Study shows increase in UV radiation in Central Europe

In recent decades, there has been an unexpectedly strong increase in UV radiation in parts of Central Europe. Between 1997 and 2022, researchers in the region around Dortmund recorded an increase of well over 10% in monthly UV radiation. They also observed a similar trend in the Brussels area of Belgium, where radiation increased by almost 20% over the same period.

Measurement of UV radiation on the ground Source: BfS/ Sebastian Lorenz

Scientists from the Federal Office for Radiation Protection (BfS) have now published these results in the journal "Photochemical & Photobiological Sciences". The study was carried out in collaboration with researchers from the Federal Institute for Occupational Safety and Health (BAuA) and the Royal Meteorological Institute (RMI) in Belgium.

The authors believe that the observed increase in UV radiation on the ground is principally due to the decrease in cloud cover in Central Europe. This change, which can also be caused by climate change, leads to greater sunshine hours – and therefore to more time in which the sun's UV radiation can reach the earth.

Evaluation of measurement data from three decades

For the study, the BfS team analysed UV data from a measurement station in Dortmund, where data has been collected as part of the German UV measuring network since 1997. In these measurements for scientific purposes, the UV measuring network uses devices known as spectroradiometers, which gather high-resolution data from the UV spectrum. The authors evaluated over a million of these measurements.

Spectroradiometers measure ozone and UV radiation in Uccle, near Brussels, Belgium Source: RMI

Against the backdrop of the small number of scientific predictions that have been made of the change in UV radiation in Europe so far, the authors had assumed that the data would show – at most – a moderate increase in UV radiation since 1997. The measured values are above the expected levels. To bolster their findings, they also used the same method to study data from a comparable UV measuring station at the same latitude. The station in the Belgian municipality of Uccle, near Brussels, has been providing high-resolution data on UV radiation since 1991. Here, the increasing trend that the researchers observed was even more pronounced. In the authors' view, the results for the two stations show that the trend is not merely local but affects parts of Central Europe in a similar way. At the same time, there is a need for further measurements and evaluations at the national and international level in order to further investigate the change in ground-level UV radiation and its influencing factors and to derive protective measures.

With a view to identifying possible causes of the observed change in UV radiation, the study also included data from other institutions for the entire period – for example in relation to daily ozone layer thickness, global radiation and sunshine hours.

The study also shows the influence of ozone concentration on solar UV radiation, especially in the summer months. Ozone in the atmosphere means that only part of the sun's UV radiation reaches the earth. A reduction in the ozone concentration in the atmosphere – e.g. due to halogenated substances – leads to an increase in the proportion of UV radiation.

Information about UV radiation is becoming increasingly important in everyday life

UV radiation from the sun is a risk to human health, as it can damage the skin and eyes and cause cancer. The intensity of UV radiation on earth, and therefore the risk to humans, depends on many factors, including geographical conditions such as latitude or altitude above sea level on the one hand and changing influences such as cloud cover or the ozone layer on the other. Due to the complex interrelationships, there have so far been few studies with meaningful long-term measurement series that show whether and how UV radiation on earth changes over a longer period of time.

President of the Federal Office for Radiation Protection, Dr Inge Paulini

"The results show that personal exposure to UV radiation may increase for the population in Germany. From a radiation protection perspective, they also show that information on UV radiation is becoming increasingly important in everyday life", says Inge Paulini, President of the BfS. "There are simple ways of protecting yourself and others from UV radiation, and information about current levels of such radiation can help people to do so. The German UV measuring network plays an important part in these efforts."

The around 40 probes in the measuring network provide measurement data from sunrise to sunset. This data is published as a UV index in the form of a daily maximum value and a daily graph on the BfS website, for example, as well as in numerous weather apps.