Collaborative Research: Characterizing the drivers of hydroclimate change over western North America and Europe in response to the global warmth of the middle Miocene

社会面临的一个关键问题是，随着地球气候系统对温室气体积累的反应，水资源的可用性将如何变化。为了解决这个问题，一组研究人员正在调查中新世中期的环境条件，这段时间大约在1500万年前，当时地球处于温暖的气候状态。近几十年来，美国西部和欧洲经历了干旱，据预测，随着地球变暖，这一趋势将加剧。然而，最近对中新世气候的重建表明，与过去的温暖间隔有关的是更潮湿而不是更干燥的条件。该项目旨在了解和模拟中新世温暖气候期间的降雨，以确定水的可用性如何随温度升高而变化。该合作项目支持职业生涯早期和中期的科学家在乔治梅森大学提供研究生和高中气候建模培训，在南加州大学提供研究生和本科气候重建培训。通过弗吉尼亚和宾夕法尼亚自然中心的社区讲座，以及与南加州大学传播学院和洛杉矶县自然历史博物馆中新世气候展览的合作，研究成果正在与公众分享。本研究旨在通过模型-数据整合的方法解决气候变暖中持续存在的水文气候不确定性。低分辨率气候模拟测试水文气候对海洋温度重建的响应以及对代理不确定性和覆盖的敏感性。高分辨率模拟能更好地解析北美季风和大气河流，它们对极端降水事件和随后的湿润气候状态至关重要，而不是当前和预计的干旱趋势。为了填补了解美国西部水文气候的数据空白，该项目产生了额外的海洋温度和陆地水文气候的代理重建。从地质、植物和动物记录中提取的水文气候证据被处理成一个可用的数据框架，用于与气候模型和一般科学界进行比较。这种模型代理方法阐明了我们未来气候的过程、敏感性和临界点，包括气候变暖可能导致的从干燥环境到潮湿环境的转变。该奖项反映了美国国家科学基金会的法定使命，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。

A key question facing society is how will water availability change as the Earth’s climate system responds to the accumulation of greenhouse gases. To address this question, a team of researchers are investigating the environmental conditions during the mid-Miocene, an interval around 15 million years ago, when the planet was in a warm climate state. The western US and Europe have experienced drying in recent decades, a trend that has been forecast to intensify as our planet warms. However, recent reconstructions of Miocene climate suggest wetter rather than drier conditions associated with past warm intervals. This project aims to understand and model rainfall during warm climate intervals in the Miocene to determine how water availability may change with warming temperatures. The collaborative project supports early career and mid-career scientists who provide graduate and high school traineeships for climate modeling at George Mason University and graduate and undergraduate traineeships in climate reconstruction at the University of Southern California. Research findings are being shared with the public through community lectures at nature centers in Virginia and Pennsylvania as well as via a partnership with University of Southern California’s communication school and the Natural History Museum of Los Angeles County’s Miocene climate exhibit. The research aims to resolve the persistent hydroclimate uncertainty in a warming climate with a model-data integration approach. Low-resolution climate simulations test hydroclimate response to ocean temperature reconstructions and sensitivity to proxy uncertainty and coverage. High-resolution simulations better resolve the North American Monsoon and atmospheric rivers, which critically determine extreme precipitation events and the subsequent wetter climate state than the current and projected drying trends. Aiming to fill data gaps for understanding western US hydroclimate, the project generates additional proxy reconstructions of ocean temperature and terrestrial hydroclimate. Extracted hydroclimate evidence from geological, botanical, and faunal records are processed into a usable data framework for comparison to climate models and the general scientific community. This model-proxy approach illuminates processes, sensitivities, and tipping points in our climate future, including a possible shift from a drier to wetter environment with warming.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.