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<p><span id="page4376"/>The amount of additional future temperature change following a complete cessation of <span class="inline-formula">CO₂</span> emissions is a measure of the unrealized warming to which we are committed due to <span class="inline-formula">CO₂</span> already emitted to the atmosphere. This “zero emissions commitment” (ZEC) is also an important quantity when estimating the remaining carbon budget – a limit on the total amount of <span class="inline-formula">CO₂</span> emissions consistent with limiting global mean temperature at a particular level. In the recent IPCC Special Report on Global Warming of 1.5&thinsp;<span class="inline-formula">^∘</span>C, the carbon budget framework used to calculate the remaining carbon budget for 1.5&thinsp;<span class="inline-formula">^∘</span>C included the assumption that the ZEC due to <span class="inline-formula">CO₂</span> emissions is negligible and close to zero. Previous research has shown significant uncertainty even in the sign of the ZEC. To close this knowledge gap, we propose the Zero Emissions Commitment Model Intercomparison Project (ZECMIP), which will quantify the amount of unrealized temperature change that occurs after <span class="inline-formula">CO₂</span> emissions cease and investigate the geophysical drivers behind this climate response. Quantitative information on ZEC is a key gap in our knowledge, and one that will not be addressed by currently planned CMIP6 simulations, yet it is crucial for verifying whether carbon budgets need to be adjusted to account for any unrealized temperature change resulting from past <span class="inline-formula">CO₂</span> emissions. We request only one top-priority simulation from comprehensive general circulation Earth system models (ESMs) and Earth system models of intermediate complexity (EMICs) – a branch from the 1&thinsp;% <span class="inline-formula">CO₂</span> run with <span class="inline-formula">CO₂</span> emissions set to zero at the point of 1000&thinsp;PgC of total <span class="inline-formula">CO₂</span> emissions in the simulation – with the possibility for additional simulations, if resources allow. ZECMIP is part of CMIP6, under joint sponsorship by C4MIP and CDRMIP, with associated experiment names to enable data submissions to the Earth System Grid Federation. All data will be published and made freely available.</p>