CO2 emissions from tropical fires and their impact on climate: a two-decade survey from space – TropFire

Our study relies on the interpretation of observations made from space by infrared sounders over more than two decades in terms of tropospheric columns of CO2 and CO, which are then used to study the diurnal variations of these gases that have proven to be a reliable proxy of fire emissions.

The simultaneous study of the tropospheric columns of CO2 and CO with the IASI instrument has highlighted the impact of the successive combustion phases (flaming vs. smoldering) on the diurnal variations of these gases. These observations have also shown the strong increase of biomass burning, and hence on CO2 and CO emissions, over Amazonia in 2010 in answer to the severe drought that affected the region that year.

The time series of CO2 and CO retrieved during this project will be used to estimate the gas surface fluxes, in order to evaluate the existing fire emission databases. In parallel, the data will be used to study the link between fire mission and climate drivers.

1 publication, 3 under preparation
3 presentations in international conferences.

Biomass burning is a large source of atmospheric CO2, CO, aerosols and chemically important gases. Carbon emitted by fire is of the order of that emitted by fossil fuel. Fire directly drives most of the interannual variability in carbon greenhouse gases. It also has a direct influence on human societies in terms of pollution and habitat change. Biomass burning is thus a major component of the carbon cycle and Earth climate system. However, actual estimates of CO2 fire emissions still suffer from large uncertainties and the relationship between emissions, climate and anthropogenic activities is still uncertain. This is particularly true for the tropical region while most of the year-to-year variability in the growth rate of atmospheric CO2 originates there, and influences remote extra-tropical regions.

Here, we propose to derive a new proxy of tropical fire activity based upon satellite observations of upper-air atmospheric CO2 and to apply this dataset to reconstruct more than two decades of biomass burning emissions and their relationship with climate variability. This project will thus combine: (1) the interpretation of observations made by first generation NOAA/TOVS and second generation MetOp/IASI and GOSAT/TANSO infrared spaceborne sounders in terms of upper air diurnal cycle of CO2; (2) the study of fire injection height using a new parameterization of convection induced by fire in the IPSL state-of-the-art atmospheric transport model LMDz; (3) the estimation of CO2 surface fluxes where fire emissions will be constrained by satellite observation of CO2; and (4) the study of future climate scenarios through the use of the IPSL dynamic vegetation model ORCHIDEE for which a new empirical fire model will be designed from satellite-derived correlations between emissions and various climate, ecological and human-related variables.