The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental consequences of an atmospheric CO₂ concentration near ∼400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resolution based on new reconstructions of boundary conditions (the Pliocene Model Intercomparison Project Phase 2; PlioMIP2). As a global annual average, modelled surface air temperatures increase by between 1.7 and 5.2 ^∘C relative to the pre-industrial era with a multi-model mean value of 3.2 ^∘C. Annual mean total precipitation rates increase by 7 % (range: 2 %–13 %). On average, surface air temperature (SAT) increases by 4.3 ^∘C over land and 2.8 ^∘C over the oceans. There is a clear pattern of polar amplification with warming polewards of 60^∘ N and 60^∘ S exceeding the global mean warming by a factor of 2.3. In the Atlantic and Pacific oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. There is a statistically significant relationship between a model's climate response associated with a doubling in CO₂ (equilibrium climate sensitivity; ECS) and its simulated Pliocene surface temperature response. The mean ensemble Earth system response to a doubling of CO₂ (including ice sheet feedbacks) is 67 % greater than ECS; this is larger than the increase of 47 % obtained from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea surface temperatures are used to assess model estimates of ECS and give an ECS range of 2.6–4.8 ^∘C. This result is in general accord with the ECS range presented by previous Intergovernmental Panel on Climate Change (IPCC) Assessment Reports.

中文翻译：

---

上新世模式比对项目第二阶段：大规模气候特征和气候敏感性

上新世时代具有很大的潜力，可以使我们更好地理解大气中的CO ₂浓度接近百万分之400的体积对长期气候和环境的影响。在这里，我们介绍了上新世气候的大规模特征，该新特征是通过基于复杂的边界条件的新重建（上新世模型比对项目第二阶段； PlioMIP2）的具有不同复杂性和空间分辨率的新气候模型集合来模拟的。作为全球年平均数，模拟的地表气温相对于工业化前时代增加了1.7至 ^5.2∘C，多模式平均值为 ^3.2∘CC.年平均总降水量增加7％（范围：2％–13％）。平均而言，由4.3表面空气温度（SAT）的增加 ^∘土地C和2.8  ^∘下在海洋。有一个清晰的极性放大模式，其极地暖分别为^60∘N 和^60∘S  ，比全球平均升温高2.3倍。在大西洋和太平洋，子午温度梯度减小，而热带纬向梯度基本保持不变。与CO ₂倍增相关的模型的气候响应之间存在统计上的显着关系（平衡气候敏感性； ECS）及其模拟的上新世表面温度响应。整体地球系统对CO ₂倍增（包括冰盖反馈）的响应比ECS大67％；这比从PlioMIP1集成获得的47％的增长要大。上新世海洋表面温度的代理衍生估计被用来评估ECS的模型估计值，并给2.6-4.8的范围ECS  ^∘ C.该结果与ECS基本一致范围由以前的政府间气候变化专门委员会（IPCC）呈现评估报告。