climate change

• When we hear the phrase 'climate change', we might think about the changes in our climate over the last few decades: rising temperatures in the air and the sea, more intense tropical storms, severe droughts etc. However, the climate of the Earth has gone through dramatic changes throughout its history.
• Some major fluctuations in temperature have occurred in the Quaternary Period.
• Quaternary Period


  The geological time period that started 2.6 million years ago, and extends into the present
• During the Quaternary period, there have been many fluctuations between the colder glacial periods and warmer interglacial periods.
• Over the last few hundred years, our climate has been warming rapidly. Average global air temperatures have risen by 0.85°C since 1880, and the majority of this warming has occurred since the 1970s. This warming is projected to continue throughout the century.
• Instrumental temperature record


  The record of global temperatures starting around the late 1800s, measured using thermometers
• Scientists have had to discover other ways to indirectly calculate global temperatures in the distant past, such as using deep marine sediment cores and ice cores.
• Ice cores


  • They contain ice crystals that were formed hundreds of thousands of years ago
  • They can be used to calculate gradual changes in temperature over thousands of years
• Marine sediment cores


  • They are used in a similar way to ice cores, but usually show a greater length of time and are generally less accurate
• We know that our climate has been warming in recent years due to our temperature records, but we can also see more evidence of our changing climate in different parts of the world such as sea level rise, decay of glaciers and ice, and changes in ecological patterns.
• Natural factors that have caused changes in Earth's climate

  • Variations in the Earth's orbit around the Sun
  • The effects of volcanic eruptions
  • Changes in the solar output (amount of heat energy) of our Sun
• Orbital forcing


  The influence of Earth's orbit on the climate
• Orbital changes the Earth goes through

  • Eccentricity
  • Obliquity (tilt)
  • Precession
• Sunspot cycle


  An 11-year cycle where the amount of sunspots on the Sun's surface varies from a minimum to a maximum, affecting solar output
• Volcanic winter


  The reduction in surface temperatures caused by a large volcanic eruption, due to volcanic ash and gases in the atmosphere
• There is overwhelming evidence to suggest that humans have been a major cause of climate change, especially the rapid warming since the 1970s.
• Greenhouse effect


  A natural process where greenhouse gases trap the energy from the Sun inside the Earth's atmosphere, which heats the Earth
• Enhanced greenhouse effect


  Higher amounts of greenhouse gases in the atmosphere trapping more heat and causing increased warming
• Human activities that have caused an increase in greenhouse gas levels

  • Burning of fossil fuels
  • Agricultural activities, especially rice farming
  • Deforestation
• Fossil fuels


  Fuels made up of the remains of organic material
• Fossil fuels are burned for energy, which produces electricity, fuels cars, and heats homes
• Burning fossil fuels


  Releases greenhouse gases such as carbon dioxide, nitrous oxides and methane
• Greenhouse gases concentrate within the atmosphere, contributing to the enhanced greenhouse effect
• The vast majority of CO2 comes from the burning of fossil fuels
• Agriculture


  A source of greenhouse gases due to farming activity
• Agricultural activities produce a lot of methane
• Methane


  A more effective greenhouse gas than CO2, better at trapping heat
• About 25% of global warming is thought to be caused by methane emissions, despite there being much less methane in the atmosphere than CO2
• Rice farming


  A large contributor to the levels of methane in the atmosphere due to the conditions in paddy fields
• Livestock


  Farm animals such as cows and sheep produce methane when they digest food
• One livestock animal on average produces 250-500 litres of methane a day
• Animals kept as livestock to meet the population's demand for meat and animal products contributes to huge methane emissions
• Agricultural fertilisers also produce nitrous oxides, which can be up to 300 times more effective in capturing heat than carbon dioxide
• Deforestation


  The process of cutting down trees
• Deforestation occurs to make space for agriculture, collect wood for other uses, or burn as fuel
• Trees take in CO2 from the atmosphere and store it inside them as carbon. Deforestation reduces the amount of CO2 being taken in and stored, resulting in higher levels in the atmosphere
• Burning of wood releases CO2 that was originally stored in the trees and puts it in the atmosphere
• Emissions of greenhouse gases due to human activities is thought to be a bigger influence on current global warming than natural causes of climate change
• Average global temperatures are projected to increase by as much as 4°C by the end of the century (projected between 1.8°-4°C) due to human activities
• The global temperatures are rising in a similar pattern to the levels of CO2 in the atmosphere