The projected loss of soil carbon to the atmosphere resulting from climate change is a potentially large but highly uncertain feedback to warming. The magnitude of this feedback is poorly constrained by observations and theory, and is disparately represented in Earth system models (ESMs)^1,2,3. To assess the climatological temperature sensitivity of soil carbon, we calculate apparent soil carbon turnover times⁴ that reflect long-term and broad-scale rates of decomposition. Here, we show that the climatological temperature control on carbon turnover in the top metre of global soils is more sensitive in cold climates than in warm climates and argue that it is critical to capture this emergent ecosystem property in global-scale models. We present a simplified model that explains the observed high cold-climate sensitivity using only the physical scaling of soil freeze–thaw state across climate gradients. Current ESMs fail to capture this pattern, except in an ESM that explicitly resolves vertical gradients in soil climate and carbon turnover. An observed weak tropical temperature sensitivity emerges in a different model that explicitly resolves mineralogical control on decomposition. These results support projections of strong carbon–climate feedbacks from northern soils^5,6 and demonstrate a method for ESMs to capture this emergent behaviour.

预计气候变化导致土壤碳向大气的损失可能是对变暖的潜在巨大但高度不确定的反馈。这种反馈的强度几乎不受观测和理论的约束，在地球系统模型（ESMs）^1,2,3中有不同的表示。为了评估土壤碳的气候温度敏感性，我们计算了表观土壤碳周转时间⁴反映了长期和大规模的分解率。在这里，我们表明，全球土壤最高层的碳转换的气候温度控制在寒冷气候下比在温暖气候下更为敏感，并指出在全球尺度的模型中捕获这种新兴的生态系统特性至关重要。我们提供了一个简化的模型，该模型仅使用跨气候梯度的土壤冻融状态的物理比例来解释观测到的高冷气候敏感性。当前的ESM无法捕获这种模式，除非在ESM中可以明确解决土壤气候和碳周转的垂直梯度。在不同的模型中出现了观测到的弱热带温度敏感性，该模型明确解决了分解的矿物学控制。^5,6并演示了ESM捕获这种紧急行为的方法。