By The Associated Press

The World Meteorological Organization says heat-trapping gases in Earth's atmosphere are growing faster than before, surging permanently beyond a troubling milestone.

The United Nations agency says global carbon dioxide levels, which first reached 400 parts per million last year, are likely to stay above that symbolic 400 milestone all year and for generations to come.

Carbon dioxide levels overall rise because of the burning of fossil fuels and were goosed by the El Nino weather phenomenon. They also fluctuate, seasonally peaking in May and dipping in September. Last month's average level at a key Hawaii monitoring station was 401 parts per million, up from 313 in 1958.

Methane and other heat-trapping gases are also spiking. The WMO issues its annual greenhouse gas bulletin, using public data, before international climate talks.