The Climate Benefit of Carbon Sequestration

Ecosystems play a fundamental role in climate change mitigation by taking up carbon from the atmosphere and storing it for a period of time in organic matter. Although climate impacts of carbon emissions can be quantified by global warming potentials, there is not a formal metric to assess climate benefits of carbon removals by sinks. We introduce here the Climate Benefit of Sequestration (CBS), a metric that quantifies the radiative effect of taking up carbon dioxide from the atmosphere and retaining it for a period of time in an ecosystem before releasing it back to the atmosphere.  To quantify CBS, we also propose a formal definition of carbon sequestration (CS) as the integral of a sequestered amount of carbon over the time horizon it remains stored in an ecosystem. Both metrics incorporate the separate effects of i) inputs (amount of atmospheric carbon removal), and ii) transit time (time of carbon retention) in carbon sinks, which can vary largely for different ecosystems or management types. In three separate examples, we show how to compare different carbon management practices in forestry and soils using CS and CBS. We believe these metrics can be useful in resolving current controversies about the management of ecosystems for climate change mitigation.