The proportionality between tonne-years of temporary carbon storage and inertial climate variables

Human- and nature-driven disturbances threaten the longevity of land-based carbon removal. However, even carbon that is temporarily stored still reduces global temperatures while said carbon remains stored. This temporary carbon storage can be measured in tonne-years, a metric that measures the time-integrated amount of carbon storage. Previous studies have identified two key findings: 1) that tonne-years of temporary storage are proportional to degree-years of avoided warming, and 2) that degree-years of avoided warming are proportional to climate outcomes that affect inertial components of the climate system, such as thermosteric sea level rise, ocean warming, and permafrost carbon loss. As a result, tonne-years of temporary carbon storage should also be proportional to climate outcomes influencing these inertial climate variables. Using the UVic Earth System Climate Model (UVic-ESCM), we simulate each Shared Socioeconomic Pathway (SSP) scenario, along with nine variations of each representing nine removal pathways with varying magnitudes and durations of carbon removal. Our results demonstrate that tonne-years of carbon storage are proportional to climate outcomes affecting inertial components of the climate system. This proportionality holds across a wide range of peak temperatures and temporary removal pathways, emphasizing that the impact of temporary carbon storage is path independent for some slow-responding climate variables.