Evidence for Climate Change
5.12 Understand the different types of evidence for climate change and its causes (including records of
carbon dioxide levels, temperature records, pollen in peat bogs and dendrochronology), recognising
correlations and causal relationships.
Climate Change
• Climate change describes the significant change in the weather of a region, usually over a period of
several decades.
• Global warming is a type of climate change – it’s the rapid increase in global temperature seen over
the last century.
Temperature Records
• Temperature records have been measured around the world, using thermometers, for 2-3 centuries at
most.
• They provide a reliable but short-term record of global temperature change.
• However old data may have been collected with equipment that isn’t as accurate as those used today.
Pollen in Peat Bogs
• Plant and insect remains in peat bogs can provide evidence for climate change since the last Ice Age
(12,000 years ago).
• Peat is an accumulation of partially decayed organic matter,
• When plant material dies it normally decays. However in anaerobic and acidic conditions, the rate of
decay is slowed or stopped.
• Pollen grains are well preserved in peat.
• Pollen grains are very resistant to decay as they have a tough outer layer.
• Different plant species produce a distinctive type of pollen, so we can identify which plants were
present.
• Peat forms in layers, so deeper layers contain older peat – the age of a particular peat layer can be
established using carbon-14 dating.
• By considering the ecological conditions (e.g. temperature) in which a plant species flourishes the
most, we can infer what the conditions were like at that time.
• E.g. If pollen is found from a species which favours warmer conditions, we can infer that the climate
was warmer.
Dendrochronology
• The division of cells underneath the bark of a tree produces a new layer of xylem vessels each year.
• The vessels grow the most in spring, followed by summer. There is very little growth in
autumn/winter.
• This creates a pattern of rings across the trunk.
• Cores can be taken through the tree trunk for examination.
• In years where ecological conditions are more suitable for tree growth (i.e. higher temperatures), the
rings are wider.
• These studies provide evidence for climate change for hundreds to even thousands of years.
16
5.12 Understand the different types of evidence for climate change and its causes (including records of
carbon dioxide levels, temperature records, pollen in peat bogs and dendrochronology), recognising
correlations and causal relationships.
Climate Change
• Climate change describes the significant change in the weather of a region, usually over a period of
several decades.
• Global warming is a type of climate change – it’s the rapid increase in global temperature seen over
the last century.
Temperature Records
• Temperature records have been measured around the world, using thermometers, for 2-3 centuries at
most.
• They provide a reliable but short-term record of global temperature change.
• However old data may have been collected with equipment that isn’t as accurate as those used today.
Pollen in Peat Bogs
• Plant and insect remains in peat bogs can provide evidence for climate change since the last Ice Age
(12,000 years ago).
• Peat is an accumulation of partially decayed organic matter,
• When plant material dies it normally decays. However in anaerobic and acidic conditions, the rate of
decay is slowed or stopped.
• Pollen grains are well preserved in peat.
• Pollen grains are very resistant to decay as they have a tough outer layer.
• Different plant species produce a distinctive type of pollen, so we can identify which plants were
present.
• Peat forms in layers, so deeper layers contain older peat – the age of a particular peat layer can be
established using carbon-14 dating.
• By considering the ecological conditions (e.g. temperature) in which a plant species flourishes the
most, we can infer what the conditions were like at that time.
• E.g. If pollen is found from a species which favours warmer conditions, we can infer that the climate
was warmer.
Dendrochronology
• The division of cells underneath the bark of a tree produces a new layer of xylem vessels each year.
• The vessels grow the most in spring, followed by summer. There is very little growth in
autumn/winter.
• This creates a pattern of rings across the trunk.
• Cores can be taken through the tree trunk for examination.
• In years where ecological conditions are more suitable for tree growth (i.e. higher temperatures), the
rings are wider.
• These studies provide evidence for climate change for hundreds to even thousands of years.
16
