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Post by marchesarosa on Jul 4, 2011 8:57:12 GMT 1
I am reposting this excellent paper again because it is really worth reading and even those who don't follow the equations can follow the gist of the arguments. www.uoguelph.ca/~rmckitri/research/globaltemp/GlobTemp.JNET.pdfDoes a Global Temperature Exist? by Christopher Essex Department of Applied Mathematics University of Western Ontario Ross McKitrick Department of Economics University of Guelph Bjarne Andresen Niels Bohr Institute University of Copenhagen J. Non-Equilibrium Thermodynamics (in press, June 2006) Abstract Physical, mathematical and observational grounds are employed to show that there is no physically meaningful global temperature for the Earth in the context of the issue of global warming. While it is always possible to construct statistics for any given set of local temperature data, an infinite range of such statistics is mathematically permissible if physical principles provide no explicit basis for choosing among them. Distinct and equally valid statistical rules can and do show opposite trends when applied to the results of computations from physical models and real data in the atmosphere. A given temperature field can be interpreted as both “warming” and “cooling” simultaneously, making the concept of warming in the context of the issue of global warming physically ill-posed. Short title: Global Temperature? ----------- The gist is that temperatures everywhere are going up and down for different reasons and averaging them is a nonsense.
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Post by marchesarosa on Jul 4, 2011 9:36:52 GMT 1
I came across this neat example of the perils of averaging in my reading.
Say there are 28 bunches of red currants on a bush varying in number of currants per cluster from 1 to 7, To find the average number of currants per bunch you add them up. This total corresponds to something REAL - the number of currants in the basin - which can then be divided by the number of bunches. You may not get get a whole number of currants in the average bunch but, hey, you are in the right ball park and you can divide up the berries into 28 equal portions that 28 folk can eat and enjoy!
When you take the first step in this process to average a temperature what do you have? Not the equivalent of a basinful of currants that you can eat. Oh, no! Temperature in Leeds may be 18 degreesC and in London 22 degreesC. Does the total of 40 degreesC correspond to anything? No.
Even when you average it by dividing by 2 you get a number that doesn't correspond to anything in either Leeds or London, or anywhere predictable inbetween, that someone can feel.
That's the gist of it really.
Currants can be added up and divided to get an average that you can EAT, Leeds and London temperatures cannot be added and up and divided to get an average that anyone in either Leeds or London can FEEL. And so on to the global scale.
Apparently, the difference between currants and degrees C is that the former possess an "extensive" property and the latter an "intensive" property - the former is amenable to meaningful averaging and the latter is not.
But, PLEASE, read the Essex, McKitrick and Andresen paper above - they explain it so much better than I can and then you will realise you need never heed the "global mean temperature" again but simply concentrate on the all-important local ones!
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Post by marchesarosa on Jul 4, 2011 9:41:54 GMT 1
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Post by StuartG on Jul 4, 2011 9:48:36 GMT 1
I read the post MM, and immediately, and before reading [and trying to understand] the .pdf, took to Google to find who the 'naysayers' at the time might be. With a date of 25 Mar 2007 the first entry is RealClimate where it says... "The common arithmetic mean is just an estimate that provides a measure of the centre value of a batch of measurements (centre of a cloud of data points, and can be written more formally as the integral of x f(x) dx. The whole paper is irrelevant in the context of a climate change because it missed a very central point. CO2 affects all surface temperatures on Earth, and in order to improve the signal-to-noise ratio, an ordinary arithmetic mean will enhance the common signal in all the measurements and suppress the internal variations which are spatially incoherent (e.g. not caused by CO2 or other external forcings)" www.realclimate.org/index.php/archives/2007/03/does-a-global-temperature-exist/ I suppose is logic and argument is OK, providing it is accepted that CO2 is the main culprit, that appears to be the 'foundation' of rasmus's argument. Is it correct? StuartG
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Post by marchesarosa on Jul 4, 2011 10:26:24 GMT 1
Well, the McKitrick et al paper may have been "irrelevant to the context of a climate change" but it wasn't discussing "climate change" was it, stu? It was enlightening us about the meaninglessness of the concept of a "global mean temperature". And I think it did that very well.
It's the temperature (and other stuff) where we are that is important and that we have to plan for - simple, idea, I know, but true!
And always remember, climate doesn't kill people, weather does!
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Post by StuartG on Jul 4, 2011 10:58:49 GMT 1
Yes, I agree, but thought that I may play the 'devils advocate' in this case. [before anyone else did] I see these arguments for GAT as a parallel to Global Average Sea-level [GAS?]. The thing about sea level is that it is 'tangible' in that it and its effects can be seen. StuartG
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Post by marchesarosa on Jul 4, 2011 14:58:34 GMT 1
Yes, I know you were pre-empting the alarmist strike, stu.
Coastal sea level (as measured by the trusty tide gauges) is the only "tangible" we need be concerned with, stu - not the ever-deepening ocean basins nor the volume of water in them that we have recently been bedazzled with by Boulder!
The alarmists really do take us for illiterates, don't they?
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Post by StuartG on Jul 4, 2011 16:31:22 GMT 1
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Post by marchesarosa on Jul 4, 2011 17:05:04 GMT 1
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Post by speakertoanimals on Jul 5, 2011 14:34:53 GMT 1
Except I think the point also is that is what is computed is NOT global mean temperature (although physicsts doing a back of the envelope calculation of thermal radiation received versus thermal radiation emitted would happily compute some sort of mean as a first estimate of the 'temperature' of Earth without global warming............), but mean of deviations.
That isn't quite the point either. As I think I've said before, Chiefio got it totally WRONG when he tried to discuss this. The Essex paper IS very technical, and the simple arguments (although sounding meaningful to the great unwashed), actually miss the point totally.
So, as regards Essex, it's NOT the equations that matter, but understanding the relevant physics and maths (such as the difference between extensive and intensive thermodynamic variables), AND understanding enough to know whether they are relevant (or not) to the actual way that temperatures are used.
If we have noisy data (such as we do for temperatures), when trying to extract the common trend, averages are the sensible thing to use (although averages of deviations from the LOCAL mean), when you want to extract that trend from the noise. Complaining that the average so constructed ISN'T a valid thermodynamic variable is totally irrelevant, since no one claimed that it was!
To go back to currants, suppose we had a variety of bushes, some bigger than others, some in patches of more fertile soil, so that the numbers of currants per bush was not directly comparable. This bush might produce 200, compared to 100 from the bush over there, just because the first bush is a lot bigger!
What we're saying, in effect, is that Delhi is warmer than Spitzbergen.............
For bushes, we'd expect a percentage change to be relevant -- if our magic fertiliser improved yields, we'd get MORE extra berries from a 200-berry sized bush than we would from a 100-size bush. Or perhaps we'd get BIGGER berries, but still 200 or them, rather than just more per se.
So, if bigger, we COULD usefully measure the average berry size from a variety of bushes, and compare with average berry size after new fertilizer had been used. If we thought berry count would increase, we'd use proptional increase in number of berries per bush. And in real world situations, we would expect perhaps BOTH total number and size of berries to improve..................
Which makes berries MORE complicated than temperature!
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Post by marchesarosa on Oct 22, 2011 13:48:58 GMT 1
A group at Berkeley (Berkeley Earth Surface Temperature - BEST) led by Prof Richard Muller, have done another run through of the same old land surface station temperature data that some of us believe is fubar . The surprise conclusion is that the world has warmed a bit since the Little Ice-Age, but, as David Whitehouse comments, "The researchers find a strong correlation between North Atlantic temperature cycles lasting decades, and the global land surface temperature. They admit that the influence in recent decades of oceanic temperature cycles has been unappreciated and may explain most, if not all, of the global warming that has taken place, stating the possibility that the “human component of global warming may be somewhat overestimated.”That last statement comes in the penultimate paragraph of one of the BEST papers here, www.berkeleyearth.org/Resources/Berkeley_Earth_Decadal_Variations“ IF the long-term AMO changes have been driven by greenhouse gases then the AMO region may serve as a positive feedback that amplifies the effect of greenhouse gas forcing over land. On the other hand some of the long-term change in the AMO could be driven by natural variability, e.g. fluctuations in thermohaline flow. In that case the human component of global warming may be somewhat overestimated.”How could Richard Black and the alarmists at the Beeb plus myriad other alarmist journalists have missed that while proudly trumpeting "global warming" (meaning AGW) is "real"? I guess they never read to the end of a paper, if, indeed, they read beyond the press release headline. They probably don't get the difference between the land surface and the total surface of the globe, either. (See Frank Lansner's analysis linked to below) The questions about "global" warming remain, how much and due to what cause?
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Post by nickrr on Oct 22, 2011 16:24:52 GMT 1
Because this statement was not a conclusion of the report. The report gave three possibilities for the AMO (taken from one of the comments in the WUWT link below): 1. Greenhouse gases independently cause AMO alterations and land-based warming. 2. Greenhouse gases alter AMO and this drives land-based warming. 3. Alterations in the thermohaline circulatory flow drive AMO alterations,thereby driving land-based warming. The comment that may apply if the third option is true (in the opinion of the authors). However they don't present any evidence that it is true. It is therefore not a conclusion of the paper and therefore should not be reported as such. I note that WUWT reports this comment without any of these necessary qualifications and reports it as if it's a conclusion of the report. Typical of their dishonest and misleading reporting. wattsupwiththat.com/2011/10/21/sceptical-berkeley-scientists-say-human-component-of-global-warming-may-be-somewhat-overstatedOn the other hand the report confirms what many of us already know - global warming is happening. Unlike the stuff about the AMO, this is a conclusion of the report and should be reported as such. This of course also exonerates the scientists involved in the so-called 'climategate' affair of the accusation of data fixing. Incidentally, I note that the report also fails to find any UHI effect - something you've been banging on about for some time. No surpirse that sceptics are clutching at such miserable straws as this stuff about the AMO.
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Post by marchesarosa on Oct 22, 2011 19:01:33 GMT 1
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Post by marchesarosa on Oct 22, 2011 19:04:37 GMT 1
"this statement was not a conclusion of the report". Nice try, nick.
In the penultimate paragraph of the paper, sure looks to me like an important statement of an alternative explanation of the data. "Fluctuations in the thermohaline flow", who'da thunk it?
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Post by marchesarosa on Oct 22, 2011 19:35:08 GMT 1
Discussion of the BEST papers here, too, on Judith Curry's blog. Excellent! judithcurry.com/2011/10/20/berkeley-surface-temperatures-released/#commentsAs for the death of the Urban Heat Island Effect, reports of its demise may have been somewhat exaggerated, nick! Read Judith Curry's blog for the arguments IF (as they say) you are genuinely interested in informing yourself about the ongoing debate.
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