Study finds oceanic climate pattern brought historic heat

(CN) — As the summer months draw near and temperatures continue to rise, a group of researchers recently found evidence that an Indian Ocean climate phenomenon is the driving force behind a streak of increasing global temperatures.

Both 2023 and 2024 set new records for global heat, accompanied by devastating wildfires, severe heat waves and an unprecedented number of climate-related disasters that exceeded predictions based on climate change.

A team of researchers from the University of Maryland decided to tackle the question of what’s causing the spike in a new study released Wednesday in the journal Earth System Dynamics. They proposed that the Indian Ocean Dipole, a climate cycle also known as the Indian Niño, is a contributing factor in temperature surges.

The team worked together to build a climate model that forecasts global temperatures by accounting for a comprehensive range of variables, including natural and human-induced factors.

Their analysis revealed the variables in their model accounted for 93% of the global surface temperature anomaly in 2023 — which was one of the two most powerful recorded Indian Niño events in modern history — and 92% in 2024. The oceanic climate pattern was found to be a predominant factor — without it, the model only accounted for 69% of the 2023 temperature spike and 77% of the 2024 spike.

“This is probably the most comprehensive attribution that’s out there right now,” Endre Farago, the study’s lead author, said in a press release. “Being able to explain 92% to 93% of the anomaly — that’s basically spot on.”

The Indian Niňo was discovered in the late 1990s and refers to fluctuations in sea surface temperatures across the western and eastern Indian Ocean. In some years, the western side of the divide grows significantly warmer or cooler than the eastern side, which can dramatically influence regional weather, altering rainfall patterns in India and fueling wildfires in Australia.

Despite being discovered nearly 30 years ago, much about the Indian Niño remains unclear — until the last decade, scientists discussed whether it was a distinct climate cycle or merely a result of the more familiar El Niño Southern Oscillation, or ENSO, in the Pacific Ocean. In a press release, Ross Salawitch, the study’s co-author and a professor at the University of Maryland, said that because the Indian Ocean is smaller than the two other major ocean basins, many researchers believed its effect on the global climate was minimal.

“There was a view in the climate community that the Pacific Ocean was the dog, and the Indian Ocean was the tail,” Salawitch said.

Salawitch added that he became convinced of the Indian Niño’s more significant impact after reviewing the model’s results, which revealed close links between the climate cycle and unusual warming patterns in South America and southern Australia during 2023. The model’s accuracy dropped significantly when the Indian Niño was excluded.

The team found that other forces driving the streak of increasing global temperatures stemmed from human activity and other natural cycles, including high sea surface temperatures in the North Atlantic Ocean and an ENSO event in the Pacific Ocean.

Salawitch called on his colleagues to include the Indian Niño in future global warming attribution studies.

“It’s our hope that they’ll find some importance and truth — some veritas — to what we did and what we found,” Salawitch said. “Doing so will hopefully lead to better quantification of the various natural and human factors that drive global warming, with meaningful implications for future policies to address climate change.”