The UN said today that the concentration of carbon dioxide (CO2) in the atmosphere has hit a new high. <br/><br/>It warned that drastic action is needed to achieve targets set by the Paris climate agreement. <br/><br/>The World Meteorological Organization said, concentrations of carbon dioxide in the atmosphere surged at a record-breaking speed in 2016. <br/><br/>It said, 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.<br/><br/>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.<br/><br/>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.