High impact scenarios and storylines

This project will create a set of ‘high impact’ scenarios or storylines, representing plausible high-consequence but low-likelihood future climates. The scenarios will define hot, cold, wet and dry extremes, windstorms, sea level rise and compound events.


The 2018 UK Climate Projections (UKCP18) provide information about the future climate of the UK, under a range of different scenarios for future emissions. Users involved in adaptation and resilience policy are also interested in how very extreme events might change, or what might happen if there were to be a fundamental shift in climate regimes or sea level due to some tipping point being crossed. Since March 2020 we have become increasingly familiar with ‘reasonable worst case scenarios’: this project will construct a set of ‘high impact’ scenarios for risk assessment, emergency planning and adaptation and resilience planners.

The project will use a variety of approaches to produce high-impact scenarios or storylines. These approaches will include analysis of past experience (including through weather data recovery initiatives), use of reanalysis products, use of current generation climate models, and use of theory and expert judgment. The project will also take advantage of simulation experiments (e.g. pseudo-global warming simulations) run elsewhere. ‘Storylines’ are basically scenarios informed by a specified underlying narrative describing, for example, some plausible change in driver of climate change. These scenarios and storylines will include extreme events and sequences of events (for example over one or more seasons), and longer-term sequences assuming, for example, high values for climate sensitivity or specific changes in the drivers of UK weather.

It is intended that the set of high impact scenarios and storylines we produce can be used with existing analytical techniques to estimate impacts.


The overall aim of the project is to deliver high-impact scenarios and storylines relevant to users, in forms that users can readily apply.

The project is based on the use of expert judgement and interpretation of various lines of evidence, informed by stakeholder and advisory groups. It will look at all the identified potential high-impact scenarios and storylines in a consistent way, providing information on confidence and credibility.