It remains difficult with the weather or climate and the reference periods.
The German DWD weather service, for example, still finds it difficult to work with the new period 1991-2020 reference and simply cannot say good bye the old 1961-1990 period. Looking back at May 2022, both were used again. According to the DWD, May 2022 was too dry and too warm in Germany. Compared to the currently valid period by 1.3 degrees. Why in the press release the no longer relevant (1961-1990 period gets taken first remains a mystery. It is said that there are people who still calculate in deutschmarks, and not the euro, which was introduced 20 years ago.
Excerpt from the DWD press release:
At 14.4 degrees Celsius (°C), the average temperature in May 2022 was 2.3 degrees above the value of the internationally valid reference period 1961 to 1990. Compared to the current and warmer period 1991 to 2020, the positive deviation was 1.3 degrees. At the beginning of the month, the thermometer dropped partly into the light frost range under the influence of high pressure, often clear skies and the associated nighttime radiation in the north as well as in the south of Germany. Faßberg in the Lüneburg Heath recorded the lowest value in Germany on the 4th with -2.5 °C.
The ‘Ice Saints’ didn’t make it, not appearing this year. To the contrary, high “Wolf” and its successor “Xenophon” brought us early summerlike temperatures of almost 30°C in the second decade of the month. The influx of subtropical air masses from North Africa further increased the heat, especially in the south. Locally, there were record temperatures for May. Ohlsbach, northeast of Freiburg im Breisgau, recorded the highest temperature in Germany on the 20th with 33.7°C. Here, 13 people died in the month of May and 13 summer days (>25°C) and four hot days (>30°C) were recorded in the month. However, the midsummer intermezzo was short-lived, as a northwesterly flow subsequently brought cooler temperatures.”
[…] Germany’s DWD National Weather Service Just Can’t Say Good Bye To Old, Cooler 1961-1990 Referenc… […]
If the Arctic can be regarded as a ‘litmus test’ for climate change as often claimed, the temperature trends of the past century seen there show that the WMO supposedly ‘normal period’ (1961 – 1990) was clearly abnormal:
http://www.climate4you.com/images/70-90N MonthlyAnomaly Since1920.gif
Try again, not the latest to Dec 2021 that shows a slight decline:
https://pbs.twimg.com/media/EEh9f6vUYAARy4o.jpg
I prefer keeping the same reference period so over the decades we can compare the headlines & reports. It’s much harder to keep track of how much they said each decade was warmer if they keep recalculating the series each time a new reference period is created. Claims of warmer temperatures yet we also hear of unwanted low temperatures as well. Changes to land use & expanding urbanization can easily bias the recent data vs old.
Chopping down old forests to install wind turbines won’t be all good for the environment.
Using a reference period is just silly. It shows how little climate scientists know about analyzing time series data. The first step is to de-seasonalize the data. With monthly data, you take the 12th difference. Yes, you lose the first year of data. But going forward, you don’t have to deal with the arbitrary 30 year reference window.