Pp 122 - 130
Assessment Statements
 5.2.1 Draw and label a diagram of the carbon cycle to show
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the processes involved.
5.2.2 Analyse the changes in concentration of atmospheric
carbon dioxide using historical records.
5.2.3 Explain the relationship between rises in
concentrations of atmospheric carbon dioxide, methane and
oxides of nitrogen and the enhanced greenhouse effect.
5.2.4 Outline the precautionary principle.
5.2.5 Evaluate the precautionary principle as a justification
for strong action in response to the threats posed by the
enhanced greenhouse effect.
5.2.6 Outline the consequences of a global temperature rise
on arctic ecosystems.
Draw and label a diagram of the carbon
cycle to show the processes involved.
 You must be able to draw
and label the complete
carbon cycle.
 The details of the carbon
cycle should include the
interaction of living
organisms and the
biosphere through the
processes of
photosynthesis, cell
respiration, fossilization
and combustion.
Roles of living organisms in the carbon cycle
 plants fix carbon dioxide during photosynthesis
 producing carbon compounds such as sugars
 carbon compounds in plants are eaten by
primary consumers (herbivores)
 carbon compounds in primary consumers are
eaten by secondary consumers & passed along
the food chain
 carbon compounds are digested & absorbed by
consumers
 carbon dioxide is released by cell respiration in
plants & animals
 plants & animals die and are decomposed by
saprotrophic bacteria & fungi
 carbon dioxide released by cell respiration in
bacteria & fungi (decomposers)
 enzymes are released to digest carbon
compounds in organic matter
 forest fires (combustion) releases carbon
dioxide
 humans burn fossil fuels adding carbon dioxide
to the atmosphere
Changes in atmospheric carbon dioxide
concentration over time
 increase in machinery & industrialization
has caused rise in levels of atmospheric
carbon dioxide concentrations since the
1880’s.
 human activities such as the burning of
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fossil fuels & transportation have all
contributed to the increase.
scientists estimate the levels have
increased by over 25% as compared to the
levels before industrialization.
scientists take measurements by looking
at the concentration of carbon dioxide in
bubbles of air trapped in Antarctic ice at
different dates.
this data shows that before the 1880’s the
carbon dioxide concentrations remained
fairly steady at about 270 ppm for about
2000 years.
concentration begins rising after 1880 and
is now more than 100 ppm higher than in
1880.
Global trend in Greenhouse Gases
Relationship between the rise in the concentration of
atmospheric CO2 & the enhanced greenhouse effect
 CO2 is a greenhouse gas
 increases in CO2 enhance the greenhouse effect
 greenhouse effect is a natural phenomenon but
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not its increase
Earth receives short wave radiation from the sun
These waves reflected from Earth as longer wave
radiation, infra red or heat
CO2 (greenhouse gases) absorb longer wave
radiation, infra red & heat
global warming happened during same period
as the rise in CO2
CO2 concentration correlated positively with
global temperature
this causal link between CO2 concentration &
global temperature is accepted by most
scientists
However, there is no proof that man-made
increases in CO2 have caused global warming
Relationship between rises in concentrations of
atmospheric carbon dioxide, methane and oxides
of nitrogen and the enhanced greenhouse effect.
 water vapour, carbon dioxide,
methane & oxides of nitrogen
are greenhouse gases which
occur naturally in low
concentration in the atmosphere
 human activity has increased
the normal level of these gases
in the atmosphere in recent
years
 incoming shorter wave radiation
from the Sun is re-radiated as
longer wave radiation
 mainly in the form of heat which
is captured by the greenhouse
gases
 this trapping of radiations
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increases the atmospheric
temperature
at a higher rate than normal
creating a positive imbalance in
global temperature
which threatens ecosystems,
climatic patterns & ocean
patterns
Earth’s history had many
fluctuations in greenhouse gases
levels & global temperature
some scientists are skeptical
about enhanced greenhouse
effect
The enhanced greenhouse effect
Causes and consequences of the enhanced
greenhouse effect
 burning of fossil fuels such coal,
 global warming causes melting
oil & gas releases carbon dioxide
 deforestation & loss of
ecosystems reduces uptake
carbon dioxide by plants
 methane is emitted from cattle,
melting permafrost &
decomposing waste at dump
sites
 accumulation of greenhouse
gases cause heating of the
atmosphere leading to global
warming
of ice caps, glaciers, permafrost,
sea level rise, flooding &
droughts
 global warming also causes
changes in ocean currents,
produce more powerful
hurricanes & extreme weather
conditions
 there is also changes in species
distributions, migration
patterns, increased
decomposition rates, increases
in pest & pathogen species, loss
of ice habitats
The precautionary principle
 those proposing something must prove that
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it causes no harm before they start to do it
objectors do not have to prove that there will
be harm
activities that threaten the environment are
banned
trials (tests) must be done first before
changes are made
precautionary principle is applied when
possible consequences are severe
precautionary principle should be used in
the case of global warming
action should be taken to reduce CO2
emissions before proved it is the cause of
global warming
where there are threats of serious or
irreversible environmental damage, lack of
full scientific certainty should not be used as
a reason for postponing measures to prevent
environmental degradation
Precautionary principle as a justification for strong
action in response to the threats posed by the
enhanced greenhouse effect
 Supporters of the precautionary
principle advocate for action now
to reduce greenhouse gases before
it is too late. Anyone producing
greenhouse gases should be
required to prove that those gases
will not have harmful effects.
 Those on the opposite side of this
issue such as farmers,
manufacturers and transportation
providers, argue that if there is no
proof that greenhouse gases are the
cause then they should not have to
invest money in new technologies
to reduce such gases.
 The global consequence is that unless all
countries take precautionary measures,
which can be more expensive than the
traditional methods, the polluting
competitors will offer products at a
reduced price and drive the ecologically
conscious companies out of business.
 A global effort to support the ecologically
friendly companies could drive their less
ecologically friendly competitors out of
business.
 Most scientists believe that the old saying
“an ounce of prevention is worth a pound
of cure” is relevant here. A more
sustainable future is something worth
investing in.
 There are also many ethical issues at play
here and the future generations to
consider. The time for more sustainable
development is here. Humans are not
only impacting each other but all
organisms within the biosphere.
Consequences of a global temperature rise
on arctic ecosystems
 Global warming seems to have the
largest & most obvious effects right
now on the arctic ecosystems.
 The Arctic includes the areas of
North America, Greenland, Iceland,
Norway and Russia which are north
of the Arctic Circle.
 It also includes Arctic Ocean which is
covered by a huge mass of ice
surrounding the North Pole.
 Over the century there have been
many changes in the ecosystems in
this area noted by scientists and the
people who live there.
 changes in the arctic ecosystems include
the following:
 increased amounts of ice melting each year.
 melting of glaciers & breaking of polar ice
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sheets into icebergs that will eventually melt the Arctic ice cap may disappear altogether.
permafrost will begin melting during the
summer which means the rate of
decomposition will increase resulting in the
release of more carbon dioxide.
species will have to move north which will alter
food chains and disrupt animals in the higher
trophic levels.
many marine species could face extinction due
to their sensitivity to temperature changes in
the ocean.
Polar bears & other ice dwelling organisms will
lose their habitat where they feed and breed.
warmer temperatures will increase the threat
of pests and disease such as malaria.
the rise in sea levels will flood low-lying areas.
extreme weather events (storms) will become
more frequent.