The role of anthropogenic aerosol in near-future sub-Saharan precipitation

Sub-Saharan Africa is densely populated and highly sensitive to climate change. West Africa has experienced both prolonged periods of drought and increased flooding over the last 50 years, and there is substantial concern that intensifying climate risk will exacerbate existing vulnerabilities. Although historical Sahel drought has been attributed to aerosol increases, African precipitation responses to aerosol changes are relatively unexplored. There is almost no existing literature exploring the impact of aerosol changes on East African rains.

There are large uncertainties in projections of African precipitation due to differences between models. Differences in the simulation of the atmospheric response to forcing, and the response to aerosol forcing in particular, play an important role in this uncertainty. Aerosol emissions from remote regions have been implicated in driving historical changes in several African regions, while some of the largest uncertainties in future emissions are also found over Africa. Much of the current requirement for projection information for Africa focuses on near-term, 10-40-yr time scale, climate adaptation. Changes in short-lived pollutants like aerosols play a much stronger role than greenhouse gases in driving the spread of near-term projections. In this project, the role of aerosol in African climate projections, and the uncertainties in these projections, will be explored through three research questions:
- What is the response of sub-Saharan African climate to potential future anthropogenic aerosol changes?
- What are the relative roles of local and remote aerosol changes, and different aerosol species, in climate projections for Africa?
- What are the mechanisms for West African and East African precipitation responses to regional aerosol forcing? Do these mechanisms depend on model climatology, model process representation, or internal variability?
To address these questions, the student will have access to a new set of coupled model experiments, designed to explore the role of aerosol in near-term projections and be easily comparable to projections typically used in decision making. The student will perform idealised experiments to aid diagnosis of important mechanisms. There is the potential to expand these experiments to quantify the role of model biases, or the role of internal variability, in the response to aerosol changes.

This project is an opportunity for the student to become an expert in a scientific topic that will become increasingly relevant as climate change, and societal responses to increased climate risk, progress. The regions where precipitation changes are expected have a large population and are undergoing considerable development with a need for mitigation. The project will thus potentially inform the next assessment of the IPCC.