Extreme fires are on the rise, pushing up carbon dioxide emissions from wildfires at a global scale. Canada in particular had a record-breaking fire season, burning through almost a decade’s worth of its fire emissions in just one fire season, according to the first annual wildfires assessment.

The first State of Wildfires report, set to be published annually, assesses extreme wildfires that happened between March of 2023 and February of 2024, their causes, and if they could have been predicted. It also evaluates how the risk of similar events will change in future.

Carbon emissions from wildfires globally were 16% above average, totalling 8.6 billion tonnes of carbon dioxide, according to the report led by the University of East Anglia, the UK Centre for Ecology and Hydrology, the Met Office, and the European Centre for Medium-Range Weather forecasts. Its authors include many of the researchers who were brought together by the ESA-Future Earth Joint programme FLARE project.

“Last year, we saw wildfires killing people, destroying properties and infrastructure, causing mass evacuations, threatening livelihoods, and damaging vital ecosystems,” said the lead author, Dr Matthew Jones, Research Fellow at the Tyndall Centre for Climate Change Research at UEA who is a member of the Global Carbon Project. “Wildfires are becoming more frequent and intense as the climate warms, and both society and the environment are suffering from the consequences.” 

The immediate and long-term impacts

An unusually high number of fires were seen in northern parts of South America, particularly in Brazil’s Amazonas state and in neighboring areas of Bolivia, Peru, and Venezuela, causing extremely poor air quality. 

The loss of carbon stocks from boreal forests in Canada and tropical forests in South America have lasting implications for the Earth’s climate. Forests take decades to centuries to recover from fire disturbance, meaning that extreme fire years such as 2023-24 result in a lasting deficit in carbon storage for many years to come.

“In Canada, almost a decade’s worth of carbon emissions from fire were recorded in a single fire season – more than 2 billion tonnes of CO2,” said Dr Jones. “In turn, this raises atmospheric concentrations of CO2 and exacerbates global warming.”

If it had not been a quiet fire season in the African savannahs, then the 2023-24 fire season would have set a new record for CO2 emissions from fires globally. The authors classified a region’s fire season as “extreme” based on a ranking of burned area, carbon emissions and fire count, if the ranking was within the upper quartile across all fire seasons for the period March 2002–February 2024.

Climate change is making extreme fire weather more likely

Along with cataloging high-impact fires globally, the report focuses on explaining the causes of extreme fire extent in Canada, western Amazonia, and Greece. Fire weather – characterized by hot, dry conditions that promote fire – has shifted significantly in all three focal regions when compared to a world without climate change. Climate change made the extreme fire-prone weather of 2023-24 at least three times more likely in Canada, 20 times more likely in Amazonia, and twice as likely in Greece.

The team used attribution tools to distinguish how climate change has altered the area burned by fires versus a world without climate change. It found that the vast extent of wildfires in Canada and Amazonia in the 2023-24 fire season was almost certainly greater due to climate change (with more than 99% confidence).

Underlying causes of extreme fires

Several factors control fire, including weather conditions influenced by climate change, the density of vegetation on the landscape influenced by climate and land management, and ignition opportunities influenced by people and lightning.

Disentangling the influence of these factors can be complex, but fire models can help reveal the influence of different factors on extreme fire activity.

Activities such as agriculture, forestry, and dedicated fire management efforts all influence the landscape, and can reduce the density of vegetation. In addition, firefighters also help to reduce fire spread by tackling active wildfires. When wildfires meet areas with sparse vegetation or more aggressive firefighting strategies, they can run out of fuel or be contained.

During 2023-24, the fourth most powerful El Niño event on record drove a prolonged drought and heatwave in South America. This natural feature of Earth’s climate increases temperatures and reduces rainfall in Amazonia every three to eight years, but it is increasingly superimposed on higher temperatures due to climate change. 

The report found that human activities increased the extent of the 2023 wildfires in western Amazonia. In this region, the expansion of agriculture has resulted in widespread deforestation and forest degradation. This has left forests more vulnerable to fire during periods of drought and fire weather, amplifying the effect of climate change.

Predicting future extreme fire risk

Using climate models, the team found that by 2100, under a mid-to-high greenhouse gas emissions scenario (SSP370), wildfires similar in scale to the 2023-24 season will become over six times more common in Canada. Western Amazonia could see an extreme fire season like 2023-24 almost three times more frequently. 

Stronger action to reduce greenhouse gas emissions can limit the future likelihood of extreme fires, although Canada will see a rise in extreme wildfires even under low emissions scenarios, highlighting the need for adaptation and managing the forest’s fuel load. 

The report was published in the journal Earth System Science Data.