Human activities which contribute to an increase in greenhouse gases in the — AQA GCSE Chemistry
Verified courseTeaching note checked against the official specification.
Human activities which contribute to an increase in greenhouse gases in the explained
Human activities which contribute to an increase in greenhouse gases in the covers 6 specification points, including Carbon dioxide methane.
Read the full explanation
and Students should be able to recall two human…. Open a point below for its explanation and revision guidance.
Some human activities increase the amounts of greenhouse gases in the atmosphere. These include: carbon dioxide methane.
Greenhouse gases absorb outgoing infrared radiation, warming the atmosphere. Human activities raise their concentrations. Carbon dioxide increases mainly by burning fossil fuels such as coal, oil and natural gas, and by deforestation, because trees remove carbon dioxide during photosynthesis. Methane increases through livestock farming, especially cattle and sheep, rice paddy fields, landfill sites and anaerobic digestion of waste. For example, a coal-fired power station releases carbon dioxide, while a cattle farm releases methane. These gases trap heat, so higher concentrations strengthen the greenhouse effect. You should link each activity to the gas it releases and explain the mechanism briefly.
Students should be able to recall two human activities that increase the amounts of each of the greenhouse gases carbon dioxide and methane.
You need to recall two human activities for carbon dioxide and two for methane. For carbon dioxide, burning fossil fuels in power stations, factories and vehicles releases carbon dioxide, and deforestation reduces the removal of carbon dioxide by photosynthesis. For methane, livestock farming, especially cattle and sheep, releases methane during digestion, and landfill sites release methane as organic waste decomposes anaerobically. Rice paddy fields also release methane. A useful method is to group activities by gas: fossil fuels and deforestation for carbon dioxide; livestock and landfill for methane. In an exam, name the activity and the gas it increases.
Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will result in global climate change.
Peer-reviewed evidence means research checked by other experts before publication. Many scientists use this evidence to conclude that human activities, such as burning fossil fuels and farming livestock, increase greenhouse gas concentrations. These gases absorb infrared radiation, so more heat is trapped and the average surface temperature rises. This warming is expected to cause global climate change, including altered weather patterns, rising sea levels and shifts in habitats. For example, ice core data and temperature records show a correlation between rising carbon dioxide and global temperature. The statement uses ‘many scientists believe’ because scientific conclusions are based on the weight of evidence, not absolute proof.
However, it is difficult to model such complex systems as global climate change.
Global climate is a complex system with many interacting parts, including the atmosphere, oceans, ice, land and living things. These parts affect one another through feedback loops, such as melting ice reducing reflectivity and causing more warming. Because of this complexity, computer models that predict climate change have limitations. They may simplify processes, rely on incomplete data, or struggle to represent clouds and ocean currents accurately. This makes long-term predictions uncertain. For example, different models may give a range of possible temperature rises. Scientists improve models by comparing them with observations and updating them as new peer-reviewed evidence emerges.
This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased.
Scientific evidence about greenhouse gases and climate is complex, so media reports often simplify it into models, speculation or opinion. A simplified model, such as a diagram showing only carbon dioxide and temperature, omits methane, water vapour and natural variation. Speculation goes beyond the data, for example claiming a single cold winter disproves warming. Opinion may reflect a group's interests. Bias arises when a report selects only part of the evidence, such as one favourable study, or gives unequal weight to voices. Students should ask what evidence is shown, what is missing, who produced it and whether the conclusion follows. This links to evaluating reports and recognising uncertainty.
Students should be able to: evaluate the quality of evidence in a report about global climate change given appropriate information describe uncertainties in the evidence base recognise the importance of peer review of results and of communicating results to a wide range of audiences.
When you read a report about global climate change, judge the evidence rather than accept the conclusion. Check the source, whether data are peer reviewed, how many measurements and how long a record they cover, whether the method is reproducible and whether the conclusion follows. Uncertainty is normal: measurements have limits, natural variation is large, and models simplify reality, so scientists give ranges rather than single values. Peer review means other experts examine methods and conclusions before publication, which improves quality but does not prove a claim. Communicating results to the public, policymakers and other scientists allows scrutiny and informed decisions. A useful method is to list strengths, weaknesses and what further evidence would reduce uncertainty.
Your focus
- Identify at least two human activities that increase carbon dioxide concentration.
- Identify at least two human activities that increase methane concentration.
- Describe how greenhouse gases absorb infrared radiation and warm the atmosphere.
Show all 18 objectives
- Recall two human activities that increase carbon dioxide concentration.
- Recall two human activities that increase methane concentration.
- Distinguish between activities that release carbon dioxide and those that release methane.
- Explain what peer-reviewed evidence is and why it is important.
- Describe how human activities can lead to an increase in surface temperature.
- Outline at least one expected consequence of global climate change.
- Describe why global climate is a complex system.
- Explain at least two reasons why climate models have limitations.
- State how climate models can be improved using observations and peer-reviewed evidence.
- Identify parts of the evidence that a simplified media report may omit.
- Explain how selection of evidence can produce bias in a report.
- Distinguish between evidence-based conclusions, speculation and opinion.
- Evaluate the quality of evidence in a supplied climate report using stated criteria.
- Describe sources of uncertainty in climate evidence.
- Explain why peer review and communication to wide audiences matter.
Human activities which contribute to an increase in greenhouse gases in the exam tips
Marking Points
- Carbon dioxide is released by burning fossil fuels such as coal, oil and natural gas in power stations, factories and vehicles.
- Deforestation reduces photosynthesis, so less carbon dioxide is removed from the atmosphere, increasing its concentration.
- Methane is released by livestock farming, particularly cattle and sheep, through digestion and waste.
- Methane is released from rice paddy fields, landfill sites and anaerobic decomposition of organic waste.
- Greenhouse gases absorb infrared radiation emitted by the Earth, so increasing their concentration strengthens the greenhouse effect.
- Burning fossil fuels such as coal, oil and natural gas releases carbon dioxide.
- Deforestation reduces carbon dioxide absorption by trees, increasing atmospheric carbon dioxide.
- Livestock farming, especially cattle and sheep, releases methane through digestion and waste.
- Landfill sites release methane as organic waste decomposes without oxygen.
- Rice paddy fields release methane due to anaerobic decomposition in waterlogged soil.
- Peer-reviewed evidence is research that has been checked by other scientists before publication.
- Human activities increase greenhouse gas concentrations, which strengthens the greenhouse effect.
- Increased greenhouse effect leads to a rise in average surface temperature.
- Rising temperatures are expected to cause global climate change, such as changing weather patterns and sea level rise.
- The conclusion is based on the weight of peer-reviewed evidence, so many scientists accept it.
- Global climate involves many interacting components, such as atmosphere, oceans, ice and land.
- Feedback mechanisms, such as ice melting and reduced reflectivity, make the system complex.
- Computer models simplify or omit some processes, leading to uncertainty in predictions.
- Incomplete data and limited understanding of some processes make modelling difficult.
- Models are improved by testing against observations and revising with new peer-reviewed evidence.
- Identify that media coverage may use simplified models that omit some greenhouse gases, feedbacks or natural factors.
- Explain that speculation is a claim going beyond the available evidence, such as predicting a specific local effect from global data.
- Explain that opinion is a personal or group viewpoint rather than a conclusion drawn from the full evidence base.
- Describe bias as selecting or emphasising only part of the evidence, or presenting one side more strongly.
- Use a specific example, such as a headline based on one study while ignoring several others, to show how bias can arise.
- Suggest how a reader can check a report, for example by finding the original peer-reviewed study and comparing several sources.
- Judge evidence by source, peer review, sample size, timescale, reproducibility and whether the conclusion follows from the data.
- Describe uncertainty as a range or limitation arising from measurement, natural variation or model simplification, not as a failure of science.
- Explain that peer review involves independent experts checking methods, data and conclusions before publication.
- Explain that communicating results to scientists, policymakers and the public allows scrutiny, replication and informed decisions.
- Use a specific example, such as a long temperature record from many stations being stronger evidence than one local measurement.
- Suggest how uncertainty could be reduced, for example by more measurements, longer records or improved models.
Examiner Tips
- 💡When asked to name activities, give specific examples such as burning coal or rearing cattle rather than vague terms like pollution.
- 💡Link each activity to the correct greenhouse gas in the same sentence to secure both marking points.
- 💡Use the term infrared radiation when explaining how greenhouse gases warm the atmosphere.
- 💡Make a two-by-two table in your notes: carbon dioxide activities and methane activities, with two examples each.
- 💡In the exam, write the gas name next to each activity so the examiner can see the link clearly.
- 💡If you cannot recall a second example, use rice paddy fields for methane or deforestation for carbon dioxide.
- 💡Use the phrase peer-reviewed evidence to show you understand why the conclusion is reliable.
- 💡Link the increase in greenhouse gases to the enhanced greenhouse effect and then to surface temperature rise.
- 💡Give a consequence of climate change, such as melting ice or changing rainfall, to show understanding of global climate change.
- 💡Use the word complex when explaining why modelling is difficult.
- 💡Give a specific reason, such as incomplete data or simplified processes, rather than saying it is just hard.
- 💡Mention that models are tested against real observations to improve reliability.
- 💡When asked to evaluate a report, quote or paraphrase a specific part of the supplied information and say what is missing or biased.
- 💡Use the words evidence, uncertainty and peer review accurately; do not simply say the media is wrong.
- 💡Link each criticism to a consequence, such as the public forming an opinion from incomplete evidence.
- 💡Use the supplied information: name the specific strength or weakness you can see rather than giving general opinions.
- 💡Structure an evaluation as strengths, weaknesses and a justified overall judgement.
- 💡When describing uncertainty, give a cause and an effect, such as limited stations leading to a wider range.
Common Mistakes
- Confusing the gases released by different activities, such as saying cattle release carbon dioxide; correct this by linking livestock to methane and fossil fuel combustion to carbon dioxide.
- Thinking deforestation directly releases carbon dioxide only; correct this by explaining that it also removes fewer trees, so less carbon dioxide is absorbed.
- Describing the greenhouse effect as a human-made process; correct this by stating it is a natural process strengthened by human activities.
- Giving only one activity for a gas when two are required; correct this by learning two distinct examples for each gas.
- Mixing up the gases, such as saying landfill releases carbon dioxide; correct this by associating landfill with methane.
- Using vague terms like farming without specifying livestock; correct this by naming cattle or sheep as methane sources.
- Stating that all scientists agree without qualification; correct this by saying many scientists accept the conclusion based on evidence.
- Confusing weather with climate; correct this by defining climate as long-term average conditions.
- Claiming the greenhouse effect is entirely human-made; correct this by explaining it is natural but enhanced by human activities.
- Thinking models are useless because they are uncertain; correct this by explaining they provide useful projections with ranges of uncertainty.
- Believing climate change is not happening because models are imperfect; correct this by distinguishing between uncertainty in details and the overall trend.
- Ignoring feedback loops; correct this by giving an example such as melting ice reducing reflection of sunlight.
- Treating all media reports as equally reliable; correct by checking whether the report cites peer-reviewed evidence and whether other studies agree.
- Assuming that a simplified model is wrong; correct by recognising that a model can be useful if its limitations are stated and it fits the purpose.
- Confusing speculation with a prediction based on data; correct by asking whether the claim follows from measurements or goes beyond them.
- Saying peer review proves a result is true; correct by saying it checks quality and reduces the chance of error, but conclusions can still be revised.
- Treating uncertainty as meaning scientists know nothing; correct by explaining that uncertainty is a quantified range around a well-supported finding.
- Judging a report only by whether you agree with it; correct by checking the evidence, method and source instead.