5.2 - The Greenhouse Effect
5.2 - The Greenhouse Effect
5.2 - The Greenhouse Effect
NOTES
BIOLOGY
TUTTEE ACADEMY
Chemistry & Biology Specialist
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5.2 - The Greenhouse Effect
5.2.1 - Draw and label a diagram of the carbon cycle to show the processes involved
Carbon can be found in four 'pools,' and moves between these four pools through a variety
of biological, geochemical or industrial processes.
Biosphere
Oceans
Atmosphere
Sediments
Photosynthesis - By terrestrial plants and algae in which atmospheric (and dissolved) carbon
dioxide is removed and fixed as organic compounds such as carbohydrate, lipid and protein
Respiration - This is done by all organisms in which they metabolise organic molecules,
releasing carbon dioxide
Feeding - The carbon of organic molecules is moved from one link in the food chain to
another
Fossilisation - Carbon, as organic molecules, becomes trapped in sediment as coal, gas and
oil
Combustion - This happens during the burning of fossil fuels and biomass
5.2.2 - Analyse the changes in concentration of atmospheric carbon dioxide using
historical records
The trends in atmospheric gases are studied as indicators of potential climate change. Those
studied include carbon dioxide, methane and oxides of nitrogen, the greenhouse gases. In
Mauna Loa, atmospheric carbon dioxide has been studied since 1958. There are many other
labs around the world these days, adding to the database of carbon dioxide levels.
Carbon dioxide is released unevenly around the world, which is in part due to the
distribution of vegetation. Therefore, collective data allows us to see what has happened
after there is mixing of the atmospheric carbon dioxide. The basic trend is an increase in
atmospheric carbon dioxide levels. Longer term estimates of global CO 2 levels have been
determined by a variety of sources including gases trapped in ancient ice cores.
Bubbles of atmospheric gases are trapped within the ice formed thousands of years ago.
Taking cores of the ice and then analysing the gases allows CO 2 levels to be determined. The
temperature can be determined from the ratio of O 16 to O18. From this, in has been
concluded that there is a clear correlation between atmospheric CO 2 and temperature. Of
course, correlation does not mean causation.
5.2.3 - Explain the relationship between rises in concentrations of atmospheric carbon
dioxide, methane and oxides of nitrogen and the enhanced greenhouse effect
Gas molecules in our atmosphere with three or more atoms can capture outgoing infrared
energy and warm the planet, and are called greenhouse gases. These include H 2O, O3, CO2
and CH4. Chlorofluorocarbons, CFCs, also have a disproportionately large effect.
The increase greenhouse gases means that more infrared light will be absorbed, scattered
and retained as heat. The average global temperature will rise. The enhanced greenhouse
effect is predicted to cause global climate changes, often referred to as global warming,
although local effects may vary greatly.
5.2.4 - Outline the precautionary principle
The precautionary principle holds that, if the effects of a human-induced change would be
very large, perhaps catastrophic, those responsible for the change must prove that it will not
do harm before proceeding. This is the reverse of the normal situation, where those who are
concerned about the change would have to prove that it will do harm in order to prevent
such changes going ahead.
This means that, if it cannot be proven that no harm will come of the action, it must not go
ahead.
5.2.5 - Evaluate the precautionary principle as a justification for strong action in response
to the threats posed by the enhanced greenhouse effect
Burden of Proof
Those making the claims must prove, with sufficient evidence, that it is true before others
change their understanding or behaviour. Therefore, the environmentalists need to provide
conclusive evidence that the actions of the polluters are causing harm to the environment.
Precautionary Principle
Those who are accused of being responsible for causing the enhanced greenhouse effect are
required to demonstrate that their actions do not cause harm. This would fall upon
governments, industries, communities and individuals to show this.
Decomposition of Detritus
The significant decay by microorganisms of the accumulated detritus (dead organic matter),
once released from its permafrost state, leads to huge releases into the atmosphere of
methane and carbon dioxide, which was previously locked away in the dead organic matter.
This contributes further to global warming.
Range of Habitats
More areas with soil rich in humus are formed. As a result, more plant life, including
conifers, appear and grow. As these plant absorb radiant heat energy and contribute further
to global warming, since they replace ice, snow and frozen tundra. A wider range of flora is
appearing. More insect-eating species have also appeared, such as birds, which are taking
advantage of the increasing numbers of insects. The appearance of small mammals, which
are taking advantage of the expanding range of plant biota and habitats
Loss of Ice Habitat
Predators are appearing to prey on the expanding vertebrate populations, such as birds of
prey that can fly on when winter returns
Pest Species
There is an increased presence of pathogens that parasitise the expanded range of animal
and plant life that the changing habitat supports.