KS3 · Chemistry

Global warming and its evidence

The gases that keep Earth warm enough for life are the same gases behind global warming. Hero or problem? By the end, you'll know how they can be both.

Build the chain

From the fuel we burn to a warmer planet

Which of these made which happen? Add a link for each arrow you think belongs, from cause to effect, then compare your web with the lesson's. Have a go before you read on — getting one the wrong way round is useful.

  1. Burning fossil fuels (coal, oil and gas)
  2. Other human activities (farming, some industry, landfill)
  3. More greenhouse gases in the atmosphere
  4. An enhanced greenhouse effect
  5. More heat trapped, warming the surface
  6. Earth's average surface temperature rises (outcome)
Add a link

No links yet.

The natural greenhouse effect

Imagine Earth with no greenhouse gases

Take every greenhouse gas out of the atmosphere — no carbon dioxide, no methane, no water vapour. What would Earth's average surface temperature be?

Your estimate

-5°C

-40°C30°C

Not the same thing

The greenhouse effectvsGlobal warming

These two terms get mixed up more than any others in this topic. Read across each row.

Focus

What it is

The greenhouse effect

A process: some gases in the atmosphere trap some of the heat, keeping Earth's surface warmer than it would be without them.

Global warming

A change: an increase in Earth's average surface temperature — the name for the recent, unusual, rapid rise.

The insight

One is a natural process. The other is a temperature going up.

Natural, or linked to us?

The greenhouse effect

Natural. It happens because greenhouse gases such as carbon dioxide, methane and water vapour are in the atmosphere.

Global warming

Most scientists agree it is being caused by emissions from human activities enhancing the greenhouse effect.

What it does to Earth's average surface temperature

The greenhouse effect

Keeps it much warmer than it would be otherwise — at a level that can sustain life.

Global warming

Pushes it up — unusually and rapidly.

The evidence

What do the temperature records actually show?

Weather stations across the globe measure temperature. Put their records together and you can track Earth's average surface temperature over time. They show that for almost 2,000 years it stayed within a narrow range — about 0.3 °C up or down. Then, over the last century or so, it rose quickly to well over 1 °C higher than its 1850–1900 average.

Which idea is closest to what you think these records tell us?
How sure are you?

Predict, then check

This is the step people skip. Commit to an answer first.

Over the same period of about 100 years, greenhouse gas emissions from human activities rose rapidly — and so did Earth's average surface temperature. Does that pattern, on its own, prove the emissions caused the warming?

Where the gases come from

Burning fossil fuels — or not?

Pick an activity, then choose its group. Where does its greenhouse gas come from?

Still to sort

Releases carbon dioxide by burning fossil fuels (0)

Coal, oil and gas — and fuels such as petrol, diesel and aviation fuel.

Where the line is: Ask: is a fuel being burned to make this happen? If yes, it belongs here.

Releases greenhouse gases without burning fossil fuels (0)

The activity itself releases the gas.

Where the line is: No fuel is being burned: the gas comes from an animal digesting, waste rotting, or a product being made.

7 of 7 still to sort.

Every one of these releases greenhouse gases. Sort each by HOW.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

The greenhouse effect is natural. Global warming is what happens when human activity enhances it.

What you need to know

  • What the greenhouse effect is, and why Earth needs it
  • What the temperature evidence for global warming shows
  • How human activities are linked to global warming — and why a pattern in the data isn't proof on its own

The big picture

Some gases in the atmosphere trap heat and keep Earth warm enough for life: that is the natural greenhouse effect. Global warming is the recent, unusual, rapid rise in Earth's average surface temperature. Temperature data show the rise; a correlation with human emissions shows a pattern; and the greenhouse effect is the mechanism that links the two.

Key points

1The greenhouse effect is natural: the Sun warms Earth and its atmosphere, a lot of that heat is radiated into space, and greenhouse gases (carbon dioxide, methane, water vapour) trap some of it, warming the surface.
2Without greenhouse gases Earth's average surface temperature would be about −20 °C; with them it is about +15 °C — warm enough to sustain life.
3Global warming is an increase in Earth's average surface temperature. The recent, unusual, rapid increase is called global warming — it is not the same thing as the greenhouse effect.
4Temperature data from weather stations across the globe are observations and measurements. They show a narrow range (about ±0.3 °C) for almost 2,000 years, then a rapid rise over the last century or so to well over 1 °C above the 1850–1900 average.
5Emissions and temperature both rose over the same period: that is a correlation, and a correlation alone doesn't prove cause. The mechanism is the greenhouse effect — more greenhouse gases enhance it, trapping more heat and raising the average surface temperature.
6Burning fossil fuels in power stations and transport releases carbon dioxide. Industrial processes, farming (including cattle) and landfill release greenhouse gases without burning fossil fuels.

Worked example

Problem

Explain how keeping large herds of cattle can add to global warming.

⚠ Watch out

Treating 'the greenhouse effect' and 'global warming' as the same thing. The greenhouse effect is a natural process that keeps Earth warm enough for life; global warming is the recent rise in average surface temperature, which most scientists agree is caused by human emissions enhancing that effect.

🧠

Memory hook

Blanket, then extra blankets. The greenhouse effect is the blanket that keeps Earth warm enough for life; global warming is what happens when we keep piling more on. (It's only a picture: the 'blanket' is gases trapping heat, not a solid layer.)

✓

Check yourself

Someone says: 'Emissions and temperature both went up, so that proves it.' What is that pattern called, why isn't it enough on its own, and what idea actually links the two?

Flashcards

(14)
What is the greenhouse effect?
The effect of some gases in the atmosphere that keep Earth's surface warmer than it would be without them, by trapping some of the heat.
Name three greenhouse gases.
Carbon dioxide, methane and water vapour.
About how warm is Earth's average surface with greenhouse gases, and without them?
With them about +15 °C; without them about −20 °C.
Why is the greenhouse effect described as natural and necessary?
It is a natural process that keeps Earth's average surface temperature at a level that can sustain life.
What is global warming?
An increase in Earth's average surface temperature — the name for the recent, unusual, rapid rise.
Where does the evidence for global warming come from?
Temperature data from weather stations across the globe — observations and measurements, not opinions.
What did Earth's average surface temperature do for almost 2,000 years?
It stayed within a narrow range — about 0.3 °C up or down.
What has the average surface temperature done over the last century or so?
Risen unusually and rapidly, to well over 1 °C higher than the 1850–1900 average.
What is a correlation?
A pattern in data showing that one factor changes as another factor changes.
Does a correlation prove that one thing causes another?
No. You also need a mechanism that explains how one leads to the other.
What does adding more greenhouse gases do to the greenhouse effect?
It enhances it, so more heat is trapped and Earth's average surface temperature rises.
Which fuels are fossil fuels, and what does burning them release?
Coal, oil and gas. Burning them releases carbon dioxide, a greenhouse gas.
Give two uses of fossil fuels that release carbon dioxide.
Power stations generating electricity and heat; transport such as cars, lorries, buses, trains, boats and aeroplanes.
Name three sources of greenhouse gases that don't involve burning fossil fuels.
Industrial processes (making fertilisers, clothing, paint, bricks), farming (fertilisers and cattle) and waste decomposing in landfill.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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How this lesson was checked. This KS3 Chemistrylesson was published through Lightbulb Learning's human-designed editorial process — the educational standards, accuracy rules and publication checks it must pass were authored and approved by Philip Halpin. It passed subject-specific assessment, automated educational checks and technical publication verification before going live (publication checks completed 29 September 2026). Published pages are monitored, human spot-checking is ongoing across the lesson library, and anything found wrong is corrected or withdrawn. How our lessons are made and checked. Spotted a mistake? Email hello@lightbulblearning.co and we'll review it.