What’s wrong here? August in Germany is not getting warmer

Written by Josef Kowatsch and Sebastian Lüning (Translated/edited by P Gosselin)

According to the German DWD national weather service August 2016 recorded a mean temperature of 17.7°C. The start of the month was really cool, but the last part of the month the temperature climbed to peak summer levels, and thus compensated for the otherwise sub-par summer. No record temperature was set, with the month’s high some degrees below the record of over 40°C set for a few minutes in 2015.

Using the station network operated by the DWD, which covers all of Germany, and looking over the long term (Figure 1), we can discern four segments since 1931:

1) It was warm during the Nazi times.
2) After the war, mean temperatures dropped, and cool Augusts persisted until 1975.
3) Beginning in 1975 a rapid rise took place until a new temperature high was reached.
4) Since the peak in 2003, the temperatures for the month of August have dropped again. In total the current temperature level is higher than in 1931.

graph 1

Figure 1: Temperature in Germany for August since 1931. Chart: Kowatsch. Data source: DWD.

To make the trend look more dramatic than it really is, some reporters are using a trick: They like to start the trend at the bottom of a cold period. Many start their chart at 1961 (Figure 2). Clearly this is near the bottom of the 1960s cold period and thus it makes August mean temperatures look as if they are rising rapidly.

August has gotten much warmer over the past 55 years. According to the linear trend line, the mean temperature was near 16°C in 1961, while today we are close to 18°C.

graph 2

Figure 2: Temperature in Germany for August since 1961. Chart: Kowatsch. Data from DWD.

However, Germany’s mean August temperature has stagnated over the past 29 years at a level of 1988. A temperature plateau has been established (Figure 3).

graph 3

Figure 3: Temperature in Germany for August since 1988. Chart: Kowatsch. Data from DWD.

What’s interesting is a look at the last 20 years (Figure 4). The summer month of August has shown a distinct cooling trend over the past 2 decades.

graph 5

Figure 4: Temperature in Germany for August since 1997. Chart: Kowatsch. Data from DWD.

Thus it’s worth keeping these facts in mind whenever the German media blare out headlines of extreme summer heat. Here it pays to maintain a cool head in order to distinguish between emotions and reality.

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