5.2 The Greenhouse Effect

Question 1

State the four main pools of carbon in the environment

Answer 1

• Sediments: Carbon deposits in the lithosphere, as minerals (carbonates) or fossil fuels
  
  • Ocean: Dissolved CO2 in aquatic systems
    
    • Biosphere: Organic carbon in living organisms
    • Atmosphere: Atmospheric gases (CO2 and Methane)

(SOBA)

Question 2

State the processes by which carbon can be moved in the environment

Answer 2

Photosynthesis, Feeding, Respiration, Fossilisation, Combustion, Diffusion

Question 3

Outline how carbon moves in the environment via Photosynthesis

Answer 3

Atmospheric carbon dioxide is removed and fixed as organic compounds (e.g. sugars) by plants and algae

Question 4

Outline how carbon moves in the environment via Feeding

Answer 4

Organic carbon is moved from one trophic level to the next in a food chain

Question 5

Outline how carbon moves in the environment via Respiration

Answer 5

All organisms (including plants) metabolise organic compounds for energy, releasing carbon dioxide as a by-product

Question 6

Outline how carbon moves in the environment via Fossilisation

Answer 6

Carbon from partially decomposed dead organisms becomes trapped in sediment as coal, oil and gas (fossil fuels)

Question 7

Outline how carbon moves in the environment via Combustion

Answer 7

During the burning of fossil fuels and biomass, carbon is released into the atmosphere

Question 8

Outline how carbon moves in the environment via Diffusion

Answer 8

In oceans, carbon can be reversibly trapped and stored as limestone (storage happens more readily at low temperatures

Question 9

Outline some of the recent trends in the changing concentrations of carbon in the atmosphere

Answer 9

Atmospheric CO2 concentrations have been measured at the Mauna Loa atmospheric observatory in Hawaii from 1958. Carbon dioxide is released unevenly around the world, due to distribution of vegetation. There is an annual cycle in CO2concentrations which are attributable to seasonal factors, but when data from the two hemispheres is incorporated, it suggests that atmospheric CO2levels have risen steadily in the past 30 years.

Question 10

Outline the study of past and future changes in atmospheric carbon concentration

Answer 10

Carbon dioxide concentration changes over a long period of time have been determined by a variety of sources, including analysing the gases trapped in ice. Fluctuating cycles of CO2concentrations over thousands of years appear to correlate with global warm ages and ice ages. CO2levels appear to be currently higher than at any time in the last 400,000 years. There is a clear correlation between atmospheric CO2 concentrations and temperature.

Question 11

State four greenhouse gasses

Answer 11

• Water vapour
  
  • Carbon Dioxide (CO2)
  • Methane
  • Nitrous Oxide (NO2)

Question 12

Outline the principles of the greenhouse effect

Answer 12

The greenhouse effect is a natural process whereby gasses in the Earth’s atmosphere (greenhouse gasses) trap radiation within the troposphere, raising temperatures, and creating a temperate climate to which all life has adapted. Without the natural greenhouse effect, the temperatures of the Earth would not be warm enough to sustain life.

Question 13

Outline the principles of the enhanced greenhouse effect

Answer 13

The enhanced greenhouse effect is the idea that increase CO2 emissions caused by human activities (burning of fossil fuels) is leading to increase global temperatures, and climate change. Elevated levels of greenhouse gases are strongly correlated with an enhanced greenhouse effect. Shortwave ultraviolet rays come from the sun, and the Earth reflects back long wave infrared radiation. The increase of greenhouse gasses in the atmosphere means that more infrared light is absorbed and re-reflected by the atmosphere. As levels of greenhouse gasses in the atmosphere increases, more radiation is reflected back to Earth instead of being lost to space.

Question 14

Outline the precautionary principle

Answer 14

“The precautionary principle states that when a human-induced activity raises a significant threat of harm to the environment or human health, then precautionary measures should be taken even if there is no scientific consensus regarding cause and effect”

• i.e. If it cannot be proven that no harm will come of an action, it must not go ahead

Question 15

Discuss the precautionary principle in relations to climate change

Answer 15

Because the global climate is a complex phenomena with many emergent properties, and is based on time frames well beyond human lifespans, it is arguably impossible to provide appropriate scientific evidence for enhanced global warming before consequences escalate to potentially dire levels. According to the precautionary principle, the onus falls on those contributing to the enhanced greenhouse effect to either reduce their input or demonstrate their actions do not cause harm - this makes it the responsibility of governments, industries, communities and even the individual. The precautionary principle is the reverse of previous historical practices whereby the burden of proof was on the individual advocating action

Question 16

Discuss the arguments for action against climate change

Answer 16

Risks of inaction are potentially severe, including increased frequency of severe weather conditions (e.g. droughts, floods) and rising sea levels. Higher temperatures will increase the spread of vector-borne diseases. Loss of habitat will result in the extinction of some species, resulting in a loss of biodiversity. Changes in global temperature may affect food production, resulting in famine in certain regions. The effects of increased temperatures (e.g. rising sea levels) could destroy certain industries which countries rely on, leading to poverty. All of these consequences could place a far greater economic burden on countries than if action were taken now. These factors would increase competition for available resources, potentially leading to increased international tension.

Question 17

Discuss the arguments for inaction against climate change

Answer 17

Cutting greenhouse emissions may delay economic growth in developing countries, increasing poverty in these regions. Boycotting trade with non-compliant countries could negatively effect economies and create international tensions. No guarantee that human intervention will be sufficient to alter global climate patterns. Money and industrial practices that may be used to develop future technologies may be lost due to restrictions imposed by carbon reduction schemes. Carbon reduction schemes will likely result in significant job losses from key industries, retraining workers will require significant time and money.

Question 18

Outline the consequences of global temperature rise on Arctic ecosystems

Answer 18

Increases in global temperature pose a”credible”threat to Arctic ecosystems:
• Changes in Arctic conditions (reduced permafrost, diminished sea ice cover)
• Rising sea levels
• Expansion of temperate species increasing competition with native species (e.g. red fox vs Arctic fox)
• Decomposition of detritus previously trapped in ice will significantly increase greenhouse gas levels (potentially exacerbating temperature changes)
• Increased spread of pest species and pathogens (threatening local wildlife)
• Behavioural changes in native species (e.g. hibernation patterns of polar bears, migration of birds and fish, seasonal blooms of oceanic algae)
• Loss of habitat (e.g. early spring rains may wash away seal dens)
• Extinction and resultant loss of biodiversity as food chains are disrupted