Climate Change – JSS3 Intermediate Science Lesson Note (Third Term)

Climate change is the long-term shift in the earth’s weather patterns and average temperatures.

• Natural changes: the earth has warmed and cooled naturally before.
• Present change: humans are now causing the earth to warm too fast.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Define climate change and state the difference between weather and climate.
2. Explain the greenhouse effect in simple steps.
3. List human activities that increase global warming.
4. Describe five effects of climate change, with examples from Nigeria.
5. Suggest ways of reducing climate change (mitigation).

What is the difference between weather and climate?

Weather is the condition of the atmosphere in a place over a short time, such as a day or a week.

Climate is the average weather of a place over a long period, usually many years.

What are the signs of climate change in Nigeria?

The signs are changes people notice over many years.

• Late rains: the rainy season does not always start when it used to.
• Intense heat: some days feel hotter than they did in the past.
• Floods and droughts: heavy rainstorms and long dry spells are more common.

What causes climate change?

Climate change has natural causes and human causes, and the human causes are the main reason for the present fast warming.

Natural causes

• Volcanic eruptions: they release ash and gases into the air.
• Changes in the sun’s energy: the amount of heat reaching the earth can vary.

Human causes

Most human causes work by adding more greenhouse gases to the air. See the greenhouse effect below.

What is the greenhouse effect?

The greenhouse effect is the trapping of heat near the earth’s surface by certain gases in the atmosphere.

• Car example: a car parked in the sun with the windows up gets hotter inside, because the glass lets sunlight in and keeps the heat from escaping.
• Atmosphere: greenhouse gases act like the glass and hold heat around the earth.
• Natural effect: a small amount keeps the earth warm enough for life.
• Problem: too much greenhouse gas traps too much heat, so the earth gets hotter.

How does the greenhouse effect happen?

1. Sunlight passes through the atmosphere and warms the earth’s surface.
2. The warm earth gives off some of this energy as heat.
3. Greenhouse gases in the air trap part of the heat.
4. The lower atmosphere becomes warmer.
5. More greenhouse gases trap more heat, so the average temperature rises (global warming).

What are the main greenhouse gases?

• Carbon dioxide (CO₂): released when fuels are burnt and when forests are destroyed.
• Methane: released by cattle, rubbish dumps and rice fields.
• Nitrous oxide: released from some fertilisers.
• Water vapour: occurs naturally in the air and also traps heat.

Which human activities increase global warming?

Human activities that release greenhouse gases or remove trees increase global warming.

• Burning fossil fuels: petrol in cars, “I-pass-my-neighbour” generators and coal in factories release CO₂, which traps heat.
• Deforestation: trees take in CO₂ and give out oxygen, so cutting or burning forests for houses or farms leaves less CO₂ being removed.
• Industrial pollution: factories burn fuel and release CO₂ and other gases into the air.
• Agriculture: cattle farming releases methane, and some fertilisers release nitrous oxide. Both trap more heat than the same amount of CO₂.
• Burning refuse: burning rubbish releases CO₂ and smoke into the air.

What are the effects of climate change?

Climate change affects land, water, food, health and living things, and does more than make days hotter.

• Flooding: ice at the poles and on mountains melts and warm sea water expands, so sea level rises. Coastal cities like Lagos then flood more easily.
• Desertification: in Northern Nigeria, heat and lack of rain dry up the land and green areas turn into desert. Farmers then find it hard to grow food.
• Extreme weather: there are very heavy rainstorms that wash away houses, and long droughts when it does not rain for months.
• Health problems: heatwaves can cause heatstroke. Mosquitoes that carry malaria like warm weather, so they spread to new areas more easily.
• Loss of biodiversity: plants and animals that cannot survive the heat or lack of water die out (extinction).

What is mitigation of climate change?

Mitigation means making the problem less severe by reducing the gases that cause warming.

We cannot stop climate change overnight, but we can slow it down.

• Switch to clean energy: solar power gives energy without releasing harmful gases, unlike petrol generators.
• Plant more trees (afforestation): every tree planted helps take CO₂ out of the air.
• Manage waste: practise the 3 R’s instead of burning rubbish.
  • Reduce: use and throw away less.
  • Reuse: use items again, such as bottles and containers.
  • Recycle: turn used materials into new products.
• Smart farming: use methods that protect the soil and do not need burning the bush every season.
• Save energy: switch off lights when you leave a room, which reduces the load on power plants.

Why should we care about climate change?

Climate change affects Nigerians directly, so it is not a “foreign” problem.

• Food prices: dry land and floods reduce harvests.
• Homes and roads: storms and rising seas damage them.
• Health: heat and disease spread affect everyone.
• Future: acting now protects the next generation.

Evaluation

1. Define climate change.
2. What is the greenhouse effect in simple terms?
3. Why is cutting down trees bad for the climate?
4. State three effects of climate change in Nigeria.
5. Name two things you can do at home to help reduce climate change.

Assignment

Write down five actions your family can take at home to reduce climate change. Beside each action, explain in one sentence how it helps.