Quantifying the role of fire in the Earth system – Part 1: Improved global fire modeling in the Community Earth System Model (CESM1)

Abstract

Abstract. Modeling fire as an integral part of an Earth system model (ESM) is vital for quantifying and understanding fire–climate–vegetation interactions on a global scale and from an Earth system perspective. In this study, we introduce to the Community Earth System Model (CESM) the new global fire parameterization proposed by Li et al. (2012a, b), now with a more realistic representation of the anthropogenic impacts on fires, with a parameterization of peat fires, and with other minor modifications. The improved representation of the anthropogenic dimension includes the first attempt to parameterize agricultural fires, the economic influence on fire occurrence, and the socioeconomic influence on fire spread in a global fire model – also an alternative scheme for deforestation fires. The global fire parameterization has been tested in CESM1's land component model CLM4 in a 1850–2004 transient simulation, and evaluated against the satellite-based Global Fire Emission Database version 3 (GFED3) for 1997–2004. The simulated 1997–2004 average global totals for the burned area and fire carbon emissions in the new fire scheme are 338 Mha yr−1 and 2.1 Pg C yr−1. Its simulations on multi-year average burned area, fire seasonality, fire interannual variability, and fire carbon emissions are reasonable, and show better agreement with GFED3 than the current fire scheme in CESM1 and modified CTEM-FIRE. Moreover, the new fire scheme also estimates the contributions of global fire carbon emissions from different sources. During 1997–2004, the contributions are 8% from agricultural biomass burning, 24% from tropical deforestation and degradation fires, 6% from global peat fires (3.8% from tropical peat fires), and 62% from other fires, which are close to previous assessments based on satellite data, government statistics, or other information sources. In addition, we investigate the importance of direct anthropogenic influence (anthropogenic ignitions and fire suppression) on global fire regimes during 1850–2004, using CESM1 with the new fire scheme. Results show that the direct anthropogenic impact is the main driver for the long-term trend of global burned area, but hardly contributes to the long-term trend of the global total of fire carbon emissions.

Fire Research: Linking Past, Present, and Future Data

“…Incorporating anthropogenic influences into fire models demonstrates that 8% of global fire carbon emission contributions (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004) are from deliberate agricultural biomass burning and 24% are from deforestation [Li et al, 2013].…”

A fire model with distinct crop, pasture, and non-agricultural burning: Use of new data and a model-fitting algorithm for FINALv1

“…9); that is, no fire can occur (f T = 0) at or below T lo and temperature does not limit fire (f T = 1) at or above T up . After Li et al (2013), we set T lo to -10…”

“…25 Li et al (2013) also included a suppressive effect of per-capita gross domestic product (GDP) on number of fires. This was based on the idea that relatively wealthy parts of the world might have more valuable property to protect and a better capacity for suppression than less developed regions.…”

“…First, although globally gridded maps of GDP exist for the past 25 years or so (van Vuuren et al, 2007), no existing data sets describe the distribution of economic status before 1990. Second, the functions elaborated by Li et al (2013) are somewhat ad-hoc, not 30 taking into account other variables that might be responsible for the observed relationships. Bistinas et al (2014), for example,…”

“…After Li et al (2012), we set fire duration (d, seconds) to 24 hours (86,400 s). Li et al (2013) also include functions that reduce burned area per fire based on population density and GDP per capita.…”