climate change

• Climate change


  Any significant change in the Earth's climate over a long period
• The climate constantly changes, it always has, and it always will
• Quaternary period


  • The most recent geological time period, spanning from about 2.6 million years ago to the present day
• Climate before the Quaternary period


  • Warmer and quite stable, then things changed a lot
• Climate changes during the Quaternary period

  Shifted between cold glacial periods that last for around 100 000 years, and warmer interglacial periods that last for around 10 000 years
• The last glacial period ended, since then the climate has been warming


  15 000 years ago
• Global warming


  The sharp rise in global temperatures over the last century, a type of climate change
• Evidence for climate change

  • Ice and sediment cores
  • Pollen analysis
  • Tree rings
  • Temperature records
• Ice and sediment cores

  • Ice sheets are made up of layers of ice, one layer formed each year, scientists can analyse the gases trapped in the layers to determine past temperatures
  • Remains of organisms found in ocean sediment cores can also be analysed to extend the temperature record back at least 5 million years
• Pollen analysis


  • Pollen from plants gets preserved in sediment, scientists can identify and date the pollen to show which species were living at that time, and infer past climate conditions
• Tree rings


  • As a tree grows it forms a new ring each year, the thickness of the rings shows what the climate was like, providing a reliable source of evidence of climate change for the past 10 000 years
• Temperature records


  • Since the 1850s, global temperatures have been measured accurately using thermometers, providing a reliable but short-term record of temperature change, historical records can extend the record further back
• Natural factors that cause climate change

  • Orbital changes
  • Volcanic activity
  • Solar output
• Orbital changes


  • Variations in the Earth's orbit around the Sun, including eccentricity, tilt, and wobble, may have caused the glacial and interglacial cycles of the Quaternary period
• Volcanic activity


  • Major volcanic eruptions eject large quantities of material into the atmosphere, some of which reflects the Sun's rays back out to space, causing short-term cooling
• Solar output


  • The Sun's energy output isn't constant, changes in short cycles of about 11 years and possibly longer cycles, reduced solar output may cause cooling in some areas, but is not thought to have a major effect on global climate change
• In recent years, global temperature has risen sharply, this is called global warming
• There's a scientific consensus that human activity is causing global warming through the greenhouse effect
• Greenhouse effect


  Greenhouse gases, such as carbon dioxide (CO2) and methane, absorb outgoing heat from the Earth, so less is lost to space, keeping the planet warm, but increased levels trap more energy and cause the planet to warm up even more
• Human activities increasing greenhouse gas levels

  • Burning fossil fuels
  • Farming livestock
  • Rice paddies
  • Cement production
  • Deforestation
• Deforestation


  Plants remove CO2 from the atmosphere through photosynthesis, when trees are cut down they stop taking in CO2 and CO2 is also released when the trees are burnt or decompose
• Effects of climate change on the environment

  • Glaciers and ice sheets melting, causing sea levels to rise
  • Sea ice shrinking, leading to loss of polar habitats
  • Coastal flooding and erosion
  • Coral reef bleaching
  • Changing precipitation patterns
  • Changing distribution and quantity of species, leading to biodiversity loss
• Effects of climate change on people

  • Increased deaths from heat, but decreased deaths from cold
  • Some areas becoming uninhabitable due to heat, drought, or flooding
  • Water shortages and political tensions over water resources
  • Crop yield changes, affecting food security
  • Increased costs of predicting, reducing impacts, and rebuilding after extreme weather events
• Mitigation strategies to reduce causes of climate change

  • Carbon capture and storage
  • Planting trees
  • Replacing fossil fuels with alternative energy production
• Carbon capture and storage


  • Capturing CO2 from power stations and transporting it to be stored safely, e.g. underground
• International agreements


  • The Paris Agreement aims to reduce greenhouse gas emissions and limit global warming, with countries submitting pledges to reduce emissions
• Adaptation strategies to respond to effects of climate change

  • Changing agricultural systems
  • Managing water supply
  • Coping with rising sea levels
• Changing agricultural systems


  • Planting new crop types more suited to new climate conditions, using biotechnology to create more weather-resistant crop varieties
• Managing water supply


  • Installing water meters, collecting and recycling rainwater and wastewater
• Coping with rising sea levels

  • Improving flood warning systems, building physical flood defences, building raised flood shelters and houses on embankments