Geoengineering could protect Amazon rainforest from climate change

Stratospheric aerosol injection (SAI) aims to artificially cool the Earth by increasing the reflection of incoming solar radiation, thereby offsetting warming caused by anthropogenic greenhouse gases. SAI is designed to mimic explosive volcanic eruptions by injecting aerosols into the stratosphere.

Concerns have been raised that SAI could suppress vegetation productivity by reducing sunlight and rainfall. However, the new study – by the University of Exeter – shows that state-of-the-art climate models actually project an increase in global land carbon storage under SAI compared to both high and mid-range CO₂ scenarios.

The effects of SAI are especially clear in Amazonia, where land carbon storage increases by 10.8% compared to a high CO₂ scenario. This is mainly because SAI reduces the warming that suppresses forest and soil carbon growth in this high CO₂ scenario.

The high CO₂ plus SAI scenario also results in 8.6% more land carbon in Amazonia compared to the mid-range CO₂ emissions scenario, which has a similar level of global warming.

Co-author Professor Peter Cox, Director of Exeter’s Global Systems Institute, said: “Surprisingly, in these three scenarios, we find that the Amazon rainforest is most productive in the scenario with SAI geoengineering.”

The Amazon rainforest is considered particularly vulnerable to vegetation loss as a result of rising global temperatures and ongoing deforestation.

This new study – published in the journal Earth System Dynamics – suggests that SAI could protect against the risk of climate change induced carbon losses from the Amazon rainforest.

The research team say that while there are many legitimate concerns about the possibility of SAI geoengineering in the real world, research on this matter and its impacts needs to be openly discussed.

“The best protection for the Amazon rainforest in the long-term is a combination of reduced rates of both deforestation and anthropogenic climate change, but SAI might provide some emergency protection if we fail to get climate change under control,” said lead author Isobel Parry, of Exeter’s Department of Mathematics and Statistics.

The paper is entitled: “Stratospheric aerosol injection geoengineering has the potential to increase land carbon storage and to protect the Amazon rainforest.”