Schrödinger’s carbon: The hidden uncertainty in every net-zero plan

Tuesday 7 April 2026

Billions of tons of carbon dioxide are being classified as 'dealt with' in global climate plans before anyone can know whether that is true. UT Researcher Rosalie Arendt has given a name to this problem in a new Nature Correspondence: Schrödinger’s carbon.

Carbon capture and storage is a key tool in climate mitigation pathways targeting 1.5°C, particularly for sectors where emissions are hardest to eliminate and for technical carbon dioxide removal from the atmosphere. Yet, carbon capture and storage does not prevent carbon dioxide production. Instead, it functions as a waste management technology, capturing carbon dioxide, transporting it and storing it underground. Despite this, climate models used by governments typically count this carbon dioxide as permanently neutralised.

Naming the Uncertainty

Rosalie Arendt introduces the term Schrödinger’s carbon to describe the uncertainty embedded in this assumption. The concept refers to carbon dioxide that is expected to be captured and stored, but whose long-term fate remains unknowable today. “The name matters,” Arendt explains. “Science policy moves when ideas become nameable. ‘Net zero’ gave policymakers a target. ‘Schrödinger’s carbon’ is an attempt to make a hidden uncertainty visible.” The idea builds on Arendt’s previous research on residual emissions and the need to distinguish clearly between emission reductions and removals. The term emerged during her work on cement decarbonisation, where nearly half of projected emission reductions rely on carbon capture and storage. In such cases, today’s emissions are effectively reclassified as neutral based on the assumption that carbon capture and storage will prevent them from entering the atmosphere.

A System dependent on assumptions

Unlike other mitigation measures, carbon capture and storage generates no valuable output. As a waste management technology, it is inherently harder to incentivize and sustain at the scale envisioned than other mitigation measures. Therefore, delivering carbon capture and storage at scale would require decades of uninterrupted political and financial commitment: an assumption that past experience calls into question, with 88% of projects (1972–2018) cancelled or underperforming.

Emitted or not Emitted / Dead or Alive?

Schrödinger's cat is a thought experiment illustrating the paradox of quantum superposition: a cat in a sealed box is considered simultaneously alive and dead until the box is opened. Similarly, carbon dioxide destined for carbon capture and storage in models exists in multiple states at once: emitted freely, securely stored, or leaking, while its ultimate fate will only be revealed decades to millennia later.

Nearly all major net-zero pathways rely on carbon capture and storage scaling more than a hundredfold by mid-century, but treating this expansion and storage integrity as guaranteed, Arendt argues, risks weakening the urgency to reduce CO₂ production. She is not calling for carbon capture and storage to be abandoned; rather, it should be reserved for carbon dioxide production that is truly unavoidable despite strong efforts to reduce demand and production. Using carbon capture and storage to justify continued CO₂-intensive activity, she warns, undermines mitigation. “Without a name,” she notes, “the uncertainty that carbon capture and storage generates remains invisible in the models shaping global climate policy. Now it has one.”

Rosalie Arendt's correspondence, 'Schrödinger's carbon: The misclassification of carbon capture and storage as standard mitigation', has been published in the scientific journal Nature.

DOI: 10.1038/d41586-026-01009-6