Climate Impacts Add $533 a Year to Canadian Home Insurance Premiums Since 2008, U of T Study Finds

What the Ratio Actually Measures

The Sun paper finds that for every $1 insurers expect to pay out in additional weather-related home insurance claims, they charge homeowners roughly $1.78 in higher premiums to cover those expected climate-driven losses. That 78-cent markup is not opacity or profit — it reflects reinsurance costs, capital costs, operating expenses, and the prudential margins regulators expect insurers to hold against catastrophe-prone lines of business.

The ratio is doing more analytical work than the press coverage has credited. It is the conversion factor that turns a projected loss trend into a premium outcome. Without it, the report could tell you climate-driven losses are growing at 11.9% per year, but it couldn't tell you what that growth rate means for the bill you actually pay. With it, the paper can run the full chain: loss experience → projected losses → required premium revenue → per-household premium impact.

That's why it deserves headline placement and hasn't received it. The $533 figure is the output of the model. The 1.78 is the engine driving the model. For a homeowner trying to decode a renewal increase, the multiplier tells you something concrete and forward-looking: each incremental dollar of climate-driven loss insurers project for your risk profile pulls almost two dollars of premium with it.

Why It's the Number That Predicts the Next Five Years

The historical 11.9% annual growth in weather-related claims is the past. The forward projection from insurers themselves — roughly 11.5% per year continued growth — is the near future. The 1.78 multiplier is the link between them and your bill. If the industry's own forward projections are accurate, the multiplier tells you that climate-driven premium pressure compounds at nearly twice the rate of the underlying loss growth.

That's the math worth carrying into a renewal conversation. Not the $533 average, which by construction is an output of a 16-year backward-looking model. The 1.78, which converts whatever climate-driven loss expectation an insurer has for your specific risk profile into a premium effect.

The Counterfactual Built from Routine Claims

The Sun paper's central analytical move is a counterfactual. It assumes that catastrophic weather-related claims (floods, wildfires, severe storms, major perils) and non-catastrophic routine claims (burst pipes, theft, minor accidents) are subject to the same underlying inflation, construction-cost, and economic drivers. Only catastrophic losses, the paper argues, are significantly intensified by worsening climate hazards.

If that assumption holds, routine claims become a usable baseline — they're the trend line home insurance loss costs would have followed without escalating extreme weather. The gap between catastrophic and routine trends (11.9% vs 1.97% annual growth) is then interpreted as the climate-driven component. About two-thirds of that gap is attributed to climate directly; the remaining third is allocated to drivers like urban growth and aging infrastructure.

This is the load-bearing assumption. Move it and the 54.5% climate share moves with it. The strength of the methodology is that the assumption is transparent, testable, and reasonable on its face. The weakness is that it's not bulletproof — and readers should understand exactly where it could give.

Where the Counterfactual Strains

The assumption that routine claims have no climate exposure is mostly defensible but has real edges:

• Freeze-thaw cycles. Burst-pipe claims, classed as routine, are partly driven by freeze-thaw frequency — which is itself shifting under a changing climate. A material climate effect on routine claims would mechanically inflate the baseline and shrink the inferred climate share. The paper doesn't engage with this specifically.
• Roof failure thresholds. Wind, hail, and ice events that would once have been near-misses are increasingly producing claims that look "routine" at the policy level (a single tile, a small leak) but reflect climate-driven changes in event frequency. Where insurers code these matters for the partition.
• The two-thirds attribution split. Of the gap between catastrophic and routine claim growth, two-thirds is attributed to climate and one-third to non-climate drivers. The split is reasoned but not derived from a separate empirical model — it's a defensible allocation, not a measurement.
• The model assumes a clean partition. Real insurance loss data is messier than the catastrophic-vs-routine binary the model relies on. Aggregating claims into those two buckets requires coding judgments that affect the underlying growth rates.

None of these strains invalidate the central finding. They do mean the 54.5% climate share is best read as a calibrated central estimate from a defensible method, not a precise measurement. A different reasonable researcher applying a different reasonable partition would land at a different number — probably in the same neighbourhood, but not identical.