COPENHAGEN?This decade is very likely to be the warmest since record keeping began in 1850, and 2009 could rank among the top five warmest years, the UN weather agency reported Tuesday on the second day of a pivotal 192-nation climate conference.

In some areas?parts of Africa and central Asia?this will probably be the warmest year, but overall 2009 ?is likely to be about the fifth-warmest year on record,? said Michel Jarraud, secretary general of the World Meteorological Organization.

The decade 2000-2009 ?is very likely to be the warmest on record, warmer than the 1990s, than the 1980s and so on,? Jarraud said at a news conference, holding up a chart with a temperature curve pointing upward.

If 2009 ends as the fifth-warmest year, it would replace the year 2003.

According to the US space agency NASA, the other warmest years since 1850 have been 2005, 1998, 2007 and 2006.

The data were released as negotiators at the two-week talks in Copenhagen worked Tuesday to craft a global deal to step up efforts to stem climate change, digging into the dense technicalities of ?metrics? and ?gas inventories.?

Scientists say without an agreement to wean the world away from fossil fuels and other pollutants to greener sources of energy, the Earth will face the consequences of ever-rising temperatures: The extinction of plant and animals, the flooding of coastal cities, more extreme weather, more drought and the spread of diseases.

On Tuesday, delegates were digging into the dense technicalities of ?metrics? and ?gas inventories,? as governments jockeyed for position leading up to the finale late next week, when more than 100 national leaders, including US President Barack Obama, will converge on Copenhagen for the final days of bargaining.

The talks, a landmark, are the boldest attempt in a 17-year odyssey to turn back the threat of climate change through global political consensus.

Deep rifts

If all goes well, the conference will yield an outline agreement that sets down pledges by major emitters of greenhouse gases for curbing their pollution.

It will also set down the principles of long-term financing, possibly worth hundreds of billions of dollars, to help wean poor countries off high-carbon technology and beef up their defenses against climate change.

Further negotiations would be needed over the next year to flesh out the agreement. Once agreed and ratified, the accord would take effect from 2013.

Two years of talks have taken place in the run-up to Copenhagen.

They have exposed deep rifts on the question of emissions burden-sharing.

Eyes on Obama

Reducing greenhouse gases carries an economic cost in energy efficiency and in shifting away from the oil, gas and coal, the cheap and plentiful ?fossil fuels? that are the mainstay of the world?s powers.

Developing countries, several of which are already big polluters, are refusing to budge unless rich nations slash their emissions by at least 40 percent by 2020 over 1990.

Among advanced economies, eyes have turned to the United States, which remained on the sidelines of the climate arena for eight years under George W. Bush.

Obama is now bulldozing away Bush?s policies and is steering legislation through Congress that would reduce US emissions by some 4 percent by 2020 compared to the 1990 benchmark.

This is just a fraction of what the European Union, Japan and others are demanding.

British challenge

But the US also argues that its campaign against carbon has to be viewed holistically?in other words, there are many other measures that should be taken into account when assessing its effort.

Obama?s hand at Copenhagen was strengthened when the US Environmental Protection Agency (EPA) labeled six greenhouse gases a dangerous pollutant that would be subject to government regulation, sidestepping Congress.

France?s climate ambassador Brice Lalonde said: ?This gives additional credibility to the US commitment.?

In Britain, Prime Minister Gordon Brown urged fellow Europeans to raise their bid on reducing greenhouse gas emissions to pressure the United States and others to offer more in the Copenhagen negotiations.

?We?ve got to make countries recognize that they have to be as ambitious as they say they want to be. It?s not enough to say ?I may do this, I might do this, possibly I?ll do this.? I want to create a situation in which the European Union is persuaded to go to 30 percent,? Brown was quoted as saying by Britain?s Guardian newspaper.

The EU has pledged to reduce greenhouse gas emissions by 20 percent by 2020, compared with 1990, and is considering raising that to 30 percent if other governments also aim high.

?Clearing undergrowth?

Delegates said the next few days would see different countries lay out their positions.

?It?s going to be an exercise in clearing the undergrowth over the next three or four days,? a senior delegate from a developed country told Agence France-Presse.

The leaders expected to attend the finale include Obama, Premier Wen Jiabao of China, Indian Prime Minister Manmohan Singh, Prime Minister Yukio Hatoyama of Japan, Brazil?s President Luiz Inacio Lula da Silva and the heads of the 27 countries of the EU.

To show good faith, rich countries are under pressure to kick in $10 billion a year in fast-track funding over the three years from 2010 to 2012.

The French minister for sustainable development, Jean-Louis Borloo, estimated that the most vulnerable countries would need $30 billion per year over the next 20 years to help reduce their exposure to likely droughts, flood, rising seas and storms.