New framework to understand mechanisms of land-ocean warming contrast induced by increasing greenhouse gases. Part II: Transient climate state.
New framework to understand mechanisms of land-ocean warming contrast induced by increasing greenhouse gases. Part II: Transient climate state.
复制标题
了解温室气体增加引起的陆地-海洋变暖对比机制的新框架。
DOI：
10.1175/jcli-d-22-0483.1
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发表时间：
2023
影响因子：
4.9
通讯作者：
and M. Watanabe
中科院分区：
文献类型：
--
作者：
Toda;M.;M. Yoshimori;and M. Watanabe
我们研究了陆地-海洋变暖对比机制，ϕ，定义为陆地平均地表气温变化除以海洋平均地面气温变化，从耦合模式比较项目第六阶段(CMIP6)每年1%的二氧化碳增加实验(1pctCO2)获得的瞬时气候响应(TCR)。第一部分中设计的能量收支框架被应用于15个CMIP6 1pctCO2模拟，并将140年CO2浓度翻两番时的气候响应与近平衡气候响应(NEQ)进行了比较，NEQ定义为CO2突然翻两番(4×CO2)实验中最后30年的平均值。结果表明，TCR的ϕ比NEQ大约4%，但差异不显著。与海洋相比，陆地上的有效辐射强迫更大，这是ϕ的主要贡献者。利用突发性4×ϕ气候响应的快慢分量可以重建1pctCO2中Tcr的时间演变，表明第一部分中所揭示的海陆变暖对比的基本机制也适用于Tcr。此外，我们的分析显示，陆地到海洋的大气能量传输减少了ϕ，而海洋的热量吸收增加了ϕ。无论响应的时间尺度如何，这两个过程都通过大气环流的变化联系在一起，导致了小的综合效应。结果表明，尽管CO2浓度持续增加，但1ptCO2中的多模式平均ϕ大致保持在1.5时不变。陆地-海洋变暖对比表明，与海洋表面变暖相比，陆地表面变暖是对大气CO2浓度增加的响应，这是人类导致全球变暖的一个显著特征。这项研究集中在瞬变气候变化模拟中陆地-海洋变暖对比大小的时间变化，并表明陆地-海洋变暖对比的大小随着时间的推移几乎是恒定的，陆地和海洋表面变暖的比率保持在大约1.5。这种微小的时间变化主要是由于陆地到海洋的能量传输和海洋热量吸收之间的补偿，因为两者与陆地-海洋变暖的对比是相反的。
We investigate the land–ocean warming contrast mechanisms,ϕ, defined as the land-mean surface air temperature (SAT) change divided by the ocean-mean SAT change, in a transient climate response (TCR) obtained from the Coupled Model Intercomparison Project phase 6 (CMIP6) 1% per year CO2increase experiments (1pctCO2). The energy budget framework devised in Part I is applied to 15 CMIP6 1pctCO2simulations, and the climate response in year 140 when the CO2concentration was quadrupled was compared with a near-equilibrium climate response (NEQ), defined as the last 30-yr mean in the abrupt CO2quadrupling (abrupt4×CO2) experiments. It is shown thatϕis larger in TCR than in NEQ by approximately 4%, although the difference is not statistically significant. In TCR, effective radiative forcing is large over land compared to the ocean, and this is the main contributor toϕas in NEQ. The time evolution ofϕin 1pctCO2can be reconstructed by means of the fast and slow components of climate response in abrupt4×CO2, indicating that the essential mechanism for the land–ocean warming contrast shown in Part I applies to TCR. Furthermore, our analyses reveal a compensation between land-to-ocean atmospheric energy transport that decreasesϕand ocean heat uptake that increasesϕ. Regardless of the time scale of the response, these two processes are linked by the change in atmospheric circulation, leading to the small combined effect. As a result, the multimodel meanϕin 1pctCO2is roughly time invariant at approximately 1.5 despite the continuous increase in CO2.Significance StatementThe land–ocean warming contrast, which indicates large land surface warming compared to ocean surface warming in response to an increase in atmospheric CO2concentration, is a striking feature of human-induced global warming. This study focuses on temporal changes in the magnitude of the land–ocean warming contrast in transient climate change simulations and shows that the magnitude of the land–ocean warming contrast is nearly constant over time, maintaining a ratio of approximately 1.5, between land and ocean surface warming. This small temporal change is explained mainly by a compensation between land-to-ocean energy transport and ocean heat uptake, because both act in opposite directions to the land–ocean warming contrast.