Global Temperature

Just today I taught my statistics students that certain values, if they exist, are fluid--what is the average height of the adult American woman, for example?  Every day women die, others turn 18, others become Americans, etc., so every day that number fluctuates (no doubt somewhere several decimal places beyond the decimal).  It's not a static number.

It never occurred to me to think about a "global temperature", but the authors of this editorial did:

The United Nation’s Intergovernmental Panel on Climate Change is quite certain Earth will be in trouble if the global temperature exceeds pre-industrial levels by 1.5 degrees Celsius or more. But how can anyone know? According to university research, “global temperature” is a meaningless concept.

“Discussions on global warming often refer to ‘global temperature.’ Yet the concept is thermodynamically as well as mathematically an impossibility,” says Science Daily, paraphrasing Bjarne Andresen, a professor at the University of Copenhagen’s Niels Bohr Institute, one of three authors of a paper questioning the “validity of a ‘global temperature'"...

But a “temperature can be defined only for a homogeneous system,” says Andresen. The climate is not regulated by a single temperature. Instead, “differences of temperatures drive the processes and create the storms, sea currents, thunder, etc. which make up the climate”.

While it’s “possible to treat temperature statistically locally,” says Science Daily, “it is meaningless to talk about 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.”

It's not a long editorial, I'd encourage you to read the whole thing.