Climate Change Causes & Effects (AQA GCSE Geography)

• The global climate conditions of the Earth range over time leading to colder and warmer periods
• The last 2.6 million years are the Quaternary period when there have been 60 cold periods and warmer interglacial periods
• The last ice age ended approximately 12,000 years ago
• The evidence for these changes comes from:
  • Ice cores which trap ash, air bubbles and microbes
  • Preserved pollen
  • Historical sources such as diaries, art and weather records
  • Tree rings

Recent climate change

Recent evidence for climate change

• As well as the historical changes in climate there is more recent evidence of climate change, including:
  • Glaciers reducing in size and melting ice: Arctic Sea ice is at an all-time low
  • Rising sea levels: 
    • Melting ice adds more water
    • Warm water expands in volume
  • Plant and tree flowering patterns are changing
  • Bird migration times have altered
  • Shorter hibernations
  • Bird nesting occurring earlier

The greenhouse effect

• The greenhouse effect is essential to the survival of life on Earth:
  • Greenhouse gases in the atmosphere allow short-wave radiation from the sun through to the Earth's surface
  • The greenhouse gases absorb some of the long-wave radiation (heat) and stop it from radiating out into space
  • This maintains the Earth's average temperature
  • Without the greenhouse effect the average temperature would be -18°C

Greenhouse gases from natural sources  

• Water vapour: Evaporation from the oceans/seas and plants
• Carbon dioxide: Volcanic eruptions, wildfires and respiration
• Methane: Emitted from oceans and soils as part of decomposition, termites also emit methane
• Nitrous oxide: Soils and oceans

Causes of Natural Climate Change

The Greenhouse Effect and The Enhanced Greenhouse Effect

Human Sources of Greenhouse Gases

Fossil fuels 

• Fossil fuels account for almost 50% of global greenhouse gas emissions
• Fossil fuels are used in transportation, construction, heating, manufacturing and energy production 

Agriculture

• Deforestation to clear land for grazing and crops leads to less CO₂ being absorbed during photosynthesis
• The production of fertilisers and pesticides uses fossil fuels
• Increased raising of dairy and beef cattle as well as rice cultivation increases methane emissions
• Artificial fertilisers also increase the amount of nitrogen oxide released into the atmosphere

Construction 

•  The manufacture of cement releases CO₂ - it is made from limestone which contains carbon

Transport

• The increasing global population has led to increased numbers of cars, lorries and planes
• Most transport uses petrol/diesel which comes from oil as fuel this releases CO₂

Social effects

• Health
  • Increased temperatures and lack of precipitation may lead to the spread of diseases:
    • Italy has experienced cases of malaria since 2017 when it was previously a malaria free area
    • An additional 280 million people may be affected by malaria
    • Water-borne diseases are more likely to spread
  • Heat waves may become more frequent
    • Heat stroke, dehydration and sunburn increase during heat waves
    • Stagnant air during heat waves increases air pollution levels:
    • Respiratory diseases increase and those suffering from respiratory illnesses such as asthma may be more affected 
  • Increased temperatures negatively affect people with cardiopulmonary diseases
  • Diets may be restricted by food shortages leading to malnutrition and famine
  • Milder winters may lead to fewer winter related deaths
• Employment
  • Loss of job opportunities due to changes in tourism and agriculture
• Homes 
  • Increased flooding due to sea level rise and increased frequency and severity of storms will lead to displacement of large numbers of people

Economic

• Agriculture
  • Farmers may need to change the crop they grow if climate conditions become unsuitable
  • Coastal flooding may lead to salt intrusion
  • Reduced availability of water will mean that irrigation is limited or impossible
  • Food shortages will lead to malnutrition and famine
• Employment
  • Job opportunities may change or decrease because:
    • Tourism may decline in some areas for example ski resorts may close due to the lack of reliable snow
    • Coastal resorts may be at risk of flooding leading to the closure
    • Farmers may have to change the crop they grow or livestock they raise or leave farming
    • In some areas agriculture may decline due to rising temperatures or changing rainfall patterns
    • Declining fishing in some areas due to changing ocean temperatures
• Settlements
  • Settlements in low-lying areas may have to be abandoned or need additional defences against sea level rise:
    • Moving settlements or improving flood defences will be costly

Environmental

• Sea level rise
  • Warmer temperatures cause the water in seas and oceans to expand, increasing the sea level
• Melting ice is adding to the increasing volume of water:
  • Average sea levels have risen 23 cm since 1880
  • Sea levels are forecast to increase a further 30 cm by 2050
• 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 affected
• Saltwater ingress is contaminating freshwater supplies and affecting coastal agriculture

Effects of a 1m sea level rise 

Natural hazards

• Changes in climate patterns are likely to increase the frequency and severity of storms:
  • The 2020 Atlantic hurricane seas were the first most active on record and 2021 was the third most active
• The frequency and length of droughts are increasing
• Dry conditions lead to the increased risk of wildfires:
  • In 2021 Australia, Greece, South Africa, Brazil and USA were just some of the places to experience severe wildfires
  • In September 2021 the USA National Fire Centre reported 44.647 wildfires which had burned 5.6 million acres
• Rising sea levels together with increased storms lead to increased flooding risk

Ecosystem change

• The location of biomes may shift to the north (Northern Hemisphere) and south (Southern Hemisphere) as they rely on specific climate conditions:
  • Polar and tundra biomes are at risk of becoming extinct as they cannot shift any further north/south
• Increasing sea temperatures and ocean acidification have resulted in coral bleaching
• 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
• Mangrove swamps and coral reefs are threatened by rising sea levels
• Pests and disease patterns may change for example malaria carrying mosquitoes may be found at higher latitudes