After more than three months, the “Dixie Fire” finally went out on Monday.

Named for a road it ran along, it was the second largest forest fire in California on record.

Its flames have burned a scar of almost 4,000 square kilometers into the landscape, leaving charred trees and houses on an area larger than Mallorca.

Not a drop of rain had fallen in California for months.

As in the previous year, this drought led to a particularly large number of forest and bush fires.

Only last weekend did heavy rainfall end the dry period on the American west coast - and with it the forest fire season.

Rebecca Hahn

Freelance writer in the science of the Frankfurter Allgemeine Sonntagszeitung.

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It was another summer of extremes: Not only in North America, enormous fires raged, also large parts of Siberia and the Mediterranean region were in flames for weeks. In Yakutia, more than 8.4 million hectares of forest burned - almost four times as much as during an average forest fire season. At the same time, Turkey experienced more and more violent forest fires than in decades; Fires were also blazing in many regions in neighboring Greece. In July and August alone, the fires in the northern hemisphere released a record amount of more than 2.6 billion tons of CO₂, reported Copernicus, the atmosphere monitoring service of the European Union and the space agency ESA.

Forest and bush fires are nothing unusual in and of themselves. Regular fires are an important part of many ecosystems. In the taiga and savannah, bushfires help keep the landscape open, and in forests, the fires make room for regrowing young trees. And as a study published in the “Philosophical Transactions of The Royal Society B” in 2016 shows, the area affected by fires around the world was actually smaller in the past few decades than in the centuries before.

But with climate change, the number and intensity of forest fires threatens to increase.

Global warming is already promoting the fires locally: For example, scientists have found that catastrophic bush fires on the scale that Australia experienced from June 2019 to March 2020 have become thirty percent more likely due to climate change.

A study published in the Proceedings of the National Academy of Sciences (PNAS) in 2016 also showed that half of the area burned in the American West from 1984 to 2015 can be attributed to climate change.

The days with so-called "fire weather" are increasing

"Research shows that there is a very strong link between global warming and an increase in the risk of forest fires," says Cathy Whitlock, professor emeritus of geosciences at Montana State University, who has been studying vegetation, fires and climate history in North and South America for decades researches. The influence of the climate can now be clearly distinguished from other factors, such as land use.

Global warming will result in more heat waves and periods of drought, making days with so-called "fire weather" more frequent. This is the term used to describe weather conditions in which fulminant fires can arise in the first place - i.e. high temperatures with low humidity, paired with strong winds. According to the 2019 Intergovernmental Panel on Climate Change, the frequency of fires will increase by 27 percent globally in 2050 compared to 2000, mainly due to meteorological changes.

The forest fire season in the western United States no longer lasts four months, but in some places more than half a year.

A study published in the PNAS in June also shows that forest fires are also raging in higher and higher elevations.

High temperatures and early snowmelt dry out hills and mountainsides that used to be too humid to catch fire.

For example, forest fires between 1984 and 2017 were able to move up the slope by an average of seven and a half meters.