Rising CO2 levels, Pg23.

Key Highlights:

• The global average CO2 concentration reached 423.9 parts per million (ppm) in 2024, a 3.5 ppm increase from 2023.
• This year-on-year increase is the highest since measurements began in 1957, surpassing the 2011-2020 decade average.
• 2024 was the warmest year on record, exceeding pre-industrial temperatures by 1.55 degrees Celsius.
• The rising CO2 concentrations highlight the failure of the Paris Agreement to significantly slow down global emissions.

Detailed Insights:

• CO2 concentrations have consistently risen over the past 40 years, with the rate of increase tripling from 0.8 ppm per year in the 1960s to 2.4 ppm per year between 2011 and 2020.
• The current CO2 concentration is 152% higher than pre-industrial levels of 278.3 ppm, with man-made processes contributing significantly to this increase.
• While CO2 is less potent than methane (CH4) and nitrous oxide (N2O) in trapping heat, it remains in the atmosphere for a longer time, contributing to 66% of warming since pre-industrial times.
• The WMO report suggests that variabilities in the natural CO2 loop, such as reduced absorption by oceans and land sinks, and increased forest fires, contributed to the 3.5 ppm increase.
• Higher temperatures decrease the CO2 absorption capacity of oceans, while extreme droughts reduce the absorption capacity of trees and grasslands, exacerbating the CO2 imbalance.
• Concentrations of CH4 and N2O also increased in 2024, reaching 1,942 ppb and 338 ppb respectively, with CH4 contributing 16% and N2O contributing 6% to warming since pre-industrial times.
• Despite efforts to control emissions, global emissions continue to rise, making it likely that the 2030 emission reduction targets will be missed.

Key Concepts Involved:

• CO2 (Carbon Dioxide): A primary greenhouse gas produced by natural and man-made processes.
• Greenhouse Gases (GHGs): Gases that trap heat in the atmosphere, contributing to global warming.
• Paris Agreement: An international agreement to combat climate change by limiting global warming.
• Pre-industrial Levels: The levels of greenhouse gases before the start of the Industrial Revolution.