Can't wait for spring? If you live in a northern region of the planet, you may see it arrive a few days early. And, according to researchers in the US, this phenomenon could continue each decade for many years to come.
It's already known that higher temperatures related to climate change are accelerating the arrival of spring in some parts of the world. But this new study, published in Nature Climate Change, shows that a fall in the number of rainy days each year also has an important role to play.
According to the researchers' calculations, decreasing precipitation frequency in late winter and early spring could cause trees to bloom one to two days earlier each decade than previous scientific estimates, through to the year 2100.
This phenomenon is explained by the associated increase in solar radiation that stimulates leaf growth. The lack of rain also means higher temperatures during the day, but cooler temperatures at night when there are no clouds to trap heat. In other words, plants and trees receive enough light and moisture for optimal growth.
"This contrasting effect earlier in the year makes the plants think it is spring and start leaf onset earlier and earlier," explains study co-author Jian Wang, a doctoral student in geography at The Ohio State University (USA).
To reach these conclusions, the study authors gathered a dataset from the United States, Europe and China. The researchers compiled dates for the first appearance of leaves and analyzed satellite images taken from 1982 to 2018 to determine the time of year when vegetation began to turn green. Finally, this information was compared with the number of monthly rainy days for each of the areas studied.
The results showed that, as the number of rainy days decreases over the years, spring is likely to arrive earlier and earlier for most areas of the planet located in the Northern Hemisphere. The only exception is grasslands located (mostly) in semi-arid regions, where the decrease in the number of rainy days is likely to slightly delay the arrival of spring.
Other climatic phenomena related to human activities can contribute to speeding up the arrival of spring. This is particularly the case for light pollution, according to another American study, published in November 2021 in the Science journal.
