A resident looks around a charred apartment complex in the aftermath of a wildfire in Lahaina, western Maui, Hawaii on August 12, 2023. Image Credit: AFP

Washington: As scientists weigh the influence climate change may have had in fuelling Hawaii’s wildfires, there isn’t one standout factor they point to. Rising temperatures likely contributed to the severity of the blaze in several ways. But global warming could not have driven the fires by itself.

Maui is facing a compound disaster, where many different agents acted together to make the fires so horrific. As human influences on the climate and environment grow, the risk of these disasters is escalating.

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Recent floods in China, fires in Greece and deadly heat in the Southwest US are other recent examples of how extreme weather, human-caused climate change and changes to the local environment can converge in devastating fashion.

“If you add together a whole bunch of influences, that’s how you get a disaster,” said Jeff Masters, a meteorologist for Yale Climate Connections. “No one thing makes it happen.”

The links between human-caused climate change and fires are well-established. Global warming means plants can more easily dry out, because warmer air hastens the evaporation of water. As the air sucks more moisture from the land, fire risks are increasing.

Disaster in Lahaina. Image Credit: AFP

Hawaii is, on average, two degrees warmer than it was in 1950, according to state climate data. Scientists said that likely provides the strongest connection between humans’ fossil fuel consumption, which emits greenhouse gases that warm the planet, and the likelihood of fires in Hawaii and elsewhere.

Rising temperatures have also intensified the heat that has baked the Southwest this summer - and which sent hot, dry air toward Hawaii. And climate change is helping to strengthen hurricanes like the one that passed south of the islands this week, probably increasing the strength of winds that fanned the flames.

What are non-climate influences?

But scientists have also prominently mentioned the role of non-climate influences in the intensity of the firestorm, such as the introduction of highly combustible nonnative plants, as well as weather patterns that happen naturally.

Among factors that made the fire so destructive - severe winds and ongoing drought - the influence of climate change appears indirect, at best.

As wind sent fires spreading out of control Tuesday, many meteorologists pointed out that Hawaii found itself between a strong area of high pressure over the North Pacific and Hurricane Dora, a cyclone that rapidly intensified into a major Category 4 storm. That pressure difference meant Hawaii was in the middle of winds flowing intensely from high pressure to low, gusting over the islands like air being released from a balloon at more than 80 mph in some spots.

Destroyed homes in Lahaina. Image Credit: AFP

Research has shown more tropical cyclones have rapidly intensified in recent decades, and that those rates of intensification have accelerated. Warmer temperatures provide more energy for storms.

But some immediate analyses of the winds observed in Hawaii have found Dora’s presence may have only increased the gusts’ speed by about 5 mph, Masters said. The high pressure - aided by a flow of hot, dry air from the Southwestern US into the Pacific - could have been enough to stir damaging winds on its own.

How hurricane intensity played a role

The hurricane and its intensity were “certainly not the main effect” fuelling the fires, Masters said, though its presence could have contributed to the disaster.

As for the drought conditions that covered more than a third of Maui County, where the most destructive fires burned, there is no direct sign that they are the product of climate change, said Abby Frazier, an affiliate faculty member at the University of Hawaii now based at Clark University in Massachusetts.

A woman with her cat after finding him in Lahaina in western Maui. Image Credit: AFP

While there is a long-term trend of declining precipitation in Hawaii, there isn’t enough evidence to suggest that is the product of anything besides normal climate patterns and fluctuations in the Pacific, she said. Precipitation patterns there are heavily influenced by El Nio, which returned in June, and by a longer-term pattern known as the Pacific Decadal Oscillation.

Does El Nino arrival explain?

El Nio is known for bringing drier winters, but its arrival doesn’t explain the current conditions, Frazier said. In the summer, it can bring more precipitation than normal because of increased tropical cyclone activity, she said.

“We can’t officially say it’s climate change that’s causing all this drying,” Frazier said. “Natural variability is just so strong in Hawaii.”

At a glance
More than 2,200 structures were damaged or destroyed as the fire tore through Lahaina, according to official estimates, wreaking $5.5 billion in damage and leaving thousands homeless.
Lahaina, a town of more than 12,000 and former home of the Hawaiian royal family, has been reduced to ruins, its lively hotels and restaurants turned to ashes.
A banyan tree at the centre of the community for 150 years has been scarred by the flames but still stands upright, its branches denuded and sooty trunk transformed into an awkward skeleton.
The new toll makes the blaze the deadliest in the United States since 1918, when 453 people died in Minnesota and Wisconsin, according to the non-profit research group the National Fire Protection Association.
The death toll surpassed 2018’s Camp Fire in California, which virtually wiped the small town of Paradise off the map and killed 86 people.
Hawaii emergency management records do not indicate the warning sirens sounded before fire hit the town. Officials sent alerts to mobile phones, televisions and radio stations, but widespread power and cellular outages may have limited their reach.
Fuelled by a dry summer and strong winds from a passing hurricane, the wildfires on Maui raced through parched brush covering the island.
More than 1,400 people had been taken in at emergency shelters.

That is not to say human activity didn’t directly contribute to the fires in ways that don’t involve the climate.

They are increasingly spreading by burning invasive and fire-prone grasses brought to the islands for ornamental use or for cattle grazing. As agricultural activity has declined on the islands, the grasses have spread across fields that were once regularly watered and maintained, said Alison Nugent, an associate atmospheric scientist at the University of Hawaii’s Water Resources Research Center.

Will such catastrophes increase?

“Over the last few decades those managed agriculture lands have progressively become more and more unmanaged,” Nugent said. “There’s grassland right next to very expensive houses.”

The wildfire risks that introduces demonstrates that “it’s more than climate change,” Masters said. “Humans are messing with the system.”

As long as that continues, he said, “We should expect these sorts of catastrophes to increase.”

Clay Trauernicht, a fire researcher at the University of Hawaii, said he and others concerned about wildfire risks have for years been working to raise awareness about the importance of better managing the grasses and taking other efforts to harden homes.

He said he hopes the devastation on Maui is enough to spur action so that the fires’ burden isn’t left solely to firefighters.

“We don’t have to be at the mercy of these weather events, but the way we’re operating right now, we are,” Trauernicht said. While climate change is a global problem, the grasses are a local one. “This is a thing we can manage.”