Climate change made unprecedented Amazon rainforest drought 30 times more likely

Human-caused climate change was the main driver of last year's devastating drought in the Amazon, according to a study by World Weather Attribution.

The rapid attribution analysis found that climate change made the devastating drought from June to November last year 30 times more likely.  

While El Niño, a natural climate phenomenon that usually brings dry conditions to the region was widely blamed for the event, researchers from the World Weather Attribution (WWA) found that climate change had a much greater influence. 

Dr Friederike Otto, Senior Lecturer in Climate Science at Grantham Institute - Climate Change and the Environment, Imperial College London and the co-founder of  WWA, said:  

“This result is very worrying. Climate change and deforestation is already wrecking parts of the most important ecosystems in the world. 

“If we continue burning oil, gas and coal, very soon, we’ll reach 2°C of warming and we’ll see similar Amazon droughts about once every 13 years

“Our choices in the battle against climate change remain the same in 2024 – continue to destroy lives and livelihoods by burning fossil fuels, or secure a healthy, liveable future by rapidly replacing them with clean renewable energy.”

An unprecedented event 

Although the Amazon is regularly affected by drought, this is the first recorded drought affecting the entire Amazon Basin at one time, leading to devastating human consequences.   

Amazon rivers fell to their lowest levels in 120 years and many waterways were too shallow for boats, leading to a more than 60% reduction in the transport of essential goods  in the region. 

Simphiwe Stewart, Technical Advisor at the Red Cross Red Crescent Climate Centre and an author of the study, noted:  

“Many communities living in the Amazon River Basin simply haven’t seen a drought like this before.

“Waterways dried up in a matter of months. People were forced to make huge journeys, dragging boats over dried up sections of river, to access food, medicine and other essential goods.” 

Record low water levels led to power cuts in many countries reliant on rivers for generating hydroelectricity, which makes up 80% of electricity in Brazil, 79% in Colombia, 68% in Venezuela, 55% in Ecuador and Peru. 

Additionally, high water temperatures have been linked to a massive die-off of river life, including at least 170 endangered pink river dolphins since September, while hot and dry conditions drove the spread of wildfires, which destroyed millions of acres of rainforest and caused dangerous air quality in Manaus, Brazil - home to more than two million people.   

Untangling drivers of drought 

To understand the influence of climate change on the Amazon drought, WWA scientists analysed weather data and model simulations to compare the climate as it is today with the 1.2°C cooler pre-industrial climate. 

The analysis looked at two key drivers of drought – low rainfall and evapotranspiration, the evaporation of water from plants and soils driven by high temperatures.  

The researchers found that El Niño and climate change had an equal influence on the very low rainfall. However, the increase in high temperatures was driven almost entirely by climate change.  

Ben Clarke, Researcher at Grantham Institute - Climate Change and the Environment, Imperial College London and the lead author of the study, said:  

“As the Amazon drought worsened in 2023, many people pointed to El Niño to explain the event. While El Niño did lead to even lower levels of rainfall, our study shows that climate change is the main driver of the drought through its influence on higher temperatures.” 

“With every fraction of a degree of warming caused by the burning of fossil fuels, the risk of drought in the Amazon will continue to increase, regardless of El Niño.” 

If global warming reaches 2°C, periods of extremely low rainfall will become another four times more likely, expected to occur about once every 33 years, while agricultural droughts driven by both low rainfall and high temperatures will become another three times more likely, expected to occur about once every 13 years.  

The finding reflects a growing understanding about the relationship between climate change and drought, particularly the crucial role of heat.  

In November 2023, WWA published a study on a devastating two-and-a-half-year drought that impacted Syria, Iran and Iraq.  

The researchers found that while rainfall did not show clear signs of being influenced by climate change, the extreme heat driven by climate change increased evaporation from soil and plants, making the drought about 25 times more likely in Syria and Iraq, and 16 times more likely in Iran.  

'Lungs of the earth'

The Amazon is the largest rainforest in the world and a global hotspot of biodiversity, home to more than 10% of all known species on earth.  

It is also the most important land-based carbon sink, often referred to as the ‘lungs of the earth,’ because it absorbs huge amounts of carbon dioxide and replaces it with oxygen.   

“The Amazon could make or break our fight against climate change. If we protect the forest, it will continue to act as the world’s largest land-based carbon sink."  Regina Rodrigues, Professor of Physical Oceanography and Climate, Federal University of Santa Catarina

The combined effects of deforestation and climate change are pushing the Amazon rainforest  toward a drier state, threatening massive tree dieback that could release large amounts of carbon dioxide into the atmosphere, further warming the planet. 

Regina Rodrigues, Professor of Physical Oceanography and Climate, Federal University of Santa Catarina and one of the authors of the study, said:  

“The Amazon could make or break our fight against climate change. If we protect the forest, it will continue to act as the world’s largest land-based carbon sink.  

But if we allow human-induced emissions and deforestation to push it through the tipping point, it will release large amounts of carbon dioxide, further complicating our fight against climate change. 

“To protect the health of the Amazon, we need to protect the rainforest and move away from fossil fuels as quickly as possible.” 

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'Climate change, not El Niño, main driver of exceptional drought in highly vulnerable Amazon River Basin' is published at World Weather Attribution.