Climate change in the Quaternary

The Quaternary period covers roughly the last 2.6 million years. During this time the Earth's climate has swung repeatedly between:

• Glacial periods — long, cold spells (ice ages) when ice sheets advanced.
• Interglacial periods — warmer gaps between them; we live in one now (the Holocene).

Since the Industrial Revolution, and especially since about 1900, global average temperature has risen unusually fast — a change that natural cycles alone struggle to explain.

Key idea: climate has always changed naturally; what is unusual now is the rate of warming, which matches the rise in human greenhouse-gas emissions.

Evidence for climate change

Geographers use a range of evidence — each with different reliability:

• Ice cores — layers of ancient ice trap air bubbles, giving temperature and CO₂ going back ~800,000 years. Very reliable, but only from polar regions.
• Sea-ice / glacier positions — retreating ice and satellite records show recent warming.
• Global temperature data — direct instrument records since ~1850; reliable but short.
• Paintings and diaries — historical sources (e.g. Thames "Frost Fairs") suggest past cold spells, but are subjective and local.

Reliability: scientific data (ice cores, instruments) is more reliable than art or diaries, which can be biased, incomplete or hard to date.

Which evidence is most reliable?

Natural causes of climate change

Before humans, three natural mechanisms drove climate change:

• Sunspots — dark patches on the Sun linked to changes in solar output; more sunspots means slightly more energy reaching Earth.
• Volcanic eruptions — large eruptions eject ash and sulphur dioxide that reflect sunlight, causing short-term cooling.
• Milankovitch cycles — long-term changes in the Earth's orbit (eccentricity), tilt (obliquity) and wobble (precession) that alter how much solar energy reaches different latitudes, driving glacial–interglacial cycles.

The enhanced greenhouse effect

Greenhouse gases (CO₂, methane, water vapour) trap outgoing heat — the natural greenhouse effect keeps Earth warm enough for life. But human activities add extra greenhouse gases, strengthening this into the enhanced greenhouse effect:

• Burning fossil fuels (power, transport, industry) releases CO₂.
• Deforestation removes trees that absorb CO₂.
• Agriculture (livestock, rice) and landfill release methane.

Match the cause to its description

Tap a cause on the left, then tap its correct description on the right.

Natural or enhanced?

Consequences of climate change

OCR wants 21st-century social, economic and environmental impacts, worldwide and in the UK:

• Environmental — melting ice sheets and glaciers; sea-level rise (~3.3 mm/yr today); more extreme weather; coral bleaching.
• Social — low-lying areas and islands (e.g. the Maldives, Bangladesh) at risk of flooding; "climate refugees"; health impacts of heat.
• Economic — damage from floods and storms; changing farming (some crops fail, others become possible); cost of new defences.

Climate change in the UK

The UK is already seeing 21st-century effects:

• Warmer, wetter winters and hotter summers; more frequent heatwaves (e.g. July 2022 exceeded 40 °C for the first time on record).
• More flooding from intense rainfall; coastal areas at greater risk from sea-level rise.
• Shifts in industry — changing farming (new crops such as vineyards spreading north) and pressure on tourism and water supply.

Your turn — sea-level rise

Projecting sea-level rise

Natural or human cause?

Tap a cause, then tap the box it belongs in.

Type of impact?

Classify each consequence of climate change.

Reading the Quaternary

A natural cooler

The key ideas to know

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