Drivers of decadal hiatus periods in the 20th and 21st centuries

The latest generation of climate model simulations are used to investigate the occurrence of hiatus periods in global surface air temperature in the past and under two future warming scenarios. Hiatus periods are identified in three categories: (i) those due to volcanic eruptions, (ii) those associated with negative phases of the Interdecadal Pacific Oscillation (IPO), and (iii) those affected by anthropogenically released aerosols in the mid-twentieth century. The likelihood of future hiatus periods is found to be sensitive to the rate of change of anthropogenic forcing. Under high rates of greenhouse gas emissions there is little chance of a hiatus decade occurring beyond 2030, even in the event of a large volcanic eruption. We further demonstrate that most nonvolcanic hiatuses across Coupled Model Intercomparison Project 5 (CMIP5) models are associated with enhanced cooling in the equatorial Pacific linked to the transition to a negative IPO phase.