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Global Carbon Budget
The Global Carbon Budget: FAQs feature image

The Global Carbon Budget: FAQs

The Global Carbon Budget: FAQs

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, to account for the rise in atmospheric CO2, as this 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 and from land use change. It also assesses how the Earth’s carbon sinks on the land and oceans are changing in response to human activities and climate change. 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 is the most comprehensive carbon budget assessment available, and contributes to assessments or reports by the IPCC and the World Meteorological Organization.

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What are the latest results of the GCB?

The GCB is updated annually; results for 2024:

The 2024 Global Carbon Budget projects fossil carbon dioxide (CO2) emissions of 37.4 billion tonnes, up 0.8% from 2023.

Despite the urgent need to cut emissions to slow climate change there is still “no sign” that the world has reached a peak in fossil CO2 emissions.

With projected emissions from land-use change (such as deforestation) of 4.2 billion tonnes, total CO2 emissions are projected to be 41.6 billion tonnes in 2024, up from 40.6 billion tonnes last year.

Over the last 10 years, fossil CO2 emissions have risen while land-use change CO2 emissions have declined on average – leaving total emissions roughly level over that period.

This year, both fossil and land-use change CO2 emissions are set to rise, with drought conditions exacerbating emissions from deforestation and forest degradation fires during the El Niño climate event of 2023-2024.

With over 40 billion tonnes released each year at present, the level of CO2 in the atmosphere continues to rise – driving increasingly dangerous global warming.

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 to far outpace the rate at which carbon is removed from the atmosphere. 

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 global warming will consistently pass 1.5°C in six years. All such projections have a degree of uncertainty, but it’s clear that the remaining carbon budget – and therefore, the time left to keep to the 1.5°C limit – is running out fast. Six years are clearly insufficient to decarbonize the world’s energy system, and therefore it is now inevitable that the 1.5°C target of the Paris agreement will be breached. In addition to reaching net zero emissions, large efforts to remove atmospheric CO2 could bring the global mean temperature back down to 1.5°C later in the century.

So far, there is little evidence of the credible policies required to cut global emissions enough to prevent the world from staying with the temperature targets of the Paris Agreement. However, trends in emissions in some regions are beginning to decline, showing climate policies can be effective. The New NDCs or national climate plans, due next year, are a vital opportunity to accelerate global action.

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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 cause.

View the full report 

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 durable form, such as in forest biomass and soils through afforestation or reforestation. These vegetation-related methods account for the vast majority CDR removals (99%) . The GCB quantifies this type of CDR in its analysis, looking at CO2 sources and sinks from land use changes. The Global Carbon Budget 2024 has included other CDR methods, such as direct air capture and storage, or enhanced weathering methods.

Current deliberate CDR (not based on vegetation) offset 0.04 million tonnes of CO2 – a negligible fraction of fossil CO2 emissions in 2023.  While it represents a growth in the anthropogenic sink from 2022, it remains about a million times smaller than current fossil CO2 emissions.

CDR may have a role in mitigating climate change but it should not be a substitute for reducing CO2 emissions at source.

View the full report

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 by about 20% and 7%, respectively already, 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 ocean CO2 sink absorbed 10.5 GtCO2 on average each year in the past decade (2014-2023), or 26% of total CO2 emissions. Climate conditions reduced the ocean sink by an estimated 6% in the past decade, likely dominated by altered winds that perturb the ocean circulation with a smaller contribution from the reduced solubility of CO2 in warming waters.

The land CO2 sink absorbed 11.7 GtCO2 on average each year in the past decade (2014-2023), or 29% of total CO2 emissions. Climate conditions reduced the land sink by an estimated 27% in the past decade due to warming and reduced rainfall. The negative effects of climate change can be seen across the globe, and are particularly strong in most of South America, Central Europe, and Southeast Asia.

The land and ocean CO2 sinks fluctuate annually in response to natural climate variability.

For example, the effects of El Niño that developed in late 2023 and early 2024 reduced the land CO2 sink to 8.4 GtCO2 in 2023, 41% below 2022 and 28% below its decadal mean.

The preliminary estimate for the 2024 land CO2 sink suggests a recovery to around 11.9

GtCO2 following the end of El Niño by the second quarter of 2024. The timing and the extent of the recovery will need to be confirmed with consolidated data in 2025.

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, 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 conclusions of the GST  will inform updates to countries’ climate commitments (NDCs) by 2025.

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) is due in 2025.

GCB @COP 29

The GCB 2024 will be presented at a number of events at COP 29:

Visit our events page to find out more

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