Global Warming and Carbon Reduction

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1Summary 重點摘要

Greenhouse gases trap heat, making the Earth hotter like being wrapped in a blanket; burning fossil fuels and cutting down forests raise carbon dioxide, bringing melting ice, rising seas and extreme weather. Saving electricity, green travel, planting trees and wasting no food all shrink our carbon footprint.

2Vocabulary cards Vocabulary

3Step by step Steps

1. Step 1: Understand the greenhouse effectExample: greenhouse gases act like a blanket at night — they let sunlight into the atmosphere and hold in the heat that the ground gives off, so the difference between day and night temperatures stays small. Scientists estimate that without an atmosphere the Earth's average temperature would be about minus eighteen degrees Celsius; a moderate greenhouse effect makes the Earth liveable. The problem is that human activities add too many greenhouse gases — the blanket grows too thick and the Earth runs a fever. Common greenhouse gases include methane besides carbon dioxide; cattle release methane during digestion, so wasting less food also cuts emissions.
2. Step 2: Know where carbon dioxide comes fromExample: burning one tonne of coal releases more than two tonnes of carbon dioxide, because the carbon in the coal joins with oxygen from the air and becomes heavier. Much of the electricity for our lights and air conditioners comes from plants like these, so saving electricity really does cut power-plant emissions. Power generation, transport and manufacturing are the three main sources of carbon emissions, and carbon reduction must start from these areas. A common mistake is thinking only factories emit carbon dioxide; power plants supply the appliances at home, so using electricity indirectly creates emissions too.
3. Step 3: Compare emissions of travel choicesExample: a car emits about 2.3 kilograms of carbon dioxide for every litre of petrol it burns; on a bus the whole vehicle's emissions are shared among dozens of passengers, so each person's average share is far smaller, while walking and cycling burn no fuel at all. Before setting out, ask two questions: how far is it, and does public transport go there directly? Turning emission counting into a habit makes low-carbon choices natural. Tests may ask for comparison: for the same journey, driving alone in a private car emits several times as much as taking the bus; sharing a car with classmates who live along the way also cuts emissions.
4. Step 4: See how forests absorb carbonExample: a mature tree absorbs about 22 kilograms of carbon dioxide each year, using photosynthesis to store the carbon in its trunk and roots. Cutting down a forest loses the trees that absorb carbon and at the same time adds the carbon released when wood is burned or rots — one loss and one gain that together greatly affect the climate. Planting trees and protecting forests are therefore an important part of carbon reduction for every country, an action every citizen can support. Tests often include calculation: five mature trees absorb about 110 kilograms of carbon dioxide a year, that is 22 times 5; circle the per-tree figure first, then multiply by the number of trees.
5. Step 5: Learn the real effects of warmingExample: melting glaciers and the Greenland ice sheet raise sea levels, and some low-lying Pacific island nations face being swallowed by the sea; heatwaves and storms ruin crops and push food prices up; a warmer ocean bleaches coral and shrinks fish catches. Global warming is not a distant scientific term but a real problem for food, water and homes, which is why countries have signed agreements to face it together. When answering questions about effects, list them by category — ocean, farming and homes — with one example each, and the answer will be complete and well organised.
6. Step 6: Cut carbon at homeExample: raising the air conditioner by one degree, switching off lights when leaving a room, and choosing appliances with a grade-1 energy label save a remarkable amount of electricity and emissions in a year — a grade-1 fridge usually uses about thirty percent less power than a grade-3 one. Household electricity forms an important share of a city's carbon emissions, and reduction need not wait for adults: pupils can start with small acts like switching off lights and unplugging chargers, and small amounts add up. Always ask an adult before unplugging anything — safety comes first; do not overfill the fridge, because leaving room for air to circulate saves power too.
7. Step 7: Build low-carbon habitsExample: walking or cycling to school, bringing your own shopping bag, and finishing every grain of rice are all carbon-cutting actions possible every day. If one person cuts one kilogram of carbon emissions a day, more than seven million people in Hong Kong together save over 2.7 million tonnes a year. Living a low-carbon life is not a hardship but a habit of choice: before every purchase and every journey, first think of the effect on the planet. Check your own low-carbon actions each week by recording how often you switch off lights and bring your own bag; a visible record is the best help for keeping habits going.

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8Recap Recap

• Greenhouse gases let sunlight in and trap heat; a moderate effect keeps Earth liveable, but too much raises the temperature.
• Burning fossil fuels and clearing forests have raised carbon dioxide from about 280 to more than 420 parts per million since the Industrial Revolution.
• Warming brings rising seas, extreme weather, fewer species and food problems that affect everyone.
• The carbon footprint measures our greenhouse gas emissions; saving power, green travel and wasting no food all cut carbon.
• Hong Kong aims to be carbon neutral by 2050, a task for government and citizens together.