1127. CO2 Concentration Increased by 11.4% in Just 20 Years

On October 28, the World Meteorological Organization (WMO) released its Greenhouse Gas Bulletin, which provides 2023 observations and the latest analysis of long-lived greenhouse gases (CO2, CH4, N2O) that significantly impact on global warming.

From 2022 to 2023, the annual mean CO2 in the global surface atmosphere increased by 2.3 ppm. This increase marked the twelfth consecutive year with an increase greater than 2 ppm, continuing an already significant trend. CO2 is accumulating in the atmosphere faster than at any time during human existence. The current atmospheric CO2 level is already 51% above that of the pre-industrial (before 1750) era.

In 2023, the within-year increase of atmospheric CO2 was larger than the decadal average and was the second largest within-year growth in the past decade. This may be a result of enhanced fire emissions and reduced net terrestrial carbon sinks. While the long-term CO2 increase caused by fossil fuel combustion is monotonic, the CO2 growth rate varies from year to year, with the variability mostly driven by the terrestrial biosphere exchange of CO2.

2023 was an exceptionally warm year; global temperature across the land and the oceans was the highest in records dating as far back as 1850. Extreme heat is a stress factor for many terrestrial systems and can cause reduced carbon uptake by plants.

Below are the key messages: 

• CO2 concentrations have increased 11.4 % in just 20 years.
• Long lifetime of CO2 in atmosphere locks in future temperature increase.
• El Niño and vegetation fires fueled the surge in the later part of 2023.
• Effectiveness of carbon sinks like forests cannot be taken for granted.
• Improved understanding of carbon-climate feedbacks is needed.

Contributor: IIYAMA Miyuki, Information Program