El Niño and its counterpart La Niña are complex weather phenomena that periodically arise due to fluctuations in ocean temperatures in the Equatorial Pacific. These warm (El Niño) and cold (La Niña) phases shift warm ocean waters eastwards and westwards across the Pacific, respectively. This can bring about changes to weather across the globe, from floods and droughts to heatwaves and cold seasons.
New research, led by scientists from The University of Texas at Austin, suggests that an ancient climate pattern, similar to this one, could make a return to the Indian Ocean due to climate change. This would likely worsen devastating events such as floods, storms, and droughts for populations already vulnerable to the effects of our world’s climate emergency. The periodicity of this El Niño-like pattern could also mean that these extreme weather events become more regular.
Using computer simulations that took into account current climate trends, the researchers found that as global temperatures changed, so too did the surface temperatures across the Indian Ocean. Whilst the ocean’s temperature does currently vary slightly, the fluctuations seen in the simulations were much sharper year to year by 2100, in a similar see-saw fashion seen in the El Niño phenomenon.
“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 Niño,” Pedro DiNezio, a climate scientist at the University of Texas Institute for Geophysics and lead author of the Science Advances study, said in a statement.
In 2019, this weather pattern was found to exist in the Indian Ocean around 21,000 years ago. Microfossils of old foram shells revealed evidence of an ice-age Indian Ocean El Niño when the Earth was cooling. Although we now live in a warming world, how wind and ocean currents are affected by both conditions were found to be similar in simulations.
Conditions over the Indian Ocean are currently kept stable by prevailing winds blowing gently from west to east. However, the simulations showed that the direction of these winds could be reversed by global warming, destabilizing the ocean and reawakening the El Niño-like swings of warming and cooling.
As the evidence continues to suggest the Indian Ocean is capable of much wilder climate patterns, new extremes are looking ever more likely. In particular, disruptions to the monsoons over East Africa and Asia raises significant concern for those reliant on its regular downpours to grow their food.
“If greenhouse gas emissions continue on their current trends, by the end of the century, extreme climate events will hit countries surrounding the Indian Ocean, such as Indonesia, Australia and East Africa with increasing intensity,” Michael McPhaden, a physical oceanographer at the National Oceanic and Atmospheric Administration who was not involved in the study, said. “Many developing countries in this region are at heightened risk to these kinds of extreme events even in the modern climate.”