7 February 2024

Climate change is behind record drought in the Amazon Basin


Without climate change, the Amazon Basin would not have experienced the exceptional agricultural drought that has affected the area around the region’s main river, an international study finds

by Matteo Cavallito


The exceptional drought experienced in the Amazon Basin during 2023 would have been caused primarily by the effects of climate change. The phenomenon, in other words, would be linked more to the general rise in temperatures than to the action of El Niño, or the periodic warming of the surface waters of the Central-Southern and Eastern Pacific Ocean during the winter months that occurs on average every five years. This is supported by a study involving researchers from Imperial College London and Universidade Federal do Rio de Janeiro, among others.

“Scientists from Brazil, the Netherlands, the UK and the US used published peer-reviewed methods to assess whether and to what extent the drought has been influenced by climate change as well as the occurrence of El Niño, which is known to be associated with drought in the Amazon,” says a statement released by the World Weather Attribution (WWA), a group of scientists formed to study the incidence of extreme events.

The study

The survey examined the exceptional drought wave that hit the area last year. This phenomenon occurred both on the meteorological front, with low rainfall, and on the agricultural front, with a high incidence of water release from the soil. “The main variable used here to characterise agricultural drought is the Standardised Precipitation Evapotranspiration Index (SPEI) which uses the difference between rainfall and potential evapotranspiration to estimate the available water,” explains World Weather Attribution.

“The more negative the values are, the more severe the drought is classified.”

At the weather level, however, the phenomenon is described by an index known as the Standardized Precipitation Index (SPI) and based only on rainfall. According to scientists, the drought levels observed are absolutely exceptional, to the point of occurring once (weather-wise) or twice (on the agricultural front) in a century.

El Niño? No, it’s the climate

El Niño oscillation certainly helped fuel the phenomenon, the authors explain. But rising temperatures would actually have played a larger role. “El Niño reduced the amount of precipitation in the region by about the same amount as climate change,” the statement explains.

“However, the strong drying trend was almost entirely due to increased global temperatures, so the severity of the drought currently being experienced is largely driven by climate change.”

Combining index analysis with climate models, the scientists showed that the probability of meteorological drought has increased tenfold. At the same time, agricultural drought has become about thirty times more likely.

The effect on the soil is crucial in the Amazon

Last year, a Chinese study published in the journal Science noted how flash drought, or the phenomenon of sudden water shortage, is becoming more frequent on a global scale precisely because of climate change. The intensification of the phenomenon, in detail, would now affect 74 percent of global regions identified by the Special Report on Extreme Events over the past 64 years of the UN Intergovernmental Panel on Climate Change.

Soil interventions, of course, are crucial. As the landmark case of the Amazon shows. “Exposure to drought impacts was compounded by historical land, water, and energy management practices including deforestation, destruction of vegetation, fires, biomass burning, corporate farming, cattle ranching and other socio-climate problems,” the World Weather Attribution says. These events “have decreased the water and moisture retention capacity of the land and thus worsened drought conditions.”