Human Activity & Global Climate Change (Edexcel GCSE Geography A)

Causes of the Enhanced Greenhouse Effect

• Human activity is increasing the amount of key greenhouse gases (GHGs) in the atmosphere

  • Carbon dioxide (CO₂) levels in the atmosphere have increased by more than 100 parts per million (ppm) to 422ppm in 2023

  • Methane, nitrous oxide and fluorocarbons (HFCs and CFCs) are also increasing

• Increased amounts of GHGs have led to the enhanced greenhouse effect:
  

  • Less radiation (heat) can escape the atmosphere

  • Average global temperatures have increased over 1°C since pre-industrial times

Enhanced greenhouse effect

Diagram showing the effect of adding more greenhouses gases to the atmosphere

Human Sources of Greenhouse Gases

Fossil fuels 

• Fossil fuels account for almost 50% of global greenhouse gas emissions

• Fossil fuels are used in a number of ways, including industry, transportation, farming and energy production 

Farming

• The production of fertilisers and pesticides uses fossil fuels

• Dairy and beef cattle farming, as well as rice cultivation, increase methane emissions

• Artificial fertilisers release nitrogen oxide into the atmosphere

• Deforestation to clear land for grazing and crops leads to less CO₂ being absorbed during photosynthesis

Industry 

• As well as using fossil fuels, construction, heating, manufacturing, etc. all release greenhouse gases 

• The manufacture of cement releases CO₂

• Cement is made from limestone, which contains carbon

Transport

• The increase in population has led to more cars, buses, trucks, and planes

• Transport uses petrol or diesel, which comes from oil, which is a fossil fuel, and releases CO₂

• Electric vehicles have to be charged using electricity produced by power stations, which release CO₂

Energy production

• Electricity and heat are generated by burning fossil fuels

• Making them the largest contributors to GHG emissions

Negative Impacts of the Enhanced Greenhouse Effect

There are a number of current and potential impacts of climate change

Rising sea levels

• Warmer temperatures cause the water in seas and oceans to expand, increasing the sea level

  • Warm water expands in volume (thermal expansion)

  • Sea levels have risen approximately 23cm since 1880

• Melting ice adds more water

  • Average sea levels have risen 23 cm since 1880

  • Sea levels are forecast to increase a further 30 cm by 2050

• By 2100, global sea levels are predicted to rise between 0.3 and 2 meters 

Effects of a 1m sea level rise 

• Low-lying coastal areas and islands are at higher risk of flooding

  • The Maldives may be uninhabitable by 2050 

• Beach erosion will increase, leading to greater coastal erosion 

• Coastal ecosystems, including coral reefs and mangrove swamps, will be lost

• Saltwater ingress is contaminating freshwater supplies and affecting coastal agriculture

Wildlife changes

• Migration and behaviour patterns of animals affected by changing temperatures

  • Fish species are moving north and south of their usual habitats to seek cooler water

  • Reduced hibernation due to warmer winters

  • Bird migration times have altered

  • Bird nesting is happening earlier

Changing patterns of crop yields

• Wheat and maize yields have negatively impacted most regions since 1960

• Crop yields are estimated to continue reducing by over 20% as temperatures increase

• The effects are that rice and soybean yields have been smaller in all major production regions 

• The largest impact has been on the price and production of food for daily consumption

  • Production has decreased

  • Prices have increased

• A changing pattern of rainfall will also threaten crop production

  • Too little rain and crops will fail

  • Too much rain and crops will rot in the fields

• Suitable areas for agriculture will change

  • Farmers may have to change their crops 

  • Areas that could grow certain crops will have to change

    • Wheat grown in the USA will have to be grown in Canada

    • This would negatively affect the USA's economy while boosting Canada's

• Reduced availability of water will mean that irrigation is limited or impossible

• Food shortages will lead to malnutrition and famine

Glacial retreat

• Most glaciers around the world have shrunk since 1850

• Mountain glaciers are an important source of water for many people

  • Glacial retreat in the Andes threatens water supplies of up to 50 million people

  • A large glacial loss in the Himalayas could affect millions of people living in China and India

  • Glaciers are important for the tourist industry

Extreme weather events

• Since the 1980s, there has been an increase in extreme weather events

• Particularly floods, storms, and extreme temperatures

• The frequency and length of droughts are increasing

• Dry conditions lead to an increased risk of wildfires

• Rising sea levels, together with increased storms, lead to increased flooding risk