Indonesia's fires quadruple in area as a record El Niño takes hold

According to New Scientist, the fires are slash-and-burn agricultural burns that ran out of control, and the El Niño supplied the dry air that let them spread ^[5]. As a mass of warm water moved from Indonesia toward Peru, the rising air that usually rains out over Indonesian forest shifted to the central Pacific ^[5]. The dry air that would normally sink over East Africa sank over Indonesia instead ^[5]. About 1,000 square kilometres had burned by June ^[1]. Two doublings from July, as the El Niño began forming ^[4], put the total near 4,000 ^[2][1].

The clearest effect so far is in the Atlantic. By the start of October no full hurricane had formed there this year, the first time in more than a century ^[8]. El Niño strengthens the high-level winds over the Atlantic and weakens the low-level ones, and the resulting shear breaks storms up ^[8]. "Those systems are being torn apart as they form," said Nick Dunstone of the UK Met Office ^[9].

Over the Pacific the same change lowers shear. Because the rising air now sits farther east, storms heading for Asia cross more warm water and pick up more heat and moisture before landfall ^[10]. The historical base for what that means is small. Nearly two dozen typhoons hit east Asia in the autumns of the three previous super El Niños ^[11], or seven or eight per event ^[2]. One, super typhoon Koppu, killed at least 47 people in the Philippines in October 2015 ^[12].

This event also sits on 1.4C of global warming, and New Scientist expects a stronger El Niño to bring stronger impacts ^[6]. "There's more moisture in the atmosphere, there's more energy in the system," said Tim Stockdale of the European Centre for Medium-Range Weather Forecasts ^[7]. The thing this doesn't tell you is the size of that extra push: how much worse a given flood or fire gets because the El Niño arrived on a warmer baseline.

Eastern Africa offers a rough comparison. Flooding killed almost 3,000 people there during the 1997 El Niño and 700 during the 2023 one ^[15]. The later toll is about a quarter of the earlier one ^[3]. Two events are not a controlled experiment, but the fall fits the argument made by Ilan Kelman at University College London. "Weather does not have to mean disaster," Kelman said ^[18]. "The reason disasters have happened is because we haven't invested in avoiding disasters," he said ^[18]. Heavy rain and flash floods are forecast next for southern Ethiopia, Kenya and Somalia ^[15].

Much of the outlook is read from what past events did ^[19]. I'd treat Indonesia's fires and the hurricane-free Atlantic as this El Niño already at work, and the months after them as likelihoods drawn from a short record. Next come floods and landslides in the Americas in January and February, and Peru, the country where the phenomenon got its name and was identified, is usually among the hardest hit ^[20]. In early 1998, rainfall turned a desert in Peru into a giant lake ^[20].