Climate shift: those long hot French summers from the 1970s can now be found in the Netherlands

They were often small, second-hand Beetles or Dafjes that were stuck in traffic jams at the border in the summer months. Fully loaded to the rafters, sometimes large packs of luggage on the roof. They were by no means safe. The cars were bought especially for vacation and should not cost too much. There was often a lot of things wrong with it. But still they were on their way to the Côte d’Azur, heading for the adventure, the glamor of the French coast, and of course the beautiful weather.

Where the Dutch migrated southwards en masse in the 1970s, it has traveled the other way again. The current Dutch summer has increasingly resembled the French summer of yesteryear. In De Bilt, which is fairly representative for the Netherlands, the average temperature of a 24-hour period between 2010 and 2019 – so measured from 0:00 to 24:00 – was 17.6 degrees. This corresponds, according to research by NRCwith the temperature in large parts of central France in the 1970s.

Used for the analysis NRC data from Copernicus, the EU’s Earth Observation Programme. That divides the continent of Europe into sections of about 30 by 30 kilometers. For each cell, the Copernicus program calculates, among other things, the average temperature and the amount of precipitation in 24 hours. These data are available for the period from 1950 to last year.

NRC calculated the average temperature and precipitation for the area around De Bilt for the summer months between 2010 and 2019. These were compared with all sections of Europe in the 1970s: in which areas was the weather most similar to that in De Bilt in the 1970s? In recent years? How did the summer weather shift due to climate change?

This week was an example of that change. Those who had to go outside in the Netherlands, especially on Tuesday, sought shade, from bathers who lowered themselves into the water next to the Scheveningen pier, to the painter who took a parasol into the aerial platform. In De Bilt, temperatures above 35 degrees were measured; since the beginning of the measurements in 1901, this has only happened nine times before. The chance of such warm days increases due to climate change, says KNMI climate researcher Peter Siegmund. That is not only a result of direct warming by greenhouse gases, he says. “In the summer there is also an increase in the amount of solar radiation in the Netherlands, because it is less often cloudy. This also increases the temperature.”

Cooling off in the fountain

It is not the case that the 1970s did not have warm summers. Who it digital archive searches by the Netherlands Institute for Sound and Vision, quickly finds the images of crowded beaches, of campsites where the tents and caravans, according to the Polygoon news, were “hut by the hood”, of “city youth” who sought refreshment in ponds and fountains. At times it was so hot that “the elderly did not hesitate” to plunge into the fountain. “One thing is certain,” it said on the Polygoon news, “the summer of 1975 will go down in history as one of the warmest since climatic observations began in De Bilt.”

But the weather wasn’t always that good. The Dutch may have become accustomed to warm summers by now, but climate researcher Siegmund – himself a student in the 1970s – says he mainly remembers “rainy youth holidays”. “We always went on holiday in the Netherlands, to Zeeland, or Bergen aan Zee. Always rain.”

At 16.3 degrees, the average daytime temperature in the Netherlands in the 1970s was indeed 1.3 degrees Celsius lower than in the decade of this century. But it actually started to rain more in the summer months: from an average of 1.9 millimeters daily then to 2.7 millimeters in the tens.

Anyway, you can’t just say that the Dutch summers are ‘so’ wetter now, says Siegmund of the KNMI. Yes, on average there are more millimeters. But: it does not necessarily rain more often, the intensity of the showers has mainly increased. “That’s because it’s gotten warmer. Warm air holds more water vapor.” The result: more downpours, fewer drizzly days.

Travel South

The summer temperature in the Netherlands has therefore risen by more than one degree in those fifty years. You could also say: the heat has traveled five hundred kilometers to the north. And that didn’t just happen in the Netherlands. Temperatures have moved north across Europe. In central France – which in the 1970s resembled the present-day Netherlands – summers are now roughly as warm as in northern Spain in the 1970s, which in turn got the temperature of southern Spain.

When it rains, it’s more complicated. Changes can also be seen there, but they do not all go in one wind direction. Particularly around the North Sea, there is more rainfall – from Brittany to Norway, and also in the Netherlands. Further inland it has become drier, while it remains wet for a while around mountain ranges. Not surprising, says Peter Siegmund of the KNMI. “The wind knocks air with water vapor against the mountains, pushing it upwards. Higher in the air, the water vapor cools, and then it starts to rain.”

The KNMI expects that the Netherlands will become even warmer in the coming decades: in thirty years’ time the country will resemble the France of today. Summers are slowly becoming drier – although it rains a bit more, the heat evaporates even more moisture. “When the soil dries out, it absorbs more heat. If a heat wave comes over it, it means even higher temperatures than with less parched ground,” says Siegmund. This also happened in France, where it warms up faster than in the wetter Netherlands. In 2050, the climate in the Netherlands throughout the year – not just in the summer – will be like that of Bordeaux today.

Video: Polygoon-Profilti/Netherlands Institute for Sound and Vision