A study using seven Earth system models from the Coupled Model Intercomparison Project version 6 (CMIP6) shows that increased atmospheric carbon dioxide (CO₂) concentrations could significantly enhance future fire activity. The multi-model mean percent change in fire carbon emissions is 66.4 ± 38.8% compared to pre-industrial levels, with a substantial increase (60.1 ± 46.9%) attributed to CO₂ biogeochemical effects, such as enhanced vegetation growth. In contrast, CO₂ radiative effects (e.g., warming and drying) have a negligible impact on fire emissions (1.7 ± 9.4%). The study highlights the importance of vegetation dynamics in future fire activity, with potential implications for policy. Fire is a critical Earth system process that alters ecosystems and atmospheric composition. Recent decades have seen increased fire frequency and size in regions like the western US, with projections of further increases due to climate change factors such as drought and heatwaves. Increased atmospheric CO₂ is associated with enhanced carbon uptake and storage by the terrestrial biosphere through the CO₂ fertilization effect. However, the impact of this effect on fire activity is uncertain, as it can both increase fuel load (leading to more fires) and increase live fuel moisture (mitigating fire severity), depending on fire regimes. The study uses CMIP6 models to quantify the impact of an idealized CO₂ increase on fire carbon emissions. The results show a robust increase in fire emissions under CO₂ increases, primarily due to biogeochemical mechanisms. The study also finds that the spatial patterns of fire and vegetation responses are similar, suggesting that increased biomass production (fuel) is a key driver of increased fire activity. Climate responses under CO₂ increases include warming, changes in precipitation, and drying, which can enhance fuel flammability. The study also notes that the biogeochemical effects of CO₂ on vegetation are more significant than the direct climate impacts in driving fire activity. The study concludes that idealized increases in atmospheric CO₂ lead to increased net primary productivity (NPP), implying an enhanced carbon sink by vegetation. However, increased fire carbon emissions can offset this, but in most models, the increase in NPP dominates, resulting in an overall accumulation of vegetation. The study emphasizes the importance of interactions between physical drivers (e.g., heatwaves, droughts) and biotic factors in future fire activity. It also highlights the need to consider ecological drivers in fire risk mitigation policies.A study using seven Earth system models from the Coupled Model Intercomparison Project version 6 (CMIP6) shows that increased atmospheric carbon dioxide (CO₂) concentrations could significantly enhance future fire activity. The multi-model mean percent change in fire carbon emissions is 66.4 ± 38.8% compared to pre-industrial levels, with a substantial increase (60.1 ± 46.9%) attributed to CO₂ biogeochemical effects, such as enhanced vegetation growth. In contrast, CO₂ radiative effects (e.g., warming and drying) have a negligible impact on fire emissions (1.7 ± 9.4%). The study highlights the importance of vegetation dynamics in future fire activity, with potential implications for policy. Fire is a critical Earth system process that alters ecosystems and atmospheric composition. Recent decades have seen increased fire frequency and size in regions like the western US, with projections of further increases due to climate change factors such as drought and heatwaves. Increased atmospheric CO₂ is associated with enhanced carbon uptake and storage by the terrestrial biosphere through the CO₂ fertilization effect. However, the impact of this effect on fire activity is uncertain, as it can both increase fuel load (leading to more fires) and increase live fuel moisture (mitigating fire severity), depending on fire regimes. The study uses CMIP6 models to quantify the impact of an idealized CO₂ increase on fire carbon emissions. The results show a robust increase in fire emissions under CO₂ increases, primarily due to biogeochemical mechanisms. The study also finds that the spatial patterns of fire and vegetation responses are similar, suggesting that increased biomass production (fuel) is a key driver of increased fire activity. Climate responses under CO₂ increases include warming, changes in precipitation, and drying, which can enhance fuel flammability. The study also notes that the biogeochemical effects of CO₂ on vegetation are more significant than the direct climate impacts in driving fire activity. The study concludes that idealized increases in atmospheric CO₂ lead to increased net primary productivity (NPP), implying an enhanced carbon sink by vegetation. However, increased fire carbon emissions can offset this, but in most models, the increase in NPP dominates, resulting in an overall accumulation of vegetation. The study emphasizes the importance of interactions between physical drivers (e.g., heatwaves, droughts) and biotic factors in future fire activity. It also highlights the need to consider ecological drivers in fire risk mitigation policies.