Stabilised frequency of extreme positive Indian Ocean Dipole under 1.5 °C warming

• Published in: Nature communications Vol. 9; no. 1; pp. 1419 - 8
• Main Authors: Cai, Wenju, Wang, Guojian, Gan, Bolan, Wu, Lixin, Santoso, Agus, Lin, Xiaopei, Chen, Zhaohui, Jia, Fan, Yamagata, Toshio
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.04.2018; Nature Publishing Group; Nature Portfolio
• Subjects: 704/106/694/2786; 704/829/2737; Agricultural economics; Agricultural ecosystems; Confidence intervals; Dipoles; El Nino; Humanities and Social Sciences; Laboratories; Marine ecosystems; multidisciplinary; Public health; Science; Science (multidisciplinary); Sea level; Statistical analysis; Indian Ocean
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-03789-6

Extreme positive Indian Ocean Dipole (pIOD) affects weather, agriculture, ecosystems, and public health worldwide, particularly when exacerbated by an extreme El Niño. The Paris Agreement aims to limit warming below 2 °C and ideally below 1.5 °C in global mean temperature (GMT), but how extreme pIOD will respond to this target is unclear. Here we show that the frequency increases linearly as the warming proceeds, and doubles at 1.5 °C warming from the pre-industrial level (statistically significant above the 90% confidence level), underscored by a strong intermodel agreement with 11 out of 13 models producing an increase. However, in sharp contrast to a continuous increase in extreme El Niño frequency long after GMT stabilisation, the extreme pIOD frequency peaks as the GMT stabilises. The contrasting response corresponds to a 50% reduction in frequency of an extreme El Niño preceded by an extreme pIOD from that projected under a business-as-usual scenario. It is unclear how extreme positive Indian Ocean Dipole will respond to 1.5 °C of warming. Here the authors show that the frequency of these events increases linearly with warming, doubling at 1.5 °C from the pre-industrial level, but plateaus thereafter.