Context: Rapidly reducing aerosol emissions, without concurrently reducing greenhouse gas emissions, could expose a large fraction of vulnerable people in highly polluted regions of India to a sudden acceleration of warming and extreme heat.
Relevance of the Topic: Prelims: Aerosols: Role and Removal; Aerosols vs GHGs.
What are Aerosols?
- Aerosols are tiny solid or liquid particles suspended in the atmosphere. E.g., black soot, sulphur aerosols, sea salt, dust etc.
- Origin:
- Natural sources (such as volcanic eruptions, forest fires, and sea spray)
- Human activities (such as industrial emissions, vehicular pollution, and burning of fossil fuels).
- Role of Aerosols:
- Aerosols scatter solar radiation, thus, reducing the amount of heat reaching the Earth's surface.
- They act as cloud-condensation nuclei and contribute to cloud formation and influence the water cycle.
What are Greenhouse Gases?
- GHGs are gases that trap heat in the Earth's atmosphere, leading to global warming.
- Key GHGs: Carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases.
Greenhouse Gases vs. Aerosols
- GHGs trap heat and contribute to global warming, whereas aerosols can counteract this effect by reflecting sunlight.
- GHGs have a long atmospheric lifespan- persisting for decades to centuries; their effects are global and long-term. Aerosols have a shorter lifespan compared to GHGs, meaning their effects are more immediate and localised.
Aerosols as Pollutants:
While aerosols provide a temporary cooling effect, they also contribute to air pollution which has significant health and environmental repercussions.
- Coal-based thermal power plants in India contribute significantly to GHG, aerosol emissions and particulate matter pollution.
- Sulphur dioxide (SO2) emitted from coal combustion forms sulphate aerosols, which reflect sunlight and cool the atmosphere.
Impacts of Aerosol Removal from Environment
The removal of aerosols at its source to reduce pollution could inadvertently contribute to warming.
1. Aerosols affecting Temperature rise in India:
- Studies indicate that aerosols have masked a portion of the warming caused by GHG emissions.
- Between 1906 and 2005, India warmed by 0.54°C, but the actual warming due to GHGs was around 2°C, with aerosols offsetting approximately 1.5°C.
- If aerosols were not present, India would have experienced much greater warming.
- The Ministry of Earth Sciences reported that India's average temperature rose by 0.7°C from 1901 to 2018, with GHG-induced warming being partially countered by aerosols.
2. Impact on Monsoon and Rainfall Patterns:
- Aerosols have played a role in decreasing Indian monsoon rainfall due to their cooling effect, especially in the Northern Hemisphere. Aerosols have a cooling effect by scattering sunlight. This results in reduced land-sea temperature contrast, which in turn results in a weaker South-West monsoon.
- The removal of aerosols may increase rainfall, but the resulting warming can cause erratic weather patterns, climate volatility and extreme events.
3. Global and Regional Implications of Aerosol Reduction:
- The impact of aerosols is not confined to national borders; changes in emissions in one region can affect distant locations. E.g., China's reduction in aerosol emissions intensified heatwaves along the west coast of North America.
- Similarly, any significant increase in aerosols over India could negatively impact the hydrological cycle. The remote effects of aerosols must be considered when formulating climate policies.
Net-Zero Targets and Future Challenges:
- While reducing aerosols improves air quality and public health, it may also lead to a sudden increase in heat stress. Achieving net-zero emissions requires simultaneous reductions in both GHGs and aerosols.
- A gradual approach to aerosol reduction, coupled with aggressive GHG mitigation, is crucial for maintaining climate balance.
Need for Long-Term Adaptation Policies
- Policymakers must prepare for the consequences of aerosol reduction by implementing robust heat action plans and comprehensive long-term strategies.
- Future policies should consider the trade-offs between improved air quality, increased temperatures, and altered rainfall patterns.
- Investment in urban planning, climate adaptation measures, and early warning systems will be essential.
A well-planned transition strategy is crucial to ensuring climate resilience while addressing pollution control measures effectively. Policymakers must balance short-term and long-term climate goals to protect vulnerable populations while mitigating global warming.