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What is the Global Carbon Budget (GCB)?
Since 2006, the Global Carbon Budget has summed up all anthropogenic emissions of carbon dioxide (CO₂) to the atmosphere, and all the carbon removed from the atmosphere by land and ocean. This allows us to account for the rise in atmospheric CO₂, which drives climate warming. It brings together many independent sources of data, including systematic observations and state-of-the-art model ensembles, to provide a robust, independent scientific assessment of CO₂ sources and sinks each year and their associated uncertainties. It tracks changes over time in CO₂ emissions from burning and other uses of fossil fuels (coal, gas, oil; and cement production) and from land use change (e.g., deforestation, reforestation). It also assesses how the Earth’s carbon sinks on the land and oceans are changing over time in response to human activities and climate change (i.e., carbon-climate feedbacks). These data are integrated at global, regional, and national levels, providing a benchmark against which UNFCCC negotiations can take place. The Paris Agreement goal of limiting global warming well below 2°C sets the budget for the additional CO₂ that can be added to the atmosphere for this temperature target. The remaining carbon budget diminishes each year, and has direct ramifications for UNFCCC negotiators working to achieve the Paris Agreement goals. The GCB, now in its 20th edition, is the most comprehensive carbon budget assessment available, and contributes to assessments and reports by the IPCC and the World Meteorological Organization, in addition to supporting national governments and non-governmental organizations.
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What are the latest results of the GCB?
The GCB is updated annually, with complete data provided up to the previous year (2024), with projections of the current year (2025) based on data available at the time the final manuscript is submitted (usually around September/October).
The 2025 Global Carbon Budget projects 38.1 billion tonnes of fossil carbon dioxide (CO₂) emissions this year. That’s a rise in global carbon emissions of 1.1% in 2025 – reaching a record high.
Decarbonisation of energy systems is progressing in many countries – but this is not enough to offset the growth in global energy demand.
Emissions from land-use change (such as deforestation) are projected to be down to 4.1 billion tonnes in 2025.
Total CO₂ emissions (fossil and land use) are projected to be slightly lower than last year.
With the end of the 2023-24 El Niño weather pattern – which caused heat and drought in many regions – the land “sink” (absorption of CO₂ by natural ecosystems) recovered this year to the pre-El Niño level.
This year’s report examined the impact of climate change on the land and ocean carbon sinks. It finds that 8% of the rise in atmospheric CO₂ concentration since 1960 is due to climate change weakening the land and ocean sinks.
The remaining carbon budget to limit global warming to 1.5°C is “virtually exhausted”.
With no sign of the urgently needed decline of global emissions, the level of CO₂ in the atmosphere – and the dangerous impacts of global warming – continue to increase.
Read the press release in full.
What is the remaining carbon budget?
The remaining carbon budget is the amount of carbon dioxide that can still be emitted while keeping global warming within a certain temperature limit, such as 1.5°C above pre-industrial levels. The budget for 1.5°C is rapidly diminishing as human emissions from fossil fuels and land-use change continue.
How long until we pass 1.5°C of global warming?
While many temperature records have been broken in recent years , the GCB study focuses on the remaining carbon budget before 1.5°C is consistently breached over multiple years. At the current rate of emissions, the team estimates a one-in-two chance that four more years of current CO₂ emissions would bring global warming to 1.5°C. All such projections have a degree of uncertainty, but it’s clear that the remaining carbon budget is running out fast.
Four years are clearly insufficient to decarbonize the world’s energy system. It therefore seems inevitable that the 1.5°C target of the Paris agreement will be breached.
The remaining carbon budgets to limit warming to 1.7°C and 2°C above the 1850-1900 level are 525 GtCO₂ (12 years at 2025 emissions levels) and 1055 GtCO₂ (25 years), respectively.
Are we making any progress in reducing emissions?
Despite the continuous growth in global emissions, trends in emissions in some regions and countries are beginning to decline, showing that climate and energy policies supporting low or zero carbon energies, such as solar and wind, can be effective. There are now 35 countries which have had emissions declining over the past decade (2015-2024), while their economy, measured as their Gross Domestic Product, has grown. This amount is twice as big as the previous decade:
Andorra, Australia, Austria, Belgium, Bulgaria, Czechia, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Israel, Jordan, Latvia, Luxembourg, Netherlands, New Zealand, Norway, Poland, Portugal, South Korea, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Taiwan, Thailand, United Kingdom, and USA.
The following countries were added to the list in 2015-2024 compared to 2005-2014: Andorra, Australia, Denmark, Estonia, Finland, Greece, Hungary, Ireland, Israel, Jordan, Latvia, Norway, Poland, Portugal, South Korea, Slovenia, Spain, Taiwan, Thailand. The following countries were removed: North Macedonia and Uzbekistan.
There is progress in other countries too, with China, the single largest carbon emitter, having slowed considerably the pace of emissions growth, with this year’s data showing the possibility of no growth and even possibly a small decline. The final trend will be confirmed over the next months as data for the rest of the year becomes available.
Why are wildfires included in the GCB?
In 2023 we included for the first time, analysis on the impacts of wildfires. Wildfires in forests, grasslands, and other ecosystems can be caused by humans or natural processes such as lightning. Wildfires are part of the carbon cycle, and are affected by and affecting Earth’s climate through several mechanisms:
- Release of CO₂ to the atmosphere from the loss of carbon stored in vegetation: since wildfire damages vegetation, it reduces the amount of carbon stored in an ecosystem, taking from a few years to a century or more (depending on where the fire occurs) to recover and reabsorb carbon from the atmosphere. If wildfire returns before the ecosystem has recovered, or if wildfires become more severe, the ecosystem may lose some of its capacity to absorb and store carbon. There is also potential for the release of methane (CH4) if there is incomplete combustion of the organic matter.
- Black carbon (soot) emissions: as fine particulate matter, soot can be carried by the wind over long distances. If deposited on snow or ice, soot can accelerate climate warming by reducing the reflectivity of the ice surface leading to increased absorption of sunlight and accelerated ice melt. It is also a pollutant detriment to human health.
- Nutrient recycling acts to restore carbon sinks: wildfire releases nutrients into the soil from vegetation and animals more quickly than if they had slowly decayed over time. This increases soil fertility and enhances vegetation growth, helping to re-establish the carbon sink. Smoke from wildfires also contains iron and phosphorus, which, when deposited into the ocean, can boost the growth of algae, sequestering large amounts of carbon that could wholly offset the carbon released by the fire in some cases.
- Climate-carbon feedbacks: Climate change is affecting the role of wildfire in the carbon cycle. Rising temperatures, changes in trends and patterns of precipitation and lightning, and faster growth of vegetation due to higher levels of carbon dioxide in the atmosphere are some of the changes that are contributing to an increased likelihood and severity of wildfires. Climate-related changes can also impede post-fire ecosystem recovery and carbon sequestration.
- Wildfire may be reducing the remaining carbon budget overall, and therefore contributing to global warming. However it is not currently possible to fully account for the wildfire-related components in the GCB due to the difficulty of differentiating between fires caused by humans and those of natural causes.
What is Carbon Dioxide Removal (CDR)? What contribution does CDR make to tackling Climate change?
Anthropogenic carbon dioxide removal (CDR) aims to remove CO₂ from the atmosphere and store it in the biosphere (i.e., vegetation and soils) or permanently in geological reservoirs underground. Examples of biospheric carbon sequestration are afforestation, reforestation, and more general revegetation of other vegetation types. These vegetation-related methods account for 99% of the global 2.2 GtCO₂ CDR per year. The GCB quantifies this type of CDR in its analysis, looking at CO2 sources and sinks from land use changes, which are purposeful human activities to remove CO₂.
The Global Carbon Budget 2025 also includes other CDR methods not based on vegetation, such as direct air capture and storage, and enhanced weathering methods. These CDR methods offset 0.003 million tonnes of CO₂ in 2024- a negligible fraction of fossil CO₂ emissions . While it is an additional anthropogenic sink, it remains about a million times smaller than current fossil CO₂ emissions.
Although CDR has a role in mitigating climate change, it is not a substitute or distraction from reducing CO₂ emissions, as much and as fast as possible.
What are natural sinks, and why are they changing?
Natural sinks refer to forests, soils, and oceans that absorb and store CO₂ from the atmosphere. These carbon sinks have increased over time as atmospheric CO₂ levels have increased. However, these natural sinks are also changing due to rising land or ocean temperatures, altered rainfall patterns on land, or changes in large-scale ocean circulation. There is modelling evidence that climate change already reduces the land and ocean sinks making their future contribution to mitigating climate change more uncertain. Taken together, the land and ocean sinks continued to take up around half of anthropogenic CO₂ emitted to the atmosphere, despite the negative impact of climate change.
The Global Carbon Budget (GCB) 2025 has recalculated how much CO₂ the land and ocean are absorbing each year. Using new data and improved understanding, we have resolved some long-standing inconsistencies in previous assessments. This important update also gives a clearer picture of the emergence of climate impacts on the natural sinks.
The ocean’s role in absorbing CO₂ has been revised upward, while the land’s role has been revised downward.
Over the past decade, the ocean CO₂ sink has taken up 29% of the total human CO₂ emissions (compared to 26% in previous budgets) and the land CO₂ sink has taken up 21% (compared to 29% in previous budgets).
After a substantially weaker land sink in 2024 due to the 2023-2024 El Niño conditions, the preliminary estimate for 2025 suggests a full recovery of the sink to pre-El Niño levels.
The land and ocean CO₂ sink are 25% and 7% smaller, respectively, than they would have been without the effects of climate change and climate variability, on average for the 2015-2024 period. That means that the total sink (land and ocean combined) is nearly 20% smaller.
What is the Global stocktake?
The Global Stocktake (GST) is a process for countries and stakeholders to see where they’re collectively making progress toward meeting the goals of the Paris Agreement and where they are not. The GST is like taking an inventory. It means looking at everything related to where the world stands on climate action and support (e.g. emissions, mitigation, finances, policies, identifying gaps), and working together to chart a better course forward to accelerate climate action.
The 2023 Global Stocktake (GST) concluded that current global climate efforts are not sufficient to meet the Paris Agreement’s goals of limiting warming to 1.5°C. One of the key points was that current climate actions are falling short, and countries must strengthen their climate commitments. This includes a transition away from fossil fuels.
The next Global Stocktake is due in 2028.
What are NDCs?
Nationally Determined Contributions (NDCs) are individual countries’ commitments under the Paris Agreement to reduce greenhouse gas emissions and combat climate change. NDCs play a crucial role in the global effort to limit warming to well below 2°C, ideally aiming for 1.5°C, and are essential for tracking progress in climate action.
Each NDC outlines a country’s planned actions and targets for mitigating climate change, reflecting its national circumstances, capabilities, and priorities.
A key aspect of NDCs include emission reduction targets. Countries specify their quantitative targets for reducing greenhouse gas emissions. Many countries have set targets for 2030 and longer term strategies to reach net zero emissions by mid century (often expressed as a percentage reduction from a baseline year).
Under the Paris Agreement, countries should update their NDCs every five years. The next round of Nationally Determined Contributions (NDCs) was due in early 2025.
GCB @COP 30
The GCB 2025 will be presented at a number of events at COP 30:
