The volume of greenhouse gases in the Earth's atmosphere surged to a new record in 2023, with the World Meteorological Organisation (WMO) warning that this should "set alarm bells ringing among decision-makers".
Ahead of COP29 next month, the global climate summit organised each year by the United Nations (UN), latest data shows that carbon dioxide (CO2) is accumulating in the atmosphere faster than at any point in the existence of mankind, rising by 11.4% in the past two decades.
The WMO is a specialised agency within the UN that focuses on atmospheric science and meteorology. It published its annual Greenhouse Gas Bulletin ahead of COP29, which starts 11 November. The bulletin compiles data collected by its worldwide network of monitoring stations.
It outlines that globally-averaged surface concentration of CO2 reached 420.0 parts per million (ppm), methane 1,934 parts per billion (ppb) and nitrous oxide 336.9 ppb in 2023.
In addition, atmospheric CO2 rose more than in 2022, although less than for the three years before that. With an annual increase of 2.3 ppm, 2023 marked the 12th consecutive year with an increase greater than 2 ppm.
Forest fires and fossil fuels
The 2023 increase was driven by CO2 emissions from large forest fires, a possible reduction in carbon absorption by forests, and "stubbornly high" fossil fuel emissions from human activities.
The WMO noted that as long as emissions continue, greenhouse gases will continue to accumulate in the atmosphere, causing global temperature to rise.
"Another year. Another record. This should set alarm bells ringing among decision-makers," said WMO Secretary-General Celeste Saulo. "We are clearly off the 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."
Credit: Belga / Nicolas Maeterlinck
CO2 staying in the atmosphere
The Greenhouse Gas Bulletin reports on greenhouse gas concentrations, rather than on emission levels. Analysis of data shows that just under half of CO2 emissions remain in the atmosphere. Just over a quarter is absorbed by the ocean and just under 30% by land ecosystems. But this fluctuates considerably year-to-year because of natural phenomena like El Niño and La Niña.
For example during El Niño years, greenhouse gas levels tend to rise because drier vegetation and forest fires reduce the efficiency of land carbon sinks.
"In the near future, climate change itself could cause ecosystems to become larger sources of greenhouse gases. Wildfires could release more carbon into the atmosphere whilst the warmer ocean might absorb less CO2. Consequently, more CO2 could stay in the atmosphere to accelerate global warming. These climate feedbacks are critical concerns to human society," said WMO Deputy Secretary-General Ko Barrett.
