Extreme heat: the challenge of modelling a systemic but unseen peril
Extreme heat rarely makes headlines, lacking the cinematic imagery that defines catastrophe. There are no satellite spirals, fire walls, or storm surge maps to broadcast across screens. Yet specialists speaking at the Business Development Agency Risk Summit, held in Bermuda this week, increasingly view it as systemic.
The panel comprised Jeff Manson SVP, underwriting & head of global public sector partnership at RenaissanceRe; Stephen Moss, head of investor analytics at Aeolus Capital Management; Dr Peter Sousounis, founder and principal consultant, Cat and Climate Consulting; and David Stamatis, senior vice president, business development at Descartes Underwriting. They all agreed that heat can be identified as “the silent killer”.
The spectacle belongs to hurricanes and wildfires. Heat, by contrast, is pervasive, incremental and increasingly foundational to how climate risk behaves.
For re/insurers, that distinction matters. Heat is not simply another hazard to price. It is a structural driver of correlation across portfolios.
The science itself is unambiguous. Global temperatures have been rising steadily for decades, and the trend is likely to continue. “Temperatures have been increasing steadily,” Sousounis explained, adding that the real risk lies not in the change in averages but in the behaviour of extremes. “It's not so much that the mean temperature is going to change a little bit. It's that the probability of exceeding a critical threshold has increased dramatically.”
For the insurance industry, that shift from averages to tail events changes the risk architecture. Small temperature shifts expand the probability mass in the extreme tail: the point where infrastructure fails, productivity collapses, and casualty risk accelerates.
More importantly, heat rarely acts alone. It amplifies other perils, often invisibly.
“Heat can occur almost anywhere,” Sousounis noted, having the potential to heavily influence the rest of the catastrophe landscape. Drought, wildfire and extreme rainfall all sit on the same thermodynamic foundations. Warmer air holds more moisture, raising precipitation extremes. Dry, hot conditions accelerate wildfire ignition and spread.
Stamatis captured the implication directly: heat is becoming “the mother of all correlators.”
That dynamic has material consequences for underwriting and modelling. Traditional catastrophe frameworks were built around separately modelled hurricanes, earthquakes, and wildfires. But as climate dynamics evolve, the industry is confronting a world where events compound.
“There’s a big concern about the increasing frequency of compound weather events,” Sousounis said, explaining that situations where hazards that once occurred independently now interact across time or geography. Wildfire stripping vegetation can set the stage for flood losses in the next rainfall event. Drought intensifies agricultural volatility and supply chain stress simultaneously.
Next-generation catastrophe models, the panel argued, must therefore evolve beyond single-peril architectures.
But the challenge is not primarily hazard modelling. Temperature itself is easy to measure. Loss is not.
Heat-driven loss spreads across casualty, infrastructure stress, productivity decline, supply chain disruption and energy demand. In many cases it does not fit neatly into traditional indemnity structures designed for “sudden, accidental events.” As Stamatis noted, “heat isn't really sudden or accidental.”
The result is a widening coverage gap. As climate dynamics reshape catastrophe behaviour, Bermuda’s capital-efficient structures, parametric innovation and ILS ecosystem position it to mediate risks that increasingly fall between traditional insurance categories.
The challenge is not recognising the threat. The industry already does. The challenge is quantifying a peril that quietly connects everything else.
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