River and Air Condition

River and Air are the same in that they both have no property, but their qualities are both important to us.
When it comes air condition, there is Discharge Permit System.
Carbon Trade is the same way using in air condition control.They all play roles By controlling the total amount of emission.

Kyoto Protocol

In order to save human beings from the threat of global warming, “United Nations Framework Convention on Climate Change” the Third Conference adopted the “Kyoto Protocol” to limit greenhouse gas emissions by developed countries to curb global warming in December 1997, held in Kyoto, Japan,

The Kyoto mechanisms

Under the Treaty, countries must meet their targets primarily through national measures. However, the Kyoto Protocol offers them an additional means of meeting their targets by way of three market-based mechanisms.
*Clean development mechanism (CDM)
*Joint implementation (JI)
*Emissions trading (Et)

CDM

CDM is based on the fact that emissions of gasleading to our global warming  are in one place – our air, regardless of the source of these gases(from which country). Similarly, the reduction is to reduce emissions, regardless of where it occurs.
Therefore, in the clean development mechanism, among a signatory to the Kyoto Protocol, developed countries (such as the United Kingdom) invest on the greenhouse gas emission reduction projects and  transfer technology in developing countries (such as China).
If these projects prove that they can not be implemented without without the support of the Clean Development Mechanism, the developed countries will be able to get carbon credits which makes the developed countries ensure their emissions below the limit.