Researchers make stunning discovery about recent US hurricanes: 'Impact attribution'

As disasters driven by extreme weather become more frequent and destructive, researchers are developing methods to measure the damage and economic costs linked to rising global temperatures caused by human activity. 

A team at Imperial College London is helping to lead the way in the developing field of "impact attribution."

What is "impact attribution"?

Researchers at Imperial's Grantham Institute of Climate Change and the Environment calculated the cost of climate inaction on hurricane severity. According to the institute, the team used Hurricanes Helene and Milton as case studies.

The findings suggest that in Florida "44 percent of the direct economic damages caused by Helene and 45 percent of those caused by Milton can be attributed to human-induced climate change." The model also indicated that rising global temperatures boosted Helene's wind speeds by about 11% and Milton's by nearly 10.

One of the biggest obstacles to accurately calculating the human activity potentially driving hurricane severity is the scarcity of data, as only a handful of major storms occur each year. As a solution, Imperial's Ralf Toumi and Nathan Sparks came up with the Imperial College Storm model (IRIS) to simulate hurricanes and thereby broaden the dataset. 

IRIS utilizes existing information, including wind speeds and related climate data going back to 1980, to inform its simulations. The model can then demonstrate how rising global temperatures can intensify a hurricane by comparing it to a duplicated model that excludes that factor, evaluating "how much more intense a cyclone's wind speed is today compared with a 1.3°C cooler world without climate change," according to the institute. 

Why is quantifying the impact of natural disasters important?

The Grantham Institute is already using this research to help some governments better anticipate future storm surges and their aftermath. 

By putting a monetary value on the destruction, some scientists also hope to inform programs like the United Nations' Loss and Damage Fund and improve financial support for countries disproportionately impacted by disasters. 

Researchers like Clair Barnes, a research associate with the World Weather Attribution initiative, however, do warn of the pitfalls that could come from over-focusing on this approach. In some nations, and especially in low- and middle-income countries, data is not always available — and that doesn't mean impacts didn't happen and don't need to be addressed and funded.

"There is a bit of a risk of focusing on the things that you can quantify and forgetting all those other things that you can't quantify," Barnes said.

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It means that researchers will need to pair rich contextual information with accurate calculations to tell the whole story. Meanwhile, IRIS may already be improving data transparency, with Toumi describing the model as "an open version" of those used by private insurance companies.

How can this research be used?

As the planet continues to overheat, a new type of legal case known as climate change litigation is increasingly requiring this type of research to establish compelling arguments. 

A group of Swiss women used an impact attribution study to argue that their age and gender made them more vulnerable to the effects of heat waves. In 2024, they won the landmark case in the European Court of Human Rights.

For researchers at Imperial, the goal of their impact attribution methods is to hold the world's biggest polluters accountable for the consequences of their inaction.

As Emily Theokritoff, a research associate at the Grantham Institute, explained, "The main motivation is to raise awareness of the cost of climate change and to illustrate how much worse the impacts are."

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