Comparison of global inventories of monthly CO emissions derived from remotely sensed data

Five global inventories of monthly CO emissions named VGT, ATSR, MODIS, GFED2 and MOPITT and based on remotely sensed active fires and/or burned area products for the year 2003 are compared. The objective is to highlight similarities and differences focusing on the geographical and temporal distribution of the emissions at the global and continental scale and for three broad land cover classes (forest, savanna/grassland and agriculture). Emissions for the year 2003 range between 398 Tg CO and 1422 Tg CO. Africa shows the best agreement among the inventories both in terms of total annual amounts (162.4-367.4 Tg CO) and of seasonality despite some overestimation of emissions from forest and agriculture land covers observed in the MODIS inventory. Eurasian boreal forests most contribute to the large difference observed due to the high fuel loads involved in burning. In these regions VGT tends to overestimate emissions especially outside the typical fire season. In South America the perfect agreement of annual totals given by VGT and MOPITT (121 Tg CO) hides a different geographical distribution of CO sources: compensation effects between the 0.5 grid cells lead to a better agreement when looking at regional or annual totals. Looking at the broad land covers, the range of contribution to global emissions is 64-74%, 13-19% and 3-4% for forests, savanna/grasslands and agriculture, respectively. Results suggest that there is still large uncertainty in global estimates of emissions and attention should be paid to accurate parameterization of vegetation characteristics and conditions at the time of fire.