GENEVA—A report by the UN weather agency has found that greenhouse gas levels in the atmosphere reached record levels in 2009.

The World Meteorological Organization says efforts to reduce emissions of carbon dioxide, methane and nitrous oxide haven’t diminished the atmospheric concentration of these gases widely blamed for stoking global warming.

The Geneva-based agency says concentrations of carbon dioxide rose in 2009 by 1.6 parts per million, to 386.8 parts per million.

The pre-industrial carbon dioxide average was about 280 parts per million. The higher the concentration of greenhouse gases, the more heat is trapped in the atmosphere.

WMO said Wednesday that the recent economic slowdown hadn’t significantly affected emissions of greenhouse gases.