The Greenhouse Effect
The greenhouse effect is the process by which the atmosphere warms the Earth and can be summarised using the diagram below.
1. Solar energy hits the Earth’s atmosphere.
2. Some solar energy is reflected back into space.
3. The rest of the solar energy reaches (and heats) the Earth’s surface.
4. Solar energy is re-radiated back towards space.
5. Some solar energy passes through the Earth’s atmosphere into space.
6. The rest of the solar energy is trapped by greenhouse gases in the Earth’s atmosphere.
The more greenhouse gases are present in the atmosphere, the more solar energy is trapped, and the warmer the Earth becomes. A greenhouse gas can be defined as any gas that is capable of trapping heat within the Earth’s atmosphere, and can be subdivided into natural and anthropogenic (man made). Natural greenhouse gases include carbon dioxide, methane and water vapour, whilst anthropogenic greenhouse gases include chloroflurocarbons (CFCs).
During the last 200 years human activities have resulted in the release of additional greenhouse gases into the atmosphere, which has resulted in an enhanced greenhouse effect and global warming. For example, carbon dioxide is released into the atmosphere due to the combustion of fossil fuels. Since the 18th century the concentration of carbon dioxide in the atmosphere has increased by 30 %, and the levels of methane have more than doubled. A major contributor to increased carbon dioxide emissions is the combustion of fossil fuels, whilst methane is produced for example at landfill sites due to the microbial degradation of material.
The Kyoto Protocol
The Kyoto Protocol is an international agreement aimed at reducing six greenhouse gas emissions (carbon dioxide, methane, nitrous oxide, hydroflurocarbons, perflurocarbons and sulphur hexafluoride) that are linked to climate change. In 1997 at Kyoto (Japan) 110 governments agreed that industrialised countries should cut their greenhouse gas emissions by an average of 5.3 % from 1990 levels by 2008-2012. Specific target reductions vary from country to country. The UK has agreed to reduce greenhouse gas emissions by 12.5 % below 1990 levels by 2008-2012.
Presently 180 countries have signed the agreement, which became law on February 16th 2005. However, the United States (which emits 36.1 % of the world’s greenhouse gases) has pulled out of the agreement.
The Kyoto mechanisms
The three Kyoto mechanisms are:
1. Joint Implementation (JI): emission reductions which arise from project investments in other countries with their own Kyoto emission targets
2. Clean Development Mechanism (CDM): emission reductions arising from project investments in developing countries which don't have their own Kyoto emission targets
3. International Emissions Trading: portions of a country's emission allowances can be bought and sold on an international carbon trading market. Highly polluting countries can buy unused "credits" from those which are allowed to emit more than they actually do.
Site by PerfectArc 2006