Fossil fuel CO2 emissions will hit a new record in 2025, according to the largest carbon balance report

The Global Carbon Budget has been quantifying the balance between carbon dioxide emissions and the role of the ocean and terrestrial biosphere in reducing or exacerbating the total concentration of carbon in the atmosphere for 20 years. The study's conclusions are based on a robust, transparent methodology accepted by the scientific community. The report involved more than 130 researchers affiliated with dozens of scientific institutions in more than 20 countries.

This year, it notes that the amount of carbon absorbed by the terrestrial sink increased compared to last year. Likewise, the transition to renewable energy accelerated dramatically in China and India, slowing the growth of carbon dioxide emissions in those regions. However, the rate of global carbon emissions increased compared to previous years, especially in the United States and the European Union. This increase in global emissions is due to the persistent use and continued global dependence on fossil fuels of all kinds.

The data presented in this report confirm that the window of opportunity to limit global warming to less than 1.5°C above pre-industrial levels has closed. At the current rate, it is estimated that the remaining carbon budget, 170 GtCO₂, will be exhausted in four years. The GCB suggests that the actions taken so far in terms of emissions reduction and decarbonization have been insufficient. Even so, looking ahead to COP30, actions to reduce fossil fuel emissions must continue to take center stage. Emissions reduction should be the pillar that underpins discussions on adaptation and mitigation.

The methodology used in the Global Carbon Budget 2025 continues to maintain the characteristic robustness that identifies this international consortium. This work involves atmospheric observations, ocean and terrestrial carbon balances, as well as updated estimates of land use and fossil fuels, which provide a robust and consistent picture of the global carbon cycle. In this sense, its main contribution can be considered to lie in its temporal continuity and improved treatment of uncertainties, which allows for the comparison of trends with a high degree of interannual consistency. The analysis confirms that fossil emissions peaked in 2024 (37.4 Gt CO₂), with partial declines in the US and the EU offset by increases in India and China.

The study highlights once again that, if current emissions continue, the possibility of exceeding 1.5 °C in the next decade is extremely high, thus demonstrating the urgency of drastically cutting fossil fuel use before 2030. Among its limitations, the team itself acknowledges the enduring uncertainty in net terrestrial fluxes and the estimation of emissions from land-use changes.

Coinciding with COP30, these findings underscore the idea that national climate commitments remain disappointingly inadequate to stabilize the climate. The report, which is a recognized benchmark, should serve as essential scientific guidance to inspire much more ambitious mitigation policies and a palpable acceleration of the global energy transition.

Annual global carbon balance reports provide the most complete picture possible of the global carbon cycle in the climate system, both at the present time and showing temporal trends in its different components. The different components of the annual carbon cycle (emissions, accumulation in the atmosphere, sinks) are estimated using various methods that have different levels of uncertainty. While CO₂ accumulation in the atmosphere is measured directly at a collection of reference observatories, both emissions and sinks are estimated using various methodologies (models, statistics, observations, etc.) and data sources that also allow their uncertainty to be estimated.

CO₂ is the main greenhouse gas in the atmosphere and, therefore, its accumulation is largely responsible for the current anthropogenic climate change that manifests itself, in addition to global warming, in different ways such as an increase in the frequency and intensity of extreme weather and climate events, impacts on health and biodiversity, sea level rise, etc. A better understanding of the carbon cycle allows us to assess the extent to which our collective efforts are enabling us to slow down the climate change we are currently experiencing.

The conclusions of this study show us that we have practically reached the atmospheric CO₂ concentration that will not exceed the 1.5 °C increase established in the Paris Agreement. It also shows how, globally, emissions are not being reduced and the decarbonization of energy systems is not progressing—with clear regional differences—at the necessary pace. Studies such as this one allow us to monitor the results of the efforts and policies implemented to slow climate change, showing that greater commitment and ambition are needed to substantially reduce the constant increase in atmospheric CO₂ concentration, which is the cause of current climate change.