According to a new study led by Eurac Research – a private research center from Bolzano, Italy – global snow cover has been steadily declining over the past four decades. On average, there are 15 fewer days that snow remains on the ground – with peaks of up to 20 or even 30 fewer days in Canada’s western provinces – and snow coverage has decreased by a total of four percent.
This study is a follow-up of an initial analysis of global snow cover published in 2020, which provided evidence that snowfall has declined in 78 percent of mountain areas over the past two decades. By extending the start of data collection to 1982, the author of both studies Claudia Notarnicola, the deputy director of Eurac Research’s Institute for Earth Observation, has shown that “with a few exceptions, data on both the extent and duration of snow cover are clearly decreasing.”
To investigate these trends, Notarnicola took a hybrid approach, combining MODIS satellite data time series from 2000 to 2020 with state-of-the-art mathematical models.
“I chose a highly attested NASA global model as the basis and then refined it. In fact, for the period when the data from the model and the more precise satellite images overlapped, I was able to better calibrate the model thanks to so-called ‘artificial neural networks,’ a computational system that falls under the aegis of artificial intelligence,” explained Notarnicola.
“The analysis of the harmonized time series over 38 years indicates an overall negative trend of − 3.6% ± 2.7% for yearly snow cover extent and of − 15.1 days ± 11.6 days for snow cover duration.”
According to Notarnicola, the few existing counter-trends are not very encouraging. For instance, although the eruption of the El Chichon volcano in Mexico in the early 1980s caused a slight cooling which counteracted the decrease in snowfall, this phenomenon had not lasted long.
“In general, over these 38 years of analysis there are also some cases of increases in both coverage and snow days, specifically in parts of Central Asia and some valleys in the United States,” Notarnicola added. “There are no consensus explanations for these phenomena, but they could be other effects of climate change, for example variations in currents and winds or specific microclimatic conditions. In any case, these are a few exceptions in a very negative global context,” she concluded.
The study is published in the journal Nature Scientific Reports.