Causes & Effects of Climate Change (SQA National 5 Geography): Revision Note

What is climate change?

• The Earth’s climate has changed over time

• It has experienced both warmer and cooler conditions than today

• Significant changes in the past were caused by physical factors

• More recent changes are largely the result of human activity

• Global temperatures have risen sharply

• These changes are happening much faster than natural climate variations

Features of climate change

Rising temperatures

• Global temperatures have increased by around 1.4°C above pre-industrial levels

• The last 10 years have been the warmest on record

Melting ice and rising sea levels

• As temperatures rise, sea ice, glaciers and ice sheets are melting

• Global average sea levels have risen by 21-24 centimetres since 1880

Changing weather patterns

• Some places are becoming wetter while others are getting drier

• More precipitation is falling as rain instead of snow

Extreme weather events

• Extreme weather events such as storms, droughts, heatwaves and wildfires are becoming more frequent and more intense

Physical causes of climate change

Milankovitch Cycles

• Milankovitch cycles are long-term changes to the Earth’s orbit around the Sun

• They affect how much solar radiation the Earth receives

  • Shape: Every 100,000 years, the Earth’s orbit changes shape

    • A  circular orbit leads to cooler periods, while an elliptical orbit leads to warmer periods

  • Tilt: Every 41,000 years, the angle of the Earth’s tilt changes

    • An increased tilt leads to hotter summers and colder winters, while a reduced tilt leads to cooler summers and milder winters

  • Precession: every 26,000 years, the Earth wobbles on its axis

    • This affects the timing and intensity of the seasons

Volcanic eruptions

• Large-scale eruptions eject vast amounts of ash and volcanic gases into the atmosphere

• These block and reflect solar radiation, leading to a fall in global temperatures

  • For example, in 1991, the eruption of Mount Pinatubo in the Philippines lowered global temperatures by 0.6°C for 1-2 years

Variations in solar output

• Sunspots are dark spots that appear on the Sun’s surface

• The more sunspots there are, the higher the average temperatures are on Earth

• The changes are small – between +0.5°C and -0.5°C

Human causes of climate change

Natural greenhouse effect

• The natural greenhouse effect is essential to the survival of life on Earth

• Short-wave radiation from the Sun passes through the atmosphere to heat the Earth’s surface

• The Earth then re-radiates heat as long-wave radiation

• Greenhouse gases in the atmosphere (like carbon dioxide and methane) absorb and trap some of this long-wave radiation, warming the Earth

• Without the natural greenhouse effect, the Earth’s average temperature would be -18°C 

Natural sources of greenhouse gases

• Water vapour – evaporation from oceans, lakes and rivers and transpiration from plants

• Carbon Dioxide – respiration, decay of organic matter, volcanic eruptions and wildfires

• Methane – decay of organic matter in wetlands, emitted by termites during digestion

• Nitrous oxide – emitted by microbes in soils and oceans

The enhanced greenhouse effect

• The process is the same as the natural greenhouse effect

• However, human activities have led to much higher concentrations of greenhouse gases in the atmosphere

• This leads to more heat being trapped and the planet getting warmer

Human sources of greenhouse gases

Carbon dioxide (CO₂)

• Burning of fossil fuels (coal, oil and gas) – for electricity, heat and transport

• Burning of wood

• Deforestation – during photosynthesis, trees remove CO₂ from the atmosphere – fewer trees mean less CO₂removed

Methane (CH₄)

• Agriculture – released by cattle and rice cultivation

• Landfill sites – decomposition of organic waste

Nitrous oxide (N₂O)

• Burning of fossil fuels

• Use of fertilisers

Chlorofluorocarbons (CFCs)

• Used in aerosols, refrigeration units and air conditioning

Key causes of the enhanced greenhouse effect

• Population growth has led to:

  • Higher energy demand

  • Greater food production

  • More urbanisation

  • More industrialisation

  • Increased use of transport

• Energy production

  • Most electricity is produced by burning coal, oil or gas

  • Fossil fuels are also used to provide heating and cooling

  • Burning fossil fuels accounts for two-thirds of global greenhouse gas emissions and 90% of CO₂ emissions

• Agriculture

  • Rearing cattle for meat and growing rice release methane

  • Land is cleared through deforestation to increase food production – this leads to less CO₂ being absorbed during photosynthesis

  • Manufacture of pesticides and fertilisers uses fossil fuels 

  • The use of fertilisers releases nitrogen oxides

• Transport

  • Most cars, lorries, ships and planes use oil as their fuel source, releasing CO₂

• Construction and industry

  • Cement production releases CO₂ – it is made from limestone, which contains carbon

  • Most manufacturing processes use energy generated from fossil fuels to produce good

Global and local effects of climate change

Social Effects

Local scale

• Health risks

  • More intense heatwaves lead to health problems such as heatstroke and higher mortality, especially among older people (e.g. summer 2022, UK)

• Water security

  •  More frequent droughts lead to local water shortages and restrictions 

• Damage to housing

  • More powerful storms cause significant damage to homes and disrupt power supplies (e.g. Storm Éowyn, Scotland, 2025)

Global scale

• Diseases

  • Rising temperatures allow diseases such as malaria to spread to new areas

• Environmental refugees

  • People living in low-lying coastal areas may be forced to flee their homes due to increased risk of flooding and erosion

• Food insecurity

  • Droughts and storms can damage crops, reducing crop yields and leading to food shortages 

Economic effects

Local scale

• Agriculture

  • Extreme weather damages crops and livestock, leading to lower incomes for farmers (e.g. the Beast from the East caused major losses for Scottish sheep farmers in 2018)

• Tourism

  • Reduced snowfall in ski resorts in the Cairngorms leads to fewer visitors and lost revenue

Global scale

• Global food prices

  • Crop failures in major food-producing countries like India and Pakistan cause global food prices to increase

• Global supply chains

  • Extreme weather in manufacturing countries like China can disrupt factories, leading to reduced production of electronic goods

Environmental effects

Local scale

• Ecosystem changes

  • Warmer winters lead to declines in the numbers of Mountain Hares in the UK

• Coastal erosion

  • Places like East Anglia experience faster erosion due to rising sea levels and more frequent storms

Global scale

• Sea level rise

  • Melting of ice sheets and glaciers contributes significantly to sea level rise

• Biodiversity loss

  • Melting sea ice puts species like the polar bear at risk of extinction 

• Loss of habitat

  • Coral bleaching and ocean acidification threaten to wipe out coral reefs by 2100