Attributing Historical and Future Evolution of Radiative Feedbacks to Regional Warming Patterns using a Green's Function Approach: The Preeminence of the Western Pacific
Attributing Historical and Future Evolution of Radiative Feedbacks to Regional Warming Patterns using a Green's Function Approach: The Preeminence of the Western Pacific
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DOI：
10.1175/jcli-d-18-0843.1
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发表时间：
2019-09-01
影响因子：
4.9
通讯作者：
Battisti, David S.
中科院分区：
文献类型：
--
作者：
Dong, Yue;Proistosescu, Cristian;Battisti, David S.
在全球气候模式（GCM）模拟中发现全球辐射反馈存在变化。近几十年来，由海表温度和海冰浓度的历史模式驱动的大气GCMs （AGCMs）产生的辐射反馈趋向于负值，这意味着低气候敏感性。在CO2增加的驱动下，自由演化的耦合gcm产生的辐射反馈趋向于更正的值，这意味着未来气候敏感性的增加。虽然反馈的这种时间变化与海温模式的演变有关，但特定区域的作用尚未被量化。这里，格林函数是从AGCM （NCAR的CAM4）内的一套模拟中推导出来的，允许将全球反馈变化归因于每个地区的地表变暖。结果表明，西热带太平洋上升区对地表变暖的辐射响应是全球辐射反馈变化的主要控制因素。从1950年代到2000年代的历史变暖优先发生在西太平洋，在大气顶部产生强烈的全球外向辐射响应（TOA），从而产生强烈的全球负反馈。耦合gcm的长期变暖优先发生在热带下降区和高纬度地区，在这些地区，地表变暖产生的全球TOA辐射变化较小，但全球地表气温变化较大，因此全球负反馈较小。这些结果阐明了确定暖池变暖机制对于理解反馈在历史上如何变化以及未来将如何演变的重要性。
Global radiative feedbacks have been found to vary in global climate model (GCM) simulations. Atmospheric GCMs (AGCMs) driven with historical patterns of sea surface temperatures (SSTs) and sea ice concentrations produce radiative feedbacks that trend toward more negative values, implying low climate sensitivity, over recent decades. Freely evolving coupled GCMs driven by increasing CO2 produce radiative feedbacks that trend toward more positive values, implying increasing climate sensitivity, in the future. While this time variation in feedbacks has been linked to evolving SST patterns, the role of particular regions has not been quantified. Here, a Green's function is derived from a suite of simulations within an AGCM (NCAR's CAM4), allowing an attribution of global feedback changes to surface warming in each region. The results highlight the radiative response to surface warming in ascent regions of the western tropical Pacific as the dominant control on global radiative feedback changes. Historical warming from the 1950s to 2000s preferentially occurred in the western Pacific, yielding a strong global outgoing radiative response at the top of the atmosphere (TOA) and thus a strongly negative global feedback. Long-term warming in coupled GCMs occurs preferentially in tropical descent regions and in high latitudes, where surface warming yields small global TOA radiation change but large global surface air temperature change, and thus a less-negative global feedback. These results illuminate the importance of determining mechanisms of warm pool warming for understanding how feedbacks have varied historically and will evolve in the future.