- May 06, 2026
- By Jason P. Dinh
In 2023 and 2024, Earth’s average global surface temperature spiked nearly 0.3 degrees Celsius above what was already expected from climate change. Both years were declared the hottest on record and coincided with deadly wildfires, heat waves and historic numbers of climate-related disasters—but until now, scientists have struggled to explain why.
In a new study published Wednesday in the journal Earth System Dynamics, University of Maryland researchers propose a novel answer: They attribute part of the temperature surge to a climate cycle similar to El Niño known as the Indian Ocean Dipole (IOD).
The researchers built a climate model that predicts global temperatures based on an extensive list of natural and manmade factors. The variables they considered could explain 93% of the global surface temperature anomaly in 2023 and 92% in 2024—the closest scientists have gotten to explaining the record-breaking heat. The IOD was among the most important predictors; when the IOD was omitted, the model’s predictive ability fell dramatically.
The authors say that understanding how such natural factors influence global temperatures will help global decision-makers isolate and potentially mitigate the climate impact of human activity.
“This is probably the most comprehensive attribution that’s out there right now,” said study lead author Endre Farago, who conducted this research as part of his chemistry Ph.D. research at UMD. “Being able to explain 92% to 93% of the anomaly—that’s basically spot on.”
The IOD, sometimes called “Indian Niňo,” refers to the difference in sea surface temperatures in the Indian Ocean’s western and eastern sides. Depending on the year, the western side can be warmer or cooler than the eastern side by varying degrees. This temperature gradient affects everything from rainfall patterns in India to bushfires in Australia.
The IOD was only discovered in the late 1990s and is still not fully understood. And because the Indian Ocean is the smallest of the three major ocean basins, many people didn’t think it could strongly affect the global climate, said study co-author and Atmospheric and Oceanic Science Professor Ross Salawitch.
“There was a view in the climate community that the Pacific Ocean was the dog, and the Indian Ocean was the tail,” said Salawitch, who also holds joint appointments in the Department of Chemistry and Biochemistry and the Earth System Science Interdisciplinary Center.