Precipitation and temperature drive many aspects of terrestrial ecosystem function. Climate change scenar-ios predict increasing precipitation variability and temper-ature, and long term experiments are required to evaluate the ecosystem consequences of interannual climate variation, increased growing season (intra-annual) rainfall variability, and warming. We present results from an experiment ap-plying increased growing season rainfall variability and year round warming in native tallgrass prairie. During ten years of study, total growing season rainfall varied 2-fold, and we found ∼50–200 % interannual variability in plant growth and aboveground net primary productivity (ANPP), leaf carbon assimilation (A CO 2), and soil CO 2 efflux (J CO 2) despite only ∼40 % variation in mean volumetric soil water content (0– 15 cm, 15). Interannual variation in soil moisture was thus amplified in most measures of ecosystem response. Dif-ferences between years in 15 explained the greatest por-tion (14–52 %) of the variation in these processes. Exper-imentally increased intra-annual season rainfall variability doubled the amplitude of intra-annual soil moisture varia-tion and reduced 15 by 15 %, causing most ecosystem pro-cesses to decrease 8–40 % in some or all years with increased rainfall variability compared to ambient rainfall timing, sug-gesting reduced ecosystem rainfall use efficiency. Warming treatments increased soil temperature at 5 cm depth, partic-ularly during spring, fall, and winter. Warming advanced canopy green up in spring, increased winter J CO 2 , and re-duced summer J CO 2 and forb ANPP, suggesting that the ef-fects of warming differed in cooler versus warmer parts of the year. We conclude that (1) major ecosystem processes Correspondence to: in this grassland may be substantially altered by predicted changes in interannual climate variability, intra-annual rain-fall variability, and temperature, (2) interannual climate vari-ation was a larger source of variation in ecosystem function than intra-annual rainfall variability and warming, and (3) effects of increased growing season rainfall variability and warming were small, but ecologically important. The relative effects of these climate drivers are likely to vary for different ecosystem processes and in wetter or drier ecosystems.