Climate Change (OCR Gateway GCSE Chemistry: Combined Science)

• The 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 industrialization
• 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 → energy + H₂O + CO₂

• 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
• There is a clear correlation between both factors as shown in the graph below.

Graph showing the steady increase in atmospheric CO₂ since 1700

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

Uncertainties in the Evidence

• 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

Effects on Climate Change

• The vast majority of climate scientists agree that increasing levels of greenhouse gases are causing the average temperature of the Earth to increase
• Temperature increases are leading to climate change
• Climate change is when there is a long term shift in world wide weather patterns and conditions

Rising Sea Levels

• The melting of the polar ice caps and glaciers is leading to rising sea levels
• This results in destructive erosion to coastal regions, flooding of wetlands and habitat destruction for birds, fish and plants
• Low lying cities are likely to see increased flooding and permanent loss of usable land without expensive barrier systems
• Increased soil salinity is also a consequence of rising sea levels

Frequent and intense droughts

• Some regions are seeing devastating droughts leading to crop failure and collapse of agricultural production
• Food production is greatly compromised leading to hardship and starvation

Storms

• The intensity of storms is increasing
• Warmer ocean surfaces mean more moisture is entering the atmosphere so storms and hurricanes are more energetic and destructive

Extreme heat waves and rainfall

• Extreme weather events are becoming more frequent resulting in great loss of life and destruction of infrastructure and ecosystems
• Changing rainfall patterns are leading to uneven distribution of freshwater supplies
  • Lack of reliable freshwater supplies results in economic and political instability as neighbouring countries compete for dwindling resources

Mitigation Strategies

• Ultimately, many people believe that reducing the global carbon footprint will be too expensive and not enough to tackle climate change, so that climate mitigation strategies should be adopted hand in hand with carbon footprint reduction
• Climate mitigation refers to adapting to a changing climate rather than trying to change the climate, for instance:
  • Changing the type of crops grown in different regions
  • Investing in flood defence systems or building houses on stilts
  • Changing building infrastructure to make it more resistant to extreme weather
  • Repurposing land vulnerable to flooding
  • Using heat sinks to make buildings more efficient

• These are challenging issues, but humans are resilient and there is every reason to believe that change can and will happen, but it may be a bumpy road ahead