Transcript Long term climate change - geography departmant of lwc

Long term climate change
Climatic periods since the
Pleistocene Ice Age in the UK
Pre Boreal 10,300 BP
Change from Tundra to continental.
Original cold and wet but becoming
warmer and drier
Boreal 9,000 BP
Becoming warmer and drier: a typical
continental climate
Atlantic 7,500 BP
Climatic optimum warm and with
slightly higher rainfall
Sub Boreal 5,000 BP
Becoming colder in winter, rainfall
slowly increasing. Some ice advance
Sub Atlantic, 2,500 BP
Little climatic optimum 1300 – 1100AD
Temp fluctuations
Warmest since Atlantic, wine in UK
Vikings
Thames freezes. Famine
Temps. Slowly increasing
Little Ice Age 1550 – 1859 AD
Today Global warming
Evidence for climate change
Pollen analysis;
Dendrochronology;
Ice core analysis;
Radiocarbon dating;
Coleoptera;
Tephra chronology
Historical records.
Pollen analysis
The pollen analysis, study of vegetation
history using the microfossils (pollen grain
and spores of size 15-50 um)
The pollen is preserved in peat bogs( an
anaerobic environment) and the type of
vegetation can give a clue to the prevailing
climate.
But the wind can blow pollen a long
distance.
Dendrochronology
..is the dating of past events (climatic changes)
through study of tree ring growth;
wide rings of certain species of trees were
produced during warm wet years and, inversely,
narrow rings during cold dry seasons.
Bristlecone Pine
But trees tend to respond more to changes in
moisture than temperature.
Ice Core analysis
The concentration of CO2 trapped within
the ice can be measured and the
atmospheric temperature can be inferred.
The lower the CO2, the lower the global
temperature.
This has been done extensively in
Greenland and Antarctica
Radio carbon dating
Radio carbon dating determines the age of
ancient objects by means of measuring the
amount of carbon-14 there is left in an object
All living things take in carbon 12 and 14. The
later decays at a known rate so when a plant
dies it starts to lose carbon 14 and so the ratio of
12 to 14 changes.
Carbon 14 has a half life of 5,730 years and so
there is a limit as to how far back this is
accurate. At the moment this is about 50,000
years
Coleoptera
Certain coleoptera beetles like specific
climates and so a knowledge of this will
help if the remains of the beetles are found
Tephra chronology
This is used to date volcanic eruptions
The chemicals radioactive minerals are
dated using their half life
Recent global warming
The diagram shows temperature rises
since 1860
Tmperatures have been higher in the past
but the change now is rapid and so natural
systems will find it hard to change
Why is global warming occurring?
This is due to greenhouse gases which
are vital for the planet. Without them out
temperature would be 30C lower.
But recently the amount of emissions have
increased.
Particularly CO2 ,
A doubling of CO2 would cause a 7 C rise
in temperatures in the higher latitides
Effects of global warming
Rising sea levels this would cause huge
problems for low lying countries such as
the Netherlands, many Pacific and Indian
Ocean islands, as well as coastal cities
Climate change world wide. This would
lead to numerous global disasters.
The number of floods, droughts and
storms would increase
Solutions?
The Kyoto Protocol was brought into effect in
February 2005
But the USA has not signed up
If a country went over its carbon limit then it
could buy Carbon credits from less polluting
countries. If this does not work then fines could
introduced, the country would be encouraged to
look for alternative.
Climate change levy