Heat wave, climate change and Big Data for Lower Franconia

The simultaneity of freedom and captivity – uncertainty from Kafka to today

Long summer nights, swimming in the Main with friends and forgetting about the upcoming exam stress over a beer and good music. That was probably the reality of life for many students in recent weeks, including mine. But sometimes, when I'm sitting amongst the celebrating or chilling people, I notice that I can't really enjoy it all that much. Yet shouldn't I, given the fact that after such a long time of online teaching and lockdowns it's even possible again to do such uncomplicated and yet actually beautiful things? I feel dissatisfaction with myself and my inability to simply enjoy things. At the same time, though, I'm also disappointed that it doesn't seem to bother many others very much. I'm talking about the heat. And the unmistakable state of dryness. In recent days there were two days with new heat records in Würzburg, the 19th and 20th July with 36.7 °C and 37.8 °C daily maximum temperatures respectively. Furthermore, it has rained below average here over the last 30 days with only 16 mm/m² of precipitation.
For comparison: in the reference period 1961–1990, it rained an average of 19 mm/m² more during this timespan. The reference period was established according to international scientific standards as 1961–1990 (sometimes also 1970–1999) because it can be assumed that the effects of anthropogenic, i.e. human-made, climate change on temperatures and precipitation were still significantly lower then than today. In order to make any statement about extreme temperature and precipitation events at all, current weather is — put simply — compared with a reference period of at least 30 years, since daily weather is often subject to the most varied fluctuations and only by means of an average over 30 years can one speak of climate, from which extreme values and trends can be determined. Although heat waves and drought are a global phenomenon of climate change, the region around Würzburg is particularly at risk in comparison with the rest of Germany. An interdisciplinary research group involving the Department of Geography and the Department of Computer Science at Universität Würzburg presented the climate report for Lower Franconia in 2020 as part of the BigData@Geo project. IPCC for here, so to speak. Like the IPCC report, this report contains modelling of meteorological parameters such as temperature and precipitation, which are based on the collection and evaluation of regional data and are linked to specific socio-economic developments. Thus the "more favourable" scenario (rcp45) stands for ecologically more sustainable development including compliance with the Paris Climate Agreement. This stipulates that global warming of 1.5 °C compared to pre-industrial levels must not be exceeded. However, if "business as usual" continues, this scenario becomes unlikely and significantly higher global warming must be assumed. This scenario is referred to as rcp85. For the Lower Franconia region, this means: significantly less precipitation, especially in already rather dry areas such as Franconian wine country, higher average temperatures, longer-lasting and more intense heat waves, and fewer frost days and snowfall. Particularly in cities such as Würzburg, this has an additional component: the increase in the number of tropical nights. These are understood to be nights in which the air temperature does not fall below 20 °C. Due to soil sealing through residential areas, roads, car parks and shops, and the usually low proportions of green and water surfaces, cities heat up significantly more compared to the surrounding countryside and also cool down less and more slowly in the evenings. In Lower Franconia this is a relatively new phenomenon; for the reference period 1970–1999, values of 0–1 tropical nights per year are estimated. Frequent tropical nights pose, in addition to the general burden of heat, a not-to-be-underestimated health risk particularly for older people, pregnant women and small children. Depending on the emissions scenario, 2–3 tropical nights per year are projected for the rcp45 scenario and over 12 for rcp85. Moreover, extreme events also become significantly more likely. Not only with regard to tropical nights, whose number in record years under rcp85 can rise to over 60 per year, but also with regard to temperatures, precipitation and other meteorological parameters overall.

The heat wave of recent days is probably merely a small foretaste of what awaits us and will probably seem relatively normal to us in retrospect in a few decades. Especially in the second half of the 21st century, we will clearly feel the differences in our actions, that is, whether we behave in a more climate-friendly way from now on or not. I don't know whether this vision of the future really helps to be more optimistic, but at least it shows that we still have the possibility to avoid particularly burdensome climatic conditions. Perhaps I should sit down with the others by the Main again until then and raise a toast. And be grateful that today is not yet 2100. 

You can find the whole report here: https://bigdata-at-geo.eu/webklimabericht/Klimabericht.pdf 
And there's also an interactive climate atlas: https://bigdata-at-geo.eu/klimaatlas/