Fact check: Has it been this hot before?

2023-09-13 08:09:00

People should “finally” understand what “lies” are being told every day, commented one user in a post that was shared thousands of times.

The Facebook post refers to this newspaper article.
Bild: Screenshot

Assessment: The heat waves in the 20th century do not speak against the existence of the climate crisis. Due to global warming, there are more hot phases. The summers of recent years have been among the hottest ever recorded.

Examination: The article contained in the online articles comes from the German local newspaper “Acher- und Bühler Bote”. As the city history institute of the city of Bühl announced upon request, the contribution by local researcher Adolf Hirth was published in issue no. 176 on August 2, 1995.

The article is about hot periods and “summer of the century” in Germany in the 20th century. 19 years between 1911 and 1976 are mentioned. First of all: If you compare the years with a graphic from the German Weather Service on past temperature anomalies in summer When compared, it turns out that not all summers in the years listed in the article were hotter than average.

The summers of 1911, 1947, 1950, 1959 and 1976 had a high positive temperature anomaly, meaning they were hotter than average. The anomaly in these years was therefore more than one Kelvin (K). The Kelvin temperature unit is often used when specifying temperature differences on the Celsius scale – same here. However, the scale division corresponds to that of the Celsius scale, so it was more than one degree Celsius hotter in these summers than in the comparable period. The reference period is the years 1961 to 1990.

However, the years 1915, 1942, 1949 or around 1961 mentioned in the article were hardly elevated or even had negative anomalies. The summer of 1917, in turn, had a high positive temperature anomaly (above 1 K) and is not reported in the article. All other years mentioned were above average, but the deviation was less than one Kelvin.

Regardless of these substantive discrepancies, the conclusion that the current heat records are “normal” because there have already been heat phases before is wrong. Such weather extremes are related to the climate crisis and cannot be explained without it.

The summers of the last few years alone show this: the graphics from the German Weather Service clearly show that almost all summers since the 2000s have had a high positive anomaly. As of 2020, the three hottest summers in the history of measurements were in the 2000s in both Germany (measurement series since 1881) and Austria (measurement series since 1767).

They are now in Germany has the four hottest summers ever measured in the 21st century, three of which were in the recent past: 2018, 2019 and 2022. Austria even has the seven hottest summers in the 21st century. Six of these occurred in the recent past: 2019, 2015, 2022, 2017, 2018 and 2023 (note each in order of placement).

These climate changes are due to human-caused increases in atmospheric concentrations of greenhouse gases. The lion’s share of this comes from burning fossil fuels. While CO2 emissions rose slowly in the mid-20th century, they began to skyrocket around 1950, graphs on Climate.gov show.

In 2022, the proportion of CO2 in the atmosphere rose to 417.06 ppm (parts per million). Before the start of the Industrial Revolution, CO2 levels were around 280 ppm. One ppm is equal to one molecule of carbon dioxide per million molecules of dry air.

In one Summary of the 2021 IPCC Working Group I Sixth Assessment Report The climate changes of the past decades are simulated using global surface temperatures. It turns out that the currently observed warming can only be depicted if human factors are taken into account in addition to the natural ones. If only natural factors were taken into account – such as the sun or volcanoes – the temperature should hardly have increased in the last 170 years and in some cases should even have decreased.

Overall, according to the IPCC report, the “likely range” of the total increase in global surface temperature by 2019 is 0.8 degrees to 1.3 degrees Celsius (1850-1900 reference frame).In Austria, the summer of 2023 was 2.8 to 2.9 degrees above the average for the climate period 1961-1990, writes GeoSphere Austria on its website.

The number of hot days in Austria in the summer of 2023 was also significantly above the average of the last few decades. A hot day is when the air temperature is above 30 °C. On tropical nights the temperature does not fall below 20 °C. It is very likely that the increase in air temperature will be accompanied by an increase in heat waves, says GeoSphere with reference to the IPCC.