- 2071 Shrawan · 2 marks
- Year not given
Global warming and greenhouse gases
Short answer
Global warming is the long-term rise in Earth's average temperature due to increased greenhouse gases from human activities. Key GHGs are CO₂, CH₄, N₂O, and CFCs. Effects include rising temperatures, glacier melt, sea level rise, extreme weather, threats to agriculture, biodiversity loss, and health impacts.
Write a short note on global warming. What are greenhouse gases and what are the effects of climate change? Describe in brief.
Global warming
Global warming is the long-term rise in the average temperature of the earth's atmosphere and oceans caused mainly by human activity that increases greenhouse gases. The earth has warmed by about 1.2–1.3 °C compared with pre-industrial (1850–1900) levels, and 2024 was the first calendar year more than 1.5 °C above that level (WMO and Copernicus). The cause is the enhanced greenhouse effect: gases trap outgoing infrared radiation from the earth.
Sun --> short-wave --> Earth surface
Earth --> infrared --> [GHG layer] --> trapped,
re-radiated down => warming
Greenhouse gases (GHGs)
Gases that absorb infrared radiation and warm the atmosphere:
| Gas | Main source | GWP (100 yr, approx.) |
|---|---|---|
| Carbon dioxide (CO₂) | Burning fossil fuels, deforestation, cement | 1 |
| Methane (CH₄) | Livestock, rice paddies, landfill, gas leaks | 28 |
| Nitrous oxide (N₂O) | Fertiliser, burning | 265 |
| CFCs / HFCs | Refrigerants, aerosols | 1,000–10,000+ |
| SF₆ | Electrical switchgear | 23,500 |
| Water vapour, ozone | Natural / secondary | - |
Effects of climate change
- Rising temperatures and heat waves.
- Melting of glaciers and ice caps: Himalayan glaciers retreat fast, causing GLOF risk and, in the long run, reduced river flow that affects hydropower.
- Sea level rise, flooding of coastal areas.
- Changing rainfall: more floods, landslides and droughts (Nepal has seen extreme monsoon events).
- Threat to agriculture, food and water security.
- Loss of biodiversity and changes in ecosystems; ocean acidification.
- Health effects: vector-borne diseases, heat stress.
- Economic loss and migration.
✓ Answer checked by Claude Opus 5.5 (high effort)
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