Experiment design of the International CLIVAR C20C+ Detection and Attribution project (original) (raw)

2019, Weather and Climate Extremes

There is a growing research interest in understanding extreme weather in the context of anthropogenic climate change, posing a requirement for new tailored climate data products. Here we introduce the Climate of the 20th Century Plus Detection and Attribution project (C20C + D&A), an international collaboration generating a product specifically intended for diagnosing causes of changes in extreme weather and for understanding uncertainties in that diagnosis. The project runs multiple dynamical models of the atmosphere-land system under observed historical conditions as well as under naturalised versions of those observed conditions, with the latter representing how the climate system might have evolved in the absence of anthropogenic interference. Each model generates large ensembles of simulations with different initial conditions for each historical scenario, providing a large sample size for understanding interannual variability, long-term trends, and the anthropogenic role in rare types of weather. This paper describes the C20C + D&A project design, implementation, strengths, and limitations, and also discusses various activities such as this special issue of Weather and Climate Extremes dedicated to "First results of the C20C + Detection and Attribution project". 1. Motivation Over the past decade and a half, many climate researchers have perceived a demand for better understanding of the current extreme weather hazard, as well as of the contribution of long-term climate trends to that hazard (Stott et al., 2013; National Academies of Sciences, Engineering, and Medicine, 2016; Stott et al., 2016). For lack of a better term, we will refer to both questions as dealing with "event attribution". The need for event attribution was first articulated within the context of informing court decisions on tort claims (Allen, 2003; Allen and Lord, 2004; Allen et al., 2007). More recently, event attribution has also been suggested as information required for funding decisions involved in the United Nations Framework Convention on Climate Change "Loss and Damage" (L&D) activity (and other L&D activities) (Pall et al., 2011; James et al.