Zero emissions commitment depends on warming level

Abstract

Abstract When anthropogenic CO 2 emissions cease, global temperature does not stabilize immediately. The resulting global temperature change, the zero emissions commitment, is central to carbon budget assessments and understanding reversibility of global warming, yet its dependence on prior warming levels remains unclear. Here we show, using zero-emission simulations with the UK Earth System Model (UKESM1.2) across global warming levels of 1.5–5 K, that the zero emissions commitment stays near zero up to 2 K but becomes positive at higher warming levels, reaching 0.4–0.6 K after ~ 150 years. This dependence indicates that stabilizing or reversing warming becomes progressively more difficult as peak temperature rises. We identify the mechanism behind this behaviour: stronger warming from higher radiative disequilibrium and weakening carbon sinks, driven by saturated land carbon uptake and the reduced radiative impact of CO 2 drawdown at higher background CO 2 concentrations. Higher peak warming therefore commits the planet to additional warming, limiting temperature-overshoot reversibility.

The authors' abstract, as published at the source. Nature Climate Change, 2026 · DOI ↗