In the future, climate change will increasingly intensify the pressures of a growing population on the natural ecosystems of California. Even small changes in climate can lead to catastrophic shifts in ecosystems when resilience has been compromised by human exploitation. It is not possible to accurately predict the response of the natural systems to global climate change through direct experimentation, but analyses of the sensitivity of ecosystems can be made using models that integrate information from direct experimentation. MC1, a state-of-the-art dynamic vegetation model, was used in this study to investigate the sensitivity of natural ecosystems in California under several different future climate scenarios. Vegetation is estimated to migrate to higher elevations, which results in reductions in the area covered by alpine meadows and subalpine forests. Higher temperatures and wetter conditions are estimated to result in expansion of conifer and mixed evergreen forests, along with grasslands, at the expense of shrublands, mixed evergreen woodland, and arid land vegetation. Forests tend to shift and expand in northern California, and grasslands expand in southern California. In contrast, drier scenarios result in grassland advancing into the simulated historical range of mixed evergreen woodland and shrubland, even in the central and northern regions of the state. Both wetter and drier scenarios result in increases in carbon storage in California vegetation of between 3% and 6%. The wetter scenarios result in increases of total ecosystem carbon, but much larger increases in carbon stored in vegetation. The dry scenarios also result in increases in total carbon storage, but most of the increase is in soils and litter. The results suggest that changes in fire and shifts in the relative dominance of woody and grass lifeforms could buffer the effect of different climatic perturbations on total ecosystem carbon storage. Under a wetter climate, an increase in carbon storage with the increase in vegetation productivity could be limited by greater losses to combustion during more extreme fire events. Under a drier climate, a decrease in carbon storage with the decrease in vegetation productivity could be limited by a shift towards greater dominance of grass lifeforms which are better-adapted to more frequent fire and more effective contributors to soil carbon stocks. Climate change will also affect the frequency and size of fires, with most of the scenarios resulting in increased fires. Under warmer and drier scenarios, the results suggest that total annual area burned will increase, but fire intensity will decline with the expansion of vegetation comprised of lighter fuel loads (e.g., grassland). The wetter scenarios result in fires larger than those seen in the simulated historical record because increases in biomass set the stage for larger and more intense fires during less frequent dry years. Interannual variation in total area burned declined under the drier scenarios. In contrast, under warmer and wetter scenarios, there was greater year-to-year variability in area burned. Depending on the climate scenario, fire business may become more or less predictable, fuels may increase or decline, and fire behavior may become more or less difficult to control.