Climate change: evidence, causes and responses

Separate weather from climate, examine evidence and judge mitigation and adaptation at different scales.

Read a climate signal

Weather describes conditions over a short period; climate describes their longer-term distribution. Compare temperature using a stated period, area and baseline.

Instrumental records and proxy evidence such as ice cores answer different questions and have different uncertainties. One cold day cannot establish a global trend.

Worked example

Fictional mean temperatures of 11.2°C and 12.0°C differ by 0.8°C. This is an absolute change; an anomaly also requires a named baseline.

Common mistake: A station maximum and a global annual mean are not interchangeable.

Source evaluation · Mean, median and range

Connect causes to the energy balance

Greenhouse gases absorb and emit infrared radiation. Increasing their concentration changes Earth’s energy balance. Fossil fuel combustion transfers carbon from long-term geological stores into the atmosphere.

Natural drivers include orbital changes, solar variability and volcanic aerosols. Their roles depend on timescale; a list of causes does not show which explains a particular trend.

Worked example

A fictional emissions index rises from 100 to 135 while population rises from 100 to 120. The per-person index is 135 ÷ 120 × 100 = 112.5. Total emissions and emissions per person both increased.

Common mistake: A slower increase still adds emissions; it is not an absolute reduction.

Index numbers · Percentage change

Evaluate a response

Mitigation reduces emissions or increases net removal. Adaptation changes exposure or vulnerability to impacts. A measure may contribute to both, but each claim needs evidence.

Compare lifetime costs, distribution of benefits, maintenance and unintended consequences. Tree planting needs suitable land, survival and time; flood protection needs capacity and upkeep.

Worked example

A fictional project cuts annual emissions from 50 to 35 units: a 30% reduction. This is an annual flow change, not proof that atmospheric carbon has fallen by 30%.

Common mistake: Project completion does not demonstrate all expected outcomes.

Percentage change · Source evaluation

Try a different resource

Time series and missing observations

The same river level threshold is used throughout. One annual record is missing. Line segments only connect consecutive observed years; no zero or interpolated observation has been inserted.

Scroll the diagram sideways to see the full resource.

Year	Days above the fixed level
2018	29
2019	36
2020	25
2021	38
2022	Missing
2023	33
2024	26
2025	31

Fictional annual river record. Original fictional resource; not an official map or real dataset.

Resource description

Exact observations: 2018: 29 days; 2019: 36 days; 2020: 25 days; 2021: 38 days; 2022: missing days; 2023: 33 days; 2024: 26 days; 2025: 31 days. The line is deliberately broken at the missing year.

Write an explanation

Evaluate the view that adaptation is enough to manage climate change.

Check your answer

Distinguish adaptation from mitigation.
Explain an impact pathway and the limits of adapting to it.
Compare scales and time horizons.
Reach a judgement supported by evidence.

Practise and review a written answer

Case studies

Permafrost thaw and Denali’s park road · Solar home systems in Bangladesh · Concentrated solar power at Noor Ouarzazate

These pages provide selected evidence. Check the whole case requirement with your teacher.

Read further

Adaptation to changing conditions · Matching evidence to a claim · Power, energy and reliable supply

Course links

AQA GCSE Geography · Pearson Edexcel GCSE Geography B · National 5 Geography · Higher Geography · Pearson Edexcel GCSE Geography A · OCR GCSE Geography A · OCR GCSE Geography B · Eduqas GCSE Geography A · Eduqas GCSE Geography B · OCR A-level Geography · Eduqas A-level Geography

Next topics

Carbon cycles: stocks, fluxes and changing feedbacks · Water resources: reliable supply and competing uses

Selected teaching sequence with fictional worked data. The linked case records supply bounded evidence; they do not satisfy every course case requirement.

Scottish links identify reusable parts of the topic. Scottish landforms, soil, weather and disease requirements need additional course-specific teaching.

Worked numerical examples are fictional unless explicitly attributed. These lessons cover selected parts of the topic; check your course requirements for the rest.