The natural cooling effect of snow in northern forests following forest fires is rapidly diminishing. As a result, a fragile climate equilibrium threatens to disappear, potentially leading to additional warming in one of the most climate-sensitive regions on Earth. This is the conclusion of new research by Vrije Universiteit Amsterdam.
The research is published in the scientific journal Proceedings of the National Academy of Sciences.
Snow albedo
After a forest fire, the landscape in northern regions often remains open and covered with snow for a long time. This snow reflects a great deal of sunlight and makes the Earth's surface brighter—an effect known as snow albedo. For years, this compensated for part of the warming caused by CO2 emissions from forest fires.
VU Earth systems scientists Max van Gerrevink and Sander Veraverbeke, together with international colleagues, investigated how forest fires influence the climate. In doing so, they looked not only at the enormous emissions of greenhouse gases but also at changes in vegetation, soil, and the clarity of the Earth's surface.
Due to climate change, snow remains on the ground for increasingly shorter periods in the spring. Lead author Van Gerrevink: “This actually weakens the natural mechanism that helped to mitigate the consequences of forest fires. As a result, forest fires in northern forests are increasingly amplifying global warming, rather than partially counteracting it.”
Increase in forest fires
Canada experienced the largest forest fire season ever recorded in 2023. The emissions from those fires even exceeded the annual fossil fuel emissions of almost every country in the world. 2025 has also become one of the most severe fire years since national monitoring began in the 1970s.
The study shows that the cooling effect of snow has decreased by nearly 30 percent since the 1960s. Whereas in the past almost half of Canadian forest fires eventually reached natural climate equilibrium - where cooling by snow fully compensated for emissions -this now applies to only about one in four or five fires. Senior author Veraverbeke: “That is particularly worrying because it is precisely the largest and most carbon-intensive fires that benefit the least from the cooling effect of snow. The effect accumulates as the Earth continues to warm.”
Targeted measures have an effect
Nevertheless, the scientists emphasize that targeted measures can still make a difference. By intervening in places where wildfires cause the greatest climate damage, governments can, according to the researchers, contribute relatively effectively and sometimes even cost-efficiently to limiting further warming.
The work was funded by the European Research Council through a Consolidator grant under the European Union’s Horizon 2020 research and innovation program.