Global annual terrestrial CO2 sink
| Object type | Damage Signal |
|---|---|
| SIGNAL Earth ID | DS-00701 |
| Observable type | Carbon uptake flux (terrestrial) |
| Unit | PgC/year (petagrams of carbon per year) |
| Temporal structure | Annual |
| Monitoring backbone | DGVM ensemble |
The
Global annual terrestrial CO2 sink represents the total amount of carbon dioxide absorbed by terrestrial ecosystems worldwide each year. This process plays a critical role in the global carbon cycle by offsetting a portion of anthropogenic CO2 emissions and helping to moderate atmospheric greenhouse gas concentrations. Terrestrial sinks include forests, grasslands, wetlands, and other land-based vegetation and soils that sequester carbon through photosynthesis and storage in biomass and soil organic matter.
Understanding the magnitude and variability of the terrestrial CO2 sink is essential for assessing the Earth's capacity to buffer climate change and for informing climate models. The sink's strength is influenced by factors such as land use changes, climate variability, ecosystem productivity, and disturbances. Monitoring this sink at a global scale requires integrating diverse data sources and modeling approaches.
Within the context of global carbon budgets, the terrestrial CO2 sink is a dynamic component that interacts with atmospheric, oceanic, and anthropogenic carbon fluxes. Its quantification supports international efforts to track progress toward emission reduction targets and to understand feedbacks in the Earth system.
Geographic / System Context
[edit]The global terrestrial CO2 sink encompasses all land-based ecosystems across the Earth's continents and islands. This includes a wide range of biomes such as tropical, temperate, and boreal forests, savannas, grasslands, tundra, and wetlands. These ecosystems vary in their carbon uptake capacity due to differences in climate, vegetation type, soil characteristics, and land management practices. The spatial distribution of the sink is heterogeneous, with tropical forests generally representing the largest carbon uptake regions due to high productivity, while boreal and temperate zones contribute seasonally and are sensitive to disturbances such as fire and insect outbreaks.
Monitoring and Measurement
[edit]Monitoring the global terrestrial CO2 sink involves a combination of observational data and modeling frameworks. Direct measurements include eddy covariance flux towers that quantify carbon exchange at local scales, forest inventories that assess biomass changes, and remote sensing technologies that estimate vegetation productivity and land cover changes. These data are integrated into Dynamic Global Vegetation Models (DGVMs), which simulate carbon fluxes based on climate inputs, vegetation dynamics, and soil processes. Ensemble approaches that combine multiple DGVMs provide robust estimates of the sink by accounting for model uncertainties and variability in input data. Scientific institutions and international research collaborations contribute to the continuous refinement of these monitoring systems.
Within the SIGNAL system, this phenomenon is treated as a defined environmental signal whose boundaries and measurement conventions are described below.
Signal Definition
[edit]The global annual terrestrial CO2 sink is defined as the net carbon uptake flux by terrestrial ecosystems worldwide, expressed in petagrams of carbon per year (PgC/year). It quantifies the annual total amount of carbon dioxide removed from the atmosphere and stored in terrestrial vegetation and soils, excluding carbon losses from land use change and disturbances. The observable type associated with this signal is the carbon uptake flux (terrestrial), representing the net balance of photosynthetic carbon assimilation minus autotrophic and heterotrophic respiration.
Boundary Conditions
[edit]Boundary inclusions for this signal encompass all natural and managed terrestrial ecosystems that actively sequester carbon dioxide through biological processes. This includes forests, grasslands, croplands, wetlands, and other vegetated land areas. Carbon stored in aboveground and belowground biomass, as well as soil organic carbon pools, are considered part of the sink. Boundary exclusions involve carbon fluxes associated with land use change emissions, such as deforestation and land degradation, which are accounted separately. Emissions from fossil fuel combustion, oceanic carbon uptake, and non-terrestrial sources are outside the scope of this signal.
Aggregation Semantics
[edit]Geographically, the signal aggregates carbon uptake fluxes across all terrestrial land surfaces at a global scale, integrating spatial heterogeneity in ecosystem types and environmental conditions. Temporally, the aggregation is annual, capturing the net carbon flux over each calendar year to reflect seasonal and interannual variability. Cross-signal aggregation involves combining this terrestrial sink estimate with other carbon flux components, such as oceanic sinks and anthropogenic emissions, to form comprehensive global carbon budgets. Aggregation methods rely on ensemble modeling outputs that harmonize data sources and temporal resolutions to produce consistent and comparable estimates.
Observational Status
[edit]Current monitoring of the global terrestrial CO2 sink leverages an ensemble of Dynamic Global Vegetation Models informed by observational datasets, providing annual estimates with recognized uncertainties. These models are continually updated to incorporate improved climate data, land use information, and ecosystem process understanding. Future SIGNAL releases may enhance temporal resolution, incorporate additional observational constraints, and refine spatial delineations of sink strength. Ongoing research aims to better characterize feedback mechanisms and the impacts of disturbances on sink dynamics.
Related Signals
[edit]- None specified
Key Associated People
[edit]- Pierre Friedlingstein — Steward-candidate (University of Exeter) [Lead author]