tirsdag 10. desember 2019

Old temperatures are adjusted when new temperatures are added

The temperature anomaly (later simply called the temperature) of the last month is added to the older temperatures when the temperature series are updated each month. But in addition to that, for different reasons, older temperatures are often adjusted. In this blog post I will examine the adjustments done on the older temperatures. I will not discuss why the adjustments are done. The examination is done by calculating the differences between the temperatures in the new series and the temperatures in the same series that were released five years ago.

I downloaded the new temperature series in November 2019 1. They have temperatures up to and including October 2019. I downloaded the old temperature series in the end of 2014 and in the beginning of 2015. The old UAH and RSS satellite temperature series for the lower troposphere (TLT) have temperatures up to and including September 2014. The old surface temperature series GISTEMP, NOAA Global, HadCRUT4 and BEST have temperatures up to and including December 2014.

Figure 1: The temperature differences between new and old releases of the same temperature series. The lines show the one year moving averages of the monthly differences.
Figure 1 shows the one year moving averages of the differences between the new and the old monthly temperatures of the same temperature series. All temperatures series were made relative to the 30-years baseline 1979 to 2008 before the differences were calculated. For NOAA Global the differences are almost identical to those of the GISTEMP, and they are therefore not included in the figure.