30 October 2017
Concentrations of CO2 in the Earth's atmosphere surged to a record high in 2016, according to the World Meteorological Organization (WMO).
Last year's increase was 50% higher than the average of the past 10 years.
Researchers say a combination of human activities and the El Niño weather phenomenon drove CO2 to a level not seen in 800,000 years.
Scientists say this risks making global temperature targets largely unattainable.