Pollution

What is a greenhouse gas?

A gas in the atmosphere that absorbs and re-emits infrared radiation, trapping heat and warming the Earth.

What is the greenhouse effect?

The process where greenhouse gases trap some heat energy in Earth’s atmosphere, keeping the planet warm enough for life.

Is the greenhouse effect harmful?

No. The natural greenhouse effect is necessary for life. The problem is the enhanced greenhouse effect caused by increased greenhouse gas levels.

What is the enhanced greenhouse effect?

The increased trapping of heat caused by higher concentrations of greenhouse gases, leading to global warming.

What is carbon dioxide?

A greenhouse gas produced naturally and by human activities that contributes to global warming.

What are natural sources of carbon dioxide?

1. Respiration by organisms
2. Volcanic eruptions
3. Decomposition

What are human sources of carbon dioxide?

1. Burning fossil fuels (coal, oil, natural gas)
2. Deforestation
3. Industrial processes

How does burning fossil fuels increase carbon dioxide?

Carbon in the fuel reacts with oxygen during combustion, producing carbon dioxide (carbon + oxygen → carbon dioxide).

How does deforestation increase carbon dioxide?

1. Fewer trees are available to absorb CO₂ through photosynthesis.
2. Burning forests releases stored carbon as CO₂.

What are effects of increased CO₂?

1. Enhanced greenhouse effect
2. Global warming
3. Climate change
4. Rising sea levels

What is methane?

A greenhouse gas that is more effective than carbon dioxide at trapping heat, but exists in smaller amounts.

What are natural sources of methane?

1. Wetlands
2. Decomposition of organic matter

What are human sources of methane?

1. Livestock farming (digestion of animals like cattle)
2. Landfills
3. Rice farming
4. Fossil fuel extraction

Why do cows produce methane?

Microorganisms in their digestive systems break down food and release methane during digestion.

What are effects of increased methane?

1. Increases the greenhouse effect
2. Contributes to global warming

Is water vapour a greenhouse gas?

Yes. Water vapour is the most abundant natural greenhouse gas.

How does water vapour enter the atmosphere?

1. Evaporation from oceans, lakes, and rivers
2. Transpiration from plants

Why is water vapour considered a greenhouse gas?

It absorbs infrared radiation and traps heat in the atmosphere.

Why is water vapour not usually considered the main cause of modern global warming?

Because its amount in the atmosphere is mainly controlled by temperature, while humans directly increase gases like CO₂ and methane.

What is global warming?

The long-term increase in Earth’s average temperature due to increased greenhouse gases.

What are consequences of global warming?

1. Melting glaciers and ice caps
2. Rising sea levels
3. More extreme weather events
4. Changes in habitats
5. Loss of biodiversity

How does global warming cause sea levels to rise?

1. Ice sheets and glaciers melt, adding water to oceans.
2. Warmer oceans expand because water takes up more space when heated.

Memory trick for CO₂ sources

CO₂ = Combustion + Cutting trees
🔥 fossil fuels
🌳 deforestation

Memory trick for CH₄ sources

CH₄ = Cows + Compost/Landfills + Crude oil/gas extraction

Memory trick for H₂O sources

H₂O = Heat → evaporation → water vapour

Overall greenhouse gas chain of effects

Human activity → increased greenhouse gases → more heat trapped → global warming → consequences.