The Government Actuary’s Department and the Institute and Faculty of Actuaries used London Climate Action Week to shift a technical debate into the everyday business of government. Their cross-government roundtable brought together climate and risk specialists from eight government organisations to ask a practical question: how can climate scenarios be used more consistently when officials make long-term decisions? According to the Government Actuary’s Department, the aim was to share experience, identify common barriers and see where scenario analysis can strengthen policy-making across government. That may sound procedural, but the issue is immediate. Climate risk is already reshaping how public institutions plan, spend and keep services running.

Government departments increasingly recognise that climate pressures reach far beyond the environment brief. They can affect economic performance, infrastructure, public services and national security, which means the quality of climate planning now matters across the state, not only in specialist teams. This is where scenario analysis earns its place. As the Institute and Faculty of Actuaries explained at the roundtable, scenarios are not forecasts. They do not claim to name one likely future. Instead, they test decisions against severe but plausible futures, asking whether a policy, investment or building would still hold up if conditions become much harder.

Many departments already use scenario-based tools for horizon scanning and strategic risk planning. The concern raised at the event was that this practice is still uneven. Climate uncertainty may be built into one programme and overlooked in another, especially when shorter budget cycles and day-to-day pressures pull attention back to the near term. That inconsistency has consequences. If departments use different assumptions, or leave climate risk out until late in the process, resilience can end up looking like an optional extra rather than part of sound public decision-making. The roundtable’s value was in giving organisations space to compare methods and push towards a more common standard.

The clearest example came from separate Government Actuary’s Department work with the Ministry of Justice on overheating risk across the prison estate. Rising temperatures are not just a statistical concern in this setting; they can affect living conditions, staff wellbeing and the reliability of buildings that must keep operating during heat stress. By applying scenario analysis, the work examined how higher temperatures could affect prisons over time, what long-term risks might build up and which interventions are worth testing before conditions worsen. In plain terms, that is the strength of this approach: it turns uncertainty into choices that can be assessed early, rather than waiting for disruption to force action.

The timing of the roundtable made the message harder to dismiss. Deputy Government Actuary Matt Gurden said the event had to move to a hybrid format after a Met Office red heat alert during a period of extreme heat. A discussion about future climate risk was suddenly being shaped by present-day heat, which is exactly the kind of signal scenario work is meant to catch before it becomes routine. That detail gives the meeting a stronger public edge than a standard policy seminar. When extreme heat changes how officials meet, travel and work, the case for climate resilience stops being abstract. It becomes part of how government buildings, staffing plans and public services function now.

The Institute and Faculty of Actuaries also used the session to share its contribution to HM Treasury’s Green Book discount rate review. The paper explores whether long-term, transformational and highly uncertain decisions should be appraised differently from routine investments, a question that sits close to the economics of resilience. That matters because the rules used to assess value can shape whether preventative action happens soon enough. Public assets expected to last for decades cannot be judged only against short-term average conditions. They need to be tested against the climate pressures they are likely to face over their working life.

What emerged from the roundtable was not a call for more modelling for its own sake. According to the Government Actuary’s Department, participants shared an interest in better governance, stronger analytical tools and closer collaboration between organisations so climate scenarios can support real policy and investment decisions. That is the useful takeaway. The hard part of climate resilience is often not spotting the risk, but building it into ordinary decisions early enough to matter. If government can make scenario analysis a normal part of planning, it stands a better chance of protecting public services before the next heat alert forces the issue.