WHAT IS THE KYOTO PROTOCOL?

It is a pact agreed on by governments at a 1997 United Nations 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. Eighty-four countries have signed the pact and 50 of have ratified it or acceded to it, according to U.N. data.

IS IT THE FIRST AGREEMENT OF ITS KIND? Governments originally agreed to tackle climate change at the "Earth Summit" in Rio in 1992. At that meeting, leaders created the U.N. Framework Convention on Climate Change (UNFCCC) which set a non-binding goal of stabilising emissions at 1990 levels by 2000. Although the convention has more than 160 participants, it is widely considered to have failed to halt a global increase in emissions.

The Kyoto Protocol is the follow-up to that and is the first legally binding global agreement to cut greenhouse gases.

SO IT'S LEGALLY BINDING?

It is binding once it has been ratified (approved at government or parliament level) by 55 percent of the signatories representing 55 percent of developed countries' carbon dioxide emissions.

HOW WILL IT BE ENFORCED?

Under a deal made by environment ministers in Bonn, Germany, in July 2001, if countries emit more gases than allowed under their targets at the end of 2012, they will be required to make the cuts, and 30 percent more, in the second commitment period which is due to start in 2013. Ministers rejected the idea of having a financial penalty. Compliance will be overseen by a special committee.

WHAT WAS AGREED IN MARRAKESH IN NOVEMBER 2001?

The rules cover issues such as what penalties countries that fail to reach their targets will face, how they can buy and sell the right to emit greenhouse gases, and to what extent countries must report on the amount of emissions they produce each year.

The Bonn agreement set out the sanctions a country would face if it failed to meet its emissions targets. Wrangling at Marrakesh centred on whether this would be legally binding. Japan and Russia resisted moves to make it so.

A compromise wording was found which postponed a formal decision on the exact legal nature of compliance, but stated that countries must accept the agreed compliance rules if they want to take part in emissions trading.

Supporters of the pact say this provides the detailed legal basis for countries to ratify it and bring it into force.

DOES EVERY COUNTRY HAVE TO REDUCE EMISSIONS BY 5.2 PERCENT?

No, only 39 countries - relatively developed ones - have target levels for the first five-year commitment period, adhering to the principle established under the UNFCCC that richer countries should take the lead. Each country negotiated slightly different targets, with the United States aiming for a seven percent reduction, Russia for stabilisation at 1990 levels and Australia allowed an eight percent increase. The 15 European Union countries took an eight percent cut and then later shared out the effort differently among member states.

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 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). One group of greenhouse gases not included is chlorofluorocarbons (CFCs), previously used in aerosols and refrigeration, because these have been banned by a separate treaty aimed at protecting the ozone layer.

SO EACH COUNTRY HAS TO REDUCE ITS EMISSIONS BY THAT AMOUNT BY THE 2008-2012 PERIOD? WHAT IF IT CAN'T?

The protocol provides for "flexible mechanisms" - ways for countries to reach their targets without actually reducing emissions at home. These include emissions trading - where one country buys the right to emit from another country which has already reduced its emissions sufficiently and has "spare" emissions reductions.

Another is 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. Countries can also claim credits for planting trees that soak up CO2 - so-called carbon "sinks".

DOES THIS MEAN THE KYOTO PROTOCOL IS NOW UP AND RUNNING?