This was the twelfth consecutive year that carbon dioxide levels rose by more than 2 parts per million
The atmosphere is holding its breath — and it’s not good news. Data from the National Oceanic and Atmospheric Administration (NOAA) has revealed that global carbon dioxide levels reached a record high in 2023. This surge places us in a precarious position, mirroring atmospheric conditions from the Pliocene epoch, a period roughly 4.3 million years ago.
The Pliocene epoch was a time of significant environmental change. While not as hot as some periods in Earth’s history, global temperatures were several degrees higher than today and sea levels were significantly elevated. These changes were likely driven by natural fluctuations in Earth’s orbit and tilt, but the current surge is demonstrably caused by human activities.
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During that geological period, sea levels were approximately 23 metres higher than today, and the average temperature was 7 degrees Fahrenheit higher than in pre-industrial times.
Carbon dioxide (CO2) concentrations at the global surface increased by 2.8 parts per million (ppm) in 2023, reaching 419.3 ppm from 2022.
This was the twelfth consecutive year that carbon dioxide levels rose by more than 2 ppm. This trend, according to NOAA’s monitoring records, was not observed before 2014. Further, the 2023 atmospheric CO2 levels are now more than 50 per cent higher than those found in the pre-industrial era.
“The 2023 increase was the third-largest in the last decade and is likely a result of an ongoing increase of fossil fuel carbon dioxide emissions, coupled with increased fire emissions possibly as a result of the transition from La Nina to El Nino,” Xin Lan, a Cooperative Institute for Research in Environmental Sciences scientist, said in a statement.
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El Nino and La Nina are the warm and cool phases of a recurring climate pattern across the tropical Pacific called the El Nino-Southern Oscillation, or “ENSO”. The world transitioned from a three-year run of El Nino to La Nina in 2023. As per NOAA, the odds of La Nina developing in June-August 2024 are 55 per cent.
The NOAA analysis also found record high levels of another greenhouse gas: Methane. Despite being less abundant than CO2, it is more potent at trapping heat in the atmosphere.
Methane levels went up to an average of 1922.6 parts per billion (ppb) — a 10.9 ppb jump over 2022. Methane levels in the atmosphere are now more than 160 per cent higher than their pre-industrial level.
The single-year increase in 2023, however, is less than the annual growth rates seen in 2020 (15.2 ppb), 2021 (18 ppb), and 2022 (13.2 ppb).
The year 2023 marked the fifth-highest since 2007. Methane levels first rose in the 1980s. It nearly stabilised in the early 2000s before rapidly increasing again in 2007.
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This trend continues. More than 85 per cent of the increase from 2006 to 2021 was due to increased microbial emissions generated by livestock, agriculture, human and agricultural waste, wetlands and other aquatic sources, according to a 2022 study and additional NOAA research in 2023. The rest could be coming from fossil fuel emissions.
“In addition to the record high methane growth in 2020-2022, we also observed sharp changes in the isotope composition of the methane that indicate an even more dominant role of microbial emission increase,” said Lan, adding that the exact causes of the recent increase are not yet fully known.
The researchers now plan to study whether climate change is causing wetlands to release methane emissions in a loop in response to warming.
As for nitrous oxide, the third-most significant human-caused greenhouse gas, the levels climbed by 1 ppb to 336.7 ppb in 2023. This increase in recent decades is being traced back to the use of nitrogen fertiliser and manure from the expansion and intensification of agriculture. Nitrous oxide concentrations are 25 per cent higher than the pre-industrial level of 270 ppb.
A December 2023 analysis from Global Carbon Project (GCP), an international consortium of scientists from more than 90 institutions, reported an increase in overall CO2 emissions by 1.1 per cent compared to 2022 levels and 1.5 per cent compared to pre-pandemic levels.
NOAA has published its first estimate of the growth in global-average CO₂ concentration for 2023 at +2.81 ppm. The global carbon project’s forecast was 2.4 ppm, Robbie Andrew, a senior researcher in the Climate Mitigation group at the Center for International Climate and Environmental Research, wrote on X.
Read more: 2023 in a blink: What were emission footprints of transport, manufacturing sectors this year
An April 2024 analysis published in journal Nature Reviews Earth & Environment reported that global CO2 emissions in 2023 increased by only 0.1 per cent relative to 2022, following a 5.4 per cent and 1.9 per cent jump in 2021 and 2022, respectively.
These 2023 emissions, according to the paper, used up 10–66.7 per cent of the remaining carbon budget to limit warming to 1.5°C. The remaining carbon budget is the net amount of CO2 humans can still emit to stay within the global warming limit.
The world might use up the permissible emissions within 0.5–6 years, with a 67 per cent likelihood, the paper highlighted. India, it found, overtook the European Union to become the third highest emitter globally.
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