Global Climate Change

Higher sea levels increase the risk of flooding in low-lying coastal areas. Coastal erosion and flooding can destroy habitats, damage buildings and reduce the amount of usable land. Salt water entering soils can also make land less suitable for growing crops.

These changes affect both wildlife and people. Coastal communities may need expensive flood defences, and some people may have to leave their homes. The change is already measurable: global average sea level rose by around 20 centimetres between 1901 and 2018.

Effect 2: changing rainfall and water supplies

Warming changes rainfall patterns, but not in the same way everywhere. Warmer conditions increase evaporation, and warmer air can hold more water vapour. Changes in wind patterns also affect where rain falls. Some regions therefore receive heavier rainfall, while others receive less rain.

Reduced rainfall can lead to drought, freshwater shortages and crop failure. This threatens food supplies and people's livelihoods. Where water is already scarce, further shortages can increase competition for supplies.

Heavier rainfall creates a different problem. Rivers may overflow or drainage systems may be overwhelmed, flooding homes, farmland and transport routes. Urban areas can be particularly vulnerable because water cannot readily soak through concrete surfaces.

Effect 3: more damaging extreme weather

Climate change can increase the likelihood or severity of extreme weather. Heatwaves become more likely as average temperatures rise. Extreme heat can harm human health, damage crops and increase the risk of fires that destroy habitats.

Warmer oceans can also contribute to more intense tropical storms and heavier associated rainfall. Strong winds and flooding can damage buildings, disrupt transport and put lives at risk.

Different types of extreme weather do not all change in the same way. For example, tropical storms could become more intense without becoming more frequent. A long-term change in risk does not mean that every individual weather event has the same cause.

Effect 4: habitat change and loss of biodiversity

Organisms depend on suitable environmental conditions. Changes in temperature, rainfall and water availability can make existing habitats less suitable. Coastal flooding and extreme weather can also damage or destroy habitats directly.

Some species may survive in different areas, but others cannot move or adapt quickly enough. Their populations may decline, increasing the risk of extinction. Losing species reduces biodiversity and can affect other organisms connected to them through food chains. Damage to marine ecosystems can also threaten fisheries on which people depend.

Judging the scale and risks

Climate change is a global, long-term problem, but its impacts are uneven. Low-lying coasts face particular flood risks, while regions that are already hot or dry may face serious heat and water shortages. Changes can continue for decades: sea levels will keep rising even if greenhouse gas emissions are reduced.

Risk depends on both the hazard and how vulnerable people or ecosystems are. A community with strong flood defences and reliable emergency services may suffer less damage than one with fewer resources. Poorer communities often have less capacity to adapt or recover.

Effects also interact. Drought can reduce harvests, while flooding can disrupt food transport, together making food insecurity worse. Habitat damage can reduce biodiversity at the same time as it damages livelihoods.

Not every local effect is harmful: some colder regions may initially gain longer growing seasons or opportunities to grow new crops. However, these benefits may not last as warming continues. A balanced judgement weighs such possible benefits against widespread risks to health, homes, water supplies, food production and ecosystems.

• Sea-level rise: melting land ice and thermal expansion of seawater → coastal flooding, habitat loss and displacement.
• Changing rainfall: drought and water shortages in some regions; heavier rainfall and flooding in others → threats to crops, water supplies and infrastructure.
• Extreme weather: more likely heatwaves and potentially more intense tropical storms → health risks, fires and damage.
• Habitat and biodiversity loss: unsuitable or damaged habitats → declining populations and greater extinction risk.

Discuss scale, risk and implications

• Global effects can continue over decades, but impacts are uneven.
• Low-lying coasts and already hot or dry regions are particularly vulnerable.
• Fewer resources for adaptation can mean greater harm.
• Linked effects can worsen food insecurity and damage ecosystems.
• Some colder regions may initially benefit agriculturally, but benefits may not persist.
• Greater storm intensity does not necessarily mean greater storm frequency.