Researchers
Question Validity Of A 'Global Temperature'
Science Daily
—
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.
Average without meaning
"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.
Many averages
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.
Claims of disaster?
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).
Note: This story has been adapted from a news release issued by