--- title: "Climate change gases, impact and mitigation" subject: "Technology, Environment and Society" chapter: 6 key: "semester_7/technology_environment_and_society:cc-gases-impact-mitigation" source: https://www.bctengineer.com/q/semester_7/technology_environment_and_society/cc-gases-impact-mitigation site: BCT Engineering --- # Climate change gases, impact and mitigation Technology, Environment and Society · Chapter 6: Climate Change - Asked in: 2075 Asoj, 8 marks - Video: [Greenhouse effect and greenhouse gases | High school biology | Khan Academy](https://www.youtube.com/watch?v=YpfxiDktSoI) — Khan Academy - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/technology_environment_and_society/cc-gases-impact-mitigation - Whole chapter: https://www.bctengineer.com/md/semester_7/technology_environment_and_society/chapter-6 ## Question What are climate change gases? Write down the probable impact and mitigation measures of the climate change. ## Short answer Climate change gases are greenhouse gases that absorb and re-emit Earth's infrared heat; key ones are CO2, methane, N2O, halocarbons and SF6. Impacts include heat waves, glacier melting and GLOFs, sea-level rise, erratic rainfall, crop failure, water scarcity, disease spread, biodiversity loss, ocean acidification and economic damage. Mitigation: clean energy, energy efficiency, clean transport, forest protection, sustainable agriculture, waste management, industry improvements, carbon pricing and lifestyle change, plus adaptation. ## Answer **Climate change gases** (greenhouse gases, GHGs) are gases in the atmosphere that absorb and re-emit long-wave (infrared) heat radiated by the Earth. Their increase due to human activity strengthens the greenhouse effect and causes global warming and climate change. | Gas | Main sources | GWP (100 yr, IPCC AR5) | Lifetime | |---|---|---|---| | Carbon dioxide (CO₂) | Burning coal, oil, gas; deforestation; cement | 1 | Centuries | | Methane (CH₄) | Paddy fields, livestock, landfills, gas leaks | 28 | ~12 years | | Nitrous oxide (N₂O) | Nitrogen fertilisers, manure, burning | 265 | ~120 years | | CFCs / HCFCs / HFCs | Refrigerators, ACs, aerosols, foams | Thousands | Decades–centuries | | Sulphur hexafluoride (SF₆) | Switchgear insulation | ~23,500 | ~3,200 years | | Water vapour (H₂O) | Evaporation (feedback, not directly emitted) | – | Days | | Tropospheric ozone (O₃) | Formed from NOₓ and VOCs from vehicles | – | Weeks | CO₂ contributes the largest share of warming because of its quantity; methane and N₂O are much stronger per kg; halocarbons are both GHGs and ozone-depleting. #### Probable impacts of climate change 1. **Rise in temperature and heat waves:** more extreme hot days, heat stress on people and animals. 2. **Melting of glaciers and ice sheets:** Himalayan glaciers retreat; formation of glacial lakes and risk of **GLOF** (glacial lake outburst floods). Long term, rivers fed by snow lose dry-season flow. 3. **Sea level rise:** thermal expansion and ice melt flood low-lying coasts and islands (Maldives, Bangladesh). 4. **Changed rainfall:** heavier floods in some areas, longer droughts in others; erratic monsoon. 5. **Agriculture and food security:** lower yields, new pests, shifting crop zones. 6. **Water scarcity:** springs dry up, groundwater falls. 7. **Health:** spread of malaria, dengue, cholera; heat-related deaths; malnutrition. 8. **Biodiversity loss:** species migrate upward or become extinct; coral bleaching; forest fires. 9. **Economic loss:** damage to roads, hydropower and settlements; poverty and climate migration. 10. **Ocean acidification:** CO₂ dissolved in the sea harms shellfish and coral. #### Mitigation measures Mitigation means reducing GHG emissions or increasing their removal (sinks). - **Clean energy:** expand hydropower, solar, wind and micro-hydro; phase down coal, oil and gas. - **Energy efficiency:** LED lights, efficient motors, better building insulation, energy audits in industry. - **Clean transport:** electric vehicles and electric public transport, cable cars, non-motorised transport (cycling, walking). - **Forests and land:** stop deforestation, plant trees, community forestry, REDD+ (Reducing Emissions from Deforestation and Forest Degradation). - **Agriculture:** less chemical fertiliser, organic farming, better manure handling, improved paddy water management. - **Waste:** reduce, reuse, recycle; capture landfill methane; biogas from kitchen and animal waste. - **Industry:** cleaner production, replacing old brick kilns with zig-zag kilns, low-carbon cement. - **Carbon pricing and policy:** carbon tax, emissions trading, removing fossil fuel subsidies. - **Awareness and lifestyle:** saving energy, less food waste, using public transport. Along with mitigation, countries also need **adaptation** (e.g. GLOF early warning, drought-resistant crops, climate-proof infrastructure) because some warming is already locked in. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What makes a gas a climate change (greenhouse) gas? A. It is poisonous to humans B. It absorbs and re-emits long-wave infrared heat radiated by the Earth C. It reflects incoming sunlight away D. It is heavier than air Answer: B. GHGs absorb and re-emit infrared heat, strengthening the greenhouse effect when their concentration increases. (Key point: Definition of GHG) 2. Why does CO2 contribute the largest share of warming although methane and N2O are stronger per kg? A. CO2 has a higher GWP than methane B. CO2 is emitted in much larger quantity C. CO2 has a lifetime of only days D. CO2 is not man-made Answer: B. CO2 has GWP 1 but its huge quantity (and centuries-long lifetime) makes it the biggest contributor. (Key point: CO2 versus other gases) 3. What causes sea level rise as an impact of climate change? A. Thermal expansion of seawater and melting of ice B. Only increased rainfall on land C. Ocean acidification D. Increased evaporation only Answer: A. Warmer water expands and ice sheets and glaciers melt, flooding low-lying coasts and islands like the Maldives and Bangladesh. (Key point: Sea level rise) 4. What is the difference between mitigation and adaptation? A. Mitigation is adjusting to impacts; adaptation reduces emissions B. They mean the same thing C. Mitigation reduces GHG emissions or increases sinks; adaptation copes with impacts already locked in D. Adaptation is only for developed countries Answer: C. Mitigation tackles the cause (emissions/sinks); adaptation (e.g. GLOF warning, drought-resistant crops) copes with unavoidable warming. 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