Every year, an international team of scientists adds up how much carbon dioxide humanity releases and tracks where it ends up. The Global Carbon Budget 2025, released on November 13, 2025 during the COP30 climate summit, is the latest full edition we could verify at the time of writing. Its headline: emissions from fossil fuels reached another record high.
What are CO2 emissions?
Carbon dioxide (CO2) is released when fossil fuels such as coal, oil and natural gas are burned, and when land use changes, for example when forests are cleared. The gas traps heat and is central to the greenhouse effect, which is why rising emissions drive climate change. Emissions are a yearly flow measured in tonnes. That is different from the concentration of CO2 in the air, which is a running total measured in parts per million (ppm).
CO2 emissions vs. CO2 concentration
The two are easy to confuse. Emissions are what is added in a given year. Concentration is what has built up in the atmosphere over time, because CO2 is removed only gradually by natural sinks. That is why concentration keeps rising even in a year when emissions grow slowly or dip slightly: as long as more CO2 is added than the sinks remove, the total in the air goes up. The 2025 figure of 425.7 ppm is a concentration, while the 38.1 billion tonnes is an emission.
How much CO2 did the world emit in 2025?
The Global Carbon Project projects the following for 2025:
- Fossil CO2 emissions: 38.1 billion tonnes, up 1.1 percent and described as a record high
- Land-use change emissions: 4.1 billion tonnes
- Total CO2 emissions: slightly lower than last year, because land-use emissions are lower
- Atmospheric CO2: 425.7 ppm, which is 52 percent above pre-industrial levels
These are projections for 2025, not final measurements, and the report was released as a preprint in the journal Earth System Science Data. Land-use and sink estimates also depend on models, which adds uncertainty.
Which fuels and countries drove the change?
The rise was driven by all fuel types. Projected changes in fossil CO2 emissions for 2025 were:
- By fuel: coal up 0.8 percent, oil up 1 percent and natural gas up 1.3 percent
- By country or region: China up 0.4 percent, the United States up 1.9 percent, India up 1.4 percent, the European Union up 0.4 percent, Japan down 2.2 percent, and the rest of the world up 1.1 percent
- Transport: international aviation up 6.8 percent, exceeding pre-COVID levels, while international shipping was flat
Where does the CO2 go?
Not all emitted CO2 stays in the air. Land and oceans act as a carbon sink by absorbing a large share. The report finds the land sink recovered to its pre-El Nino level in 2025 after the 2023 to 2024 El Nino ended. Yet climate change is weakening both land and ocean sinks, and a companion paper in Nature attributes about 8 percent of the rise in atmospheric CO2 since 1960 to that weakening. If sinks weaken, a larger share of each year’s emissions stays in the air, so the same emissions produce a faster rise in concentration. The report also notes that Southeast Asian and large parts of South American tropical forests have shifted from CO2 sinks to sources.
How much carbon budget is left?
A carbon budget is the total amount of CO2 that can still be emitted before a chosen temperature limit is likely to be passed. For limiting warming to 1.5 degrees Celsius, the remaining budget is 170 billion tonnes of CO2, which the report calls virtually exhausted. That equals about four years at 2025 emission levels. Lead author Pierre Friedlingstein of the University of Exeter says it will be gone before 2030 at the current emission rate.
Is there any good news?
The report finds that 35 countries have cut emissions while growing their economies, evidence that the two can be decoupled. Japan, at a projected 2.2 percent fall, is the only place with a decline among the regions listed above. Replacing fossil fuels with sources such as renewable energy is one of the main ways to cut emissions further, though the report itself stresses that emissions must fall much faster than they have.
Who produces these numbers?
The Global Carbon Budget is produced by the Global Carbon Project with an international team of more than 130 scientists from over 90 institutions, among them the University of Exeter, the University of East Anglia, CICERO, Ludwig Maximilian University of Munich, the Alfred Wegener Institute and the University of California, Davis. Because the numbers combine direct energy data with models, each new edition revises earlier estimates slightly. Releasing the numbers during the climate talks gives negotiators and researchers a shared reference, and single-year changes of around one percent are best read as indicative rather than exact.
Frequently asked questions
Did global CO2 emissions fall in 2025?
Fossil CO2 emissions are projected to be a record 38.1 billion tonnes, up 1.1 percent. Total emissions including land-use change are projected to be slightly lower than last year.
What does 425.7 ppm mean?
It is the projected concentration of CO2 in the atmosphere in 2025, 52 percent higher than before the industrial era.
What is the difference between fossil and total emissions?
Fossil emissions come from burning coal, oil and natural gas. Total emissions add the CO2 released by land-use change, such as clearing forests.
Which country’s emissions rose the most?
Among the places listed, the United States had the largest projected percentage rise at 1.9 percent, followed by India at 1.4 percent.
Who publishes the Global Carbon Budget?
The Global Carbon Project, an international research collaboration that updates the budget every year.
How long will the 1.5 degree budget last?
About four years at 2025 emission levels, according to the Global Carbon Project.