Dr. Pielke's (apparent) view that GC models are not useful if they don't forecast nearterm regional climate change accurately, but at the same time I think ice melt, extent, precipitation, and GMST with appropriate weightings as an objective function might be more useful.
    Moderator Response: [Dikran Marsupial] Please restrict the criticism to the argument, not the source, even if the ciriticm is indirect.
  39. Lessons from Past Climate Predictions: IPCC AR4 (update)
    #58 PaulK -- a minor quibble with your comment, and a further explanation of why the baseline adjustment method chosen by Dana1981 is incorrect ...... You use the abbreviation GMST. I assume this is Global Mean Surface TEMPERATURE. The datasets are not temperature, they are anomalies, or changes in temperature. We can monitor CHANGES in global average surface (actually 2 meter air) temperature much more accurately than we can monitor the actual absolute temperature. 0 degees Celsius (or Kelvin) on an AR4 model projection does not mean the temperature at which water freezes. It means "same same temperature as the average temperature from 1980-1999". Similarly, the GISS dataset is NOT temperature. It is the change, in degrees Kelvin, from the average temperature from 1951-1980. Fortunately, the GISS dataset can be converted to the same "degrees Kelvin change from the 1980-1999 average" that is used for the AR4 model anomalies. Contrary to what Dana1981 says, the choice of baseline is not arbitrary. On both this thread and the earlier thread of the same title, I have had a very limited specific goal. The desire to understand and replicate what Figure 3 purports to show. In the first thread, I was confused by Dana's claims that the 2000-2010 model mean trend was 0.12C/decade, followed by a model mean trend of 0.28C/decade. Those numbers have been corrected to the 0.18C/decade and 0.19C/decade numbers. What has not yet been resolved, at least in the main article, is the proper adjustment of two sets of temperature anomaly data series so that they have the same reference zero point.
    Moderator Response: [Dikran Marsupial] Trends are independent of the baseline, f(x) = 2x + 4 has exactly the same slope/gradient/derivative/trend (whatever you want to call it) as g(x) = 2x + 2. If the interest is in trends the baseline is irrelevant.
  40. Dikran Marsupial at 20:00 PM on 24 September 2011
    Lessons from Past Climate Predictions: IPCC AR4 (update)
    PaulK You mention "acceptable tolerance levels"; please specify what acceptable tolerance levels would be in this particular case. Note that even if the models were perfect, the observtions can only be reasonably expected to lie within the spread of the model runs, nothing more than that.
  41. Lessons from Past Climate Predictions: IPCC AR4 (update)
    Model validation requires the demonstration that for a set of input vectors varying within credible uncertainty levels, the set of key output vectors vary within acceptable tolerance levels. Matching to a single dataset, such as GMST is a necessary but not a sufficient condition for model validity, whereas demonstrating that there is no match to a key data time series can be a sufficient condition to demonstrate the lack of validity of a model. The comparison of GMST here is disingenuous, to say the least, but suppose that Dana1981 could indeed credibly show a reasonable match of GMST between models and observations, should that convince us of the validity of the model(s)? AR4 WG1 reveals a very large shortwave heating deficit in all of the CMIP GCMs, which is compensated for by LW impedance. Until this is resolved, a comparison of GMST is like showing one face of a Rubik’s cube and claiming that the problem is solved. Model developers of CCSM have already reported on their latest model update, with focus on trying to solve the SW mismatch. The result is interesting:
    “The CCSM4 sea ice component uses much more realistic albedos than CCSM3, and for several reasons the Arctic sea ice concentration is improved in CCSM4. An ensemble of 20th century simulations produces a pretty good match to the observed September Arctic sea ice extent from 1979 to 2005. The CCSM4 ensemble mean increase in globally-averaged surface temperature between 1850 and 2005 is larger than the observed increase by about 0.4◦C.”
    Journal of Climate 2011 ; e-View doi: 10.1175/2011JCLI4083.1 http://journals.ametsoc.org/doi/abs/10.1175/2011JCLI4083.1 What price the current comparisons of GMST?
    Moderator Response: [grypo] Thank you for that link. Fixed it too.
  42. Dikran Marsupial at 18:54 PM on 24 September 2011
    Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    John Russell, I live in the UK and am a keen cricketer and I can tell you that cool wet summers are not the "new normal". We (the team I play for) isn't loosing any more games to the weather than it used to. Summers in the UK are notoriously variable and they are little different to how they have been for the last 20 years or so. The difference is that more fuss is made of it than there used to be. Cold spells in the winter are also nothing new. IIRC the U.K. is a rather bad place to look for evidence of climate change or extremes; we are buffered to a large extent by the Atlantic ocean and our weather is changable because it depends so strongly on regional atmospheric circulation. If from the west it is wet an cool in the summer, wet an mild in the winter; if from the east it is dry and hot in the summer, dry and cold in the winter. The only new thing is there being a possible increase in weather from the north in winter, due to blocking, but the evidence for that is fairly weak AFAICS. All just IMHO of course.
  43. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    @muoncounter #15 writes: "There are new normals; get used to them." No need to be aggressive. Is that how you talk to your students (assuming that Norman is right about your profession)? That there are 'new normals' is exactly the point I was making. It's just that in some places, like the UK, our 'new normal' seems to be cool, wet summers and really cold spells in winter (-15C) -- which makes it difficult for me to convince the 'general audience' (that you say the book is aimed at) that global warming is real. You don't have to explain it to me, mate -- I get it. I know several people who I call 'on the sceptic side of don't know' who have been to SkS on my suggestion and asked a few innocent questions. Some of them (admittedly those with a tendency to the devil's advocate approach) have come away with a negative opinion about the site and therefore have been pushed further towards denial. Which makes my job harder as a climate communicator. That does not mean they've all had this experience, some have suddenly 'got it'. All questions should be answered in ways that does not belittle the genuine student. Your last line was a put down and was unnecessary.
  44. Ocean Heat Content And The Importance Of The Deep Ocean
    Lars - had a re-read of Palmer (2011). Now fixed. Thanks for the correction. A post on Meehl (2011) is forthcoming. And a more detailed breakdown of the deep ocean warming is provided in Kouketsu (2011). I'll get around to that one too - eventually.
  45. Galactic cosmic rays: Backing the wrong horse
    My reading of the first sentence implies that the SkS rebuttal contradicted Kirkbys own words. I'm assuming Kirkbys words contradicted the popular press??
  46. Ocean Heat Content And The Importance Of The Deep Ocean
    Rob: These are not climate change simulations. Palmer et al. describe control runs, with all forcings kept constant at pre-industrial values. The TOA imbalances are not specified, they are inherent in the models. They study the models internal variations on decadal time scales, and find that, as you say, heat is distributed to all depths of the ocean. There is another, even newer, study by Meehl et al. in Nature Climate Change (”Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods”) which has the same sort of analysis, but for future-climate simulations. Meehl et al. get essentially the same result as Palmer et al., which is very interesting: Both papers shows, by different simulations, that Treberths missing heat probably is in the deep ocean (Trenberth is a coauthor of the Meehl et al. piece). One should also note that there are a number of measurements showing that the deep waters actually are warming. Purky and Johnson has a nice review (”Warming of Global Abyssal and Deep Southern Ocean Waters Between the 1990s and 2000s”).
  47. Ocean Heat Content And The Importance Of The Deep Ocean
    Dave123 @ 1 - "Isn't increased heat movement into deeper ocean layers an arrow pointing towards lower short term climate sensitivity?" IIRC Roy Spencer, and a few other skeptics, argue the opposite - because his simple model soaks up heat very quickly he claims climate sensitivity is low - the oceans having a limited capacity. Remember the oceans are the Earth's main heat sink, so that makes sense, if it were true. Spencer's model, however, is nothing like the real ocean. Bodhod @ 2 - warming of the deep ocean from volcanic activity is a natural contributor to the Thermohaline Circulation. As cold, dense, and salty water sinks around the poles and travels across the ocean floor heading towards the equator, it picks up a small amount of heat from volcanic venting. That, combined with mixing, makes the bottom water warmer and less salty and therefore more buoyant. This contributes to the rising portion of the circulation, so it a key component of the ocean's natural cycling.
  48. Review of Rough Winds: Extreme Weather and Climate Change by James Powell
    muoncounter @14 From other places you have posted I believe you are a teacher or college professor who lives in Texas. Here is an interesting link to Texas climate. Historical and Current Texas Weather Patterns. Some interesting points is that droughts have been less intense, on average after 1960. Last year and this year have been very bad for Texas but not unusual. Also in this document they have an interesting page with Texas Hurricane History. In the first graph they have hurricanes from 1950 to 2000. This is a 50 year period and the trend is up. Many may conclude that hurricanes are increasing and then link it to global warming. Then the next graph is Texas hurricanes from 1850 to 2000. Now the trend line is down. Maybe the author is trying to point out that weather trends are not that meaningful in trying to determine the future. This sample shows that 50 years has one trend, 150 years has the opposite trend. Who knows maybe 500 years and you have another postive trend and then go back 1000 and it is negative again. Also look at the rain and temperature graphs at the start of the document.
  49. Ocean Heat Content And The Importance Of The Deep Ocean
    I'd expect the Ice Sheet values and the Arctic Sea Ice to switch in order in the near future, correct?
  50. Ocean Heat Content And The Importance Of The Deep Ocean
    I didn't see it there, but no matter. It answers Bodhod's question quite neatly. A quantum of insignificance? Might use that some time.

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