- A modelling study assessed how different deployment locations for marine cloud brightening (MCB) could influence Africa’s climate under a middle-of-the-road climate change scenario.
- MCB over the Southeast Pacific showed the strongest cooling effect, reducing temperature and precipitation extremes.
- Deployments over other regions (Northeast Pacific and Southeast Atlantic) had weaker cooling effects, with some areas that could experience residual warming.
- MCB could be more effective at cooling maximum and hottest day temperatures than minimum and coldest day temperatures.
A Degrees-funded team in South Africa, co-led by Romaric Odoulami and Chris Lennard from the University of Cape Town, investigated how marine cloud brightening (MCB), a solar radiation modification (SRM) strategy, might affect the African climate. MCB involves injecting sea-salt aerosols into low level marine clouds to brighten them. This increases their reflectiveness, which reduces how much of the sun’s radiation reaches the Earth’s surface. This ground-breaking SRM study is the first MCB paper funded by Degrees and the first to be published from an African team. It used climate simulations to compare the effects of MCB across three oceanic regions: the Northeast Pacific (NEP), the Southeast Pacific (SEP), and the Southeast Atlantic (SEA). A fourth scenario examined the combined effects of deploying MCB in all three regions simultaneously.
The team compared these scenarios against a middle-of-the-road emissions scenario (leading to around 2.5-2.7°C warming by 2100) for 2035–2054. The findings show that deploying MCB in the Southeast Pacific could have the strongest cooling effect, particularly over West Africa, where it could reduce both mean and extreme temperatures and precipitation compared to the middle-of-the-road climate change scenario. Deploying MCB in the Southeast Atlantic and the Northeast Pacific had weaker cooling impacts, with some areas that could still experience substantial residual warming. The study also found that MCB is more effective at cooling maximum temperature and associated hottest day temperature than minimum temperature and associated coldest day temperature. Precipitation changes varied by region, with deployment in the Southeast Pacific and the Southeast Atlantic leading to wetter conditions in some parts of West and Central Africa but drier conditions in Southern Africa. The research highlights the complexity of regional climate responses to MCB, reinforcing results from previous studies, which suggest that where MCB is deployed plays a crucial role in determining its effectiveness. Romaric said: “Brightening clouds in parts of the Atlantic and Pacific oceans could reduce some of the risks associated anthropogenic warming. However, how and where MCB is deployed could result in very different climate responses. Our findings suggest that using MCB to reduce global warming could offset some climate impacts and exacerbate others.” The authors emphasise that while MCB could reduce some climate risks, it does not counter the urgent need to reduce greenhouse gas emissions. Any assessments of the risks and benefits of MCB must consider the scenario uncertainties and focus on assessing impacts at regional scale.
‘Africa’s Climate Response to Marine Cloud Brightening Strategies Is Highly Sensitive to Deployment Region’, published in Atmospheres by Romaric C. Odoulami, Haruki Hirasawa, Kouakou Kouadio, and colleagues.
