Drivers Of Change In mid-Latitude weather Events (DOCILE)

气候变化的外部驱动因素在中纬度天气事件中的作用，特别是人类对气候的影响，引起了科学、政策和公众的强烈兴趣。2014年2月，英国首相表示，他“怀疑”当时的洪水与人为气候变化之间存在联系，但令人沮丧的是，科学界一直无法提供更量化的评估。量化气候变化在极端天气事件中的作用也具有财政意义：目前，与影响有关的气候变化将主要通过极端事件的变化来感受。虽然缓慢发生的过程可以加剧（或减轻）个别天气事件的影响，但这些事件本身发生概率的任何变化都可能压倒这种影响。虽然这是一个已知的问题，但人们对这种发生概率变化的幅度知之甚少，这是该项目旨在解决的一个重要知识空白。联合国气候变化框架公约2015年巴黎协定呼吁研究全球气温上升1.5摄氏度与2摄氏度的影响，2018年IPCC特别报告。几乎没有中纬度天气事件可以明确地归因于外部气候驱动因素，因为如果没有这些驱动因素，这些事件根本不会发生。因此，任何对人为气候变化和未来不同程度变暖的成本的全面评估都必须量化极端天气风险变化的影响，包括相对“普通”事件风险的微妙变化。长期以来，人们一直注意到人类对气候的影响可能会影响到导致中纬度极端天气的动力系统的占有率，但直到最近才开始出现关于可归因于系统占有率变化的初步报告。最近的一个例子是2014年英国南部的洪水，人们认为洪水的发生不是因为个别的大雨，而是因为一个更持久的喷气式飞机。量化这种变化提出了一个挑战，因为高大气分辨率是现实模拟的过程，引起天气制度，而大的合奏需要量化微妙的，但可能是重要的变化，政权占用统计和事件频率。在这个项目下，我们建议，第一次，应用一个完善的大集合的方法，允许明确模拟不断变化的事件概率的全球季节性预测分辨率模型。我们的目标是回答以下问题：在欧洲，动力响应人类对气候的影响，通过改变占用的流通制度和事件频率，加剧或抵消的热力学响应，这主要是通过增加可用的水分和能量在个别事件的表现？我们的重点是比较当今的条件与没有人类对气候影响的反事实“世界可能”，并比较1.5度和2度的未来情景。虽然较高的强迫提供了较高的信噪比，但由于驱动因素的变化和非线性响应的可能性，解释变得复杂。我们用前所未有的大合奏来补偿较低的信号。事件归因已被WCRP确认为任何综合气候服务方案的关键组成部分。到目前为止，NERC科学在其发展中发挥了重要作用：该项目将把归因研究纳入更广泛的了解中纬度天气动态的议程。

The role of external drivers of climate change in mid-latitude weather events, particularly that of human influence on climate, arouses intense scientific, policy and public interest. In February 2014, the UK Prime Minister stated he "suspected a link" between the flooding at the time and anthropogenic climate change, but the scientific community was, and remains, frustratingly unable to provide a more quantitative assessment. Quantifying the role of climate change in extreme weather events has financial significance as well: at present, impact-relevant climate change will be primarily felt through changes in extreme events. While slow-onset processes can exacerbate (or ameliorate) the impact of individual weather events, any change in the probability of occurrence of these events themselves could overwhelm this effect. While this is known to be a problem, very little is known about the magnitude of such changes in occurrence probabilities, an important knowledge gap this project aims to address.The 2015 Paris Agreement of the UNFCCC has given renewed urgency to understanding relatively subtle changes in extreme weather through its call for research into the impacts of a 1.5oC versus 2oC increase in global temperatures, to contribute to an IPCC Special Report in 2018. Few, if any, mid-latitude weather events can be unambiguously attributed to external climate drivers in the sense that these events would not have happened at all without those drivers. Hence any comprehensive assessment of the cost of anthropogenic climate change and different levels of warming in the future must quantify the impact of changing risks of extreme weather, including subtle changes in the risks of relatively 'ordinary' events. The potential, and significance, of human influence on climate affecting the occupancy of the dynamical regimes that give rise to extreme weather in mid-latitudes has long been noted, but only recently have the first tentative reports of an attributable change in regime occupancy begun to emerge. A recent example is the 2014 floods in the Southern UK, which are thought to have occurred not because of individually heavy downpours, but because of a more persistent jet. Quantifying such changes presents a challenge because high atmospheric resolution is required for realistic simulation of the processes that give rise to weather regimes, while large ensembles are required to quantify subtle but potentially important changes in regime occupancy statistics and event frequency. Under this project we propose, for the first time, to apply a well-established large-ensemble methodology that allows explicit simulation of changing event probabilities to a global seasonal-forecast-resolution model. We aim to answer the following question: over Europe, does the dynamical response to human influence on climate, manifest through changing occupancy of circulation regimes and event frequency, exacerbate or counteract the thermodynamic response, which is primarily manifest through increased available moisture and energy in individual events?Our focus is on comparing present-day conditions with the counterfactual "world that might have been" without human influence on climate, and comparing 1.5 degree and 2 degree future scenarios. While higher forcing provides higher signal-to-noise, interpretation is complicated by changing drivers and the potential for a non-linear response. We compensate for a lower signal with unprecedentedly large ensembles. Event attribution has been recognised by the WCRP as a key component of any comprehensive package of climate services. NERC science has been instrumental in its development so far: this project will provide a long-overdue integration of attribution research into the broader agenda of understanding the dynamics of mid-latitude weather.