Which of these is a greenhouse gas?

methane. Carbon dioxide, water vapour and methane are greenhouse gases.

Which activity releases the most carbon dioxide?

burning fossil fuels. Combustion of coal, oil and gas is the largest source.

Which gas is released by the digestion of cattle?

methane. Cattle and rice fields are large sources of methane.

How does deforestation increase carbon dioxide in the atmosphere?

fewer trees remove carbon dioxide by photosynthesis. Trees are a sink for carbon dioxide.

Why does making cement release carbon dioxide?

calcium carbonate is heated and gives off carbon dioxide. Limestone breaks down into lime and carbon dioxide.

What is the enhanced greenhouse effect?

the extra warming caused by increased greenhouse gases. "Enhanced" means increased beyond the natural effect.

Greenhouse gases and global warming · Cambridge IGCSE Environmental Management

In plain words

The natural blanket of gases round the Earth has been getting thicker for two hundred years, and people are the reason. This unit is about which gases, where they come from, and how extra gas turns into extra heat.

9 things to know

A greenhouse gas is a gas that absorbs radiation and emits the energy as thermal (heat) energy.
Three greenhouse gases are carbon dioxide (CO₂), water vapour (H₂O) and methane (CH₄).
Combustion of fossil fuels releases carbon dioxide. This is the largest source.
Agriculture releases methane: from the digestion of cattle, from the decomposition of manure, and from rice fields.
Deforestation reduces the removal of carbon dioxide by photosynthesis, because there are fewer trees to take it in.
Changes in land use: draining wetlands releases methane.
Cement manufacture: calcium carbonate (limestone) is heated to produce calcium oxide (lime), and carbon dioxide is released.
An increasing human population, and increased energy use, release more carbon dioxide.
The enhanced greenhouse effect: the extra greenhouse gases absorb more radiation, so more heat is held in the atmosphere. This causes global warming, a rise in the Earth's average temperature. Global warming can result in climate change.

Worked example

Explain how cutting down a forest and burning the wood increases the amount of carbon dioxide in the atmosphere in two ways.

Burning the wood is combustion, which releases the carbon stored in the trees as carbon dioxide.
With the trees gone, less photosynthesis takes place, so less carbon dioxide is removed from the air.
One change adds carbon dioxide. The other stops it being taken out.

Tips and tricks

Methane comes from cattle, manure, rice fields and drained wetlands. Carbon dioxide comes from burning, cement and the loss of forest. Match the gas to the source.
Keep the chain in order: more greenhouse gases, enhanced greenhouse effect, global warming, climate change. They are four different things.

6 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Greenhouse gases and global warming: 6 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

Which of these is a greenhouse gas?
- nitrogen
- oxygen
- methane (the answer)
- argon
Carbon dioxide, water vapour and methane are greenhouse gases.
Which activity releases the most carbon dioxide?
- growing rice
- keeping cattle
- draining wetlands
- burning fossil fuels (the answer)
Combustion of coal, oil and gas is the largest source.
Which gas is released by the digestion of cattle?
- methane (the answer)
- carbon dioxide
- sulfur dioxide
- oxygen
Cattle and rice fields are large sources of methane.
How does deforestation increase carbon dioxide in the atmosphere?
- trees release methane when they grow
- fewer trees remove carbon dioxide by photosynthesis (the answer)
- soil absorbs more oxygen
- more rain falls
Trees are a sink for carbon dioxide.
Why does making cement release carbon dioxide?
- calcium carbonate is heated and gives off carbon dioxide (the answer)
- cement absorbs oxygen
- cement is made from coal
- cement is made from methane
Limestone breaks down into lime and carbon dioxide.
What is the enhanced greenhouse effect?Stretch
- the natural warming that makes life possible
- the thinning of the ozone layer
- the cooling caused by volcanic ash
- the extra warming caused by increased greenhouse gases (the answer)
"Enhanced" means increased beyond the natural effect.

6 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

3 questions, 8 marks. Write your answers on paper, then check them.

Greenhouse gases and global warming

Cambridge IGCSE Environmental Management 0680 · 8 marks · papermunch.org

Name ______________________________ Date ______________

Define the term greenhouse gas.[2]
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A gas that absorbs radiation and emits the energy as thermal (heat) energy.
I got this one
State three sources of methane from human activity.[3]
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Any three: digestion by cattle; decomposition of manure; rice fields; drainage of wetlands.
I got this one
Explain how increased concentrations of greenhouse gases lead to climate change.[3]
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The extra gases absorb more radiation, which is the enhanced greenhouse effect. More heat is held in the atmosphere, so the Earth's average temperature rises: global warming. The warming changes long-term weather patterns, which is climate change.
I got this one

Answers: Greenhouse gases and global warming

1. A gas that absorbs radiation and emits the energy as thermal (heat) energy.
2. Any three: digestion by cattle; decomposition of manure; rice fields; drainage of wetlands.
3. The extra gases absorb more radiation, which is the enhanced greenhouse effect. More heat is held in the atmosphere, so the Earth's average temperature rises: global warming. The warming changes long-term weather patterns, which is climate change.