What Is Climate Change? A KS3 Geography Guide

Climate change refers to long-term shifts in global temperatures and weather patterns. Since the mid-twentieth century, human activities — particularly the burning of fossil fuels — have been the main driver of these changes, releasing greenhouse gases that trap heat in the atmosphere and cause the Earth to warm beyond its natural range.

What is the difference between weather and climate?

Before exploring climate change, it helps to be clear on the distinction between weather and climate:

Weather is what conditions are like outside today — temperature, cloud cover, rainfall, wind. It changes from day to day.

Climate is the average pattern of weather in a region over a long period, typically at least 30 years.

Climate change is not about one unusually hot summer. It is about measurable, sustained shifts in those 30-year averages — and the accelerating pace of those shifts in the current era.

What causes climate change?

The natural greenhouse effect

The Earth's atmosphere contains gases — including water vapour, carbon dioxide (CO₂) and methane (CH₄) — that act like a blanket around the planet. Incoming solar radiation warms the Earth's surface; outgoing heat radiation is partly trapped by these gases and re-radiated back downward. Without this natural greenhouse effect, the Earth's average surface temperature would be approximately -18°C rather than the current +15°C. The greenhouse effect is essential to life.

The enhanced greenhouse effect

The problem is that human activities are adding extra greenhouse gases to the atmosphere faster than natural processes can absorb them. The primary sources are:

Source | Key greenhouse gas emitted
Burning fossil fuels (coal, oil, gas) | CO₂
Deforestation (removing carbon sinks) | CO₂
Livestock farming | CH₄ (methane)
Paddy field agriculture | CH₄ (methane)
Industrial processes and cement | CO₂, N₂O

Since the Industrial Revolution (broadly from the 1750s), atmospheric CO₂ concentrations have risen from approximately 280 parts per million (ppm) to over 420 ppm in 2023 — the highest level in at least 800,000 years of ice-core data, according to the Met Office.

What is the evidence for climate change?

The evidence for human-caused climate change is extensive and comes from multiple independent sources:

Temperature records: The Met Office's global temperature series shows that nineteen of the twenty warmest years on record have occurred since 2000. The year 2023 was confirmed as the warmest on record globally.

Ice sheets and glaciers: The Arctic sea ice extent has shrunk by around 13% per decade since satellite observations began in 1979 (NASA data). Mountain glaciers on every continent are retreating.

Sea level rise: Global mean sea level has risen approximately 20 cm since 1900, with the rate accelerating. IPCC projections suggest a further 0.3–1 m rise by 2100 under different emissions scenarios.

Ocean warming and acidification: The oceans absorb roughly 90% of the excess heat and about 30% of the CO₂ added to the atmosphere, making them warmer and more acidic — a serious threat to coral reef ecosystems.

Extreme weather frequency: Heatwaves, heavy rainfall events and some types of tropical cyclone are becoming more frequent and more intense, consistent with climate model predictions.

What are the impacts of climate change?

Climate change affects physical and human systems across the globe, but the impacts are uneven — countries least responsible for historical emissions often face the greatest risks.

Physical impacts

More frequent and intense heatwaves

Changes to precipitation patterns: some regions get wetter, others drier

Melting ice sheets contributing to sea level rise

Ocean warming bleaching coral reefs (e.g. Great Barrier Reef, where 50% of corals have died since 2016)

Permafrost thaw releasing methane (a feedback loop)

Human and economic impacts

Threats to food security as growing conditions shift

Displacement of coastal and low-lying communities (e.g. Bangladesh, Pacific Island nations)

Increased risk of drought in sub-Saharan Africa

Rising costs of flood damage in the UK — the Environment Agency has estimated flood risk could cost the UK up to £1 billion per year more by 2050 without adaptation investment

How do countries respond to climate change?

Responses fall into two categories:

Mitigation — reducing the causes of climate change by cutting greenhouse gas emissions. Examples: switching from fossil fuels to renewable energy (wind, solar), improving energy efficiency, protecting and restoring forests, and electrifying transport.

Adaptation — adjusting to the impacts that are already happening or unavoidable. Examples: building sea walls, developing drought-resistant crops, redesigning urban areas to manage heat and flooding.

The UK government's Climate Change Act 2008 committed the UK to legally binding emissions reduction targets. The UK reached "net zero" electricity generation from coal for the first time in April 2024. However, global emissions continue to rise overall, meaning mitigation efforts need to accelerate significantly.

A worked example: the SEEP framework applied to climate change

Geographers often use the SEEP framework (Social, Economic, Environmental, Political) to organise the impacts of an issue:

SEEP dimension | Climate change impact example
Social | Displacement of communities in low-lying areas; heat-related illness particularly affecting elderly populations
Economic | Increased cost of flood insurance; reduced agricultural yields in drought-affected regions
Environmental | Species extinction as habitats shift; bleaching of coral reefs; loss of Arctic sea ice
Political | International negotiations (COP climate summits); tensions over climate finance for developing nations

Using SEEP ensures your geography answers cover the full range of impacts rather than focusing only on environmental effects.

Frequently asked questions

What is the greenhouse effect in simple terms for KS3?

The greenhouse effect is a natural process where certain gases in the Earth's atmosphere — including carbon dioxide and methane — trap heat from the sun and warm the planet's surface. Without it, the Earth would be too cold for life. The problem is that human activities are adding extra greenhouse gases, trapping more heat than normal and causing temperatures to rise.

How much has the Earth warmed?

According to the Met Office, the Earth has warmed by approximately 1.2°C above pre-industrial levels (the average from 1850 to 1900) as of 2023. The Paris Agreement of 2015 set a target of limiting warming to 1.5°C to avoid the most severe impacts — a threshold that scientists now warn could be reached within the next decade without significant emissions cuts.

What is the difference between climate change and global warming?

Global warming refers specifically to the rise in average global temperatures caused by increased greenhouse gases. Climate change is a broader term covering all the changes in climate patterns that result from this warming — including changes to precipitation, wind patterns, sea levels and the frequency of extreme weather events. Global warming is the cause; climate change describes the range of effects.

What can KS3 students do about climate change?

Individual actions matter in aggregate but are insufficient without systemic change. At a personal level, reducing meat consumption, flying less, and avoiding single-use plastics each have a measurable impact. More powerfully, becoming an informed citizen — understanding the science, the politics and the economics of climate responses — enables effective engagement with the decisions that shape collective outcomes at local, national and international level.

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