The Netherlands is experiencing the hottest week ever recorded, and the longest uninterrupted period of temperatures above 30 degrees. While the Netherlands is sweating, climate researchers are puzzling: that heat waves are getting warmer is in line with expectations, but not that things are going so fast.

2018 was exceptionally dry and warm, last year the temperature in the south shot past the 40 degree limit for the first time and we are currently experiencing the hottest week since the start of the measurements - as part of an exceptionally long heat wave.

For example, De Bilt is expected to have the eighth day in a row on Thursday in which the afternoon temperatures do not fall below 30 degrees and locally even regularly exceed 35 degrees.

By way of comparison: for a 'normal heat wave' we need at least five consecutive days with temperatures above 25 degrees in De Bilt, including maximums above 30 degrees on three days.

See also: KNMI: 'Perhaps open door, but the risk of heat waves is increasing'

Dutch heatwaves anticipate global warming

If you add up the heat, it is an exceptional situation, says Geert Jan van Oldenborgh in conversation with NU.nl. He is a climate researcher at KNMI and collaborates internationally on studies that try to determine the exact causes of weather extremes - such as the recent heat in Siberia, or last year's forest fires in Australia.

But it is precisely those heat waves in the Netherlands that are a difficult task for extreme experts, he says. They are rising a lot faster than expected, and that is not yet easy to explain.

"According to climate models, the heat waves should be about 1.5 degrees warmer here now than at the beginning of the twentieth century. But measurements show that the hottest days of the year in the Netherlands are already more than 3 degrees warmer - about twice as fast. So."

In any case, the Netherlands is warming faster than the world average. The average Dutch summer temperature is now about 2.5 degrees higher than in 1900 and the annual temperature about 2 degrees. World average it has become about 1.2 degrees warmer over the same period.

See also: Also in Africa they have heat waves (and you never hear about that)

The 'Spanish Plume' is also getting hotter

Van Oldenborgh says there is a suspicion that one of the causes is the relatively rapid warming of the Mediterranean, which also affects the Dutch summers.

The current heat wave, for example, is a product of the so-called 'Spanish Plume', an elongated high-pressure area that leads to a supply of hot air from Spain to the Netherlands.

"Normally it only lasts a few days, but in this case it turned into a normal high-pressure area above our own country and the high temperatures are maintained by the solar radiation. But all this takes place against an increasingly higher background temperature due to the increased greenhouse effect."

See also: Five days hotter than 35 degrees, not seen since 1901