Global concentrations of carbon dioxide in Earth’s atmosphere surpassed 400 parts per million for a monthly average this past spring, breaching a symbolic barrier set by climate scientists and policy makers, according to a report released Monday.

Concentrations of other greenhouse gases produced from human activities, such as methane and nitrous oxide, also reached records in 2014, the World Meteorological Organization announced in its annual Greenhouse Gas Bulletin. The report is one of several measurements made by different climate agencies to address the state of greenhouse gases in advance of the Paris Climate Summit.

“This evidence shows us that the concentrations are increasing, and they are increasing with increasing rates,” said Oksana Tarasova, chief of the W.M.O.’s Atmospheric Environment Research Division. “This calls for urgent and very strong actions to limit the emission of those greenhouse gasses.”

In 2014, the average global atmospheric carbon dioxide level rose to 397.7 parts per million, substantially higher than the 278 parts per million floating in the atmosphere during preindustrial time, or before 1750. The researchers reported that the annual average is expected to pass 400 parts per million in 2016.