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Was the Mexico hailstorm due to climate change? Scientists say it's not that simple

A summer hailstorm struck Guadalajara on June 30, engulfing parts of the city in ice, according to the BBC. Although short — lasting only about 20 minutes — the Mexico hailstorm unleashed up to five feet of hail, damaging at least 200 homes and business and sweeping away dozens of vehicles. Residents didn’t report any injuries or deaths, but the event has left many scratching their heads, since temperatures in the area had recently been hovering at around 90 degrees.

“This is a very unusual event,” says Jonathan Martin, an atmospheric and oceanic scientist at the University of Wisconsin, Madison. Indeed, Jalisco Gov. Enrique Alfaro Ramírez said in a video posted to Facebook that the storm was “one we haven’t seen before," a statement that leads Martin to theorize that that kind of event happens in Guadalajara at most only once every 60 to 100 years.

Typically, says Martin, the combination of warm surface temperatures and cool temperatures at about three miles above the ground experienced in the area would result in thunderstorm showers, not hailstorms. But on June 30, above-ground temperatures in Guadalajara were much colder than normal, freezing the water droplets into roughly dime-sized hailstones. On top of that, surface temperatures were warmer than usual, and the stark difference in surface and above-ground temperatures produced an intense storm with huge amounts of precipitation.

In an email to Mic, Morgan O’Neill, an earth system scientist at Stanford University, emphasizes the oddity of the weather event, explaining that “very severe hailstorms can still occur in the tropics, but they tend to occur preferentially in high-altitude regions.” She points to a massive 2014 hailstorm that slammed Mexico City, which has an elevation of about 7,400 feet, as an example; Guadalajara, by comparison, has an elevation of only around 5,100 feet.

In discussing the storm, Gov. Ramirez tweeted, “Hail more than a meter high, and then we wonder if climate change exists." Did climate change actually trigger the storm, though? Without more data, it's hard to say for sure, according to Martin.

“There’s an enormous amount of inherent variability in the earth’s climate system” independent of human-driven climate change, he explains. In other words, it’s hard to rule out the possibility that such storms, though extreme, simply occur every few decades in Guadalajara regardless of climate change. O’Neill agrees, saying, "One extreme storm can’t indicate anything useful about climate change, but a trend holds much more information. Are such storms happening more frequently? Are conditions for their occurrence increasingly favorable?"

As it turns out, panning out and analyzing storm trends reveals that the frequency of intense storms has indeed grown over time and could continue to do so, says Martin. According to the National Oceanic and Atmospheric Association, climate change will likely cause an increase in the proportion of Category 4 and 5 tropical cyclones in the coming years. That goes for other extreme weather events, too; a 2018 study forecast an increase in the frequency of deadly heat waves, for instance. Currently, there's an intense heat wave in Europe happening, with the French town of Gallargues-le-Montueux reaching 114.6 degrees Fahrenheit — the highest recorded temperature ever in France — on June 28.

So regardless of whether the Guadalajara storm "is a direct product of climate change," says O’Neill, "we should be very concerned about climate change for myriad other reasons. The overall picture that theory, observations, and modeling paint is very bleak.”