Climate Change and Human Activity (Edexcel GCSE Geography: B (1GB0))

The greenhouse effect

• The Earth's atmosphere is made up of a number of gases
  • Nitrogen
  • Carbon dioxide
  • Oxygen
  • Water vapour
  • Methane
  • Argon
• 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^oC

The enhanced greenhouse effect

• Human activity is increasing the amount of certain greenhouse gases in the atmosphere:
  • Carbon dioxide (CO₂) levels in the atmosphere have increased by more than 100 parts per million (ppm) to 420ppm in 2020
  • Methane, nitrous oxides and chlorofluorocarbons are also increasing
• Increased amounts of greenhouse gases have led to the enhanced greenhouse effect:
  • Less long-wave radiation (heat) can escape the atmosphere
  • Average global temperatures have increased over 1^oC since pre-industrial times

The greenhouse effect vs the enhanced greenhouse effect

Human Sources of Greenhouse Gases

Greenhouse Gas	Sources from human activity
Carbon Dioxide (CO2)	Burning of fossil fuels: power stations, vehicles Burning of wood Deforestation: trees utilise CO2 in photosynthesis. The fewer trees there are the less CO2 is removed from the atmosphere
Methane (CH4)	Decay of organic matter: manure, waste in landfill, crops
Nitrous Oxide (N2O)	Artificial fertilisers Burning fossil fuels
Chlorofluorocarbons (CFCs)	Aerosols Refrigeration units Air conditioning

Recent evidence for climate change

• As well as the historical changes in climate there is more recent evidence of climate change, including:

Temperature change

• Average temperatures have increased: since the 1980s with all years above the 1961-1990 average

Glacier and Arctic ice decline 

• Glaciers reducing in size and melting ice: Arctic Sea ice is at an all-time low

Arctic Sea Ice 2012 and average 1979-2000 

Rising sea levels

• Melting ice adds more water
• Warm water expands in volume (thermal expansion)
• Sea levels have risen approximately 23cm since 1880

Wildlife

• Plant and tree flowering patterns are changing
• Bird migration times have altered
• Shorter hibernations
• Bird nesting occurring earlier

Extreme weather events

• Since the 1980s there has been an increase in extreme weather events:
  • Particularly floods, storms and extreme temperatures

• Predictions have been made regarding global temperature in the future based on computer modelling of emissions
• The predictions suggest an increase of between 1.9^o and 4.2^oC 
  • This is dependent on whether the human population continues to grow at the same rate and uses fossil fuels

Past and projected changes in global average temperature

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

Effects of a 1m sea level rise 

• It is difficult to predict future impacts of global warming because there are a number of things that are difficult to predict including:
  • The rate the population may grow
  • Use of fossil fuels may increase or decrease
  • People's lifestyles may alter becoming more or less sustainable

The consequences of climate change

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

Social effects

• Health
  • Increased temperatures and a 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 the displacement of large numbers of people

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

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 the 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