Climate change has increased frequency and intensity of conditions favorable to extreme wildfires, report shows

A report by an international group of researchers including three Brazilians shows that climate change tripled the probability of weather conditions favoring unprecedented wildfires in Canada and multiplied it by a factor of 20 in western Amazonia between March 2023 and February 2024. Global carbon emissions were 16% above average.

By Luciana Constantino  |  Agência FAPESP – Climate change tripled the probability of favorable weather conditions for unprecedented wildfires in Canada and multiplied it by a factor of 20 in western Amazonia between March 2023 and February 2024, boosting greenhouse gas emissions, causing environmental devastation, and killing inhabitants of the region.

This is just one of the conclusions of a report written by an international group of researchers and published on August 14. Moreover, the authors state, although the area burned by wildfires globally was similar to the average for previous years – about 3.9 million square km, more than the size of India – carbon emissions worldwide were 16% above average, totaling 8.6 billion metric tons (Gt) of CO2, the seventh-highest amount since 2003.

The State of Wildfires 2023-24 report is published in the journal Earth System Science Data, and annual updates will follow. The authors catalogue extreme wildfire events in a range of ecosystems and biomes, from savanna and peatland to boreal and tropical forest, and discuss their causes and predictability, considering the extent to which they can be attributed to human-driven climate change and land use change, and assessing future risks under different climate scenarios.

To this end, they developed tools, compiled data from all countries and used artificial intelligence (AI) in an effort to understand and predict extreme wildfires, and to deliver actionable information to policymakers and society in general. Graphs, maps and charts displaying the results can be viewed online.

According to the report, the extreme fire “season” in western Amazonia (which includes the Brazilian states of Amazonas, Acre, Roraima and Rondônia) was driven by prolonged drought linked to the strong El Niño. The drought and other weather conditions explained 68% of the fires, but anthropic activities such as logging, agricultural expansion and landscape fragmentation also contributed. “Our analyses revealed that multiple drivers were needed to cause areas of extreme fire activity,” the authors write regarding the phenomenon worldwide.

Led by the University of East Anglia (UEA) in the United Kingdom, and co-led by the UK Met Office, the UK Center for Ecology and Hydrology (UKCEH) and the European Center for Medium-Range Weather Forecasts (ECMWF), the report has 44 authors, including three Brazilian researchers.

One of the three is Maria Lucia Ferreira Barbosa, who has a PhD from the National Space Research Institute (INPE) and is now affiliated with the Federal University of São Carlos (UFSCar) in São Paulo State, Brazil.

“The purpose of the report is to present a global overview of wildfires researched by regional experts. It was important to assemble this regional expertise, with a diverse team in terms of both countries and knowledge areas. Another interesting point is the rapid updating of the previous year’s data, so that the models develop continuously. We plan to produce more robust forecasts and diagnoses every year, so that stakeholders can access the research and formulate strategies for dealing with the impacts,” Barbosa told Agência FAPESP.

The second Brazilian author of the report is biologist Liana Anderson, a researcher at the National Disaster Surveillance and Early Warning Center (CEMADEN). She stressed the importance of “understanding the past and present in order to plan preventive action for the future”. 

“By analyzing regions over time, we can identify novel points of attention. We’ve created an open-access online database that enables people to do different kinds of research to answer countless questions. We need to understand what fire means in terms of barriers to achieving Brazil’s socioeconomic and environmental goals, and in terms of the consequences, especially biodiversity loss, impoverishment and food insecurity, for example,” Anderson said.

The increase in wildfires in South America during the period was slightly below average, according to the report, but Amazonas State was an exception, with record levels owing to a historic drought and a severe deterioration in air quality.

Manaus, the state capital and most populous city in the Amazon, had the second-worst air quality in the world in October 2023, exposing more than 2 million inhabitants to the smoke and hazardous particulate matter from wildfires, the report notes. The problem was so bad that federal prosecutors filed suit against Amazonas in November 2023, demanding evidence that the state was investing in fire prevention and combat in line with the Plan for the Prevention and Control of Deforestation and Fires in the Amazon (PPCDAm). Manaus was once again blanketed by smoke from wildfires in August 2024.

Extreme events largely due to drought were also recorded in Venezuela and parts of Bolivia and Peru. A fire in Valparaíso, Chile, in February 2024 resulted in at least 131 deaths and widespread destruction of property.

The group used a combination of data from global satellite observations, models and regional experts’ insights. “We analyzed a global dataset focusing on metrics such as the date of the fire, perimeter and ignition point to see if this dataset was satisfactory to represent the extreme events. We produced figures and metrics for events in Greece, Valparaíso (Chile), Canada and Australia, and were able to show that it worked for this purpose,” said the third Brazilian author of the report, Guilherme Mataveli, a remote sensing specialist in INPE’s Earth Observation and Geoinformatics Division.

The Pantanal, the South American biome with the world’s largest continuous wetlands, is expected to rank high on the list of areas with the most wildfires in the 2024-25 season, given the number of events already recorded, Mataveli remarked. In the first seven months of this year, the number of fires reached 4,756, the highest since 1998 when the current time series began, according to data from INPE.

Mataveli recently conducted postdoctoral research on greenhouse gas emissions from wildfires at UEA’s Tyndall Center for Climate Change Research, with supervision by Dr. Matthew Jones, the lead author of the report, and with funding from FAPESP.

“Last year we saw wildfires killing people, destroying properties and infrastructure, causing mass evacuations, threatening livelihoods, and damaging vital ecosystems. Wildfires are becoming more frequent and intense as the climate warms, and both society and the environment are suffering from the consequences,” Jones said in a press release.

Extreme fire season

In addition to the catalogue of high-impact fires globally, the report focuses on explaining the causes of extreme fire events 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. 

As a result, they concluded, the extreme fire-prone weather of 2023-24 was made at least three times more likely in Canada, 20 times more likely in Amazonia, and twice as likely in Greece, which again suffered the consequences in August 2024, with evacuation orders on the outskirts of Athens and an appeal to the European Union for assistance to contain the fires.

“If we don't think more realistically, and keep our models updated, we won’t be able to prepare properly for the massive events that are going to hit us. The events and impacts are happening to a far greater extent than we expected,” Anderson said.

With regard to global carbon emissions from the fires, Canada’s boreal forests contributed over nine times the average and accounted for almost a quarter of total emissions. On the other hand, emissions from Africa’s savannas decreased.

Fire weather prediction data in Canada showed a mild anomalous signal one to two months in advance, whereas events in Greece and Amazonia had shorter predictability horizons.

Future

The climate models used by the report’s authors suggest that the frequency and intensity of extreme wildfires will increase by the end of this century, particularly under scenarios with persistently high levels of greenhouse gas emissions.

By 2100, events of similar magnitude to those of 2023 in Canada are projected to occur 6.3–10.8 times more frequently under a medium-to-high emissions scenario. The frequency of extreme fire seasons may increase almost threefold in western Amazonia and double in Greece. On the other hand, their likelihood should decrease if emissions fall significantly.

For the 2024-25 season, the models predict an above-average probability of extreme fire conditions (hot, dry and windy) in parts of North and South America, where fire-prone conditions were observed in June and July 2024 in California (USA), Alberta and British Columbia (Canada) and the Pantanal (Brazil).

Support
The research informing the report was also supported by FAPESP via four projects (20/15230-5; 21/07660-2; 20/16457-3; and 19/25701-8.

The State of Wildfires 2023–2024 report is at: https://essd.copernicus.org/articles/16/3601/2024/essd-16-3601-2024.html.