How do we collect the data?

Who collects the data? IPCC – Intergovernmental Panel on Climate Change NASA Universities Meteorological Centres Environmental Groups

Is the Earth’s temperature rising? Data comes from so many different sources it can be difficult to tell! The UK meteorological society says no, NASA says yes….

What do we use to collect the data?... Thermometers Dendrochronology Coral Ice Cores Historical Records Frozen Isotopes Peat Bogs

Thermometers Many readings are possible Location is important Possible errors May not pick up slight changes Not representative of a large area

Corals Corals are animals Have a temperature range within which they can live Most live close to their upper range If it rises above this coral bleaching occurs; the coral becomes stressed Stressed coral expels the zooxanthellae it needs to provide it with food Coral cannot survive without zooxanthellae Corals take in isotopes; these can also give an indication of temperature

Ice Cores Ice Cores are a bit like annual rings on trees; every year a new layer is laid down and this makes it a useful record Very time consuming though! Can be used to tell us the composition of the air and give us an indication of what temperatures were like

Ice Cores Oxygen Isotopes are used to help determine temperature as well as air composition 18O evaporates less readily and condenses more readily than 16O During winter the heavier isotope precipitates more readily than the lighter one so less of it is found in the ice cores at the pole Therefore, each annual layer starts out 18O rich, then the level of 18O drops, before rising again at the end of the year The data collected this way can be compared with paleoclimatic data

Ice Cores The analysis using oxygen isotopes is not foolproof though – isotopes can diffuse as time proceeds We have been able to analyse data in ice cores from as far back as 300,000 years The ratio of deuterium to hydrogen can also be analysed to allow for a similar comparison As well as giving us an idea about temperatures (using oxygen isotopes) we are able to analyse the CO2 concentrations in the air

Ice Cores Volcanic ash can also be used to help us date an ice core This can be useful provided you know the exact date of an eruption Precipitation during ice ages was much more alkaline; again, this is a useful indication of the period the core was laid down in, but cannot give us an exact age

Historical Records The further back you go, the less reliable the data Modern methods much more precise Human errors Slight changes in temperature may not have been measured Useful as a comparison to more modern methods

Peat Bogs Can store vast amounts of carbon; up to ten times more than other ecosystems Important carbon sinks World’s carbon sinks store up to two trillion tonnes of CO2 (100 years of fossil fuel emissions!) Draining or burning peat bogs releases CO2 back into the atmosphere

Peat Bogs as indicators Atmospheric mercury can become trapped in peat bogs Cold climates produce a much greater level of trapped mercury and vice versa When dating, human activity can also contribute to mercury levels Scientists also look at levels of decay (plant and animal), the presence of particular leaf species and the presence of various species of amoebae – these can all give an indication of climate

Dendrochronology Tree-ring dating Size of xylem vessels Many large vessels laid down in summer Few small vessels laid down in winter Length of the summer and the temperature during summer period will affect the size of the xylem vessels

Dendrochronology Trees can produce more than one growth ring if conditions vary Comparison between many trees is needed Not exact; large rings doesn’t necessarily mean one thing Size of growth ring can be influenced by temperature, light intensity, CO2 concentration, rainfall or a combination of these