Anthropogenic climate change: the enhanced greenhouse effect and its causes, the evidence for human-driven warming, the environmental impacts, and the strategies of mitigation and adaptation.

What this dot point is asking

The SQA wants you to explain the enhanced greenhouse effect and its human causes, the evidence that warming is human-driven, the environmental impacts of climate change, and the strategies of mitigation (tackling the cause) and adaptation (coping with effects). This is the capstone sustainability topic, drawing the whole course together.

The enhanced greenhouse effect and its causes

The natural greenhouse effect keeps Earth warm. Human activity has enhanced it by adding more greenhouse gases.

More greenhouse gas means more outgoing infrared radiation is absorbed and re-radiated back to the surface, raising global temperatures, global warming, and changing climate patterns worldwide.

Evidence for human-driven warming

The evidence that the climate is warming and that humans are the cause includes:

• a clear rise in global average temperature over the industrial era;
• rising atmospheric carbon dioxide, measured directly (for example the Keeling Curve) and against the lower pre-industrial levels preserved in ice cores;
• melting glaciers and ice sheets and shrinking sea ice;
• rising sea levels from melting ice and thermal expansion;
• shifting seasons and the movement of species ranges.

The close match between rising carbon dioxide from fossil-fuel burning and rising temperature points to a human cause.

Environmental impacts

Climate change has wide-ranging impacts:

• Sea-level rise from melting ice and thermal expansion floods low-lying land and coasts;
• More frequent or severe extreme weather: droughts, heatwaves, storms and floods;
• Shifting habitats and species ranges, as organisms move towards poles or higher altitudes, threatening those that cannot move and disrupting ecosystems;
• Ocean acidification, as the sea absorbs carbon dioxide, harming shell-forming organisms and coral reefs.

These impacts connect back to biodiversity, water, food and the living environment across the course.

Mitigation and adaptation

• Mitigation examples: switching from fossil fuels to renewable (and nuclear) energy, energy efficiency, reforestation and carbon capture, reducing waste and methane, and changing diets and farming.
• Adaptation examples: building flood defences and sea walls, growing drought-resistant crops, improving water storage, and managing the retreat from vulnerable coasts.

A full response uses both: mitigation to limit how much the climate changes, and adaptation to cope with the change that is already locked in.

Examples in context

Example 1. The Keeling Curve and ice cores. Continuous measurements at Mauna Loa show atmospheric carbon dioxide rising year on year, and ice cores show today's levels are far above anything in the pre-industrial record. Together they provide direct evidence that human emissions are raising carbon dioxide and driving warming.

Example 2. The Netherlands' flood defences. With much of its land low-lying, the Netherlands invests heavily in dykes, barriers and managed water systems to cope with rising seas and storm surges. It is a clear example of adaptation, coping with climate impacts, which works alongside, not instead of, mitigation to cut emissions.

Try this

Q1. Name two greenhouse gases whose human emissions enhance the greenhouse effect. [2 marks]

• Cue. Carbon dioxide and methane (nitrous oxide is also acceptable).

Q2. State whether building a sea wall is mitigation or adaptation, and explain why. [2 marks]

• Cue. Adaptation, because it copes with an effect of climate change (rising sea level) rather than reducing emissions.