Collaborative Research: Non-Linearity and Feedbacks in the Atmospheric Circulation Response to Increased Carbon Dioxide (CO2)

合作研究：大气环流对二氧化碳 (CO2) 增加的响应的非线性和反馈

• 批准号: 2335762
• 负责人: Lorenzo Polvani
• 金额: $ 54.7万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-06-01 至 2027-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2335762&HistoricalAwards=false
• 关键词: Collaborative; Research; Non; Linearity; Feedbacks; Collaborative; Research; Non; Linearity; Feedbacks

Efforts to address climate change begin with the simple fact that adding carbon dioxide (CO2) to the atmosphere warms the globe. But the consequences of greenhouse warming that matter for people are regional rather than global and involve other factors besides temperature. One such factor is warming-induced change in atmospheric circulation, which can, for example, cause some regions to dry out while others become more flood prone. The importance of circulation change for regional climate challenges efforts to address climate impacts since the dynamical mechanisms through which warming induces circulation change are not well understood, and model simulations used to inform decision making do not show strong agreement as to how much circulation change will occur. A further consideration is that the amount of circulation change is not necessarily proportional to the amount of global temperature increase. Previous work by the Principal Investigators (PIs) of this project found several examples of nonlinear behavior, for instance the strength of the Northern Hemisphere Hadley Cell (the overturning cell with rising motion near the equator and subsidence over the Northern subtropics) decreases for a doubling of CO2 but increases if CO2 is further increased to a tripling.Work under this award seeks to understand the circulation response to CO2 increase, focusing specifically on the reasons for differences in circulation change from one climate model to another and the mechanisms responsible for nonlinearity in circulation change. One mechanism for nonlinearity is the rapid weakening of the Atlantic Meridional Overturning Circulation (AMOC), which occurs at a particular level of CO2 increase and causes circulation change by creating a patch of colder sea surface temperatures in the North Atlantic. The rapid weakening of the AMOC happens at different CO2 levels in different climate models and is thus a source of inter-model spread in circulation change. Another mechanism is CO2-induced change in stratospheric ozone, as CO2 increase affects the amount and latitudinal distribution of stratospheric ozone, which in turn can influence the jet stream because ozone causes radiative heating which produces upper-level temperature contrasts. The CO2-ozone feedback, in which CO2 influences temperature which in turn affects ozone causing further temperature change, has only recently been recognized as a contributing factor to climate and circulation change. The research is conducted through analysis of model simulations available through several Model Intercomparison Projects, along with new simulations generated using the Community Earth System Model (CESM) and the climate model of the Goddard Institute for Space Studies (GISS Model E2.2).The work is of societal as well as scientific interest given the influence of circulation change on regional climate change, as noted above. A related consideration is that assessments of regional climate change often assume that regional climate changes will be proportional to global temperature increase, thus research on the nonlinearity of circulation change has direct bearing on regional climate change assessments. The PIs are well positioned to disseminate their results to the climate impacts community as both have been authors on previous assessments including reports of the Intergovernmental Panel on Climate Change and the World Meteorological Organization. In addition, the PIs participate in outreach programs within their communities including the Baltimore Ingenuity Project (IP), and the work provides support and training to two graduate students.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.

解决气候变化的努力始于一个简单的事实，即在大气中添加二氧化碳（CO2）会使地球温暖。 但是，对人们至关重要的温室变暖的后果是区域性的，而不是全球，除了温度以外，还涉及其他因素。 这样的因素之一是变暖引起的大气循环变化，例如，这可能导致某些地区变干，而另一些地区则更容易发生洪水。循环变化对区域气候挑战的重要性为解决气候影响而努力，因为尚未充分理解变暖引起循环变化的动力学机制，并且用于告知决策的模型模拟并未对发生多少循环变化表示强烈的共识。 另一个考虑因素是，循环变化的量不一定与全球温度升高成正比。 首席研究人员（PIS）先前对该项目的工作发现了几个非线性行为的例子，例如，北半球的强度（在赤道附近的倾斜运动和北部亚热带的沉降）下降的北半球强度会减少CO2的重复，但如果CO2的重点增加到循环均增加了循环，则需要提高循环的范围。在循环中，从一个气候模型变为另一种气候模型以及导致循环变化非线性的机制。 非线性的一种机制是大西洋子午倾覆（AMOC）的迅速削弱，该机制在特定二氧化碳水平上增加，并通过在北大西洋上产生较冷的海面温度来引起循环变化。 在不同气候模型中，AMOC的快速削弱在不同的CO2水平上发生，因此是循环变化中模型间扩散的来源。 另一个机制是二氧化碳诱导的平流层臭氧的变化，因为二氧化碳的增加会影响平流层臭氧的量和纬度分布，这反过来又会影响喷气流，因为臭氧会导致辐射加热，从而产生高级温度对比。 二氧化碳反馈会影响温度，这反过来影响臭氧导致进一步的温度变化，直到最近才被认为是气候和循环变化的促成因素。 这项研究是通过分析通过几个模型对比项目获得的模型模拟进行的，以及使用社区地球系统模型（CESM）生成的新仿真以及戈达德太空研究所的气候模型（GISS模型E2.2）。鉴于上文所述，鉴于区域气候变化的影响对循环的影响以及循环的影响，这项工作均具有社会利益以及科学利益。 一个相关的考虑是，对区域气候变化的评估通常认为区域气候变化将与全球温度升高成正比，因此对循环变化非线性的研究直接与区域气候变化评估有关。 PI在气候影响社区中的良好位置可以将其结果传播到以前的评估中，包括有关气候变化间政府间小组和世界气象组织的报道的作者。 此外，PIS还参加了社区内的推广计划，包括巴尔的摩Ingenuity Project（IP），这项工作为两名研究生提供了支持和培训。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的审查标准通过评估来通过评估来获得支持的。