Global Warming (CIE IGCSE Geography)

Changes in the global climate

• 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 25,000 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 and art
  • Tree rings

Causes of Natural Climate Change

Cause	Impact
Milankovitch Cycles	Long term changes to the Earth's orbit and position. This changes how much solar radiation the Earth receives The Earth's orbit changes every 100,000 years a more circular orbit leads to cooler periods and an elliptical orbit leads to warmer periods The Earth's tilt varies every 40,000 years and the greater the tilt the hotter summers are and colder the winters are Every 24,000 years the Earth wobbles on its axis and this can affect the seasonal temperatures
Volcanic eruptions	Large scale eruptions lead to vast quantities of ash being ejected into the atmosphere Ash in the atmosphere blocks solar radiation leading to a decrease in temperatures
Sunspot activity	Increased sunspot activity is linked to higher average temperatures
Atmospheric dust	Asteroids and meteors entering the Earth's atmosphere may increase the amount of dust which decreases temperatures

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 radiating out into space
  • This maintains the Earth's average temperature
  • Without the greenhouse effect the average temperature would be -18^oC

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

The enhanced greenhouse effect

• Human activity is increasing the number of 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
• 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

Average Global Temperatures

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

Impacts of the enhanced greenhouse effect

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

Homes and settlements

• Increased flooding due to sea level rise and increased frequency and severity of storms will lead to displacement of large numbers of people
• 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

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

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 23cm since 1880
  • Sea levels are forecast to increase a further 30cm 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 is contaminating freshwater supplies and affecting coastal agriculture

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
• Melting of ice caps/glaciers leading changing ocean currents
• Mangrove swamps and coral reefs are threatened by rising sea levels
• Loss of habitats through flooding, drought and wildfires
• Food webs breaking as species numbers are reduced and food sources are decreased
• Loss of plants and vegetation

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

Responses to climate change

• Global warming and climate change require an international response because it affects the entire globe
• Responses can involve either adaptation or mitigation
• In 1988 the Intergovernmental Panel on Climate Change (IPCC) was set up to assess the 'risks of human-induced climate change
• This was followed by several international agreements

Earth Summit, Rio 1992

• Set out aims to stabilise greenhouse gas levels 

Kyoto Protocol 1997

• Delegates from 150 countries agreed to reduce greenhouse gas emissions
• It stated that industrialised countries would reduce emissions to below the levels in 1990
• Developing countries including China and India were exempt from the agreement
• The USA did not sign up for the treaty
• Canada withdrew in 2011 stating that without China and USA the treaty would not work

Paris Agreement 2015

• Global agreement to limit global warming to 2^oC (preferably 1.5^oC) above pre-industrial levels
• Agreement also includes reducing CO₂ emissions by at least 60% by 2050
• Signed by 196 countries including the USA and China (the USA withdrew in 2020 and rejoined in 2021) 

Conference of the Parties (COP)

• The United Nations (UN) holds an annual (every year) meeting to discuss climate change.
• COP26 was held in Glasgow in 2021 
• All nations agreed to take actions to further reduce greenhouse gas emissions

Reducing emissions 

• Emissions can be reduced in a number of ways including;
  • Reducing deforestation 
  • Increasing afforestation
  • Improving energy efficiency in industry and domestic appliances
  • Reducing emissions from industry
  • Improving public transport
  • Electric vehicles
  • Use of renewable energy and nuclear power