Earth's atmosphere experienced an unprecedented increase in carbon dioxide (CO₂) in 2024, a gas that contributes to the warming of our planet.
Scientists measured an increase of 3.5 parts per million (ppm) of CO₂ in the air between 2023 and 2024, representing the largest annual rise since modern records began in 1957. This total concentration now reaches approximately 423.9 ppm, which is 152% higher than pre-industrial levels. The main causes include humanity's persistent burning of fossil fuels, a resurgence of forest fires, and a decrease in absorption by natural carbon sinks like oceans and forests. These sinks, which usually capture a portion of the CO₂, appear to be less effective, worsening the situation.
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CO₂ is the main greenhouse gas responsible for climate change, accounting for about 80% of the warming effect since 1990, according to the U.S. National Oceanic and Atmospheric Administration. By trapping solar heat, it raises global average temperatures, which alters weather patterns, causes sea levels to rise, and threatens the food and economic security of billions of people. Ko Barrett, Deputy Secretary-General of the World Meteorological Organization, emphasized that reducing emissions is vital for climate stability and the well-being of communities.
Greenhouse gas emissions vary considerably by country. In 2024, China was the largest emitter, responsible for approximately 29.2% of global emissions, followed by the United States at 11.1% and India at 8.2%. While China and India increased their emissions compared to 2023, those from the United States remained stable. Yet, initiatives like the Paris Agreement aim to limit these emissions, but political actions, such as the repeated U.S. withdrawal from this agreement, complicate global efforts. The *Climate Action Tracker* project estimates that neither China nor the United States is doing enough, rating them as "highly insufficient" and "critically insufficient" respectively.
Besides CO₂, other gases like methane (CH₄) and nitrous oxide (N₂O) also reached record levels in 2024, with increases of 166% and 25% compared to pre-industrial times. These increases are partly explained by positive feedback loops: warming reduces the effectiveness of carbon sinks, such as oceans which absorb less CO₂ in warmer waters, thereby accelerating climate change. Oksana Tarasova, an expert at the World Meteorological Organization, stressed the need to strengthen monitoring to better understand these mechanisms.
Faced with this urgency, the report's recommendations include drastically reducing emissions and improving monitoring systems. Solutions involve an energy transition to renewable sources and better management of natural resources. Without rapid action, impacts on ecosystems and human societies could intensify, making each year more critical for the planet's future.
Natural carbon sinks
Carbon sinks are natural reservoirs, such as oceans and forests, that absorb and store carbon dioxide from the atmosphere. This process helps regulate the climate by reducing the amount of CO₂ available to trap heat. For example, trees capture CO₂ during photosynthesis, while oceans dissolve it in water.
However, the effectiveness of these sinks is threatened by climate change. As temperatures rise, oceans absorb less CO₂ because gases dissolve less effectively in warm water. Furthermore, deforestation and ecosystem degradation reduce forests' capacity to act as carbon sponges.
This decrease creates a positive feedback loop: less CO₂ is absorbed, which accelerates warming, which in turn further weakens the sinks. Studies show that if this trend continues, up to 30% of natural absorption could be compromised by the end of the century.
To counter this, reforestation initiatives and marine area protection are essential. By restoring these ecosystems, we can boost their capacity to capture carbon, offering a natural solution to mitigate the effects of climate change.