What is Kyoto protocol?

In 1997, delegates from 194 nations met in Kyoto, Japan, and collectively promised to reduce greenhouse gas emissions by about 5 percent below 1990 levels by 2012, as a first step toward global cooperation on limiting carbon-driven climate change. The treaty they produced, known as the Kyoto Protocol, expires at the end of 2012.

The treaty required the major industrialized nations to meet targets on emissions reduction but imposed no mandates on developing countries, including emerging economic powers and sources of global greenhouse gas emissions like China, India, Brazil and South Africa.

The United States is not a party to the protocol. It was negotiated by the Clinton administration, but the Senate voted 95 to 0 against even considering ratification because of those asymmetrical obligations. President George W. Bush flatly repudiated it.

Some major countries, including Canada, Japan and Russia, have said they will not agree to an extension of the protocol unless the unbalanced requirements of developing and developed countries are changed. That is similar to the United States’ position, which is that any successor treaty must apply equally to all major economies.

But the European Union, the major developing countries, and most African and Pacific island nations would like to see the Kyoto process extended as a prelude to a more ambitious, binding international agreement that would take effect 2020. The goal would be to reduce emissions enough to keep the average global temperature from ever rising more than 2 degrees Celsius, or about 3.6 degrees Fahrenheit, above its current level.

The fate of the Kyoto agreement was a central topic at the international gathering on global warming in Durban, South Africa, in December 2011.

But the issue was left unresolved at the meeting, which ended with modest accomplishments: the promise to work toward a new global treaty in coming years. The future treaty deal renewed the protocol for several more years. It also began a process for replacing the protocol with something that treats all countries — including the economic powerhouses China, India and Brazil — equally. The future treaty deal was the most highly contested element of a package of agreements that emerged from the extended talks among the 200 nations that met in Durban. The expiration date of the protocol — 2017 or 2020 — and the terms of any agreement that replaces it will be negotiated at future sessions.

The United States has been criticized at such gatherings for years, in part because of its rejection of the Kyoto framework and in part because it has not adopted a comprehensive domestic program for reducing its own greenhouse gas emissions.

President Obama has pledged to reduce American emissions 17 percent below 2005 levels by 2020, but his preferred approach, a nationwide cap-and-trade system for carbon pollution, was blocked in the Senate in 2010 after being passed by the House the year before.

United States emissions are down about 6 percent over the past five years, largely because of the drop in industrial and electricity production caused by the recession.