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Greenhouse gases reach highest level ever recorded, UN agency reports

Greenhouse gases reach highest level ever recorded, UN agency reports

Globally averaged concentrations of carbon dioxide (CO2), the most abundant greenhouse gas in the planet’s atmosphere, as well as of methane (CH4) and nitrous oxide (N2O), reached their highest ever-recorded levels in 2004, mainly due to human activity, the United Nations meteorological agency announced today.

CO2 increased by 1.8 parts per million (ppm) to 377.1 ppm, or 0.47 per cent compared with 2003, the World Meteorological Organization (WMO) reported in its first annual Greenhouse Gas Bulletin. The 35 per cent rise in CO2 since the dawn of the industrial age in the late 1700s has largely been generated by emissions from the combustion of fossil fuels.

“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 levelling off,” said Michel Jarraud, Secretary-General of the Geneva-based agency.

In contrast, atmospheric levels of methane, at 1783 parts per billion (ppb), have shown signs of reaching a plateau with virtually no rise in 2004 and changing by less than 5 ppb per year since 1999.

Human activity such as fossil fuel exploitation, rice agriculture, biomass burning, landfills and ruminant farm animals account for some 60 per cent of atmospheric CH4, with natural processes including those produced by wetlands and termites responsible for the remaining 40 per cent.

Nitrous oxide, at 318.6 ppb, has been steadily rising by about 0.8 ppb per year since 1988. Around one third of N2O discharged into the air is a result of human activities such as fuel combustion, biomass burning, fertilizer use and some industrial processes.

The rates supersede those of pre-industrial times by 35 per cent for CO2, 155 per cent for CH4 and 18 per cent for N2O, and increased over the previous decade by 19 ppm, 37 ppb and 8 ppb respectively in absolute amounts.

WMO plans to release the 2005 bulletin in November 2006.