Unified Modeling and Prediction of Weather and Climate: A 25-Year Journey

In recent years there has been a growing appreciation of the potential advantages of using a seamless approach to weather and climate prediction. However, what exactly should this mean in practice? To help address this question, we document some of the experiences already gathered over 25 years of developing and using the Met Office Unified Model (MetUM) for both weather and climate prediction. Overall, taking a unified approach has given enormous benefits, both scientific and in terms of efficiency, but we also detail some of the challenges it has presented and the approaches taken to overcome them.