The Netherlands was almost 3% sunnier during the coronavirus crisis

The amount of solar radiation that reached the Earth’s surface increased during the period when measures to limit the spread of coronavirus were in place. Researchers Pier Siebesma and Marieke Dirksen (KNMI/TU Delft) came to that conclusion. Between March 15 and June 15 radiation intensity was up 2.5 percent compared to the average value measured during the same period over the last four years.

The relationship between solar radiation, air pollution and cloud formation is a complex one. Changing cloud formation can also affect incoming radiation and skew the outcome of the investigation. That is why only data were used that had been gathered during daylight hours when skies were clear.

Less air pollution
The measures also led to a fall in pollution levels over the Netherlands. Air traffic came to a practical standstill while road traffic was halved. Industrial activity was also wound down. The emissions from planes, cars and factories is a source of aerosols, particles which block solar radiation.

Long-term solar radiation trends, typically covering a period of over ten years, are mainly ascribed to clouds and aerosols (fine particles in the air). About 80 percent of aerosols are emitted by people. Sea salt and Sahara desert dust (which coloured the sun read some years ago) are among the natural sources of aerosols.