Slippery sidewalks instead of solid snow
The most intense warming is observed in spring and winter, and the slowest in autumn. In Lodz and the Lodz Region, warming has moved us from a zone in which negative-temperature days dominated in winter to one where the temperature is usually positive during the day and drops below zero only at night. Unfortunately, this means that snow cover is now rare. It appears after a heavy snowfall and disappears after a few days. Such situations repeat many times during the season. If the temperature is positive during the day and drops below zero at night, the sidewalks in the morning are covered with ice and are dangerously slippery.
Farmers perceive the phenomena related to climate warming slightly differently than city dwellers. Snow cover protects the ground against excessive cooling and loss of soil moisture. The soil, deprived of snow, is exposed to frost. A few-day period of negative temperatures may lead to a decrease in the yield of winter cereals. The lack of snow cover also means a lack of significant water inflow to the soil during the spring thaw. In the past, it used to be a significant injection of moisture before the growing season. Currently, the deficit of water in the soil often begins at the beginning of spring. A warmer winter also creates more favourable conditions for the survival of pests.
Summer heat waves and tropical nights
Of course, warming is also visible in the summer. The average temperature of the summer months has increased by more than 1.5 degrees C. Many of us enjoy the warmth as long as it is not excessive. Unfortunately, heat waves, i.e. periods with a maximum daily temperature exceeding 30 degrees C, are becoming more and more frequent, longer and more intense. In central Poland, the number of hot days has almost tripled in the last 50 years.
Currently, heat is considered the most dangerous meteorological threat to human life in developed countries. Especially in cities, where high temperatures during the day are accompanied by slightly lower temperatures at night. Nights when the temperature does not fall below 20 degrees C are called tropical nights. In the mid-20th century, they happened very rarely in Poland, once every dozen or so years. Currently, in cities, they are very common during heat waves, preventing the body from regenerating at night. Higher temperature in the summer also means much greater evaporation and often an accompanying drought, water shortage or its low quality.
False spring is transforming agriculture
Warming has resulted in significant shortening of winter (i.e. the period with an average temperature below 0 degrees C) and lengthening of summer (i.e. the period with an average temperature above 15 degrees C). The length of the other seasons has not changed significantly, but pre-winter and spring start (and end) earlier, while autumn and pre-winter start later. This means the extension of the growing season, a very important period for farmers and fruit growers.
Since the mid-20th century, the growing season in the vicinity of Lodz has been extended by almost a month. A longer growing season is conducive to the maturation of plants for which the previous growing season was too short. Maize can be used as an example. Thirty years ago, it was grown solely for fodder because the cobs had no chance to mature. Currently, it is a popular cereal in Poland. While farmers can remedy this problem by postponing the sowing, perennial fruit bushes and trees are at great risk in years when the last frost occurs during the fruit setting period.
More and more often, the so-called false spring occurs – after several weeks of warming and the start of vegetation, winter returns. A wave of frost during the period of flowering or fruit formation brings huge losses in fruit growing, but also in natural ecosystems.
To sum up: inhabitants of Lodz and the Lodz Region are most threatened by the summer heat. The lack of snow cover in winter is a problem for farmers and fruit growers, due to the fact that the soil without an insulating layer is exposed to frost. This may lead to a decrease in the yield of winter cereals and freezing of the roots of perennial plants and fruit trees, as well as water shortage, which is dangerous for everyone.
Adaptive actions should focus on preventing such situations. We cannot forget about the activities leading to the reduction of greenhouse gas emissions into the atmosphere. The climate crisis is primarily a threat to people. The progress of global warming makes our lives harder. It may be even harder in the future. At the moment, actions against climate change are a few sham steps, but in general, they are actually few, and the amount of carbon dioxide in the atmosphere is still increasing.
Text: Prof. Joanna Wibig, Department of Meteorology and Climatology, Faculty of Geographical Sciences, University of Lodz
Edit: Iwona Ptaszek-Zielińska, Communications and PR Centre, University of Lodz