Definition
Geoengineering
Intentional, large-scale modification of the climate system to counteract global warming, usually without reducing emissions at the source.
- Geoengineering is the deliberate, large-scale intervention in Earth’s climate system.
- It aims to reduce the impacts of climate change, but treats the symptoms, not the root cause (GHG emissions)
- Two major categories:
- Solar Radiation Management (SRM): reflects sunlight away from Earth
- Greenhouse Gas Removal (GGR): removes CO₂ from the atmosphere
- Methods include space mirrors, stratospheric aerosols, cloud seeding, ocean fertilization, biochar, carbon capture and storage, and direct air capture.
- All options involve high uncertainty, high cost, limited real-world trials, and strong geopolitical implications
Solar Radiation Management (SRM)
1. Stratospheric Aerosol Injection (SAI)
- Releases reflective sulfate aerosols into the stratosphere, mimicking volcanic eruptions
- Aerosols scatter sunlight back into space, lowering temperatures
- Delivered via aircraft, balloons, or artillery
- Cooling potential is high, but effects are temporary, lasting 1–3 years
- Drawbacks include:
- Reduced rainfall, affecting agriculture
- Regional drought risks
- Uncertain effects on cloud formation, monsoons, and ozone chemistry
- SAI acts like pulling down a reflective “sunshade” over the planet.
- It cools quickly but disappears once removed.
2. Space Mirrors / Solar Shields
- Uses large mirrors in space to block or deflect sunlight
- Could reduce solar input by a small percentage but create global cooling
- Requires extreme precision, launch capacity, and energy
- High costs, extremely difficult to maintain, and no real-world trials
Space mirrors are one of the most technologically ambitious ideas in climate engineering and remain mostly theoretical.
3. Cloud Brightening (Marine Cloud Enhancement)
- Sprays sea-salt particles into marine clouds to make them whiter and more reflective
- Short-term, regional cooling effect, especially over oceans
- Already used experimentally for drought and heat mitigation
- Risks include unpredictable rain patterns, flooding, and regional atmospheric changes
Greenhouse Gas Removal (GGR)
1. Ocean Fertilization
- Adding iron, nitrogen, or phosphorus to stimulate phytoplankton growth
- Phytoplankton absorb CO₂ during photosynthesis; later sink to the ocean floor
- Oceans store ~35,000 gigatonnes of carbon, making them a major long-term sink
- Concerns:
- Algal blooms may disrupt ecosystems
- Possible dead zones, oxygen depletion
- Uncertain long-term stability of stored carbon
