Climate versus carbon dioxide controls on biomass burning: a modelanalysis of the glacial–interglacial contrast

[摘要] Climate controls fire regimes through its influence on the amount and typesof fuel present and their dryness. CO₂ concentration constrainsprimary production by limiting photosynthetic activity in plants. However,although fuel accumulation depends on biomass production, and hence onCO₂ concentration, the quantitative relationship between atmosphericCO₂ concentration and biomass burning is not well understood. Here afire-enabled dynamic global vegetation model (the Land surface Processes andeXchanges model, LPX) is used to attribute glacial–interglacial changes inbiomass burning to an increase in CO₂, which would be expected toincrease primary production and therefore fuel loads even in the absence ofclimate change, vs. climate change effects. Four general circulation modelsprovided last glacial maximum (LGM) climate anomalies – that is, differencesfrom the pre-industrial (PI) control climate – from the PalaeoclimateModelling Intercomparison Project Phase~2, allowing the construction of fourscenarios for LGM climate. Modelled carbon fluxes from biomass burning werecorrected for the model's observed prediction biases in contemporary regionalaverage values for biomes. With LGM climate and low CO₂(185 ppm) effects included, the modelled global flux at the LGM wasin the range of 1.0–1.4 Pg C year^-1, about a third less thanthat modelled for PI time. LGM climate with pre-industrial CO₂(280 ppm) yielded unrealistic results, with global biomass burningfluxes similar to or even greater than in the pre-industrial climate. It isinferred that a substantial part of the increase in biomass burning after theLGM must be attributed to the effect of increasing CO₂ concentrationon primary production and fuel load. Today, by analogy, both risingCO₂ and global warming must be considered as risk factors forincreasing biomass burning. Both effects need to be included in models toproject future fire risks.

[学科分类] 地球化学与岩石