6. Atmospheric Systems and Societies

What are the main components of the atmosphere and their approximate proportions?

• Nitrogen (N₂): ~78%

• Oxygen (O₂): ~21%

• Argon: ~0.9%

• Carbon dioxide (CO₂): ~0.04%

• Plus trace gases like methane and ozone

What is the structure of the atmosphere in terms of layers?

• Troposphere: weather occurs here

• Stratosphere: contains the ozone layer

• Mesosphere: coldest layer

• Thermosphere: very hot, low density

• Exosphere: transitions into space

What is the greenhouse effect, and why is it important?

The natural greenhouse effect keeps Earth warm by trapping heat via gases like CO₂, CH₄, and water vapor. It makes life on Earth possible by regulating global temperature.

What is the enhanced greenhouse effect?

An increase in greenhouse gases from human activity (e.g. fossil fuels, deforestation) traps more heat, leading to global warming and climate change.

What are the major sources of greenhouse gases?

• CO₂: combustion of fossil fuels, deforestation

• CH₄: agriculture (rice, cattle), landfills

• N₂O: fertilizers

• CFCs: industrial processes and refrigerants

How does albedo affect Earth's energy balance?

Albedo is the reflectivity of surfaces. High albedo (e.g. ice) reflects more sunlight; low albedo (e.g. forests, oceans) absorbs more. Melting ice reduces albedo, increasing warming (positive feedback).

What are the effects of climate change on the hydrological cycle?

• Altered rainfall patterns

• Increased evaporation

• More intense storms

• Melting glaciers and sea level rise

• Changes in drought and flood frequency

What are the potential impacts of climate change on ecosystems?

• Species migration or extinction

• Habitat loss

• Coral bleaching

• Disruption of food webs

• Changes in species distribution and phenology

What are strategies for mitigating climate change?

• Renewable energy

• Carbon taxes and trading

• Afforestation/reforestation

• Energy efficiency

• Carbon capture and storage (CCS)

• Sustainable transport

What is the difference between mitigation and adaptation in climate change response?

• Mitigation: reducing causes of climate change (e.g. emissions)

• Adaptation: adjusting to effects (e.g. flood defenses, drought-resistant crops)

What is the role of international agreements in addressing atmospheric pollution and climate change?

Agreements like the Kyoto Protocol, Paris Agreement, and Montreal Protocol aim to reduce emissions, phase out harmful substances, and encourage global cooperation on climate policy.

What is the Paris Agreement and what are its strengths and weaknesses?

Paris Agreement (2015): aims to limit global warming to well below 2°C, ideally 1.5°C, through nationally determined contributions (NDCs).
Strengths:

• Almost universal participation

• Encourages transparency and review

• Non-binding, allowing flexible national goals
  Weaknesses:

• Non-binding targets = lack of enforcement

• NDCs may be insufficient to meet goals

• Relies heavily on national political will

What are the causes and impacts of photochemical smog?

Causes: sunlight acting on nitrogen oxides and volatile organic compounds (VOCs).
Impacts: respiratory problems, reduced visibility, damage to plants and buildings.

What is acid deposition, and what causes it?

Acid deposition (rain, snow, or dust) is caused by SO₂ and NOₓ emissions from burning fossil fuels, forming sulfuric and nitric acid in the atmosphere.

What are strategies to reduce acid deposition?

• Reduce emissions (low-sulfur fuels, scrubbers)

• Switch to renewables

• International agreements (e.g. Clean Air Act)

• Liming of soils and lakes to neutralize acidity