Climate change is extending natural disaster seasons from wildfires to tornadoes to hurricanes

Climate change is rewriting the rules for wildfires and other natural hazards.

Just after 11 a.m. on Dec. 30, sheriff’s deputies and fire crews headed out to investigate reports of a blaze near Boulder, Colorado. Six hours later, after 100-mile-per-hour winds hurtling down off the Rockies fanned the flames across dry grasses and suburban enclaves, more than 1,000 homes in the towns of Louisville and Superior were reduced to ash.

It was among the most destructive fires in the state’s history, and it occurred about as far outside what is generally considered “wildfire season” as possible.

In much of the American West, fire is considered a summer problem, when hot temperatures and dry forests combine to offer up perfect conditions for wildfires to spread. As the climate has changed, those warm and dry months have expanded into the “shoulder seasons” of spring and fall. The chances of anomalous major fires springing up in December and January have also increased.

And it isn’t just fires: The changing climate is rewriting the entire concept of disaster seasons, from wildfire to tornadoes to hurricanes, and forcing the nation to reassess its relationship with risk.

Policymakers and the public are understandably struggling to keep up. Resources from money to personnel that tend to be allocated on a seasonal basis may need to be made available year-round. People in vulnerable locations need to stay vigilant and plan for the worst on an expanded scale.

Beyond fires

But climate change isn’t just raising the risk of wildfires. Only a few weeks before the Boulder disaster, an outbreak of severe storms in the Midwest spawned several long-track tornadoes. One of them tore through more than 160 miles mostly in Kentucky, causing widespread damage; all told, the storms killed at least 76 people. And just like the Boulder blaze, the tornadoes appeared well outside their traditional season, generally considered to peak from April through June.

It’s important to note that the climate change-tornado connection isn’t remotely as solid as that for fires or heat waves or some other disasters. But that doesn’t mean the connection isn’t there.

And then there’s hurricanes. The only natural disaster that has an official, government-defined season is straining at those bounds thanks to climate change. Atlantic hurricane season stretches from June 1 to Nov. 30, and while there have been outlier storms in the past, they seem to be increasing in frequency. According to data from the National Oceanic and Atmospheric Administration, no decade has had as many storms form in May than the 2010s, with six. There have already been three in the first two years of the 2020s.

The basic mechanism is fairly simple: The ocean’s surface has warmed substantially over the past century — and especially over the past few decades. That means the conditions required for tropical cyclones to form exist for more of the year. Because hurricane season does have official start and end dates, this is the first of these shifting periods that may provoke an obvious policy response: a change to those dates.

A shift like that is not just about the science and frequency of storms. The consideration, according to the NOAA spokesperson, will include “a detailed social science study” of the potential impacts of redefining hurricane season. Klotzbach pointed out that just adding some more days of potential catastrophe to our mental calendars may not be such a good thing.

“People are getting messaged with everything all the time,” he said. “Watch out for this, look out for that.”

Do disaster “seasons” make sense?

With hurricanes, or with fires and tornadoes, does it actually help to extend the period of potential danger in terms of public health and awareness? Hurricane season is already six months long, and the bulk of truly damaging storms tends to cluster in August and September. How vigilant do people in vulnerable areas really need to be for much of the year?

There are other implications for the shifting disaster seasons. Klotzbach noted that some insurance policies related to hurricanes are put together in May based on forecasts of the upcoming season, meaning the industry might have to change its practices — if only by a few weeks. For other types of disasters, like fires or tornadoes, it may mean rethinking how we do things year-round.

“We really can’t stop a tornado,” Strader said. “There’s nothing really to do if you’re in the path of it except for have better homes, better building codes, better enforcement of those building codes. That’s important.”

“We need to think of our wildland firefighting people resources differently,” Raymond said. “These need to be full-time jobs.”

The fact is, though, that in some cases there may not be many actions that could limit the damage from “out-of-season” disasters. The fire in Boulder last December mixed the foibles of day-to-day human behavior with a perfect climate change-enabled circumstance to produce a destructive blaze. We can try to limit the foibles, but those circumstances are only getting more likely. “We expect warming,” Raymond said, “and warming in all seasons.”

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