California Institute for Energy and Environment (CIEE)

We examine a macro-scaled perspective of fire and climate for California and highlight landscapes where sensitivity and exposure to climate change has the potential to induce alteration of future fire activity. This research presents just one method of proposing a future of fire and includes many caveats and assumptions. Using statistical models, we relate the probability of burning in 1080-m landscapes over a 30-year baseline period of 1971–2000 to climate variables for the same period. These climate variables aim to represent spatial variation in vegetation growth conditions and the seasonal dryness necessary for burning. A metric of distance to human development is used to examine human influence on fire activity via ignition and/or suppression. We quantify how the risk of relatively long-term tendency for burning might change with climate over the next 100 years based on projections from two Global Climate Models and two emissions scenarios. Model outcomes suggest varying degrees of increased future fire activity in more productive regions of California however by 2070–2099, the two GCMs selected for the study disagree in the polarity in response for drier, less productive regions. The second component of this study is retrospective. We test the temporal transferability of baseline models by back-casting using 1971–2000 model parameters but incorporating climate and development data from 1941–1970. These baseline back-casts were compared against model outcomes developed using data from the 30-year period from 1941–1970. Though fire records from before 1950 were not kept as reliably as in more recent periods, this method helps to understand how well projections of future fire might reflect actual future events. Baseline models are then also used with observed climate records for periods 1911–1940, which allows us to consider differences among future projections of fire and climate in the context of the range estimated for the last century.