The concentration of carbon dioxide (CO2) in the atmosphere has hit a new high.

The UN said that drastic action is needed to achieve targets set by the Paris climate agreement.

The World Meteorological Organization said concentrations of carbon dioxide in the atmosphere surged at a record-breaking speed in 2016," with rates hitting 403.3 parts per million in 2016.

"Globally averaged concentrations of CO2 reached 403.3 parts per million in 2016, up from 400.00 ppm in 2015 because of a combination of human activities and a strong El Nino event.

The Greenhouse Gas Bulletin, the UN weather agency's annual flagship report, tracks the continent of dangerous gasses in atmosphere in the post-industrial era (since 1750).

The report also said that the last time Earth experienced similar CO2 concentration rates was three to five million years ago, when the sea level was up to 20 metres (66 feet) higher than now.

Without rapid cuts in CO2 and other greenhouse gas emissions, we will be heading for dangerous temperature increases by the end of this century, well above the target set by the Paris climate change agreement," WMO chief Petteri Taalas said in a statement.

The historic agreement approved by 196 countries two years ago is facing renewed pressure following US President Donald Trump's decision to quit the accord. But nations are set to press on with the task of implementing it at climate talks in Bonn next week.