Volcanic activity plays a strong role in modulating climatevariability. Most model projections of the twenty-first century,however, under-sample future volcanic effects by not repre-senting the range of plausible eruption scenarios. Here,we explore how sixty possible volcanic futures, consistentwith ice-core records5, impact climate variability projections ofthe Norwegian Earth System Model (NorESM)under RCP4.(ref. 7). The inclusion of volcanic forcing enhances climatevariability on annual-to-decadal timescales. Although decades with negative global temperature trends become∼50%more commonplace with volcanic activity, these are unlikely to be able to mitigate long-term anthropogenic warming.Volcanic activity also impacts probabilistic projections of global radiation, sea level, ocean circulation, and sea-icevariability, the local-scale effects of which are detectable when quantifying the time of emergence. These results highlight theimportance and feasibility of representing volcanic uncertaintyin future climate assessments.