Green-house gases level alarming

The concentration of major green-house gases (carbon dioxide, methane and nitrous oxide) in the atmosphere has reached its highest-ever recorded level.

According to the 2004 annual green-house gases bulletin released by the World Meteorological Organisation (WMO) in Geneva, carbon dioxide content in the atmosphere has peaked at 377.1 parts per million (ppm). This is 19 ppm higher than its average level in the previous decade.

Concentration of methane was recorded at 1,783 parts per billion (ppb), up 37 ppb from the previous decade, and that of nitrous oxide at 318.6 ppb, about 8 ppb higher than in the last decade.

Compared to the pre-industrial period of the late 1,700s, the levels of carbon dioxide, methane and nitrous oxide are higher by 35 per cent, 155 per cent and 18 per cent respectively.

The 2005 green-house gases bulletin is scheduled to be issued by the WMO in November. Significantly, though methane concentration has increased the maximum in percentage terms in the past, it is now tending to reach a plateau. This is evident from virtually no increase in its concentration in 2004 and less than 5 ppb annual rise recorded since 1999.

Human activity such as fossil fuel exploitation, paddy cultivation, biomass burning, landfills and livestock like ruminant animals, account for about 60 per cent of the atmospheric methane. The remaining 40 per cent is due largely to natural processes like methane emission from wetlands and that generated by termites.

But the content of carbon dioxide, the most abundant green-house gas, is continuing to rise unabated.

There also are no signs of its reaching the plateau soon.

The estimated 35 per cent increase in carbon dioxide since the late 1970s is attributed largely to emissions from the combustion of fossil fuels. In 2004, carbon dioxide content of the environment rose by 1.8 ppm or 0.47 per cent over the previous year's level.

Similarly, the nitrous oxide level in atmosphere has been going up steadily by about 0.8 ppb a year since 1988, according to the WMO report. Around one-thirds of nitrous oxide discharged into the air is a result of human activities, such as fuel, combustion, biomass burning, fertiliser use and some industrial processes.

The WMO prepares the green-house gase bulletin in cooperation with the World Data Centre for Green-house Gases (WDCGG), located in Japan Meteorological Agency, and the Global Atmosphere Watch Scientific Advisory Group for Green-house Gases.

The WDCGG bases its data on observations collected from 44 WMO members and the Global atmosphere watch group is assisted by the national oceanic and atmospheric administration's earth system research laboratory in this effort.