OpenNEX: Sensitivity of the simulated climate to the prescribed stratospheric sulfate aerosols

Bala Govindasamy (July 16, 2018)

Geoengineering the earth's climate using sulfate aerosols in the stratosphere is proposed as an option to counteract the human-induced climate change. In this study, using the NCAR climate model, the sensitivity of the geoengineered climate to the aerosol particle size and the prescribed altitude is assessed by prescribing a fixed total amount of sulfate aerosols uniformly at different levels of the stratosphere. Experiments using two sizes for the aerosol particles are studied; the smaller background and larger volcanic aerosols. We find that background aerosols are more effective in cooling the planet for any prescribed altitude. Volcanic size aerosols are more effective in cooling the climate when they are prescribed at the higher levels of the stratosphere. There is no such height dependency for the background aerosols. The near-IR and terrestrial radiation absorption by volcanic aerosols lead to larger stratospheric heating compared to the background aerosol cases. This extra warming causes large dynamical changes in the stratosphere as well as an increase in stratospheric water vapour. Our results highlight the challenges in precisely controlling the global climate when important details of aerosol microphysics and transport are considered.