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Bern at 22:41 PM on 11 August 2010On Statistical Significance and Confidence
As has been mentioned elsewhere by others, given that the data prior to this period showed a statistically significant temperature increase, with a calculated slope, then surely the null hypothesis should be that the trend continues, rather than there is no increase? I guess it depends on whether you take any given interval as independent of all other data points... stats was never my strong point - we had the most uninspiring lecturer when I did it at uni, it was a genuine struggle to stay awake! -
chris1204 at 22:38 PM on 11 August 2010On Statistical Significance and Confidence
The data set contains two points which are major 'outliers' - 1996 (low) and 1998 (high). I appreciate 1998 is attributable to a very strong El Nino. Very likely, the effect of the two outliers is to cancel one another out. Nevertheless, it would be an interesting exercise to know the probability of a positive slope if either or both outliers were removed (a single and double cherry pick if you like) given the 'anomalous' nature of the gap between two temperatures in such a short space of time. -
Dikran Marsupial at 22:28 PM on 11 August 2010Has Global Warming Stopped?
fydijkstra A few points: (i) just because a flattening curve gives a better fit to the calibration data than a linear function does not imply that it is a better model. If it did then there would be no such thing as over-fitting. (ii) it is irellevant that most real world functions saturate at some point if the current operating point is nowhere near saturation. (iii) there is indeed no physical basis to the flattening model, however the models used to produce the IPCC projections are based on our understanding of physical processes. They are not just models fit to the training data. That is one very good reason to have more confidence in their projections as predictions of future climate (although they are called "projection" to make it clear that they shouldn't be treated as predictions without making the appropriate caveats). (iv) while low-order polynomials are indeed useful, just because it is a low-order polynomial does not mean that there is no over-fitting. A model can be over-fit without exactly interpolating the calibration data, and you have given no real evidence that your model is not over-fit. (v) your plot of the MDO is interesting as not only is there an oscillation, but it is super-imposed on a linear function of time, so it too goes off to infinity. (vi) as there is only 2 cycles of data shown in the graph, there isn't really enough evidence that it really is an oscillation, if nothing else it (implicitly) assumes that the warming from the last part of the 20th century is not caused by anthropogenic GHG emissions. If you take that slope away, then there is very little evidence to support the existence of an oscillation. (v) it would be interestng to see the error bars on your flattening model. I suspect there are not enough observations to greatly constrain the behaviour of the model beyond the calibration period, in which case the model not giving useful predictions. -
John Russell at 22:25 PM on 11 August 2010On Statistical Significance and Confidence
I hate to admit this -- I'm very aware some will snort in derision -- but as a reasonably intelligent member of the public, I don't really understand this post and some of the comments that follow. My knowledge of trends in graphs is limited to roughly (visually) estimating the area contained below the trend line and that above the trend line, and if they are equal over any particular period then the slope of that line appears to me to be a correct interpretation of the trend. That's why, to me, the red line seems more accurate than the blue line on the graph above. And this brings me to the problem we're up against in explaining climate science to the general public: only a tiny percentage (and yes, it's probably no more than 1 or 2 percent of the population) will manage to wade through the jargon and presumed base knowledge that scientists assume can be followed by the reader. Some of the principles of climate science I've managed to work out by reading between the lines and googling -- turning my back immediately on anything that smacks just of opinion and lacks links to the science. But it still leaves huge areas that I just have to take on trust, because I can't find anyone who can explain it in words I can understand. This probably should make me prime Monckton-fodder, except that even I can see that he and his ilk are politically-motivated to twist the facts to suit their agenda. Unfortunately, the way real climate science is put across, provides massive opportunities for the obfuscation that we so often complain about. Please don't take this personally, Alden; I'm sure you're doing your best to simplify -- it's just that even your simplest is not simple enough for those without the necessary background. -
Berényi Péter at 20:55 PM on 11 August 2010Temp record is unreliable
#109 kdkd at 19:37 PM on 11 August, 2010 Your approach still gives the appearance of cherry picking stations You are kidding. I have cherry picked all Canadian stations north of the Arctic Circle that are reporting, that's what you mean? Should I include stations with no data or what? How would you take a random sample of the seven (7) stations in that region still reporting to GHCN every now and then? 71081 HALL BEACH,N. 68.78 -81.25 71090 CLYDE,N.W.T. 70.48 -68.52 71917 EUREKA,N.W.T. 79.98 -85.93 71924 RESOLUTE,N.W. 74.72 -94.98 71925 CAMBRIDGE BAY 69.10 -105.12 71938 COPPERMINE,N. 67.82 -115.13 71957 INUVIK,N.W.T. 68.30 -133.48 BTW, here is the easy way to cherry pick the Canadian Arctic. Hint: follow the red patch. -
fydijkstra at 20:43 PM on 11 August 2010Has Global Warming Stopped?
In my comment #20 I showed that the data fit better to a flattening curve than to a linear line. This is true for the last 15 years, but also for the last 50 years. I also suggested a reason why a flattening curve could be more appropriate than a straight line: most processes in nature follow saturation patterns instead of continuing ad infinitum. Several comments criticized the polynomial function that I used. ‘There is no physical base for that!’ could be the shortest and most friendly summary of these comments. Well, that’s true! There is no physical basis for using a polynomial function to describe climatic processes, regardless of which order the function is, first (linear), second (quadratic) of higher. Such functions cannot be used for predictions, as Aldin also states: we are only speaking about the trend ‘to the present’. Aldin did not use any physical argument in his trend analysis, and neither did I, apart from the suggestion about ‘saturation.’ A polynomial function of low order can be very convenient to reduce the noise and show a smoothed development. Nothing more than that. It has nothing to do with ‘manipulating [as a] substitute of knowing what one is doing’ (GeorgeSP, #61). A polynomial function should not be extrapolated. So far about the statistical arguments. Is there really no physical argument why global warming could slow down or stop? Yes there are such arguments. As Akasofu has shown, the development of the global temperature after 1800 can be explained as a combination of the multi-decadal oscillation and a recovery from the Little Ice Age. See the following figure.
The MDO has been discussed in several peer-reviewed papers, and they tend to the conclusion, that we could expect a cooling phase of this oscillation for the coming decades. So, the phrase ‘global warming has stopped’ could be true for the time being. The facts do not contradict this.
What causes this recovery from the Little Ice Age, and how long will this recovery proceed? That could be a multi century oscillation. When we look at Roy Spencers ‘2000 years of global temperatures’ we see an oscillation with a wavelength of about 1400 years: minima in 200 and 1600, maximum in 800. The next maximum could be in 2200.
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John Brookes at 19:43 PM on 11 August 2010On Statistical Significance and Confidence
Another interesting way to look at it is to look at the actual slope of the line of best fit, which I get to be 0.01086. Now take the actual yearly temperatures and randomly assign them to years. Do this (say) a thousand times. Then fit a line to each of the shuffled data sets and look at what fraction of the time the shuffled data produces a slope of greater than 0.01086 (the slope the actual data produced). So for my first trial of 1000 I get 3.5% as the percentage of times random re-arrangement of the temperature data produces a greater slope than the actual data. The next trial of 1000 gives 3.5% again, and the next gave 4.9%. I don't know exactly how to phrase this as a statistical conclusion, but you get the idea. If the data were purely random with no trend, you'd be expecting ~50%. -
kdkd at 19:37 PM on 11 August 2010Temp record is unreliable
BP #108 Your approach still gives the appearance of cherry picking stations. As I said previously, you need to make a random sample of stations to examine. Individual stations on a global grid are not informative, except as curiosities :) -
Berényi Péter at 18:59 PM on 11 August 2010Temp record is unreliable
This one is related to the figure above. It's adjustments to GHCN raw data relative to the Environment Canada Arctic dataset (that is, difference between red and blue curves).
Adjustment history is particularly interesting. It introduces an additional +0.15°C/decade trend after 1964, none before.
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gallopingcamel at 16:30 PM on 11 August 2010Why I care about climate change
Some great posts! Here are a few comments: macoles (#123 & #124), The irony was unintended. For me the establishment/consensus is often wrong whether it be based on religion or science. It is in my nature to question authority whether it is based on church, ideology or science. muoncounter (#125), Like you, I care about the teaching of science in K-12 as well as college level. In my state, there are 370 high schools but less than 40 teachers with physics degrees teaching science. The quality of science text books is critical when so few teachers have an adequate background in the subject. I hope you will want to support John Hubisz in his efforts to improve science text books: http://www.science-house.org/middleschool/ doug_bostrom (#126) In Newton's day they used to talk about "Laws" but modern physicists understand that they are always wrong even though their theories often have great predictive power. The perihelion of Mercury does precess as Einstein predicted, GPS systems need relativistic corrections and the energy released from nuclear reactions appears to follow the E=mc2 relationship. In spite of all this success, Einstein understood the limitations of his theories better than the folks at Conservapedia. muoncounter (#127), Loved the cartoon (how did I miss it?). At least one more pane needed for evolution vs. creationism. -
rcglinski at 16:12 PM on 11 August 2010Models are unreliable
Do any climate models have substantial agreement with the last century of precipitation data? -
rcglinski at 15:42 PM on 11 August 2010CO2 was higher in the past
Thanks Doug. -
Doug Bostrom at 14:10 PM on 11 August 2010Models are unreliable
Fun! Schmidt and Knappenberger are found at Annan's blog, discussing M&M 2010. Minor celebrities For extra credits in "Climate Science Arcana" coursework, follow the "old dark smear" links at the top of Annan's post. Those have a bit of useful background material to the M&M 2010 treatment of Santer 2008, to do with RPjr. If you have a clue what that's all about, you spend too much time on climate blogs. -
Doug Bostrom at 12:00 PM on 11 August 2010Grappling With Change: London and the River Thames
Further to HR's remarks, I see that it's actually quite easy to find publications indicating some changes in storm behavior and frequency in the North Atlantic. I should not so easily conclude that I can't contribute a little further information here. Increasing destructiveness of tropical cyclones over the past 30 years A shift of the NAO and increasing storm track activity over Europe due to anthropogenic greenhouse gas forcing Heightened tropical cyclone activity in the North Atlantic: natural variability or climate trend? Trends in Northern Hemisphere Surface Cyclone Frequency and Intensity As the London folks noted, this information is in keeping w/predictions. As they also noted, while no particular storm can be linked to climate forcing it would not be prudent to ignore an emerging pattern of observed evidence of a predicted trend. HR, this exercise leads me to suggest you ask yourself, "Why did I talk about sea level change over the past 30 years when our topic is about sea level rise over the next 100+ years? Why am I trying so hard to ignore what's in front of me?" -
Don Gisselbeck at 11:58 AM on 11 August 2010More evidence than you can shake a hockey stick at
The record low in Guinea is interesting. I was a Peace Corps volunteer in neighboring Sierra Leone in the late 70s. Several of my students were from Guinea and had seen ice form on open water during the Harmattan. -
Doug Bostrom at 11:39 AM on 11 August 2010CO2 was higher in the past
Robert I don't see anything unusual there. WUWT folks are angry because some poor scientist found out something boxing them in a little bit more. -
apeescape at 11:33 AM on 11 August 2010On Statistical Significance and Confidence
Thanks for this, you have a great website. btw, did you check out the Bayes factor relative to the "null"? -
robert test at 11:02 AM on 11 August 2010CO2 was higher in the past
Watts has just posted a new article http://wattsupwiththat.com/2010/08/10/study-climate-460-mya-was-like-today-but-thought-to-have-co2-levels-20-times-as-high/ It refers to a new study in PNAS http://www.pnas.org/content/early/2010/08/02/1003220107.abstract?sid=08063fb7-c9e9-48d7-a515-b3db8907505c Hope you can comment on this soon. -
Doug Bostrom at 10:52 AM on 11 August 2010Grappling With Change: London and the River Thames
I'm not the person to deal with your points, HR, I'm the wrong person to challenge. You're in disagreement with experts having more knowledge of this topic than either of us. What I can surmise based on what I've read of our processes of cognition is that your disagreement with people knowing more of the topic of operating the Thames Barrier than the both of us suggests you're unwilling to confront information that makes you uncomfortable. I can't think of any other explanation. By the way, you're by no means unique or even at fault for having a hard time dealing with risk. As far as researchers can tell so far it's a universal trait of humans. -
HumanityRules at 10:42 AM on 11 August 2010Grappling With Change: London and the River Thames
30.doug_bostrom at 11:45 AM on 5 August, 2010 Doug it's a little weak to suggest the data I presented is just an aspect of a psycological problem I have. There is no significant trend for storminess in the North Sea that I can find published. The list of Thames barrier closures shows a downward trend in the surge and High Water Level readings during closure events suggesting the barrier is being closed for less severe events. Ocean levels have risen how much in the last 3 decades? 10cm? There is no justification to suggest the very large increase in barrier closures has anything to do with real changes in climate. Deal with the points rather than my mental state. -
Berényi Péter at 10:38 AM on 11 August 2010Temp record is unreliable
#102 Ned at 06:50 AM on 11 August, 2010 I thought it would be worth putting up a quick example to illustrate the necessity of using some kind of spatial weighting when analyzing spatially heterogeneous temperature data OK, you have convinced me. This time I have chosen just the Canadian stations north of the Arctic Circle from both GHCN and the Environment Canada dataset.
The divergence is still huge. Environment Canada shows no trend whatsoever during this 70 year period, just a cooling event centered at the early 1970s, while GHCN raw dataset is getting gradually warmer than that, by more than 0.5°C at the end, creating a trend this way.
No amount of gridding can explain this fact away.
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Doug Bostrom at 10:18 AM on 11 August 2010CO2 was higher in the past
Here's an excellent writeup on main sequence stars rcglinksi. -
rcglinski at 10:10 AM on 11 August 2010CO2 was higher in the past
How is solar heat output determined for periods before direct measurement? I ask because the article says solar output was 4% lower during the Ordovician but I can't tell how the number was arrived at. -
Chris Winter at 09:41 AM on 11 August 2010Antarctica is gaining ice
Thanks for pointing this out over at CP. There, I made the assumption that "sea ice" meant floating icebergs. My bad. -
andrewcodd at 09:38 AM on 11 August 2010Models are unreliable
There is a trade off betweeen concern for the most vulnerable and mistrust of governments. I am not a confirmed beleiver in the network of socialists doctoring results for their trotskyite masters. That said inevitably there will be incidences where the responsability of stewardship weighs heavy on scientific rigour. The code should be available so we can move on. We all agree models will be better in the future. Not to heed what they are currently delivering is an imprudency beyond recall. -
Daniel Bailey at 09:32 AM on 11 August 2010On Statistical Significance and Confidence
Good post, Alden. Communicating anything to the public does indeed require a minimal usage of jargon; but as we all know, there exist those who live to be contrarians, for whom no level of clear explanations exist that cannot be obfuscated. Thanks again! The Yooper -
Stephan Lewandowsky at 09:31 AM on 11 August 2010On Statistical Significance and Confidence
I would appreciate some more background on how you computed the Bayesian credible interval. For example, what exactly do you mean my non-informative prior? Uniform? And how did you deal with auto-correlations if at all? (I realize that I am asking for the complexity you seek to simplify--fair enough, but a 'technical appendix' might be helpful for those more conversant with statistics.) -
Peter Hogarth at 08:55 AM on 11 August 2010Models are unreliable
Pete Ridley at 07:12 AM on 11 August, 2010 I'm guessing you read the comments and not the details of the paper? The paper itself is interesting, as M,M&H confirm that tropical Lower Troposhere temperature trends from 1979 to end of 2009 are significantly positive, and to an extent reflect the earlier views in Santer 2008. See my comment on tropospheric hot-spot for some background on this. At the time of writing that comment I suggested that the inclusion of the 2010 data would allow the trends to more closely approach statistical “robustness”, so confirmation is a useful step. They also confirm the known issues with the earlier models used by Santer, and also confirm that the differences between the UAH and RSS MSU datasets are now statistically significant. For the Tropical Lower Troposphere temperature data they quote “In this case the 1979-2009 interval is a 31-year span during which the upward trend in surface data strongly suggests a climate-scale warming process”. That the original model was flawed in this case is old news, and this has been discussed here previously. I note once again some of your sources (and the comments on this new paper) lack context and scientific objectivity. -
Berényi Péter at 08:54 AM on 11 August 2010Temp record is unreliable
#105 Peter Hogarth at 07:58 AM on 11 August, 2010 Bekryaev lists all sources (some of them available for the first time), the majority with links, though I admit I haven't followed them all through. Show us the links, please. I am surprised you make comments without even looking at the paper. Anyway, I genuinely thought you might be interested. I am. However, I would prefer not to pay $60 just to have a peek what they've done. I am used to the free software development cycle where everything happens in plain public view. #104 Ned at 07:11 AM on 11 August, 2010 Obviously, stations in northern Canada are mostly warming faster than those further south I see that. However, that does not explain the fact the bulk of divergence between the three datasets occurred in just a few years around 1997 while the sharp drop in Canadian GHCN station number happened in July, 1990. Anyway, I have all the station coordinates as well, so a regional analysis (with clusters of stations less than 1200 km apart) can be done as well. But I am afraid we have to wait for that as I have some deadlines, then holidays as well. -
dorlomin at 08:32 AM on 11 August 2010More evidence than you can shake a hockey stick at
Does anyone know the cause of the dip in CO2 concentrations on the slide featured in post 15, the dip being about 1500 AD. -
Doug Bostrom at 08:27 AM on 11 August 2010Greenland's ice mass loss has spread to the northwest
Fascinating article about Greenland here in the UK's Daily Mail. A reporter visits scientists working this summer on the ice sheet, investigating drainage. Some great photos. -
Doug Bostrom at 08:03 AM on 11 August 2010Models are unreliable
Pete, worth noting also that you won't find a refutation to M&M 2010 coming from here, you'll find it reported if and when such a refutation appears. The sites you mention are in full celebration but of course they're not adding any information of their own, the actual information is all in the paper itself. Hopefully for M&M the air the party won't be over before their work actually appears in print. :-) -
Peter Hogarth at 07:58 AM on 11 August 2010Temp record is unreliable
Berényi Péter at 07:07 AM on 11 August, 2010 Thanks for fixing the links, though I think Ned has actually answered one question I had quite efficiently. I'm not sure what it is I still don't get? (why so defensive?) Bekryaev lists all sources (some of them available for the first time), the majority with links, though I admit I haven't followed them all through. I am surprised you make comments without even looking at the paper. Anyway, I genuinely thought you might be interested. -
Doug Bostrom at 07:55 AM on 11 August 2010Models are unreliable
I might add as a gratuitous fling, the amount of back-slapping and rejoicing around M&M's first accepted comment in years is indicative of the general poverty of their camp. Looking at the comment threads erupting around this I'm reminded of meat being thrown into a kennel full of emaciated dogs. Folks outside the kennel have more to eat than they care to look at, frankly, are amply fed with dismal facts. Less gratuitously, this publication immediately moves me to point out that not everybody can feed from the meal on offer. Those who've committed themselves to trying to show the temperature observations under discussion are meaningless will have to go hungry unless they disagree w/M&M. Those saying there's no trend will also have to continue listening to their stomachs rumbling, because again M&M's results depend on observing a trend. -
Pete Ridley at 07:46 AM on 11 August 2010Confidence in climate forecasts
For some reason my earlier post of this comment was removed so I’ve modified it slightly. I can’t see any violation of the comments policy.Moderator Response: Putting duplicate comments into multiple threads leads to incoherent discussion. -
Doug Bostrom at 07:38 AM on 11 August 2010Models are unreliable
James Annan comments on M&M's comment as published in ASL: A commenter pointed me towards this which has apparently been accepted for publication in ASL. It's the same sorry old tale of someone comparing an ensemble of models to data, but doing so by checking whether the observations match the ensemble mean. Well, duh. Of course the obs don't match the ensemble mean. Even the models don't match the ensemble mean - and this difference will frequently be statistically significant (depending on how much data you use). Is anyone seriously going to argue on the basis of this that the models don't predict their own behaviour? If not, why on Earth should it be considered a meaningful test of how well the models simulate reality? Of course the IPCC Experts did effectively endorse this type of analysis in their recent "expert guidance" note, where they remark (entirely uncritically) that statistical methods may assume that "each ensemble member is sampled from a distribution centered around the truth". But it's utterly bogus nevertheless, as there is no plausible situation in which that can occur, for any ensemble prediction system, ever. Having said that, IMO a correct comparison of the models with these obs does show the consistency to be somewhat tenuous, as we demonstrated in that (in)famous Heartland presentation. It is quite possible that they will diverge more conclusively in the future. Or they may not. They haven't yet. Annan Should be quite a stir out of this, papers of this sort being few and far between. Worth noting that Annan is an unflinching critic of whatever he sees wrong w/IPCC, etc. Probably a useful snapshot metric of the significance of M&M's output here. -
Pete Ridley at 07:12 AM on 11 August 2010Models are unreliable
Jo Nova’s blog has an interesting new article “The models are wrong (but only by 400%) ” (Note 1) which you should have a look at, along with the comments. It covers the recent paper “Panel and Multivariate Methods for Tests of Trend Equivalence in Climate Data Series” (Note 2) co-authored by those well-known and respected expert statisticians, McIntyre and McKitrick, along with Chad Herman. David Stockwell sums up the importance of this new paper with “This represents a basic validation test of climate models over a 30 year period, a validation test which SHOULD be fundamental to any belief in the models, and their usefulness for projections of global warming in the future”. David provides a more detailed comment on his Niche Modeling blog “How Bad are Climate Models? Temperature” thread (Note 3) in which he concludes “But you can rest assured. The models, in important ways that were once claimed to be proof of “… a discernible human influence on global climate”, are now shown to be FUBAR. Wouldn’t it have been better if they had just done the validation tests and rejected the models before trying to rule the world with them?”. Come on you model worshipers, let’s have your refutation of the McIntyre et al. paper. NOTES: 1) see http://joannenova.com.au/2010/08/the-models-are-wrong-but-only-by-400/#more-9813 2) see http://rossmckitrick.weebly.com/uploads/4/8/0/8/4808045/mmh_asl2010.pdf 3) see http://landshape.org/enm/how-bad-are-climate-models/ Best regards, Pete Ridley -
Ned at 07:11 AM on 11 August 2010Temp record is unreliable
That map from my previous comment also nicely illustrates the conceptual flaw in the claim (by Anthony Watts, Joe D'Aleo, etc.) that the observed warming trend is an artifact of a decline in numbers of high-latitude stations. Obviously, stations in northern Canada are mostly warming faster than those further south. So, if you did use a non-spatial averaging method, dropping high-latitude stations would create an artificial cooling trend, not warming. Using gridding or another spatial method, the decline in station numbers is pretty much irrelevant (though more stations is of course preferable to fewer). -
Berényi Péter at 07:07 AM on 11 August 2010Temp record is unreliable
#101 Peter Hogarth at 04:25 AM on 11 August, 2010 some of the links seems to be broken? Yes, two of them, sorry.- GHCN data
- March, 1840 file at Environment Canada - this one only contains a single record for Toronto, but shows the general form of the link and structure of records
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Ned at 06:50 AM on 11 August 2010Temp record is unreliable
Berényi Péter writes: Unfortunately I do not have too much time for this job, you may have to wait a bit. Like Berényi Péter, I also don't have a lot of time right now, being about to leave for vacation in a few days and having far too much to do. But I thought it would be worth putting up a quick example to illustrate the necessity of using some kind of spatial weighting when analyzing spatially heterogeneous temperature data. Since BP uses Canada as his example, I'll do the same. He mentions a useful data source, the National Climate Data and Information Archive of Environment Canada. I'll use the same data source. Since I want to get this out quickly, I'm just using monthly mean temperature data from July, and as another shortcut I'll just look at every 5 years (i.e., 2010, 2005, 2000, 1995, ...) I picked July because it's the most recent complete month and 5-year intervals for no particular reason. Maybe sometime later I can expand this to look at the complete monthly data set. In any case, using just one month per 5 year interval will make this analysis more "noisy" than it would otherwise be, but that's OK. I then identified all stations with data in all years, and whose name and geographic coordinates were exactly the same in all years. There's just over 150 of them:
Note, first, that the stations aren't distributed uniformly.
Note, second, that the trends differ greatly in different regions.
In particular, note that there are a large number of stations showing cooling in inland southwestern Canada. There are also a lot of stations showing warming across eastern and northern Canada.
(This is an Albers conical equal-area projection, so the apparent density of stations is proportional to their actual density on the landscape).
If you calculate the trend for each station, and then just take the overall non-spatial average, you get a slight cooling of about -0.05C/decade for Julys in the 1975-2010 period.
But as the map shows, that's quite unrealistic as an estimate of the trend for the country as a whole! The large number of tightly-clustered stations in certain areas outweighs the smaller number of stations that cover much larger areas elsewhere.
To estimate the spatially structured temperature trend I used a fairly simple kriging method. This models a continuous surface based on the irregularly distributed station data. There are many other approaches that could be used (e.g., gridding, other interpolation methods, etc). Anyway, the spatially weighted trend across all of Canada is warming of +0.18C/decade.
So ... a naive nonspatial analysis of these data give an erroneous "cooling" of -0.05C/decade. A spatially weighted analysis gives a warming of +0.18C/decade.
This is why I keep telling Berényi Péter that his repeated attempts to analyze temperature data using simple, nonspatial averages are more or less worthless.
Again, this is based on a small fraction of the overall data set, and a not necessarily optimal methodology. But it's sufficient to show that using real-world data you can end up with seriously misleading results if you don't consider the spatial distribution of your data.
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muoncounter at 05:25 AM on 11 August 2010Why I care about climate change
Doug, You have made my day. Knowledge of the existence of such a thing as 'conservapedia' enriches my existence. I suggest to anyone not willing to believe in relativity that they immediately forfeit their GPS units. Given these remarks about quantum mechanics, "Collapsing of the wave function is by no means magic. In can be intuitively understood as this: You find a particle at a particular spot; if you look again immediately, it's still in the same spot, they should also forfeit all semiconductor-based electronics. Of course, they have wonderful things to say about global warming: "The anthropogenic global warming theory is one of several explanations for the 1.5 degrees F of warming of the earth's surface recorded since the middle of the 19th century. The theory enjoys broad based political support from Liberals, Greens and the US Democratic Party, and theory supporters frequently assert the existence of a "scientific consensus" favoring their viewpoint" Not too long ago (during the height of the ID debate in the US), this was a popular cartoon in the world of science education:
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Peter Hogarth at 04:35 AM on 11 August 2010Grappling With Change: London and the River Thames
doug_bostrom at 04:22 AM on 11 August, 2010 Agreed. -
Doug Bostrom at 04:32 AM on 11 August 2010Grappling With Change: London and the River Thames
Pete if you don't mind I'll refer to something you said in relation to Ned's recent post, as support for a general observation. Pete said: I may be able to make time for a further read but looking at some of the over 200 references mentioned there to “uncertainties” and “estimates” about those horrendously complex global climate processes and drivers gives me a hint that I’ll be wasting valuable time. I was disappointed to see virtually nothing about assumptions made. Looking beyond the immediate topic of sea level rise, Ned's remark exactly illustrates how Pete's reasoning about "wasting time" looking at citations is incorrect, and how his remark about seeing "virtually nothing about assumptions made" is not actually right. We have to look at all the information made available to us if we want to avoid ambiguities leading to fallacious conclusions. If we choose not to or cannot find the time to do so, that's not an argument against the worth of what we personally don't know. Personalizing this, for the article above I made a best effort to summarize what I was able to find from a variety of authoritative sources on London and floods. If I missed something in my research leading to errors in my little essay, that doesn't mean I'm right and the rest of the world is wrong, it simply means I'm ignorant of certain things. Ignorance is universal and thus permissible but we should deal with ignorance in a conservative way; I should not claim that because I don't know something nobody else does, or that my perspective is correct when I have cause to believe I don't have a complete grasp of my topic. I should be mindful of accidentally conveying and promoting misperceptions springing from my ignorance. -
Peter Hogarth at 04:25 AM on 11 August 2010Temp record is unreliable
Berényi Péter at 23:54 PM on 10 August, 2010 Peter, some of the links seems to be broken? Anyway, does your first chart represent published results or just your own analysis? If you are interested in Arctic surface station records have a look at Bekryaev 2010 which uses data from 441 high latitude and Arctic surface stations. -
Doug Bostrom at 04:22 AM on 11 August 2010Grappling With Change: London and the River Thames
Not to prematurely consign my article to the dustbin of history but the topic of accuracy of sea level measurements is already treated here on SkS and includes some helpful discussion around confusion concerning sea level measurement and the like. Rather than reenacting that history here, perhaps it would be better to contribute to existing threads. "How much is sea level rising" has a well developed discussion on measurement uncertainties. There's also "How much will sea levels rise in the 21st Century?", devoid of discussion but with a writeup by John Cook including data to work from, probably more germane to the exact discussion that has arisen here.Moderator Response: Excellent suggestion. This is one of those cases in which an original post on a broad topic legitimizes comments on all those topics, but at some point the comments get so detailed that continuation on that original thread no longer is appropriate. Everyone is welcome to post a comment on this thread, announcing that they have posted a comment on a more specialized, relevant thread. I suggest you even paste a link to your comment on that other thread. (Right click on the time-date stamp of your comment on the other thread.) -
Ned at 04:13 AM on 11 August 2010Grappling With Change: London and the River Thames
Let's see. In these two comments (first, second) Pete Ridley suggests that we should use data from a network of 12 GPS stations in the South Pacific to look at sea level rise. He also dismisses global studies of sea level based on the combination of satellite altimetry and gauge data. The satellite record shows a global trend of around +3.3 mm/year over the past two decades (thanks, Peter Hogarth!) The South Pacific GPS network that Pete Ridley refers to shows individual trends ranging from +3.2 to +8.6 mm/year (ignoring one outlier of +16.8 mm/year). The mean is +5.4 mm/year and the median is +4.9 mm/year. So, the network of stations that Pete Ridley was recommending actually shows a rate of rise that's about 50% greater than the global mean from the satellite record. However, as noted in the annual reports on the South Pacific GPS project, sea level in that region is known to be rising faster than the global average, and this regional difference shows up in the altimetry data as well. Taking this regional difference into account, their annual reports conclude that: The net sea level trends are positive at all sites, which indicates sea level in the region has risen over the duration of the project. The sea level rise is not geographically uniform but varies spatially in broad agreement with observations taken by satellite altimeters over a similar timeframe. [...] The sea level trends from SEAFRAME stations are mostly higher than the global average rate, but this is consistent with higher rates in the southwest Pacific measured by satellite altimeters So, if Pete Ridley likes the South Pacific CGPS project, he must also approve of the global satellite-based sea level record, since the two data sets are mutually consistent. Surely Mr Ridley isn't arguing that the satellite altimeters are accurate over the South Pacific but inaccurate over the rest of the ocean..... -
Doug Bostrom at 03:53 AM on 11 August 2010Why I care about climate change
Further to muoncounter's remarks, one of my concerns about this brouhaha over climate science is how the tactics employed to degrade public confidence in climate research necessarily can't and don't respect borders of inquiry. If somebody becomes the victim of purposeful confusion about the difference between hypothesis and theory or what "uncertainty" means in terms of confidence in scientific findings they're going to carry that loss of coherence everywhere they go, see everything through the same fuzzy cloud. Leading to things like this: The equations for special relativity assume that it is forever impossible to attain a velocity faster than the speed of light and that all inertial frames of reference are equivalent, hypotheses that can never be fully tested. Relativity rejects Newton's action at a distance, which is basic to Newtonian gravity and quantum mechanics. The mathematics of relativity assume no exceptions, yet in the time period immediately following the origin of the universe the relativity equations could not possibly have been valid. ... Relativity has been met with much resistance in the scientific world. To date, a Nobel Prize has never been awarded for relativity. Louis Essen, the man credited with determining the speed of light, wrote many fiery papers against it such as The Special Theory of Relativity: A Critical Analysis.[6] Relativity also gravely conflicts with quantum mechanics, and although theories like string theory and quantum field theory have attempted to unify relativity and quantum mechanics, neither has been entirely successful or proven. ... Despite censorship of dissent about relativity, evidence contrary to the theory is discussed outside of liberal universities. ... The Theory of Relativity enjoys a disproportionate share of federal funding of physics research today. Conservapedia article "Theory of Relativity" Sound familiar? -
Phila at 03:52 AM on 11 August 2010Remember, we’re only human
Typo alert: I meant to say "The Isles of Britain can't and don't support their population." -
Phila at 03:45 AM on 11 August 2010Remember, we’re only human
Humanity Rules: "Yep Malthus was wrong. He believed the Isles of Britain could not support more than 7 million people. He was wrong." The Isles of Britain can't and don't support more than 7 million people. The resources that actually support its population come from all over the globe, just like the resources that support other first-world countries. The population of Tokyo, for instance, is "supported" by a land area that's roughly three times greater than the land area of Japan. This situation is extremely vulnerable to various types of climactic disruption, wholly apart from the fact that we're running an unsustainable ecological deficit. Hope is not a plan, as the saying is. -
Peter Hogarth at 03:04 AM on 11 August 2010Grappling With Change: London and the River Thames
Pete Ridley at 00:26 AM on 11 August, 2010 All of the recent global sea level analyses use similar high resolution tide gauge data, as well as GPS/satellite altimetry as in the South Pacific Project. There is a global integrated sea level monitoring system and the South Pacific stations are part of it. In my view you have been extremely selective in your choice of references on sea level. Have a look at this short article on sea level rise where I cite the main recent references available in early 2010, and incidentally provide some visual clues as to why sea level rise in the South Pacific is not representative of sea level rise globally, notwithstanding that a 15 year period is less likely to give statistically significant trends when analysing individual stations (this seems to be a tactic often used by skeptics) as has been done in your reference. I could cite you many individual tide stations where sea level has actually fallen over the entire satellite recording period, but this does not change the global result. I suggest you gain much more knowledge of climate data and recent scientific research, and then balance this against the minority views of Spencer.
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