Substantial uncertainty remains in both the sign and magnitude of the Zero Emissions Commitment (ZEC): the expected additional change in global surface temperature once we achieve net zero CO₂ emissions.

Uncertainty in ZEC has implications for the remaining carbon budget to stay below the temperature threshold of the Paris climate agreement: a positive ZEC reduces the remaining budget; a negative ZEC opens the door for more ambitious targets or more time to reach net zero.

The prospect of additional warming after net zero is both plausible and significant, with a chance that ZEC could exceed 15% of total global warming.

While a ZEC of 0 means no further change to global surface temperatures, other aspects of the Earth system, such as sea levels, will continue to change in a net zero world due to warming realized previously. These changes should be factored into the assessment of safe warming limits and adaptation plans.

Current climate models do not adequately represent the full scope of complex and interdependent Earth system processes that determine ZEC. The lead article presents a structure for quantifying uncertainty in ZEC and proposes a roadmap for future research into quantifying ZEC and reducing its uncertainties.