It is already painfully clear that models of anthropogenic global warming are ridiculously inadequate, and do not meet the basic tests of experimental science, no matter how many "scientists" yell "consensus." Now comes a serious question from a serious scientist that threatens to undermine the fundamental premise of the alarmists.
Danish physicist Bjarne Andresen has raised the interesting point that there may be no global warming, because there is no such thing as global temperature! That is because the earth atmosphere is not a homogeneous system. It's not a glass lab jar in your high school physics lab.
"It is impossible to talk about a single temperature for something as complicated as the climate of Earth. 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."(Italics added.)
Andresen is a professor at The Niels Bohr Institute, University of Copenhagen. His article appeared in The Journal of Non-equilibrium Thermodynamics, with coauthors Essex and McKitrick. The journal deals with energy systems that are too complex to come to equilibrium, unlike a cup of hot tea, which behaves in a highly predictable way. A lot of important physical systems, like the climate, appear to be non-equilibrium systems. They are not well understood, which is why they are a hot frontier topic in physics.
Mathematically, there are several different "measures of central tendency," which is what an "average" really is. When we think about "average global temperature" we are usually thinking about the arithmetic mean. But there is also a geometric mean, a mode, a median, and more complicated expressions that can be used as numerical indices for the heat content of a physical system. But as Andresen points out, which of those "averages" you use depends upon your model of the atmosphere.
The current evidence cited for "global warming" could even mean a decrease in the physical heat density of the atmosphere, if a different mathematical average is used. And because the climate is driven by differences in heat between different regions --- leading to the daily weather, as well as hurricanes and snow storms --- the right predictor for global climate may not be an average heat density at all, but rather the regional differences in heat content. Weather systems flow from high to low pressure regions, which are in turn dependent upon complex heat exchange mechanisms.
All the standard arguments for global warming rely upon conventional "equilibrium" models of the atmosphere, all of which may be false.
As Andersen suggests, global warming hype may be more politics than science.
C. Essex, R. McKitrick, B. Andresen: Does a Global Temperature Exist? Journal of Non-Equilibrium Thermodynamics (2007).