Climate Change

Climate change made September heat in South America 100 times more likely

Unusual heatwaves hit continent in early spring; WWA study finds temperatures warmer by 1.4-4.3°C due to greenhouse gas emissions

By Akshit Sangomla
Published: Wednesday 11 October 2023
Unusual heatwaves hit South America in early spring this year, following a hotter-than-usual winter season. Photo: iStock_

Global warming and consequent climate change, rather than climate pattern El Nino, were to blame for South America’s untimely and devastating heatwaves and subsequent wildfires. Climate change made the heatwaves at least 100 times more likely and increased the temperatures by 1.4 to 4.3 degrees Celsius, a new rapid attribution study by the World Weather Attribution (WWA) group has found.

WWA is a global consortium of climate scientists who study the role played by human-induced global warming and the consequential climate change in the occurrence, frequency and intensity of extreme weather events such as heatwaves, droughts, cold spells, extreme rainfall, floods and storms.

Unusual heatwaves hit the continent in early spring this year, following a hotter-than-usual winter season and arrived on the heels of unprecedented and record-breaking September heat around the world.

Read more: Over 80% people felt climate change-induced heat in July 2023

The global average temperature in September at 16.38°C was 1.75°C above the pre-industrial (1850-1900) average, the highest on record and breaking the previous record by 0.5°C, according to the World Meteorological Organisation.

“Temperatures exceeded 40°C in Brazil, Bolivia, Argentina and Paraguay, affecting millions of people,” according to a press release by the study authors. The heightened temperatures induced at least 36 wildfires in Bolivia, 20 in Paraguay and several more throughout Brazil.

Though only four deaths have been reported from Sao Paolo, Brazil, the actual impact of the heatwaves can only be known in the months to come after proper assessment.

WWA scientists from Brazil, Argentina, Netherlands, United States and United Kingdom assessed 10-day maximum temperatures throughout the impacted region of South America in August and September.

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From actual temperature observations and climate models, they found the event was a one-in-30-year occurrence in today’s climate. Further, the temperatures during the event would have been 1.4 to 4.3°C cooler if humans had not spewed greenhouse gases into the atmosphere and caused global warming and consequent climate change.

Compared to the impact of climate change, the direct influence of the ongoing El Nino phenomenon in the equatorial Pacific Ocean was small, the scientists added.

During the El Nino phase of the El Nino Southern Oscillation climate phenomenon, warmer than average sea-surface temperatures are observed across the equatorial Pacific Ocean, which generally cause warming in the South American region and disrupt global weather patterns.

“With future global warming, heat events like this will become even more common and hotter. At global mean temperatures of 2°C above pre-industrial levels, a heat event like this would be about another five times more likely and 1.1 to 1.6°C hotter than today,” said the study.

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“Heat kills, particularly in spring, before people are acclimatised to it. Temperatures above 40°C in early spring are incredibly extreme and while we are aware of just four heat-related fatalities, it’s likely the true number is much higher,” said Julie Arrighi, director at the Red Cross Red Crescent Climate Centre, in a press note.

“Unless we take ambitious action to rapidly reduce greenhouse gas emissions, springtime heat will only become more intense, affecting vulnerable people and disrupting ecosystems that are vital for regulating our climate,” said Izidine Pinto, researcher at the Royal Netherlands Meteorological Institute, in a press statement.

“Governments need to invest in weather stations to improve future studies. Having a good local understanding of changing extremes helps people prepare for the future,” said Sjoukje Philip, researcher at the Royal Netherlands Meteorological Institute, in a press release.

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