CAREER: Understanding Cloud Feedback and Natural Aerosol Fingerprints to Interpret Past Warm Climate Forcing and Constrain Tropical Climate Sensitivity

职业：了解云反馈和自然气溶胶指纹，以解释过去温暖的气候强迫和限制热带气候敏感性

• 批准号: 1844380
• 负责人: Natalie Burls
• 金额: $ 81.42万
• 依托单位: George Mason University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1844380&HistoricalAwards=false
• 关键词: CAREER; Understanding; Cloud; Feedback; Natural

Equilibrium climate sensitivity refers to as the average surface temperature change of the planet in response to a change in external forcing (e.g., the doubling of the atmospheric CO2 concentration) once the climate system has reached a balanced state. Equilibrium climate sensitivity is a central concept in climate science for estimating the future temperature under the scenario of a continuous increase of atmospheric CO2 concentration using climate models, as a large portion of the total climate warming results from other changes in the climate system in response to the radiative forcing due to anthropogenic greenhouse gas emissions, such as clouds, atmospheric moisture, and snow/ice coverage. The research has broader societal impacts as the central goal of this study is to understand the fundamental physical mechanisms that have controlled tropical climate and how it responds to warming. This is of significant practical value in establishing confidence in the ability of climate models to capture tropical feedbacks under future warming. This award will support the careers and training of the PI (an early career female scientist), a graduate student, and a postdoctoral fellow. The PI will work with Geology graduate students through summer research visits and development of a website for students/researchers from across the country to access and analyze paleoclimate model data. She will mentor local undergraduate and high school students through George Mason's Aspiring Scientists Summer Internship Program and present a "weather and climate" module at a George Mason summer camp designed for females underrepresented in fields of science, technology, engineering, and mathematics. Constraining the range of climate sensitivity estimates beyond those established over the last three decades has proven to be one of the grand challenges in climate science. The limited timespan of the instrumental record makes it difficult to tease out natural, decadal-plus variability from cloud feedbacks in response to greenhouse gas induced warming, with signals further complicated by 20th century aerosol forcing. This project will take a new approach towards constraining the nature of cloud feedbacks under warming by examining climate sensitivities in past warm periods of paleo climate records. The current climate models lack ability to adequately reproduce the reduced meridional surface temperature gradients reconstructed for the past three warm climates, namely, the Pliocene, Miocene and Eocene, as constrained by large-scale surface temperature and hydrological cycle reconstructions. The PI will seek answer about the required strength of the climate sensitivity, particularly from tropical cloud radiative feedback, for climate models to simulate these three very different past warm periods. This multi-warm-climate approach will help establish the extent to which robust tropical cloud feedback mechanisms can consistently explain the patterns of warming, and the hydrological cycle response, seen across the 20th century, Pliocene, Miocene and Eocene. The research project will integrate the latest scientific advances within both the climate modeling and paleoclimate reconstruction communities to: 1) address a fundamental gap in our understanding of the tropical feedbacks needed to simulate distinct past warm climates and the extent to which they are consistent across warm periods, and 2) test the robustness of climate mechanisms put forth within the paleoclimate community to aid in the interpretation and design of climate reconstructions.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.

平衡气候敏感性是指地球平均表面温度变化对外部强迫变化的响应（例如，一旦气候系统达到平衡状态，大气中二氧化碳浓度就会增加一倍。平衡气候敏感性是气候科学中的一个核心概念，用于使用气候模式估计大气CO2浓度持续增加情景下的未来温度，因为总气候变暖的很大一部分是由气候系统中的其他变化引起的，这些变化是对人为温室气体排放造成的辐射强迫的响应，例如云，大气湿度和雪/冰覆盖。这项研究具有更广泛的社会影响，因为这项研究的中心目标是了解控制热带气候的基本物理机制以及它如何应对变暖。这在建立对气候模型在未来变暖情况下捕捉热带反馈的能力的信心方面具有重要的实用价值。该奖项将支持PI（早期职业女性科学家），研究生和博士后研究员的职业和培训。PI将与地质学研究生合作，通过夏季研究访问和开发一个网站，供来自全国各地的学生/研究人员访问和分析古气候模型数据。她将通过乔治梅森的有抱负的科学家暑期实习计划指导当地的本科生和高中生，并在乔治梅森夏令营为科学，技术，工程和数学领域的女性设计的“天气和气候”模块。 事实证明，将气候敏感性估计的范围限制在过去三十年建立的范围之外，是气候科学面临的重大挑战之一。仪器记录的时间跨度有限，因此很难从云反馈中梳理出自然的、十年以上的变化，以响应温室气体引起的变暖，世纪气溶胶强迫使信号进一步复杂化。该项目将采取一种新的方法，通过检查古气候记录中过去温暖时期的气候敏感性来限制变暖下云反馈的性质。由于受到大尺度地表温度和水文循环重建的限制，目前的气候模式无法充分再现过去三个温暖气候时期（即上新世、中新世和始新世）的经向地表温度梯度。PI将寻求关于气候敏感性所需强度的答案，特别是来自热带云辐射反馈的答案，以便气候模型模拟这三个非常不同的过去温暖时期。这种多温暖气候的方法将有助于建立强大的热带云反馈机制在多大程度上可以始终如一地解释变暖的模式，以及整个世纪，上新世，中新世和始新世的水文循环响应。该研究项目将整合气候建模和古气候重建领域的最新科学进展，以：1）解决我们对模拟不同的过去温暖气候所需的热带反馈的理解的根本差距，以及它们在温暖时期的一致程度，和2）测试古气候学界提出的气候机制的稳健性，以帮助解释和设计气候重建。该奖项反映了NSF的法定使命并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Sustained mid-Pliocene warmth led to deep water formation in the North Pacific

• DOI: 10.1038/s41561-022-00978-3
• 发表时间: 2022-07
• 期刊: Nature Geoscience
• 影响因子: 18.3
• 作者: H. Ford;N. Burls;P. Jacobs;A. Jahn;R. Caballero-Gill;D. Hodell;A. Fedorov

Pliocene decoupling of equatorial Pacific temperature and pH gradients

• DOI: 10.1038/s41586-021-03884-7
• 发表时间: 2021-10
• 期刊: Nature
• 影响因子: 64.8
• 作者: M. Shankle;N. Burls;A. Fedorov;M. Thomas;Wei Liu;D. Penman;H. Ford;Peter H Jacobs;N. Planavsky-N.

Evaluating the large-scale hydrological cycle response within the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble

• DOI: 10.5194/cp-17-2537-2021
• 发表时间: 2021-12
• 期刊: Climate of the Past
• 影响因子: 4.3
• 作者: Zixuan Han;Qiong Zhang;Qiang Li;R. Feng;A. Haywood;J. Tindall;S. Hunter;B. Otto‐Bliesner

Time Scales and Mechanisms for the Tropical Pacific Response to Global Warming: A Tug of War between the Ocean Thermostat and Weaker Walker

• DOI: 10.1175/jcli-d-19-0690.1
• 发表时间: 2020-07-15
• 期刊: JOURNAL OF CLIMATE
• 影响因子: 4.9
• 作者: Heede, Ulla K.;Fedorov, Alexey, V;Burls, Natalie J.
• 通讯作者: Burls, Natalie J.

A stronger versus weaker Walker: understanding model differences in fast and slow tropical Pacific responses to global warming

• DOI: 10.1007/s00382-021-05818-5
• 发表时间: 2021-05-29
• 期刊: CLIMATE DYNAMICS
• 影响因子: 4.6
• 作者: Heede, Ulla K.;Fedorov, Alexey, V;Burls, Natalie J.
• 通讯作者: Burls, Natalie J.