Unexpected region of the Amazon is experiencing ‘alarming’ rapid growth in climate extremes

An unexpected region of the Amazon is at the forefront of rapid growth in climate extremes, a new report reveals.

The central north Amazon, a region with extensive areas of high forest cover, natural savannas and vast indigenous territories, was not previously considered as being the most affected by climate change.

The report, launched to coincide with COP 30, the first COP to be held in the Amazon, identifies Amazonia as experiencing rapid growth in extreme temperatures and water stress - with 10% of the basin witnessing dry season increases in extreme temperatures of at least 0.77°C a decade and more than 3.31°C since 1981.

The findings reveal that climate extremes in the Amazon have been getting increasingly worse over the last 43 years. These changes are not apparent in assessments of average temperatures, which are rising at 0.21°C a decade and are in line with the global average warming.

Scientists fear that if these rapid increases in incidence of climate extremes continue it could risk pushing the Amazon past critical thresholds.

The discoveries are among the findings of a study led by researchers at Lancaster University and involving an international team of more than 50 scientists, and supported by WWF UK, which sheds new light on climate extremes within the Amazon. Their report provides an up-to-date comprehensive assessment of Amazonia's changing climate across more than four decades and at a high-resolution for the whole biome.

Climate extremes are responsible for some of the most harmful climate-linked impacts on nature and people, driving increased mortality, losses of forest species and damage to ecosystems. In the Amazon, recent exceptionally hot or dry periods have led to extensive forest fires, large-scale animal and tree deaths as well as impacts to human health from heat and air pollution.

By dividing the Amazon into 11km cells and using high resolution temperature and rainfall data from sources that combine information from satellites and local weather stations, the research team was able to identify dry seasons for each individual area of the Amazon.

Using this, as well as a new measure of water deficit that accounts for the effects of temperature on water loss, the researchers modelled temperature changes and water stress across the entire Amazon from 1981 to 2023. Temperature and water deficit were recorded as the averages from across the dry season or the whole hydrological year (dry and wet seasons combined).

The rate of climate change was assessed in two different ways. First, the authors used the central tendency, the most commonly used measure to date which emphasises average rates of temperature and water deficit change across all years. Second, the authors then used extreme tendency, which emphasizes the most exceptional years. This therefore provides a more accurate indication of the changes in the hottest or driest time periods.

"We are most interested in climate extremes in the dry period as that is when the most harm can be caused by high temperatures," said Professor Jos Barlow of Lancaster University and lead author of the report. "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."

The Southern Amazon, which has experienced significant deforestation and land-use change, is confirmed as the fastest warming region when looking at average temperature changes.

However, the central north Amazon is identified as experiencing the most rapid growth in climate extremes.

"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 Dr Nathália Carvalho, post-doctoral research associate at Lancaster Environment Centre. "This is important because we show that Amazonia's climate is not changing uniformly. This information will be crucial when planning and implementing climate change adaptation strategies."

Professor Barlow said: "Extreme climate is a primary concern, contributing to forest fires, exceptional river levels, air pollution and high temperatures that can harm people as well as animals and the forest trees. The rates of change that we are seeing in the most affected regions are very alarming.

"Given the area that is experiencing the fastest growing in extreme temperature is far from the arc of deforestation, these rapid rises cannot be explained by local changes such as deforestation and land-use changes. It's showing how the Amazon is being affected by global climate change. It's the world's emissions that are responsible."

There is evidence from recent studies that climate extremes are impacting the region including the first observed mass death of mammals in the Amazon, where sloths and other mammals were found on the forest floor or hanging dead from understorey trees, reductions in the size of bird populations, and changes to bird lifespans, appearance and behaviour. The region has also experienced extensive forest fires, with extreme heat and drought contributing to air pollution in the Amazon city of Manaus, and drying rivers have affected the health of people living in the forests.

Dr Joice Ferreira, at the Brazilian Agricultural Research Corporation (Embrapa) highlights the social concerns. "Extreme climate events are impacting local livelihoods in many ways, affecting key products like açaí. This removes the safety net that forests provide, threatening food security and weakening their role in a growing socio-bioeconomy. Most concerning, it could derail public policies currently being designed and implemented by Brazilian and state governments to drive positive transformation in the region, such as forest restoration plans. This scenario demands global action to halt climate change in the name of climate justice."

Professor Barlow added: "Adaptation measures are urgently required to address the impacts of these rapidly changing climate extremes, including preventing factors that amplify climate risks such as deforestation. We also need to bring in measures to support the fighting of forest fires as well as supporting local people when the rivers they rely on for navigation dry up."

Dr Mike Barrett, chief scientific adviser at WWF-UK, which supported the research, said: "The rapidly increasing climate extremes revealed in this report highlight the urgent need for COP30 to deliver global action on climate change. However, the new regions of risk also demonstrate the need to support other measures, including an end to deforestation."

The report, 'Rapid increase of climate extremes across northern Amazonia', has been published on the pre-print server EarthArXiv.