Abstract
Abstract. Fire is an integral Earth System process that interacts with climate in multiple ways. Here we assessed the parametrization of fires in the Community Land Model (CLM-CN) and improved the ability of the model to reproduce contemporary global patterns of burned areas and fire emissions. In addition to wildfires we extended CLM-CN to account for fires related to deforestation. We compared contemporary fire carbon emissions predicted by the model to satellite-based estimates in terms of magnitude and spatial extent as well as interannual and seasonal variability. Long-term trends during the 20th century were compared with historical estimates. Overall we found the best agreement between simulation and observations for the fire parametrization based on the work by Arora and Boer (2005). We obtained substantial improvement when we explicitly considered human caused ignition and fire suppression as a function of population density. Simulated fire carbon emissions ranged between 2.0 and 2.4 Pg C/year for the period 1997–2004. Regionally the simulations had a low bias over Africa and a high bias over South America when compared to satellite-based products. The net terrestrial carbon source due to land use change for the 1990s was 1.2 Pg C/year with 11% stemming from deforestation fires. During 2000–2004 this flux decreased to 0.85 Pg C/year with a similar relative contribution from deforestation fires. Between 1900 and 1960 we predicted a slight downward trend in global fire emissions caused by reduced fuels as a consequence of wood harvesting and also by increases in fire suppression. The model predicted an upward trend during the last three decades of the 20th century as a result of climate variations and large burning events associated with ENSO-induced drought conditions.
Highlights
Fires occur in all major biomes and influence climate in multiple ways
All simulations in this study were performed with a modified version of the Community Land Model version 3.5 (CLM3.5; Oleson et al, 2008b; Stoeckli et al, 2008) applied with a resolution of 1.9◦×2.5◦
In this study we modified the representation of wildland fires in CLM-CN by a fire algorithm based on the work by Arora and Boer (2005) (CLM-CN-AB), which was developed within the Canadian Terrestrial Ecosystem Model (CTEM) framework (Verseghy et al, 1993)
Summary
Fires occur in all major biomes and influence climate in multiple ways. Fires lead to the emissions of trace gases and aerosols into the atmosphere impacting atmospheric chemistry (Crutzen et al, 1979), atmospheric radiative properties (Penner et al, 1992), and cloud formation (Feingold et al, 2001; Andreae et al, 2004). We used CLM-CN with prescribed dynamic land use datasets (Hurtt et al, 2006) to explicitly account for the fraction of deforestation emissions that occurs through burning This allowed us to compare simulated contemporary fire carbon emissions to satellite-based estimates, that capture both wildfires and deforestation fires. For this study we performed offline CLM-CN simulations for 1798 to 2004 and compared simulated contemporary area burned and fire carbon emissions to satellite-based global fire products (van der Werf et al, 2006; Schultz et al, 2008; Tansey et al, 2008; Mieville et al, 2010).
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