Projected Changes to Characteristics of El Niño‐Southern Oscillation, Indian Ocean Dipole, and Southern Annular Mode Events in the CMIP6 Models

In this study we analyse projections of future changes to the El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Southern Annular Mode (SAM) using the latest generation of climate models. Multiple future scenarios are considered. We quantify the fraction of models that project future increases or decreases in the frequency and amplitude of ENSO, IOD, and SAM events in the late 21st century. Changes to the frequency of co‐occurring and consecutive driver phases are also examined. We find that while there is large inter‐model spread, the most common pathways correspond to more frequent ENSO events; weaker, less frequent IOD events; and stronger, but less frequent austral spring SAM events. There is no clear consensus on the change to the frequency of concurrent events, though we find a significant increase in La Niña‐ and El Niño‐only events occurring with neutral IOD and SAM. We also find a significant increase to the frequency of consecutive positive IOD events under a high emissions scenario, but no significant change to the frequency of consecutive ENSO or negative IOD events. In most models, the correlation between drivers, that is, ENSO and IOD, and ENSO and SAM, does not significantly change between the late 20th and late 21st century. These results indicate a high degree of internal variability in the models. Plain Language Summary Year‐to‐year climate variability impacts ecosystems and billions of people around the world. Major drivers of this variability in the Southern Hemisphere include the El Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Southern Annular Mode (SAM). As anthropogenic activities continue to impact the climate, and further change is inevitable, we need to improve understanding of how these climate drivers will change. Here we use the latest generation of climate models to investigate how the strength and frequency of these three climate drivers are projected to change over the remainder of the 21st century. We investigate changes to these drivers individually, as well as changes to the frequency of these drivers occurring simultaneously or consecutively. While there is still a large amount of inter‐model spread, the most common model projections are: more frequent ENSO events; weaker and less frequent IOD events; and stronger, but less frequent SAM events. A statistically significant increase in the frequency of consecutive positive IOD events in the high emissions scenario is also found.