5.2 The Greenhouse effect

1. 5.2 The Greenhouse effect

2. Assessment Statements Draw and label a diagram of the carbon cycle to show the processes involved. Analyze the changes in concentration of atmospheric carbon dioxide using historical records. Explain the relationship between rises in concentrations of atmospheric carbon dioxide, methane and oxides of nitrogen and the enhanced greenhouse effect. Outline the precautionary principle. Evaluate the precautionary principle as a justification for strong action in response to the threats posed by the enhanced greenhouse effect. Outline the consequences of a global temperature rise on arctic ecosystems.

3. The Carbon Cycle Carbon is one of the most important elements that are recycled in an ecosystem.

4. Inorganic carbon dioxide in the atmosphere is trapped or “fixed” as organic carbon compounds during photosynthesis. Some of the carbon is returned to the atmosphere as the plants respire. The other steps in the cycle follow the same path as food chains. As herbivores eat plants, and carnivores eat herbivores, the carbon compounds move from plants to animals.

5. Respiration by any organism in this sequence returns carbon to the atmosphere as carbon dioxide and when a plant or animal dies, carbon compounds move to detritivores and saprotrophs which may also respire. http://www.youtube.com/watch?v=U3SZKJVKRxQ http://www.youtube.com/watch?v=Xz0fn81BlIQ

6. In some conditions, plants and animals do not decay when they die. They become compressed and fossilized in a process that takes millions of years and forms fossil fuels. Vast coal, oil and natural gas deposits have been formed and the carbon trapped in these fuels cannot return to the atmosphere unless the fuels are burned. Over a very long period of time, fossil fuel formation has gradually lowered the carbon dioxide level of Earth’s atmosphere, but recently this balance has been upset.

7. Draw a labeled diagram showing stages of the carbon cycle. [5]

8. How the Greenhouse Effect Works Certain gases, including CO2 enable the atmosphere to retain heat. Without these gases in the atmosphere, the Earth’s temperature would be too low to support life. The warming effect of these gases is known as the greenhouse effect because it is works in a similar way a greenhouse works.

9. A greenhouse is made of glass, which allows shorter-wave radiation from the sun to pass through it. As the sunlight passes through the glass, the radiation is changed into heat, which has a longer wavelength. Glass is less transparent to theses long wavelengths and heat is trapped in the greenhouse, making it warmer. The greenhouse gases such as carbon dioxide, methane, and water vapor act the same way. They trap the heat and keep the temperature comfortable for life to exist.

10. Greenhouse gases, Human Activity and Global Warming Carbon dioxide forms only 0.04% of the atmospheric gases but it plays a significant part in the greenhouse effect. Other greenhouse gases include water vapor, methane, oxides and fluorocarbons (FCs). Chlorofluorocarbons (CFCs) were used in aerosols and as refrigerants but were found to damage the ozone. They were replaced with hydrofluorcarbons (HFCs), but HFCs are causing problems because they are a greenhouse gasses.

11. Human population has increased dramatically in the last hundred years. Increased population calls for an increased demand for energy in industry, transport and homes. Most of this energy demand has been met by burning fossil fuels, mainly coal, oil and gas.

12. Burning fossil fuels releases both carbon dioxide and oxides of nitrogen. Burning these fuels has raised the concentration of carbon dioxide in the Earth’s atmosphere by more than 20% since 1959

13. In the tropical regions of the world vast rainforests trap carbon dioxide through photosynthesis and have been important in maintaining the low level of carbon dioxide. We upset this balance by deforesting vast areas of forests for agriculture and timber production. 78,000 square miles are lost every year. Forest destruction has multiple effects, but most important for the atmosphere are the loss of carbon dioxide uptake and the increase of carbon dioxide released from the rotting or burnt vegetation.

14. Another important result of rising carbon dioxide levels is lowering of the pH of the oceans as carbon dioxide dissolves in them. Acidic oceans may inhibit the growth of the producers, weakens shells and coral, which affects the food chains.

15. Atmospheric Carbon Dioxide levels Safe level of atmospheric CO2 is 350ppm.

17. Methane is another important greenhouse gas. It’s produced by human activity when organic waste decomposes, it also comes from rice paddies and from cattle farming. As the human population increases the need for food increases, resulting in more rice paddies and cattle farming. Cattle release methane from their digestive systems as they process their food.

18. Climatologists are concerned that, as a result of all this activity, humans are adversely affecting our atmosphere. Rising levels of greenhouse gases are believed to be causing an enhancement of the natural greenhouse effect.

19. Earth is experiencing a rise in average global temperature, known as global warming, which is thought to be happening because of this enhanced greenhouse effect. Global warming is a too simplistic of a term. Some areas of the world will become colder, a better term is climate change.

20. Some Results of Climate Change Melting of ice caps and glaciers Rising sea levels, causing flooding Change in the pattern of climate, leading to changes in ecosystems and the distribution of plants and animals

21. One liter of gasoline comes from 23.5 tons of ancient organic material. The total amount of fossil fuels used in 1997 was estimated to have been produced from all plant matter that grew on the surface and all the oceans of the ancient Earth from a period of more than 400 years. Earth’s coal supply will last for 1500, however, with a 5% growth rate will only last 86. As supplies of other fossil fuels diminish, coal will be used more.

22. The Precautionary Principle The precautionary principle suggests that if the effect of a change caused by humans is likely to be very harmful to the environment, actions should be taken to prevent it, even if there may not be sufficient data to prove that the activity will cause harm. This principle is often applied to the impact of human actions on the environment and human health, as both are complex and the consequences may be unpredictable.

23. The precautionary principle challenges governments, industries and consumers to take action without waiting for definitive scientific proof to be forthcoming.

24. Evaluating the Precautionary Principle Should the precautionary principle be used to justify action to reduce the impact of the release of greenhouse gases into the atmosphere before irreparable harm is done? Here are some arguments to discuss: Climate change has consequences for the entire human race and an international solution is needed to tackle the problems. It is not always the case that those who produce the most greenhouse gases suffer the greatest harm so it is essential that measures to reduce emissions are taken with full international cooperation. If industries and farmers in one area invest money to reduce their greenhouse gases while those in other areas don’t, an economic imbalance may be created in favor of the more polluting enterprises, who can offer services more cheaply. Consumers can be encouraged to use more environmentally friendly goods and services. It is unethical for one generation to cause harm to future generations by not taking actions to address the problem of greenhouse gases. Scientists can argue that it is better to invest in a sustainable future and prevent further harm.

25. Global Temperature rise and Arctic Ecosystems The ecosystems of the Arctic include the tundra, permafrost and the sea ice in the north Pole. Records have shown considerable changes in recent years. Average annual temperatures in the Arctic have increased by double the increase in global temperatures, which results in the melting of sea ice and glaciers.

26. Melting sea ice affects many species. Algae, which hare important producers in Arctic food chains, are found just beneath the sea ice. As ice disappears, so do the algae and this affects numerous other organisms that use them as food. Populations of marine mammals, caribou and polar bears are also affected. Caribou are falling through once-solid sea ice and polar bears which live on sea ice while hunting for prey, now have shorter feeling periods and decreased access to seals that they hunt. Polar bears numbers are decreasing at an alarming rate.

27. Forest and tundra ecosystems are important features of the Arctic environment. In Alaska, substantial changes in forest life, including increases in insect pests. Rising temperatures have allowed spruce bark beetles to reproduce rapidly, one outbreak caused the loss of over 2.3 million acres of trees. Detritus, which is dead organic matter is trapped in the frozen tundra is released as the ground thaws. The detritus decomposers and the carbon dioxide and methane producers are released into the atmosphere, adding to the rising greenhouse gas levels.

28. Explain the relationship between rises in concentration of atmospheric gases and the enhanced greenhouse effect. [8] Award [2 max] from the following list of greenhouse gases: water vapour; carbon dioxide; methane; oxides of nitrogen; all (of these gases) occur naturally; and human activity has increased the normal level of these gases in recent years; incoming shorter wave radiation from the Sun; is re-radiated as longer wave radiation/infrared; (mainly) in the form of heat; captured by greenhouse gases; which increases the atmospheric/ocean temperature; at a higher rate than normal / creating a positive imbalance; which threatens ecosystems/climatic patterns/ocean patterns; Earth’s history had many fluctuations in gas levels/global temperature / some scientists are skeptical about enhanced greenhouse effect;

29. Outline the precautionary principle. [2] some human-induced change can be very large/perhaps catastrophic; those responsible for the change must prove it will cause no harm before proceeding; appropriate (environmental/medical etc.) example e.g. companies must immediately reduce emission of greenhouse gases even though proof of human impact on global warming is still debated; is reverse of historical practice / previously those concerned about change had to prove it will do harm to prevent such changes from going ahead / paradigm shift; [2 max]

30. Outline how global warming may affect arctic ecosystems. [5] global warming is an increase in temperature of the atmosphere/oceans/Earth; may result in climate change / changes in amount of precipitation / greater ranges in temperature; melting ice leads to rising of sea level; leading to loss of habitat / example of organism that would lose habitat; changes in salinity / changes in ocean currents change distribution of nutrients; changes in predator-prey relationships (due to ecosystem disruption); increased success of pest species; temperate species with bigger range of habitats as ice melts; increased rate of decomposition of detritus;

31. Below is a graph of atmospheric CO2 levels measured at Mauna Loa Observatory, Hawai’i. Explain the observed changes in atmospheric CO2 concentration from 1960 to 2005. [3] from 1960–2005) atmospheric concentration increases/strong positive trend / increase between 1960–2005 of 65 ppm/figures to that effect; CO2 released by human activities contributes to the increase; CO2 examples of human activities e.g. combustion of fossil fuels / deforestation; seasonal/annual fluctuations (do not prevent long-term increase); [3 max]

32. List 3 groups of organisms in the carbon cycle that transfer carbon dioxide to the atmosphere. State the process in the carbon cycle by which carbon dioxide is fixed as organic carbon-containing compounds. List 3 greenhouse gases. List 5 human activities that are causing an increase in the levels of greenhouse gases in the atmosphere. List 3 ways in which a rise in average global temperature is having an effect on Arctic ecosystems.