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Global carbon budget reveals weaker land carbon sink

Global carbon budget reveals weaker land carbon sink

New Capabilities

New estimates show natural carbon absorption is 20% lower than previously calculated, with climate change already degrading Earth's capacity to absorb CO₂

January 15th, 2026: Nature Study Reveals Smaller Land Carbon Sink

Overview

For decades, scientists assumed that forests and soils were absorbing roughly 30% of humanity's carbon dioxide emissions. A major reassessment published in Nature in January 2026 shows they've been overestimating: the natural land carbon sink is actually 20% smaller than previously calculated—0.6 billion tonnes of carbon per year that scientists thought was being absorbed is staying in the atmosphere.

The revision has immediate consequences for climate targets. With the remaining carbon budget for limiting warming to 1.5°C now estimated at just 130 billion tonnes—roughly three years of emissions at current rates—the discovery that nature is absorbing less CO₂ than expected means the window for action is even narrower than climate models suggested. The study also found that tropical forests in Southeast Asia and large parts of South America have already flipped from carbon sinks to carbon sources.

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Key Indicators

20%
Sink overestimate
The natural land carbon sink is 20% smaller than previous Global Carbon Budget estimates
0.6 Gt
Missing absorption
Billion tonnes of carbon per year that was assumed to be absorbed by land but remains in atmosphere
8.3 ppm
Climate-driven CO₂ increase
Additional atmospheric CO₂ since 1960 attributed to climate change weakening natural sinks
~3 years
Budget remaining
Time until the remaining carbon budget for 1.5°C warming is exhausted at current emission rates

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People Involved

Pierre Friedlingstein
Pierre Friedlingstein
Director of Exeter's Global Carbon Budget Office
 Corinne Le Quéré
Corinne Le Quéré
Royal Society Research Professor at University of East Anglia

Organizations Involved

Global Carbon Project
Global Carbon Project
International Research Consortium
Publisher of annual Global Carbon Budget

International scientific collaboration that publishes authoritative annual assessments of global carbon emissions and their distribution among atmosphere, ocean, and land.
Intergovernmental Panel on Climate Change
Intergovernmental Panel on Climate Change
UN scientific body
Primary international authority on climate science

United Nations body that assesses climate science and provides the scientific basis for international climate policy.

Timeline

  1. Nature Study Reveals Smaller Land Carbon Sink

    Publication

    A major reassessment in Nature shows the natural land carbon sink is 20% smaller than previously estimated. The study finds climate change has already reduced sink efficiency, adding 8.3 ppm to atmospheric CO₂ since 1960.

  2. COP30 Concludes in Belém, Brazil

    Policy

    Climate negotiations conclude with the Belém Package, including a Forest and Climate Roadmap and the launch of Brazil's Tropical Forests Forever Facility, which raised $6.6 billion.

  3. Global Carbon Budget 2025 Published

    Publication

    The Global Carbon Project reports fossil fuel emissions reached a record 38.1 billion tonnes in 2025. Land-use emissions declined nearly 10% due to reduced Amazon deforestation, but total emissions remained essentially flat.

  4. Atmospheric CO₂ Reaches 423 ppm

    Milestone

    Annual average atmospheric CO₂ concentration reaches 423 parts per million, driving human-induced warming to 1.36°C above pre-industrial levels.

  5. Global Land Carbon Sink Collapses

    Finding

    Scientists report that in 2023, the world's forests stopped acting as a net carbon sink. The combination of Amazon drought, Canadian wildfires, and El Niño caused atmospheric CO₂ growth to spike 86% compared to 2022.

  6. Canadian Wildfires Begin Record Season

    Event

    Unprecedented wildfires in Canada emit nearly 480 megatonnes of carbon—five times the 20-year average—accounting for 23% of global wildfire emissions for the year.

  7. Northern Forests Become Net Carbon Emitters

    Finding

    Research later reveals that forests across Earth's northern hemisphere shifted from carbon sinks to net carbon emitters starting in 2016, driven by increasing droughts, wildfires, and forest degradation.

  8. Paris Agreement Adopted

    Policy

    196 nations adopt the Paris Agreement, committing to limit global warming to well below 2°C and pursue efforts to limit it to 1.5°C above pre-industrial levels.

  9. Global Carbon Budget Annual Reports Begin

    Publication

    Corinne Le Quéré initiates the annual Global Carbon Budget publication through the Global Carbon Project, establishing a systematic framework for tracking global carbon emissions and sinks.

  10. First Continuous CO₂ Measurement Begins

    Science

    Charles David Keeling takes the first atmospheric CO₂ measurement at Mauna Loa Observatory in Hawaii, recording 313 parts per million. This initiates the longest continuous record of atmospheric CO₂.

Scenarios

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1

Carbon Removal Investment Accelerates to Fill the Gap

The revised sink estimates trigger increased investment in engineered carbon dioxide removal technologies. With nature-based solutions now understood to be less effective than assumed, governments and corporations redirect funding toward direct air capture, enhanced weathering, and ocean-based removal. The Science Based Targets initiative finalizes new standards in 2026 that explicitly require technological CDR to compensate for weaker natural sinks.

Discussed by: World Resources Institute, Carbon180, Nature Climate Change
Consensus —
2

1.5°C Target Officially Declared Unreachable

With the remaining carbon budget for 1.5°C now estimated at only 130 billion tonnes—and natural sinks absorbing less than expected—climate scientists and policymakers shift focus to limiting warming to 2°C. International negotiations pivot toward enhanced adaptation funding and managed overshoot scenarios where temperatures temporarily exceed 1.5°C before declining.

Discussed by: Climate Analytics, IPCC scientists, Carbon Brief
Consensus —
3

Tropical Forests Continue Transition to Carbon Sources

The trend identified in the study—tropical forests in Southeast Asia and South America flipping from sinks to sources—accelerates. Continued deforestation, rising temperatures, and increased fire frequency push additional forest regions past tipping points. By 2030, the majority of tropical forests are net carbon emitters rather than absorbers.

Discussed by: Nature Geoscience, World Resources Institute, Global Forest Watch
Consensus —
4

Carbon Credit Market Undergoes Major Correction

The finding that land carbon sinks are weaker than estimated compounds existing concerns about forest carbon credit integrity. Credits based on overestimated sequestration rates face large-scale invalidation. The voluntary carbon market contracts further as buyers demand credits based on revised baseline calculations.

Discussed by: Integrity Council for Voluntary Carbon Market, Clean Air Task Force, BCG
Consensus —

Historical Context

Keeling Curve Discovery (1958)

March 1958

What Happened

Charles David Keeling installed a carbon dioxide monitoring instrument at the Mauna Loa Observatory in Hawaii, beginning continuous atmospheric CO₂ measurements. His first reading recorded 313 parts per million. Within two years, the data showed a clear upward trend underlying seasonal variation—the first direct evidence that human activities were measurably increasing atmospheric CO₂.

Outcome

Short Term

The scientific community gained the first reliable baseline for atmospheric CO₂, though climate change remained a fringe concern in policy circles.

Long Term

The Keeling Curve became the most iconic dataset in climate science, directly informing the formation of the IPCC in 1988 and providing the evidentiary foundation for international climate negotiations.

Why It's Relevant Today

The January 2026 study refines the picture that began with Keeling's measurements. While Keeling showed CO₂ was accumulating in the atmosphere, this study reveals that less of it is being absorbed by land than scientists assumed—meaning more of humanity's emissions stay in the atmosphere than previous carbon budgets indicated.

Amazon Drought and Fire Crisis (2023-2024)

July 2023 – December 2024

What Happened

Record drought struck the Amazon basin while Canadian wildfires burned over 18 million hectares. Scientists reported at a 2024 conference in Manaus that for the first time on record, the world's forests stopped acting as a net carbon sink in 2023. Atmospheric CO₂ growth spiked 86% compared to the previous year. Canadian fires alone contributed 23% of global wildfire emissions.

Outcome

Short Term

The land carbon sink temporarily collapsed to near zero, causing the largest single-year spike in atmospheric CO₂ growth rate in the measurement record.

Long Term

The event demonstrated how climate change creates feedback loops that weaken natural carbon absorption, previewing the chronic weakening now quantified in the 2026 study.

Why It's Relevant Today

The 2023-2024 events were treated as anomalies caused by El Niño and exceptional fires. The 2026 study shows they were symptoms of a structural problem: climate change has been systematically weakening land carbon sinks for decades, contributing an additional 8.3 ppm of CO₂ to the atmosphere since 1960.

Voluntary Carbon Market Crisis (2023-2024)

January 2023 – December 2024

What Happened

A series of investigations by journalists and scientists revealed that up to 87% of forest carbon credits purchased by major companies likely did not deliver real climate benefits. Millions of credits were invalidated. The voluntary carbon market contracted by 61% as buyers lost confidence in offset quality. Major credit certifiers faced calls for fundamental reform.

Outcome

Short Term

Corporate offset strategies faced reputational risk, and several companies abandoned offset-based net-zero claims. Credit prices diverged sharply based on quality ratings.

Long Term

New integrity standards emerged from the Integrity Council for Voluntary Carbon Markets, and the Science Based Targets initiative began developing stricter guidelines for carbon removal claims.

Why It's Relevant Today

The 2026 finding that land carbon sinks are 20% smaller than estimated compounds the carbon credit crisis. Credits calculated using inflated baseline absorption rates are even less valuable than previously thought, potentially triggering another wave of credit invalidations.

Sources

(12)
+6
Nature Global Carbon Project Carbon Brief Science Advances Future Earth European Space Agency Climate Office World Resources Institute Copernicus Atmosphere Monitoring Service Climate Change Tracker COP30 Brazil Nature News Nature Climate Change