Despite international climate action commitments under the Paris Agreement, current Nationally Determined Contributions (NDCs) remain insufficient to limit warming to 1.5°C above preindustrial levels. As a result, various climate intervention approaches are suggested to reduce warming, alongside efforts to reduce emissions. A category of approaches, solar radiation modification (SRM), involves altering the Earth’s radiation budget by limiting the amount of solar energy available at the Earth’s surface. One such approach, stratospheric aerosol geoengineering (SAG), involves the injection of reflective aerosols or their precursors into the stratosphere - an upper layer of the atmosphere starting at approximately 10-15 km above ground - to counterbalance human-induced warming by reflecting some of the incoming solar radiation back into space, thereby reducing warming at the Earth’s surface. The approach seeks to mimic the cooling effect of explosive volcanic eruptions like Mount Pinatubo (Philippines) in 1991. During the eruption of Mount Pinatubo, megatons of sulphur dioxide (SO2) were released into the atmosphere, some of which reached the stratosphere, where they oxidised to form sulfuric acid, which in turn formed fine aerosol droplets capable of reflecting a small portion of incoming sunlight back to space. This phenomenon induced a global cooling of approximately half a degree up to two years after the Pinatubo eruption. While modelling studies confirm the cooling potential of injecting aerosol into the stratosphere, its influence on precipitation is regionally heterogeneous, potentially increasing the risk of food insecurity in the most climate-vulnerable regions worldwide.
Additionally, studies modelling SAG have almost exclusively focused on assessing the potential of sulphate-based aerosols despite the associated risk to human and other natural systems. Further modelling work has shown that using sulphate aerosols for SAG could induce stratospheric ozone depletion, delay the recovery of the ozone layer, increase surface ozone, and increase exposure to UV-B radiation, with significant disruptions to human health (e.g., increased risks of skin cancer and related mortality) and other natural systems. These risks have sparked interest in researching the potential implications of alternative materials for SAG, which may yield different outcomes while still inducing radiative cooling.
The project aims to characterise the global and regional climate response to alternative materials (alumina and calcite) for stratospheric aerosol geoengineering and explore the implications for agriculture, biodiversity, renewable energy, and water resources across Africa using climate model simulations that incorporate more advanced stratospheric chemistry representations produced by the National Centre for Atmospheric Research (NCAR).
Objectives:
- Contribute to developing an Africa SRM research hub to build capacity in SRM research and modelling in Africa
- Assess the global and regional climatic response to stratospheric aerosol injection with alternative (non-sulphate) materials.
- Assess the implications of SRM-induced changes in the climate for agricultural production, water resources, biodiversity, and renewable energy across Africa.
- Quantify the climatic risk associated with sulphate versus non-sulphate aerosols for stratospheric aerosol injection.
Collaborating institutions:
- The University of Cape Town (South Africa) hosts the research project
Partners include
- National Center for Atmospheric Research (NCAR, USA)
- The National University of Agriculture (Benin)
- University of Parakou (Benin)
- National Institute of Cartography (Cameroon)
- Université Felix Houphouët-Boigny (Côte d’Ivoire)
- University of Nairobi (Kenya)
- Augsburg University (Germany)
- University Peleforo Gon Coulibaly (Côte d’Ivoire)
- Kenya Meteorological Services (Kenya)
Project team
Project Funder
