The international agreement to reduce greenhouse-gas emissions that was implemented in 2005 is known as the Kyoto Protocol. The protocol was adopted in 1997 and came into force in 2005. It aimed to reduce greenhouse gas emissions from industrialized countries by at least 5% below 1990 levels by the year 2012. It also established a system of emissions trading, where countries that exceeded their emissions reduction targets could purchase credits from countries that had exceeded their targets. However, some major emitters such as the United States did not ratify the protocol, while others such as Canada, Russia, and Japan withdrew later on. The protocol was widely criticized for its limited scope and lack of binding emissions reduction targets for developing countries. Despite these limitations, the Kyoto Protocol paved the way for future international climate agreements, such as the Paris Agreement in 2015.