Projected increase in El Nino-driven tropical cyclone frequency in the Pacific

The El Nio/Southern Oscillation (ENSO) drives substantial variability in tropical cyclone (TC) activity around the world(1-3). However, it remains uncertain how the projected future changes in ENSO under greenhouse warming(4-8) will affect TC activity, apart from an expectation that the overall frequency of TCs is likely to decrease for most ocean basins(9-11). Here we show robust changes in ENSO-driven variability in TC occurrence by the late twenty-first century. In particular, we show that TCs become more frequent (similar to 20-40%) during future-climate El Nino events compared with present-climate El Nino events-and less frequent during future-climate La Nina events-around a group of small island nations (for example, Fiji, Vanuatu, Marshall Islands and Hawaii) in the Pacific. We examine TCs across 20 models from the Coupled Model Intercomparison Project phase 5 database(12), forced under historical and greenhouse warming conditions. The 12 most realistic models identified show a strong consensus on El Nino-driven changes in future-climate large-scale environmental conditions that modulate development of TCs over the off-equatorial western Pacific and the central North Pacific regions. These results have important implications for climate change and adaptation pathways for the vulnerable Pacific island nations.