Nearly all of the increase in summer forest fires in California since 2001 is directly attributable to human-caused climate change

This study delves into the increasing extension of summer forest fires in California, primarily driven by anthropogenic climate change (Turco et al. 2023). Historical data indicate a fivefold increase in summer burned area (BA) in forests in northern and central California from 1996 to 2021 relative to 1971 to 1995. Using the latest simulations developed for climate change attribution and detection studies and accounting for the uncertainties arising from the data-driven climate-fire model, climate models, and internal climate variability, we have investigated the impact of anthropogenic climate change on the observed increase in BA in California’s forests. We detect the signal of combined natural and anthropogenic forcing on the observed BA starting in 2001 while finding the observed BA changes to be inconsistent with internal variability or natural forcing alone. We estimate that climate simulations that included both human and natural forcings yield 172% more BA from 1971 to 2021 than models without anthropogenic forcing, with a remarkable +320% increase from 1996 to 2021. Considering the significance of anthropogenic climate change for the rise in forest BA in California, we pose a crucial question: what will the future of fires look like with ongoing climate changes? Addressing this, we evaluate how fuel limitations resulting from fire-fuel feedbacks might alter future fire trajectories under the influence of anthropogenic climate change. Dynamic models incorporating various feedback strengths suggest an expected further increase in annual average forest BA, ranging from 3 to 52% compared to the mean of the last two decades (2001-2021), which also marks the highest 20-year records since 1971. This highlights the imperative for proactive adaptation strategies. Our findings underscore the urgent need to address the impacts of climate change within fire management and policymaking.