A factfile on the Kyoto Protocol which got a new lease of life at UN climate talks in Doha, albeit in a watered-down guise covering only about 15 percent of the world's greenhouse gas emissions.
WHAT IS IT?
With 191 members, the 1997 Kyoto Protocol is the only global treaty with binding limits on Earth-warming greenhouse gas emissions.
Its first leg, which expires on December 31, committed 37 developed "Annex 1" economies to an average 5% cut from 1990 levels in the period 2008-2012 -- a target that was largely met.
When the pact came into force in 2005, it bound countries responsible for nearly two-thirds of global emissions.
It excluded developing countries like China and India, which have since become the world's largest and fourth largest polluters according to the International Energy Agency, as well as second-placed United States which refused to ratify the deal.
From January 1, 2013 to the end of 2020, when a new, global deal will enter into force, the protocol will live on in the form of a "second commitment period."
Russia, Japan, New Zealand and Canada, the only country to have withdrawn from the pact, have not renewed their emissions targets in a second round.
WHO IS IN?
The 27-member European Union has committed itself to a 20 percent cut on 1990 emission levels, dismissing calls to raise the bar to 30 percent.
The other signatories and their targets are:
Australia -- 5% on 2000 levels (the only country not to use 1990 as a base year.
Belarus -- 8%
Croatia -- 20% (with the EU)
Iceland -- 20% (with the EU)
Kazakhstan -- 7%
Liechtenstein -- 20%
Monaco -- 30%
Norway -- 30%
Switzerland -- 20%
Ukraine -- 20%
The protocol's text, amended in Doha, commits parties to revisiting their targets, with a view to increasing them, by 2014.
HOW DOES IT WORK?
Annex 1 countries can meet their targets by cutting emissions or buying unused allowances from other countries, or earn credits by funding Earth-friendly energy projects in developing nations, which they can sell or use to offset emissions.
Former East Bloc countries like Russia and Poland managed to stock up billions of credits because of lenient targets, so-called "hot air" which the new deal allows them to bank into a follow-up period. The text is quiet on what happens after 2020.
"Hot air," when traded, causes emissions to be cancelled on paper but not in the atmosphere.
Most potential markets, including the EU and Australia, have said they will not be buying credits carried over from 2012 -- an issue that complicated the Doha negotiations with Russia and Poland.
The UN has set a target of limiting global warming to 2.0 degrees Celsius (3.6 Fahrenheit) from pre-industrial levels -- a level at which scientists say the planet may be spared the worst impacts of climate change.