Recent and predicted climatic change and potential impact on coasts.

The idea

Recent climatic change has driven a global eustatic sea-level rise of approximately 3.4 mm per year, primarily through thermal expansion of oceans and the melting of terrestrial ice sheets. Predicted climatic changes suggest an acceleration of this trend, with sea levels potentially rising by 0.3 m to over 1.0 m by 2100 depending on emission pathways. The potential impacts on coasts are severe, including increased frequency and magnitude of coastal flooding, accelerated rates of coastal erosion, and the permanent inundation of low-lying areas like the Maldives. Furthermore, warmer sea surface temperatures may increase the intensity of tropical cyclones, exacerbating storm surges and threatening coastal infrastructure and ecosystems such as salt marshes.

What earns the marks

• Identify thermal expansion and the melting of land-based ice (glaciers and ice sheets) as the primary drivers of recent eustatic sea-level rise.
• Use quantitative data to describe recent and predicted sea-level changes, such as the current rise of approximately 3.4 mm per year.
• Explain how climate change increases the risk of coastal flooding and accelerates coastal erosion through higher baseline sea levels and more intense storm surges.
• Discuss the socio-economic and environmental impacts on coastal communities, such as the loss of coastal habitats through coastal squeeze and damage to infrastructure.

Common mistakes and how to put them right

• Claiming that melting sea ice causes sea-level rise.

  Put it right: Only the melting of land-based ice and thermal expansion contribute to eustatic rise.

• Confusing weather events with climate change.

  Put it right: Climate change refers to long-term trends rather than individual, isolated storms.

• Assuming all coasts will be impacted equally.

  Put it right: Local factors such as isostatic rebound, coastal topography, and existing defences mean impacts vary spatially.

Exam tips

• Quote specific figures from the IPCC regarding recent sea-level rise and future projections to support your arguments.
• Discuss the concept of coastal squeeze where rising sea levels push coastal habitats against fixed artificial defences, leading to habitat loss.
• Evaluate the varying vulnerability of different coastlines, contrasting low-lying islands with steep, rocky coastlines.