Published in

IOP Publishing, Environmental Research Letters, 1(12), p. 014019, 2017

DOI: 10.1088/1748-9326/aa5386

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A comparison of model ensembles for attributing 2012 West African rainfall

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

In 2012, heavy rainfall resulted in flooding and devastating impacts across West Africa. With many people highly vulnerable to such events in this region, this study investigates whether anthropogenic climate change has influenced such heavy precipitation events. We use a probabilistic event attribution approach to assess the contribution of anthropogenic greenhouse gas emissions, by comparing the probability of such an event occurring in climate model simulations with all known climate forcings to those where natural forcings only are simulated. An ensemble of simulations from 10 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) is compared to two much larger ensembles of atmosphere-only simulations, from the Met Office model HadGEM3-A and from climateprediction.net (a regional version of HadAM3P). These are used to assess whether the choice of model ensemble influences the attribution statement that can be made. Results show that anthropogenic greenhouse gas emissions have decreased the probability of high precipitation across most of the model ensembles, although the magnitude and confidence intervals of the decrease depend on the ensemble used, with more certainty in the atmosphere-only model ensembles. An increase in probability of high precipitation in HadGEM3-A using the observed trend in SSTs for natural simulations highlights the need to ensure that estimates of natural SSTs are consistent with observed trends in order for results to be robust. Further work is needed to establish how anthropogenic forcings are affecting the rainfall processes in these simulations in order to better understand the differences in the overall effect.