[ducleonctor]

There is something peculiar on the map in the article that caught my eye:

The formerly split country of Germany is also sharply split on the map! The western part (BRD/FRG) has significantly more hot humid days than the eastern part (former DDR/GDR). The colored area edge almost exactly matches the border.

A political map of FRG/GDR for comparison: https://www.stepmap.de/karte/brd-ddr-ddIwvxHotF

Why does this data follow political borders so sharply in this case? Is that effect real or caused by methology error or skewed data?

Apparently the basic data stems from the HadISD database: https://www.metoffice.gov.uk/hadobs/hadisd/v311_2020f/index....

This file lists the stations (version v311_2020f) in the database: https://www.metoffice.gov.uk/hadobs/hadisd/v311_2020f/files/...

Many stations in the former GDR seem to be present, for example:

  104880-99999 DRESDEN 51.133   13.767   230.1 1931-01-01 2020-02-06
  094690-99999 LEIPZIG/SCHKEUDITZ& 51.417   12.233   142.0 1975-07-01 1991-10-31

If the effect is real: Which difference between FRG and former GDR areas causes it?

[ianferrel]

One possibility: Western Germany is more industrialized and urban, with higher population and population density. Thermal measurements in the west are more likely to be taken in urban heat islands?

[ducleonctor]

Industry seems to explain some of that effect. Population density doesn't explain it completely, either:

https://en.wikipedia.org/wiki/Demographics_of_Germany#/media...

Other parts of West Germany also sport lower population density (Lower Saxony in the North, Bavaria in the South).

It is absolutely astonishing how strongly human behavior (industry and metropolitan areas) influences local environmental conditions. I guess most cities may (be forced to) change radically.