Implications of the Linear Carbon Sink Model - Highlighted Article

From: Climate Etc.

By: Joachim Dengler

Date: July 10, 2024

Implications of the Linear Carbon Sink Model

This post is the first of two extracts from the paper Improvements and Extension of the Linear Carbon Sink Model.

Introduction – Modelling the Carbon Cycle of the Atmosphere

When a complex system is analyzed, there are two possible approaches. The bottom-up approach investigates the individual components, studies their behavior, creates models of these components, and puts them together, in order to simulate the complex system. The top-down approach looks at the complex system as a whole and studies the way that the system responds to external signals, in the hope to find known patterns that allow conclusions to be drawn about the inner structure.

The relation between anthropogenic carbon emissions, CO2 concentration, and the carbon cycle has in the past mainly been investigated with the bottom-up approach. The focus of interest are carbon sinks, the processes that reduce the atmospheric CO2 concentration considerably below the level that would have been reached, if all CO2 remained in the atmosphere. There are three types of sinks that absorb CO2 from the atmosphere: physical oceanic absorption, the photosynthesis of land plants, and the photosynthesis of phytoplankton in the oceans. Although the mechanisms of carbon uptake are well understood in principle, there are model assumptions that cause divergent results.

The traditional bottom-up approaches are typically box-models, where the atmosphere, the top layer of the ocean (the mixed layer), the deep ocean, and land vegetation are considered to be boxes of certain sizes and carbon exchange rates between them. These models contain lots of parameters, which characterize the sizes of the boxes and the exchange rate between them. The currently favored model is the Bern box diffusion model, where the deep ocean only communicates by a diffusion process with the mixed layer, slowing down the downwelling carbon sink rate so much, that according to the model 20% of all anthropogenic emissions remain in the atmosphere for more than 1000 years. (continue reading)

Implications of the Linear Carbon Sink Model