Physical geography · GCSE Geography
Climate change
The evidence that climate is changing, natural and human causes, and the difference between mitigation and adaptation.
The greenhouse effect is not new. The enhanced one is.
The important bits
What you need to know
- 1
Climate is the long-term average of weather. A cold week does not disprove global warming; trends in global mean temperature, ice and sea level do the arguing.
- 2
Evidence is multi-proxy: thermometer records since the nineteenth century, ice cores trapping ancient air, tree rings, glacial retreat, shrinking Arctic sea ice, earlier springs, and rising sea level from thermal expansion plus meltwater.
- 3
Natural causes include Milankovitch orbital cycles (shape, tilt, wobble) over tens of thousands of years, solar output variation, and volcanic aerosols that cool briefly (Pinatubo 1991). These explain ice ages; they do not explain the late-twentieth-century spike.
- 4
The natural greenhouse effect keeps Earth habitable: water vapour, carbon dioxide and methane trap outgoing long-wave radiation. Without it, the planet would be a frozen ball.
- 5
The enhanced greenhouse effect is extra trapping from fossil fuels, deforestation (less carbon absorbed, burning releases CO2), and agriculture (methane from cattle and rice; fertiliser nitrous oxide). That is the human cause the exam wants named.
- 6
Impacts are uneven: low-lying coasts and small islands (Maldives, Tuvalu) face inundation; Sahel rainfall reliability shifts; UK winters may be wetter and extremes sharper; Arctic communities and ecosystems lose ice. Feedbacks (albedo loss, permafrost methane) can accelerate change.
- 7
Mitigation cuts the cause: renewable energy, energy efficiency, afforestation, international agreements (Kyoto, Paris 2015). Adaptation lives with the effects: sea walls, drought-resistant crops, managed retreat, changing insurance. Places need both.
- 8
Climate justice is geography: HICs caused most historic emissions; many LICs face the sharpest impacts with the smallest budgets. That tension sits inside every COP headline.
Go deeper
Why “it’s been warmer before” is not an exam answer
Earth’s climate has swung between glacials and interglacials. Ice cores from Antarctica show CO2 and temperature dancing together over 800,000 years. The dangerous claim is that today’s warming is therefore natural. Orbital cycles operate on millennial scales; the post-1850 rise, especially since 1970, is too fast and matches the rise in anthropogenic greenhouse gases, while solar output has not tracked the warming. Volcanoes cause a year or two of cooling, not a sustained climb. In six-mark “discuss natural and human causes” answers, give the natural mechanisms credit for the deep past, then show why they fail as the main driver now. That is evaluation, not activism.
Go deeper
Mitigation is not adaptation with a longer word
Students mix these up constantly. Mitigation: reduce emissions or enhance sinks — wind farms, nuclear, insulating homes, restoring peat, carbon pricing, the Paris pledge to keep warming well below 2°C. Adaptation: flood barriers on the Thames, raising houses in Bangladesh, switching crops, early-warning systems, moving a capital (Indonesia’s planned shift from Jakarta). A coastal LIC may adapt because it cannot wait for global mitigation; an HIC can afford both. Exam questions often ask which is more sustainable. Mitigation treats the disease; adaptation treats the symptoms. Geography’s honest answer is that both are required, and that adaptation without mitigation becomes an endless, unequal arms race against the sea.
See the idea in action
Question: explain how human activity has caused climate change. Point: burning fossil fuels. Develop: coal, oil and gas release stored carbon as CO2, thickening the greenhouse blanket, raising global temperatures. Second human cause: deforestation in Amazonia reduces photosynthesis uptake and can add CO2 through burning. Third: methane from cattle and paddy fields, a more powerful greenhouse gas per molecule. Finish with a place impact (Arctic ice, Maldives) so the process does not float.
Exam technique
Turn knowledge into marks
If a question says “evidence of climate change”, do not explain the greenhouse effect. Give ice, temperature, sea level, glaciers — the symptoms — unless it also asks for causes.
Common mistakes
Do not give these marks away
- 01
Confusing the greenhouse effect (necessary) with the enhanced greenhouse effect (the problem).
- 02
Using weather anecdotes (“it snowed in April”) as climate evidence.
- 03
Writing mitigation examples under an adaptation heading, or the reverse.
What is the difference between the greenhouse effect and the enhanced greenhouse effect?
AThere is no difference; both are caused only by volcanoes
BThe greenhouse effect is a natural warming process; the enhanced effect is extra warming from human greenhouse-gas emissions
CThe greenhouse effect only happens at night
DThe enhanced greenhouse effect cools the Earth by reflecting sunlight
Show the answer
The greenhouse effect is a natural warming process; the enhanced effect is extra warming from human greenhouse-gas emissions. Greenhouse gases keep Earth warm enough for life. Extra CO2, methane and related gases from fossil fuels, deforestation and farming trap more heat than the natural baseline.
Quick questions
If this is the bit you searched
Does the hole in the ozone layer cause global warming?
They are different problems. Ozone depletion (CFCs) is about UV at the poles; climate change is about greenhouse trapping of heat. CFCs are greenhouse gases too, but “the ozone hole” is not the mechanism of global warming.
What did the Paris Agreement 2015 actually do?
It committed countries to nationally determined contributions aiming to keep warming well below 2°C, pursuing 1.5°C. It is a political framework, not a physical switch: implementation and gaps still decide the temperature outcome.