2016 saw a record surge in CO2 in the atmosphere.
3.3ppm increase in 2016 is a new record increase in one year.
CO2 in the atmosphere hit 403.3ppm
2016 saw average concentrations of CO2 hit 403.3 parts per million, up from 400ppm in 2015.
"It is the largest increase we have ever seen in the 30 years we have had this network," Dr Oksana Tarasova, chief of WMO's global atmosphere watch programme, told BBC News.
"The largest increase was in the previous El Niño, in 1997-1998 and it was 2.7ppm and now it is 3.3ppm, it is also 50% higher than the average of the last ten years."