Over 21,000 future California residentialwildfire risk scenarios were developed on amonthly 1/8° grid, using statisticalwildfire models.We explore interactions between two global emissions scenarios, three climate models, six spatially explicit population growth scenarios derived from two growth models, and a range of parameters defining properties' vulnerability to loss. Scenarios are evaluated over two future time periods relative to historic baselines.We also explore effects of spatial resolutions for calculating household exposure to wildfire on changes in estimated future property losses. Our goal was not to produce one authoritative set of future risk scenarios but rather to understand what parameters are important for robustly characterizing effects of climate and growth on future residential property risks. By end of century, variation across development scenarios accounts for far more variability in statewide residential wildfire risks than does variation across climate scenarios. However, the most extreme increases in residential fire risks result from combining high-growth/high-sprawl scenarios with the most extreme climates considered here. Case studies for the Bay Area and the Sierra foothills demonstrate that, while land use decisions profoundly influence future residential wildfire risks, effects of diverse growth and land use strategies vary greatly around the state.

Changing climatic conditions are influencing large wildfire frequency, a globally widespread disturbance that affects both human and natural systems. Understanding how climate change, population growth, and development patterns will affect the area burned by and emissions from wildfires and how populations will in turn be exposed to emissions is critical for climate change adaptation and mitigation planning. We quantified the effects of a range of population growth and development patterns in California on emission projections from large wildfires under six future climate scenarios. Here we show that end-of-century wildfire emissions are projected to increase by 19-101% (median increase 56%) above the baseline period (1961-1990) in California for a medium-high temperature scenario, with the largest emissions increases concentrated in northern California. In contrast to other measures of wildfire impacts previously studied (e.g., structural loss), projected population growth and development patterns are unlikely to substantially influence the amount of projected statewide wildfire emissions. However, increases in wildfire emissions due to climate change may have detrimental impacts on air quality and, combined with a growing population, may result in increased population exposure to unhealthy air pollutants.