1. How do we collect the data?

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

3. 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….

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

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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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