VOLCANIC CLASSIC: VOLCANIC eruptions and CLimAte response - Stratospheric Sulfate isotopes in Ice Cores, data assimilation, and climate sensitivity

地球的气候如何应对扰动？尽管经过数十年的努力，这个基本问题仍然难以回答，在最先进的模型中，气候对外部强迫的敏感性范围很广。为了更好地了解气候系统，缩小未来气候预测的不确定性范围，需要采取创新的新办法。在这里，我提出了一个新的战略，将提供独特的新的测试气候模型和紧急约束气候敏感性，通过利用重大火山爆发的记录。火山爆发对气候产生巨大的影响，因为它们的硫酸盐气溶胶反射入射的阳光，驱动突然冷却的时间尺度为1-5年。然而，我们阅读这一记录的能力目前受到火山作用力（火山爆发对入射辐射的影响-主要是平流层硫酸盐的作用）和全球气候反应的不确定性的限制。通过使用尖端的新技术来测量冰芯中的硫同位素，我将独特地限制平流层硫酸盐和喷发纬度和季节，改变过去火山强迫的知识。我将把它与新的和改进的全球气候响应重建进行比较，通过将新的全球分布的古气候记录纳入模型数据同化产品来实现。通过研究气候对过去2000年233次主要火山爆发的反应，我将提供火山气候敏感性的强有力的观测约束。我将用这些来测试最先进的气候模型的敏感性和反馈。这些测试将为理解当前模型中对气溶胶的广泛敏感性以及对有争议的地球工程方案的辩论提供信息。由于模型对火山和二氧化碳的反应是相互联系的，这项工作最终将用于改进对二氧化碳上升的敏感性范围，并改进对未来气候的预测。

How does Earth's climate respond to perturbation? Despite decades of work, this fundamental question remains difficult to answer, with a wide range of climate sensitivities to external forcing persisting in state-of-the-art models. To improve understanding of the climate system and narrow the range of uncertainties in future climate projections, innovative new approaches are required. Here I propose a novel strategy that will provide unique new tests of climate models and emergent constraints on climate sensitivity, by harnessing the record of major volcanic eruptions.Volcanic eruptions exert an enormous influence on climate, as their sulfate aerosols reflect incoming sunlight, driving abrupt cooling on timescales of 1-5 years. However our ability to read this record is currently limited by uncertainties in volcanic forcing (the impact of eruptions on incoming radiation - primarily a function of stratospheric sulfate) and global climate response. By using cutting edge new technology to measure sulfur isotopes in ice cores, I will uniquely constrain stratospheric sulfate and eruption latitude and season, transforming knowledge of past volcanic forcing. I will compare this to new and improved reconstructions of global climate response, achieved by incorporating new, globally-distributed paleoclimate records into model-data assimilation products. By examining the climate response to each of the 233 major eruptions of the last 2000 years, I will provide robust observational constraints on volcanic climate sensitivity. I will use these to test sensitivity and feedbacks in state-of-the-art climate models. These tests will inform both understanding of the wide range of sensitivity to aerosols in current models and the debate on controversial geoengineering schemes. As model response to volcanoes and CO2 are linked, this work will ultimately be used to refine the range of sensitivity to CO2 rise and improve projections of future climate.