Extreme fire risk has grown exponentially in a hotter climate

Unprecedented wildfires in Canada and parts of Amazonia last year were at least three times more likely due to climate change, and significantly contributed to the global increase in carbon dioxide emissions from fires. 

These alarming findings are detailed in the first edition of the State of Wildfires report, which examines extreme wildfires of the 2023-2024 fire season (March 2023 – February 2024), while also exploring their causes. 

Fires under different climate scenarios 

For the investigation, the scientists examined whether such events could have been predicted and assessed how risk of similar occurrences might change under different climate change scenarios in future.

The report, which will now be published annually, is a collaborative effort led by the University of East Anglia (UEA) in the UK, alongside the UK Center for Ecology & Hydrology (UKCEH), the Met Office, and the European Center for Medium-Range Weather Forecasts (ECMWF). 

CO2 emissions from fires

Some of its main findings include the fact that carbon emissions from wildfires globally were 16% above average, totaling 8.6 billion tons of carbon dioxide. 

The report also revealed that emissions from fires in Canada’s boreal forests were over nine times the average of the past two decades, contributing nearly a quarter of the global emissions from wildfires.

According to the experts, if it had not been a quiet fire season in the African savannahs, the 2023-24 fire season would have set a new record for CO2 emissions from fires globally. 

Devastating fires by region 

The situation in Canada was particularly dire, with fires leading to over 230,000 evacuations and the loss of eight firefighters’ lives. 

Additionally, northern parts of South America, particularly Brazil’s Amazonas state and neighboring areas of Bolivia, Peru, and Venezuela, also experienced an unusually high number of fires. This resulted in the Amazon region facing some of the worst air quality ratings on the planet.

Elsewhere, wildfires in Chile, Hawaii, and Greece were especially devastating, causing 131, 100, and 19 direct fatalities, respectively. These incidents were among the many wildfires worldwide that had significant impacts on society, the economy, and the environment.

More frequent fires with climate change 

“Last year, we saw wildfires killing people, destroying properties and infrastructure, causing mass evacuations, threatening livelihoods, and damaging vital ecosystems,” said lead author Matthew Jones, a research fellow at the Tyndall Center for Climate Change Research at UEA. 

“Wildfires are becoming more frequent and intense as the climate warms, and both society and the environment are suffering from the consequences.”

The loss of carbon stocks from boreal forests in Canada and tropical forests in South America has long-term implications for the Earth’s climate. Forests require decades to centuries to recover from fire disturbances, meaning that extreme fire years like 2023-24 result in a persistent 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 two billion tons of CO2,” Jones said. “In turn, this raises atmospheric concentrations of CO2 and exacerbates global warming.”

The role of climate in extreme fires

The report also underscores the role of climate change in making the 2023-24 fire season more extreme. It focused on explaining the causes of widespread fire extent in three regions: Canada, western Amazonia, and Greece. 

Fire weather, characterized by hot, dry conditions that promote fires, has shifted significantly in all three areas when compared to a world without climate change. 

The report found that 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.

Cutting-edge attribution tools were used to differentiate how climate change has altered the area burned by fires compared to a world without these changes. 

Changing weather patterns worldwide

The findings showed with more than 99% confidence that the vast extent of wildfires in Canada and Amazonia during the 2023-24 fire season was almost certainly greater due to climate change.

“It is virtually certain that fires were larger during the 2023 wildfires in Canada and Amazonia due to climate change,” said Chantelle Burton, a senior climate scientist at the Met Office.

“We are already seeing the impact of climate change on weather patterns all over the world, and this is disrupting normal fire regimes in many regions. It is important for fire research to explore how climate change is affecting fires, which gives insights into how they may change further in the future.”

Frequency and intensity of extreme fires

Looking ahead, climate models used in the report suggest that the frequency and intensity of extreme wildfires will increase by the end of the century, particularly in scenarios where greenhouse gas emissions remain high.

By 2100, under a mid-to-high greenhouse gas emissions scenario (SSP370), wildfires similar in scale to those seen during 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, while Greece could experience such fire seasons twice as often.

“As long as greenhouse gas emissions continue to rise, the risk of extreme wildfires will escalate,” said Douglas Kelley, a senior fire scientist at the UK Center for Ecology & Hydrology. 

Low emissions could limit extreme fires

However, the report also suggests that following a low emissions scenario (SSP126) could significantly limit the future likelihood of extreme fires.

For example, in western Amazonia, the frequency of events like those in 2023-24 might not increase by 2100 compared to the current decade if emissions are kept low.

In Canada, the increase in the frequency of extreme fires could be reduced from a factor of six to a factor of two, while in Greece, the rise could be limited to 30%.

“Whatever emissions scenario we follow, risks of extreme wildfires will increase in Canada, highlighting that society must not only cut emissions but also adapt to changing wildfire risks,” Kelley said.

Interplay of factors controlling fires

The report also delves into the complex interplay of factors controlling fire, including weather conditions influenced by climate change, the density of vegetation on the landscape shaped by climate and land management, and ignition opportunities driven by human activity and lightning.

Disentangling the influence of these factors can be challenging, but the report used advanced fire models to reveal how these different elements influenced the extreme fire activity observed.

In Canada and Greece, for instance, the report found that the area burned by fires would likely have been larger if the landscape had not been altered by human activities. Actions such as agriculture, forestry, and dedicated fire management efforts influence the landscape and can reduce vegetation density, which in turn can limit the spread of fires.

Moreover, firefighters play a critical role in containing active wildfires, and when fires encounter areas with sparse vegetation or more aggressive firefighting strategies, they can be stopped from spreading further.

“In Canada and Greece, a mix of severe fire weather and plenty of dry vegetation reinforced one another to drive a major uptick in the number and extent of fires last year,” said Francesca Di Giuseppe, a senior scientist at ECMWF.

“But our analysis also shows that factors such as suppression and landscape fragmentation related to human activities likely played important roles in limiting the final extent of the burned areas.”

Human activities and fire-prone weather

The report also highlighted how human activities have increased the extent of the 2023 wildfires in western Amazonia. The expansion of agriculture in this region has led to widespread deforestation and forest degradation, making forests more vulnerable to fire during periods of drought and fire-prone weather, thus amplifying the impact of climate change.

During the 2023-24 fire season, the fourth most powerful El Niño event on record triggered a prolonged drought and heatwave in South America. El Niño, a natural climate phenomenon, increases temperatures and reduces rainfall in Amazonia every three to eight years, but it is now being superimposed on the higher temperatures driven by climate change.

“In many tropical forests like Amazonia, deforestation and the expansion of agriculture have exacerbated the effects of climate change on wildfire risk, leaving these vital ecosystems more vulnerable,” Burton explained.

Forecasting fire risk

The report also casts an eye toward the 2024-2025 fire season, noting that forecasting fire risk is a growing area of research and that early warning systems have already been developed based on weather factors alone.

For instance, extreme fire weather in Canada was predicted two months in advance in 2023, providing early indications of high fire potential. However, events in Greece and Amazonia had shorter windows of predictability.

“We’re not particularly surprised by some of the recent fires in the news, as above-average fire weather was predicted in parts of North and South America. However, the extensive Arctic fires we’ve witnessed recently have caught us by surprise – something to look at in our next report,” said Di Giuseppe.

According to the authors, the report represents their first annual effort to catalogue extreme wildfire events, explain their occurrence, and predict future risks.

“By consolidating state-of-the-art wildfire science and delivering key insights relevant to policymakers, disaster management services, firefighting agencies, and land managers, we aim to enhance society’s resilience to wildfires and promote advances in preparedness, mitigation, and adaptation.”

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

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