Climate Change Could Reawaken Indian Ocean El Niño

Smoke from bushfires
New research led by The University of Texas at Austin shows that extreme weather events like Australia’s “Black Summer” of 2019-20 could become more common if global warming reawakens an Indian Ocean El Niño in the future. Credit: Indigo Skies Photography/Flickr

Global warming is approaching a tipping point that during this century could reawaken an ancient climate pattern similar to El Ni.o in the Indian Ocean, new research led by scientists from the University of Texas Institute of Geophysics (UTIG) has found. If it comes to pass, floods, storms and drought are likely to worsen and become more regular, disproportionately affecting populations most vulnerable to climate change.

Sediment and forams under a microscope
Evidence of an ice age Indian Ocean El Niño was found in the chemistry of these 21,000 year old foram shells by Thirumalai in 2017, when he was a postdoctoral fellow at the University of Texas Institute for Geophysics. The researchers now think the processes driving Indian Ocean El Niño during global cooling were very similar to those under global warming. Credit: Kaustubh Thirumalai

Computer simulations of climate change during the second half of the century show that global warming could disturb the Indian Ocean’s surface temperatures, causing them to rise and fall year to year much more steeply than they do today. The seesaw pattern is strikingly similar to El Ni.o, a climate phenomenon that occurs in the Pacific Ocean and affects weather globally. “Our research shows that raising or lowering the average global temperature just a few degrees triggers the Indian Ocean to operate exactly the same as the other tropical oceans, with less uniform surface temperatures across the equator, more variable climate, and with its own El Ni.o,” said lead author Pedro DiNezio, a research scientist at UTIG (now an associate professor at the University of Colorado Boulder).

According to the research, if current warming trends continue, an Indian Ocean El Ni.o could emerge as early as 2050.

The results were published May 6, 2020, in the journal Science Advances. They build on a 2019 paper by many of the same authors that found evidence of a past Indian Ocean El Ni.o hidden in the shells of microscopic sea life, called forams, that lived 21,000 years ago — the peak of the last ice age when the Earth was much cooler.

To show whether an Indian Ocean El Ni.o can occur in a warming world, the scientists analyzed climate simulations, grouping them according to how well they matched present-day observations. When global warming trends were included, the most accurate simulations were those showing an Indian Ocean El Ni.o emerging by 2100.