Humanity & Greenhouse Gases (AQA GCSE Chemistry: Combined Science)

• Human activity is contributing to the release of carbon dioxide and methane, both greenhouse gases 
• Methane levels are increasing due to:
  • More waste being sent to landfill sites due to an increasing human population
  • Increased levels of farming 
• Carbon dioxide levels are increasing due to:
  • The increased demand for energy resulting in more fossil fuels being burned

methane  +   oxygen   →  carbon dioxide   +    water 

1. • Deforestation- fewer trees means less carbon dioxide is removed from the atmosphere by photosynthesis

carbon dioxide + water    →     glucose + oxygen 

• 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

Graph to show the increase in carbon dioxide levels since 1700

Graph to show the increase in temperature levels since 1700

• 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