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A strong change in the global climate poses as one of the main threats to human existence and future development. Since the late nineteenth century, the mean global temperature has increased by 0.4 - 0.8°C and the sea level has risen by 10 to 15cm. A doubling of the CO2 concentration in the atmosphere is believed to cause an increase in the global mean temperature of 1.5 to 4.5°C. Human influenced climate change is triggered by a concentration change of chemical substances (called greenhouse gases - GHG) in the Stratosphere through human influence.
The United Nations Framework Convention on Climate Change entered into force in March 1994. The Convention includes a commitment by developed country parties, including economies in transition (Annex I Parties), aiming at the return of CO2 and other GHG emissions to their 1990 levels.
The Kyoto Protocol (adopted 1997), which entered into force 16 February 2005, sets targets for each of the developed country parties and economy in transition parties with a view to reducing their overall emissions of the six main GHGs by at least 5 per cent below 1990 levels in the commitment period 2008 to 2012. The latest monitoring data indicates that the European Union has delivered on its long-standing commitment to stabilise emissions of CO2 at the level of 1990 in the year 2000. The EU-15 is committed to deliver a collective 8% cut in emissions by 2008-2012 and equally the New Member States are determined to meet their individual targets under the Kyoto Protocol. The EU addresses its own greenhouse gas emissions through launching the European Climate Change Programme (ECCP). The ECCP led to the adoption of a range of new policies and measures, e.g. the EU's emissions trading scheme, which started its operation on 1 January 2005. The scheme is based on Directive 2003/87/EC, which entered into force on 25 October 2003.
Some substances, though, do not 'only' have dangerous impacts on the global climate but do also pose a danger to the ozone layer. Such ozone-depleting greenhouse gases (such as CFCs and HCFCs) are controlled by the Vienna Convention and the Montreal Protocol.
Depletion of the ozone-layer
The ozone depletion process on the other hand begins when Chlorofluorocarbons (CFCs) and other ozone-depleting substances are emitted into the atmosphere. CFCs are extremely stable compounds, and do not dissolve in rain. After a period of several years, molecules reach the stratosphere, about 10 kilometers above the Earth's surface. Strong UV light breaks apart the Ozone-depleting substances molecule with the formation of free radicals. Those free radicals actually destroy ozone, not the intact molecule. It is estimated that one chlorine radical can decompose over 100,000 ozone molecules before it is removed from the stratosphere. Ozone is constantly produced and decomposed in a natural cycle and the overall amount of ozone is essentially stable, which was the 'natural' situation until the past several decades. Since then large increases in stratospheric chlorine and bromine, however, have upset that balance and have added a siphon downstream, removing ozone faster than natural ozone creation reactions can keep up. Therefore, ozone levels fall and the natural ozone layer is depleted.
Since ozone filters out harmful UVB radiation, less ozone means higher UVB levels at the surface. The more the depletion, the larger the increase in incoming UVB. UVB has been linked to skin cancer, cataracts, damage to materials like plastics, and harms certain crops and marine organisms. Although some UVB reaches the surface even without ozone depletion, its harmful effects will increase as a result of the anthropogenic ozone depletion.
According to the Impact Assessment Guidelines of the European Commission, the following key question is of particular importance when examining the impacts of policy initiatives on climate change:
- IA TOOLS
- The European Commission's site on Climate Change (To appreciate the magnitude of this temperature increase, it should be compared with the global mean temperature difference of perhaps 5 to 6°C from the middle of the last ice age to the present interglacial period.)
- The EU Emission Trading Scheme (EU ETS)
- UNEP - Intergovernmental Panel on Climate Change IPCC
- The European Environment Agency's site on Climate Change
- United Nations Environment Programme (UNEP): Ozone Secretariat - Montreal Protocol
- UNEP: The 1985 Vienna Convention for the Protection of the Ozone Layer
- JRC: IA TOOLS. Supporting inpact assessment in the European Commission. 
This text is for information only and is not designed to interpret or replace any reference documents.