Uncertainties in Present and Past Fire Carbon Emission Estimates

Much progress has been made in estimating contemporary fire emissions over the past decade, mostly thanks to new satellite information and improved algorithms and modeling. Average fire carbon emissions according to the fourth version of the Global Fire Emissions Database (GFED4s) are 2.2 Pg carbon per year over the 1997-2015 period. The uncertainty in this number is difficult to quantify and we describe where most progress can be made in lowering uncertainties in the near future. This includes improvements in mapping burned area using multiple data streams, combining observations of burned area and fire radiative power (FRP) to better constrain fuel consumption, but also points towards a clear need for conducting new field measurements. Uncertainties in past fire emission estimates since the pre-industrial era are even larger due to the lack of a consistent data source. The available data indicate that fire emissions have increased in deforestation zones and boreal regions but decreased in savanna regions, at least in Africa. Whether past fire emissions were higher or lower than current rates thus depends partly on the balance between those two trends. We provide estimates for the possible range of past fire emissions, discuss the uncertainties therein, and the potential for reducing those uncertainties.