Global climate change — AQA GCSE Chemistry
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Global climate change explained
Global climate change covers 3 specification points, including An increase in average global temperature is a… and There are several potential effects of global….
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Open a point below for its explanation and revision guidance.
An increase in average global temperature is a major cause of climate change.
Average global temperature is calculated from many land and sea measurements over a long period. When this average rises, the climate system changes: warmer air holds more water vapour, ice melts, and ocean water expands. These changes alter weather patterns, sea level and habitats, so the temperature rise is a major cause of climate change. It is not the only factor, because volcanic eruptions and changes in solar output also affect climate, but the recent rise is linked to increased greenhouse gases from human activity. A useful method is to distinguish weather, which is short term and local, from climate, which is long term and average. A single hot day is weather; a rising multi-decade average is climate change.
There are several potential effects of global climate change.
Global climate change can affect the environment and people in several ways. Melting ice sheets and glaciers, plus thermal expansion of seawater, raise sea level and increase flooding of low-lying land. Warmer oceans and air can make some storms and rainfall events more intense, while other regions become drier and face drought. Habitats such as coral reefs and polar ecosystems may be damaged, so species may migrate, decline or become extinct. Agriculture may suffer where rainfall changes or pests spread, affecting food supply. Human health may be affected by heatwaves and changing disease patterns. These effects are potential because their size and location depend on how much warming occurs and how societies respond. A useful method is to group effects into environmental, economic and social categories.
Students should be able to: describe briefly four potential effects of global climate change discuss the scale, risk and environmental implications of global climate change. AQA GCSE Chemistry 8462. GCSE exams Jun
Global climate change arises because greenhouse gases such as carbon dioxide and methane absorb infrared radiation re-emitted by Earth, warming the atmosphere and oceans. Four potential effects to describe briefly are: rising sea levels as ice sheets and glaciers melt and warm water expands; more frequent and severe extreme weather such as heatwaves, droughts and heavy rainfall; changes to ecosystems and habitats, so some species shift range or decline; and impacts on agriculture and water supply, affecting food security and human health. Scale means the effects are global and long-lasting, spanning decades and continents. Risk means the likelihood and seriousness of harm, which is greater where populations are exposed and less able to adapt. Environmental implications include biodiversity loss, ocean acidification and altered nutrient cycles.
Your focus
- Define average global temperature and distinguish it from local weather.
- Explain how a rise in average global temperature causes climate change.
- Describe at least two effects of the temperature rise on the climate system.
Show all 9 objectives
- Describe several potential environmental effects of global climate change.
- Describe several potential effects on human societies and economies.
- Explain why the effects are potential and vary between regions.
- State four potential effects of global climate change.
- Explain the scale and timescale over which climate change acts.
- Discuss risk and environmental implications for people and ecosystems.
Global climate change exam tips
Marking Points
- Define average global temperature as a long-term average from many measurements around the world.
- Explain that a rise in this average drives climate change by altering the climate system.
- Link the temperature rise to effects such as melting ice, thermal expansion of oceans and changed weather patterns.
- Distinguish climate, a long-term average, from weather, which is short term and local.
- Recognise that other factors such as volcanic activity and solar variation also affect climate, but the recent rise is linked to greenhouse gases.
- Describe sea-level rise from melting ice and thermal expansion, and its effect on coastal flooding.
- Describe changed weather patterns, including more intense rainfall or storms in some regions and drought in others.
- Describe effects on ecosystems, such as coral bleaching, habitat loss and species migration or extinction.
- Describe effects on people, including impacts on agriculture, food supply, water availability and health.
- Explain that effects are potential and depend on the amount of warming and on human responses such as adaptation.
- Names carbon dioxide and methane as greenhouse gases that absorb infrared radiation and warm the atmosphere.
- Describes at least four distinct effects, for example sea-level rise, extreme weather, ecosystem change and effects on agriculture or water supply.
- Explains scale as global and long-term, affecting many countries over decades rather than one local area.
- Explains risk as the combination of how likely an effect is and how serious its consequences would be.
- Links environmental implications to biodiversity, habitats, oceans or nutrient cycles.
- Uses the idea that some regions and communities are more vulnerable because they cannot adapt easily.
Examiner Tips
- 💡Define average global temperature before explaining its effect, so your answer has a clear starting point.
- 💡Use the weather-versus-climate distinction when a question gives a short-term event.
- 💡Link the temperature rise to at least two consequences to show the causal chain.
- 💡Group your points into categories such as environmental, economic and social to cover the range of effects.
- 💡Use specific named examples, such as low-lying islands or coral reefs, to make each effect concrete.
- 💡Add a sentence explaining that the effects are potential and depend on future warming and adaptation.
- 💡Use command words carefully: describe means give the effect, discuss means develop scale, risk and implications.
- 💡Keep each effect to one clear sentence so four effects fit comfortably in the time available.
- 💡Where asked to discuss, add a sentence on why an effect is serious or who is most at risk rather than listing more effects.
Common Mistakes
- Using one cold day to argue against global warming; correct by explaining that climate is a long-term average, so single weather events do not disprove a trend.
- Confusing climate change with the ozone hole; correct by linking climate change to greenhouse gases and the ozone hole to chlorofluorocarbons.
- Saying the temperature rise is the only cause of climate change; correct by stating it is a major cause while other natural factors also operate.
- Listing only one effect; correct by covering environmental, economic and social effects.
- Treating every effect as certain and identical everywhere; correct by saying effects vary by region and depend on the scale of warming.
- Confusing cause and effect, such as saying sea-level rise causes melting ice; correct by saying melting ice and thermal expansion cause sea-level rise.
- Confusing climate change with the ozone hole; the correction is that ozone depletion is caused by CFCs and is a separate issue from greenhouse warming.
- Listing only one or two effects when four are required; the correction is to prepare four clearly different examples and check each is genuinely distinct.
- Treating weather and climate as the same; the correction is that weather is short-term local conditions while climate is the long-term pattern.