What are the consequences of the warm winter?

Record temperatures on New Year’s Eve: What are the consequences of the warm winter?

At the turn of the year, t-shirt weather prevailed in many parts of Germany. There was already talk of a “heat wave” in winter. But is December really that unusual this year – and what do warm phases in winter mean for nature?

The last days of the past year created a spring mood. Lightly dressed, you could enjoy the sunshine in many parts of Germany. Even if this may seem pleasant at first: record temperatures in December are a sign of climate change. A meteorologist and an environmentalist explain what makes the current winter special and what the effects are on the flora and fauna.

Looking only at the average temperature, December was quite balanced. But only because both fairly low and very high extremes are included in the calculation. The Christmas month was characterized by an “icy Advent season, very mild Christmas and record temperatures at the turn of the year”, as summarized by an evaluation by the German Weather Service (DWD). According to the DWD, the “first much too cold and then sometimes record warm weather” led to an average temperature of around 1.8 degrees Celsius in December. The month was about one degree above the value of the internationally valid reference period from 1961 to 1990 and exactly in the middle of the current and warmer comparison period from 1991 to 2020.

Overall, the DWD therefore only rated December as “a bit too warm” with “rather balanced amounts of precipitation and sunshine”. “So far we’ve had a normal to a little too mild winter,” confirms Andreas Friedrich, meteorologist and press spokesman for the DWD, when asked by the editorial network Germany (RND). There was also a cold snap. However, the previous cold days were overcompensated by the high temperatures towards the end of the year.

Consequence of climate change – but not a “heat wave”

In many places the temperatures on New Year’s Eve breaking records. In Munich and three other cities, 20 degrees Celsius and more were measured. Even if the DWD only calculates the national average temperature monthly and not per day, one can assume that it is probably the warmest New Year’s day in Germany since records began, says Friedrich. The reason for the unusual New Year’s Eve weather is climate change.

“Without the warming of the climate, there would not have been such temperatures at the turn of the year,” says Friedrich. The concept of a heat wave, which is now sometimes used, is not correct. Experts from the DWD do not use terms such as heat or heat wave relative to the season – but only for high summer temperatures. At twenty degrees in winter, one simply speaks of “extremely mild weather,” says Friedrich. Particularly mild temperatures in winter are said to be temperatures of around ten degrees and more.

How the rest of the winter will go cannot yet be said with certainty. “We can only look seven to ten days into the future,” says the meteorologist. Forecasts that go beyond that are less accurate. “In any case, no return to permafrost is to be expected by mid-January,” says Friedrich. “In principle, the mild weather conditions like before Christmas remain.” The heat is still being caused by westerly air currents from the Atlantic. There has been a lot of wind lately.

It is likely that the average winter will be similar to the last ones: the bottom line is that the temperatures are too high and there is more rain than snow. And despite the fluctuations, without huge deviations in the average temperature from recent statistics.

Animals wake up from hibernation

Above all, however, it is temperature fluctuations that can have a negative effect on animals and sometimes also plants, says Silvia Teich, press spokeswoman for the German Nature Conservation Union (NABU). And especially for the hibernators. In Germany, these include hedgehogs, squirrels, or “sleeping mice” such as the dormouse. You can currently see hedgehogs running around, says Teich. Because the warm temperatures let the animals wake up from their winter sheep. Insects that keep a kind of hibernation would also wake up. “Bees become active at eight to ten degrees,” says Teich. “But you can find food even now. Christmas roses and snowdrops are in bloom right now, and hazelnuts will be coming soon.”

If it stays with a single warm period, all of this is not a problem. Because as soon as the cold temperatures return, hibernation or hibernation can continue. “Healthy wild animals then simply go back to sleep,” says Teich. The bees then returned to their hive.

However, constant ups and downs in temperatures are worrying if this interrupts hibernation several times. “That costs the animals a lot of energy, so their reserves are more likely to be used up,” says Teich. In the case of plants, shoots and buds that were formed during warm winter days can freeze to death if the cold snaps again. “It’s not so bad for wild plants, they usually sprout again later,” says Teich. However, there could be a risk of crop losses for fruit growers.

Migratory birds change their behavior

In addition to the unstable temperatures, it is also problematic that the winters are getting warmer overall. This has already changed the behavior of many migratory birds. The so-called “short-distance migrants”, which overwinter at a medium distance from Germany, returned earlier from the south and then began to breed earlier. When the cuckoo, a so-called “long-distance migrant”, returns from its more distant winter quarters south of the Sahara, it is too late for it to cheat its eggs into their nests. The chicks of the reed warblers, in whose nests the cuckoo likes to lay its eggs, may have already hatched. A clear disadvantage for the cuckoo, who, as Teich puts it, “doesn’t have it easy anyway”.

In view of the mild temperatures in winter, some birds are already becoming “migratory laziness”: some of them no longer leave Germany at all in winter. “We are told of storks and cranes that no longer migrate south at all,” says Teich. What long-term consequences this will have for these birds or other animals in the ecosystem cannot yet be foreseen, says Teich. “With ever-increasing temperatures, massive effects on wildlife and nature are to be expected in any case, which we cannot yet foresee.”