Abstract
Abstract. Fires have influenced atmospheric composition and climate since the rise of vascular plants, and satellite data have shown the overall global extent of fires. Our knowledge of historic fire emissions has progressively improved over the past decades due mostly to the development of new proxies and the improvement of fire models. Currently, there is a suite of proxies including sedimentary charcoal records, measurements of fire-emitted trace gases and black carbon stored in ice and firn, and visibility observations. These proxies provide opportunities to extrapolate emission estimates back in time based on satellite data starting in 1997, but each proxy has strengths and weaknesses regarding, for example, the spatial and temporal extents over which they are representative. We developed a new historic biomass burning emissions dataset starting in 1750 that merges the satellite record with several existing proxies and uses the average of six models from the Fire Model Intercomparison Project (FireMIP) protocol to estimate emissions when the available proxies had limited coverage. According to our approach, global biomass burning emissions were relatively constant, with 10-year averages varying between 1.8 and 2.3 Pg C yr−1. Carbon emissions increased only slightly over the full time period and peaked during the 1990s after which they decreased gradually. There is substantial uncertainty in these estimates, and patterns varied depending on choices regarding data representation, especially on regional scales. The observed pattern in fire carbon emissions is for a large part driven by African fires, which accounted for 58 % of global fire carbon emissions. African fire emissions declined since about 1950 due to conversion of savanna to cropland, and this decrease is partially compensated for by increasing emissions in deforestation zones of South America and Asia. These global fire emission estimates are mostly suited for global analyses and will be used in the Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations.
Highlights
Fire is one of the most important disturbance agents in terrestrial ecosystems on a global scale, occurring in all major biomes of the world, and emitting roughly 2–3 Pg C yr−1, mostly in the form of CO2, and substantial amounts of reduced species and aerosols (Andreae and Merlet, 2001; van der Werf et al, 2010)
Africa accounts for a large part of global fire carbon emissions and the general trend largely mimics that of Africa
In Africa, the continent from which half of all carbon emissions stems, we found that emissions were relatively flat while CMIP5 estimates increased over the past decades, at odds with recent findings that agricultural expansion lowers fire activity (Andela and van der Werf, 2014)
Summary
Fire is one of the most important disturbance agents in terrestrial ecosystems on a global scale, occurring in all major biomes of the world, and emitting roughly 2–3 Pg C yr−1, mostly in the form of CO2, and substantial amounts of reduced species and aerosols (Andreae and Merlet, 2001; van der Werf et al, 2010). Droughts tend to increase fire activity in areas with abundant fuel build-up and decrease fire activity in arid regions (Krawchuk and Moritz, 2011; van der Werf et al, 2008). Tropical rainforests in their natural state rarely burn. This is a consequence of moist conditions underneath the canopy and a lack of dry lightning ignitions (Cochrane, 2003). Humans have changed that though using fire for agricultural purposes in tropical forest Land use changes, such as logging and forest fragmentation, increased the forest flammability and number of successful lightning-caused ignitions (Aragão and Shimabukuro, 2010; Cochrane and Laurance, 2008; Fearnside, 2005). In many regions, humans suppress fires, both directly via fire fighting and indirectly by altering the fire seasonality and by modifying fuel build-up through grazing and prescribed burning (Kochi et al, 2010; Le Page et al, 2010; Rabin et al, 2015)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
