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Stratospheric Aerosol Intervention (SAI)


Prelims: Environment (Technologies for Climate Change mitigation), Stratospheric Aerosol Intervention, Stratosphere

Mains: General Studies-III  Conservation, Environmental Pollution and Degradation, Environmental Impact Assessment.

Why in the News ?

A recent study looked at the impact of stratospheric aerosol intervention (SAI) in mitigating global warming effects in West Asia (also known as Middle East) and North Africa (MENA).

Source: DTE

📌 FYI on Prelims


  • It is the layer of Earth’s atmosphere lying between the troposphere and the mesosphere. 
  • The stratosphere extends from the tropopause at about 10 to 17 km (about 6 to 11 miles) altitude to its upper boundary (the stratopause) at about 50 km (30 miles).
  • It’s characterized by a highly stable temperature gradient that cools from top to bottom.
  • It also contains the ozone layer.
  • Commercial jet aircraft fly in the lower stratosphere to avoid turbulence and increased atmospheric drag, which are common in the troposphere below.
  • This layer holds 19 percent of the atmosphere’s gases but very little water vapor


  • Stratospheric Aerosol Intervention (SAI)

    • Stratospheric Aerosol Intervention (SAI), also known as Stratospheric Aerosol Injection, is a geoengineering or climate engineering approach that uses tiny reflective particles or aerosols to reflect sunlight into space in order to cool the planet and reverse or stop global warming.
    • It aims to mimic the cooling effects of volcanic eruptions by injecting sulfur dioxide (SO2) directly into the stratosphere, where it forms sunlight-reflecting sulfate aerosols. 
    • The 1991 eruption of Mount Pinatubo in the Philippines, often cited as the inspiration for this concept, deposited massive amounts of particulate matter and sulfur dioxide (SO2) into the atmosphere.
    • This aerosol layer was reported to have lowered average temperatures around the world by about 0.5 °C (0.9 °F) over the following few years. 
    • It is believed that as more radiation is scattered in the stratosphere by aerosols, less would be absorbed by the troposphere, the lower level of the atmosphere where weather primarily occurs.
    • The production of such an artificial aerosol layer could be accomplished by shooting  sulfur particles into the stratosphere with cannons or dispersing them from  balloons or other aircraft.
  • Aerosols

    • They are tiny solid or liquid particles suspended in air or a gas.
    • Aerosols can be natural, such as fog or gas from volcanic eruptions, or artificial, such as smoke from burning fossil fuels.
    • Aerosol particles are either emitted directly into the atmosphere (primary aerosols) or produced in the atmosphere from precursor gases (secondary aerosols).
    • Aerosol particles are tiny, but numerous, and often comprise a number of inorganic and organic substances.
    • True aerosol particles range in diameter from a few millimicrometres to about 1 micrometre (equal to 10-4 cm). 
    • Particles with a diameter of less than 0.1 micrometer are sometimes referred to as Aitken nuclei.
    • Visible forms of atmospheric aerosol plumes include smoke, smog, haze, and dust.


Prelims: PYQ/FAQ

Q. Consider the following:

  1. Aerosols
  2. Foam agents
  3. Fire retardants
  4. Lubricants

In the making of how many of the above are hydrofluorocarbons used?

a) Only one

b) Only two

c) Only three

d) All four


  • Hydrofluorocarbons (HFCs) are synthetic chemicals that are used as refrigerants, blowing agents, firefighting agents, solvents, and propellants. They are non-flammable, chemically stable, and non-reactive.
  • HFCs are potent greenhouse gases, with global warming potentials (GWPs) that are hundreds to thousands of times greater than carbon dioxide (CO2) per unit of mass. They are also short-lived climate pollutants (SLCPs), meaning that they have atmospheric lifetimes of less than 30 years.
  • HFCs were introduced in the late 1980s to replace ozone-depleting substances, such as chlorofluorocarbons (CFCs). However, their use has become increasingly regulated in the 21st century due to their impact on climate change.
  • The Kigali Amendment to the Montreal Protocol is a global agreement to phase down HFC production and consumption. Under the Kigali Amendment, all countries have agreed to reduce their HFC consumption by 85% by 2050.
  • There are a number of alternatives to HFCs that are available and being developed. These alternatives have lower GWPs and are often more energy-efficient. Some examples of HFC alternatives include:
    • Hydrofluoroolefins (HFOs)
    • Natural refrigerants, such as carbon dioxide (CO2), ammonia, and propane
    • Hydrocarbon blends
    • Water
  • HFCs are entirely man-made. They are primarily produced for use in refrigeration, air-conditioning, insulating foams and aerosol propellants, with minor uses as solvents and for fire protection. HFCs are not used for making lubricants. 

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