With weakening prospects of prompt mitigation, it is increasingly likely that the world will experience a four degrees Celsius, or more, global temperature rise. Typically, long-term adaptation planning for extreme climate change faces a variety of psychological, social and institutional barriers which often immobilise decision-makers.This paper argues that long-term planning for such an extreme rise should be a continuous and transformational process, rather than simply building on previous two degrees Celsius adaptation measures. The authors show that it is possible to reduce the complexity and uncertainty surrounding long-term adaptation strategies by breaking the decision-making process down into actionable steps, based on well established methodologies.A case study of the Thames Estuary is used to illustrate how adaptation decisions with long lifetimes can be assessed and framed in a way that can be absorbed in strategic planning. Such decisions include:

safeguarding land allocations for future options
considering whole-life costs for structures (to justify higher initial costs) that may provide benefits in terms of future flexibility.

The paper argues that the ability to ‘nest’ such short term decisions within a longer term framework, which appropriately considers a range of possibly diverging climate futures, is likely to be critical in planning adaptation for a four degrees Celsius world. The paper concludes that the proposed approach requires translating and framing for any given institutional context. Further development and uptake of these ideas would benefit from a set of practical examples that can be observed and a process supported by governments at all levels. The paper states that the emergence of case studies and their systematisation into frameworks to guide decision-makers in practice is an urgent task.