Global Warming
The rise in the Earth's average surface temperature caused by greenhouse gases
In one minute
Global warming is the long-term rise in the Earth's average surface temperature. Gases such as carbon dioxide and methane trap heat in the air, and human activity has added a great deal of them.
It is the main driver of climate change. Exams ask for causes, effects and the treaty response.
Exam focus
- Frequency: Rarely asked
- Usually asked as: Short answer (4 to 6 marks)
Legal provision
India has no single Act on global warming. The law reaches it through these sources.
- Section 2(a), Air (Prevention and Control of Pollution) Act, 1981: an "air pollutant" is any solid, liquid or gaseous substance (including noise) present in the atmosphere in such concentration as may be or tend to be injurious to human beings, other living creatures, plants, property or environment.
- Section 3(1), Environment (Protection) Act, 1986: the Central Government can take all measures it thinks necessary to protect the environment and control pollution.
- UN Framework Convention on Climate Change, 1992, Kyoto Protocol, 1997 and Paris Agreement: the treaties that set the global response.
- Article 2, Paris Agreement: the goal of holding the rise in global average temperature well below 2 degrees Celsius above pre-industrial levels. Efforts continue to limit it to 1.5 degrees.
Meaning and definition
Global warming is the long-term rise in the Earth's average surface temperature, caused by the build-up of greenhouse gases in the atmosphere. A greenhouse gas is a gas that traps heat. The Earth needs some of them to stay warm enough for life. The problem is the extra amount.
- 1. Sunlight reaches the Earth and warms the surface.
- 2. The surface sends heat back towards space.
- 3. Greenhouse gases in the air trap part of that heat.
- 4. Human activity adds more gases, so more heat is trapped.
- 5. ResultThe average temperature of the surface rises.
Detailed explanation
Step 1: the main gases
The main greenhouse gases are carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O) and CFCs. Water vapour also traps heat.
Step 2: causes
- Burning fossil fuels: coal, oil and gas release large amounts of carbon dioxide.
- Deforestation: fewer trees means less carbon dioxide taken in.
- Industry: factories release gases and pollutants.
- Farming: cattle and rice fields give off methane, and fertilisers release nitrous oxide.
- Cities and transport: vehicle fuel and construction add to the carbon footprint.
Example. A thermal power station in Chandrapur burns coal and sends carbon dioxide into the air. The trucks that carry the coal add more. Together they raise the amount of heat-trapping gas.
Step 3: effects
- More heatwaves, droughts, floods and storms.
- Melting glaciers and ice caps, and rising sea levels that threaten coasts.
- Loss of species that cannot adapt.
- Pressure on crops and food supply.
- More heat illness and spread of some diseases.
- Acidification from the extra carbon dioxide the sea absorbs, which harms coral and shellfish.
Step 4: the legal response
Because every country's gases mix in one atmosphere, the response is mainly by treaty. The UNFCCC (1992) set the framework. The Kyoto Protocol (1997) and the Paris Agreement added the commitments. The Paris Agreement states a goal of holding the rise well below 2 degrees Celsius and pursuing 1.5 degrees (Article 2). Inside India, the Air Act and the 1986 Act can address gases that harm the environment, but there is no separate warming statute.
Don't confuse: global warming and the greenhouse effect
| Point | Greenhouse effect | Global warming |
|---|---|---|
| Meaning | The natural trapping of heat by gases, which keeps the Earth warm | The extra rise in temperature when more gas is added |
| Harmful? | No. Life needs it. | Yes, when the rise is fast and large |
Inside the concept. The rise in average temperature recorded over several decades because of added carbon dioxide is global warming.
Just outside it. The natural warming of the Earth's surface by water vapour and normal levels of carbon dioxide is the greenhouse effect itself.
Common mistakes
- Writing that greenhouse gases are harmful in every amount. Some are needed for life.
- Mixing global warming with ozone depletion. They are different problems.
- Using global warming and climate change as the same term. Climate change is the wider result.
- Stating that India has a dedicated statute on global warming. It does not.
Leading case laws
No case in the syllabus list turns only on global warming. Indian courts have treated climate harm as part of the right to a healthy environment, as covered in the note on climate justice.
How to write this answer in the exam
5-mark answer
- Meaning: rise in average surface temperature.
- Greenhouse gases named.
- Main causes.
- Main effects.
10-mark answer
- Meaning and the greenhouse effect.
- Gases and sources.
- Causes grouped under fuels, forests, industry, farming, cities.
- Effects on weather, sea, species, food, health.
- Treaty response: UNFCCC, Kyoto, Paris, with the 1.5 degree goal.
- Indian law: Air Act, 1981 and the 1986 Act.
Key points to remember
- Global warming: long-term rise in average surface temperature.
- Gases: carbon dioxide, methane, nitrous oxide, CFCs, water vapour.
- Causes: fossil fuels, deforestation, industry, farming, cities.
- Paris Agreement, Article 2: well below 2 degrees, efforts towards 1.5 degrees.
- No separate Indian Act. The Air Act and the 1986 Act apply to harmful gases.
Quick self-test
1. Name three greenhouse gases.
Any three of carbon dioxide, methane, nitrous oxide, CFCs and water vapour.
2. What temperature goal does Article 2 of the Paris Agreement state?
Holding the rise well below 2 degrees Celsius and pursuing efforts to limit it to 1.5 degrees.
3. Is the greenhouse effect itself harmful?
No. It is natural and keeps the Earth warm. The harm comes from the extra gases.