Spring drought similar to record year 1976
Like in 2018, 2019, and 2020, the Netherlands faces drought again. So far, the precipitation deficit has been increasing at the same rate as in the record year 1976, when the drought was extra harsh in June, July, and August. Whether that will happen again this year remains to be seen, climate researcher Peter Siegmund of meteorological institute KNMI said to NRC. "But if the deficit is already so great in the spring, the maximum deficit in the summer will probably also be high."
The KNMI determines the precipitation deficit - how much more water evaporates than rain falls - every day from April 1 until the end of September. If the deficit rises, the soil dries out, and the groundwater level falls. That can have major consequences, including failed crops, subsiding houses, and weakening dykes. Low water levels can also affect inland shipping.
According to the KNMI, precipitation over the whole year in the Netherlands has actually increased since the 1960s because of climate change. For every degree of global warming, the air can hold 7 percent more water vapor, so there could be more rain. But the extra rainfall is not distributed equally over the seasons. Evaporation has increased throughout the country in all seasons, also because of climate change.
The Netherlands sees more rain in the autumn and winter and slightly more in the summer - increasingly often in downpours. But precipitation decreased in the spring. "We don't really know why that is," Siegmund said to the newspaper. That, combined with increased evaporation, quickly results in drought. "And those are the first months of the growing season."
With further global warming, evaporation will continue to increase, Siegmund said. The picture for precipitation in the spring and summer is less clear. According to the latest climate models, it will increase slightly in Northern Europe and decrease sharply in the Mediterranean. The Netherlands is in between those areas. "Which way we'll roll is not yet clear," Siegmund said.
Currently, the KNMI expects that the months April-September will be drier or a lot drier in the Netherlands. It partly depends on how quickly the world reduces its greenhouse gas emissions. If it happens fast, the drought months may not be as bad. But if it happens too slowly, further global warming could affect the air circulations. The KNMI's weather models show that this could lead to less moist air from the North Sea in the summer, while the easterly wind brings more dry, warm air from the Mediterranean. That would fuel the droughts in the Netherlands.