El Niño is one of the most familiar climate patterns on Earth. Pools of water in the eastern tropical Pacific Ocean become abnormal warm, triggering changes in global weather patterns.

Thanks to the climate crisis, El Niño may have some competition. A new study published in Science Advances on Wednesday shows that as early as mid-century, global warming could cause an ancient climate pattern similar to El Niño in the Indian Ocean to reawaken. It would throw weather further into disarray, particularly in places in the global south that depend on rainfed agriculture.

The study builds on a previous one published by some of the same authors last year, which found that this climate pattern in the Indian Ocean may have existed during the last Ice Age, 20,000 years ago. Back then, thanks to…