Summer sunshine surpasses 1976 record: KNMI

According to the KNMI weather institute, the summer sun has shone more this year than in any other summer since measurements began in 1965. The old record of 1976 was broken four days before the end of the meteorological summer.

According to the KNMI, this year's sunny summer "fits in with the trend of increasing solar radiation in the Netherlands since the 1990s." For example, there is an increase of 3 percent in solar radiation per 10 years, which can even reach up to 5 percent in the spring.

The weather institute calculates the national solar radiation on the basis of the average solar radiation measured at the five KNMI stations: De Kooy near Den Helder, Eelde near Groningen, De Bilt, Vlissingen and Maastricht.

The old record of 1976 was an average solar radiation of 229 Watts per square meter. According to the KNMI, the average will be higher this year at approximately 238 Watts per square meter. The average value over the years 1991-2020 is 206 Watts per square meter.

The solar radiation is not evenly distributed over the country. The west coast receives an average of 9 percent more sun in summer than the east of the country.

More sun in spring and summer contributes to the warming of the Netherlands in addition to the global temperature increase, according to the weather institute. It also leads to a precipitation deficit. According to the KNMI, solar radiation is increasing in almost all of Europe. This is partly due to a decrease in cloud cover because of an increasing number of high pressure areas in spring and summer, and partly because the air has become cleaner.

"Based on calculations with climate models, we take into account in the high KNMI climate scenario a normal value of 219 Watts per square meter around 2085, an increase of more than 6 percent compared to the current climate normal," according to the weather institute. "We therefore expect that the current trend of 3 percent per 10 years will level off in the future as we have more cloudy summer weather again. In addition to global warming caused by humans, natural variations in the weather continue to have a major influence on solar radiation, the drought and the temperature in the Netherlands."