The amount of greenhouse gases in the atmosphere reached a new record high in 2011, the World Meteorological Organization (WMO) said Tuesday.

Total radioactive forcing, or the warming effect on the climate, of all long-lived greenhouse gases was the carbon dioxide (CO2) equivalent of 473 parts per million last year, a 30 percent increase over that in 1990, said the WMO 2011 Greenhouse Gas Bulletin.

CO2, which is the single most important greenhouse gas emitted by human activities, accounted for about 80 percent of the increase; and the amount of CO2 in the atmosphere reached 390.0 parts per million in 2011, or 140 percent of the pre-industrial level, according to the bulletin.

It said that since the start of the industrial era in 1750, about 375 billion tonnes of carbon have been released into the atmosphere as CO2. About half of this carbon dioxide remains in the atmosphere, with the rest being absorbed by the oceans and terrestrial biosphere.

Michel Jarraud, Secretary-General of WMO, said future emissions will only compound the situation and it's not certain whether the carbon sinks will continue to absorb CO2 at the same level in the future.

"There are many additional interactions between greenhouse gases, Earth's biosphere and oceans, and we need to boost our monitoring capability and scientific knowledge in order to better understand these," he said.

The WMO bulletin reports on atmospheric concentrations of greenhouse gases, which represent what remains in the atmosphere after the complex system of interactions between the atmosphere, biosphere and the oceans.