Global fossil CO2 emissions have not yet reached their turning point

The Global Carbon Project shows that fossil CO₂ emissions will continue to rise in 2024. There is no sign of the rapid and substantial decline in emissions that would be needed to limit the impact of climate change.

Despite advances in clean and renewable energy, growing natural gas and oil consumption continues to drive global fossil fuel emissions higher: they are expected to increase by 0.8 percent in 2024 to reach 37.4 billion tons of CO₂. Emissions from coal will increase slightly by 0.2 percent. Despite the urgent need to reduce emissions in order to slow climate change, there appears to be no sign yet that the world has reached the peak of fossil CO₂ emissions. This is the conclusion of the latest report by the international Global Carbon Project, in which scientists from the Max Planck Institute for Biogeochemistry were also involved. With 4.2 billion tons projected from land-use change, particularly deforestation, total CO₂ emissions in 2024 are expected to be 41.6 billion tons – 1 billion tons more than in 2023.

Over the last 10 years, total CO₂ emissions have remained at a relatively steady plateau. Before that they had sharply increased by an average of 2 percent per year between 2004 and 2013. While this indicates progress towards the Paris climate targets, it is not nearly enough to stay well below 2°C and to bring global emissions towards net zero in the long term. For CO₂ emissions to reach net zero by 2050, total emissions would have to fall by an average of 1.6 gigatons annually. If emissions remain at current levels, the carbon budget that remains for us to limit global warming to 1.5 degrees Celsius (with a 50 percent probability) would be used up in this decade. The Global Carbon Project (GCP) projects global greenhouse gas emissions and their causes in its annual report.

Emissions from fossil sources

The fact that global fossil emissions are likely to rise in 2024 is due to the continued increase in emissions from gas and oil combustion, for example from international aviation and shipping. These are expected to increase by 7.8 percent in 2024, but still below pre-pandemic 2019 levels. At the same time, coal emissions will increase slightly by 0.2 percent. These account for about 41 percent of global emissions. The United States is projected to reduce its emissions by 0.6 percent in 2024 compared to 2023 (13 percent of global emissions). The European Union was able to reduce its emissions by 3.8 percent (7 percent of global emissions (EU27)). By contrast, emissions in China are expected to increase by 0.2 percent (32 percent of global emissions) and in India by 4.6 percent (8 percent of global emissions). Many countries seem to have succeeded to reduce or slow their fossil CO₂ emissions. In 22 countries, accounting for 23 percent of global fossil CO₂ emissions, these emissions decreased during the decade 2014-2023 while their economies grew. However, this noticeable trend towards decarbonization of energy systems is not enough overall to put global emissions on a downward path towards net zero.

The ocean as a CO₂ sink

In 2024, the ocean, along with plants and soils on land, continue to absorb about half of the anthropogenic CO₂ entering the atmosphere. However, climate change is increasingly affecting both sinks. Over the past decade, the oceans have absorbed an average of 10.5 gigatons per year, or 26 percent of total emissions. “Climate change has reduced the oceans' ability to absorb CO₂ by about 6 percent over the last decade,” says Prof. Judith Hauck, an environmental researcher at the Alfred Wegener Institute. “This is likely due to changes in winds that disrupt ocean circulation, and to the fact that the oceans are getting warmer and warmer, which reduces the solubility of CO₂.” According to the report, the preliminary estimate for the oceanic sink is 10.8 gigatonnes of CO₂ for 2024, slightly higher than the figure for 2023. “We were able to confirm last year's preliminary estimate for 2023 that the ocean sink had absorbed more CO₂ for the first time in three years.” The three-year stagnation was due to an exceptional triple La Niña event, which the GCP also described in its last report. “In 2023, there was a change to El Niño, during which the ocean sink is always somewhat stronger because less carbon-rich deep water rises to the surface.” The ocean sink is estimated from measurements of the CO₂ content in the surface ocean and simulations with global ocean models. According to the researchers, it is also worrying that the number of ocean observations is declining and is now back to the level of the early 2000s.

Double the pressure on terrestrial ecosystems

Climate change also affects the CO₂ sink on land: between 2014 and 2023, the land masses absorbed an average of 11.7 gigatons per year – or 29 percent of total CO₂ emissions. “However, less precipitation and ever-increasing warming have reduced the absorption capacity of terrestrial ecosystems by about 27 percent,” says Prof. Julia Pongratz, a geographer at LMU Munich. Ecosystems are also under massive pressure for another reason: changing and expanding land use. “Although global CO₂ emissions from land-use changes are expected to remain quite high at 4.2 gigatons in 2024, overall we see a downward trend here in recent decades.” This is mainly due to the fact that less deforestation is taking place and more land is being reforested. However, permanent deforestation over the last 10 years has still caused around 3.7 gigatons of CO_2, and only just under half of this is offset by reforestation. “The high emissions once again highlight the importance of completely halting deforestation in order to reduce emissions.”

Total global emissions and CO₂ increase in the atmosphere

Total CO2 emissions are projected to reach 41.6 gigatons of CO₂ in 2024, about 2 percent higher than in 2023. They have plateaued at a relatively steady level over the past decade, indicating progress in efforts to combat climate change, but not enough to put global emissions on the downward path needed to tackle climate change.
In 2024, the atmosphere is expected to have accumulated about 422.5 parts per million (ppm). This is 2.8 parts per million more CO₂ than in 2023 and more than double the pre-industrial level. The rise is due to CO₂ emissions, although the exact rise also depends on the reaction of the CO₂ sink on land and, to a lesser extent, in the ocean, depends on climatic conditions. Drought and fires have reduced the capacity of terrestrial ecosystems to absorb CO₂. Although the ocean was able to absorb more CO₂ during El Niño, it could not compensate for the decline on land, which is why more CO₂ remained in the atmosphere.

About the Global Carbon Project (GCP)

The GCP is an international research project of the Future Earth research initiative on global sustainability. It aims to develop a complete picture of the global carbon cycle, encompassing both the biophysical and human dimensions, as well as their interactions and feedbacks. Climate researchers from around the world are working on the report. The Global Carbon Budget 2024 is the 19th edition of the annual update, which began in 2006 and is published in the journal Earth System Science Data. Many researchers from German-speaking countries were involved in the report. They come from the Alfred Wegener Institute (AWI, Bremerhaven), ETH Zurich, the GEOMAR Helmholtz Centre for Ocean Research (Kiel), the Helmholtz Centre Hereon, the International Institute for Applied Systems Analysis (IIASA), the Karlsruhe Institute of Technology, the Leibniz Institute for Baltic Sea Research (Warnemünde), the Ludwig Maximilian University of Munich (LMU Munich), the Max Planck Institute for Meteorology (Hamburg), the Max Planck Institute for Biogeochemistry (Jena), the Potsdam Institute for Climate Impact Research and the Universities of Bremen, Bern and Hamburg. These researchers contributed ocean observations, model simulations of the ocean, land and atmosphere, and various analyses. At the Max Planck Institute for Biogeochemistry in Jena, these are Prof. Sönke Zaehle and Dr. Christian Rödenbeck.