We are releasing the monsters

“It ain't rocket science — when it's hotter and drier, fires burn more easily and more explosively.” — John Vaillant, author of Fire Weather

Billions of tonnes of planet-heating gases emitted by humans from burning oil, methane gas and coal are unleashing monsters around the globe. And even the wealthiest state in the most powerful nation on the planet hasn’t been able to contain them. Global warming is cranking up the heat and drought in California, spawning an accelerating outbreak of monstrous wildfires. 

In this article, I use California’s well-documented climate and fire history to illustrate two critical things about wildfire in our warming climate. The first is how hot-and-dry conditions breed megafires. The second is how wildfire responds non-linearly to warming.   

As Jennifer Balch, lead author on a recent study of western North American wildfires, explained to Bloomberg Green: “What we do know is that it takes just a little bit of warming to lead to a lot more burning.” Or, as another climate scientist, Park Williams, phrased it in The Atlantic, “each degree of warming causes way more fire than the previous degree of warming did. And that’s a really big deal.”

Lots more fire doesn’t just mean an acceleration in the number of fires. It also means the largest megafires are transforming into uncontrollable monsters. 

The newest monster

I’ll start by looking at California’s recent monster fire and the hot-and-dry conditions that set the stage for it. 

The January 2025 firestorm involved more than 30 fires burning across the Los Angeles region. The two biggest and most destructive were the Eaton and Palisades fires. These raced through city neighbourhoods at shocking speed. They destroyed homes, businesses, schools, churches and nearly everything else in their path. Thousands of structures burned. Millions of people fled their homes. Billions of dollars went up in toxic smoke clouds. 

Some estimates peg it as the world’s most expensive wildfire in modern times. And it leaves behind an insurance crisis that threatens to topple the region’s sky-high real estate values.

This unprecedented rampage happened in the heart of California – the world’s fourth-largest economy. California has one of the biggest and best-trained firefighting forces with decades of experience fighting big fires. And the state brings the latest high-tech arsenal to the fight, including drones, infrared spotters, satellites, super-computers, artificial intelligence, robots, suppression foams, huge stockpiles of specialized fire retardant that can be precision dropped from night-flight capable bombers, plus fleets of giant bulldozers and fire trucks. And all that still wasn’t enough.

This highlights the sobering fact that megafires keep winning because, while we fight these monsters with one hand, we give them new superpowers with the other. Wildfires feast on hot landscapes full of tinder-dry fuel. And our fossil fuel emissions are now regularly cooking up hot-and-dry conditions beyond anything previously experienced in a region — by the humans that live there, by the infrastructure we’ve built there, or by the ecosystems that are getting baked and incinerated.  

These were the kind of unprecedented hot-and-dry conditions that primed the landscape to burn before the Los Angeles firestorm. 

Loading the climate dice on California’s south coast

To illustrate how the warming climate in the region of the Los Angeles firestorm has been generating unprecedented hot-and-dry fire conditions, I’ve created a chart below. It shows the average temperature and rainfall on California’s south coast every year since 1900. This is for the six-month period that preceded the Los Angeles firestorm (July – December). 

The data for this chart and the similar ones that follow came from the fabulous Climate at a Glance site run by the National Oceanic and Atmospheric Administration’s (NOAA). 

On this chart, there is one dot for each year. All the years in the twentieth century (1900-1999) are grey. I’ve also added grey shading to show the climate range for that century. And I’ve indicated the century’s average temperature and rainfall using dotted lines.

You can compare that old climate to the red dot labelled 2024. That dot shows the conditions that led up to the Los Angeles firestorm. Temperatures were hotter than anything experienced in the previous century. And rainfall was at record lows, with only half an inch of rain during those six months. As you can see, such extreme hot-and-dry conditions never happened in the last century. 

Unfortunately, while 2024 is a freak outlier compared to the old cooler climate, it isn’t in our new warmer climate. Instead, it’s now just part of the normal mix of years. This can be seen on my next chart. 

On this version of the chart, I’ve added the rest of the years in the current century (2000-2023) as red dots. Now you can see how the climate in this century is hotter. All the years are now hotter than the old average. And two-thirds of them qualify as hot-and-dry compared to the old climate. More frequent hot-and-dry conditions prime the landscape for more frequent fire. 

And most worrisome of all, is the growing number of years that are now unprecedentedly hot and dry for the region. These conditions prime the landscape for unprecedented fires. And that’s exactly what occurred during the two most extreme years so far: 2017 and 2024. They are circled in white on the chart. 

In December 2017, the Thomas Fire burned through Ventura County. It was California’s first top 20 megafire to burn during a winter month. It took an army of firefighters a month to put it out. By the end, it had become the state’s largest wildfire ever recorded up to that point.  

Similar hot-and-dry conditions returned in 2024. These, once again, primed the landscape for unprecedented fire. And once again, an unprecedented megafire erupted: the Los Angeles firestorm. 

It’s important to understand how we have overheated the climate dice. Because it warns us that such extreme fire conditions will keep returning with regularity. Again, and again. 

The conditions will grow more dangerous if we keep burning fossil fuels — the gasoline in our cars, the diesel in our trucks and jetliners, the natural gas in our buildings, the coal in our power plants. The CO2 this burning pumps into the atmosphere will load the climate dice even hotter. And we will suffer under even more extreme fire conditions on a regular basis. 

This same pattern is unfolding — even more dramatically — statewide during the fire season. Let’s look at that next.

Loading the climate dice during California’s fire season.

Here’s the same type of chart, but this one covers the entire state during its traditional fire season (May – October). You can see how the climate has shifted hotter and drier during California’s critical fire season as well.

Once again, we see that every year since 2000 (all those red dots) has been hotter than the old normal. And here too, the fire-suppressing cool-and-wet conditions that were common in the previous century never happen anymore. We’ve turned these climate dice perma-hot. That means a lot more years primed for megafires — and, as we will see, the number of megafires has exploded.

Far more dangerous is that deep-red quadrant in the upper left of the chart. That’s where the relatively hot-and-dry fire seasons now fall under our new warmer climate. If you look closely, you can see that this entire quadrant is beyond anything that happened in the last century. That means we’ve loaded the climate dice to roll out a lot of fire seasons that are unprecedentedly hot and dry compared to the last century. Those conditions prime the landscape for unprecedented fire monsters that are beyond anything seen in the last century. And, as we will see, that has also happened in shocking numbers.

Take a look…

The megafires in the twentieth century  

To show how megafires have responded, I will build a chart showing California’s 40 largest wildfires on record. Each of these megafires burned more than 110,000 acres. This historical fire data comes from California’s Department of Forestry and Fire Protection (CAL FIRE) and stretches back to 1920 when accurate record-keeping began.

I’ve placed these 40 largest wildfires in three groups. The first group burned during the twentieth century. There were seven.

There is a grey bar on this chart for each megafire, positioned in the year the fire burned. The height of the bar indicates the number of acres burned. For example, the grey bar on the far left shows the Matilija Fire of 1932 that burned nearly 220,000 acres.

I’ve colored these fire bars grey to match the grey dots representing those years on the earlier climate chart. 

This chart shows that Californians only had to deal with megafires of this size once or twice per decade under the cooler, wetter, and more stable climate of the last century.

Megafires at the start of this century 

I’ve now added the second group of megafires. These burned during the first 16 years of this century. I’ve coloured these red to match the red dots representing those years on the climate chart. 

If you remember from that climate chart above, all those years were hotter than the twentieth century average. That has increased the odds of megafires during these years — and the dramatic increase is startling. This is what climate scientists mean when they warn that a little bit of warming leads to a lot more fire.

Understanding this is critical for our future safety. We need to understand that wildfire will respond non-linearly to our warming, when we decide how to prepare for the future. And we need to understand it when we decide whether to burn fossil fuels or choose an alternative.

The takeaway message, for me, is that however bad it seems now, it will grow dramatically worse if we keep overheating the climate further.

Which brings us to the final group of megafires…
 

Megafires in the last eight years 

I’ve added the final group of megafires — those from the last eight years. I would say that qualifies as a non-linear response. Or in less techie terms: holy $#!%.

That crazy pile of megafires from the last eight years burned during fire seasons that were hotter than any in the last century. Nearly all burned during 2017, 2018, 2020 and 2024, the four most extreme hot-and-dry fire seasons ever. I circled those in the earlier climate chart.

Because this is already a long article, I’m only going to highlight one aspect of those crazy years — the fire chaos of 2020. 

To provide scale, remember how there were only seven megafires over 110,000 acres during the last century (the grey bars on the top 40 fire chart above). Combined, these burned around one million acres. 

Well, ten of these megafires burned in 2020 with the largest torching more than a million acres on its own. Combined, those 10 burned over three million acres. And five of them ended up among the state’s six largest on record at that point. 

When you get hit by a century of megafires in a single year, you know the monsters are winning.

(Note: there are a lot more interesting lessons to learn from the unprecedented megafires chaos of the last eight years. For readers interested in a deeper dive, see the “extended content” section at the end of the article).

The future…

What I’ve hoped to illustrate with these charts and information is how global warming is loading the climate dice to roll ever more frequent and extreme hot-and-dry conditions. And how wildfire is responding with accelerating frequency and fury. 

Hopefully, by understanding these trends, we can better prepare for our future, whether we live in California or not. Because this isn’t just happening in California. It’s happening in many regions and ecosystems around the world. That includes here in Canada where surging wildfire is transforming our forests into net carbon emitters. Regardless of where we call home, nobody wants their neighbourhood to burn down, their families displaced for months, or their livelihood vaporized. And nobody wants to force a dystopian future on their kids and grandkids.

As it is, our current level of global warming is already creating unheard of superpowers in the biggest monster fires. They burn hotter, faster and more aggressively. They’ve started turbocharging themselves by conjuring up their own extreme fire weather — like ember superstorms, fire tornadoes, internal hurricane force winds, and pyrocumulus clouds that spit lighting. These monsters have started to escape the fire season, and they are now showing up in swarms. Perhaps, the monsters' most dangerous new superpower of all is their dramatic increase in speed. Research shows that the fastest burning fires have more than doubled in speed in the western United States since 2000. And these superfast fires destroy the vast majority of homes. Their unprecedented speed allows them to escape containment and invade towns and cities.

This is what John Vaillant calls “21st century fire,” in his award-winning book “Fire Weather.” The fire beasts are growing bigger, more formidable and harder to contain.  

During California’s epic 2020 fire season, Philip B. Duffy, a climate scientist and president of the Woodwell Climate Research Center, told the New York Times: “People are always asking, ‘Is this the new normal?’ I always say no. It’s going to get worse.”

How much worse it gets depends on how many more tonnes of planet-heating gases humanity decides to release. That’s because global warming is a one-way street. We’ve packed the kids and all future generations into the backseat, and we are driving onward into a hotter future. How much farther we drive into the overheating Pyrocene before we stop the car depends on our total cumulative emissions over time. Or, as the Intergovernmental Panel on Climate Change (IPCC) states clearly: “every tonne of CO₂ emissions adds to global warming.”

In short, whenever we burn fossil fuels, we feed the monsters attacking us. 

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Extended Content – I think there are many lessons we can learn by studying how megafires have changed over the last eight years in California. For those who are interested in a deeper dive than provided above, I’ve included a more in-depth discussion below. At the very bottom are some endnotes covering a few key fire studies that I’ve found helpful.

The climate of the last eight years, revisited.

To refresh our memories, I’m bringing back the climate chart for California’s fire season. 

The five years circled on this chart are when all these megafires burned. As you can see, all these years were hotter than any fire season in the last century. And the four in the upper left had the most extreme hot-and-dry combinations on record. Extreme fire conditions breed extreme fires.

2017 – the biggest, latest, and the most destructive.

This chart shows the megafires up to 2017.  

Thomas Fire: the biggest and the first outside fire season

As we saw at the top of the article, the Thomas Fire rampaged through suburbs just north of Los Angeles in December 2017, burning a then-record 282,000 acres. This fire was a climate wake-up call for many, because it was the first megafire to burn outside California’s traditional "fire season." That meant global warming was now pushing critical fire weather into the “rainy season.” This is proving to be especially dangerous on the south coast because it overlaps with the region’s annual Santa Ana windstorms. That combo supercharged the Thomas Fire. And our overheated climate dice rolled that same combination again in 2024. That time, it spawned the Los Angeles firestorm. Two for two. That’s important to know because it warns us that this formerly unheard-of combination is going to come back repeatedly in our overheated climate.

Tubbs Fire: record destruction.

In October of 2017, more than a dozen major fires erupted across northern California. One of them, the Tubbs Fire, shocked Californians as it incinerated entire neighbourhoods in the city of Santa Rosa and beyond. 

While it didn’t grow to be one of the state’s largest fires, it was California’s most destructive in the modern era. It destroyed more than 5,000 structures, killed 22 people and caused more than a billion dollars in damage. 

2018 – even bigger and more destructive

The extremely hot-and-dry 2018 fire season was the first to host three of the state’s all-time top 40 megafires in the same year. 

Mendocino Complex Fire: a new level of huge. 

The largest of the three was the Mendocino Complex fire. It jumped off the charts, burning nearly 460,000 acres. As you can see, this was a giant leap above any fire on record. It started when a rancher was driving a metal stake into the ground. A spark jumped off and ignited the bone-dry landscape faster and more furiously than modern firefighting technology and crews could contain.  Driving metal stakes into the ground isn't new. But such extreme hot-dry fire conditions are.

Carr Fire: a flat tire burns a thousand homes. 

The second-largest wildfire that year was the Carr Fire. It was sparked by a flat tire on a highway. Yeah, those happen all the time. But the extreme heat and dry conditions baking California that fire season whipped the sparks thrown from the wheel’s rim into a house-eating monster that burned more than a thousand homes. 

Camp Fire: a new level of death and destruction.

In November 2018, the Camp Fire erupted with stunning speed and ferocity. This satellite photo was taken just five hours after the fire started. By the end of the day, the town of Paradise and much of the nearby communities of Magalia, Butte Creek Canyon, and Concow had been overrun and burned down. 

This was only the second time that a fire outside the traditional fire season was able to burn its way into the state’s top 40 largest list. The first, as we saw above, was the Thomas Fire the year before. The monsters have started attacking in winter.

The Camp Fire would go on to become the state’s deadliest and most destructive wildfire -- killing 85 people and destroying more than 18,000 structures. The damages exceeded $16 billion. 

That month, Governor Jerry Brown held a press conference warning: “This is not the new normal. This is the new abnormal … Unfortunately, the best science is telling us that dryness, warmth, drought, all those things, they’re going to intensify … We have a real challenge here threatening our whole way of life...”

Even with that warning, few people were prepared for what 2020 would bring.

2020 – a century in one year.

An all-new level of hot-and-dry baked the 2020 fire season. And the monsters attacked in overwhelming numbers and scale.

The swarm: ten in one year.

To provide some scale for the fire chaos that year, consider that there were seven megafires larger than 110,000 acres during the last century. Combined, they burned around one million acres. In 2020, there were ten of these megafires. Combined, they burned three times as much — more than three million acres.  Five of them were among the six largest on record.

By the end of 2020, thousands of wildfires had combined to torch over four million acres in California – roughly four per cent of the entire state burned. That was more than double the single-year record set only two years earlier. 

A 2020 study found that overall, the extent of the state's summer forest fires had jumped eightfold since the 1970s. That’s yet another red-flag warning that wildfire responds non-linearly to global heating.

August Complex Fire: a million acres. 

The largest of the 2020 megafire swarm was the August Complex Fire that burned more than a million acres. That was more than double the previous record set in 2018 by the Mendocino Complex Fire. 

What seemed like a science-fiction scenario just a few years earlier — a million acre megafire and a century-topping swarm in a single year — had arrived with bewildering speed. The Los Angeles Times called it “California’s climate apocalypse”.  In 2020, the hot-and-dry conditions that spawned all this fire chaos were unprecedented. But our overheated climate dice will keep rolling out many similar years in the future. 

2021 – up and over the mountains.

In 2021, four more of the all-time top 40 megafires burned. Under the old climate, that would have taken decades.

The Dixie Fire: the state’s largest single fire. 

The largest was the Dixie Fire. At nearly a million acres, it smashed the record as the largest single-source wildfire in California history. 

It started when a tree fell across a powerline. That’s a commonplace occurrence. It happens all the time where I live. What has changed is the arrival of extreme levels of heat and parched landscapes that can turn the commonplace into an uncontrollable firestorm like this. 

The first fire to breach the Sierras.

The Dixie rewrote the record books in yet another troubling way. It was the first fire in recorded history to burn its way up and over the Sierra Nevada mountain range. That showed that the monsters had grown powerful enough to break through yet another barrier that used to contain them. And, in a pyro-flex, the Caldor Fire repeated the feat just a couple weeks later. 

NOAA notes that "extreme fire behavior during this period shocked many wildfire managers ... flame fronts threw embers over the crests of mountain divides, across miles of rocky and inflammable terrain, one more behavior never before observed by wildfire managers."

2024 – explosive speed. 

That brings us to the most recent fire season of 2024. As we saw on the climate chart above, this was the most extreme hot-and-dry combo so far. And July 2024 was blistering hot — the hottest month ever recorded in California.

The Park Fire: uncontainable speed. 

The record heat in July spawned the Park Fire. The initial cause was a car fire in a Chico city park. Even though multiple witnesses reported it immediately and firefighters responded quickly, the extreme fire weather conditions allowed this monster to escape capture. 

During the first 12 hours, it grew at the rate of 4,000 acres per hour. To give you a sense of how explosively fast this fire was, consider that the Thomas Fire just a few years earlier was the largest on record at the time. It was driven by raging Santa Ana winds and took a month to burn 280,000 acres. It felt apocalyptic at the time. The Park Fire burned more acres in the first three days. When it was finally put out, it had torched 430,000 acres. 

The Park Fire highlights one of the most dangerous superpowers that our fossil fuel burning is bestowing on the monsters attacking us — breakneck speed. 

A recent study found that the small fraction of fires that are the fastest burning has accounted for the vast majority of homes burned in the United States since 2000. This study also found that the maximum fire speed has more than doubled in the western United States in just the last two decades. In California, the fastest fires now burn four times faster. 

By overheating the climate, we are producing wildfires with uncontrollable speed. These superfast fires are outracing our efforts to stop them before they invade our cities and towns. They are starting to attack faster than humans can get away. 

The Los Angeles firestorm: record destruction.

Finally, as we saw at the start, the extreme hot-and-dry conditions of California’s 2024 fire season continued into the winter on the south coast. As I mentioned earlier, these conditions allow extreme wildfires to erupt when the Santa Ana windstorms are blowing. This tag-team combo didn’t happen in the past. It has now happened twice — in 2017 and again this January. Both times resulted in unprecedented fire monsters — the Thomas Fire and the Los Angeles firestorm. And now, thanks to our fossil fuel burning, this combo will keep coming back repeatedly. 

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ENDNOTES

For those readers looking for more science links about this crisis, I’ll end with some studies that I’ve found informative.

Climate change is driving the wildfire crisis.

A study, funded by NOAA, found that "climate change is to blame for record-breaking California wildfires." It concludes that "nearly all the observed increase in burned areas over the past half-century is due to human-caused climate change."

Another recent California fire study found that “climate has been the dominant controller of wildfire activity in the Sierra Nevada region in the past 1,400 years.” Researchers from Brown University studying ash layers in old lake sediments determined that warm and dry conditions were linked to increased wildfire as far back in time as the layers went.

Extreme hot-and-dry conditions load the dice.

A study, led by researchers from McGill University, found that "hot-dry extremes" are the conditions that breed explosive, hard to contain, megafires. The study documents how these hot-dry conditions are becoming increasingly common and more extreme in western parts of the United States due to climate change. 

Extreme heat alone can now dry the landscape.

That same study found that extreme hot-dry events are now occurring even when rainfall is close to normal. In our old lower-energy climate, extreme dryness only happened when there was a lack of rain. But global warming now produces heat waves so intense they evaporate enough water to create drought conditions on their own. That’s especially worrisome because rising temperatures are the most certain result of continued fossil fuel burning. 

Extreme heat creates an exponentially bigger “sponge”.

The water-vapor holding capacity of the atmosphere increases exponentially as it warms. That means dry air can suck lots more water out of the landscape as it warms. And conversely, wet air has more water to dump as rain as it warms.

Daniel Swain, a climate scientist in California, recently co-authored a study in Nature on how this phenomenon is turbocharging wildfires. In an interview with one of my favorite climate authors, Elizabeth Kolbert, he uses the analogy of an expanding atmospheric sponge that can pull more water out of the landscape. And he explains how the flip side of squeezing out more rain is increasing the biomass, which then turns to wildfire fuel during the dry years. 

Speed kills.

As I mentioned in the extended content above, a recent study found that the small fraction of fires that are the fastest burning has accounted for the vast majority of homes burned in the United States since 2000. This study also found that the maximum fire speed has more than doubled in the western United States in just the last two decades. In California, the fastest fires now burn four times faster.  

The fire season is changing.

Research shows that the average wildfire season in the Western U.S. is now 105 days longer, burns six times as many acres, and has three times as many large fires compared to the 1970s.

For more...

Read John Vaillant’s book Fire Weather. It’s the most comprehensive guide I’ve read on how fire is changing in our warming climate. Plus, it’s a riveting good read.