Last year’s wildfires in Canada and parts of the Amazon were significantly more likely due to climate change—at least three times more probable—and they significantly increased global CO2 emissions from fire, according to a new systematic annual review.
This annual report is co-directed by the University of East Anglia (UEA, UK), the UK Centre for Ecology & Hydrology (UKCEH), the Met Office (UK), and the European Centre for Medium-Range Weather Forecasts (ECMWF, UK).
Released today in the journal Earth System Science Data, the report reveals that global carbon emissions from wildfires were 16% above the average, amounting to a staggering 8.6 billion tons of carbon dioxide. Emissions from the Canadian boreal forests were over nine times the average for the last two decades, making up nearly a quarter of the worldwide emissions.
If the African savannahs hadn’t experienced a quieter fire season, the 2023-24 fire season could have set a new record for global CO2 emissions from wildfires.
In addition to releasing substantial CO2, the fires in Canada led to over 230,000 evacuations and the tragic loss of eight firefighters’ lives. An extraordinarily high number of fires were also reported in the northern regions of South America, especially in Brazil’s Amazonas state, as well as in areas of Bolivia, Peru, and Venezuela. This situation resulted in the Amazon facing some of the worst air quality ratings globally.
Additionally, intense and quickly spreading wildfires in Chile, Hawaii, and Greece resulted in direct fatalities of 131, 100, and 19, respectively. These are among the numerous wildfires worldwide that had significant repercussions for communities, economies, and ecosystems.
“Last year, the wildfires caused fatalities, destroyed homes and infrastructure, led to mass evacuations, jeopardized livelihoods, and harmed crucial ecosystems,” stated Dr. Matthew Jones, the lead author of this year’s analysis and a Research Fellow at the Tyndall Centre for Climate Change Research at UEA.
“Wildfires are becoming increasingly frequent and severe due to climate change, resulting in detrimental impacts on both society and the environment.”
The depletion of carbon stocks from boreal forests in Canada and tropical forests in South America has long-term effects on the Earth’s climate. Forests typically take decades to centuries to bounce back from fire disruptions, which means that extreme fire years like 2023-24 will cause a prolonged deficit in carbon storage.
“In Canada, a single fire season recorded nearly a decade’s worth of carbon emissions from fires—over 2 billion tons of CO2,” Dr. Jones added. “This, in turn, increases atmospheric CO2 levels and worsens global warming.”
Climate change made the 2023-24 fire season more extreme
Aside from documenting high-impact fires globally, the report sought to explain the causes behind the severe fire activity in three specific regions: Canada, western Amazonia, and Greece.
Fire weather conditions, defined by hot and dry climates that foster fire, have changed dramatically in all three noted regions when compared to a world without climate change. Climate change made the extreme fire-prone conditions of 2023-24 at least three times more likely in Canada, 20 times more likely in Amazonia, and twice as likely in Greece.
The report employed advanced attribution tools to clarify how climate change has modified the areas affected by wildfires compared to a climate-unaltered world. It confirms that the large wildfires experienced in Canada and Amazonia during the 2023-24 season were almost certainly exacerbated by climate change (with more than 99% confidence).
“It is nearly certain that the wildfires in Canada and Amazonia during 2023 were larger as a result of climate change,” asserted Dr. Chantelle Burton, Senior Climate Scientist at the Met Office.
“We are already witnessing the effects of climate change on weather patterns globally, disrupting typical fire dynamics in many areas. It is crucial for fire research to investigate how climate change influences fires, as this provides valuable insights into how these fires may evolve in the future.”
The likelihood of extreme wildfires will increase, but can be managed
Climate models referenced in the report indicate that the frequency and severity of extreme wildfires are expected to rise by the century’s end, especially in scenarios where greenhouse gas emissions remain high.
According to the report, by 2100, wildfires akin to those in the 2023-24 season could become over six times more frequent in Canada under a mid-to-high greenhouse gas emissions scenario (SSP370). Meanwhile, western Amazonia could face extreme fire seasons nearly three times as often, and Greece could see fire events of similar magnitude double in occurrence.
“As long as greenhouse gas emissions continue to escalate, the chance of extreme wildfires will also rise,” noted Dr. Douglas Kelley, Senior Fire Scientist at the UK Centre for Ecology & Hydrology.
However, the anticipated increase in the likelihood of severe wildfire occurrences similar to those in 2023-2024 can be mitigated by reducing greenhouse gas emissions. Following a low emissions scenario (SSP126) could restrict future incidences of extreme fires. For western Amazonia, the frequency of occurrences akin to 2023-2024 is projected to remain unchanged by 2100 compared to the current decade. Meanwhile, in Canada, the future increase in extreme fire frequency may decrease from sixfold to just double, and in Greece, the rise may be limited to 30%.
“Regardless of the emissions scenario adopted, the risk of extreme wildfires is set to increase in Canada, underscoring the necessity for society not just to reduce emissions but also to adapt to changing wildfire threats,” concluded Dr. Kelley.
“These projections stress the urgent need to swiftly decrease greenhouse gas emissions and properly manage vegetation to lower the risks and impacts of increasingly severe wildfires on both society and ecosystems.”
Disentangling the factors behind extreme fires
Various elements affect fire behavior, including weather conditions shaped by climate change, vegetation density influenced by climate and land management practices, as well as ignition sources such as human activities and lightning.
Understanding how these factors contribute can be challenging; however, the report utilized advanced fire models to clarify their respective impacts on extreme fire incidents.
The findings indicate that areas burned by fire in Canada and Greece would likely have been more extensive if not for human alterations to the landscape. Human activities such as agriculture, forestry, and specific fire management strategies all play a role in influencing wildfire dynamics.
The environment can be affected, leading to a decrease in plant life density. Additionally, firefighters play a vital role in slowing the spread of fires by addressing active wildfires. When wildfires encounter areas with limited vegetation or when more aggressive firefighting methods are employed, they may deplete their fuel sources or be effectively contained.
“In Canada and Greece, there was a combination of extreme fire weather and a surplus of dry vegetation that contributed significantly to the increase in both the number and size of fires last year,” commented Dr. Francesca Di Giuseppe, Senior Scientist at ECMWF.
She further explained, “Our research indicates that elements such as fire suppression efforts and landscape fragmentation caused by human activities have likely had a significant influence on reducing the overall burned areas.”
“While human activities significantly impacted the most severe fire incidents we studied, our findings reveal that the final scope of these fires was primarily dictated by the simultaneous presence of several predictable factors — chiefly weather conditions, the abundance of flammable material, and moisture levels — rather than direct human intervention.”
The analysis indicated that human actions exacerbated the 2023 wildfires in western Amazonia. In this area, agricultural expansion has led to significant deforestation and degradation of forests. Consequently, these forests have become more susceptible to fires during dry spells and heightened fire conditions, which in turn intensifies the impacts of climate change.
During the period of 2023-24, one of the most intense El Niño events recorded caused an extended drought and heatwave across South America. This climatic phenomenon, which occurs every three to eight years, typically raises temperatures and lowers rainfall across Amazonia, and it’s increasingly occurring alongside elevated temperatures due to climate change.
“In many tropical forests like those in Amazonia, the combination of deforestation and agricultural expansion has intensified how climate change affects wildfire risk, making these crucial ecosystems more exposed,” noted Dr. Burton.
Looking ahead to the 2024-2025 fire season
Fire risk forecasting is an expanding field of study, with early warning systems already established based solely on weather conditions. For instance, in Canada, predictions of extreme fire weather were made two months ahead of time, offering early signs of a high fire risk in 2023. In contrast, the situations in Greece and Amazonia had shorter prediction windows.
For the upcoming 2024-25 season, forecasts indicate a sustained above-average chance of fire weather—characterized by hot, dry, and windy conditions—in certain regions of North and South America. This suggests potential wildfire risks in places like California, Alberta, British Columbia, and the Brazilian Pantanal in June and July.
Dr. Di Giuseppe remarked, “We aren’t particularly shocked by the recent fires reported in the news, as we had already anticipated above-average fire weather in specific areas of North and South America. However, the large-scale Arctic fires we’ve seen lately came as a surprise — an area we will explore further in our upcoming report.”
