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Global Warming
The recent gradual warming of the
Earth’s atmosphere largely as a result
of human activity.
Contents
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Evidence
– Pollen analysis
– Dendrochronology
– Ice-core analysis
– Sea-floor analysis
– Radiocarbon dating
– Coleoptera
– Changing sea levels
– Glacial deposits
– Historical records
– Recent evidence for global warming
Possible causes of climate change
– Enhanced greenhouse effect
Effects of global warming
– Rising sea levels
– Climatic change
– Extreme events
Case studies
– The Amazon basin (equatorial)
– The African savanna (tropical wet/dry)
– Bangladesh (Monsoon)
Effects on the British Isles
– Coastal regions
– Agriculture
– Flora, fauna and landscape
– Soils
– Water resources
– Energy use
Responses to global warming
– International responses
– National responses: the UK
– L local responses
EVIDENCE
Evidence
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Pollen analysis
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Dendrochronology
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Core samples from ocean floor reveal shifts in animal an plant populations which indicate climatic change
Radiocarbon dating
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Drilling cores from areas such as Antarctica and Greenland. Carbon dioxide trapped inside =climatic indicator levels ten to be
lower during cooler periods and higher in warmer
Sea-floor analysis
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Tree ring analysis each year a tree grows a ring on its trunk
A wide band indicates a warm wet year a narrower one indicates a cooler and drier year
Limitation is investigations have shown that trees respond more to levels of moisture than temperature
Also few trees are older than 4,000 years
Ice-core analysis
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Pollen resist decay when they fall into peat bogs
Different species of plant prefer different climatic conditions
Pollen is a good way of finding out climatic conditions as only mature plants produce pollen therefore the conditions were good
enough for them to grow
A limitation is that pollen can be moved by animals or wind.
Carbon is taken in by plants during photosynthesis
Carbon-14 decays at known rate carbon 12 does not decay
Therefore comparison of the levels of the two isotopes present in plant remains indicate the age at which the plant died.
Type of vegetation present at particular times indicates climate periods
Method can accurately date organic matter up to 50,000 years old.
Coleoptera
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Analysis Cleoptera beetles tend to be found under different climatic conditions
Present day knowledge of present climatic range of different species and age of sediments allows past climatic conditions to be
determined.
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Changing sea levels
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Glacial deposits
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Historical records
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Recent evidence for global warming
– Rising average temperatures
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Rias and fjords and fjords indicates rising (eustatic) sea levels flooding glacial and river valleys.
Show records of ice advance during colder periods and retreat during warmer times.
Cave paintings, depth of grave digging in Greenland diaries, documentary evidence of events
Possible causes
Possible causes of climate change
• Theories:
– Variations in solar activity(sunspot activity)
– Changes in the Earth’s orbit and axial tilt (which affect the amount
of solar radiation reaching the surface)
– Meteorite impact
– Volcanic activity (increasing dust in the atmosphere)
– Plate movement (redistribution of land masses)
– Changes in oceanic circulation
– Changes in atmospheric composition, particularly the build-up of
carbon dioxide and other greenhouse gases (the enhanced
greenhouse effect)
• Enhanced greenhouse effect
Effects
Effects of global warming
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Rising sea level
– Sea level rise in 20st century has been 1.5cm
– But in 21st could rise between 5-10cm in a decade
– Sufficient enough to cause serious flooding in coastal areas and increased erosion
– Low lying countries such as Bangladesh and Netherlands and Bangladesh, and many pacific and Indian Ocean islands,
rising sea levels will have catastrophic consequences.
– Cost of flood defences
– British estuaries may need defences similar to the Thames Barrier
Climatic change
– Many places will experience warmer summers
– Continental areas could see reduced rainfall
– They could end up producing desert like conditions in places previously good for agriculture, such as Spain
– Some climatologist believe that if global warming leads to changes in the pattern of ocean currents UK could have a
much colder climate
– Changes in vegetation, wildlife and agriculture.
– Populations would diminish
– Mass migrations as people search for areas to grow crops
Extreme events
– Heat waves, floods, droughts and storms will all last longer and show increasing intensity
– Higher temperatures = increased evaporation over oceans = greater global precipitation
Effects on the British Isles
Effects on the British Isles
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Coastal regions
Agriculture
Flora, fauna and landscape
Soils
Water resources
Energy use
Responses
Responses to global warming
• International responses
– Carbon credits
– Post Kyoto
• National responses: the UK
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Domestic front
Carbon Trust
Scotland woodland creation schemes
Climate change and Sustainable Energy Act
Climate change bill
5 year carbon targets
• Local responses
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Insulating
Recycling
Using energy wisely
Using public transport
Arguments for global warming
• Climate change has happened before but now
humans are the dominant factor affecting it.
• Can talk about evidence Dendrochronology...
• Hockey stick
Arguments against global warming
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Vested interest of scientists. It is argued that scientists exaggerate the effects of
global warming because they receive funds from environmental companies.
Unreliability of computer climate models. It is argued that these models are not
able to predict tomorrow’s weather. So how can they predict long-term climate
change?
There are other factors involved in global warming. It is argued that human
activities are not the only cause of global warming.
People in fossil fuel industries will lose their jobs.
Case studies
The Amazon Basin (equatorial)
Location: South America
Lies within equatorial climate zone and
covers an area of some 8,235,430 km2,
mainly in Brazil
Predicted impacts of climate change on this
region: An increase in temperature of 2-3ºC
by 2050
A decrease in precipitation during the dry
season last up to 4 months
More intense rainfall will be experienced
during the wet season.
Sea levels are currently rising by some 5 mm
per year along the delta Amazon
Up to 40% of plant species may no longer be
viable in the Amazon rainforest by 2080 if
predicted climate changes occur
As the dry season lengthens trees will have
more time to dry out so there is likely to be
increased incidence of spontaneous
Problems of hydraulic cycle
The African savanna (tropical wet/dry)
Location: North Africa
tropical wet/dry savanna climate is
experienced over a huge area of
Western African surrounding the
rainforests to the north and south of
the equator.
Savanna lands likely to experience an
increase in temperature of some 1.5
degrees by 2050 . Surrounding sea
temperatures are not expected to rise
to the same extent (0.6-0.8 degrees),
resulting in greater temperature
differential between land and sea.
Precipitation expected to increase by
15% within the savanna lands closer
to the equator but might decrease by
10% in areas towards the northern
and southern fringes of the climate
zone, for example in the Horn of
Africa. This is likely to be due partly to
the Sahara heating up more than the
Atlantic Ocean, causing more
moisture to be drawn in from the
ocean during the wet season
Bangladesh (monsoon)
Location: Bangladesh country in
South Asia
Population is over 150 million in 2008
Most densely populated countries in
the world
Poorest nations it is the most illprepared . To face challenges
Likely to be seriously effected by
global warming.
Predicted effects include:
Increase in average temperatures of
1.5-2.0 digress calicoes by 2050
Increase of 10-15% in annul
precipitation by 2050.
20% increase in river discharge
Because of glacial melt from
Himalayas