New Delhi: In 2023, not only did the planet experience its hottest year on record, but it also saw a dramatic spike in greenhouse gas (GHG) concentrations, locking in a trajectory of rising global temperatures for years to come, as highlighted in the World Meteorological Organization's (WMO) annual bulletin released on Monday. The report warns that carbon dioxide (CO₂) is accumulating in Earth’s atmosphere at a rate faster than any previous time in human history, surging by 11.4% over the past two decades. This increase in CO₂ levels recalls conditions 3–5 million years ago, when the Earth was 2–3 degrees Celsius warmer, and sea levels stood 10–20 meters higher than today.
“Another year, another record. Decision-makers should be on high alert,” said WMO Secretary-General Celeste Saulo, stressing that the goal of keeping global warming well below 2 degrees Celsius, with a target of 1.5 degrees above pre-industrial levels, appears increasingly elusive. She highlighted the tangible impacts of these rising levels, noting, “Every part per million, every fraction of a degree in temperature increase has real consequences for people and the planet.”
Released just ahead of the UN climate conference COP29, the bulletin reveals that in 2023, global surface concentrations of CO₂ reached 420 parts per million (ppm), with methane at 1,934 parts per billion (ppb) and nitrous oxide at 336.9 ppb. These levels are 151%, 265%, and 125% above pre-industrial (pre-1750) benchmarks, respectively, based on data from the Global Atmosphere Watch monitoring network.
The bulletin, which focuses on GHG concentrations rather than emissions, underscores that CO₂, responsible for 64% of the climate's warming effect, rose 11.4% above the 2004 level of 377.1 ppm. Fossil fuel combustion remains the primary driver, although yearly changes are influenced by phenomena like the El Niño-Southern Oscillation. In 2023, El Niño contributed to the spike in CO₂, as dry conditions and increased forest fires diminished the effectiveness of land-based carbon sinks.
Methane, a potent greenhouse gas with a lifespan of about a decade in the atmosphere, contributes around 16% of the warming impact of long-lived GHGs. Nitrous oxide, also a potent greenhouse gas and ozone-depleting substance, accounts for about 6% of radiative forcing, with the remaining 14% coming from other polluting gases.