In search of the Hockey Stick – part 1

Let’s go back to the January plot from the previous post. It concisely presents all the January temperature measurements in the NOAA dataset, from 1705 to 2009, in one single image. Here it is again:

January Mean Temperatures again (click to enlarge)

The time is on the X axis, the temperature on the Y axis. The density represents the number of measurements available. We’ll come back to the temperatures later, but let’s have a look at the number of measurements first. That number grows gradually as the world is being explored and developed, from a few isolated readings in the early 18th century to a dense network in the 20th. In 1950 there is a sudden increase, and a plateau develops which lasts until 1990.

And then, out of the blue, a brutal decline sets in.

From 1990 onwards, only as much measurements remain as were available at the end of the 19th century. Worse, the period 2005-2009 is a flashback to 1850 as to data quantity.

What’s happening ? And where is the Hockey Stick ?

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