During London Climate Action Week, the Government Actuary's Department and the Institute and Faculty of Actuaries convened a roundtable on climate scenarios, bringing together representatives from eight government organisations. The stated aim was practical rather than promotional: to compare how departments are already using scenario methods, identify common obstacles and consider where a more consistent approach could improve policymaking. The significance lies in the administrative setting. This was not a standalone climate event but a cross-government discussion about how uncertainty is handled inside Whitehall, particularly where long-term risks can alter spending decisions, estate management and service resilience.
According to the Government Actuary's Department, departments increasingly recognise that climate risks reach well beyond environmental policy. The issues discussed covered economic performance, infrastructure, public services and national security, reflecting a broader shift in which climate exposure is being treated as a whole-of-government planning matter rather than a specialist concern. The roundtable also drew a clear distinction between forecasts and scenarios. Forecasts tend to centre on a most likely path, whereas scenario analysis is used to test decisions against severe but plausible futures. In policy terms, that matters because departments are often making choices on assets and services that will still be operating decades from now.
Many departments already use scenario-based tools for horizon scanning and strategic risk planning. The discussion, however, focused on whether those tools are being applied consistently enough when officials move from identifying risks to making policy and investment decisions. A recurring question was not whether climate uncertainty exists, but how far it is built into the formal machinery of appraisal. That point is especially relevant for programmes with long asset lives, delayed benefits or significant adaptation costs. Where appraisal relies too heavily on a single central case, there is a risk that heat, flooding or wider economic disruption are treated as secondary issues rather than decision-shaping factors.
The Institute and Faculty of Actuaries used the session to share its contribution to HM Treasury's Green Book Discount Rate review. As set out by the institute, the review raises a technical but important question for government: whether long-term, transformational and highly uncertain choices should be assessed differently from routine investments. In practice, that goes to the rules departments use to compare present costs with future benefits. For climate-related decisions, small changes in appraisal assumptions can materially affect whether a scheme appears worthwhile, whether resilience spending is justified early and how departments weigh long-term risks that are difficult to price with precision.
Participants then turned to experience from across departments, examining where climate uncertainty is already being considered well and where it can still be missed. The Government Actuary's Department said the discussion covered barriers to wider use and what would help ensure climate scenarios are used effectively, with participants highlighting the need for stronger governance, better analytical tools and closer collaboration between organisations. The picture that emerges is one of uneven maturity rather than institutional indifference. Some parts of government are already using scenario methods for strategic planning, but the roundtable suggested there is still work to do if those approaches are to become standard practice across appraisal, operational planning and capital decisions.
To ground the discussion, the Government Actuary's Department presented a case study from separate work with the Ministry of Justice on overheating risk across the prison estate. That exercise looked at the potential effect of rising temperatures on prison buildings and operations, and showed how scenario analysis can be used to test interventions before conditions worsen. The case study matters because it moves the debate from abstract climate modelling to estate management decisions with direct operational consequences. For departments responsible for buildings, transport networks or frontline services, the value of scenarios is not simply descriptive. It lies in assessing which assets are most exposed, when adaptation becomes necessary and which responses remain workable under a range of future conditions.
The circumstances of the event reinforced the point being made. Deputy Government Actuary Matt Gurden noted that the roundtable was moved to a hybrid format following a Met Office red heat alert during a period of extreme heat, offering an immediate example of climate risk affecting how public business is conducted. No new formal guidance was announced, and the session was presented as a forum for shared learning rather than a policy launch. Even so, the direction of travel is clear. Departments are under growing pressure to show that climate uncertainty is being handled systematically, not episodically, and that policy, investment and risk planning processes are robust against more than one future.