Context:
A report by the Climate Overshoot Commission said that potentially dangerous experimental geoengineering methods – including controversial “solar radiation modification” – need to be halted until they have been researched thoroughly.
About Geoengineering:
- Manipulating the earth’s climate to lower its temperature in a bid to counter global warming.
- Generally, geoengineering techniques can be grouped into two categories:
- Solar Radiation Management (SRM) or Solar Geoengineering – aim to reflect a small proportion of the Sun’s energy back into space, counteracting the temperature rise caused by increased levels of greenhouse gases in the atmosphere
- Greenhouse Gas Removal (GGR) or Carbon Geoengineering – aim to remove carbon dioxide or other greenhouse gases from the atmosphere
The basic idea behind solar geoengineering
Earth’s Temperature and Heat Absorption:
- The Earth’s surface temperature rises as it absorbs heat energy from the sun, primarily in the form of shortwave radiation.
- A portion of the absorbed heat is re-emitted as longwave infrared radiation, which warms the atmosphere.
- Heat at higher altitudes can escape into space, without significantly impacting the temperature of the Earth’s atmosphere.
- The temperature of the atmosphere at the altitude where this heat emission occurs determines the overall outgoing energy.
Greenhouse Gas Effect:
- Greenhouse gases like carbon dioxide impede the escape of infrared radiation from the Earth’s atmosphere.
- This interference creates an imbalance between the incoming and outgoing energy, resulting in the Earth’s surface warming up.
Solar Geoengineering:
- Solar geoengineering aims to artificially increase the amount of heat radiated back into space.
- By doing so, it intends to reduce the Earth’s surface temperature.
In summary, the Earth’s temperature rises due to heat absorption from the sun, greenhouse gases trap some of this heat, and solar geoengineering seeks to mitigate this effect by enhancing heat radiation into space.
Some proposed techniques include:
- Albedo enhancement – Increasing the reflectiveness of clouds (marine cloud brightening) or the land surface.
- Space reflectors
- Stratospheric aerosols – Introducing small, reflective particles into the upper atmosphere to reflect some sunlight before it reaches the surface of the Earth.
Carbon Geoengineering
- Designed to extract carbon dioxide and other greenhouse gases from the atmosphere, effectively mitigating the heightened greenhouse effect and reducing ocean acidification.
- Various proposed approaches include:
- Afforestation
- Biochar – ‘Charring’ biomass and burying it – 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 Fertilisation – Adding nutrients to the ocean in selected locations to increase primary production which draws down carbon dioxide from the atmosphere.
- Enhanced Weathering – Revealing extensive mineral deposits that can chemically interact with carbon dioxide from the atmosphere and subsequently sequestering the resulting compound in either the ocean or soil.
- Ocean Alkalinity Enhancement – Grinding up, dispersing, and dissolving rocks such as limestone, silicates, or calcium hydroxide in the ocean to increase its ability to store carbon and directly ameliorate ocean acidification.
About Climate Overshoot Commission:
- The Global Commission on Governing Risks from Climate Overshoot
- An independent group of eminent global leaders, who will recommend a strategy to reduce risks should global warming goals be exceeded.
- Operates in the context of the Sustainable Development Goals and other relevant governance frameworks.
Source: The Hindu
Previous year question
In the context of which of the following do some scientists suggest the use of cirrus cloud thinning technique and the injection of sulphate aerosol into stratosphere?
[UPSC Civil Services Exam – 2019 Prelims]
(a) Creating the artificial rains in some regions
(b) Reducing the frequency and intensity of tropical cyclones
(c) Reducing the adverse effects of solar wind on the Earth
(d) Reducing the global warming
Answer: (d)
