Humanity & Greenhouse Gases (AQA GCSE Chemistry)

Revision Note

Test Yourself
Stewart

Author

Stewart

Expertise

Chemistry Lead

Human Activity & Climate Change

  • Human population is increasing and with it the global demand for food, water, consumer goods, housing and energy which are supplied with greater and more widespread industrialisation
  • This creates more waste so more landfill sites are needed which increases the amount of methane by decomposition
  • The increased energy demands are met in most cases by the burning of fossil fuels which produces CO2:

Fossil fuel + oxygen → H2O + CO( + energy)

  • Added to this is the effect of deforestation on the amount of CO2 as large areas of forested land are being destroyed for building and agricultural activities
  • Plants and trees remove CO2 during photosynthesis:

6CO2 + 6H2O → C6H12O6 + 6O2

  • Hence their removal increases the amount of atmospheric CO2 as there are less plants available to remove it during photosynthesis
  • Increasing agricultural activities also cause an increase in methane production
  • By analysis of the percentage of CO2 in the atmosphere and the changes in temperature over several hundred years, the evidence for the effects of CO2 on global temperature is convincing
  • The evidence collected by scientists is peer-reviewed by other scientists to make sure that the results are valid and they are confident with the conclusions made
  • Peer-reviewed evidence gives a clear correlation between the percentage of CO2 in the atmosphere and the changes in temperature as shown in the graphs below
  • This has led many scientists to agree that human activities cause an increase in the temperature of the Earth's atmosphere at the surface

Climate Change - Graph CO2 Evolution, IGCSE & GCSE Chemistry revision notes

Graph showing the steady increase in atmospheric CO2 since 1700

Climate Change - Graph Temperature Evolution, IGCSE & GCSE Chemistry revision notes

Graph showing the steady increase in temperature from when accurate records exist

Uncertainty & Historical Error

  • Advances in science and technology mean current levels of CO2 and global temperatures can be determined with a high degree of accuracy
  • Historical data is much less accurate due to the lack of accurate instrumentation and methods
  • Fewer locations would also have been measured due to the lack of satellites and transport
  • There are some methods to estimate past climate conditions, which include:
    • Analysis of the fossil record and tree rings
    • Analysis of gas bubbles trapped in ice from hundreds of thousands of years ago

  • Unfortunately, these methods, while providing at least some data, are not as precise as modern day techniques nor do they provide data which is representative on a global scale
  • The complexity of the Earth’s climate and contributing factors make it a difficult task to produce a working model that clearly shows the link between global warming and greenhouse gases
  • This and other difficulties have led to hype and speculation in the media in recent times in which some scientists have cast doubts on human activity and climate change
  • However, academic surveys have shown that about 97% of climate scientists do believe human activity is causing climate change

Exam Tip

It is important that peer review of research results as well as communication to a wide range of audiences is carried out to dispell myths and misinformation about climate change

You've read 0 of your 0 free revision notes

Get unlimited access

to absolutely everything:

  • Downloadable PDFs
  • Unlimited Revision Notes
  • Topic Questions
  • Past Papers
  • Model Answers
  • Videos (Maths and Science)

Join the 80,663 Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Stewart

Author: Stewart

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.