The World Meteorological Organization´s Greenhouse Gas Bulletin, published March 14, examined concentrations of carbon dioxide, methane and nitrous oxide in the planet´s atmosphere.

The values supersede those of pre-industrialized times by 35 percent, 155 percent and 18 percent respectively, according to the U.N. organization.

"Global observations coordinated 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 leveling off," said WMO Secretary-General Michel Jarraud.

The 35 percent rise in carbon dioxide since the late 1700s has largely been generated by emissions from the combustion of fossil fuels, according to the WMO.

In contrast, atmospheric levels of methane apparently have reached a plateau, with no increase in 2004. Human activities, including fuel use, biomass burning, landfills and farm animal operations, are responsible for 60 percent of the atmospheric methane, according to WMO estimates.

Nitrous oxide in the atmosphere has been steadily rising since 1988, and about a third of the discharges into the air result from human activities such as fuel combustion, biomass burning, fertilizer use and some industrial processes, according to the U.N. agency.

The March 14 report is the first of what the WMO plans will be annual reports. The organization plans to release the 2005 bulletin in November 2006.