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Long term evidence for climate change
1. Ice Cores
Explanation...
• Best evidence for climate change comes
from Greenland and Antarctic ice cores
• Ice cores are a frozen record of past
climates... Like a time capsule
• Within these layers the ice contains air
bubbles which contain carbon dioxide
and oxygen isotopes.
• From looking at the graph you can see clearly the periods of low
concentrations of CO2 occur during glacial periods
• High concentrations of CO2 link with warmer periods of time- like the
Holocene interglacial we are going through now
• Low CO2 = Low sea level
Long Term
1. Ice Cores
Long Term
• From looking at the graph below you can see
clearly the periods of low concentrations of
CO2 occur during glacial periods
• High concentrations of CO2 link with warmer
periods of time- like the Holocene interglacial
(in between glacial times) we are going through
now.
• Low CO2 = Low sea level
Long Term
1. Ice Cores- How accurate
and reliable are these
sources of data?
• The sequences of sea level change
links very closely with oxygen and
CO2 isotope levels suggesting that
this is a very reliable source!
2. Pollen Analysis
Long Term
• Pollen is produced by all
plants and was extracted
from sediment cores in
peat bogs and lake beds.
• Pollen grains are
preserved in waterlogged
sediments.
• By analysing Pollen we can
see how ecosystems have
changed in response to
climate change.
2. Pollen Analysis- How
accurate and reliable are
these sources of data?
Long Term
• Not as reliable - as accurate pollen
reconstructions rely on good
preservation of pollen. Long pollen
sequences are rare, and vegetation
change may lag behind “climate
change”.
Where do we get the medium term
evidence for climate change from?
1. Tree Rings (Dendrochronology)
• Many trees are
sensitive to changes
in temp, sunlight and
precipitation
• In warm years trees
have wide rings &
vice versa
• Record can go back
10,000years+
Medium Term
1. Tree rings- How accurate
and reliable are these
sources of data?
• Good reliability – However, tree
records only give localised records.
Medium Term
2. Paintings and written accounts
Bruegel Painting 1565
London Frost Fair 1789
Medium Term
Dickensian Winters
• Written word is
also good
evidence; they
provide
description of
climatic
conditions
Medium Term
2. Historical records- How
accurate and reliable are
these sources of data?
• Unreliable – These sources did not
set out to record climate, and must
be used with care. They are usually
local, and difficult to generalise.
3. Glacier Retreat
Medium Term
3. Retreating glaciers
Medium Term
• Glaciers change in response to
climate change.
• We can look at old
photos/maps/paintings to
measure direct differences in
glacial positions
Medium Term
3. Retreating Glaciers- How
accurate and reliable are
these sources of data?
• Reliable – Good records stretch back
to around 1880, before this the
record is patchy.
Where do we get the short term evidence
for climate change from?
• The last 128yrs of data suggest the Earth is 0.7 – 0.8
oC warmer
• 11 of the world’s hottest 12 years occurred in the decade
1995-2006
• Global warming or natural change?
Short Term
• Link between CO2 &
temperature
• Is the increase in
CO2 anthropogenic
(human) or natural
changes?
...Most scientists
agree anthropogenic
Short Term
• 3 possible
effects of
climate change!