Is there a shift in stratospheric aerosol composition ?

Extreme fires leading to Pyrocumulonimbus clouds have had large influences on stratospheric aerosol composition in the past three years by injecting smoke into the upper troposphere and lower stratosphere. Their initial mass loadings seem to be comparable to medium volcanic eruptions. Here, we analyze the Cloud-Aerosol Lidar and InfraRed Pathfinder Satellite Observations (CALIPSO) and the Stratospheric Aerosol and Gas Experiment (SAGEIII/ISS) to separate the relative contribution of fires and volcanoes on stratospheric aerosol optical depth and evaluate their medium to long-term impacts on climate. In 2017, the British Columbia fire in Canada led to a long-lasting stratospheric layer with maximum aerosol optical depth (AOD) near 0.1. This event is ranked the eighth most significant stratospheric feature between 2006 and 2019 and represents 50% of the maximum AOD of the largest volcanic eruption over the same period, the Sarychev eruption in June 2009. More recently, the 2019/2020 Australian fires led to an AOD higher by a factor of 2-3 surpassing the Sarychev AOD peak. The radiative impacts of those fires are explored using a stand alone radiative transfer model and their climate impacts will be discussed.