Rising nitrogen deposition leads to only a minor increase in CO₂ uptake in Earth system models

Area of Science:

• Earth System Science
• Biogeochemical Cycles
• Climate Change Research

Background:

• Current Earth System Models (ESMs) often neglect nitrogen cycling, despite its critical role in regulating primary productivity and influencing climate feedbacks.
• Understanding coupled carbon-nitrogen (C-N) cycles is crucial as ESMs increasingly incorporate these interactions.

Purpose of the Study:

• To develop a novel framework for quantifying C-N feedbacks in ESMs.
• To assess the impact of rising nitrogen deposition on carbon dioxide (CO2) uptake and nitrous oxide (N2O) emissions.

Main Methods:

• Development of a new framework to integrate nitrogen cycling into ESMs.
• Utilizing a model ensemble to simulate C-N cycle interactions under rising nitrogen deposition scenarios.

Main Results:

• Rising nitrogen deposition acts as a negative feedback, enhancing CO2 fertilization on land and in the ocean.
• The increase in CO2 uptake due to nitrogen deposition is minimal compared to CO2 uptake reductions when C-N cycling is coupled.
• Nitrogen deposition leads to increased N2O emissions from both land and ocean.

Conclusions:

• Rising nitrogen deposition has a limited, marginal effect on mitigating climate change.
• The study underscores the importance of explicitly including nitrogen cycling in ESMs for accurate climate projections.