What is climate?

This is a guest post by Professor Richard Lindzen.

We are generally told that the following defines ‘climate’…

Figure 1 Global average temperature anomaly.

Actually, we are not looking at ‘average temperature’. Averaging Mt. Everest and the Dead Sea makes no sense. Instead, we average what is called the temperature anomaly. We average the deviations from a 30-year mean. The figure shows an increase of a bit more than 1°C over 175 years. We are told by international bureaucrats that when this reaches 1.5°C, we are doomed. In all fairness, even the science report of the UN’s IPCC (i.e. the WG1 report) and the US National Assessments never make this claim. The political claims are simply meant to frighten the public into compliance with absurd policies. It remains a puzzle to me why the public should be frightened of a warming that is smaller than the temperature change we normally experience between breakfast and lunch.

My puzzlement becomes clearer when one includes the data points in Figure 1, as shown in Figure 2. This was first noted by Stanley Grotch, and updated by John Christy and I).

Figure 2 Temperature anomalies at individual stations as well as the mean.

We see that the data points are spread pretty densely over a range of about 16°C – over an order of magnitude greater than the range of the mean. The change in Figure 1 looks big simply because the data points are left out and the scale is expanded by over an order of magnitude.

What exactly does this say about climate? In point of fact, the Earth has dozens of different climate regimes. This is shown in Figure 3 showing the Koppen climate classification for the period 1901-2010. Each of these represents different interactions with their environments. Are we really supposed to think that each of these regimes responds in lock-step with the global mean temperature anomaly? On the contrary, Figure 2 tells us that at any given time, there are almost as many stations cooling as are warming.

Figure 3 Koppen climate classification.

Of course, the notion that global average temperature anomaly constitutes ‘climate’ is attractive due to its simplicity.

Unfortunately, that doesn't mean that it is correct.