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Average Global Temperature Is Impossible


Discussions on global warming often refer to 'global temperature.' Yet the concept is thermodynamically as well as mathematically an impossibility, says Bjarne Andresen, a professor at The Niels Bohr Institute, University of Copenhagen, who has analyzed this topic in collaboration with professors Christopher Essex from University of Western Ontario and Ross McKitrick from University of Guelph, Canada. It is generally assumed that the atmosphere and the oceans have grown warmer during the recent 50 years. The reason for this point of view is an upward trend in the curve of measurements of the so-called 'global temperature'. This is the temperature obtained by collecting measurements of air temperatures at a large number of measuring stations around the Globe, weighing them according to the area they represent, and then calculating the yearly average according to the usual method of adding all values and dividing by the number of points. "It is impossible to talk about a single temperature for something as complicated as the climate of Earth", Bjarne Andresen says, an an expert of thermodynamics. "A temperature can be defined only for a homogeneous system. Furthermore, the climate is not governed by a single temperature. Rather, differences of temperatures drive the processes and create the storms, sea currents, thunder, etc. which make up the climate".He explains that while it is possible to treat temperature statistically locally, it is meaningless to talk about a a global temperature for Earth. The Globe consists of a huge number of components which one cannot just add up and average. That would correspond to calculating the average phone number in the phone book. That is meaningless. Or talking about economics, it does make sense to compare the currency exchange rate of two countries, whereas there is no point in talking about an average 'global exchange rate'.If temperature decreases at one point and it increases at another, the average will remain the same as before, but it will give rise to an entirely different thermodynamics and thus a different climate. If, for example, it is 10 degrees at one point and 40 degrees at another, the average is 25 degrees. But if instead there is 25 degrees both places, the average is still 25 degrees. These two cases would give rise to two entirely different types of climate, because in the former case one would have pressure differences and strong winds, while in the latter there would be no wind.A further problem with the extensive use of 'the global temperature' is that there are many ways of calculating average temperatures.Example 1: Take two equally large glasses of water. The water in one glass is 0 degrees, in the other it is 100 degrees. Adding these two numbers and dividing by two yields an average temperature of 50 degrees. That is called the arithmetic average.Example 2: Take the same two glasses of water at 0 degrees and 100 degrees, respectively. Now multiply those two numbers and take the square root, and you will arrive at an average temperature of 46 degrees. This is called the geometric average. (The calculation is done in degrees Kelvin which are then converted back to degrees Celsius.)The difference of 4 degrees is the energy which drives all the thermodynamic processes which create storms, thunder, sea currents, etc.These are but two examples of ways to calculate averages. They are all equally correct, but one needs a solid physical reason to choose one above another. Depending on the averaging method used, the same set of measured data can simultaneously show an upward trend and a downward trend in average temperature. Thus claims of disaster may be a consequence of which averaging method has been used, the researchers point out.What Bjarne Andresen and his coworkers emphasize is that physical arguments are needed to decide whether one averaging method or another is needed to calculate an average which is relevant to describe the state of Earth.Reference: C. Essex, R. McKitrick, B. Andresen: Does a Global Temperature Exist?; J. Non-Equil. Thermod. vol. 32, p. 1-27 (2007).


Alia Ahmed 6 years, 10 months ago

I think it is interesting that this writer tries to prove that science is nothing but another religion by quoting scientists' findings that supports his/her positions.

Paul Decelles 6 years, 10 months ago

There is a good discussion about the article in the blog realclimate at: have read the paper in question and the criticism might be valid if the global average temperature were being used as an actual input to some sort of physical model. It is not. As the criticism in Real climate notes:"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). Thus the choice may not need a physical justification, but is part of a scientific test which enables us to get a clearer 'yes' or 'no'. One could choose to look at the global mean sea level instead, which does have a physical meaning because it represents an estimate for the volume of the water in the oceans, but the choice is not crucial as long as the indicator used really responds to the conditions under investigation. And the global mean temperature is indeed a function of the temperature over the whole planetary surface. "So at least some global warming "skeptics" have taken well known properties of averages and led readers to an erroneous conclusion about how these averages fit in to undertstanding global climate!

aginglady 6 years, 10 months ago

"This is the temperature obtained by collecting measurements of air temperatures at a large number of measuring stations around the Globe, weighing them according to the area they represent, and then calculating the yearly average according to the usual method of adding all values and dividing by the number of points."___There is a problem with the systems of temp recording. Everyone doesn't use the same method of taking, recording etc. This group : working to get monitoring done correctly, etc. etc.The link can tell far more than I can do here.Nice photos too.

UncommonSense 5 years, 6 months ago

pdecell, the problem with your argument is that the climate and weather do not function by the "average global temperature"; they function because of the differences in actual temps.

Gonzaga 5 years, 4 months ago

If a thing exists it exists in some amount, hence can be measured (Thorndike?)

Temperatures can be observed and reported in scattered sites globally. It those sites are "globally representative" of the population of locally representative sites, observed values of site-average temperatures (e.g., daily high + low / 2) may be collected and averaged arithmetically. The resulting value would be, by definition, the current "average global temperature"; and if calculated daily/monthly/yearly would permit assessment of trends in the average of local averages aka average global temperature. Theoretically, given normal contrasts in hemispheric seasonal patterns, there should be no statistically significant change in the global average unless something causes changes in hemispheric patterns (higher lows in winters, higher highs in summers, for example).

In any event everybody talks about "average global temperature", and one must assume it's a value that can be calculated and, to some extent, interpreted. But it's a value that seems never to be cited in discussions of the relationship between "global warming aka rise in average global temperature" and climate change.

Please enlighten us..

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