4.2 – The Greenhouse Effect

4.2 – The Greenhouse Effect

4.2.1 – 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


4.2.2 – 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 CO2 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 CO2 levels to be determined. The temperature can be determined from the ratio of O16 to O18. From this, in has been concluded that there is a clear correlation between atmospheric CO2 and temperature. Of course, correlation does not mean causation.

4.2.3 – Explain the relationship between rises in concentrations of atmospheric carbon dioxide, methane and oxides of nitrogen and the enhanced greenhouse effect

The greenhouse effect is a natural phenomenon that creates moderate temperatures on Earth to which life has adapted. The Earth has relatively little CO2 in its atmosphere compared to planets like Venus. The enhanced greenhouse effect, however, is the idea

The enhanced greenhouse effect, however, is the idea that the activities of humans are increasing the levels of CO2 and other greenhouse gases in the atmosphere. This in turn may lead to increased global temperatures and climate change. Gas molecules in our atmosphere with three or more atoms can capture

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 H2O, 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.



4.2.4 – 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.

4.2.5 – 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.

The General Effects include:

  • Increased frequency and intensity of droughts
  • Flooding due to higher rainfall, increased snowmelts, rising sea levels
  • Declines in food production
  • Increased disease, as warmer temperatures allow for increased numbers of pathogens
  • More extreme weather
  • Loss of biodiversity


4.2.6 – Outline the consequences of a global temperature rise on arctic ecosystems

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

This temporarily leads to extensive flooding of surrounding low-lands

Distribution of Prey Species

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.