<em>The Weekly Planet</em>: Hail! It’s America’s Most Underrated Climate Risk

And that ends the section of the newsletter where I talk about insurance. By positioning itself in this way, Understory happens to have collected a new kind of hail data. It has a ground-truth record of where hail has landed, a surprisingly hard type of data to come across in the U.S.

“The observational data for hail is … dangerous. It’s less quality-controlled,” John T. Allen, a meteorology professor at Central Michigan University who wasn’t involved in this study, told me. “If you hit a city, you get lots of reports, but if you don’t hit a city, you don’t get many reports at all.”

Understory’s data are the key to the new study. Kubicek and his co-authors used machine learning to associate the spots where they know hail has actually fallen with the radar data observed at the time. Then they found similar radar data going back to 1979, extrapolating from their ground-truth data to create a historical record of hail fall.

More frequent hail is a nuisance by itself, but the damage depends on where it falls. In Hail Alley, roofers and car garages are used to dealing with hail. “If you have a hailstorm hit Dallas, there’s a whole market around that,” Kubicek said. “If you have a hailstorm hit Columbus, Ohio, or Nashville, Tennessee, then it will be costly in ways it wouldn’t be elsewhere.”

“The most shocking thing for us is that [hail’s] moving to new territory at essentially a rate of growth of 1.1 percent year over year,” he said. “It works out to a new Delaware getting hail every year.”

First Occurrence of Hail, 1979 to 2018

Now for the caveat: The paper hasn’t been peer-reviewed. I was able to circulate it to a few hail scientists, and would describe them as impressed with Understory’s data but skeptical of its methodology. “I think they’re on the right track when it comes to ground-truthing, but there’s a lot more that could be done,” Allen said. Often, the paper skips over statistical work or data cleaning that a more polished academic study might require, he added.

Yet these scientists did not dispute its broadest findings: Climate change seems to be making hail worse.

“A consensus does seem to be emerging” that hailstorms will become more severe “as the planet warms,” Julian Brimelow, a hail researcher in the Canadian government, wrote in an email. “We are on a path for some devastating and incredibly expensive hail damage years in the future. This is why insurance and re-insurance companies are so concerned.”

And that’s what I find truly noteworthy about the Understory study. It shows that some climate science is now happening entirely in the private sector: Climate-change data are detected, standardized, and converted into insurance payouts before they ever reach the hands of an academic.

In this newsletter, we talk a lot about how climate change is a function of the economy, how it emerges from the physical infrastructure of the fossil-fuel-based energy system. What Understory shows is that this is now true in a much more mundane way too. Climate science is now part of the ordinary course of business for insurance companies.