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Learner Resource 1
Task 1: Climate change proxy analysis
Proxy Analysis
What does this indicate about Earth’s
past climates?
Tree rings
Tree growth is influenced by
and
rainfall i.e. the climatic conditions. Patterns are
analysed in tree-ring widths,
, and isotopic
composition that all give indications of the climate at
that time. In the UK and other temperate areas trees
will produce a new ring every
and these
provide a record of the climatic conditions. Some trees
can survive for thousands of years and so will
preserve valuable
of climate data that are
extracted from tree cores, similar cores are drilled into
ice.
Thick wide rings indicate periods of fertility
when precipitation is
and narrow
rings indicate
periods. Evidence
needs to be handled with care as tree rings
can be affected by other variables e.g. soil
and wind.
Ice cores
Ice has accumulated from snowfall over many
centuries and millennia having formed solid ice packs.
It is possible to drill through the ice to collect ice
which contain dust, air bubbles, or isotopes
of
that can be used to interpret the past
climate of that area.
CO2 was stable over the last millennium until
the early 19th century. However its
concentration is now nearly
higher
than it was before the industrial revolution.
CH4 has doubled since pre-industrial levels.
Parameter
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Climate Change
Image
1
© OCR 2017
Proxy Analysis
What does this indicate about Earth’s
past climates?
Marine and
lake
sediments
Billions of tonnes of sediments accumulate in the
world’s oceans, lakes, and
every year
and the deeper the sediment the older it is e.g. the
surface sediments reflect the climatic conditions in
the
day. Sediment cores are collected
and materials examined to determine historic
marine conditions e.g. ocean temperatures.
The ratio of oxygen
16 and 18
can be analysed to determine historic
ocean temperatures. Sediments rich in
heavy oxygen (oxygen-18) indicate
temperatures and match with
past ice ages.
Fossils
The remains of plants and
can get
buried in sediments and can be identified
thousands of years later. Species require specific
climatic conditions and hence scientists can deduce
what the climate what like at the time the remains
were deposited.
dating is used to
determine the age of the fossils.
A range of species have been identified
globally, including many along the UK’s
coastline, such as
Ammonites that indicate that temperatures
were once warmer in the past.
Parameter
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Image
2
© OCR 2017
Proxy Analysis
What does this indicate about Earth’s
past climates?
Fossil
pollen
Each species of plant produces pollen grains that
have a distinct and identifiable
. These
pollen grains are well preserved in the sediment
layers that form in the bottom of a lake or ocean.
By analysing the pollen grains in each layer, the
type of plants were growing at the time the
sediment was deposited can be determined.
Conclusions can then be made about the climate
at the time when those pollen grains were
deposited.
The amount of pollen deposited in a given
time period indicates the abundance of
vegetation, high concentrations indicating
periods. Species found in
savannah ecosystems have been
identified in the Amazon basin indicating
drier conditions in the past.
Corals
forms the skeleton of
corals and this is extracted from sea water. This
hard skeleton thus contains oxygen and the ratio
of isotopes of oxygen can be used to determine
the temperature of the water in which the coral
grew.
Higher concentrations of
isotopes indicate warmer ocean
temperatures and lighter cooler
temperatures- this has coincided with
records of temperatures in the Atlantic
ocean.
Parameter
Image
Word bank:
present
shape
warmer
pollution
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Climate Change
temperature
density
cold
rivers
drier
isotopes
archives
cores
calcium carbonate
heavy
Jurassic
3
animals
radiocarbon
40%
oxygen
spring
high
© OCR 2017
OCR Resources: the small print
OCR’s resources are provided to support the teaching of OCR qualifications, but in no way constitute an endorsed teaching method that is required by the Board, and the decision to use them lies with the individual teacher. Whilst every effort is
made to ensure the accuracy of the content, OCR cannot be held responsible for any errors or omissions within these resources. © OCR 2017 - This resource may be freely copied and distributed, as long as the OCR logo and this message remain
intact and OCR is acknowledged as the originator of this work.
OCR acknowledges the use of the following content: Tree rings - Laszlo/Shutterstock.com Ice core – Csiro/Simon Fraser/Briannica.com, Marine sediments – Science Photo Library/UIG/Briannica.com, Fossil – Vladimir Wrangel/Shutterstock.com,
Fossil pollen – Dee Breger/Photo Researchers/UIG/Britannica.com, Coral reef – Oleksandr Chub/Shutterstock.com
Please get in touch if you want to discuss the accessibility of resources we offer to support delivery of our qualifications: [email protected]
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© OCR 2017