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muoncounter at 23:14 PM on 15 May 2012IPCC graph showing accelerating trends is misleading
It is interesting that the word 'accelerated' is not present in the WG1 discussion of this graph. They merely state the obvious: The rate of warming averaged over the last 50 years (0.13°C ± 0.03°C per decade) is nearly twice that for the last 100 years. If the underlying temperature-time function is linear with random noise, trends calculated from any starting point and over any time period long enough to deal with the noise are all very close. This is distinctly not the appearance of the IPCC graph, clearly indicating that there is some curvature to the function. In this case, the curvature is up. -
dorlomin at 22:20 PM on 15 May 2012New research from last week 19/2012
Most of the climate science we come across tends to come onto the radar because of some spurious hand waving 'sceptical' effort to claim fraud or conspiracy or the like. Whats so great about these posts is it gives a brief weekly overview of the sheer volume of science and where the latest ideas are heading. The fact that week after week so many interesting papers appear is a testimony the how interesting and dynamic this area of science is. -
Carbon500 at 21:05 PM on 15 May 2012101 responses to Ian Plimer's climate questions
Composer99 and scaddenp: (-snip-). Hopefully it will get their teachers doing the same, instead (-snip-). To develop this further: The government statement that the world’s oceans are getting warmer everywhere is contradicted by the IPCC as I’ve quoted. Were I a school teacher, I’d be getting my class to investigate this further - for example, which oceans? Cooler by how much? Over what period of time? (-snip-)? - in other words, question, investigate and think for yourself – surely a good scientific grounding? The same applies to oceanic pH. The claim has been made that the average pH of the oceans has increased by 0.11 – does the class think this is plausible, and why? The sort of questions I’d be getting them to look into would be: what factors affect pH? Does the pH range of the oceans vary in different parts of the world? Does it change in shallower waters, and at depth? Is there variation with temperature? How important is CO2 in the picture? Can a class experiment be devised to test issues raised? Finally, Sphaerica : given my comments on ocean pH above, I'd need to do some investigating myself before forming an opinion. (-snip-). Naturally I accept that advances in modelling will have been made since the FAR, and have also noted their comments on computer modelling reliability on pages 600-601. However, (-snip-)?Moderator Response:[DB] This thread is about the Australian Governments 101 responses to Ian Plimer's climate questions and the scientific basis for them. It does not delve into the rationale for why Mr. Plimer takes the stance that he does. Nor does it explore the various and sundry conspiracy theories or "alternative explanations to known physics" that are based on little other than poorly-thought-out wishful thinking.
OHC is still increasing in its inexorable response to the radiative imbalance at the TOA. Use the Search function to look up Levitus 2012 from April for further info. The same for Ocean Acidification and modeling. All are off-topic on this thread.
Off-topic, conspiracy theorizing, allegations of fraud and ideological snipped.
Please construct further comments to comply with the Comments Policy as subsequent comments constructed as this one was will be summarily deleted. Thank you for your compliance and consideration in this matter.
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les at 20:54 PM on 15 May 2012IPCC graph showing accelerating trends is misleading
95 - SJR "I think that Skywatchers contribution suffers from the same problem as the IPCC graph, namely comparing trends over periods of different length." Really your post 100 and KR's post 99 answers this. There is not problem - despite the psudo-science from Helena 92 - to have identical periods so long as the uncertainty is treated properly. as 99 shows, the shorter period has higher uncertainness - however the effect is still substantially greater so there's no problem... skywatcher 76's graphs could have +/- bars or lines which would widen as they reached the early/late fixed point... if one doesn't explicitly calculate the error-bars, you are more or less forced to 'fix' the errors by having constant periods as per 100. -
John Mason at 17:05 PM on 15 May 2012Two Centuries of Climate Science: part three - Manabe to the present day, 1966-2012
Well spotted sailrick! There's always one that gets through! Thanks - John -
Nick Stokes at 16:59 PM on 15 May 2012IPCC graph showing accelerating trends is misleading
The Moyhu trend viewer helps here, though it only goes back to 1901. You can click buttons for the dataset and period you want - say Hadcrut from 1901 to present. In the triangle plot, you can see the trends to present along the right hand axis. They do show reddening colours going up untli about 20 years duration; shorter term trends to present are quite noisy and can be negative. If you want to see trends starting 1901, look along the x-axis, Again after some initial noise, there's quite a high trend reflecting the 1900-1940 period, then a dip, and then a rise to the century duration. You can click anywhere to see numerical values, with significance and a graph, and you can click the red square buttons to show significance. And if you want to cherry pick, it's helpful there too. -
skywatcher at 13:30 PM on 15 May 2012IPCC graph showing accelerating trends is misleading
Tom #108 - agreed , it's prefereable to use end point method due to signal/noise issues early in the series. This is seen in my second graph in #78, the early noise is what causes the trend to vary substantially for trends between 1875 and 1920. After that, you have the progressive rise, which tells you nothing more clever than that the overall profile is slightly convex, but it is weak at inferring anything much else. Helena, just saying 'no' will never make you right. Tom's statement is quite correct, as demonstrated multiple times upthread. You have failed to provide any examples, real or conceptual, that demonstrate otherwise. -
DSL at 12:26 PM on 15 May 2012Global warming stopped in
1998,1995,2002,2007,2010, ????
Muon beat me to it, matzdj. The theory of AGW did not start with measurement of temperature. It started with physics. If you or Roy are going to propose a step change, you'll need to provide a consistent physical mechanism. I second Sphaerica's recommendations as well, particularly Foster & Rahmstorf, as it is the kind of basic analysis ignored by those who start and end their analyses with a string of uncontextualized data. -
Mike3267 at 12:09 PM on 15 May 20122012 SkS Weekly Digest #19
Hate to be a wet rag, but some of our denier friends will spin the cartoon into some kind of death threat. In any case, I don't think calling people stupid is the best way to win them over. -
Dragonwyst at 11:57 AM on 15 May 20122012 SkS Weekly Digest #19
Help - edit - "out" not "our" -
Dragonwyst at 11:57 AM on 15 May 20122012 SkS Weekly Digest #19
Not intimidated - just a tad our of my depth. I'm aware of how little I know, and don't know that my 2c can actually add anything worthwhile. However, I think I want to start asking people on both sides of this non-debate what their childhoods were like. I think the "religious fervour" aspect has it's roots way back... -
sailrick at 11:27 AM on 15 May 2012Two Centuries of Climate Science: part three - Manabe to the present day, 1966-2012
"other non-condensing greenhouse-gases had exterted" typo in last word and another typo in the bottom graphic - lower right It reads "CO2 sourcees identified" an extra e Excellent series. delete or edit this, if you will -
Tom Curtis at 11:08 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
skywatcher @107, thanks for the clarification. We should note that it is still preferable to used the end point method rather than the start point method in this case. That is because the HadCRUT3v temperature index typically covered around 20% of the globe in the 1850's, compared to around 80% in the 2000's. The result is that the temperature record has a much lower signal to noise ratio early in the record, particularly prior to 1880 which would defeat the technique. (It may show the correct pattern, I have not checked. But it would be illegitimate to draw any inference from it.) -
skywatcher at 10:51 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
Tom #106, I see your point - the clarifying statement is this - whether you fix the start or end point, always read the trend changes forwards in time. So fixing the 1850 point begins with short trends and ends with longer ones, the later trends being larger than the earlier (2nd fig in #76). Fixing the 2005 point (as done by IPCC) begins with longer trends, that get progressively shorter through time (1st fig in #76), and in both cases the positive trend rises over time. That feature is unique to the rising, accelerating curve, and not present in a falling or decelerating curve. The rate of trend rise is lower if you fix the 1850 point than if you fix the 2005 point, due to the increasing amount of data involved in the longer trend (so the acceleration is less pronounced for the 1850 fix), but the trend still rises. -
muoncounter at 10:37 AM on 15 May 2012Global warming stopped in
1998,1995,2002,2007,2010, ????
matzdj: Your proposed 'step change' has been discussed here before. The problem is that there is no physical mechanism that can make that happen. You'd need an 0.3 degree step, which is about the size of the '98 el Nino (refer to the departure from linear in fig 3). That el Nino ended, as all of these cyclic events do. That leaves your 'step' unsupported. No, the scientifically unsound analysis is the one that does not look at all the data, does not take into consideration the noise and creates effects without cause. -
Tom Curtis at 10:33 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
Skywatcher @102 writes:"The patterns produced in both graphs in #76 are indicative of a temperature profile that is broadly concave, rather than convex or flat. I think that general point is mathematically defensible, as with Tom Curtis' sketches. Mathematically, whether you start in 1850 or in 2005, both will show increasing gradients for a concave profile, but one will have rapid increase near the end (2005 fixed point), and one will have slower increase at the end (1850 fixed). But both will increase."
I have probably misunderstood what you said, however, with an accelerating (concave upward) curve a sequence of progressively longer trends with a common start point would each have a progressively greater trend, ie, the longer trends would be larger. In contrast, sequence of progressively longer trends with a common end point would have progressively lower trends, ie, the longer trends would be lower. -
Tom Curtis at 10:25 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
In my concluding paragraph of 104, I should have said her assumption is false of any data with an accelerating slope and a signal to noise ratio sufficient to allow determination of the underlying signal. If Helena has wanted to argue that the technique illustrated by the IPCC can work in some cases, but that in the particular case used by the IPCC, the noise is to great for it to be valid, she may have had a point. There are relatively simple mathematical methods for determining that, and I believe they would show that she was incorrect. But you do actually have to look at the data to know if she would have been incorrect or not, if that had been her contention. Instead, Helena has argued that the technique cannot work under any circumstances, even as a statistical inference. She thereby demonstrates that she does not even understand the basic maths of the situation. -
Tom Curtis at 10:15 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
Two points for Helena: 1) I believe I have finally figured out what you mean be a decreasing decelerating curve. It is a curve which below the x-axis, ie, negative, but in which it approaches the x-axis over time such that curve satisfies the condition that slope(t) < slope(t+a) where a is greater than 0. That, however, is mathematically just an accelerating curve. Over time, the slope of the curve gets larger. The situation is described as - it is cold, but it is getting warmer, and over time it is getting warmer faster. So, yes, the IPCC technique will detect acceleration in this case - and so it should, for the situation is one of accelerated warming. If I have misunderstood your phrase (which is as clear as mud), specify what you mean mathematically, or plot the curve on a graph and show it to us. 2 Helena @93 said:"In the same way, when you start in the present (his graph1 and the IPCC), you're not being "fair" to the past as its trend gets mechanically diluted. You "force-flaten" long trends. That's why you can't compare trends that have different T. "
This theme that increasing the length of the trend will always flatten it is a constant theme of Helena's, and (so far as I can tell) the core of her argument. Indeed, SFAICT, apart from a few failed counterexamples and constantly reiterating that she disagrees, she has no other argument. And it is simply false. Consider the function such that If x < or = 0, f(x)= 0; else f(x)=x^2. We can consider two series of progressively longer trends. In the first series the trends are all centered on 1. In this case, each successive trend will have a higher slope than the previous trend. That directly contradicts Helena's contention. In the second series, the trends all terminate at 25. In this case, each successively larger trend will have a lower trend than the preceding one. This is the case that parallels the IPCC diagram. Helena's central assumption is in fact false of any data with an accelerating slope (and in some other cases as well). By sticking rigourously to her "intuitive statistics", Helena simply starts with an initial premise that no data can show acceleration. -
Tom Curtis at 09:48 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
SRJ @86, the question under discussion here is not, "What is the best method to analyze temperature trends over the last 150 years?" The IPCC's analysis did not consist of just the illustration under discussion, which as Dikran Marsupial has pointed out, only appears in summaries of the data, not in direct analyses of the data. In FAQ 3.1 where a similar figure to that above appears, the IPCC says:"Expressed as a global average, surface temperatures have increased by about 0.74°C over the past hundred years (between 1906 and 2005; see Figure 1). However, the warming has been neither steady nor the same in different seasons or in different locations. There was not much overall change from 1850 to about 1915, aside from ups and downs associated with natural variability but which may have also partly arisen from poor sampling. An increase (0.35°C) occurred in the global average temperature from the 1910s to the 1940s, followed by a slight cooling (0.1°C), and then a rapid warming (0.55°C) up to the end of 2006 (Figure 1). The warmest years of the series are 1998 and 2005 (which are statistically indistinguishable), and 11 of the 12 warmest years have occurred in the last 12 years (1995 to 2006). Warming, particularly since the 1970s, has generally been greater over land than over the oceans. Seasonally, warming has been slightly greater in the winter hemisphere. Additional warming occurs in cities and urban areas (often referred to as the urban heat island effect), but is confined in spatial extent, and its effects are allowed for both by excluding as many of the affected sites as possible from the global temperature data and by increasing the error range (the light grey band in the figure)."
Clearly, therefore, the IPCC makes people aware of the high trends in Global Mean Surface Temperature (GMST) in the middle of the 20th century. These high trends correlate with high trends in total Top of Atmosphere (TOA) forcing, although the forcings do not completely explain it. Because of that correlation, it would be an embarrassment to the IPCC if there where not high trends in GMST in the middle of the 20th century. As the IPCC makes people aware of the mid 20th century trends, their purpose in the diagram we are discussing is not to conceal them. Rather, it is to illustrate the general tendency to higher trends as the century progresses. If that illustration is not to be misleading, then an inductive inference from the pattern shown to the acceleration of the warming over the period in question must be justified. That is what has been questioned by Monckton and by Helena. So, while I agree that the additive model is better than the IPCC's chart, that is not relevant to this discussion. Further, while I agree that for most purposes comparing trends of different length is unwise, that is also not relevant to this discussion. What is relevant is the question as to whether or not, if you do compare trends as the IPCC has done, you can validly make an inductive inference that the warming has accelerated. Please note that simply comparing the peak 25 year trend in different periods does not answer that question. Consequently, for this purpose your first chart is worse than the IPCC's. That is because a high trend ending in a particular year may be followed by a low trend shortly thereafter. Consquently you can have more total warming with a lower peak trend which is reached year after year than with a higher peak trend that is reached and simply falls away. Another way of putting that is that that you get greater warming with more robust trends, and hence it is the robust trends which better indicate increased warming. Finally, the attack on the chart above by Monckton is not based on statistical qualms. Rather it is based on a desire to attack the IPCC to undermine action on global warming. You can be sure that had the IPCC used the additive model shown by you, it would have come under equally virulent, and unwarranted assault. If you do not believe this, just consider the continuing unjustified assaults against the validity of the temperature record itself. -
skywatcher at 09:38 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
SRJ - I quite agree on the general point that for a more detailed analysis, using trends of comparable length is preferable, but this is only relevant for detailed analysis, which the IPCC FAQ figure was not. Your numbers in #100 neatly illustrate the point with consistent trend lengths. The reason I produced the figures in #76 was that, as KR says in #99, the IPCC figure was merely illustrating a point. Not proving some part of atmospheric physics, or anything like that. Helena repeatedly implied that there was a kind of cherry-picking going on with the choice of the four trends by the IPCC - my figure neatly demonstrated that this was not the case, given the more-or-less progressively increasing trend rates to the present. Most other choices of four trends spaced across the profile would have given the same result, even if a few choices would have produced slightly different patterns (relevant to Dikrans points about forcing and trends). The patterns produced in both graphs in #76 are indicative of a temperature profile that is broadly concave, rather than convex or flat. I think that general point is mathematically defensible, as with Tom Curtis' sketches. Mathematically, whether you start in 1850 or in 2005, both will show increasing gradients for a concave profile, but one will have rapid increase near the end (2005 fixed point), and one will have slower increase at the end (1850 fixed). But both will increase. There are, statistically, much better ways to support the overall acceleration in temperature (or just look at any of the 'hockey stick' graphs!), but these methods would not be appropriate for an illustrative FAQ answer. Helena #92, a "decreasing, decelerating" profile would have negative gradients. So your point was? There are four possible curve solutions - draw the four possible curves, like the two in Tom Curtis' #77, one has increasing positive gradients, one has increasing (steepening) negative gradients, a third has decreasing positive gradients, and the last has decreasing (flattening) negative gradients. All would show up differently in my figures in #76. -
michael sweet at 09:18 AM on 15 May 2012Global warming stopped in
1998,1995,2002,2007,2010, ????
Mastzdj, I am surprised an engineer would claim "my “eyeball-least-squares-fit” to the data." Any scientist knows an eyeball line is not a least squares line. Using my special Mark-2 ultra-sensitive eyeball your lines are incorrect. They should have an upward slope in both cases where you have flat lines. Please provide a graph with a least squares fit and not an eyeball fit. -
KR at 09:02 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
SRJ - Got it, my mistake on what you were discussing in terms of autocorrelation. While I still feel that varying trend lengths are of some use, if properly considering uncertainties, I would agree that looking at equal spans provides rather more information. -
SRJ at 08:36 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
# 99 KR You misunderstood me, I was referring back to Dikran in post 94 where he suggested fitting a linear trend to the trend estimates from my plot in post 86. Those trend estimates are autocorrelated since they have so much data in common. I should have stated clearer in my post 97 that it was about autocorrelation between the trend estimates of post 86 rather than autocorrelation of the temperature anomalies themselves. The trends you are calculating are again for time periods of different length, and as such comparing apples to oranges. What I would do is to compare trends calculated over time spans of equal length, e.g. 100 years. Using the SKS Trend calculator here is how I would do it: Period _____ Trend Hadcrut3 1850-1950: 0.023 ±0.013 °C/decade (2σ) 1875-1975: 0.034 ±0.013 °C/decade (2σ) 1900-2000: 0.065 ±0.012 °C/decade (2σ) 1912-2012: 0.074 ±0.012 °C/decade (2σ) -
Bob Lacatena at 08:21 AM on 15 May 2012101 responses to Ian Plimer's climate questions
13, Carbon500, "The ocean remains alkaline (pH>7)" Really? So your position is that any change in the concentration of H+ in the oceans that does not actually push the pH below 7 is harmless? A 30% increase in H+ concentration (as evidenced by a pH change of 0.11) is unworthy of wory? On climate modeling: Do you think a single sentence in a five year old report provides a thorough and authoritative review of the state of an important and rapidly advancing aspect of science (climate modeling)? On the matter of ocean heat... Skeptical science will have a few important posts in upcoming weeks on this, relating to the latest research. I hope that you'll accept such findings with as much confidence as you do when quoting a 5 year old report. -
scaddenp at 08:00 AM on 15 May 2012101 responses to Ian Plimer's climate questions
Carbon500. See here for discussion of published total Ocean Heat Content. Note the date of the publication too. I'd say "the oceans are warming" is an accurate statement. What is the OHC data unequivocally shows is that we have an energy imbalance, and that temperatures will continue to rise. With a 101 questions to answer, the response is necessarily brief. If you wanted the detail, then the IPCC report would also make a good start, but good that you have found that. -
Bob Lacatena at 07:42 AM on 15 May 2012Global warming stopped in
1998,1995,2002,2007,2010, ????
matzdj, That's a very pretty up-down escalator you've created. Read this post and then this one. Some places to start (I won't argue with you, if you're as open minded and concerned as you say, then you should be able to figure this out very easily for yourself). 1) Don't use Spencer's graphs. He uses lots of "tricks" like stretching the Y axis, and adding the rather silly "polynomial fit for entertainment purposes." Try woodfortrees.org, like this. 2) Don't use short trends. They're useless. Your entire 2002-2012 choice is a waste of everyone's time. 3) Forget "step changes." There's no such thing. That's for the wave-your-arms-magic-and-fantasy crowd. 4) Read about Foster and Rahmstorf 2011. 5) Look at this post giving another perspective on how to look at temperatures. 6) Look harder for the ocean heat content information. This site is a good place to do that. There's actually a post coming up on that within a few days. A few of them, actually. Bottom line: a) Don't use short trends. b) Don't assume that because the simple observations are noisy that you can't extract a clearer signal from the data. c) When you do look at the signal, and you also consider the complexity and other factors in the system, everything makes sense. d) Read and learn more before you adopt a position. -
KR at 07:12 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
SRJ - If your concern is autocorrelation, I would suggest looking at the SkS Trend Calculator, which calculates uncertainties including autocorrelation effects, using the techniques of Foster and Rahmstorf 2011. Period ____ Trend GISTEMP 1980-2005 _ 0.156 +/-0.051 C/decade 1955-2005 _ 0.123 +/-0.023 C/decade 1905-2005 _ 0.071 +/-0.011 C/decade 1855-2005 _ 0.059 +/-0.007 C/decade Even with autocorrelation uncertainties the increase in trends is quite notable. All of this kerfluffle, however, is really over such a tiny point. Monckton was incorrect over the observed acceleration in warming, and in his strawman argument (as the IPCC conclusion of anthropogenic influences was not from this graph). This graph is merely an illustrative demonstration of "simple fits" to the temperature record (as per the IPCC illustration). Personally, I would consider this illustration (a) quite supportable as the simple demonstration it is, and (b) most definitely not the basis of conclusions about anthropogenic warming. -
matzdj at 07:05 AM on 15 May 2012Global warming stopped in
1998,1995,2002,2007,2010, ????
This is my first post here. I hope the note and images come through properly. ***************************************** I’m afraid that your negation of the skeptics arguments was in itself too simplistic and inappropriate. I agree with your preliminaries and with what you showed through Figure 2. However, only the TV talking heads would try to use Figure 2 as you show it. Let me suggest another possible view of the same data from UAH (extended to April 2012). I would appreciate your comments on the analysis.
First, let’s look at the 17 years from 1979 through 1996.
The green line is my “eyeball-least-squares-fit” to the data. A more precise analysis might not exactly match, but it certainly wouldn’t show a significant increase or decrease in global temperature during this period.
Now let’s look at the more recent years. Obviously, we want to try to avoid confusing the analysis with an El Niño, so let’s just look at the period from 2002 to 2012.
Can anyone show me the temperature global temperature increase that has happened during this last decade. If this data is real, I can’t see any response to an accelerating atmospheric CO2 concentration. (Does anyone challenge the raw data or its reduction to this curve?)
Now if we put these two together, it seems to indicate that there were a step change that occurred between about 1996 and 2002.
Yes., it’s warmer now than it was in 1979. Yes, the last decade has been the warmest in a while, but how can you, in good conscience, draw a straight line from 1979 to 2012 and relate that to any parameter that as been rising steadily at an accelerating rate? It may be mathematically, and statistically, correct, but it is a scientifically poor analysis of this data.
I have also seen some analysis on this site that say that just because temperature change isn’t happening, doesn’t mean climate change is over. What was cited was that what was really important was Global Heat Content, because that was how to understand the net increase in heat being captured by the oceans. A curve was shown through about 2003 and looked to show a steadily increasing global thermal heat content. You almost had me convinced.
Global heat content does look to be a pretty sound way to look at whether the earth is absorbing more heat or not. However, the data stopped at 2003. I searched around and found a figure on the NOAA site
.
Now please help me understand what is steadily increasing in response to the accelerating atmospheric concentration of CO2 .
For reference, I am a liberal research engineer, who also happens to be an anthropogenic global warming (nay , climate change) skeptic. Not a non-believer, a skeptic. I agree there are changes happening. I’m sure that man is causing at least some of it. But the doomsaying conclusions I hear being expounded just don’t seem to be justified by the data that I have been able to find. I would be happy for you to help me see the error in my ways.
Your site has the potential to be a place where data can be discussed and countered and recountered. The other sites all seem to be only one sided. Are you willing to open this site to not only beating down the stupid comments made by the right wing talking heads on TV, but to honestly looking at the experiments, the data, the interpretation of that data, and the alternative conclusions that can be drawn?
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SRJ at 06:57 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
# 96 Dikran I think we are talking past each other. The fitted model is statistical significant over the 2 periods mentioned in the quote from Gavin Simpson. The model is estimated from all data so I do think it makes sense to say it is insignificant from 2003 on. Because the model for the period 2003-2011 is estimated from more data than just these few years. But I am coming a bit out of my depth so I will refer you the blog post I mentioned and the documention for the mgcm package: http://stat.ethz.ch/R-manual/R-devel/library/mgcv/html/gamm.html http://stat.ethz.ch/R-manual/R-devel/library/mgcv/html/s.html My reason for my original statement "and continued but not significant warming from 2003 to 2011" was exactly that I didn't want people to interpret the lack of significance as indication of no warming. And I do think that we can agree on that? I -
SRJ at 06:38 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
# 94 Dikran I don't think it will be useful or meaningful to fit a a linear model since these trends are extremely autocorrelated as they have so much data in common. I. e. the data point for 2010 is estimated from the period 1986-2010 while the data point for 2011 are estimated over the period 1987-2011, to they have 24 common years. And yes, my graph shows that the 25 year trend has increased since 1850-1874. It also shows that around 1940 the 25 year trend were as high as today. That does not contradict IPCC, my graph are just showing more details about 25 years trend. In fact, doing my analysis with the other timespans IPCC also use shows: 50 yrs trends: Increased since 1850-1899, around 1940 as high as today 75 yrs trends: Increased since 1850-1924, recent trends are highest observed 100 yrs trend: monotone increase since 1850-1950, but in recent years they have stabilised In agreement with IPCC - but I still don't like that graph -
Dikran Marsupial at 06:18 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
SRJ, one must be very careful of mentioning statistical significance in the climate debate as it is very widely misunderstood. Over short timescales it is meaningless to say that the trend is statistically insignificant as this will be the case purely because there is insufficient data in the period to reliably asses what the trend actually is. If you do specifically point out that something is not statistically insignificant then it is important to also mention whethe the power of the test is sufficiently high for the lack of statistical significance to be meaningful or even surprising. Unless you do this, then there will be those who misinterpret the significance of insignificance! ;o) -
SRJ at 06:12 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
# 90 Dikran I agree completely with your last statement. But please note that my statement you quote was not about linear trends but about the significance of the locally fitted generalized additive model. It is not an attempt to use only the 2003-2011 data, I just simply state the fact that the fitted model is not showing an significant increase after 2003. But it is still increasing. If you read Gavins Simpsons blog post he notes that the model is significant until 2005, but with the addition of the slighly cooler year 2011, the significance only extends to 2003. What I tried to emphasize was that the lack of statistical significant warming does not mean that there is no warming, basically I was summarizing Gavin Simpsons comment about the graph: "The derivatives suggest two periods of significant increase in temperature (at the 99% level); during the inter-war years and post ~1975. The second period of significant increase in global annual mean temperature appears to persist until ~2005. After that time, we have insufficient data to distinguish the fitted increasing trend from a zero-trend post 2005. It would be wrong to interpret the lack of significant change during periods where the fitted trend is either increasing or decreasing as gospel truth that the globe did or did not warm/cool. All we can say is that given this sample of data, we are unable to detect any further periods of significant change in temperature other than the two periods indicated in blue. This is because our estimate of the trend is subject to uncertainty." # 91 les I think that Skywatchers contribution suffers from the same problem as the IPCC graph, namely comparing trends over periods of different length. -
Dikran Marsupial at 06:11 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
Helena/SRJ If you fit a linear model to the trends computed by SRJ, it will slope upwards, which implies that the rate of warming has increased over the period 1850-present, i.e. warming has on average been accellerating. As far as I can see SRJ's method is in agreement with the the IPCC diagram. -
tomfid at 06:10 AM on 15 May 2012There's no correlation between CO2 and temperature
Looking at temp-CO2 correlations is a bad idea for the very fundamental reason that temperature indicates the accumulation of forcing, so there is an integration between flow (CO2 forcing) and stock (heat or temperature). In general, you can't expect to see a correlation between a flow and stock time series, even when causality is perfect. It happens that some relationship is evident for CO2-temp because the time constant of surface heat is fairly short, but this is not terribly informative. This topic gives the impression that it's OK to look for temp-CO2 or forcing-CO2 correlations, if you just look for them the right way. It would be better if the message were that looking at stock-flow correlations (CO2-temp, or worse, emissions-temp) is basically misleading, unless you explicitly consider the dynamics. -
Helena at 06:02 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
... that's why when you start in 1850 (his graph2) the full 150yrs trend is so low even though you've just "added in" the massive 1970-2000 increase : the increase gets diluted by T. In the same way, when you start in the present (his graph1 and the IPCC), you're not being "fair" to the past as its trend gets mechanically diluted. You "force-flaten" long trends. That's why you can't compare trends that have different T. -
Helena at 05:49 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
les : "Just how someone thinks SRJ analysis is a good approach to the acceleration question and yet fail to acknowledge skywatchers contribution is, let's say, baffling. " skywatcher76 graph and method are already much better than the IPCC method, but they still have two flaws : - for science reasons : his method implies comparing different trends, thus having the problem of flattening long trends as you can see in the two graphs. You're then really not comparing the same thing (the slope of different trends) on the same graph as the slope is itself a function of the time period. His graphs seem to be 1D functions slope(t), but in fact they really are 2D functions slope(t,T). You would need to correct his graph for T. - for communication reasons : a decreasing decelerated temperature would look the same as his first graph (you would just be starting in the negatives), which is not very good if you want a clear picture. SRJ method addresses those two problems. (sorry for this last last message, but les was new to the discussion and had kind words on saying it was an interesting one) -
les at 05:23 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
Well, having followed this dialogue; I think it's worth letting the various contributors know that, frustrating as it may be, the general flow has been educational... Just how someone thinks SRJ analysis is a good approach to the acceleration question and yet fail to acknowledge skywatchers contribution is, let's say, baffling. -
otter17 at 05:07 AM on 15 May 2012Lindzen's Clouded Vision, Part 2: Risk
This one is getting bookmarked. It is nice to have a collection of some of the economic analyses in one place. It seems many that disagree with the scientific stance have an issue with the solutions, so I make it a point to get straight to the point. -
Dikran Marsupial at 05:05 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
SRJ wrote "and continued but not significant warming from 2003 to 2011" This is such a short period that one would not expect the observed trend to be statistically significant, even if it continued at the previous rate or even slightly higher. Looking at it the other way, there is no statistically significant evidence that the warming from 2003 to 2011 was less than from (say) 1980 to 2003. -
Dikran Marsupial at 05:00 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
The reservation I have about the IPCC graph is that a linear model is obviously not appropriate for timespans greater than 30 years or so, because of changes in forcings means that the residuals have structure, and so violate the modelling assumption. Not that big a deal as the fact is clearly evident in the plot and nobody is drawing any firm statistical conclusions from it. However the diagram is in a FAQ and is not intended to be part of the IPCC's scientific explanation or evidence of anything. It is obviously intended as an illustration designed to convey a basic point, which is that the rate of warming has been accellerating. There is a difference between the FAQs and the body of the report and Monckton surely knows that. -
Dikran Marsupial at 04:51 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
Helena, Just a thought, but trends ending at the current time tell you about the change in gradient (i.e. curvature) around the current time. Trends starting at (say) 1860 give you an indication of the change in gradient (i.e. curvature) around 1860, not the present date (note that the two differet sets of trends have a different common point, one is "today", the other is 1860). Hence it is no big surprise that the analysis gives a different result. -
Helena at 04:34 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
My last message here : you know my stand, it's useless to discuss it further, and (-snip-) Skywatcher : "Progressively increasing or decreasing gradients of the lines prove concavity of the curve" Gradients prove concavity yes, but 4 trends calculated on different time scales no. That's my whole point. Muon : I agreed to those three points (he yes/no questions) with .... you ! Not the IPCC ! There is no yes/no question in the legend of the IPCC graph, right ? You cannot start from saying it's an accelerated warming, then plot the 4 trends and say "well, the 4 trends increase, that surely indicates accelerated warming", that would be circular reasoning. What you must do is start with 4 increasing trends, not knowing anything else. What can you conclude from that ? My stand is : not much. KR: "As multiple posters have noted, a linear trend increasing over time is a clear indicator of acceleration " First, please note that Tom Curtis said : "Therefore this test [linear trend increasing over time] does not detect accelerating curves per se, but acceleration within a curve" You got 4 linear trends calculated. Can you really conclude or infer that the underlying curve depicts an accelerated warming ? SRJ : I support your method and i think your comment should replace or be added to the article on this website. It's sad the IPCC didn't use it and instead used one that can be rightfully criticized...Moderator Response:[DB] "It's sad the IPCC didn't use it and instead used one that can be rightfully criticized..."
As many have already pointed out, you have not "rightfully" proved this assertion.
Tone-trolling snipped.
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Composer99 at 04:17 AM on 15 May 2012101 responses to Ian Plimer's climate questions
Carbon500: What I get from "Whilst the global trend is one of warming, significant decadal variations have been observed in the global time series, and there are large regions where the oceans are cooling." is the oceans are warming The extra nuance in the more fleshed-out description does not alter the accuracy of the simpler one. Finally, I find your accusation of misleading terminology in the DCCEE response to Plimer is without merit. Any decrease in pH is necessarily an "increase in acidity" (which is why the change in ocean pH is "ocean acidification"), without regard to the final state of the system or entity in which the decrease has occured. -
SRJ at 04:14 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
I also do not like that figure from IPCC. I think it is comparing apples to oranges when trend lines over 150 years are compared with 25 year trend lines. Skywatchers graphs do the same, i.e. comparing trends over longer times with trends over shorter times. Consider replacing the trend with the mean. Would it make sense to compare the mean of the temperature over the last 150 years to the mean over the temperature over the last 25 years? What I would do is to calculate ALL 25 years trend over the entire lenght of the series, then plot these vs. end year. In that way, trends of equal lenght are compared I had already the code ready for this, using annual data for HadCru I get this plot, click to enlarge:
The 25 year trends are increasing up to 2005 (marked by a vertical line), from there on they are decreasing. However, the trends after 2005 are still positive and significant, so warming is indeed continuing.
Error bars shown are not corrected for autocorrelation.
In general, I do not like the concept of calculating trends on more or less arbitrary subsets of the data. Another approach using all the data to fit a generalized additive model is outlined by Gavin Simpson in a blog post here.
Using the code provided I have updated his graph, and it shows a significant warming until 2003, and continued but not significant warming from 2003 to 2011:
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Pete Wirfs at 02:59 AM on 15 May 20122012 SkS Weekly Digest #19
Nope, not intimidated. Pete -
otter17 at 01:46 AM on 15 May 20122012 SkS Weekly Digest #19
Issue of the Week: I think the authors and the people that comment here are great examples of civility and are excellent teachers. One just has to look at the succinct clarity in the 170 or so articles covering climate science myths to see what a great teaching service is provided. Some might feel intimidated if they see comments from someone that has no interest in learning about the peer review literature, but that isn't Skep Sci's fault. I have seen many examples of Skep Sci trying to put the science in understandable terms when posed a question from a non-expert. As an engineer, I have learned quite a bit, though I only pop in once in a great while to post my thoughts.. -
KR at 00:29 AM on 15 May 2012IPCC graph showing accelerating trends is misleading
skywatcher - Those are very informative graphs; well worth including in the main post on this thread. As multiple posters have noted, a linear trend increasing over time is a clear indicator of acceleration (with, albeit, increasing variations for shorter time periods, as seen in skywatchers graphs). Helena's objections are mathematically unsupportable, and the constant repetition is simply (IMO) trolling. And, returning to the original subject, Monckton's objections to the IPCC graph are in one sense incorrect (acceleration is definitely shown), and in another a strawman argument (the IPCC did not base the conclusion of anthropogenic influence on this graph). -
Bob Lacatena at 23:37 PM on 14 May 2012IPCC graph showing accelerating trends is misleading
Helena's pretentious "I'll teach you guys what I mean by my genius" attitude, combined with a very thorough lack of clarity and an unwillingness to reason -- only to lecture and malign -- suggests a trollish behavior that does not warrant feeding. You be the judge whether or not you think this is an accurate portrayal, but to me pursuing this conversation simply lets the troll grow larger and larger, until it breaks the very bridge it lives beneath. -
muoncounter at 23:06 PM on 14 May 2012IPCC graph showing accelerating trends is misleading
Helena#78: "where did we say that we were considering increasing functions ?" Here, where you agreed the curve under discussion is concave up. Here, where you agreed with 'increasing and accelerating', which I re-stated here. And here. This is now straightforward: a. If the temperature function over the period in question was increasing and linear, there would be no change in slope regardless of the interval used. b. If the temperature function was increasing and accelerating (which you agree means concave up), slopes starting in later periods would be greater (more positive) than slopes from periods starting earlier. Here is an illustration of this from first-year calculus:
The slope of the line crossing the curve at x=1 is the smallest. Subsequent lines have increasing slope. Subsequent lines cross the curve at x>1. The slope of the last line shown (purple) is calculated from a very small interval around x=2 and is the largest. Work it backwards: the pattern of lines is sufficient to infer the shape of the curve.
To insist otherwise at this point suggests you have an interest in prolonging this agonizing (and frankly uninteresting) back-and-forth.
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Bernard J. at 23:03 PM on 14 May 2012IPCC graph showing accelerating trends is misleading
"Helena" sounds like Girma Orssengo.
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