Download L10 Climate Change Long and Short Term Evidence

Learning Objectives
• Know how scientists have got
data from the past to create
graphs of climate change
• Understand that we can look at
Climate change as both long and
short term events
• Will be able to evaluate how
reliable past records are to use
Is climate change natural or
human induced?
•The problem with global warming is
that everyone agrees that it is
happening, but there is fierce debate
about how and why?
•Many Scientists believe that climate
change is a result of the enhanced
greenhouse effect
The combined effect of increase
in greenhouse gases!
So what are the
greenhouse gases?
The 4 main greenhouse gases are:
•CO2
•Methane
•CFCs
•Nitrous Oxide
Climate Change is not a new thing!
•The worlds climate has been changing over the
last 18 000 years, sometimes getting hotter and
sometimes colder as you can see from the graph
below. We will look next lesson at some reasons
why scientists think Global warming is a natural
event!
Where do we get the long term evidence
for climate change from?
1. Ice Cores
• 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.
1. Ice Cores
• 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
we are going through now!
1. Ice Cores
• From the ice cores we can also detect oxygen
isotopes. Combined with the CO2 isotopes the 2
link in well to explain sea level changes.
• When there was low levels of CO2 recorded sea
levels were lower (think why???)
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•
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?
• 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+
1. Tree rings- How accurate
and reliable are these
sources of data?
• Good reliability – However, tree
records only give localised records!
2. Paintings and written accounts
6b. Paintings are a good line of
evidence
Bruegel Painting 1565
London Frost Fair 1789
Dickensian Winters
• 6c. The written
word is also good
evidence
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
3. Retreating glaciers
• Glaciers change in response to
climate change.
• We can look at old
photos/maps/paintings to
measure direct differences in
glacial positions
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?
Short Term
• Link between CO2 &
temperature
• Is the Carbon
Anthropogenic
(human) or Natural?
• Most scientists
agree Anthropogenic
Short Term
• 3 possible
effects of
climate change!
To end…
• Give 2 examples of research
methods that show long term
historical climate change?
• How reliable are these?
• Give 2 ways of measuring medium
term climate change?
• How reliable are these?
• What about short term?