- Intro – define geoengineering.
- Explain the different types of geoengineering.
- Refer to some apprehensions raised.
Geoengineering is a term for various experimental technologies. It refers to deliberate, large-scale intervention carried out in the Earth’s natural systems to reverse the impacts of climate change. They are slowly but steadily gaining salience and broadly fall under two categories: Solar Radiation Modification (SRM)/Radiative Forcing Geoengineering (RFG) and Carbon Dioxide Removal (CDR) technologies.
Types of geoengineering:
Solar radiation management geoengineering : SRM techniques aim to reflect a small proportion of the Sun’s energy back into space. This counters the temperature rise caused by increased levels of greenhouse gasses in the atmosphere. Some proposed techniques include:
- Albedo enhancement: Increasing the reflectiveness of clouds or the land surface so that more of the Sun’s heat is reflected back into space.
- Space reflectors: Blocking a small proportion of sunlight before it reaches the Earth.
- Stratospheric Aerosol Injection (SAI): Introducing small, reflective particles into the upper atmosphere to reflect some sunlight before reaching the surface of the Earth.
- Cirrus Cloud Thinning: It focuses on eliminating or thinning cirrus clouds to allow heat to escape into space. These clouds are found at high altitudes, often absorbing more sunlight than they reflect.
Carbon engineering: GGR techniques aim to remove carbon dioxide or other greenhouse gases from the atmosphere. It directly counters the increased greenhouse effect and ocean acidification. Some proposed techniques include:
- Afforestation: Engaging in a global-scale tree planting effort.
- Biochar: ‘Charring’ biomass and burying it so that its carbon is locked up in the soil.
- Bio-energy with carbon capture and sequestration: Growing biomass, burning it to create energy and capturing and sequestering the carbon dioxide created in the process.
- Ambient Air Capture: Building large machines that can remove carbon dioxide directly from ambient air and store it elsewhere.
- Ocean Fertilization: Adding nutrients to the ocean in selected locations to increase primary production which draws down carbon dioxide from the atmosphere.
- Enhanced Weathering: Exposing large quantities of minerals that will react with carbon dioxide in the atmosphere and storing the resulting compound in the ocean or soil.
- Ocean Alkalinity Enhancement: Grinding up, dispersing, and dissolving rocks such as limestone, silicates, or calcium hydroxide in the ocean. This will increase the ocean’s ability to store carbon and directly ameliorate ocean acidification.
However, the IPCC’s 5th Assessment Report observed that, “SRM techniques entail numerous uncertainties, side effects, risks and shortcomings” and “raise questions about costs, risks, governance and ethical implications of development and deployment”.
While geoengineering is highly risky, some experts argue that countries should deploy these if they fear large-scale casualties or economic disruptions due to extreme climatic events. So Governments should start discussions on establishing global governance mechanism to deter the unilateral deployment of these technologies, while supporting further research on the evolving technologies. However, geoengineering can only act as a supplement to scaling back of GHG emissions in all sectors, not a substitute.