Patrick T Brown , Scott Strenfel, Richard B. Bagley, Craig B. Clements

Increasing fuel aridity due to climate warming has and will continue to increase wildfire danger in California. In addition to reducing global greenhouse gas emissions, one of the primary proposals for counteracting this increase in wildfire danger is a widespread expansion of hazardous fuel reductions. Here, we quantify the potential for fuel reduction to reduce wildfire intensity using empirical relationships derived from historical observations using a novel combination of spatiotemporal resolution (0.5km, hourly) and extent (48 million acres, 9 years). We use machine learning to quantify relationships between sixteen environmental conditions (including ten fuel characteristics and four temperature-affected aridity characteristics) and satellite-observed fire radiative power. We use the derived relationships to create fire intensity potential (FIP) maps of sixty historical weather snapshots at a 2km and hourly resolution. We then place these weather snapshots in differing background climatological temperature and fuel characteristic conditions to quantify their independent and combined influence on FIP. We find that in order to offset the effect of climate warming under the SSP2-4.5 emissions scenario, fuel reduction would need to be maintained perpetually on ~3 million acres (at a 5-year return frequency, 600,000 acres, or ~1% of our domain, per year) by 2050 and ~8 million acres (at a 5-year return frequency, 1.6 million acres, or ~3% of our domain, per year) by 2090. Overall, we find substantial potential for fuel reduction to negate the effects of climate warming and that whether or not fuel reduction is scaled up has larger leverage on our domain average FIP than shifting global greenhouse gas emissions from the SSP2-4.5 to the SSP1-2.6 trajectory.