Turning Point for Fossil CO₂ Emissions Not Yet Reached

The tipping point in global CO₂ emissions has yet to be reached. According to the Global Carbon Budget 2024, released today at COP29 in Baku, Azerbaijan, emissions are forecast to reach around 37.4 billion tonnes of CO₂ this year – an increase of 0.8 per cent over the previous year. Between 2004 and 2013, annual increases averaged around two per cent. Although these figures indicate some progress towards the Paris climate targets, they are far from sufficient to keep global warming well below 2°C and achieve net-zero global emissions by 2050. To meet these goals, total emissions would need to decline by an average of 1.6 gigatonnes annually.

Published today in the journal Earth System Science Data, the report analyses emissions from fossil fuels, land-use changes (such as deforestation), and the complex interactions between the atmosphere, oceans, and land. It assesses the amount of carbon absorbed or released by plants, soils, and oceans and projects future carbon flows to calculate the remaining CO₂ budget critical for meeting global climate goals.

The Marine CO₂ Sink Remains Stable – But Challenges are Mounting

The report shows that the ocean continues to absorb around 26 per cent of global CO₂ emissions – a crucial function, yet one increasingly threatened by climate change. Higher water temperatures reduce the solubility of CO₂, thus diminishing the ocean’s capacity to act as a carbon sink. “Climate change has reduced the ocean’s CO₂ uptake capacity by around six per cent over the past decade,” explains Professor Dr Judith Hauck, environmental scientist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). The 2023 El Niño cycle temporarily boosted the ocean’s carbon uptake as less carbon-rich deep water reached the surface, but ongoing warming could weaken the ocean’s role as a carbon store in the long term.

CO₂ Monitoring in the North Atlantic – A Long-Term GEOMAR Project

The ocean sink – the amount of CO₂ the ocean absorbs and stores from the atmosphere – is estimated through measurements of CO₂ levels in the surface ocean and simulations with global ocean models. Scientists from GEOMAR Helmholtz Centre for Ocean Research have been contributing data through long-term monitoring in the North Atlantic. This ongoing dataset, collected by GEOMAR’s CO₂ research group for over 20 years, relies on sensors installed on the container ship MS ATLANTIC SAIL in cooperation with the shipping company Atlantic Container Lines (ACL). Operating between North America and Europe, the vessel continuously collects data on temperature, salinity, dissolved oxygen, and CO₂ in surface waters. This data is part of the Integrated Carbon Observation System (ICOS) European research infrastructure, providing annual data for the Global Carbon Budget.

The monitoring systems on board are maintained by Dr Tobias Steinhoff, chemical oceanographer and co-author of the Global Carbon Budget report. “Last year, we had to remove the instruments from the vessel to overhaul and upgrade them after a decade of continuous operation,” says Dr Steinhoff. “As a result, fewer data were available this year.”

SOCAT Data Platform: Key to Carbon Research and Climate Policy

Beyond GEOMAR’s own measurements, Dr Tobias Steinhoff is actively involved in the Surface Ocean CO₂ Atlas (SOCAT) platform, an international initiative that compiles and quality-checks surface CO₂ data. SOCAT data provides an early estimate of oceanic carbon uptake and also feeds into the Global Carbon Budget. Dr Steinhoff notes, “Our work in SOCAT strengthens the global understanding of oceanic CO₂ dynamics and highlights the ocean’s role as a CO₂ reservoir.”

About: The Global Carbon Project

The Global Carbon Project (GCP) is part of the international Future Earth research initiative. Its goal is to develop a comprehensive picture of the global carbon cycle, including its biophysical and human dimensions and their interactions. Climate scientists worldwide contribute to the annual report on the global carbon budget. The Global Carbon Budget 2024 is the 19th edition, with the first published in 2006. Each year, the report is published in the journal Earth System Science Data.

Numerous researchers from German-speaking countries contributed to the Global Carbon Budget 2024, including scientists from the Alfred Wegener Institute (Bremerhaven), ETH Zurich, GEOMAR (Kiel), Helmholtz Centre Hereon (Geesthacht), International Institute for Applied Systems Analysis (IIASA), Karlsruhe Institute of Technology, Leibniz Institute for Baltic Sea Research (Warnemünde), Ludwig Maximilian University (Munich), Max Planck Institute for Meteorology (Hamburg), Max Planck Institute for Biogeochemistry (Jena), Potsdam Institute for Climate Impact Research, and the universities of Bremen, Bern, and Hamburg.

Original Publication

Friedlingstein et al. (2024) Global Carbon Budget 2024. Earth System Science Data.

https://essd.copernicus.org/preprints/essd-2024-519