Abstract. Zero Emissions Commitment (ZEC), the expected change in global temperature following the cessation of CO₂ emissions has recently been assessed by the Zero Emissions Commitment Model Intercomparison Project (ZECMIP). ZECMIP concluded that the component of ZEC from CO₂ emissions will likely be close to zero in the decades following the cessation of emissions. However, of the 18 Earth system models that participated in ZECMIP only two included a representation of the permafrost carbon feedback to climate change. To better assess the potential impact of permafrost carbon decay on ZEC a series of perturbed parameter experiments are here conducted with an Earth system model of intermediate complexity. The experiment suggest that the permafrost carbon cycle feedback will directly add 0.06 [0.02 to 0.14] °C to the benchmark ZEC value assesses 50 years after 1000 PgC of CO₂ has been emitted to the atmosphere. An additional 0.04 [0 to 0.06] °C is likely to been added relative to the benchmark ZEC value from the thaw-lag effect unaccounted for in the ZECMIP experiment design. Overall we assess that the permafrost carbon feedback is unlikely to change the assessment that ZEC is close to zero on decadal timescales, however the feedback is expected to become more important over the coming centuries.

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多年冻土碳反馈对气候变化的零排放承诺的估计影响

摘要。零排放承诺模型（ZECMIP）最近评估了零排放承诺（ZEC），这是由于停止CO ₂排放而导致的全球温度的预期变化。ZECMIP得出结论，CO _2中的ZEC成分停止排放后的几十年内，排放量可能接近于零。但是，在参与ZECMIP的18个地球系统模型中，只有两个模型表示了对气候变化的多年冻土碳反馈。为了更好地评估多年冻土碳衰减对ZEC的潜在影响，此处使用中等复杂程度的地球系统模型进行了一系列扰动参数实验。实验表明，多年冻土层的碳循环反馈将直接将基准ZEC值增加0.06 [0.02至0.14]°C，这是在1000 PgC的CO ₂ 50年后评估的已经排放到大气中了。相对于基准ZEC值，可能由于ZECMIP实验设计中未考虑的解冻滞后效应而增加了0.04 [0至0.06]°C。总体而言，我们评估了多年冻土碳反馈不太可能改变以十年为单位的ZEC接近于零的评估，但是预计反馈在未来几个世纪中将变得越来越重要。