Carbon dioxide (CO₂) is the most important greenhouse gas (GHG).

In 2023, the worldwide concentration of CO₂ showed no sign of decreasing. Despite attempts at reducing CO₂ emissions, the concentration of CO₂ in the atmosphere rose again in 2023.

As the figure shows, the growth rate of CO₂ is still increasing.

The rate at which CO₂ has increased is shown below.

The figure comes from the World Meteorological Organization, which just released its 2023 update on the State of Greenhouse Gases in 2023.

Last year was the 12th consecutive year with a growth greater than 2 parts per million of atmospheric carbon dioxide.

The decades-long increase in CO₂ levels is a direct result of the growth in fossil fuel emissions in the 2010s and 2020s.

The variation in the growth rate of CO₂ is mostly due to the El Niño, which impacts photosynthesis rates. The Earth transitioned from a three-year-long La Niña to an El Niño — i.e., from the cold phase to the warm phase, which caused the record-high global average temperature.

The WMO report concluded that CO₂ is accumulating in the atmosphere faster than at any time during human existence. The current level of CO₂ level is 51% greater than the pre-industrial era (before 1750).

Methane: Carbon dioxide accounts for 66% of global warming. The second-largest contributor is methane (CH₄), which accounts for 16% of global warming. The methane concentration charts show similar growth rates to CO₂.

Carbon monoxide: The report also noted that 2023 experienced the largest increase in carbon monoxide (CO) in the past two decades. The growth in CO is attributed to the rise in wildfires.

In 2023, Canada experienced its worst wildfire season on record, and emitted amounts of CO comparable to the annual emissions from some large nations.

From August to October, Australia experienced its driest three-month period on record, with severe bushfires.

Plant stress: 2023 was an exceptionally warm year; global temperatures were the highest since 1850.

Extreme heat stresses plants because it reduces their carbon uptake. In 2023, the ecosystem took up about 28% less CO₂ than in 2021–2022.

Consequences: The WMO report concluded that wildfires could release even more CO₂ into the atmosphere and the warmer oceans and stressed plants could absorb less CO₂. As a consequence, even more CO₂ could remain in the atmosphere.

The world is facing accelerating global warming and ocean acidification. These data should be a major concern to everyone.

Roger Warburton, Ph.D., is a Newport, R.I., resident. He can be reached at [email protected].

Notes: “Green House Gas Bulletin,” World Meteorological Organization, No. 20, 28 October 2024: “The State of Greenhouse Gases in the Atmosphere Based on Global Observations through 2023.”