Reconstructing Earth Energy Imbalance

地球大气层顶部的净能量平衡对于气候科学中的许多重要问题至关重要(例如，气候对温室气体浓度变化的敏感性以及大气和海洋之间的相互作用模式)。尽管发挥着核心作用，但地球的能源收支只是在过去20年里才得到很好的观察。这种短时间的直接观测为评估有关气候变异性的重要问题留下了有限的样本，特别是在区分气候系统的外部强迫变异性和内部变异性方面。虽然可以使用气候模型来解决这些问题，但古气候指标提供了仪器时代之前气候信息的唯一编码，因此对于量化气候变异性，特别是地球在年际、年代际和更长时间尺度上的能量不平衡至关重要。该项目建议使用古气候数据同化(PDA)方法重建过去1000年的地球能量收支。这种方法结合了来自古气候代理的信息和气候模型的物理约束，以重建代理没有直接观测到的气候场。这项拟议的研究利用了最近的数值模拟和初步概念验证计算来实现这种重建。具体地说，研究人员将使用离线PDA和在线PDA，其中长期气候模式模拟的静态统计数据用于提供物理约束，而在线PDA则在计算效率上高效的气候模型模拟器为早期的代理重建增加动态“记忆”。研究人员的目标是在大气层顶部构建传出的短波和长波辐射，并根据海洋热含量进行存储。然后，这些重建将被用来解决关于海表面温度可变性的空间模式与能量不平衡之间的关系的假设。该项目将提供对地球能量不平衡的代理约束估计，包括海洋热含量和大气顶部辐射不平衡。一系列验证实验，使用卫星测量、仪器测量和历史模拟，将为这些估计提供置信限。拟议的研究直接涉及气候科学中的重要未决问题，包括气候敏感性所需的工业化前能源不平衡，以及太平洋温度变化模式对全球能源不平衡的贡献。潜在的更广泛的影响包括合成古气候指标的网格数据产品和大气层顶部能量不平衡的模型数据。这种千禧年网格尺度的重建将向广泛的古气候界公开提供，用于广泛的气候研究，包括探测和归属研究。这项工作将支持华盛顿大学一名研究生的科学培训和专业发展。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The net energy balance at the top of Earth’s atmosphere is critical for many important problems in climate science (e.g., climate sensitivity to changing greenhouse gas concentrations and modes of interaction between the atmosphere and ocean). Despite this central role, Earth’s energy budget has only been well observed for about the past 20 years. This short period of direct observation leaves a limited sample for evaluating important questions about climate variability, especially for distinguishing between variability that is externally forced versus internal to the climate system. While these questions can be approached using climate models, paleoclimate proxies provide the only encoding of climate information before the instrumental era, and thus are essential for quantifying climate variability, and particularly Earth’s energy imbalance on interannual, decadal and longer timescales. This project proposes to reconstruct Earth’s energy budget for the past 1000 years using paleoclimate data assimilation (PDA) method. This approach combines information from paleoclimate proxies with the physical constraints of climate models to reconstruct climate fields that are not directly observed by the proxies. The proposed research takes advantages of recent numerical simulations and preliminary-proof-of concept calculations to achieve this reconstruction.Specifically, the researchers will use an offline PDA, where the stationary statistics of long climate model simulations are used to supply physical constraints, and online PDA, where computationally efficient emulators of the climate models add dynamical “memory” to the reconstructions from proxies at earlier times. The researchers aim to construct outgoing shortwave and longwave radiation at the top of the atmosphere, and storage in terms of ocean heat content. The reconstructions will then be used to address a hypothesis on the relationship between spatial patterns of sea-surface temperature variability and energy imbalance. This project will provide a proxy-constrained estimate of Earth’s energy imbalance, both in ocean heat content and in the top-of-atmosphere radiative imbalance. A hierarchy of validation experiments, using satellite measurements, instrumental measurements, and historical simulations will provide confidence bounds on these estimates. The proposed research directly addresses important open problems in climate science, including pre-industrial energy imbalance needed for climate sensitivity, and the contribution of patterns of Pacific temperature variability to the planetary energy imbalance. The potential Broader Impacts include a gridded data product synthesizing paleoclimate proxy and model data for the top-of-atmosphere energy imbalance. Such a gridded millennial scale reconstruction will be made publicly available to the wide paleoclimate community for a widespread climate research, including detection and attribution-studies. This work will support the scientific training and professional development of one graduate student at the University of Washington.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.