This week, we will be suffering from very cold polar air with temperatures well below zero as a result. However, it remains to be seen whether we will have to deal with a true cold wave, as climate change has reduced the probability of a cold wave to once every 12 years. Climate scientists from research organisation VITO have estimated this based on data from the European Commission's Copernicus Climate Change platform.

Mol, 8 February 2021 - We speak of a cold wave if there are 5 consecutive ice days. These are days on which the maximum temperature remains below freezing point. In addition, three nights have to be freezing cold, with temperatures not rising above -10 degrees. In the past, cold waves occurred regularly: about once every 6 years. Due to global warming, the probability is now twice as low: once every 12 years. The last cold spell dates back to 2012.

Cold waves have a major impact on our society, such as the traffic chaos they cause and cold stress. Exposure to extreme cold can cause hypothermia and indirectly increase the risk of cardiovascular disease or respiratory infections. In this respect, the reduced risk of cold waves is one of the few positive aspects of human-induced climate disruption. The key question is whether this positive effect can outweigh the strong advance of heat waves, where the link with mortality is much more obvious. The reduced chance of cold waves also has a negative side for nature: plants and animals in our regions are adapted to cold winter temperatures. Subsequent growth stages, such as flower setting in plants, only occur optimally if the plants have experienced a cold period. The cold waves are also good for stopping the advance of invasive species. Due to global warming, these species thrive in more northerly regions and pose a threat to the indigenous species. But they are often unable to withstand very low temperatures that do not occur in their original habitats. Finally, cold waves also mean that lakes and rivers freeze. If there are fewer cold waves in the future, the chances of enjoying snow and ice will also decrease. For our northern neighbours, this means a direct threat to the famous Eleven Cities Tour (Elfstedentocht in Dutch).

By 2050, the chance will have dropped to once every 20 years and by the end of the century to once every quarter of a century. Moreover, cold waves will become shorter and shorter: they will last on average two days less. Whereas now there are nine, that will drop to seven days. These changes are impressive, but rather optimistic because they are based on a moderate scenario (RCP4.5; representative concentration pathway 4.5) of the IPCC (United Nations Intergovernmental Panel on Climate Change). In a pessimistic climate scenario (RCP8.5), cold waves become virtually unthinkable: only twice a century or only every 50 years. In that case, natural ice-skating rinks will most likely only appear in our history books.

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