Global warming — AQA GCSE Combined Science
Test yourself on Global warming with AQA GCSE practice questions.
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Global warming explained
Global warming raises average temperatures and shifts weather patterns, so organisms face changed conditions.
Read the full explanation
Describe consequences by linking a physical change to an effect on organisms. For example, warmer seas can bleach coral reefs: corals lose their symbiotic algae, so the reef supports fewer fish. Rising temperatures can melt ice, reducing polar bear hunting habitat. Changed rainfall can make some habitats drier, so drought-tolerant plants spread while others decline. Warmer conditions can let some insect pests or disease-carrying mosquitoes extend their range, affecting crops or human health. Some species may migrate towards the poles or to higher land, while those that cannot move or adapt may become endangered or extinct. Describe means give clear points with a cause and effect, not just name a change. Use named examples where possible and explain the biological link.
Levels of carbon dioxide and methane in the atmosphere are increasing, and contribute to ‘global warming’.
Carbon dioxide and methane are greenhouse gases. Their atmospheric concentrations are rising because human activities add them faster than natural processes remove them. Carbon dioxide increases mainly from burning fossil fuels such as coal, oil and natural gas, and from deforestation, which reduces photosynthesis that removes carbon dioxide. Methane increases from agriculture, including livestock digestion and rice paddy fields, and from landfill sites and fossil fuel extraction. These gases absorb outgoing infrared radiation from the Earth's surface and re-emit it, so less heat escapes to space. This strengthens the greenhouse effect and contributes to global warming. The statement asks you to recognise the increase and the contribution, not to calculate exact temperature changes. Use the correct terms: greenhouse gas, infrared radiation, greenhouse effect.
Your focus
- State at least two biological consequences of global warming, each linked to a named organism or ecosystem.
- Describe how a physical change caused by global warming affects the survival or distribution of a species.
- Explain why some species may become endangered or extinct as a result of global warming.
Show all 6 objectives
- Identify carbon dioxide and methane as greenhouse gases whose atmospheric levels are increasing.
- Describe at least one human activity that increases carbon dioxide and one that increases methane.
- Explain how increasing greenhouse gas levels contribute to global warming by absorbing infrared radiation.
Global warming exam tips
Marking Points
- Rising sea temperatures can cause coral bleaching because corals lose their symbiotic algae, reducing the reef's biodiversity.
- Melting polar ice reduces the area of sea ice used by polar bears for hunting seals, so their food supply declines.
- Changes in rainfall patterns can cause some habitats to become drier, so drought-resistant plant species may replace those less able to survive.
- Warmer conditions can allow some insect pests or disease-carrying mosquitoes to spread into new areas, affecting crop yields or human health.
- Some species may shift their geographic range towards the poles or to higher altitudes, while species unable to move or adapt may become endangered or extinct.
- Changing temperatures can alter the timing of life-cycle events such as breeding, flowering or migration, which can disrupt food chains and ecological interactions.
- Carbon dioxide is a greenhouse gas and its atmospheric concentration is increasing.
- Methane is a greenhouse gas and its atmospheric concentration is increasing.
- Burning fossil fuels such as coal, oil and natural gas releases carbon dioxide.
- Deforestation reduces the removal of carbon dioxide by photosynthesis, contributing to its increase.
- Agriculture, including livestock and rice paddy fields, and landfill sites release methane.
- Greenhouse gases absorb outgoing infrared radiation and re-emit it, so less heat escapes to space, contributing to global warming.
Examiner Tips
- 💡Use command word 'describe' to give a sequence of clear points: state the environmental change, then the biological effect on a named organism.
- 💡Include at least one named example, such as coral bleaching or polar bear habitat loss, to make your answer specific.
- 💡Link each consequence back to global warming rather than writing generally about pollution or habitat loss.
- 💡Name the human activities that increase each gas: fossil fuel combustion and deforestation for carbon dioxide; livestock, rice paddies and landfill for methane.
- 💡Use the phrase 'absorb infrared radiation' rather than 'absorb heat' to show precise scientific understanding.
- 💡Link the increase in greenhouse gases to the enhanced greenhouse effect and global warming in one clear chain of reasoning.
Common Mistakes
- Confusing global warming with ozone depletion: students may say the ozone hole causes warming. Correction: global warming is mainly driven by greenhouse gases trapping heat, while ozone depletion is a separate issue caused by CFCs.
- Giving only physical effects such as 'ice melts' without a biological consequence. Correction: always link the physical change to an effect on a named organism or ecosystem, for example melting sea ice reduces polar bear hunting habitat.
- Assuming all species will simply move or adapt successfully. Correction: some species cannot move fast enough or have no suitable habitat, so they may become endangered or extinct.
- Saying carbon dioxide or methane 'destroys' the ozone layer. Correction: these gases contribute to global warming by absorbing infrared radiation; ozone depletion is caused mainly by CFCs.
- Confusing the greenhouse effect with global warming. Correction: the greenhouse effect is a natural process that keeps Earth warm; global warming is the recent increase in average temperature due to extra greenhouse gases.
- Thinking methane is unimportant because it is present in smaller amounts than carbon dioxide. Correction: methane is a more potent greenhouse gas per molecule, so even smaller increases contribute to warming.