As the climate phenomenon known as El Niño began to crank up the global thermostat last year, South America felt the heat.
A series of searing temperature spikes hit Brazil. In November, a 23-year-old woman passed out at a Taylor Swift concert in Rio de Janeiro and subsequently died of heat exhaustion. A severe drought hit the Amazon basin, while in Bolivia, authorities in July declared a drought alert for Lake Titicaca, an 8,300-square-kilometre freshwater lake that sits high in the Andes Mountains. Scores of river dolphins washed up dead on the shores of Lake Tefé in Brazil, with researchers pointing to soaring water temperatures as the likely cause of their demise.
And that all happened in spring in the Southern Hemisphere.
“This is not the worst of it, we still have three months of summer to go through,” Anabela Bonada, manager and research associate at the Intact Centre on Climate Adaptation at the University of Waterloo, said in December. “So I don’t think we have seen yet the real repercussions of El Niño like we’re going to start to see it in the next few months. And I do think it will be quite complicated for South America.”
A Peruvian navy research ship deploys an El Niño monitoring buoy in the Pacific Ocean off Tumbes, near Peru's border with Ecuador, this past November.Supplied by ANDINA/AFP via Getty Images
El Niño is part of a broader climate pattern known as the El Niño-Southern Oscillation (ENSO), a recurring phenomenon driven by fluctuating ocean temperatures and trade winds. El Niño is the warm phase of the cycle and occurs, on average, every two to seven years.
El Niño periods typically bring warmer temperatures around the world. It also aligns with regional patterns, such as drier conditions in Northern Brazil and heavy rainfall for coastal regions of Ecuador and Peru. The World Meteorological Organization made its official announcement on July 4, 2023, saying El Niño conditions had developed in the tropical Pacific for the first time in seven years, “setting the stage for a likely surge in global temperatures.”
A sweltering summer in the Northern Hemisphere followed, with heat waves in Europe, China and the United States and an unprecedented wildfire season in Canada.
In November, the WMO said the current El Niño event is expected to last at least until April, 2024.
In Canada, that prediction played out with one of the warmest Decembers on record. How high those spikes might get as summer unfolds in the Southern Hemisphere remains to be seen. Another uncertainty is how El Niño will be affected by human-driven climate change. Climate researchers have been puzzling over that question for decades, but the issue is complex, in part because limited data make it difficult to get a comprehensive picture of past El Niño events.
In general, though, researchers expect warmer global temperatures to amplify ENSO effects such as droughts, heat waves and wildfires.
As 2023 emerged as the warmest year on record, the U.S. Climate Prediction Center in December said forecasts indicated a “historically strong” El Niño during the November-January season, noting an event of that strength could be in the top five of El Niño events since 1950.
Regina Rodrigues is a professor and climate researcher at the Federal University of Santa Catarina in Southern Brazil. In posts on the social-media site X in December, she said El Niño effects exacerbated by climate change were already hitting South America.
She cited a string of heat waves in Brazil that covered wide swaths of the country and lasted for days or weeks at a time.
“So not only are those heat waves more widespread compared to past El Niño events, but they are also much more recurrent and intense,” Dr. Rodrigues said.
Here are some areas in South America where El Niño is either already having an impact or could play a role in coming months.
Too little water
In 2023, the dry season in the Amazon led to an unprecedented drought, with water levels in the Rio Negro, in the rain forest near Manaus, diminishing to a depth of just 12.7 metres – the lowest recorded in 120 years.
The region’s worst droughts and most devastating fire seasons are usually linked to El Niño, according to the U.S. National Oceanic and Atmospheric Administration. Both of the two previous record-low stream flows in Rio Negro – 1963 and 2010 – also happened during El Niño events.
Too much water
In South America, El Niño events typically cause drought in the Amazon and northeastern parts of the continent, paired with flooding in the tropical west coast and southeastern regions. Those weather patterns can correspond with devastating health and economic effects, exacerbated by poverty, inflation or social unrest.
Brazil has been hit by a series of storms since this past June, including a September cyclone that left dozens of people dead. In certain areas, river levels surged to 17 metres above average, according to a September report from the UN Office for the Coordination of Humanitarian Affairs. Flooding also hit Paraguay, where government officials cited El Niño as a factor in the emergency.
Too hot for human health
Extreme heat during August and September affected millions of people across Argentina, Brazil, Paraguay and Bolivia, said a study released in October by World Weather Attribution, an international initiative that studies how climate change contributes to events such as drought and heat waves. While ENSO may have influenced those weather patterns, climate change was the main driver, according to the WWA report.
The effects of heat on human health are compounded by poverty, which can make it harder or impossible to access cooler surroundings and is a feature in many parts of South America expected to grapple with extreme heat in coming months.
Too hot for wildlife
Because of warmer ocean temperatures, El Niño can have significant effects on fisheries and migratory seabirds.
Marine mammals can also be affected. In 2023, more than 100 river dolphins washed up dead on the shores of Lake Tefé in Brazil, highlighting the devastating drought gripping the Amazon. In an October bulletin, WWF-Brazil said analyses to date indicate river dolphin mortality is related to “climate change, the effects of El Niño and extreme drought.”
From grasslands to desert
At about two million square kilometres, the cerrado is the most biodiverse tropical savanna in the world, according to the 2022 Global Land Outlook, a UN report. In recent decades, about half of the cerrado’s native vegetation has been destroyed by mining, cattle ranching, soy, cotton and other agribusiness concerns, the report says. If El Niño brings higher temperatures and drought, that area may be further endangered.
From forests to ashes
Higher temperatures and drought also fuel wildfires. In 2023, wildfires burned in Argentina, Paraguay and Bolivia. For days in October and November, smoke shrouded Manaus, the capital of the Amazonas state in Northwestern Brazil, giving it some of the worst air quality in the world.
Last February, wildfires in Chile killed at least a dozen people and displaced hundreds more. Those fires occurred during a summer heat wave and before El Niño made its official entrance. With summer and El Niño now both in play, the picture of how they may interact is coming into clearer focus.
Wendy Stueck