I wrote earlier correcting Ross McKitrick’s false claim that there is no such thing as Global Temperature. Unfortunately McKitrick’s claim has been adopted and spread by people ignorant of basic physics. For example, consider this review of Essex and McKitrick’s book Taken by Storm at (where else?) Tech Central Station, by Paul Georgia. If you look at Georgia’s biographical details, you will see that he has studied political economy and economics and there is no evidence that he ever studied physics and it certainly shows in his review.
Before I examine what Georgia wrote in his review, I’d like to give Wikipedia a plug. I thought I’d have to quote passages from basics physics texts, but Wikipedia has accurate and careful explanations that I can link to.
No Physical Meaning
Essex, who studies the underlying mathematics, physics and computation of complex dynamic processes, raises some very fundamental scientific issues with regard to global warming. Take, for instance, the “average global temperature,” which is the primary statistic offered as evidence of global warming. The problem with this statistic is that it has no physical meaning. Temperature is not a thermodynamic variable that lends itself to statistical analysis, nor does it measure a physical quantity.
If you read the Wikipedia page on temperature you will discover that it does have a physical meaning and also that it is a physical quantity. And that there is the whole field of statistical mechanics based on the application of statistics to temperature. Go figure.
Thermodynamic variables are of two types, says Essex, extensive and intensive. Extensive variables, like energy or mass, occur in amounts. Intensive variables, such as temperature, refer to conditions of a system. A cup of hot coffee, for example, contains an amount of energy and has a temperature. If you add an equal amount of coffee with the same amount of energy and the same temperature to the cup, the amount of energy doubles, but not the temperature. The temperature remains the same. Thus, while you can add up the energy from two separate systems and get total energy, it is physically meaningless to add up the two systems’ temperatures. And dividing that number by two doesn’t give you the average temperature either. Such an exercise results in a statistic that has no physical meaning. Yet that is exactly what occurs when the average global temperature is computed.
So let’s see. We have some coffee at 60 degrees and add an equal amount also at 60 degrees. Georgia tells us that the mixture will have a temperature of 60 degrees. So far so good. And that adding the two temperatures doesn’t give the right answer. Let’s see: 60+60 = 120, which is not the right answer. OK. And that “dividing that number by two doesn’t give you the average temperature either”. Let’s see: 120/2 = 60, which, err, is the right answer. I don’t want to be too harsh here, but I think your average eight year old could figure out that if you add a number to itself and divide by two you get the original number back again. But this was too much for Georgia.
In fact, adding the temperatures and dividing by two also works if you add an equal quantity at a different temperature. the Wikipedia page on intensive variables has the formula if the quantities are different—it’s a weighted mean of the two temperatures.
Moreover, temperature and energy aren’t the same thing. The internal energy of a system can change without changing the temperature and the temperature can change while the internal energy of the system remains the same. In fact, this occurs all the time in the climate because the two variables are fundamentally different classes of thermodynamic variables and there is no physical law that requires that they move together.
Wow. I guess we’ll just have to ditch the entire field of thermodynamics then. In fact, Temperature T and internal energy U are related by the formula
where m is the mass and c the specific heat. It is true that it is possible for internal energy to change without affecting the temperature if there is a phase change, but the atmosphere stays way above the temperature of liquid nitrogen, so this makes almost no difference to temperatures.
The next time somebody informs you that the planet’s “average temperature” has increased, you can rest assured that they have told you exactly nothing.
It’s clear that Georgia does not understand the basic physics of temperature, but he is willing confidently make false claims about temperature. Furthermore, the fact that Tech Central Station published his nonsense demonstrates that the editors there know nothing about physics either, which is a rather sad state of affairs for a site that publishes commentry on scientific matters.