Improving historical trends in the INFERNO fire model using the Human Development Index

Abstract. Earth System Models (ESM), have struggled to reproduce the historical decline in burnt area, with discrepancies largely attributed to the under-representation of anthropogenic fire suppression. Key factors such as agricultural expansion, land-use changes, fire management policies, and landscape fragmentation have all contributed to reduced fire activity, especially in tropical savannas, but these are not adequately captured in the fire model formulation that underpins most ESMs. This study investigates whether the observed downward trend in global burnt area can be better represented in the JULES-INFERNO fire model by incorporating a simplified representation of direct human impacts on fire. Specifically, we focus on the Human Development Index (HDI), which reflects socio-economic development and, in turn, influences fire suppression efforts. By incorporating HDI into INFERNO, we aim to improve the representation of fire ignition and suppression dynamics. Results show that including HDI-driven socio-economic factors reduces biases in annual burnt area, particularly in Temperate North America, Central America, and Europe. While including HDI corrects regional biases, it also introduces a global negative bias as compensating errors at the regional level are addressed. Overall, this approach improves the representation of burnt area trends in eight out of 14 regions, including Southern Hemisphere South America and Northern Hemisphere Africa, where observations show negative trends. Despite mixed results in other fire regions, this study demonstrates that incorporating a socio-economic dimension in INFERNO through HDI provides a simple and effective way to improve fire model performance. It also enhances the ability of ESMs to capture human-environment interactions and offering valuable insights for future climate modelling and fire management strategies.