Lecture Notes: Climate Change – Science, Impacts, and Solutions

1. Introduction

Climate change refers to long-term alterations in temperature, precipitation, wind patterns, and
other aspects of the Earth’s climate system. While Earth’s climate has always changed naturally, the
current trend of rapid warming is primarily due to human activities, especially the burning of fossil
fuels, deforestation, and industrial processes.

Why study climate change?

 It affects every aspect of life — ecosystems, economies, human health, and geopolitics.

 Understanding the science allows informed policymaking.

 Mitigation and adaptation require coordinated global action.

2. The Science of Climate Change

2.1 Greenhouse Effect

The greenhouse effect is a natural process that warms the Earth’s surface:

1. Solar radiation reaches the Earth’s atmosphere.

2. Some radiation is reflected back to space.

3. The rest is absorbed by land and oceans, heating the planet.

4. The Earth emits infrared radiation back toward space.

5. Greenhouse gases trap some of this heat, warming the atmosphere.

Major greenhouse gases (GHGs):

 Carbon dioxide (CO₂) – from fossil fuel combustion and deforestation.

 Methane (CH₄) – from livestock, rice paddies, landfills.

 Nitrous oxide (N₂O) – from fertilizers, industrial processes.

 Fluorinated gases – synthetic compounds from refrigeration, manufacturing.

2.2 Evidence of Climate Change

 Temperature records: Global average temperatures have risen ~1.1°C since the late 19th
century.

 Glacial retreat: Significant ice loss from Greenland, Antarctica, and mountain glaciers.

 Sea-level rise: Due to melting ice and thermal expansion of seawater.

 Shifts in species distribution: Many plants and animals moving toward cooler regions.
  Extreme weather: Increased frequency/intensity of heatwaves, droughts, and storms.

2.3 Anthropogenic vs. Natural Causes

Natural factors:

 Volcanic eruptions.

 Solar variability.

 Orbital cycles (Milankovitch cycles).

Human factors:

 Fossil fuel burning (coal, oil, gas).

 Large-scale deforestation.

 Industrial emissions.

 Agricultural practices.

3. Climate Modeling

Climate models simulate interactions between the atmosphere, oceans, land surface, and ice.
They are used to:

 Predict future climate scenarios.

 Test effects of various GHG emission pathways.

 Inform policy decisions.

Representative Concentration Pathways (RCPs):

 RCP 2.6: Aggressive mitigation; warming limited to ~1.5°C–2°C.

 RCP 4.5: Stabilization of emissions by mid-century.

 RCP 8.5: High emissions scenario; warming >4°C by 2100.

4. Impacts of Climate Change

4.1 Environmental Impacts

 Melting ice caps → Rising seas, coastal flooding.

 Ocean acidification → Coral bleaching, decline in marine biodiversity.

 Ecosystem disruption → Habitat loss, species extinction.

 Wildfires → Linked to hotter, drier conditions.

 Agriculture: Crop yields decline in many regions due to heat and drought.

 Infrastructure: Damage from flooding, storms.

 Energy: Increased demand for cooling; disruptions in hydropower.

 Insurance: Higher costs due to more frequent disasters.

4.3 Social and Health Impacts

 Heat stress: Increased mortality during heatwaves.

 Spread of diseases: Mosquito-borne illnesses expanding into new regions.

 Climate refugees: Displacement due to sea-level rise, drought.

 Food security: Reduced agricultural productivity in vulnerable regions.

5. Climate Change and the Oceans

 Thermal expansion: Water expands as it warms, contributing to sea-level rise.

 Loss of sea ice: Reduces albedo (reflectivity), accelerating warming.

 Acidification: CO₂ dissolves in seawater, forming carbonic acid, lowering pH.

 Disrupted currents: Changes in temperature and salinity affect ocean circulation.

6. Mitigation Strategies

Mitigation refers to reducing or preventing the emission of GHGs.

6.1 Renewable Energy

 Solar power: Photovoltaic panels, concentrated solar plants.

 Wind energy: Onshore and offshore wind farms.

 Hydropower: Large dams and small-scale hydro.

 Geothermal: Heat from Earth’s interior.

6.2 Energy Efficiency

 Building insulation.

 Efficient appliances.

 Industrial process optimization.

 Smart grids.
6.3 Carbon Capture and Storage (CCS)

 Capturing CO₂ emissions from power plants and storing them underground.

 Bioenergy with CCS (BECCS) combines biomass energy with carbon capture.

6.4 Reforestation and Afforestation

 Planting trees to absorb CO₂.

 Protecting existing forests from logging.

6.5 Sustainable Agriculture

 Reduced fertilizer use.

 Methane capture from livestock waste.

 Crop diversification.

7. Adaptation Strategies

Adaptation involves adjusting to actual or expected climate changes.

7.1 Infrastructure

 Sea walls, flood barriers.

 Elevated buildings in flood-prone areas.

 Heat-resistant road materials.

7.2 Water Management

 Rainwater harvesting.

 Efficient irrigation systems.

 Desalination in water-scarce areas.

7.3 Agricultural Adaptation

 Drought-resistant crops.

 Adjusted planting seasons.

 Shade structures for livestock.

8. International Policy Frameworks

8.1 United Nations Framework Convention on Climate Change (UNFCCC)

 Basis for international cooperation.

8.2 Kyoto Protocol (1997)

 Legally binding emission reduction targets for developed countries.

8.3 Paris Agreement (2015)

 Limit global warming to “well below 2°C” and pursue efforts for 1.5°C.

 Nationally Determined Contributions (NDCs) submitted by each country.

9. Role of Technology

 AI in climate modeling: Improved prediction accuracy.

 Smart grids: Integrating renewable energy efficiently.

 Battery storage: Smoothing renewable energy supply.

 Precision agriculture: Minimizing waste, optimizing yield.

10. Climate Change Communication

 Public understanding is crucial for action.

 Avoiding misinformation and climate denial.

 Using clear, relatable examples to show local impacts.

11. Climate Justice

 Recognizes that climate change impacts are not evenly distributed.

 Developing nations, despite lower emissions, face greater risks.

 Ethical responsibility of high-emission countries to aid vulnerable populations.

12. Future Outlook

 Without significant action, climate change will accelerate.

 Technological breakthroughs and policy shifts can limit worst-case outcomes.

 Lifestyle changes (diet, transport, energy use) have cumulative effects.

13. Summary Table

Mitigation Renewables, CCS, reforestation Reduce GHG emissions

Adaptation Flood defenses, drought crops Cope with changes

Policy Paris Agreement, carbon pricing Coordinate action

14. Discussion Questions

1. Which is more urgent: mitigation or adaptation? Why?

2. How can we balance economic growth with emission reduction?

3. Should developed nations bear more financial responsibility for climate solutions?

4. What local climate change impacts have you observed in your region?

15. Conclusion

Climate change is one of the defining challenges of the 21st century. Its causes are well-understood,
its impacts are already being felt, and the solutions are within reach — but they require
unprecedented global cooperation. From technological innovation to lifestyle choices, every level of
society has a role to play in steering the planet toward a sustainable future.