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Geography AS - World at Risk (Climate Change) (Coping with Climate Change,…
Geography AS - World at Risk (Climate Change)
Evidence of Climate Change
Climate is Constantly Changing
Medium-term climate change
Last glacial period
ended
around
18,000 years ago
.
Temperature rise was
not constant
after this.
Around 5000 years ago, temp was
1-2°C higher
than today.
Short-term climate change
Global warming
is the term used for the
rapidly increasing global temperature
over the
last century
.
Overall pattern over this time shows a general
increase
in
temperature
, but the pattern hasn't been
constant
.
Global temperature
rose steadily
from the
early 20th century
until the
1940s
, then
dropped
back down.
Scientists believe there would have been another
glacial period
but
global warming
prevented it.
Long-term climate change
The Earth's temperature has had huge changes.
Climate shifted from
cold glacial periods
(lasting around 100,000 years) and
warmer interglacial periods
(lasting around 10,00 years).
Currently in an
interglacial period now
Overview
Climate change
:
Any
significant
change in the
weather
of a region over a period of at least
several decades
.
Constantly changing
over
long
,
medium
and
short
time scales
Evidence for Long, Medium and Short-Term Climate Change
Medium-term change
Historical records
Records can
indirectly
indicate
different conditions
in the past.
Tree rings
New
tree rings
form each year as a tree grows. During good conditions, a tree ring will be thick.
Scientists can take
cores
and count rings to find a trees
age
and look at the ring's
thickness
to see what the climate was like
each year
.
Tree rings can reliably
show
and
date
climate conditions up to
10,000 years ago
.
Retreating glaciers
Scientists can tell the size and distance moved of a glacier by the position of
deposited rocks
, which can be
dated
to show when deposited.
Distance
of rocks from current glacier
indicates climate change
.
Short-term change
Weather records
Weather condition details have been consistently
collected since 1861
.
Can be used to show detailed
climate changes
over the time period collected.
Polar ice melt
Current research into
polar ice
behaviour shows
reduction
in amount of ice at both poles.
Changes in
extent of polar ice
shows changes in climatic factors affecting them.
Ecosystem changes
Changes in temperature affect availability of
food
and
shelter
.
Affects what species lives in an area.
Scientists can use
changes
in
species distribution
to indicate climate change.
Long-term change
Ice cores
Ice sheets
drilled to extract
ice cores
Ice sheets made up of ice
layers
One layer forms each year so the core bottom is very old.
Analysis of trapped gases from the ice formation tell what the temperature was each year.
Pollen analysis
Pollen
from plants is often
preserved
in
sediment
.
Can be
identified
and
dated
to show when it was
released
.
Scientists know present day
plant conditions
, therefore when they find preserved pollen from similar plants, it indicates
conditions
were
similar
when the preserved pollen was
produced
.
Sea level change
Sea level* is affected by things like the volume of water
stored as ice**.
Past sea levels are shown by
raised beaches
which can be
dated
.
Causes of Climate Change
Earth's Climate Changes Naturally without Human Influence
Variations in solar output
Output energy isn't constant.
Sunspots increase solar energy output.
Thought to increase and decrease in number in an 11 year cycle (with variations).
Meteor impacts
Meteor or asteroid impacts form large craters, throwing huge amounts of material into the atmosphere.
Can result in lots of sunlight being blocked for months or even years, changing the climate.
Variations in the Earth's orbit
Earth's orbit around the sun affects the way the Earth receives energy.
It's movements gradually change in three ways, in turn affecting global climate.
Stretch
:
Earth's orbit path changes from a almost perfect circle to an ellipse and back again about every 96,000 years.
Changes the distance from the sun, so energy amounts vary.
Tilt
:
Earth is tilted at an angle, called its axis.
Changes between 21.8° and 24.4° over a 41,000 year cycle.
Change in tilt changes amount of energy received, changing global climate.
When the tilt is greater (24.4°), areas receive more energy (the tropics) whilst other climate regions receive less (the temperate zones).
Wobble
:
Earth axis wobbles on a 22,000 year cycle.
Causes seasons to gradually change and swap.
Volcanic eruptions
Major volcanic eruptions eject large amounts of materials into the atmosphere.
Can result in lots of sunlight being blocked for months or even years, changing the climate.
Human Activity is Causing the Recent Changes in Climate
Recent rise in global temp and it's rate of increase unheard of in historical terms.
Scientific consensus that the rise is caused by human activity.
Climate is affected most by two human activities:
Destruction of natural CO2 sinks
:
CO2 sinks store CO2 keeping it out the atmosphere.
Biggest sinks are oceans.
Another big sink are plants.
CO2 released when trees are burnt by forest fires or to make way for agriculture.
Thought that a lot of GHG emissions from humans could be stored in CO2 sinks but now they won't be able to keep pace with increasing emissions, so more CO2 will go directly into the atmosphere.
Enhanced greenhouse gas emissions
:
GHGs include
carbon dioxide
,
methane
,
ozone
and
water vapour
.
Greenhouse effect
where GHGs absorb outgoing energy, less lost to space. Essential for keeping planet warm.
Too much GHGs in the atmosphere traps too much energy, causing global temp rise.
CO2 released into atmosphere when fossil fuels are burnt.
Impacts of Climate Change
Global Warming is causing...
Ice to Melt
Melting of ice on land means stored water is returning to oceans.
Increase in ocean water volume causes
eustatic
sea level change.
If all remaining ice sheets melted, global sea level would rise between 60-80 metres.
Increased global temp also means oceans get warmer and expand, further increasing the ocean water volume.
This could raise sea levels by 8-80cm each global temp increase of 1°C
Permafrost to Thaw
Permafrost is ground permanently frozen for two years or more.
Covers around 20% of the Earth's land surface.
Areas of permafrost are natural sinks of CO2, stored as organic material in the soil.
Thawing of permafrost releases some of this, contributing to global warming.
Thawing of permafrost can cause building and pipeline collapse.
May also bring economic benefits as it's easier to look for and extract natural resources in areas of unfrozen ground.
Other changes in Climate
Increase in frequency of extreme weather events
Change in the distribution of climatic regions
Affects ecology.
Affects agriculture.
Regional climate changes may benefit some human activities
Emissions Scenarios are Used to Predict Impacts of Global Warming
Scientific consensus human factors cause global warming.
Scientists try predicting how emissions will change in the future, to try predict changes in climate and the impacts.
A number of emission scenarios have been produced.
These can be put into global climate models to see how the climate will change in each scenario.
These can be used to show how different climate changes can cause different impacts.
Combined Impacts May Lead to a Tipping Point
Slight rise in temperature could cause catastrophic and irreversible changes to the environment.
May happen due to positive feedback loops where a change in climate speeds up by impacts it's already caused.
Combined effect of positive feedback on existing impacts may lead to a tipping point.
Coping with Climate Change
Strategies Have Limitations and Side Effects
Limitation
- Strategies might have limitations that reduce their effectiveness.
Side effect
- Some strategies might have side effects on other things.
Agreeing on How to Cope with Climate Change is Complex
Key players:
Governments
- develop strategies on an international, national and local scale.
Businesses
- Responsible for contributing to climate change, or can help slow it down. May lobby governments to reduce restrictions or may help by investing in new technologies to combat climate change.
Non-governmental organisations
- Can have many roles and views depending on what they're set up to do and who their members are.
Communities
and
Individuals
- Strategies developed on a larger scale are carried out at a local level.
Strategies to cope with climate change need to be developed, managed and carried out.
Can be done at different levels by various groups.
There are Different Strategies for Coping with Climate Change
Mitigation strategies
- Involves taking action to reduce how much climate change occurs.
Examples:
Carbon tax.
Changing the energy mix.
Modified agricultural practises.
Emission-cutting technologies.
Energy conservation.
Waste strategies
Tree planting.
Carbon offsetting.
Adaptation strategies
- Involves taking action to reduce the impacts that the changes are having.
Examples:
Lifestyle adaptations.
Improved risk assessment.
Flood adaptations.
Water resource management.
Community awareness.
Individuals Can 'Act Local, Think Global'
Individuals can make small changes that will help the global problem.
Some think if everyone took steps to decrease their carbon footprint, it'd make a big difference. Others disagree.
Likely that emission changes are incremental rather than gradual as large-scale initiatives and changes in attitudes cause sudden changes.