Higher than expected CO₂ fertilization inferred from leaf to global observations

Area of Science:

• Earth System Science
• Ecology
• Climate Science

Background:

• Terrestrial biosphere activity has increased, impacting the global net land carbon sink (NLS) and atmospheric CO2 growth.
• Global terrestrial gross primary production (GPP) has risen ~31% since 1900, but drivers remain unclear.

Purpose of the Study:

• To identify the dominant driver of increased terrestrial biosphere activity.
• To quantify the CO2 fertilization effect on photosynthesis.
• To project future land carbon sink capacity under different CO2 fertilization scenarios.

Main Methods:

• Reconciling leaf-level and global atmospheric data.
• Analyzing trends in modeled biospheric activity.
• Comparing historical CO2 fertilization estimates with new findings.

Main Results:

• Rising atmospheric CO2 is the dominant driver of increased GPP.
• A global CO2 fertilization effect of 30% since 1900 was identified, nearly double current estimates.
• Future land carbon sink projected to be significantly larger under higher CO2 fertilization.

Conclusions:

• The CO2 fertilization effect plays a larger role in modulating future anthropogenic CO2 than previously estimated.
• Enhanced land carbon sinks are crucial for meeting Paris Agreement climate targets.
• Preserving terrestrial carbon sinks is vital for climate change mitigation.