On February 16, 2005 (January 8, 2005 lunar calendar), the Kyoto Protocol officially came into force. On February 16, 2005, the Kyoto Protocol, which aims to curb global warming, came into force. This is the first time in human history that greenhouse gas emissions are limited in the form of regulations. The Kyoto Protocol stipulates that by 2010, the emissions of six greenhouse gases, including carbon dioxide, in all developed countries will be reduced by 5.2% compared with 1990. Developed countries must meet their reduction targets from 2008 to 2012. This is a file photo taken at the venue of the United Nations climate conference in Kyoto, Japan on December 9, 1997. The United States accounts for only 3% to 4% of the world's population, but it emits more than 25% of global carbon dioxide emissions, making it the world's largest emitter of greenhouse gases. The United States signed the "Kyoto Protocol" in 1998. But in March 2001, the Bush administration announced its refusal to ratify the "Kyoto Protocol" on the pretext that "reducing greenhouse gas emissions will affect the economic development of the United States" and "developing countries should also undertake the obligation to reduce and limit greenhouse gas emissions." On February 16, 2005, the "Kyoto Protocol" came into force. This is the first time in human history that greenhouse gas emissions are limited in the form of regulations. In order to promote countries to meet their greenhouse gas reduction targets, the protocol allows the following four ways to reduce emissions:? First, "emissions trading" between two developed countries where emission allowances can be bought and sold, that is, countries that are difficult to complete the reduction task can spend money to buy the excess quota from the country that has exceeded the task. Second, the greenhouse gas emissions are calculated as "net emissions", that is, the amount of carbon dioxide absorbed by forests is deducted from the actual emissions of the country. Third, the green development mechanism can be used to urge developed and developing countries to jointly reduce greenhouse gas emissions. Fourth, the "group approach" can be adopted, that is, many countries within the European Union can be regarded as a whole, and some countries can reduce and some countries can increase to complete the emission reduction task as a whole. In December 2011, Kent, Canada's environment minister, said that the decision to join the Kyoto Protocol was a mistake. Because the protocol's emission reduction control outline does not apply to the two largest gas emitters, the United States and China, it is doomed to fail, and Canada also decided to withdraw. He pointed out that Canada supports the new emission reduction agreement reached at the climate conference in Durban, South Africa, and believes that emission reduction should be a global joint action, and all countries should also be bound. On December 31, 2012, the "Kyoto Protocol" officially failed.