Key Stage 3 geography · Physical geography

KS3 climate change from the Ice Age to today: a parent guide

At Key Stage 3, pupils study how the climate has changed from the last Ice Age to the present day. They meet the natural causes of change, the evidence scientists use to reconstruct past climates, and the way human activity since the industrial period has added to the greenhouse effect. It matters because pupils will make decisions about energy, travel and food as adults, and they need to separate what is well established from what is opinion.

Climate change from the Ice Age, explained

Earth’s climate has never been fixed. Over the last two and a half million years or so it has swung between cold glacial periods, often called ice ages, and warmer interglacial periods. At the coldest point of the most recent glacial period, about 20,000 years ago, thick ice sheets covered most of Scotland, Wales and northern England, and sea levels were well over 100 metres lower than today, so Britain was joined to mainland Europe. The ice then retreated, and the warm period we live in began about 11,700 years ago.

Pupils learn that natural causes drove these changes. Small, regular shifts in the shape of Earth’s orbit, the tilt of its axis and the wobble of its spin alter how much sunlight reaches different parts of the planet, and over tens of thousands of years this pushes the climate in and out of glacial periods. Large volcanic eruptions can cool the planet for a year or two by putting gas and dust high into the atmosphere, where they block some sunlight, and changes in the sun’s output play a smaller part. Within the last thousand years there were also smaller shifts, such as a warmer spell in medieval times and the cooler period often called the Little Ice Age, when the River Thames sometimes froze solid enough for fairs.

How do we know any of this? Pupils study the evidence. Ice cores drilled from Antarctica and Greenland hold layers of snow that built up year by year and trapped tiny bubbles of ancient air, so scientists can measure past carbon dioxide and estimate past temperatures; the longest cores go back around 800,000 years. Tree rings, pollen preserved in peat and lake mud, fossils, and landforms left by ice give more clues. Since the mid-1800s there have also been thermometer readings from enough places to estimate a global average, and for recent decades satellite data. Good geographers look at where each kind of evidence is strong and where it has limits.

The final part of the story is recent change. The greenhouse effect is natural and necessary: gases such as carbon dioxide, methane and water vapour trap some of the heat leaving Earth, keeping the planet far warmer than it would otherwise be. Since the industrial period began, burning coal, oil and gas, clearing forests and farming have raised the amounts of carbon dioxide and methane in the air. Carbon dioxide has risen from about 280 parts per million before industrialisation to over 420 today, and the global average temperature is now more than 1°C higher than in the late 1800s. Pupils learn that scientific bodies around the world agree that human activity is the main cause of the warming seen since the mid-1900s.

Because the programme of study asks pupils to understand how human and physical processes interact, lessons also cover what changes in climate can mean for people and what can be done. Mitigation means reducing emissions, for example through renewable energy or less wasteful transport. Adaptation means living with the changes, such as building flood defences or growing different crops. Schools choose their own place-based examples, such as a low-lying island, a glacier that is retreating or a UK flood-prone town. It is a topic where teachers aim to present evidence calmly and let pupils reason from it.

Words your child will hear

Glacial period: A long cold phase of Earth’s history when ice sheets spread across large areas. Often called an ice age.
Interglacial: A warmer gap between glacial periods. We are in one now.
Greenhouse effect: The trapping of some heat by gases in the atmosphere, which keeps Earth warm enough for life.
Ice core: A long tube of ice drilled from an ice sheet that holds layers of snow and trapped air from past years.
Fossil fuels: Coal, oil and natural gas, formed from ancient living things, which release carbon dioxide when burned.
Mitigation: Action to reduce the causes of climate change, such as cutting greenhouse gas emissions.
Adaptation: Action to cope with climate change, such as building flood defences.

What the National Curriculum says

The programme of study for Key Stage 3 says:

Pupils should be taught to understand, through the use of detailed place-based exemplars at a variety of scales, the key processes in physical and human geography
Physical geography relating to: geological timescales and plate tectonics; rocks, weathering and soils; weather and climate, including the change in climate from the Ice Age to the present; and glaciation, hydrology and coasts
Pupils should be taught to understand how human and physical processes interact to influence and change landscapes, environments and the climate; and how human activity relies on the effective functioning of natural systems

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

A model answer: how do ice cores show past climates?

Explain how scientists use an ice core to find out what the climate was like in the past.

Say how the ice forms. In places such as Antarctica it is so cold that snow does not melt. Each year’s snow is buried by the next and squashed into ice, so the ice builds up in layers.
Explain how the layers give dates. A core is a long cylinder of ice drilled out of the ice sheet. The deeper the ice, the older it is, so scientists can count annual layers near the top and use other methods deeper down.
Explain the air bubbles. As the snow turns to ice, it traps small bubbles of the atmosphere of that time. Scientists analyse the gas in them to measure how much carbon dioxide and methane the air held.
Explain how temperature is found. The ice itself contains slightly different forms of oxygen atoms depending on how warm it was when the snow fell. Measuring this gives an estimate of past temperatures.
Say what the evidence shows, and its limits. Cores from Antarctica reach back around 800,000 years and show that carbon dioxide and temperature rose and fell together through the glacial cycles. But they come from only a few places, so scientists compare them with other evidence such as tree rings and pollen.

Ice cores are drilled from ice sheets, where each year’s snow becomes a layer of ice. Trapped air bubbles show past levels of greenhouse gases, and the chemistry of the ice gives estimates of temperature. The deeper the ice, the older it is, with the longest cores reaching about 800,000 years back. Scientists check ice core results against other evidence.

Common mistakes and how to help

“The climate has always changed naturally, so people can’t be responsible now”

The first half is true, which makes the conclusion sound convincing.

What helps: Natural causes did drive past changes. But scientists can measure the extra carbon dioxide from burning fossil fuels, and it matches the recent warming. Ask which natural causes could explain the rapid recent rise, and what the evidence says.

Using a cold day or a snowy winter as proof that global warming is not happening

Weather is what people feel directly, so one cold week feels more convincing than a global average.

What helps: Climate is a long-term pattern. Compare one day with an average over decades, as a single day’s weather tells you little about the trend.

Thinking the greenhouse effect is itself harmful

News stories only discuss it as a problem.

What helps: Without a natural greenhouse effect Earth’s average surface temperature would be well below freezing. The concern is that human activity is strengthening it.

Mixing up climate change with ozone layer damage

Both involve the atmosphere and appear in news stories about the environment.

What helps: The ozone layer high in the atmosphere filters harmful ultraviolet light. Damage to it, mostly from chemicals that have since been largely banned, is a separate issue from the greenhouse effect.

How to help at home

Talk about the past in your own area. Ask older relatives or neighbours how weather and seasons have changed in their lifetimes, then ask what evidence would be needed to turn memories into reliable facts. This shows your child why scientists use measurements.
Count tree rings. If you see a sawn tree trunk or stump, count the rings with your child. Wide rings usually mean good growing years and narrow rings difficult ones, which is why rings are used as climate evidence. Looking is enough.
Draw a timeline. On a long strip of paper, place the last glacial maximum about 20,000 years ago, the end of the ice age about 11,700 years ago and the industrial period about 250 years ago. If 1 metre stands for 20,000 years, the whole industrial period is only about 1 centimetre long, which shows how recent and rapid the latest change is.
Look at your household energy. Walk round the home and list where energy comes from, such as heating, cooking, lights and travel. Discuss which uses involve burning fossil fuels, and which small changes the family could actually make.
Ask for evidence, not opinions. When a claim about climate comes up in the news, ask your child: what is the evidence, who measured it and could other evidence check it? These habits matter in geography lessons as much as the facts.

Builds on

Key Stage 2: Climate zones, biomes and vegetation belts
Key Stage 2: Rivers and the water cycle
Key Stage 2: Mountains
Key Stage 2: Volcanoes and earthquakes
Key Stage 2: Settlements and land use
Key Stage 2: Economic activity and trade
Key Stage 2: Natural resources