Carbon sequestration ought to be permanent on climate-relevant timescales

Markets for durable carbon removal credits are expanding despite conflicting rules and standards. A major unresolved issue surrounds the permanence of sequestration and what it means. We draw from the principles of ‘intergenerational equity’ and the ‘polluter-pays’ to argue that sequestration ought to be permanent on climate-relevant timescales which geoscience has determined to be in excess of 10000 years. This is far longer than the typical durability of carbon credits. In this perspective, we examine the implications of having to guarantee the permanence of carbon removal either by permanent sequestration or by a sequence of temporary storage. We will review the science underlying the definition of climate-relevant permanence. We will ask why we should care, who gets to reap the benefits from not guaranteeing permanence, who will suffer the consequences, who pays for permanence, and who gets to decide.