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Climate Change

Earth’s Changing Climate

  • Climate change is any significant change in the Earth’s climate over a long period; it constantly changes
  • Earth is 4.5 billion years old; scientists divide this into different geological time periods, we are currently in the Quaternary period
  • This period began 2.6 million years ago and is divided into two epochs
    • The Pleistocene epoch lasted from 2.6 million years ago to 11 700 years ago
    • The Holocene epoch began 11 700 years ago
  • Prior to the Quaternary period, the Earth’s climate was warmer and more stable
  • Temperatures fluctuate in the Quaternary period; colder glacial periods last approx. 100 000 years and warmer interglacial periods last approx. 10 000 years
    • The last glacial period ended around 15 000 years ago; since then the climate has been warming
  • Graphs are used to show climate change over periods of time, however the different periods of time used allow for different conclusions to be drawn
  • Global warming is the term used to describe the sharp rise in global temperatures over the last century – it’s a type of climate change

Evidence for Climate Change

  • Scientists can work out how the climate has changed over time using various methods
  • Sea ice positions have been monitored using satellite images since 1979
    • By studying the sea ice maximum and sea ice minimum, scientists can tell how ocean temperatures are changing
      • Sea ice forms around the poles in the winter when ocean temperatures fall below -1.8°C and melts during the summer when its warmer
    • The data is very reliable, but accurate records do not go far back
  • Ice cores are extracted from ice sheets and the snow is tested to give scientists information
    • Layers of fallen snow are gradually compressed into ice, forming one layer each year
    • Scientist drill into ice sheets to extract long cylindrical cores of ice
      • Lighter coloured layers show snow laid down in the summer and darker colour layers show snow laid down in the winter as strong winds mixed dust into it, making it darker
      • 18O, a heavier isotope of oxygen is found in gas bubbles from warmer periods and 16O, a lighter isotope of oxygen is found in gas bubbles from colder periods
      • Lots of CO2 in gas bubbles suggests warmer periods
    • One ice core from Antarctica shows the temperature changes over the last 400,000 years
    • Data collected from ice cores is very detailed and reliable
  • Global temperatures have been measured accurately using thermometers since the 1850s
    • This gives a reliable, but short-term record of temperature change
    • Weather stations are not evenly distributed so data from some areas is patchy
  • Historical records can be drawn from paintings and diaries
    • Diaries often contain information about weather and harvests and the date is extremely useful
      • Long snowy winters suggest colder periods
      • Early harvests suggest warmer periods
    • Paintings of fairs and markets on frozen rivers show that winters in Europe were regularly much colder 500 years ago than they are now
    • Diaries and paintings aren’t very reliable as they show one person’s viewpoint and they don’t go very far back

Causes of Climate Change

  • Sun spots are cooler areas of the Sun’s surface that are visible as dark patches
    • These are temporary and caused by magnetic storms
    • They increase the energy output of the Sun, causing the Earth to warm up
    • Sunspots come and go in cycles of about 11 years
      • Some cycles are longer, several hundreds or thousands of years
    • Periods when there are very few sunspots and solar output is reduced may cause the Earth’s climate to become cooler in some areas
      • The Little Ice Age (1300-1870) is linked to fewer sunspots
      • The Medieval Warm period (950-1250) is linked to more sunspots
    • Most scientists think that changes in solar output don’t have a major effect on global climate change
  • Volcanic eruptions eject large quantities of material into the atmosphere
    • Some particles reflect the Sun’s rays back out to space so the Earth’s surface cools
    • CO2 is a greenhouse gas and massive quantities of it could contribute to global warming
    • Volcanic activity may cause short-term changes in climate
      • In 1991, Mount Pinatubo’s eruption caused Earth’s average temperature to fall by 1°C over the following two years
      • The Little Ice Age (1300-1870) is linked to more volcanic activity
      • The Medieval Warm period (950-1250) is linked to less volcanic activity
  • Milankovitch cycles are variations in the way the earth moves around the sun
    • Eccentricity (orbit) describes the changes in the shape of the Earth’s orbit
      • The path of the Earth’s orbit around the Sun changes from an almost perfect circle to an ellipse and back again every 96 000 years
      • Colder periods tend to occur in a circular orbit and warmer periods in an elliptical orbit
      • Orbital changes may have caused the glacial and interglacial cycle of the Quaternary period
    • Obliquity (tilt) describes the changes in how the Earth tilts on its axis
      • The Earth’s tilt changes from 21.5° to 24.5° every 41 000 years
    • Precession (wobble) describes the amount the Earth wobbles on its axis
      • The force of gravity from the Sun and moon cause the axis to trace a circular shape which goes from one extreme to the other over a period of 23 000 years
    • These cycles affect how far the Earth is from the Sun, and the angle that the Sun’s rays hit the Earth; changing the amount of solar radiation received by the Earth
      • Obliquity and precession affect how much solar radiation is received at different latitudes at different times of year

The Greenhouse Effect

  • The natural greenhouse effect is essential for keeping Earth warm
    • Energy comes from the sun as short-wave radiation
    • Most energy passes through naturally occurring greenhouse gases
    • Earth’s surface is warmed
    • Some energy is reflected out to space as long-wave radiation
    • Long wave radiation does not pass through greenhouse gases as easily as short-wave radiation
      • Some energy escapes back out to space
      • Some energy is absorbed by greenhouse gases
      • Some is reflected to Earth
    • Earth is warm enough for life to exist
  • Greenhouse gases include carbon dioxide, methane and water vapour
  • The rate of the recent rise in global temperatures is unprecedented and the scientific consensus is that human activities are causing global warming by making the greenhouse effect stronger; this is called the enhanced greenhouse effect
  • Various activities contribute to the enhanced greenhouse effect
    • Farming of livestock produces lots of methane and rice paddies emit methane because of flooded fields
    • Burning fossil fuels like coal, oil, natural gas and petrol in thermal power stations or in cars release carbon dioxide
    • Cement production produces carbon dioxide because cement is made of limestone which contains carbon
    • Deforestation reduces the amount of carbon dioxide taken in by trees and when they are burnt carbon dioxide is emitted
  • Different gases have different global warming potentials as the same quantities can absorb different amount of radiation
    • Carbon dioxide accounts for 60% of the enhanced greenhouse effect
    • Methane accounts for 15% of the enhanced greenhouse effect
      • There is little of it, but it is 25X more efficient than CO2
    • Chlorofluorocarbons account for 15% of the overall effect are the only human-made greenhouse gases
      • There are tiny amounts of it, but it can be 15 000X more efficient than CO2
      • The main sources are air-conditioning, fridges, aerosols and foam packaging
    • Nitrous oxide accounts for 6% of the enhanced greenhouse effect
      • It is 250X more efficient than CO2
      • The main sources are agricultural fertilisers and car exhausts
  • Most scientists agree that the increased carbon dioxide levels caused by human activity (mainly in ACs) are the reason for global warming
    • Lifestyles in ACs use lots of fuel and energy in things like cars, aeroplanes, food, phones and other electrical products
    • EDCs like China and India are emitting more CO2 as they develop industry and their people start to want a lifestyle like that enjoyed by people in ACs
  • Looking at each country’s share of total CO2 emissions is misleading due to the different population sizes
    • Looking at a country’s CO2 emissions per capita is more sensible as it takes population size into account
    • However, it is still misleading as it doesn’t consider the fact that some countries produce a lot of CO2, making products like cement, clothes and electronic tablets, which are used by people in ACs
    • The carbon footprint of a country is the most sensible way to analyse data of CO2 emissions as it considers the fact that the lifestyle of people in ACs depends on CO2 emissions in EDCs and LIDCs

Global Impacts of Climate Change

  • There are a range of social, economic and environmental impacts of climate change worldwide such as those resulting from sea level rise and extreme weather events
  • In some areas, peoples’ lives and homes are at risk due to climate change
    • Reduced rainfall means wildfires pose an increased threat; they damage homes and kill people
    • People may be unable to inhabit areas if they become too hot and dry
    • People may be unable to inhabit low-lying coastal areas lost to seas and floods
      • Many small islands, such as the Maldives, are susceptible to being flooded, making it unlikely to be habitable in 100 years
    • The frequency and severity of extreme weather events could increase
      • In the summer of 2003, Europe suffered from record high temperatures, it was the hottest summer in 500 years
        • Over 20,000 people died
        • Hospitals and mortuaries overflowed
        • The farming industry lost £10billion because crops and animals died
        • Railway lines buckled, and roads melted
        • The London Eye closed for a day because the cabins were too hot
      • In November 2013, Typhoon Haiyan devastated the Philippines
        • 4 million refugees were created
    • Migration to safer areas is caused by climate change and may lead to overcrowding
    • Changing rain patterns could reduce water availability
      • Some areas have less rainfall, others have very heavy rainfall that means freshwater runs back into oceans quickly, melting glaciers put more freshwater into the oceans and more freshwater evaporates
      • About 1 billion people will not have enough water by 2025 due to the lack of freshwater
    • Political tensions could be caused between countries with rivers as borders
    • Low crop yields could increase malnutrition, ill health and death from starvation
    • Water flooding leads to water becoming more contaminated by human and industrial waste, so more people will die of diseases such as typhoid, dysentery and cholera
      • Diarrhoea kills 1.5 million children under 5 each year
    • Warmer temperatures increase lifespan and survival of insects like mosquitos, increasing infectious diseases such as malaria internationally
  • In some areas, countries’ economies will shrink due to the expenses of climate change
    • As extremes in weather conditions increase, more money need to be spent on predicting them, protecting the country from them and rebuilding after them
    • Rising temperatures cause areas of permafrost to melt, leading to the collapse of building and pipelines build on them
      • However, natural resources would be extracted easier from unfrozen ground
    • Some crops suffer, e.g. maize crops have shrunk due to warming; other crops benefit, e.g. higher latitude countries
      • Rice exports from Vietnam will decrease
        • About half of Vietnam’s rice is grown in the Mekong Delta
        • With sea levels rising, there are more floods, which makes the water too salty to grow rice in
        • By 2050, the decrease in rice production could affect 1 million people and cost $17billion
      • Coffee exports from Ethiopia will decrease due to the Coffee berry borer beetle which thrives in warmer temperatures
        • 700 000 families depend on coffee for their income
      • In 2011 Russia banned exports of wheat after a heatwave damaged its crops
      • It is thought that the crop yields in sub-Saharan Africa could be 22% less by 2050
    • Water shortages may affect generation of hydroelectric and thermal power as thermal power stations require lots of water
    • Tourism in some countries could decrease
      • The Maldives could be underwater within 100 years
      • Less skiing due to less snow
  • In some areas, habitats and species are at risk due to climate change
    • Between 2005-2100, temperatures are expected to rise by 0.3-4.8°C
    • Warmer temperatures cause thermal expansion, melting glaciers and melting ice caps which duly cause the sea level to rise
      • Greenland and Antarctica are especially susceptible to melting ice sheets
    • Sea ice shrinking leads to the loss of polar habitats
    • Water becomes more acidic due to increased CO2, reducing the number of fishes
    • Species decline due to warming
      • Coral reefs suffer from bleaching due to increasing water temperatures
      • Polar bears mainly eat seals, but hunt from the ice
        • When there is less ice, they must swim further to find food, which takes more energy
        • They also need to rest on ice, so they can save energy, especially in the winter when there is less food
        • Lack of food is the main reason why polar cubs die, and can stop reproduction
    • Warmer temperatures increase the frequency and severity of extreme weather such as tropical storms, heatwaves and droughts
    • Precipitation patterns change
      • Lake Chad in central Africa was one of the world’s greatest lakes but is shrinking
        • Droughts meant evaporated water was not replaced by rainfall
        • Rainfall in the whole region has reduced by 5-10mm a year
        • Less rainfall means that people take more water from the lake
        • It is used by 30 million people in Chad, Nigeria, Niger and Cameroon to provide drinking water, food and income
        • It is used for fishing and provides water for crops and animals
    • The distribution and quantity of some species could change, and biodiversity could decrease
      • Some species migrate to higher latitudes for cooler temperatures
      • Some species become extinct if their habitats are destroyed or damaged
      • Up to a quarter of all plant and animal species could be extinct by 2050
  • Regional impacts of climate change differ in each continent
    • In Africa there are water shortages and drought, reduced crop production and an increase in diseases
    • In Europe there are economic losses due to flood damage, a reduction in water availability especially in southern Europe and a threat to human health
    • In Asia there is coastal and urban flooding, a threat to human health and water and food shortages
    • In Australasia there are economic losses due to flood damage, damage to coral reef systems and water shortages
    • In North America there is property damage and death from wildfires, heat-related deaths and urban floods
    • In Central and South America there is reduced water availability, flooding and landslides and decreased food production
    • In Polar regions there are threats to ecosystems and an indigenous way of life

Impacts of Climate Change on the UK

  • There are a range of social, economic and environmental impacts of climate change within the UK such as the impact on weather patterns, seasonal changes and changes in industry
    • The average temperature will increase with warmer but wetter winters and warmer but drier summers
  • Ill-health, water shortages and floods are social impacts of climate change
    • Deaths from cold-related illnesses may decrease but more heat-related illnesses will need to be treated
    • Water shortages will occur affecting mostly London and the south-west
      • Over a quarter of the UK population live there, creating a huge problem
      • Restrictions on water may be implemented such as hosepipe bands, or cuts to domestic water supplies
    • Drier summers will affect water availability
      • Particularly in south-east England where population density is increasing
    • Extreme rainfall increases the chances of flooding from rivers, coastal flooding and flash floods
      • Particularly those on estuaries and low-lying coastal areas
      • London could experience serious flooding with the Thames Flood Barrier unable to cope
      • £120 billion worth of infrastructure is at risk of flooding
      • Coastal towns have some of the highest numbers of elderly people who are least equipped to cope
      • In the summer of 2007, the UK suffered its wettest May and June since records began in 1776
        • Tewkesbury, Gloucestershire was affected badly when two months’ worth of rain fell in 14 hours
        • Three people dies, 1800 houses were completely cut off and 50 000 had no electricity
        • A water treatment works was flooded leaving 135 000 houses without water for 17 days
  • Changes in tourism, agriculture and fishing have a negative effect on the economy
    • Warmer weather could boost and reduce tourism in different areas
      • More people may decide to holiday at home, on English beaches
      • In places such as the Cairngorms, tourism will decline due to lack of skiing
      • The Tourism Comfort Index (TCI) measures how suitable the climate is for outdoor activities; Cornwall, Devon and Somerset are predicted to reach excellent by 2050
    • Increased risk of flooding means more money will need to be spent to prevent coastal erosion and repair damaged areas
      • Currently, damage caused by rivers and the sea flooding cost the UK about £1.3 billion a year but this could increase to up to £12 billion a year by 2080
      • Floods across the country in spring / summer 2007 caused widespread damage to homes, businesses and transport networks, costing £3.2billion
    • Temperature increase could create a better climate for farming whilst reduced rainfall and droughts cause issues
      • Temperature increase and seasonal changes lead to a longer growing season, increasing productivity of some crops
      • There would be opportunities for growing new types of food
      • New crops adapted to warmer climates could be grown in southern England, but reduced rainfall and droughts would increase the need for irrigation and water storage
      • Farmers in the south will be able to grow crops like sunflowers, olives and melons
    • Conditions are like those in France 20 years ago, creating a better environment for vineyards
      • When Prince William and Kate married, English wine was served
      • In 16 years, England had won 14 international trophies for sparkling wines
      • From 2004-14, land use for vineyards doubled with a record 6.4 million bottles sold in 2014 – a 43% increase on 2013’s record of 4.45 million bottles
      • However, 2012 was a bad year for wine with only 1.03 million bottles produced due to floods
    • Water shortages could shut down power stations which need large quantities of water
    • Extreme weather as well as fish population and species changes will affect fishermen and fishing infrastructure
      • Infrastructure will be put at risk by an increase in extreme weather conditions
      • The change in fish populations and species in UK water will affect the livelihood of fishermen
  • The climate, extreme events, sea level and wildlife are all changing the environment
    • The average temperature along with winter rainfall will increase whilst summer rainfall will decrease
      • The increased temperature will be greatest in southern England where the average summer temperature is projected to increase by 3.9°C by 2080
      • On the western side of the UK winter rainfall is expected to increase by 16%
      • In southern England, summer rainfall is expected to decrease by 23%
    • Droughts and flooding will become more common
      • Droughts are expected to be more frequent and intense, especially in Southern England
      • Flooding will become more frequent due to increased rainfall and sea level rise
        • Birds like the Lapwing and Redshank suffered when breeding grounds were flooded in spring / summer 2007
    • Sea level is expected to rise by 12-76cm by 2095 leading to the loss of habitats
    • The loss of habitats and changing climate will upset the balance of natural ecosystems and lead to species migration and extinction
    • Some species have already left their original habitats and moved north to areas with lower temperatures