Historical and future fire occurrence (1850 to 2100) simulated in CMIP5 Earth System Models

Earth System Models (ESMs) have recently integrated fire processes in their vegetation model components to account for fire as an important disturbance process for vegetation dynamics and agent in the land carbon cycle. The present study analyses the performance of ESMs that participated in the 5th Coupled Model Intercomparison Project (CMIP5) in simulating historical and future fire occurrence. The global present day (1981 to 2005) burned area simulated in the analysed ESMs ranges between 149 and 208Mha, which is substantially lower than the most recent observation based estimate of 399Mha (GFEDv4s averaged over the time period 1997 to 2015). Simulated global fire carbon emissions, however, are with 2.0PgC/year to 2.7PgC/year on the higher end compared to the GFEDv4s estimate of 2.2PgC/year. Regionally, largest differences are found for Africa. Over the historical period (1850 to 2005) changes in simulated fire carbon emissions range between an increase of +43% and a decrease of −35%. For the future (2005 to 2100) we analysed the CMIP5 simulations following the representative concentration pathways (RCPs) 26, 45, and 85, for which the strongest changes in global fire carbon emissions simulated in the single ESMs amount to +8%, +52% and +58%, respectively. Overall, however, there is little agreement between the single ESMs on how fire occurrence changed over the past or will change in the future. Furthermore, contrasting simulated changes in fire carbon emissions and changes in annual mean precipitation shows no emergent pattern among the different analysed ESMs on the regional or global scale. This indicates differences in the single fire model representations that should be subject of upcoming fire model intercomparison studies. The increasing information derived from observational datasets (charcoal, ice-cores, satellite, inventories) will help to further constrain the trajectories of fire models.