Chapter 6: Climate Change

• Quaternary Period: Period from 2.6 million years ago until today. It has almost always colder than today.
• Woolly mammoths first appeared about 400,000 years ago. They disappeared 4,000 years ago – either because we hunted them, or Earth grew too warm for them, or both.

  
• In the last ice age, sea levels fell by 120 m. So sea floor was exposed as 'land bridges’, allowing humans to migrate. Land bridges joined Britain to Ireland and France.

  
• The last ice age began around 110 000 years ago. Then, about 12 000 years ago, Earth began to warm up. The ice age ended.
• Milankovitch cycles


  Changes in Earth's movements, which affect the climate.
• Sunspots


  The dark spots moving across the Sun: a sign of intense magnetic activity.
• Scientists use different types of clues to study the myriad ways that Earth’s climate has changed during the past 4.6 billion year, including direct measurements.
• Method 1: Ocean sediment ➡️ radiometric dating:

  Ocean sediment builds up layer by layer over millions of years. A core of sediment is drilled from the ocean floor and studied layer by layer, using a method called “radiometric dating”. This tells scientists both the age of layer and what the climate was like then.

  
• Method 2: Ice sheets ➡️ ice cores:


  Scientists drill and extract long tubes of ice, called ice cores, from ice sheets. Ice sheets build up in layers too, from snow. Analysis of ice cores tells scientists when the snow fell, the temperature then - and what gases were in the air.
• Method 3: Tree rings are used to determine the age of a tree.

  
• Natural factors increasing global warming

  • Orbital changes (Wobble, roll and stretch theory)
  • Milankovitch cycles
  • Volcanic activity
  • Solar output
• Greenhouse effect


  A natural process that keeps the planet warm. Without it, humans would not be able to live on Earth
• Human factors increasing global warming

  • Burning fossil fuels (release carbon dioxide) <CO2>
  • Deforestation (trees absorb carbon dioxide during photosynthesis) <CO2>
  • Dumping waste in landfills (waste decomposition produces methane) <CH4>
  • Agriculture (agricultural practices lead to the release of nitrogen oxides) <CH4>
• Milankovitch cycles includes its…

  • eccentricity (how far away from the sun)
  • obliquity (how tilted the earth is)
  • precession (how the axis of the earth wobbles)
• Volcanic eruptions…


  • release large amounts of CO2 into the atmosphere, which is a greenhouse gas.
  • Sulphur dioxide has a cooling effect, which can reduce the amount of solar radiation that reaches the Earth's surface.
• Global Warming is the rise in temperatures around the world.
• Climate Change


  All aspects of climate are changing because the Earth is getting warmer
• Examples of greenhouse gases

  • Methane (CH4)
  • Carbon Dioxide (CO2)
  • Water vapour
  • Sulfur Dioxide
• Impacts of climate change

  • Floods --> Low-lying coasts having more floods; sea levels are rising because ice sheets are melting; the water expands as ice sheets warm
  • Drought --> more rain, more floods; some regions are getting less rain, so they suffer from drought.
  • Heatwaves --> kill crops, wildlife, and people (babies and old people)
  • Wildfires --> destroy homes, and crops, and kill off wildlife.
  • Crop yields --> Climate no longer suits crops.
  • Pests --> crop pests kill crops; spreads malaria; spreads to places that were once cold for them
• Every year, billions of tonnes of dead organisms, and particles carried by the wind and rivers, settle on the ocean floor.
• They drift down through the ocean non-stop, hour after hour after hour.
• Changes in Earth's movements

  
• Sunspots

  
• Mt. Pinatubo in the Philippines erupting in 1991. Global temperatures fell by 0.5°C for 2 years.

  
• Carbon Dioxide in the atmosphere has been increasing since the industrial revolution.
• Methane in the atmosphere is rising due to livestock farming; extracting more fossil fuels and growing rice.
• Process of global warming

  1. The sun sends out energy as sunlight. This warms Earth.
  2. Earth gives out some of the energy again as heat, which warms the air.
  3. Some of the heat escapes to the outer atmesphere.
  4. But some is trapped by greenhouse gases, and does not escape.
  5. The more of a greenhouse gas there is, the warmer the Earth gets.
• Fossil fuels


  coals, oil, natural gas
• Emissions


  Waste gases that go into air.
• By 2017, some countries have managed to reduce their emissions.
• Emissions per person = A country's total emissions of the gas / A country's population
• Treaties that aim to reduce greenhouse gas emissions:

  • The Kyoto Protocol (1997)
  • The Paris Agreement (2016)
• Scientists predict that the global temperature will rise a further 2 - 3°C by 2100.
• • The faster we cut emissions now, the better our chances of surviving and coping in the future.
  • The more slowly we act now, the greater the crisis ahead.
• Ways to Cut Emissions / Strategies

  • Wind farms
  • Solar farms
  • Wave & tidal power plants
  • Electric cars & other vehicles that run on batteries
  • Artificial meat 'grown' in factories
  • Find ways to remove carbon dioxide from the air
  • Reduce the amount of carbon dioxide that's produced
  • Reduce the amount of methane that's produced
  • Stop some sunlight from reaching Earth
  • Help people to adapt to changing climates
• Wind farms


  • Generate electricity from the wind
• Solar farms


  • Generate electricity from sunlight
• Wave & tidal power plants

  • Generate electricity from the movement of the wind & tides
• Electric cars & other vehicles that run on batteries

  • Ideally charged by electricity that's not from power stations that burn fossil fuels
• Artificial meat 'grown' in factories

  • Tastes very like real meat