The globally-averaged surface concentration of CO2 reached an astronomical 420.0 parts per million (ppm), methane 1 934 parts per billion and nitrous oxide 336.9 parts per billion (ppb) in 2023.
These values are 151%, 265% and 125% of pre-industrial (before 1750) levels, according to the World Meteorological Organization’s (WMO) annual Greenhouse Gas Bulletin.
These are calculated on the basis of the long-term observations within the Global Atmosphere Watch network of monitoring stations.
Celeste Saulo, WMO Secretary-General, said “Another year. Another record. This should set alarm bells ringing among decision makers. We are clearly off track to meet the Paris Agreement goal of limiting global warming to well below 2°C and aiming for 1.5°C above pre-industrial levels.
These are more than just statistics. Every part per million and every fraction of a degree temperature increase has a real impact on our lives and our planet.”
The report has attributed the 2023 increase of CO2 in the atmosphere, to El Niño years. “Greenhouse gas levels tend to rise because drier vegetation and forest fires reduce the efficiency of land carbon sinks.”
The annual increase of CO2 to 2.3 parts per million (ppm), marked the 12th consecutive year of an increase greater than 2 ppm.
The WMO Greenhouse Gas Bulletin is one of WMO’s flagship publications released to inform the UN Climate Change conference, COP, and is now in its 20th issue.
During that time the CO2 level has increased by 11.4 % (42.9 ppm) above the level of 377.1 ppm recorded in 2004 by WMO’s Global Atmosphere Watch network of monitoring stations.
Analysis of data shows that just under half of CO2 emissions remain in the atmosphere.
Just over one quarter are absorbed by the ocean and just under 30% by land ecosystems, although there is considerable year-to-year variability in this because of naturally occurring phenomena like El Niño and La Niña.
The last time the Earth experienced a comparable concentration of CO₂ was 3-5 million years ago, when the temperature was 2-3°C warmer and sea level was 10-20 meters higher than now.