As a result of climate change, meridional waves that already have unpredictable effects on our weather will further increase in size and will cause more extreme consequences in the winter periods, explains an expert to 24.
In the coming years, our winters will have significantly more periods of extreme weather. Even though winters in general will be “quiet and mild”, they will be more often interrupted by cold blasts. These phenomena, although short in duration, can be expected anytime from September to April.
As meteorologist László Molnár explains, this change, which is further triggered by climate change, in short has to do with differences in temperature between the North Pole and the Equator, and with what are called meridional flows.
Triggered by these differences, a meridional flow is a “vertical wave” that runs along the Earth’s longitudinal circles. When it goes north, it carries hot air from the Equator, and when it goes toward the South, it carries cold air from the North pole.
In winter, when there is a larger difference in temperature between the North Pole and the Equator, these waves have a higher amplitude, triggering more extreme weather conditions.
“Depending on which side of the wave we are standing on, we can either be hit by a polar cold wave or an equatorial heatwave.”
And how does climate change come in the picture? While the North Pole remains cold and dark in the winter, the Earth’s surface on the Equator has a rising temperature due to the greenhouse effect: this causes meridional waves that have more energy and reach an even farther distance.
Molnár explains that our continental climate is also affected by zonal (latitudinal, west-east) flows, but these are not as extreme as the meridional ones, and their effects are rather easy to predict.
Mild winters are in fact the result of climate change, too. As Molnár says, cold waves used to be more intense in the mid-20th century; we will be more likely to encounter unusually hot weather during the winter months.
“We are lucky if there will be a white Christmas every ten years […], and our grandchildren will probably not get to see any big Hungarian lakes.”
He is also convinced that there will be new highs in temperature by 2025, breaking Hungary’s current record of 41.9°C from 2007. The coldest ever measured temperature in the country was -35°C in 1940. Two famously cold settlements are Zabar and Szécsény, although as he explains, their stations are not old enough yet to provide sufficient data for scientific research.
Following a sunny and rather warm period, next week’s weather will be characterised by significant precipitation, with temperatures not reaching higher than 15–17°C. In the morning hours, it can even freeze in some places.