Wednesday, March 15 2006 14:59 Hrs (IST) - World Time -

New York: In a worrying development, the greenhouse gases, which are associated with global warning, reached their highest ever recorded levels in 2004, mainly due to human activity, the United Nations has reported.

Scientists say unless the concentration is reversed, it could have devastating effect on the earth with droughts, heat waves, melting of polar ice leading to rise in sea level with highly adverse effects on coastal cities and small islands.

The UN meteorological agency reported yesterday that the concentration of carbon dioxide, the most abundant greenhouse gas in the planet atmosphere, rose by 1.8 parts per million to 377.1 ppm or 0.47 per cent in 2004 compared to previous year.

The 35 per cent in carbon dioxide since the dawn of the industrial age in the late 1700s has largely between due to emissions from combustion of fossil fuels.

Another greenhouse gas which reached record level is methane which is generated by farming and burning of fossil fuels like oil and coals.

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

Another major greenhouse gas nitrous oxide at 318.6 ppb has been rising by 0.8 ppb per year since 1988. Around one third of gas 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 carbon dioxide, 155 per cent for methane and 18 per cent for nitrous oxide, and increased over the previous decade by 19 ppm, 37 ppb and 8 ppb respectively in absolute amounts.