Advances in the field of extreme event attribution allow to estimate how anthropogenic global warming affects the odds of individual climate disasters, such as river floods. Extreme event attribution typically uses precipitation as proxy for flooding. However, hydrological processes and antecedent conditions make the relation between precipitation and floods highly nonlinear. In addition, hydrology acknowledges that changes in floods can be strongly driven by changes in land-cover and by other human interventions in the hydrological system, such as irrigation and construction of dams. These drivers can either amplify, dampen or outweigh the effect of climate change on local flood occurrence. Neglecting these processes and drivers can lead to incorrect flood attribution. Including flooding explicitly, that is, using data and models of hydrology and hydrodynamics that can represent the relevant hydrological processes, will lead to more robust event attribution, and will account for the role of other drivers beyond climate change. Existing attempts are incomplete. We argue that the existing probabilistic framework for extreme event attribution can be extended to explicitly include floods for near-natural cases, where flood occurrence was unlikely to be influenced by land-cover change and human hydrological interventions. However, for the many cases where this assumption is not valid, a multi-driver framework for conditional event attribution needs to be established. Explicit flood attribution will have to grapple with uncertainties from lack of observations and compounding from the many processes involved. Further, it requires collaboration between climatologists and hydrologists, and promises to better address the needs of flood risk management.

中文翻译：

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河流洪水事件归因的挑战

极端事件归因领域的进展可以估计人为全球变暖如何影响个别气候灾害（例如河流洪水）的可能性。极端事件归因通常使用降水量作为洪水的替代指标。然而，水文过程和先决条件使得降水和洪水之间的关系高度非线性。此外，水文学承认，土地覆盖变化和水文系统中的其他人类干预（例如灌溉和水坝建设）可能会强烈驱动洪水的变化。这些驱动因素可以放大、抑制或抵消气候变化对当地洪水发生的影响。忽视这些过程和驱动因素可能会导致错误的洪水归因。明确包括洪水，即使用可以代表相关水文过程的水文和流体动力学数据和模型，将导致更稳健的事件归因，并将解释气候变化以外的其他驱动因素的作用。现有的尝试是不完整的。我们认为，现有的极端事件归因概率框架可以扩展到明确包括近自然情况下的洪水，其中洪水的发生不太可能受到土地覆盖变化和人类水文干预的影响。然而，对于这种假设无效的许多情况，需要建立一个用于条件事件归因的多驱动框架。明确的洪水归因必须解决由于缺乏观察和涉及的许多过程而造成的不确定性。此外，它需要气候学家和水文学家之间的合作，并有望更好地满足洪水风险管理的需求。