Topic 5.2 The Greenhouse Effect

Question 1

5.2.1 Draw and label a diagram of the carbon cycle to show the processes involved.

Answer 1

Question 2

5.2.2 Analyze the changes in concentration of atmospheric carbon dioxide using historical records.

Answer 2

• from measuring CO₂ concentration in trapped air in Antarctican ice: for 2 000 years before 1880, the carbon dioxide concentration of the atmosphere remained fairly constant at about 270 ppm.
• Now, has risen to about 400 ppm as of 2015 (Mauna Loa observatory, Hawaii)
• annual fluctuation, but overall trend is increasing [CO₂]

Question 3

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

Answer 3

The enhanced greenhouse effect is the additional warming of the Earth caused by increased amounts of greenhouse gases (inc. CO₂, methane, oxides of nitrogen, water vapour).

• All these gases occur naturally
• Human activity has increased normal level of gases in recent years
• Incoming short wave radiation from the sun
• Some of this radiation is reflected by the earth’s surface back into space as long wave/infrared radiation
  
  • mainly in form of heat
• Greenhouse gases absorb this infrared radiation and re-reflect back to earth, resulting in increased atmospheric/ocean temperatures (the greenhouse effect)
  
  • at higher rate than normal
  • threatens ecosystems
• Earth has history of many fluctuations in gas levels/global temperature
  
  • humans causing enhanced greenhouse effect (through emitting gases through deforestation, industrializaion, increased agriculture, etc.) is still being debated

Question 4

5.2.4 Outline the precautionary principle.

Answer 4

• states that preventative action should be taken now to reduce carbon emissions and greenhouse gas production before it is too late. Furthermore, the principle holds that those who wish to continue producing excess greenhouse gases should prove that there is no harmful effects before continuing.
• 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.

Question 5

5.2.5 Evaluate the precautionary principle as a justification for strong action in response to the threats posed by the enhanced greenhouse effect.

Answer 5

Precautionary Principle

• those proposing something must prove that it causes no harm before they start to do it
• objectors do not have to prove that there will be harm
• activities that risk/threaten/may cause harm are banned
• trials/tests must be done first

Support for Precautionary Principle

• no sufficient data, but can be good protection; later may be too late
• consequences = more severe if we wait
• could result in scientific innovation
• potential cost is huge if we don’t

Opposition for Precautionary Principle

• could hinder development in undeveloped countries​
• could affect economy
• may be too expensive to be realistic

Question 6

5.2.6 Outline the consequences of a global temperature rise on arctic ecosystems.

Answer 6

C hanges in arctic climate

R ising sea levels and changing salinity

E xpansion of the range of habitats available to temperate species

D ecomposition of detritus previously trapped in permafrost

I ncreased competition/increased success of pest species including pathogens

B ehavioural changes

L oss of ice habitat

E xtinction