The United Nations weather agency says atmospheric levels of the three main greenhouse gases all reached new record highs in 2021.

The World Meteorological Organization, WMO, analyzed observation data collected from weather agencies and research institutions across the world.

The WMO's annual report released on Wednesday says that global carbon dioxide concentrations were 415.7 parts per million, or ppm, methane at 1,908 parts per billion, or ppb, and nitrous oxide at 334.5 ppb.

All of those figures were higher than those recorded in the previous year and the highest since 1984 when observations began across the world.

Carbon dioxide emissions from the combustion of fossil fuels declined by 5.4 percent between 2019 and 2020. But those emissions rose by 4.9 percent from the following year through 2021, as human activities resumed after coronavirus lockdowns.

The report says the annual increase of atmospheric methane last year was the largest since the start of measurements.

Causes are still being investigated by scientists, but there may be a possible link with La Nina events which are associated with increased precipitation in the tropics.

The report points out a possibility that if it gets warmer, organic material decomposes faster in water, which leads to methane emissions.

Japan's Meteorological Agency, which has taken part in data analysis, says that global efforts to reduce greenhouse gas emissions have not caught up with the actual volumes of outputs.

The agency says that countries need to take necessary measures more quickly to reduce disaster risks resulting from abnormal weather events.