The fires that have been raging in Los Angeles County this week may be the “most destructive” in modern US history.

In just three days, the blazes have covered tens of thousands of acres of land and could potentially have an economic impact of up to $150bn (£123bn), according to private forecaster Accuweather.

Sky News has used a combination of open-source techniques, data analysis, satellite imagery and social media footage to analyse how and why the fires started, and work out the estimated economic and environmental cost.

More than 1,000 structures have been damaged so far, local officials have estimated. The real figure is likely to be much higher.

“In fact, it’s likely that perhaps 15,000 or even more structures have been destroyed,” said Jonathan Porter, chief meteorologist at Accuweather.

These include some of the country’s most expensive real estate, as well as critical infrastructure.

Accuweather has estimated the fires could have a total damage and economic loss of between $135bn and $150bn.

“It’s clear this is going to be the most destructive wildfire in California history, and likely the most destructive wildfire in modern US history,” said Mr Porter.

“That is our estimate based upon what has occurred thus far, plus some considerations for the near-term impacts of the fires,” he added.

The calculations were made using a wide variety of data inputs, from property damage and evacuation efforts, to the longer-term negative impacts from job and wage losses as well as a decline in tourism to the area.

The Palisades fire, which has burned at least 20,000 acres of land, has been the biggest so far.

Satellite imagery and social media videos indicate the fire was first visible in the area around Skull Rock, part of a 4.5 mile hiking trail, northeast of the upscale Pacific Palisades neighbourhood.

These videos were taken by hikers on the route at around 10.30am on Tuesday 7 January, when the fire began spreading.

At about the same time, this footage of a plane landing at Los Angeles International Airport was captured. A growing cloud of smoke is visible in the hills in the background – the same area where the hikers filmed their videos.

The area’s high winds and dry weather accelerated the speed that the fire has spread. By Tuesday night, Eaton fire sparked in a forested area north of downtown LA, and Hurst fire broke out in Sylmar, a suburban neighbourhood north of San Fernando, after a brush fire.

These images from NASA’s Black Marble tool that detects light sources on the ground show how much the Palisades and Eaton fires grew in less than 24 hours.

On Tuesday, the Palisades fire had covered 772 acres. At the time of publication of Friday, the fire had grown to cover nearly 20,500 acres, some 26.5 times its initial size.

The Palisades fire was the first to spark, but others erupted over the following days.

At around 1pm on Wednesday afternoon, the Lidia fire was first reported in Acton, next to the Angeles National Forest north of LA. Smaller than the others, firefighters managed to contain the blaze by 75% on Friday.

On Thursday, the Kenneth fire was reported at 2.40pm local time, according to Ventura County Fire Department, near a place called Victory Trailhead at the border of Ventura and Los Angeles counties.

This footage from a fire-monitoring camera in Simi Valley shows plumes of smoke billowing from the Kenneth fire.

Sky News analysed infrared satellite imagery to show how these fires grew all across LA.

The largest fires are still far from being contained, and have prompted thousands of residents to flee their homes as officials continued to keep large areas under evacuation orders. It’s unclear when they’ll be able to return.

“This is a tremendous loss that is going to result in many people and businesses needing a lot of help, as they begin the very slow process of putting their lives back together and rebuilding,” said Mr Porter.

“This is going to be an event that is going to likely take some people and businesses, perhaps a decade to recover from this fully.”

The Data and Forensics team is a multi-skilled unit dedicated to providing transparent journalism from Sky News. We gather, analyse and visualise data to tell data-driven stories. We combine traditional reporting skills with advanced analysis of satellite images, social media and other open source information. Through multimedia storytelling we aim to better explain the world while also showing how our journalism is done.

They are the displaced and there are tens of thousands of them, 600 in an evacuation centre we visited.

From elderly people who fled without their medication, to pregnant mothers desperate to escape the smoke, they had nowhere else to go.

Jim Mayfield, who has lived in the northern suburb of Altadena for 50 years, wept as he told me his dogs, Monkey and Coca, were all he had left.

He said: “The fire was coming down, a ball of fire, it hadn’t made it to my house, but then I woke up and I seen it so I had to start evacuating.

“I had to grab my dogs, I didn’t have enough water and my house is burned down to the ground.”

Sheila Kraetzel, another elderly resident, relived the sense of terror as homes were engulfed by the flames.

She said: “I smelt smoke, I was sleeping, and my dog alerted me that there was trouble.

“When I looked outside, there were embers floating across my yard.

“My whole neighbourhood is gone.”

“It was a beautiful, unique place,” she added, smiling.

Asked how she could smile, she fought back tears and replied: “Well, there’s tomorrow you know.”

How anyone could find hope amid the destruction we have witnessed here is beyond me.

Read more:
Scale of ‘most destructive’ blazes in modern US history
In pictures: Before and after the blazes
What caused the fires?

There are people handing out food and water, medical staff doing what they can. Volunteers have rallied from far and near.

One of them, Stephanie Porter, told me it felt “heavy” inside the centre.

“You walk through and see the despair on people’s faces, not knowing what their next step is, not knowing if their house is still standing,” she said.

“I had to take a few moments… and kind of cry, and then you go back to serve.

“It just breaks your heart.”

Three miles up the road, Altadena resembles a war zone, but residents have not been allowed to return.

When they finally do, they’ll discover there’s nothing left of the material lives they left behind.

Given gilt yields are rising, the pound is falling and, all things considered, markets look pretty hairy back in the UK, it’s quite likely Rachel Reeves’s trip to China gets overshadowed by noises off.

There’s a chance the dominant narrative is not about China itself, but about why she didn’t cancel the trip.

But make no mistake: this visit is a big deal. A very big deal – potentially one of the single most interesting moments in recent British economic policy.

Why? Because the UK is doing something very interesting and quite counterintuitive here. It is taking a gamble. For even as nearly every other country in the developed world cuts ties and imposes tariffs on China, this new Labour government is doing the opposite – trying to get closer to the world’s second-biggest economy.

The chancellor‘s three-day visit to Beijing and Shanghai marks the first time a UK finance minister has travelled to China since Philip Hammond‘s 2017 trip, which in turn followed a very grand mission from George Osborne in 2015.

Back then, the UK was attempting to double down on its economic relationship with China. It was encouraging Chinese companies to invest in this country, helping to build our next generation of nuclear power plants and our telephone infrastructure.

But since then the relationship has soured. Huawei has been banned from providing that telecoms infrastructure and China is no longer building our next power plants. There has been no “economic and financial dialogue” – the name for these missions – since 2019, when Chinese officials came to the UK. And the story has been much the same elsewhere in the developed world.

In the intervening period, G7 nations, led by the US, have imposed various tariffs on Chinese goods, sparking a slow-burn trade war between East and West. The latest of these tariffs were on Chinese electric vehicles. The US and Canada imposed 100% tariffs, while the EU and a swathe of other nations, from India to Turkey, introduced their own, slightly lower tariffs.

But (save for Japan, whose consumers tend not to buy many Chinese cars anyway) there is one developed nation which has, so far at least, stood alone, refusing to impose these extra tariffs on China: the UK.

The UK sticks out then – diplomatically (especially as the new US president comes into office, threatening even higher and wider tariffs on China) and economically. Right now no other developed market in the world looks as attractive to Chinese car companies as the UK does. Chinese producers, able thanks to expertise and a host of subsidies to produce cars far cheaper than those made domestically, have targeted the UK as an incredibly attractive prospect in the coming years.

And while the European strategy is to impose tariffs designed to taper down if Chinese car companies commit to building factories in the EU, there is less incentive, as far as anyone can make out, for Chinese firms to do likewise in the UK. The upshot is that domestic producers, who have already seen China leapfrog every other nation save for Germany, will struggle even more in the coming year to contend with cheap Chinese imports.

👉 Tap here to follow Politics at Jack and Sam’s Daily wherever you get your podcasts 👈

Whether this is a price the chancellor is willing to pay for greater access to the Chinese market is unclear. Certainly, while the UK imports more than twice as many goods from China as it sends there, the country is an attractive market for British financial services firms. Indeed, there are a host of bank executives travelling out with the chancellor for the dialogue. They are hoping to boost British exports of financial services in the coming years.

Still – many questions remain unanswered:

• Is the chancellor getting closer to China with half an eye on future trade negotiations with the US?

• Is she ready to reverse on this relationship if it helps procure a deal with Donald Trump?

• Is she comfortable with the impending influx of cheap Chinese electric vehicles in the coming months and years?

• Is she prepared for the potential impact on the domestic car industry, which is already struggling in the face of a host of other challenges?

• Is that a price worth paying for more financial access to China?

• What, in short, is the grand strategy here?

These are all important questions. Unfortunately, unlike in 2015 or 2017, the Treasury has decided not to bring any press with it. So our opportunities to find answers are far more limited than usual. Given the significance of this economic moment, and of this trip itself, that is desperately disappointing.