Aerosols

A recent study has highlighted that water vapour contributes more to atmospheric heating than aerosols. However, aerosols continue to play a complex and significant role in influencing climate, air quality, and human health.

About Aerosols

Aerosols are fine solid or liquid particles suspended in the atmosphere. They typically remain in the atmosphere for a few days to weeks before settling to the ground or being washed out by rain or snow.

Aerosols originate from both anthropogenic and natural sources:

• Human-made sources include the burning of fossil fuels and biofuels, industrial emissions, and vehicular pollution.

• Natural sources include desert dust, sea spray, volcanic eruptions, and forest fires.

Although aerosol particles are extremely small, they are numerous and chemically diverse, consisting of various inorganic and organic substances.

Common visible forms of aerosols include smoke, smog, haze, and dust, which are often associated with air pollution episodes.

How Do Aerosols Affect the Climate?

Aerosols influence the climate system through multiple pathways:

1. Direct Radiative Effects

Aerosols interact directly with solar radiation.

• Some aerosols, such as sulphates and sea salt, reflect incoming sunlight back into space, thereby producing a cooling effect.

• Others, especially black carbon, absorb solar radiation and contribute to atmospheric warming. Because black carbon is dark in colour, it is highly efficient at absorbing heat.

Thus, aerosols can have both cooling and warming effects, depending on their composition.

2. Indirect Effects through Clouds

Aerosols act as Cloud Condensation Nuclei (CCN), around which water vapour condenses to form clouds.

By influencing the number and size of cloud droplets, aerosols can:

• Alter cloud reflectivity (albedo),

• Change cloud lifetime,

• Modify precipitation patterns.

These changes affect the Earth’s radiation balance, thereby influencing climate systems.

Impact of Aerosols on Human Health and Economy

Beyond climate, aerosols significantly affect human health and socio-economic systems.

1. Public Health Impacts

Fine particulate matter, especially particles smaller than 2.5 micrometres (PM2.5), can penetrate deep into the lungs and even enter the bloodstream. Exposure to such particles is associated with:

• Respiratory diseases,

• Cardiovascular disorders,

• Premature mortality due to air pollution.

Thus, aerosols contribute significantly to poor air quality and public health burdens.

2. Impact on Transport and Energy

High concentrations of aerosols such as desert dust and volcanic ash can:

• Disrupt air and road transport,

• Reduce visibility,

• Damage aircraft engines.

Aerosols also reduce solar irradiance, thereby lowering the efficiency of solar power plants.

Conclusion

Although recent research suggests that water vapour has a stronger warming effect on the atmosphere than aerosols, aerosols remain critical climate agents due to their dual role in cooling and warming the atmosphere. Additionally, their significant impacts on cloud formation, air quality, public health, and energy systems make them an important area of study in climate science and environmental governance.