Two of the most important Greenhouse gases in the Earth’s atmosphere reached a record high in 2006, and measurements show that one – carbon dioxide – is playing an increasingly important role in global warming, the U.N. weather agency said Friday.

The global average concentrations of carbon dioxide, or CO2, and nitrous oxide, or N2O, in the atmosphere were higher than ever in measurements coordinated by the World Meteorological Organization, said Geir Braathen, a climate specialist at the Geneva-based agency.

Methane, the third of the three important greenhouse gases, remained stable between 2005 and 2006, he said.

Braathen said measurements show that CO2 is contributing more to global warming than previously.

CO2 contributed 87 percent to the warming effect over the last decade, but in the last five years alone, its contribution was 91 percent, Braathen said.