First 273 words of the document:
Biology Unit 4
Topic 5: On the wild side
18. Analyse and interpret different types of evidence
for global warming and its causes (including records
of carbon dioxide levels, temperature records, pollen
in peat bogs and dendrochronology) recognising
correlations and causal relationships.
Source of evidence Link to global warming
Temperature Long-term data sets allow changes in temperature to be analysed, e.g. the Central
records England Temperature series has records from 1659 to present
Tree rings Studying the size of tree rings is called dendrochronology. If the climate is
warmer and wetter then the rings are wider. We can look at tree ring widths over
3000 years into the past and can tell a lot about the climate from them.
Factors affecting growth include: light intensity, water availability and CO levels.
Pollen data Pollen grains are preserved in peat bogs. By sampling at different levels in the
peat we are sampling at different ages. Analysis of the pollen can tell us which
plants were growing and so what the climate was like when the peat was formed.
Ice cores Air trapped in ice when it was formed thousands of years ago can be analysed. A
tube of ice is taken out through the strata of the ice cap. Records of oxygen
isotopes (proportions of O¹ to O¹) reflect air temperature at the time. This gives
us information about temperatures and atmospheric CO levels in the past.
Ice cores give records for the longest time period (over 300 000 years).
Text Book: p.42 - 45