WHAT IS THE KYOTO PROTOCOL?

It is a pact agreed by governments at a 1997 UN conference in Kyoto, Japan, to reduce the amount of greenhouse gases emitted by developed countries by 5.2 percent of 1990 levels during the five-year period 2008-2012. A total of 141 nations have ratified the pact, according to UN data.

IS IT THE FIRST AGREEMENT OF ITS KIND?

Governments originally agreed to tackle climate change at an "Earth Summit" in Rio de Janeiro in 1992. At that meeting, leaders created the UN Framework Convention on Climate Change (UNFCCC), which set a non-binding goal of stabilising emissions at 1990 levels by 2000, a goal not met overall. The Kyoto protocol is the follow-up and is the first legally binding global agreement to cut greenhouse gases.

SO IT'S LEGALLY BINDING?

Kyoto will have legal force for its participants from Feb. 16 after meeting twin conditions -- backing from at least 55 countries and support from nations representing at least 55 percent of developed countries' carbon dioxide emissions. It passed the second hurdle in November 2004 when Russia ratified and now has backing from nations representing 61.6 percent of emissions. The United States, the world's biggest polluter, has pulled out, saying Kyoto is too expensive and wrongly omits developing nations.

HOW WILL IT BE ENFORCED?

Under a 2001 deal made by environment ministers in Germany, countries overshooting their targets in 2012 will have to make both the promised cuts and 30 percent more in a second period from 2013. They rejected the idea of a financial penalty.

DO ALL COUNTRIES HAVE TO CUT EMISSIONS BY 5.2 PERCENT?

No, only 39 countries -- relatively developed ones -- have target levels for the 2008-12 period, adhering to the principle set under the UNFCCC that richer countries should take the lead. Each country negotiated different targets, with Russia aiming for stabilisation at 1990 levels and the European Union trying for an 8 percent cut.

HOW ARE THEY DOING SO FAR?

Many countries are lagging behind Kyoto targets. The UNFCCC Secretariat in Bonn says emissions by Spain and Portugal were 40.5 percent above 1990 levels in 2002. US emissions were up 13.1 percent. Emissions by ex-communist bloc states fell most sharply due to the collapse of Soviet-era industries -- Russian emissions were down 38.5 percent.

WHAT ARE THESE "GREENHOUSE GASES"?

Greenhouse gases are gases that trap heat in the earth's atmosphere. The main one is carbon dioxide (CO2), most of which comes from burning fossil fuel. The protocol also covers methane (CH4), much of which comes from agriculture and waste dumps, and nitrous oxide (N2O), mostly a result of fertiliser use. Three industrial gases used in various applications, such as refrigerants, heat conductors and insulators, are also included - they are hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6).

HOW WILL COUNTRIES COMPLY?

The European Union set up a new market in January 2005 under which about 12,000 factories and power stations are given carbon dioxide quotas. If they overshoot they can buy extra allowances in the market or pay a financial penalty; if they undershoot they can sell them. Prices in the EU market are now about 7.2 euros ($9.25) per tonne.

WHAT OTHER MECHANISMS ARE THERE?

The protocol provides for other "flexible mechanisms" -- ways for countries to reach targets without reducing emissions at home. These include the "clean development mechanism" where developed countries can earn credits to offset against their targets by funding clean technologies, such as solar power, in poorer countries.