Gas flaring during oil extraction over the Arctic region is the primary source of warming-inducing aerosols (e.g. black carbon (BC)) with a strong potential to affect regional climate change. Despite continual BC emissions near the Arctic Ocean via gas flaring, the climatic impact of BC related to gas flaring remains uncertain. Here, we present simulations of potential gas flaring using an earth system model with comprehensive aerosol physics to show that increases in BC from gas flaring can potentially explain a significant fraction of Arctic warming. BC emissions from gas flaring over high latitudes contribute to locally confined warming over the source region, especially during the Arctic spring through BC-induced local albedo reduction. This local warming invokes remote and temporally lagging sea-ice melting feedback processes over the Arctic Ocean during winter. Our findings imply that a regional change in anthropogenic aerosol forcing is capable of changing Arctic temperatures in regions far from the aerosol source via time-lagged, sea-ice-related Arctic physical processes. We suggest that both energy consumption and production processes can increase Arctic warming.

There is significant uncertainty in the global inventory of black carbon (BC). Several recent studies have reported BC emission updates, including the Fire Emission Inventory-northern Eurasia, anthropogenic emission in Russia, and global natural gas flaring. Compared with the inventory used by Intergovernmental Panel on Climate Change, these updates are only 10% higher on a global scale but are 3 times greater than previous estimations in Arctic (60-90 degrees N). We applied GEOS-Chem to examine these emission updates and evaluate their impacts on direct forcing. We found that Fire Emission Inventory-northern Eurasia may be substantially overestimated, Russia shows no prominent influence on simulation, and natural gas flaring noticeably improves simulation performance in the Arctic. Model estimated direct forcing of BC is increased by 30% on the global scale and is 2 times higher in the Arctic through application of these emission updates. This study reveals the urgent need to improve the reliability of emission inventories in the high latitudes, especially over Eurasia. Plain Language Summary Recent black carbon (BC) emission updates suggest a substantially higher inventory than that used by Intergovernmental Panel on Climate Change. Through GEOS-Chem modeling, we found that the Fire Emission Inventory-northern Eurasia biomass burning emission is overestimated over northern Eurasia, likely due to employment of U.S. plants species-based emission factors. Russian anthropogenic and natural gas flaring inventories help improve simulation performance in the Arctic. Model estimated direct forcing of BC is doubled when applying these emission updates, indicating the urgent need to further validate and improve the BC emission inventory.

The strategic location of the AERONET site in Ilorin, Nigeria, makes it possible to obtain information on several aerosol types and their radiative effects. The strong reversal of wind direction occasioned by the movement of the ITCZ during the West Africa Monsoon (WAM) plays a major role in the variability of aerosol nature at this site, which is confirmed by aerosol optical depth (AOD) (675 nm) and angstrom ngstrom exponent (AE) (440-870 nm) values with 1st and 99th percentile values of 0.08 and 2.16, and 0.11 and 1.47, respectively. The direct radiative forcing (DRF) and radiative forcing efficiency (RFE) of aerosol, as retrieved from the AERONET sun-photometer measurements, are estimated using radiative transfer calculations for the periods of 2005-2009 and 2011-2015. The DRF and RFE of the dominant aerosol classes-desert dust (DD), biomass burning (BB), urban (UB) and gas flaring (GF)-have been estimated. The median (+/- standard deviation) values of the DRF at the top of the atmosphere (TOA) for the DD, BB, UB and GF aerosol classes are -27.5 +/- 13.2 Wm(-2), -27.1 +/- 8.3 Wm(-2), -11.5 +/- 13.2 Wm(-2) and -9.6 +/- 8.0 Wm(-2), respectively, while those of the RFE are -26.2 +/- 4.1 Wm(-2) delta(-1), -35.2 +/- 4.6 Wm(-2) delta(-1), -31.0 8.4 Wm(-2) delta(-1) and -37.0 +/- 10.3 Wm(-2) delta(-1), respectively. Arguably due to its high SSA and assymetric values, the DD aerosol class shows the largest DRF but the smallest RFE. Its smallest AOD notwithstanding, the GF class can cause greater perturbation of the earth-atmosphere system in the sub-region both directly and indirectly, possibly due to the presence of black carbon and other co-emitted aerosol and the ageing of the GF aerosols. This study presents the first estimate of DRF for aerosols of gas flaring origin and shows that its radiative potential can be similar in magnitude to that of biomass burning and urban aerosol in West Africa.