How are the LA wildfires linked to climate change?

Wildfires are devastating the city of Los Angeles, fuelled by a perfect storm of dry conditions and intense mountain winds. In this episode of Beyond the Ice, we break down the weather and climate mechanics behind this ongoing disaster. Climate scientist Dr Ella Gilbert and ice core scientist Dr Thomas Bauska discuss how our changing climate increases the risk of more frequent extreme events.

At the time of recording the episode on Monday 13 January, 12,000 buildings and about 40,000 acres of Los Angeles County were affected by wildfire - numbers that have only risen over the following week, as firefighting teams contended with continued challenging weather conditions. As the fires are brought under containment, our thoughts are with the communities affected and displaced.

In the second half of this edition, we take a step back in time to look at what new research into ice cores has recently revealed about major wildfires in Earth’s ancient past. How did scientists find out about wildfires that took place thousands of years ago? And can this tell us anything about the relationship between major climate shifts and wildfire events?

The discussion, in brief:

What are the factors driving the wildfires in Los Angeles?

The LA wildfires are unprecedented in the region for their combined ferocity and wide area - and this is due to a perfect storm of several years of vegetation growth, a period of dryness, and then fierce seasonal wind conditions. Climate scientist Dr Ella Gilbert broke down the factors at play:

"For the last few years, LA saw wet conditions - and there was a lot of rain and a lot of growth of vegetation. Two winters in a row, parts of Los Angeles recorded twice as much rain as a normal winter. So we had shrubs, trees, brush basically - and it means that there's a lot of fuel available to burn.

Then in 2024, it has swung strongly the other way, and we've had a very dry period. There has only been 7mm of rain since May 2024. Recently, about 60% of California has been classified as 'abnormally dry'. And that means that all of that vegetation dried out. So there's lots of fuel that's very flammable in the region around LA.

Then most recently, we've had these very strong mountain winds - known as Santa Ana or Föhn winds - that are formed when air gets forced over steep terrain like that surrounding LA. As it descends on the other side of the mountains, it is warm and dry - it reduces the humidity to something like 5 or 10%, which is really dry.

These warm, dry winds have also been really speedy: 60-80mph in some places. So once that trigger, once that spark was set and the fire had started, those winds were blowing embers a long way, so the fire spread really quickly. And that meant they were tearing through lots of the actual city, and causing these really horrendous scenes that we've been seeing in the news."

What's a Föhn wind?

Föhn winds are warm, dry winds that are formed when air gets forced over mountains. They are called different things in different parts of the world and in different mountain regions - you might hear them called Chinook winds, Santa Ana winds or Zonda winds. Ella offered a mental image to help understand the phenomenon:

"It's wherever you have air interacting with really steep terrain, and it causes all of the moisture to rain out or become clouds on one side of the mountain, so that when it travels to the other side, it's much drier.

And then this dry air gets squished because the atmosphere is denser at the bottom of the mountain. So it compresses all of that, kind of like if you're pumping up a bike tyre: if you're releasing the air, it gets colder, if you compress, it gets hotter. The atmosphere's pumping up the tyre and making the air warmer. So you get this warm, dry wind on the other side."

How do these extreme conditions relate to climate change?

On 13 January, a rapid assessment by researchers at UCLA has suggested that the fires would still have been extreme without climate change, but would likely have been somewhat smaller and less intense. Their early estimates are that climate change would account for about 25% of the fuel available for the fires, associated with "climate whiplash", or the year-on-year the intensity of changing weather conditions.

Taking a step back to global trends, we seem to be seeing an increase extremity, and more regular extremity of events. Ella explained what we mean by extremification in more detail:

"One of the primary effects of climate change is that it makes extreme events happen more frequently, it makes them happen with greater intensity, and for longer periods. Regardless of what they are - it could be wet extremes, it can be dry extremes, it could be hot extremes.

A warmer Earth means the air holds more moisture, so we have more water available for extreme rainfall. Rainfall can shift so you get much more water in one place - and that probably means you're getting much less in another and seeing more drought, drier drought conditions elsewhere. And we see these different patterns of change in different parts of the world.

In the case of wildfires, it's related to lots of those different extremes. Think of the fire triangle - you're adding heat to the system and you're also drying it out. So you're much more likely to get these sorts of wildfires happening when you do get a spark to light it."

Ella then talked about the way that climate change is making weather and temperature less predictable:

"Climate change is making things less predictable. It's changing the seasonality of the normal cycle that you would expect things to happen in, like weather. That's when your snows arrive, whether that's when the vegetation typically grows. All of those things are shifting as a result of changes to the climate. And that seasonality can be really key when we're talking about the occurrence of fires.

This is not the usual season for wildfires in California. But you do typically we see these Santa Ana driven winds in autumn and winter in California. So the properties of this January wildfire are a bit different to the ones you would see in the summer. And this is much more related directly to that sequence of weather."

What does the disaster in LA tell us about our readiness for the extreme conditions brought on by climate change?

On 9 January, the LA Times reported that fire hydrants ran dry, despite the fact that tanks used to store water for firefighting in the hills were filled to capacity. In this news piece, spokespeople from Los Angeles Department of Water and Power said that infrastructure was stretched by the need for water at many simultaneous locations. On top of this, the high winds were making it unsafe for firefighting tactics like using aerial drops of water and fire retardant.

Ella spoke about global readiness for more extreme weather and events:

"I would say that we have created systems to deal with the kinds of extremes that were extreme in an unchanged climate. We've become accustomed to a certain 'normal' and a certain degree of deviation from that normal, which would be the arrival of what we'd call a 1 in 100 year event. But because of how we're changing the climate, those extremes are getting more extreme and more regular.

We're just not ready for them. What's really difficult is that it's happening on so many fronts as well, it's not just wildfires. It's like whack-a-mole, and they are many, many moles popping up. It's happening so fast that it's really hard to keep up, and requires a lot of resources to adapt."

In order to adapt to this rapidly changing world, leaders need to be thinking realistically and ambitiously about what looking after human communities and wild places might look like in a rapidly changing world.

In the second part of this episode, Dr Thomas Bauska discusses new research about evidence of wildfires in previous periods of the Earth's geological history.

A new study published in the journal Nature on 2 January 2025 investigated ancient gases trapped in Antarctic ice, found markers of wildfires, and concluded that global increases in wildfire activity likely occurred during periods of abrupt climate change throughout the last Ice Age. Thomas is a co-author of the paper, which was led by Dr Ben Riddell-Young at Oregon State University.

What's an ice core?

Ice cores are cylinders of ice drilled out of ice sheets - very often for analysis in Antarctica or Greenland or other pole. They can be miles deep, depending on the depth of the ice sheet. Inside that ice is trapped information about the climate at the time that the snow fell - before it was compacting and turned into accumulating ice. The deeper you go, the further back in time you go. In particular, scientists look at air bubbles trapped in the ice - effectively air samples of the time.

How did they identify the wildfire events?

The study was looking to explain a series of bumps and wiggles in records of CO₂ and methane during the last ice age. Thomas set the scene:

"Earth was very different than today. Temperatures were cooler, and we had massive ice sheets sitting over places like Canada and most of the UK. So the climate was very different, and also quite variable - we have some evidence that Earth's climate reorganised itself really quickly within a few decades.

It's been one of my goals to try to figure out 'what's the fastest, biggest change we can ever have naturally, for carbon dioxide'. It turns out the fastest change we've ever seen for CO₂ happens within about a century, and it's a rise about 15 parts per million."

For context, these are still small bumps compared to the scale of human-induced emissions - around ten times slower than we see today. But this was still noticeable in the data.

Lead author, Ben Riddell-Young, measured the isotopes of methane for those periods - chemical fingerprints of where these gases came from. Thomas explained:

"The isotopes of methane are particularly sensitive to biomass burning - wildfire. He saw that most of the methane bump could be explained by a burst of wildfire, again, over maybe about a century or so. My role was to do some calculations to figure out the impact on carbon dioxide - because most of the gases released from a wildfire are carbon dioxide.

The greenhouse gas emissions from wildfires is almost diddly-squat compared to present-day fossil fuel burning. But this study shows these fire events were likely one of the cascading impacts from abrupt climate change events, and that they also have an emissions impact."  

Can we make an educated guess about what was going on when these ancient wildfires took place? Can it tell us anything about today?

"We were seeing a reorganisation of climate at the time," says Thomas. That's one common factor with today. But otherwise, it isn't exactly like what we'd see in the future. He continued:

"The problem with actually linking that past with now is that it is the opposite signal of what we're seeing today. So today, the Arctic is warming a lot, sea ice is declining. It's not the same forcing either - then, it was big fluctuations in the ocean. What's driving climate change today is greenhouse gases.

In these past wildfire events, one scenario is that you start off with these massive armadas of icebergs leaving the North Atlantic. A bunch of freshwater gets dumped into the ocean, it shuts off ocean circulation, the northern hemisphere cools a lot. The southern hemisphere warms. So you have this sort of asymmetric pattern, an extreme scenario. The rainfall belts of the tropics, what we call the Intertropical Convergence Zone, shifts south to an extreme that we don't see today. The southern hemisphere probably got wetter at this time. The northern hemisphere, where most of the land was a much drier. So essentially, their main northern hemisphere landmass dried out and fire was enhanced."

How well are wildfires currently modelled into our predictions for a warmer world?

Both Thomas and Ella confirmed that wildfire is very difficult to model and account for. Ella contextualised this with work she's doing on modelling a future Arctic:

"It is really difficult to model fires, especially when we're talking over many decades, or we're talking over large spatial scales as well. One of the things that the project I work on is also looking at is the risk of wildfires in the Arctic - especially as the permafrost changes and as the terrestrial land based environment changes and shifts in response to climate change in the Arctic.

Can we say what the risk will be yet? No - it requires really state of the art modelling, which is what we're currently working on. It's this perfect confluence of so many different factors. It's environmental, it's climate, it's weather. It's also land use. It's the human interaction with the landscape - it's politics, it's economic factors. There are so many things going on that makes it a really challenging question to answer."

The BEYOND THE ICE podcast from British Antarctic Survey is available on all podcast platforms, and is embedded at the top of this article.

• Dr Thomas Bauska is an ice core scientist, and Royal Society University Research Fellow at British Antarctic Survey. His research uses the climate and carbon cycle variability of the past to inform projections of the future. He uses isotopes of greenhouse gases trapped in polar ice cores to reconstruct past changes in the carbon cycle.
• Dr Ella Gilbert is a climate scientist and regional at British Antarctic Survey. Her research explores how the Arctic and Antarctic climates may change in response to climate change, using high-resolution regional models, with a particular specialism in atmospheric processes. Ella is also a busy science communicator across news media, social media, and documentary.