Human-caused climate change made the “unprecedented” wildfires that spread across Brazil’s Pantanal wetlands in June 2024 between four and five times more likely, according to a new rapid attribution study.
South America’s Pantanal – the world’s largest tropical wetland – experienced exceptionally hot, dry and windy conditions in June, causing blazes in the region to soar.
The World Weather Attribution (WWA) service finds that the month was the hottest, driest and windiest year in the 45-year record.
The team conducted an attribution study to find the “fingerprint” of climate change on these weather conditions.
They find that, in a world without climate change, these conditions would be very rare – occurring only once every 161 years.
In today’s climate, which has already warmed by 1.2C above pre-industrial temperatures as a result of human-caused warming, these conditions are a one-in-35 year event.
The authors also explore how wildfires in the region could continue to worsen as the planet warms.
They find that if that planet reaches warming levels of 2C, the likelihood of these conditions could double, to once every 18 years.
Soaring fires
The vast Pantanal wetland extends across Brazil, Bolivia and Paraguay.
It is one of the most biodiverse places on earth, home to more than 4,700 plant and animal species.
Every year, hot and dry weather conditions make the wetland prone to wildfires – usually between July and September.
By June this year, intense wildfires were already soaring. The number of Pantanal fires increased by 1,500% in the first half of this year compared to the same period in 2023, according to data from Brazil’s National Institute for Space Research reported by the Brasil de Fato newspaper.
This amounts to more than 1.3m hectares of the wetland burned so far this year – an area around eight times the size of London.
Around 2,500 fires were identified in June, which is the highest number since 1998 and more than six times the level reported in 2020, which was “known as the ‘year of flames,’ when wildfires ravaged the area and sparked widespread outcry”, the Associated Press said.
The region is currently experiencing its worst drought in 70 years, which Brazil’s government has said is being “intensified by climate change and one of the strongest El Niño phenomena in history”.
Prolonged dry periods, high temperatures and land-use change all contribute to wildfire conditions, says Dr Maria Lucia Barbosa, a postdoctoral researcher at the Federal University of São Carlos in Brazil, who was not involved in the attribution study. She tells Carbon Brief:
“While fires are a natural part of the Pantanal ecosystem, the recurrence of extreme fire seasons – such as the current one, shortly after the devastating 2020 fires – suggests that, alongside climate change, a new fire regime may be emerging in the ecosystem, characterised by increased severity and frequency.”
Hot, dry and windy
Wildfire intensity and duration are influenced by a wide range of factors, including weather, vegetation and fire management strategies.
The authors of the new study focus on a metric called the “daily severity rating” (DSR), which combines information on maximum temperature, humidity, wind speed and precipitation. Dr Clair Barnes – a research associate at Imperial College London’s Grantham Institute and author on the study – told a press briefing that this metric “indicates how difficult it is likely to be to control the fire once it starts”.
High temperatures and wind speeds, as well as low humidity and rainfall, are very conducive to wildfires spreading and, therefore, produce a high DSR.
The map below shows the average DSR in the Pantanal in June 2024. It reveals that most of the Pantanal was experiencing wildfire risk above the 1990-2020 average over that month.
The weather conditions in the Pantanal in June 2024 were “really unusual for the time of year”, Barnes said.
To investigate how atypical the weather conditions in June 2024 were, the authors analysed temperature, windiness, rainfall and humidity data from the past 45 years.
The chart below depicts annual average rainfall and annual average daily maximum temperature in the Pantanal over 1979-2024. It shows that over the past 45 years, the average temperature in the Pantanal has been steadily increasing and total rainfall has been decreasing.
The authors find that June 2024 was the hottest, least rainy and windiest June since records began. They also find that the relative humidity was the second lowest on record.
Annual rainfall across the Pantanal has been decreasing over the past 40 years, the authors note. They point out that natural variability and deforestation are known to impact rainfall patterns across South America, but add that climate change “may also be influencing the drying trend”.
Attribution
Attribution is a fast-growing field of climate science that aims to identify the “fingerprint” of climate change on extreme-weather events, such as heatwaves and droughts.
To conduct attribution studies, scientists use models to compare the world as it is today to a “counterfactual” world without human-caused climate change. In this study, the authors investigated the impact of climate change on DSR in the Pantanal region.
They find that in today’s climate – which has already warmed by 1.2C as a result of human activity – fire weather conditions like the ones that drove the wildfires in the Brazilian Pantanal during June 2024 are a “relatively rare event”, and would be expected to occur roughly once every 35 years.
However, they say, if the planet continues to warm, these events could become more likely. If the climate warms to 2C above pre-industrial levels, the likelihood of these fire conditions will double compared to today.
The graphic below shows how often June fire weather conditions, such as those seen in the Brazilian Pantanal in June 2024, could be expected under different warming levels.
The square on the left shows a world without climate change, in which these DSR levels would happen once every 161 years. The middle square shows that in today’s climate, the DSR is a one-in-35 year event. And the square on the right shows that in a 2C world, a June DSR like that of 2024 could be expected once every 18 years.
The authors also investigate how climate change affected DSR “intensity”. They find that human-induced warming from burning fossil fuels increased the June 2024 DSR by about 40%.
The authors add that as the climate continues to warm, this trend is likely to worsen. The authors warn that if warming reaches 2C above pre-industrial temperatures, similar June fire weather conditions will become 17% “more impactful”.
(These findings are yet to be published in a peer-reviewed journal. However, the methods used in the analysis have been published in previous attribution studies.)
Fire impacts
Wildfires have wide-ranging impacts on people and nature in the Pantanal. In one example, a 2021 study found that around 17m vertebrates were “killed immediately” by the fires in 2020.
Wildfires can “devastate [the] livelihoods” of people living in the Pantanal and “pose significant health risks” from the resulting smoke, Barbosa says.
She notes that wildfires release CO2 into the atmosphere, contributing to climate change, and they “lead to widespread loss of habitat, endanger wildlife and disrupt ecological balances”. She tells Carbon Brief:
“Species that are already threatened or have limited ranges are particularly vulnerable to habitat destruction caused by fires.
“Repeated fires can push fire-sensitive vegetation into a state of permanent degradation, further threatening the ecological integrity of the region.”
Some fires are permitted for agricultural purposes – such as to burn degraded pasture – during the rainy season, from around November to April. This practice is banned in the drier summer months, but a 2020 piece from Mongabay notes that “in reality, the ban is not always respected and enforcement is haphazard”.
Filippe Santos, a researcher at Portugal’s University of Évora and one of the authors of the study, told a press briefing that “fire is part of the dynamics” of the Pantanal – when it is controlled.
Low-intensity fires allow animals “time to leave” the area, he said, adding:
“What we see with wildfires, is that this does not happen, because the fire is so intense and on such a large scale that animals don’t have time to run away.”
The “highly intense” wildfires also “don’t give nature enough time to recover”, Santos says.
In June, Brazil’s environment minister, Marina Silva, told the government news agency Agencia Brasil that the country is “facing one of the worst situations ever seen in the Pantanal”, adding that the fires are heightened by climate extremes and criminal activities.
Most Pantanal fires are caused by human activity, a 2022 study found. Police in Brazil are investigating the “possible culprits” behind 18 fire outbreaks in the region, Silva said last month.
In recent weeks, a law to improve coordination on tackling fires took effect in Brazil.
A statement from the Institute for Society, Population and Nature, a Brazilian NGO, says this new policy is a “significant milestone” and will establish “guidelines for the practice of integrated fire management across all biomes and territories in the country”.
Barbosa says it will be a “challenge” to implement this policy. She would like to see a “comprehensive national early warning system for multiple hazards to ensure risk reduction” for a range of threats – including wildfires. She tells Carbon Brief:
“Collaboration with local communities, firefighters and brigades is crucial for prevention and response efforts…A coordinated approach that integrates all stakeholders, along with the establishment of a national fund dedicated to fire management, is essential for mitigating the impacts of future fire seasons.”
The post Climate change made the ‘supercharged’ 2024 Pantanal wildfires 40% more intense appeared first on Carbon Brief.
Climate change made the ‘supercharged’ 2024 Pantanal wildfires 40% more intense
Drought and heatwaves occurring together – known as “compound” events – have “surged” across the world since the early 2000s, a new study shows.
Compound drought and heat events (CDHEs) can have devastating effects, creating the ideal conditions for intense wildfires, such as Australia’s “Black Summer” of 2019-20 where bushfires burned 24m hectares and killed 33 people.
The research, published in Science Advances, finds that the increase in CDHEs is predominantly being driven by events that start with a heatwave.
The global area affected by such “heatwave-led” compound events has more than doubled between 1980-2001 and 2002-23, the study says.
The rapid increase in these events over the last 23 years cannot be explained solely by global warming, the authors note.
Since the late 1990s, feedbacks between the land and the atmosphere have become stronger, making heatwaves more likely to trigger drought conditions, they explain.
One of the study authors tells Carbon Brief that societies must pay greater attention to compound events, which can “cause severe impacts on ecosystems, agriculture and society”.
Compound events
CDHEs are extreme weather events where drought and heatwave conditions occur simultaneously – or shortly after each other – in the same region.
These events are often triggered by large-scale weather patterns, such as “blocking” highs, which can produce “prolonged” hot and dry conditions, according to the study.
Prof Sang-Wook Yeh is one of the study authors and a professor at the Ewha Womans University in South Korea. He tells Carbon Brief:
“When heatwaves and droughts occur together, the two hazards reinforce each other through land-atmosphere interactions. This amplifies surface heating and soil moisture deficits, making compound events more intense and damaging than single hazards.”
CDHEs can begin with either a heatwave or a drought.
The sequence of these extremes is important, the study says, as they have different drivers and impacts.
For example, in a CDHE where the heatwave was the precursor, increased direct sunshine causes more moisture loss from soils and plants, leading to a drought.
Conversely, in an event where the drought was the precursor, the lack of soil moisture means that less of the sun’s energy goes into evaporation and more goes into warming the Earth’s surface. This produces favourable conditions for heatwaves.
The study shows that the majority of CDHEs globally start out as a drought.
In recent years, there has been increasing focus on these events due to the devastating impact they have on agriculture, ecosystems and public health.
In Russia in the summer of 2010, a compound drought-heatwave event – and the associated wildfires – caused the death of nearly 55,000 people, the study notes.
The record-breaking Pacific north-west “heat dome” in 2021 triggered extreme drought conditions that caused “significant declines” in wheat yields, as well as in barley, canola and fruit production in British Columbia and Alberta, Canada, says the study.
Increasing events
To assess how CDHEs are changing, the researchers use daily reanalysis data to identify droughts and heatwaves events. (Reanalysis data combines past observations with climate models to create a historical climate record.) Then, using an algorithm, they analyse how these events overlap in both time and space.
The study covers the period from 1980 to 2023 and the world’s land surface, excluding polar regions where CDHEs are rare.
The research finds that the area of land affected by CDHEs has “increased substantially” since the early 2000s.
Heatwave-led events have been the main contributor to this increase, the study says, with their spatial extent rising 110% between 1980-2001 and 2002-23, compared to a 59% increase for drought-led events.
The map below shows the global distribution of CDHEs over 1980-2023. The charts show the percentage of the land surface affected by a heatwave-led CDHE (red) or a drought-led CDHE (yellow) in a given year (left) and relative increase in each CDHE type (right).
The study finds that CDHEs have occurred most frequently in northern South America, the southern US, eastern Europe, central Africa and south Asia.
Threshold passed
The authors explain that the increase in heatwave-led CDHEs is related to rising global temperatures, but that this does not tell the whole story.
In the earlier 22-year period of 1980-2001, the study finds that the spatial extent of heatwave-led CDHEs rises by 1.6% per 1C of global temperature rise. For the more-recent period of 2022-23, this increases “nearly eightfold” to 13.1%.
The change suggests that the rapid increase in the heatwave-led CDHEs occurred after the global average temperature “surpasse[d] a certain temperature threshold”, the paper says.
This threshold is an absolute global average temperature of 14.3C, the authors estimate (based on an 11-year average), which the world passed around the year 2000.
Investigating the recent surge in heatwave-leading CDHEs further, the researchers find a “regime shift” in land-atmosphere dynamics “toward a persistently intensified state after the late 1990s”.
In other words, the way that drier soils drive higher surface temperatures, and vice versa, is becoming stronger, resulting in more heatwave-led compound events.
Daily data
The research has some advantages over other previous studies, Yeh says. For instance, the new work uses daily estimations of CDHEs, compared to monthly data used in past research. This is “important for capturing the detailed occurrence” of these events, says Yeh.
He adds that another advantage of their study is that it distinguishes the sequence of droughts and heatwaves, which allows them to “better understand the differences” in the characteristics of CDHEs.
Dr Meryem Tanarhte is a climate scientist at the University Hassan II in Morocco, and Dr Ruth Cerezo Mota is a climatologist and a researcher at the National Autonomous University of Mexico. Both scientists, who were not involved in the study, agree that the daily estimations give a clearer picture of how CDHEs are changing.
Cerezo-Mota adds that another major contribution of the study is its global focus. She tells Carbon Brief that in some regions, such as Mexico and Africa, there is a lack of studies on CDHEs:
“Not because the events do not occur, but perhaps because [these regions] do not have all the data or the expertise to do so.”
However, she notes that the reanalysis data used by the study does have limitations with how it represents rainfall in some parts of the world.
Compound impacts
The study notes that if CDHEs continue to intensify – particularly events where heatwaves are the precursors – they could drive declining crop productivity, increased wildfire frequency and severe public health crises.
These impacts could be “much more rapid and severe as global warming continues”, Yeh tells Carbon Brief.
Tanarhte notes that these events can be forecasted up to 10 days ahead in many regions. Furthermore, she says, the strongest impacts can be prevented “through preparedness and adaptation”, including through “water management for agriculture, heatwave mitigation measures and wildfire mitigation”.
The study recommends reassessing current risk management strategies for these compound events. It also suggests incorporating the sequences of drought and heatwaves into compound event analysis frameworks “to enhance climate risk management”.
Cerezo-Mota says that it is clear that the world needs to be prepared for the increased occurrence of these events. She tells Carbon Brief:
“These [risk assessments and strategies] need to be carried out at the local level to understand the complexities of each region.”
The post Heatwaves driving recent ‘surge’ in compound drought and heat extremes appeared first on Carbon Brief.
Heatwaves driving recent ‘surge’ in compound drought and heat extremes
Greenhouse Gases
DeBriefed 6 March 2026: Iran energy crisis | China climate plan | Bristol’s ‘pioneering’ wind turbine
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Energy crisis
ENERGY SPIKE: US-Israeli attacks on Iran and subsequent counterattacks across the Middle East have sent energy prices “soaring”, according to Reuters. The newswire reported that the region “accounts for just under a third of global oil production and almost a fifth of gas”. The Guardian noted that shipping traffic through the strait of Hormuz, which normally ferries 20% of the world’s oil, “all but ground to a halt”. The Financial Times reported that attacks by Iran on Middle East energy facilities – notably in Qatar – triggered the “biggest rise in gas prices since Russia’s full-scale invasion of Ukraine”.