Greenhouse gases blamed for global warming and climate change have reached their highest ever levels in the atmosphere, the World Meteorological Organisation (WMO) said on Tuesday.
A bulletin from the United Nations agency said the gases - the main warming culprit carbon dioxide (CO2), methane and nitrous oxide - "all reached new highs in 2004."
WMO officials also indicated that a near record year-on-year rise in CO2 levels for 2005 recorded by US monitors - well above the average for the past 10 years - would not come as a major surprise.
"Global observations co-ordinated by WMO show that levels of carbon dioxide, the most abundant greenhouse gas in the atmosphere, continue to increase steadily and show no signs of levelling off," said WMO Secretary-General Michel Jarraud.
Carbon dioxide, which the WMO says accounts for 90 percent of warming over the past decade, is largely generated by human activity involving the burning of fossil fuels - including in industry, transport and domestic heating.
Scientists warn emissions must be slowed and reduced if the earth is to avoid climatic havoc with devastating heat waves, droughts, floods and rising sea-levels sinking low-lying island states and hitting seaboard cities like New York and London.
The UN's 1992 Kyoto Protocol, which came into force last year after a decade of wrangling, obliges major industrial nations to cut emissions while granting exemptions to developing countries like India and China.
But it was weakened by the withdrawal in 2001 of the United States, whose President George W. Bush said that working to meet its targets would seriously damage the US economy. He has also argued that warming is a natural, not man-made, process. In its first Greenhouse Gas Bulletin, to be an annual publication, the WMO said that in 2004 carbon dioxide levels in the atmosphere stood at 377.1 parts per million (ppm), 35 percent higher than in the pre-industrial age before 1750.
Methane, generated by intensive farming and landfills as well as the burning of fossil fuels like oil and coal and which accounts for around 20 percent of the greenhouse effect, has risen 155 percent in the modern age.
But its growth is slowing down, the WMO said, while nitrous oxide, which accounts for only 6 percent of the warming effect, is rising consistently.
The average annual increase in absolute amounts of CO2 in the atmosphere over the past decade has been 1.9 ppm, slightly higher than the 1.8 ppm of 2004, WMO environment division chief Leonard Barrie told a news conference.
Barrie said a finding by the UN National Oceanic and Atmospheric Administration, cited by the British Broadcasting Corporation, that carbon dioxide had grown last year by 2.6 ppm had to be viewed in perspective.
"It is important to take the long view. There can be fluctuations," he said. "The 2.6 ppm figure is within past experience. If it were to persist over several years, then we would have to start talking about what it means."
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