---
title: "Global warming: meaning, causes, consequences"
subject: "Engineering Chemistry"
chapter: 3
key: "semester_2/engineering_chemistry:global-warming-causes-consequences"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/global-warming-causes-consequences
site: BCT Engineering
---

# Global warming: meaning, causes, consequences

Engineering Chemistry · Chapter 3: Environmental Chemistry

- Asked in: 2068 Bhadra, 3 marks
- Video: [Understand Global Warming & Climate Change | Greenhouse Effect | Causes, Effects, and Solutions](https://www.youtube.com/watch?v=nWPlf9ZpHBI) — Toppscholars
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/global-warming-causes-consequences
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-3

## Question

What is meant by global warming? Give its causes and consequences.

## Short answer

Global warming is the gradual rise in Earth's average temperature from enhanced greenhouse effect by CO2, CH4, N2O, CFCs. Causes: fossil fuel burning, deforestation, agriculture. Consequences: glacier melt, sea-level rise, extreme weather, crop failures, biodiversity loss, and spread of diseases.

## Answer

#### Meaning
**Global warming** is the gradual rise of the average temperature of the earth's surface and lower atmosphere due to the increased concentration of greenhouse gases (CO₂, CH₄, N₂O, CFCs, water vapour, O₃). The rise has been about 1.1 °C since the pre-industrial era.

#### Causes
| Gas | Main sources |
|---|---|
| CO₂ (about 60 % of the effect) | Burning of coal, oil, wood; deforestation; cement industry |
| CH₄ | Paddy fields, cattle (rumination), landfills, natural gas leaks, wetlands |
| N₂O | Nitrogenous fertilisers, burning of biomass, nitric acid industry |
| CFCs | Refrigerators, air conditioners, aerosols, foam |
| O₃ (troposphere) | Photochemical reactions of vehicle exhaust (NOx + hydrocarbons) |

The main human causes are the burning of fossil fuels, deforestation, agriculture (paddy and cattle) and use of fertilisers and CFCs.

#### Consequences
- Melting of glaciers and polar ice, and rise of sea level (flooding of coastal regions, island nations). In Nepal, Himalayan glaciers are retreating and glacial lake outburst floods are a threat.
- Changed rainfall patterns: more floods, droughts, storms and heat waves.
- Loss of crop yield, food and water shortage; shifting of climatic zones.
- Extinction of species and loss of biodiversity; coral bleaching.
- Spread of diseases such as malaria and dengue to new areas.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Global warming is
   A. The gradual rise of average earth surface and lower atmosphere temperature due to increased greenhouse gases
   B. Cooling of the stratosphere by ozone
   C. A sudden temperature fluctuation each day
   D. Rise in sea salt
   Answer: A. Caused by increased GHG concentrations. (Key point: Meaning)

2. CO2 contributes about what share of the enhanced greenhouse effect?
   A. About 6%
   B. About 60%
   C. About 20%
   D. About 95%
   Answer: B. CO2 is the largest contributor, about 60%. (Key point: CO2 share)

3. Which are main sources of methane?
   A. Nitrogenous fertilisers and nitric acid industry
   B. Cement industry and deforestation
   C. Paddy fields, cattle, landfills, natural gas leaks and wetlands
   D. Refrigerators and aerosols
   Answer: C. These are the CH4 sources; the others describe N2O, CO2 and CFCs. (Key point: CH4 sources)

4. Which is a consequence?
   A. Decreased sea level
   B. More polar ice
   C. Reduced disease spread
   D. Sea-level rise, changed rainfall, species loss, spread of malaria and dengue
   Answer: D. Warming has wide effects. (Key point: Consequence)

## Related in Engineering Chemistry

- [Global warming: causes, consequences, remedies](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Aglobal-warming) — Engineering Chemistry, chapter 3, asked 2×
- [Short note: Global warming](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Aglobal-warming-note) — Engineering Chemistry, chapter 3

## Related in other subjects

- [Global environmental issues: causes and consequences](https://www.bctengineer.com/question.md?key=semester_7%2Ftechnology_environment_and_society%3Aglobal-env-issues-causes) — Technology, Environment and Society, chapter 4
- [Global warming and greenhouse gases](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Aglobal-warming-ghg-climate) — Energy Environment and Society, chapter 4
- [Research article on global warming](https://www.bctengineer.com/question.md?key=semester_5%2Fcommunication_english%3Aresearch-article-global-warming) — Communication English, chapter 10
- [Global warming and international efforts](https://www.bctengineer.com/question.md?key=semester_7%2Ftechnology_environment_and_society%3Aglobal-warming-international) — Technology, Environment and Society, chapter 6