Why WTW’s Climate Diagnostic gives insurers a sharper view of risk

WTW’s Climate Diagnostic tool promises insurers a clearer view of how floods, storms and heat waves hit their books. What does the platform really do, where does it help in daily underwriting, and where are the limits?

Reviewed: ad hoc news Software & Services desk. Edited and checked on 2026-06-18, 08:59. Details in the imprint.

WTW’s Climate Diagnostic is one of those tools that only shows its power when a map lights up with red flood zones and deep-blue wind corridors across an insurer’s portfolio. Suddenly, exposure is not an abstract spreadsheet, but a landscape of risk.

What Climate Diagnostic actually does

Climate Diagnostic takes insurers’ own portfolios and overlays them with physical climate risk data such as flood, wind and heat stress for different future scenarios. The tool is aimed at underwriting, portfolio steering and regulatory climate disclosures.

According to WTW, users can drill down from a high-level view of a book to individual locations, combining catastrophe models with climate projections to see how losses might behave over time. The official Climate Diagnostic product page describes it as a way to compare risks under multiple warming pathways and time horizons.

How it changes daily underwriting

In practice, Climate Diagnostic promises something very concrete: a property treaty underwriter can see how a flood-prone region in a 1.5 °C scenario differs from a 3 °C world, and how that feeds into aggregate exposure. That is more tangible than a generic climate report.

WTW emphasizes that the platform connects climate science, catastrophe models and insurers’ own exposure data, so that pricing and capacity decisions can factor in long-term shifts instead of only historical losses. This supports both risk appetite setting and discussion with reinsurers on climate assumptions.

Regulation pushes the demand

Climate Diagnostic is also designed with disclosure frameworks in mind. WTW explicitly references use cases such as TCFD-aligned reporting and regulatory stress testing for supervisors in Europe and other regions. That makes the tool less “nice to have” and more compliance infrastructure.

Regulators in markets like the UK are asking large insurers to quantify climate scenarios for different business lines, and manual spreadsheets quickly hit their limits. A specialized analytics layer can help standardize assumptions, document methodologies and respond more quickly to new supervisory requests.

Strengths, but not a crystal ball

The strength of Climate Diagnostic lies in turning abstract climate pathways into spatially resolved risk views that can be sliced by peril, region or line of business. Maps, charts and scenario sliders give underwriters something they can grasp at a glance.

However, the tool does not remove the uncertainty that comes with climate modelling. Even the best projections differ, and insurers still need internal governance to choose scenarios, set tolerance levels and decide how much conservatism to build into pricing and limits. Climate Diagnostic is an instrument, not the decision-maker.

Where WTW positions the platform

For WTW, Climate Diagnostic slots into a broader climate and resilience suite that also includes advisory services and other analytics. The group presents it as a way to bridge the gap between climate science, financial risk and board-level strategy.

In marketing material, WTW points to collaborations with academic and modelling partners, underlining that the datasets behind the tool are regularly updated. That matters in a field where new research on, for example, convective storms or wildfire behaviour can materially affect loss expectations.

Context and stock reference

WTW, listed on NASDAQ under ISIN US9663871021, has been pushing hard into data-driven risk tools alongside its traditional broking and consulting services, and Climate Diagnostic is one of the more visible pieces of this strategy.

Key facts on WTW’s Climate Diagnostic

• Product: Climate Diagnostic
• Manufacturer: Willis Towers Watson Public Limited Company
• Category: Software / climate risk analytics
• Launch: Around early 2020s, continuously updated
• RRP / Price: Not publicly listed, enterprise licensing on request
• Availability: Offered globally to insurers and financial institutions
• Target group: Insurers, reinsurers, banks and institutional investors with material physical climate risk exposure
• Highlight / USP: Integrates climate scenarios with catastrophe models and client exposure data for granular portfolio and disclosure analysis

This article was AI-assisted and editorially reviewed. Product information without guarantee; prices and availability may change at short notice. No investment advice, no buy or sell recommendation. Stock-market transactions involve risks up to total loss.