An area of more than 700,000 km² in the central-northern Amazon, nearly the size of Chile, has seen extreme dry-season temperatures rise by at least 3.2 °C since 1981. The figure comes from the study "Rapid increase of climate extremes reveals new areas of concern in Amazonia", published on Thursday in Communications Earth & Environment, a Nature Portfolio journal, and signed by 53 scientists from several countries, including Brazilians and experts from the Science Panel for the Amazon. The team is led by Lancaster University in the United Kingdom, in partnership with WWF.
In the affected region, one of the best-preserved parts of the basin, warming advanced at a rate of at least 0.75 °C per decade, more than three times the pace of the forest's average annual temperature, about 0.21 °C per decade over the past four decades. To measure the change, the researchers divided the entire basin into 11 km grid cells and analysed high-resolution temperature and rainfall data from 1981 to 2023. Across the forest as a whole, the 95th percentile of maximum temperatures in the driest period rose 0.49 °C per decade, according to the paper's abstract. During the dry season, 10% of the basin already faces increases in extreme heat of at least 0.75 °C per decade.
An uneven shift in the forest
The southern Amazon remains the fastest-warming part of the biome on average. It is in the centre-north, however, far from the "arc of deforestation", the farming frontier pushing into the forest's southern and eastern edges in states such as Pará and Mato Grosso, that extreme heat and water deficit are growing fastest. The affected area holds intact forest, natural savannas and Indigenous territories, and had therefore been treated as one of the Amazon's most resilient zones. According to reporting by Luciana Constantino of Agência Fapesp published in Folha de S.Paulo, the result indicates the phenomenon stems both from forest loss, Brazil's main source of greenhouse gas emissions, and from global climate change. "The rates of change in climate extremes are much higher than the rates of change of average climate in the Amazon, and the most affected regions are also different for extremes and average climate," said Nathália Carvalho, a postdoctoral researcher at the Lancaster Environment Centre, in a statement. Lead author Jos Barlow, a professor at Lancaster University, explained the scope of the analysis:
"We are most interested in things when they are at their hottest and driest as that is when the most harm can be caused by high temperatures. While this has been assessed in the Southern Amazon, which shares a largely similar dry season, it has never been assessed across the whole of the Amazon, which includes regions north of the equator which have a different dry season period."
In recent years, hot and dry extremes in the Amazon have brought unprecedented fires, large-scale tree mortality and localised animal deaths, including mass die-offs of river dolphins, along with shrinking bird populations, according to the paper and WWF. The immediate concern is this year's El Niño, expected to be the strongest on record, which could again expose the forest to extreme heat and drought two years after the major drought of 2024, Folha reported.
Measures and funding
The study calls for rapid cuts in global greenhouse gas emissions, fire prevention, an end to deforestation and forest degradation, and greater investment in adaptation. About 17% of the forest has already been cleared, and the 2025 Global Tipping Points Report, produced with WWF involvement, estimates that a loss of between 20% and 25% could be enough to trigger a transformation of the biome into a degraded state. On 3 September, the UK government announced a commitment to the Tropical Forest Forever Facility (TFFF), an international mechanism created to fund conservation and adaptation in tropical forests.
"The rapidly increasing climate extremes revealed in this study highlight the urgent need for global action on climate change to protect vital ecosystems such as the Amazon. However, the new regions of risk also demonstrate the need to support other measures, including an end to deforestation and support for measures such as the Tropical Forest Forever Facility if we are to avoid critical tipping points and environmental collapse."
The statement came from Mike Barrett, chief scientific adviser at WWF-UK. In the organisation's view, the British commitment to the TFFF announced last week is timely and now needs to be backed by measures removing deforestation-linked commodities from UK supply chains.