The gloomy picture painted by the UN Climate Change Convention (UNCCC) Executive Secretary Joke Waller-Hunter came ahead of a fresh effort to breathe life into the sickly Kyoto Protocol.
In a statement issued in Bonn on Wednesday, Waller-Hunter said: "The fact that 2003 is on track to be one of the warmest years on record should be a warning we must all take seriously."
She said there's growing evidence that many governments have been inspired by the Climate Change Convention and its Kyoto Protocol to strengthen action at the national level, but more needs to be done to stop the increase in greenhouse gas concentrations.
Waller-Hunter gave no figures for global warming in 2003, but anecdotal evidence and scientific data from several countries suggest it will be the hottest year since record-keeping began.
In October, the French national weather service said that unless weather was exceptionally cold until the end of the year, the mean national temperature in 2003 would be "nearly half a degree (Celsius)" (0.9 F) higher than the average from 1900-2002.
The 188 parties to the UNCCC meet in Milan from December 1-12 to assess progress in addressing climate change.
Topping the agenda will be the future of the Kyoto Protocol, an offspring of the UNCCC that deals specifically with the emissions of carbon pollution blamed for global warming.
The Protocol was badly hit when the United States, the world's biggest polluter, pulled out of it in March 2001 in one of President George Bush's first acts after taking office.
Kyoto's rulebook was laboriously completed but under its complex ratification arithmetic, the deal cannot enter into force until it has been ratified by Russia.
Waller-Hunter said that "national communications" to the UNCCC showed that despite efforts to address greenhouse gas emissions, the rich industrialised world was still increasing its pollution.
"The combined emissions of Europe, Japan, the US and other industrialised countries could grow by eight percent from 2000 to 2010 (or to about 17% over 1990 levels) despite domestic measures currently in place to limit them," she said.
The Milan meeting will gather some 4000 delegates. It includes a ministerial-level gathering on December 10-11 that will be addressed by Italian Prime Minister Silvio Berlusconi.