Emerging climate impact on carbon sinks in a consolidated carbon budget

Despite the adoption of the Paris Agreement 10 years ago, carbon dioxide (CO 2) emissions from burning fossil fuels continue to increase, pushing atmospheric CO 2 levels to 423 ppm in 2024 and driving human-induced warming to 1.36 °C, within years of breaching the 1.5 °C limit 1,2. Accurate reporting of anthropogenic and natural CO 2 sources and sinks is a prerequisite to tracking the effectiveness of climate policy and detecting carbon-sink responses to climate change. Yet notable mismatches between reported emissions and sinks have so far prevented confident interpretation of their trends and drivers 1. Here we present and integrate recent advances in observations and process understanding to address some long-standing issues in global carbon budget estimates. We show that the magnitude of the natural land sink is substantially smaller than previously estimated, whereas net emissions from anthropogenic land-use change are revised upwards 1. The ocean sink is 15% larger than the land sink, consistent with recent evidence from oceanic and atmospheric observations 3,4. Climate change reduces the efficiency of the sinks, particularly on land, contributing 8.3 ± 1.4 ppm to the atmospheric CO 2 increase since 1960. The combined effects of climate change and deforestation have turned Southeast Asian and large parts of South American tropical forests from CO 2 sinks to sources. This underscores the need to halt deforestation and limit warming to prevent further loss of carbon stored on land. Improved confidence in assessments of CO 2 sources and sinks is fundamental for effective climate policy.