Context: A recent study presents a novel approach to Stratospheric Aerosol Injection (SAI) as a potential means to directly cool the Earth.
Relevance of the Topic: Prelims: Concept and Mechanism of Stratospheric Aerosol Injection Method.
What is Stratospheric Aerosol Injection (SAI)?
- SAI is a proposed method of cooling the planet and reducing the impacts of climate change by adding a layer of tiny reflective particles (aerosols) to the high atmosphere.
- Aerosols reflect sunlight back into space, increasing Earth’s albedo and lowering surface temperatures by reducing the amount of sunlight reaching the earth.
- The method was inspired by volcanic eruptions, which have been known to have a cooling effect on the planet by spewing aerosols into the air.
- How well SAI works depends on the type of material injected, the timing of the injection, and the location.
Key Findings:
- Injecting 12 million tonnes of sulphur dioxide every year at an altitude of 13 km in the local spring and summer seasons of each hemisphere could cool the planet by approximately 0.6 degrees Celsius.
- To achieve 1°C cooling, 21 million tonnes/year of sulphur dioxide would be required.
- If the particles were injected at an even higher altitude in the subtropics, only 7.6 million tonnes would be required annually.
- Higher altitude injection is more effective because particles stay for longer. At lower altitudes particles are more likely to be caught in clouds and washed out by rain. Despite this, researchers are exploring low-altitude spraying because it is technically less challenging.
While there are some benefits to this method, using three times the usual amount of aerosols carries greater risk.
Risks and Side effects of SAI
- Social and geopolitical risks: If one country injects aerosols into the stratosphere, all countries will be affected, it could affect global climate patterns, leading to conflicts.
- Delayed recovery of the ozone hole and increased risk of acid rain.
- Cooling could mask warming on the ground and make countries complacent about curtailing emissions.