Traditional climate impact models often underestimate the severity of future extremes due to a reliance on short historical records and inherent model uncertainties. To address this, we operationalize a "downward counterfactual search" to expose latent urban vulnerabilities, extending analysis from the physical "hazard space" into the socio-economic "consequence space". Using Singapore as a demonstrative case, we perturb a historical 1978 flood event to generate three scenarios: a historical baseline, an operational extreme (1-in-100-year design limit), and a future extreme derived from Singapore’s Third National Climate Change Study (V3). We simulate how these events cascade through interdependent infrastructure, specifically modelling road inundation, Emergency Medical Service (EMS) accessibility, and productivity losses.

Results indicate that while current infrastructure is resilient to historical and operational extremes, the V3 future scenario triggers systemic failure. Inundation increases nine-fold over historical benchmarks, causing widespread gridlock that pushes nearly the entire city beyond critical 11-minute EMS response thresholds. Furthermore, by incorporating coinciding institutional failures—such as historical Mass Rapid Transit (MRT) tunnel flooding—we estimate productivity losses could exceed 915,000 hours. This study demonstrates that traditional models often fail to capture non-linear thresholds where urban systems collapse. By simulating "close calls" and cascading consequences, this framework provides a rigorous stress test for resilience planning against unprecedented climate futures.

Authors:
Terry van Gevelt, Singapore Management University, Singapore

About the Presenter(s)
Terry van Gevelt is Associate Professor of Urban Sustainability and Lee Kong Chian Fellow at the College of Integrative Studies, Singapore Management University.

See this presentation on the full schedule – Monday Schedule

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