Why one hurricane’s climate cost can’t be pinned to a single figure
Two accepted methods give Hurricane Harvey very different climate-linked shares of its losses, and the study’s authors say no breakthrough will settle it.
By
Leah Morrison
In brief
- Estimating what climate change added to a storm means comparing it with a world without warming.
- Frequency and intensity methods can land far apart on the same hurricane.
- A consistency test shows both can be valid, so the authors call single-event costs ambiguous.
There is no single price tag for the damage that climate change adds to a hurricane or a heat wave, because the answer shifts with the valid method used to calculate it. A study summarized by Phys.org argues that this ambiguity is built into the problem itself rather than caused by weak data.
Comparing a real storm with a world that never warmed
Human activity has raised global temperatures, yet pinning down the costs directly incurred through that warming remains hard. Hurricanes and heat waves are shaped by warming in ways that may differ from place to place and vary over time, and neither observations nor climate models always record those effects accurately.
Researchers therefore rely on a counterfactual. They place an actual extreme weather event next to a hypothetical scenario where climate change played no part, and the gap between the two yields an estimate of the costs tied to warming.
The practice is known as extreme event impact attribution, or EEIA. It turns such side-by-side comparisons into estimates of damage and cost linked to warming, and more than one version of it is in use.
Two approaches, one storm, very different answers
One version, built on frequency, asks how much more probable climate change made an event. The other, built on intensity, asks how much more destructive climate change made it. Run on the same disaster, the two can produce vastly different estimates.
Hurricane Harvey in 2017 shows how far apart they can land.
Were the two estimates supposed to match, a gap this wide would suggest that at least one method is technically flawed or lacks a sound theoretical basis.
A consistency test changes the reading
To probe that possibility, A. L. Match and colleagues propose a consistency framework in an article published in AGU Advances. Under it, a method is consistent when, across a group of events over time, the sum of costs it assigns to climate change equals the real extra costs that were incurred.
According to the researchers, frequency-based and intensity-based methods are both able to meet that standard. The framework also spells out particular conditions under which excess costs are captured in a coherent and accurate way.
What lasting ambiguity means for adaptation and lawsuits
Since both methods can be consistent, and so valid, the authors conclude that the climate-related cost of any one event is inherently ambiguous. In their account, neither a technical breakthrough nor flawless knowledge of climate and society would remove that ambiguity.
They add that this could restrict how far EEIA can guide adaptation, recovery or litigation. Each of those uses depends on putting a figure on what climate change contributed to a particular event.
The paper is A. L. Match and colleagues, “On the Inherent Ambiguity of Extreme Event Costs Attributed to Climate Change,” published in AGU Advances in 2026 under DOI 10.1029/2026av002546.
Photo: Connor Scott McManus / Pexels
