Data collection

• Historic data-

  • historic data collected in the past on atmospheric composition, temperature and weather patterns may be unreliable due to the lack of sophisticated equipment or a lack of data collection on a global scale
  • Temperature records collected in towns may show warming that is caused by an increase in the heat island effect as the town grows rather than as a result of a global temperature rise
• Proxy data-

  • involves making an estimate about one factor that cant be measured by using a related factor which can be measured or estimated
  • for example:
  • dendrochronology= the width of a tree ring shows the growth rate and may indicate the temperature at the time it was laid down, the age of tree rings can be estimated easily
  • some coral species produce large coral heads with annual growth rings which can be used to estimate past temperatures in the sea
• Ice core data-

  • over 40 ice cores have been drilled to gain information about the historical atmosphere, mainly in Antarctica and Greenland
  • annual accumulations of snow build up into ice layers, so deeper ice layers are older
  • data on ice up to 800,000 years old has been collected from the 3,200m core from Dome Concordia in Antarctica
  • air bubbles trapped in ice provide information on the atmosphere when the bubble became trapped, such as carbon dioxide concentration and the ratio of oxygen isotopes which gives information on the temperature when the gas was trapped
• Ice core data continued-

  • the layers are clearest in shallower ice
  • compaction caused by pressure can make deeper layers less distinct but radio-isotope analysis can also be used to estimate the age of the ice
  • layers of volcanic ash can be used to compare ice cores and identify layers of similar age
• Satellite data-

  • sensors carried by satellites are used to collect data on factors such as wind velocity, ocean currents, temperature, wave height, ice cover, ice thickness and vegetation cover
  • Low Earth Orbit (LEO) satellites in polar orbit at altitudes of about 800km collect detailed information of whole of the earths surface
  • each orbit lasts about 1.5 hours and successive orbits overfly different areas so the whole of the Earths surface can be surveyed over about 15 days
  • satellites in geostationary orbit provide less detailed information from a constant position of 36,000km above equator
• Monitoring ocean currents-

  • surface currents can be monitored using satellites or buoys and floats at the surface
  • deeper currents can also be monitored. Argo floats, can be programmed to sink to a particular depth for specific durations such as 10 days after which they surface, transmit the data then submerge for another 10 days
  • data are collected on factors such as temperature and salinity
  • the sequence of position plots show the direction and speed of the current
• Computer models-

  • the understanding of climate systems continues to grow and is helped by computer modelling which allows interconnections and their consequences to be estimated more accurately
  • a computer model can be tested by feeding in data for a particular year such as 1900 and seeing whether the model can predict the outcome for a later year, like 2000.
  • if the prediction was similar to the real outcome then the model can be trusted with caution
  • the model can be continually modified using more data collected by analysing differences between the predicted and real outcomes
• Feedback mechanisms and tipping points-

  • A change in one environmental factor may cause other factors to change. These may have an impact on the original change, either increasing or reducing it
  • Negative feedback mechanisms reduce the size of the original change
  • Positive feedback mechanisms increase the size of the original change
• Negative feedback mechanisms-

  • A negative feedback mechanisms takes place when an environmental change causes other changes which decrease the rate of the initial change or the level of its impact. This reduces its effect and helps to re-establish the original equilibrium
  • Increased low-level cloud: higher temperatures increase evaporation which leads to increased condensation and produces more clouds. Clouds have a higher albedo than most of the earth surface so more sunlight is reflected away and the amount of warming is reduced
• Positive feedback mechanisms-

  • Takes place when an environmental change causes other changes which increase the rate of the initial change or the level of its impact and thus increases the effect of the original change
  • This sequence of changes either increases temperatures directly or increases the concentrations of gases which will cause further temperature rise
• Soil decomposition-

  • the rate of decomposition of dead organic matter in soil is largely controlled by the temperature and in cooler areas organic matter can build up over time. If the temperature rises, the rate of decay may increase and aerobic decomposition by microorganisms will release more carbon dioxide, maybe for very long periods of time until the organic matter level has dropped to a new equilibrium level
• Melting permafrost-

  • Land areas in Arctic and Antarctic regions may have soil that is waterlogged but permanently frozen. This frozen soil includes dead organic matter that decomposed slowly under anaerobic conditions, releasing methane gas which was trapped by the permafrost. Warming can cause the frozen soil to defrost, releasing the methane gas which is a powerful greenhouse gas and causes further warming
• Ocean Acidification

  • Nearly half the carbon dioxide released into the atmosphere since the industrial revolution has dissolved in the oceans, producing carbonic acid and making the oceans more acidic. Ocean acidification reduces coral survival and therefore reduces carbon sequestration as less carbon dioxide is stored as calcium carbonate in coral
• Ice and snow melting-

  • Ice and snow have a high albedo so most of the incoming sunlight is reflected and not absorbed. If warming reduces the area of snow or ice then more sunlight may be absorbed causing further warming
• Release of methane hydrate

  • Dead organic matter in deep sea sediments has decomposed to produce methane gas. Under high pressures and low temperatures it from solid methane hydrate in the sediments. If deep seawater temperatures rise then methane hydrate may melt, releasing methane gas into the atmosphere. This would cause further temperature rise.
• Increased forest and peat fires

  • Many peat bogs have water logged soils where dead organic matter builds up to form peat. As these areas warm up and dry out, peat fires become more frequent so carbon dioxide is released and less carbon will be present in the remaining peat. Drier conditions would also cause forest fires to be more extensive and last longer, releasing more carbon dioxide into the atmosphere
• Increased water vapour

  • Warmer temperatures caused by carbon dioxide and other anthropogenic greenhouse gases increase the rate of evaporation. Although there will be an increase in the rate of precipitation warmer air can hold more water vapour. Water vapour is a powerful greenhouse gas and higher levels cause further warming
• Tipping points

  • Is the concept that human actions that cause climate change may cause changes in natural processes that themselves cause climate change to the extent that the original human actions are no longer needed for climate change to continue increasing. In this situation stopping the original human activity would not stop climate change.
  • If climate change is to be controlled, it is vital that this is done before tipping points are reached.
• Natural processes that will become unstoppable if temperatures rise too much-

  • Fasted soil decomposition
  • Release of carbon dioxide by increased forest and peat fires
  • Snow on land melting, caused by increasing temperatures reduces the earth's albedo so more sunlight is absorbed, rasing temperatures further and causing more snow to melt