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Starting in March 2023, Canada burned for eight months, with flames reaching all 13 provinces and territories in the country’s most devastating fire season. At least 150,000 people were evacuated, and tens of millions of people were affected by smoke across North America. In New York, residents experienced the worst air quality in half a century.

Five months later, Greece was hit by the largest forest fire in the European Union to date, destroying nearly 900 square kilometers of forest and killing 19 immigrants. Near the equator, the Amazon experienced a record number of fires. For months, satellite images showed thick clouds of smoke enveloping entire countries and charred areas of land, the edges of which were highlighted by orange flames.

We have climate change to thank for these unprecedented fires. On Tuesday, an international group of scientists released the annual State of Wildfires report, which analyzed global wildfires between March 2023 and February 2024 and concluded without a doubt that climate change has exacerbated the conditions that fueled the flames. According to the report, last year’s wildfires in Canada, Greece and the Amazon were at least three times more likely – and up to 20 times more likely – than they would have been without human-caused global warming.

The scientists also found that all of this burning released an incredible 8.6 billion tons of carbon dioxide – 3 billion tons more than the U.S. emitted from burning fossil fuels in 2022.

“This release of greenhouse gases … creates a positive feedback loop that could then lead to more extreme fires,” said Douglas Kelley, a fire researcher at the UK Centre for Ecology and Hydrology and one of the report’s authors. “So if we continue to emit greenhouse gases at the same level as we are now, we will see at least six to 11 times more of these fires by the end of the century.”

To understand how climate change increases the likelihood, researchers analyzed regional data to identify changes in fire weather – a term that describes the hot, dry and often windy conditions in which wildfires can easily start. Climatic and ecological factors such as changes in rainfall or excessive plant growth can make environments more flammable. Add in drought and heat waves, both of which are exacerbated by climate change, and fire weather becomes more extreme.

But those conditions only mean that a large fire could easily start and spread—not that it necessarily will. Kelley says even with a good understanding of the risks, predicting the next extreme fire remains a tricky endeavor, in part because human behavior can make a big difference.

“People go out and set fires, or they can put out fires,” Kelley said. “And while climate change has caused changes in fires, so has human fragmentation of the landscape.” In some places, agriculture and roads prevent fires from spreading as far. In other places, deforestation can make forests drier, giving them fuel to burn more vigorously. And in the U.S., decades of poor forest management set the stage for extreme fires by suppressing naturally occurring fires and turning the landscape into a powder keg of overgrown vegetation.

Because each area has its own complexity, the researchers focused their analysis on three different regions with large wildfires and meaningful data: Canada, Greece and the Amazon.

In Canada, the burning of over 50,000 square miles of boreal forest caused about a quarter of global carbon emissions during the one-year study period. Overall, the report found that the warming planet made Canada’s fires three times more likely. But the researchers also point out that the damage would have been even greater had Canada’s landscape not been altered by humans through agriculture, firefighting and urban infrastructure. In Greece, similar factors prevented the 2023 Evros fire from being worse than it was.

Of all the regions examined in the report, the Amazon rainforests – which include the Brazilian state of Amazonas and adjacent parts of Bolivia, Peru and Venezuela – appear to be most affected by climate change. Here, researchers found a 20 times higher likelihood of severe wildfires. And in 2023, a particularly strong El Niño – a multi-year climate pattern influenced by cycles of warm ocean currents – contributed to a record-breaking fire season.

“El Niño is making it harder for rain to form in the Amazon, causing drier and hotter weather,” says Maria Lucia Barbosa, a fire researcher at the University of São Carlos in Brazil and one of the study’s authors. “When people make fires, they spread easily under these conditions.” According to the report, the fires also claimed a heavy toll on dozens of indigenous peoples who live in the area and whose livelihoods depend on a healthy forest.

The State of Wildfire report also looked at damage from other significant fires during the study period, though not to the same depth. In Hawaii, the town of Lahaina was destroyed in an inferno in August that killed 102 people. In Australia, more than 300,000 square miles burned during the Southern Hemisphere summer — the largest wildfire season in more than a decade. In Chile, hundreds of fires broke out amid a megadrought. Globally, the report found that climate change has made extreme fires twice as likely. A separate analysis of satellite data released in June found that extreme wildfires have become twice as frequent and intense over the past two decades.

This article originally appeared in Grist at https://grist.org/wildfires/wildfire-2023-canada-greece-amazon-climate-change-fueled-last-years-extreme-wildfires-some-more-than-others/.

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