THE ISSUE OF GLOBAL
WARMING
6.1 The greenhouse effect
Assessment Statements
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6.1.1 Describe the role of greenhouse gases in
maintaining the mean global temperature.
6.1.2 Describe how human activities add to
greenhouse gases.
6.1.3 Discuss qualitatively the potential effects of
increased mean global temperature.
6.1.4 Discuss feedback mechanisms that would be
associated with an increase in mean global
temperature.
Assessment Statements
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6.1.5 Describe and evaluate pollution management
strategies to address the issue of global warming.
6.1.6 Outline the arguments surrounding global
warming
6.1.7 Evaluate contrasting human perceptions of the
issue of global warming.
6.1.1 Describe the role of greenhouse gases in
maintaining the mean global temperature.
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The chemical reactions that
support life-processes work at
optimal temperatures of
around 15oC. This
temperature is maintained by
certain greenhouse gases in
the atmosphere trapping
radiation that heats the
surface.
Short-wave ultraviolet light
from the sun is reflected from
the surface as infrared light.
Atmospheric gases are
transparent to the shorter
ultraviolet light, but either trap
or reflect back the longer
infrared light. This works just
like glass in a greenhouse.
6.1.2 Describe how human activities add to
greenhouse gases.
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Greenhouse gases consist of
water vapor (which makes up
95% of it), carbon dioxide,
methane, nitrous oxide, and
ozone.
Humans add up to 2.7
gigatons of carbon dioxide
every year. This is primarily
caused by deforestation and
the onset of global
industrialization and the
subsequent production of
pollution derived from fossil
fuels. There are natural
sources for CO2 as well, but
scientists assume most comes
from humans.
6.1.2 Describe how human activities add to
greenhouse gases.
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Main human activities
releasing greenhouse gases
are as follows:
Burning fossil fuels and
releasing carbon dioxide
Deforestation creating
carbon dioxide
Increased cattle ranching
leading to increased
methane levels
Rice farming in padi fields
leads to methane release
Fertilizers in agricultural
systems has led to higher
nitrous oxide concentrations.
6.1.3 Discuss qualitatively the potential effects of
increased mean global temperature.
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Increasing mean global
temperature will have the
following effects:
Retreat of polar ice caps and
glaciers
Increase in sea level causing
coastal flooding and relocation
Increased flooding
Change in biome distribution
and species composition
Severe water shortages and
possibly wars over supply
Agriculture may shift towards
poles
Increased diseases
6.1.3 Discuss qualitatively the potential effects of
increased mean global temperature.
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An increase in storm activity
such as more frequent and
intense hurricanes (more
atmospheric energy)
Up to 4 billion people
affected by water
shortages, including
reduced rainfall over the
USA, and much of Europe.
200 to 550 million more
people going hungry
60 million more Africans
exposed to malaria
Extinction of up to 40
percent of wildlife
6.1.4 Discuss feedback mechanisms that would be associated with
an increase in mean global temperature.
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Here are some of the positive
feedback loops:
Albedo – Amount of incoming
solar energy reflected back
into the atmosphere by the
Earth’s surface.
As the mean global
temperature increases, more
ice will melt each year. Less
ice will mean less albedo,
which will lead to an increase
in temperature.
Increased carbon dioxide
released from biomass
decomposition, especially in
forest regions leads to further
increase in temperature.
6.1.4 Discuss feedback mechanisms that would be associated with
an increase in mean global temperature.
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Rotting vegetation trapped
under permafrost releases
methane that is unable to
escape due to the ice covering
it. As the ice melts, it releases
the methane, which increases
greenhouse gases.
Increased forest cover in high
latitudes decreases albedo
and increases temperature.
Warming increases the
decomposition of gas hydrates
leading to a release of
methane and an increase in
temperature.
6.1.4 Discuss feedback mechanisms that would be associated with
an increase in mean global temperature.
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Large sea ice slows heat
loss from the relatively
warm ocean to the cold
atmosphere, as sea ice
masses melt and no longer
moderates the energy
balance, warming escalates.
Here are some of the
negative feedback loops:
Increased evaporation in
tropical latitudes due to
higher levels of
precipitation will lead to
increased snowfall on the
polar ice caps, reducing the
mean global temperature.
6.1.4 Discuss feedback mechanisms that would be associated with
an increase in mean global temperature.
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Deforestation leads to
increased aerosols and thus
reduced solar radiation at
the surface causing cooling.
Increase in carbon dioxide
in the atmosphere leads to
increased plant growth by
allowing increased levels of
photosynthesis (Carbon
dioxide fertilization effect).
Increased plant biomass
and productivity would
reduce atmospheric
concentrations of CO2.
Increased evaporation
increases cooling.
6.1.5 Describe and evaluate pollution management strategies to
address the issue of global warming.
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National and International
methods to prevent further
increases in mean global
temperature:
Controlling and reducing the
amount of atmospheric
pollution
Stopping forest clearance and
increasing forest cover
Developing alternative
renewable energy sources
Improving public transportation
Setting national limits on
carbon emissions
Developing carbon dioxide
capture methods
6.1.5 Describe and evaluate pollution management strategies to
address the issue of global warming.
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Carbon taxes (environmental
taxes for burning fossil fuels)
Carbon trading (allows
companies to trade permits for
producing emssions)
Carbon offset schemes
(Investing in projects that cut
emissions elsewhere)
One of the most successful
international agreements is the
Kyoto protocol for reducing
carbon dioxide emissions
The success of international
solutions to climate change
depend on the following:
6.1.5 Describe and evaluate pollution management strategies to
address the issue of global warming.
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The extent to which
governments wish to sign up to
the international agreement
Whether governments are
preventative (before it gets out
of hand) or reactive (respond
once it is obvious)
Ways individuals can reduce
greenhouse gas emissions:
Grow your own food or eat
locally produced or organic
food
Reduce your heating –
weather-proof your home
Use energy-efficient products
6.1.5 Describe and evaluate pollution management strategies to
address the issue of global warming.
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Unplug appliances and turn
off lights when not in use
Reduce the use of refrigerants
and air conditioning
Use a manual lawnmower
instead of electric or gas
Turn off taps and take showers
instead of baths
Walk, ride a bike, and use
public transportation more
often
Use biofuels
Eat lower down the food chain
(vegetables rather than meat)
Get involved in local political
action
6.1.6 Outline the arguments surrounding global warming
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Non-human factors affecting
global climate include:
Greenhouse gases produced
by natural sources (volcanoes,
sunspots, animals and peat
moss)
Volcanic ash and dust blocking
out solar radiation
Earth’s tilt and variation in
orbit causing regional and
seasonal temp changes
Reduced albedo due to
position and extent of ice
sheets
Changes in albedo due to
cloud cover
6.1.6 Outline the arguments surrounding global warming
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Ocean currents can lead to
warming or cooling
Natural fluctuations in
atmospheric circulation (El
Nino and La Nina)
Bush fires can release
carbon into the atmosphere
In addition, climate change
is a complex issue for a
number of reasons:
It is an issue on a huge scale
(all parts of the planet)
The interaction between the
parts of the planet are
many and varied
6.1.6 Outline the arguments surrounding global warming
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Includes natural and
anthropogenic forces
Not all the feedback
mechanisms are fully
understood
Many of the processes are
long term and the impacts of
changes may not have
occurred yet
It also includes a lot of
uncertainty which comes down
to two questions:
How much is the planet
warming?
Where will the impacts of
global warming be greatest?