A global temperature

Eli’s post about some of Ross McKitrick’s blunders reminded me that I was involved in a discussion elsewhere when someone highlighted another of his papers called Does a global temperature exist? (with Christopher Essex and Bjarne Andresen). It’s rather old, and Eli’s already covered it, so I won’t say much more about it. Essentially they consider various ways of averaging temperature and conclude that

There is no global temperature.

What I thought I would do is make a slightly different point. In the physical/natural sciences, numbers are used to represent something. In the case of temperature, it’s the average energy per particle. How you manipulate those numbers then depends on what you want to do. If you simply wanted to know the average temperature, you might simply add up the temperatures and divide by the number of measurements. You might, however, need to weight the average if the measurements aren’t all associated with the same volume. If the specific heat capacity has a strong temperature dependence, you might want – instead – to determine the total energy associated with the measurements and then compute the temperature from that. On the other hand, if one was interested in the greenhouse effect, or energy balance, one might define the average temperature as the temperature of a blackbody that has the same flux as the average surface flux on the Earth.

As long as you understand the properties of the system, or know what it is you want to do, you can work out how best to manipulate the numbers. If, however, what you get seems very odd, you might want to check that you haven’t made some kind of blunder, like using Celsius instead of Kelvin (see Eli’s post). I guess the point that I’m getting at is that simply knowing how to manipulate numbers isn’t sufficient if you don’t understand what the numbers represent or don’t have some sense of why you would want to manipulate the numbers in the first place.

Of course, there’s nothing wrong with trying things and getting them wrong. However, typically you would want to learn from your mistakes. It appears that not only does Ross McKitrick not learn from his mistakes, he doesn’t even want them pointed out to others, which seems to rather go against the scientific method. That Ross McKitrick doesn’t take well to criticism also seems reasonably well known. This review of his book Taken by Storm, also with Christopher Essex, starts the concluding paragraph with:

One hesitates to comment on these authors, given their one-size-fits-all reaction to those who disagree: all are simply dupes of the doctrine. But I cannot remember a book that combines so thoroughly tendentiousness with pretensions of objectivity.

Bear in mind that the above refers to the current Chairman of the Global Warming Policy Foundation’s Academic Advisory Council (Essex), and his immediate predecessor (McKitrick). That might explain the Global Warming Policy Foundation’s regular blunders, but I suspect that that is more a feature than a bug.