9.1 Greenhouse gases and global warming

Taking action to combat global warming

Global warming is a major concern at present. A number of organisations, panels and research bodies have been working to gather accurate and relevant information so that a true picture of our current situation can be painted. One important orgaisation that you may have heard of is the Intergovernmental Panel on Climate Change (IPCC). The IPCC was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), to evaluate the risk of climate change brought on by humans. You may also have heard of the Kyoto Protocol , which will be discussed a little later.

Group discussion : world carbon dioxide emissions

The data in the table below shows carbon dioxide emissions from the consumption of fossil fuels (in million metric tons of carbon dioxide).

Questions

1. Redraw the table and use a coloured pen to highlight those countries that are 'developed' and those that are 'developing'.
2. Explain why CO ${}_2$ emissions are so much higher in developed countries than in developing countries.
3. How does South Africa compare to the other developing countries, and also to the developed countries?

Carbon dioxide emissions are a major problem worldwide. The Kyoto Protocol was signed in Kyoto, Japan in December 1997. Its main objective was to reduce global greenhouse gas emissions by encouraging countries to become signatories to the guidelines that had been laid out in the protocol. These guidelines set targets for the world's major producers to reduce their emissions within a certain time. However, some of the worst contributors to greenhouse gas emissions (e.g. USA) were not prepared to sign the protocol, partly because of the potential effect this would have on the country's economy, which relies on industry and other 'high emission' activities.

Panel discussion

Form groups with 5 people in each. Each person in the group must adopt one of the following roles during the discussion:

• the owner of a large industry
• an environmental scientist
• an economist
• a politician
• a chairperson for the discussion

In your group, you are going to discuss some of the economic and environmental implications for a country that decides to sign the Kyoto Protocol. Each person will have the opportunity to express the view of the character they have adopted. You may ask questions of the other people, or challenge their ideas, provided that you ask permission from the chairperson first.

Summary

• The atmosphere is the layer of gases that the surrounds Earth. These gases are important in sustaining life, regulating temperature and protecting the Earth from harmful radiation.
• The gases that make up the atmosphere are nitrogen, oxygen, carbon dioxide, argon and others e.g. water vapour, methane.
• There are four layer in the atmosphere, each with their own characteristics.
• The troposphere is the lowest layer and here, temperature decreases with an increase in altitude. The troposphere is where weather occurs.
• The next layer is the stratosphere where temperature increases with an increase in altitude because of the presence of ozone in this layer, and the direct heating from the sun.
• The depletion of the ozone layer is largely because of CFC's, which break down ozone through a series of chemical reactions.
• The mesosphere is characterised by very cold temperatures and meteor collisions. The mesosphere contains high concentrations of metal atoms.
• In the thermosphere , neutral atoms are ionised by UV and X-ray radiation from the sun. Temperature increases with an increase in altitude because of the energy that is released during this ionisation process, which occurs mostly in the upper thermosphere.
• The thermosphere is also known as the ionosphere , and is the part of the atmosphere where radio waves can be transmitted.
• The auroras are bright coloured skies that occur when charged particles collide with atoms in the upper atmosphere. Depending on the type of atom, energy is released as light at different wavelengths.
• The Earth is heated by radiation from the sun. Incoming radiation has a short wavelength and some is absorbed directly by the Earth's surface. However, a large amount of energy is re-radiated as longwave infrared radiation.
• Greenhouse gases such as carbon dioxide, water vapour and methane absorb infrared radiation and re-emit it back towards the Earth's surface. In this way, the bottom layers of the atmsophere are kept much warmer than they would be if all the infrared radiation was lost.
• Human activities such as the burning of fossil fuels, increase the concentration of greenhouse gases in the atmosphere and may contribute towards global warming .
• Some of the impacts of global warming include changing climate patterns, rising sea levels and a loss of biodiversity, to name a few. Interventions are needed to reduce this phenomenon.

Summary exercise

1. The atmosphere is a relatively thin layer of gases which support life and provide protection to living organisms. The force of gravity holds the atmosphere against the earth. The diagram below shows the temperatures associated with the various layers that make up the atmosphere and the altitude (height) from the earth's surface.

   

   1. Write down the names of the layers A, B and D of the atmosphere.
   2. In which one of the layers of the atmosphere is ozone found?
   3. Give an explanation for the decrease in temperature as altitude increases in layer A.
   4. In layer B, there is a steady increase in temperature as the altitude increases. Write down an explanation for this trend.
2. Planet Earth in Danger It is now accepted that greenhouse gases are to blame for Planet Earth getting warmer. The increase in the number of sudden floods in Asia and droughts in Africa; the rising sea level and increasing average temperatures are global concerns. Without natural greenhouse gases,like carbon dioxide and water vapour,life on earth is not possible. However, the increase in levels of carbon dioxide in the atmosphere since the Industrial Revolution is of great concern. Greater disasters are to come, which will create millions of climate refugees. It is our duty to take action for the sake of future generations who will pay dearly for the wait-and-see attitude of the current generation. Urgent action to reduce waste is needed. Global warming is a global challenge and calls for a global response now, not later. (Adapted from a speech by the French President, Jacques Chirac)
   1. How do greenhouse gases, such as carbon dioxide, heat up the earth's surface?
   2. Draw a Lewis structure for the carbon dioxide molecule
   3. The chemical bonds within the carbon dioxide molecule are polar. Support this statement by performing a calculation using the table of electronegativities.
   4. Classify the carbon dioxide molecule as polar or non-polar. Give a reason for your answer.
   5. Suggest ONE way in which YOU can help to reduce the emissions of greenhouse gases.
3. Plants need carbon dioxide (CO ${}_2$ ) to manufacture food. However, the engines of motor vehicles cause too much carbon dioxide to be released into the atmosphere.
   1. State the possible consequence of having too much carbon dioxide in the atmosphere.
   2. Explain two possible effects on humans if the amount of carbon dioxide in the atmosphere becomes too low.
   (DoE Exemplar Paper Grade 11, 2007)