Effect of greenhouse gases up 20% since 1990

The effect of greenhouse gases in the Earth's atmosphere has increased 20 percent since 1990, showed the Annual Greenhouse Gas Index (AGGI) released Tuesday.

The index was set to a reading of 1 as of 1990, and it is now up to 1.20, indicating a 20 percent increase of carbon dioxide, methane, nitrous oxide and chlorofluorocarbons (CFCs) in the air, said the Climate Monitoring and Diagnostics Laboratory (CMDL), of the US National Oceanic and Atmospheric Administration.

The greenhouse gases, mostly from industrial activities, can help trap solar heat in the air, leading to global warming.

"The AGGI will serve as a gauge of success or failure of future efforts to curb carbon dioxide and other greenhouse gas increases in the atmosphere both by natural and human-engineered processes,"said David Hofmann, CMDL director.

In the current reading, for every million air molecules there are about 375 carbon dioxide molecules, two methane molecules and less than one nitrous oxide molecule. The CFCs, a key factor responsible for the depletion of the protective ozone layer, make up less than one molecule in a billion in the atmosphere.

The greenhouse gases produce an effect known as radiative forcing, which is a shift in the balance between solar radiation coming into the atmosphere and Earth's radiation going out.