Explain the enhanced greenhouse effect and evaluate responses to anthropogenic climate change

What this dot point is asking

SCSA wants you to distinguish the natural greenhouse effect from the human-enhanced one, present the evidence, and evaluate responses. A strong answer connects emissions to a mechanism, to observed change, and to a management strategy.

The greenhouse effect

The Sun warms Earth's surface, which radiates heat back as infrared. Greenhouse gases such as carbon dioxide, methane and water vapour absorb some of this outgoing infrared and re-emit it, including back toward the surface, keeping the lower atmosphere warmer than it would otherwise be. Without this natural effect, Earth would be far too cold for life. The problem is not the effect itself but its enhancement.

Human activities that enhance it

• Burning fossil fuels for electricity, transport and industry releases carbon dioxide that was locked in the geosphere for millions of years.
• Land clearing and deforestation remove carbon-absorbing vegetation and release stored carbon.
• Agriculture releases methane from livestock and rice, and nitrous oxide from fertilisers.
• Industrial processes release further greenhouse gases.

These shift the carbon cycle, adding carbon to the atmosphere faster than natural sinks such as oceans and forests can remove it.

The evidence

Multiple independent lines of evidence point to human-caused warming.

• Rising atmospheric carbon dioxide measured directly since the late 1950s, now far above the range seen in ice-core records.
• Rising global average temperatures over the past century.
• Shrinking glaciers and polar ice, and rising sea levels.
• The chemical signature of the added carbon matches fossil fuel sources.

The correlation between emissions and warming, combined with the known physics of greenhouse gases, links the two.

Impacts on Earth systems

Warming affects all four spheres.

• Hydrosphere: sea-level rise from melting ice and thermal expansion threatens low-lying coasts; ocean acidification harms shell-forming organisms and coral.
• Biosphere: shifting climate zones force species to move or adapt; coral bleaching has repeatedly affected the Great Barrier Reef during marine heatwaves.
• Atmosphere: more frequent and intense heatwaves, and changed rainfall patterns, including the long-term drying trend in south-west Western Australia.
• Geosphere: thawing permafrost and changing erosion patterns.

Responses: mitigation and adaptation

Mitigation reduces the cause:

• Shifting to renewable energy such as solar and wind, both abundant in Australia.
• Improving energy efficiency.
• Protecting and restoring forests as carbon sinks.
• Carbon pricing and international agreements such as the Paris Agreement.

Adaptation manages unavoidable impacts:

• Coastal defences and managed retreat from rising seas.
• Drought-tolerant crops and improved water management.
• Heatwave planning for cities.

Evaluating these, mitigation tackles the root cause but needs global cooperation and time to take effect, while adaptation protects communities now but does not stop warming. Most experts argue both are needed together.