Describe the physical impacts of climate change on the environment

What this dot point is asking

SEAB wants you to describe the physical impacts of climate change, the ways a warming climate alters the natural environment. The central insight is that warming does not act alone: it raises sea levels, melts ice, intensifies extreme weather, warms and acidifies the oceans, and shifts ecosystems, and these physical changes are the foundation for the human impacts that follow.

The answer

Rising sea levels

A warming world raises global sea levels through two mechanisms:

• Melting land ice: glaciers and the great ice sheets of Greenland and Antarctica lose mass, adding water to the oceans.
• Thermal expansion: as ocean water warms, it expands and takes up more space, lifting the level even without extra water.

Rising seas threaten low-lying coasts and islands with flooding and erosion.

Melting ice and thawing permafrost

Warming shrinks the world's ice:

• Mountain glaciers retreat, reducing the meltwater that feeds rivers.
• Arctic sea ice shrinks in extent and thickness.
• Permafrost (permanently frozen ground) thaws, which can release stored greenhouse gases and damage the land.

More frequent and intense extreme weather

A warmer atmosphere holds more energy and moisture, making extreme weather more common and severe:

• Heatwaves become hotter and longer.
• Heavy downpours and floods increase, as warmer air carries more water vapour.
• Droughts worsen in some regions as evaporation rises.
• Tropical storms can become more intense.

Ocean warming and acidification

The oceans absorb most of the extra heat and much of the extra carbon dioxide:

• Ocean warming causes coral bleaching, where heat-stressed corals expel the algae that feed them, turning white and often dying.
• Ocean acidification occurs as seawater absorbs carbon dioxide, making it harder for corals and shellfish to build their skeletons and shells.

Shifting ecosystems

As climates shift, the ranges of plants and animals move, often toward the poles or higher altitudes, and the timing of natural events changes, disrupting ecosystems.

Examples in context

Example 1. Coral bleaching on the Great Barrier Reef. Repeated marine heatwaves have caused mass coral bleaching events on Australia's Great Barrier Reef, with large stretches of coral whitening and parts dying. It is a vivid physical impact of ocean warming, and because reefs support fisheries, tourism and coastal protection, the damage shows how a physical change ripples outward. Reefs across Southeast Asia face the same threat.

Example 2. Sea-level rise threatening low-lying Pacific islands. Nations such as Tuvalu and Kiribati, only a few metres above sea level, face rising seas that flood land, erode coasts and contaminate freshwater with salt. These islands are among the first places where sea-level rise is a present physical reality, illustrating the impact that most concerns low-lying states, including coastal cities like Singapore.

Try this

Q1. State the two main reasons global sea levels are rising. [2 marks]

• Cue. The melting of land ice such as glaciers and the Greenland and Antarctic ice sheets, which adds water to the oceans, and the thermal expansion of seawater as it warms and takes up more space.

Q2. Explain why heavy rainfall events may become more common as the climate warms. [2 marks]

• Cue. A warmer atmosphere can hold more water vapour, so when conditions cause that moisture to condense, more rain can fall at once, making intense downpours and flooding more likely.

Q3. Describe what happens during coral bleaching. [2 marks]

• Cue. When the sea becomes too warm, corals expel the algae that live in them and give them food and colour, so the coral turns white; if the warm conditions persist the weakened coral can die.