Kostas Lagouvardos and his colleagues at the Penteli Observatory, which offers sweeping views of Athens, are what you would call experts on wildfires. They have spent decades researching the link between meteorological conditions and deadly infernos, as well as tackling the challenge of forecasting when and where the disasters might happen.
But even they were caught off-guard by the wildfire that arrived at their door last August. “It was ironic,” says Lagouvardos, research director at the Institute for Environmental Research and Sustainable Development at the National Observatory of Athens.
The Penteli site, which forms part of the NOA and is home to the historic Newall refractor telescope, was almost engulfed by a blaze that spread from nearby Mount Pentelicus.
Flames whipped around the grounds, coming within metres of the astronomy tower and other buildings, as helicopters dropped water from above and firefighters below battled to save the crucial scientific site. The observatory buildings were spared, but its nearest neighbour was badly damaged, as were many other buildings in the area. One person died.
The fact that a wildfire came so close to the very building where scientists had long attempted to understand the phenomenon highlights the key challenges for cities around the world as extreme weather intensifies. Not only are wildfires becoming more common, they are difficult to predict and are spreading ever closer to densely populated urban areas. Just last week, Israel’s Prime Minister Benjamin Netanyahu warned that wildfires in the country were at risk of reaching Jerusalem.
“The fire was a shock for many people,” says Lagouvardos. Although the Attica region in which the Greek capital is located has suffered with many wildfires in recent years, fuelled by record-breaking temperatures, “it was the first time [a blaze] was so close to the city”.
Ultimately, Athens, whose wider metropolitan area is home to 3.6mn people, escaped a catastrophic wildfire — but only just. “What was missing was the wind element,” says Thomas Smith, associate professor in environmental geography at the London School of Economics and Political Science, singling out a critical factor that can escalate a wildfire from manageable to devastating.
But Athens, like other big cities including Dallas, Lisbon, Sydney and Cape Town, are what some scientists refer to as “sitting ducks”. In these places, the climate and geographical conditions mean they are extremely vulnerable to global warming-related disasters. This could be wildfires, like those in Los Angeles in January, but also flooding, as seen in Valencia last year. In some cases, one can follow the other.
These so-called sitting ducks “haven’t had an extreme event” so far, says Erin Coughlan de Perez, a professor at Tufts University, an expert in climate risk. “They’ve got lucky.”
But the odds might be against them. With 2025 expected to be one of the hottest on record, despite a cooling La Niña weather phenomenon earlier this year, scientists warn of a rising risk of climate-related disasters.
Climate change is causing a rise in extreme heat, which helps fuel wildfires, while hotter temperatures can also lead to more intense rainfall and flooding, because warmer air holds more moisture.
Research has found the hot, dry and windy conditions that drove the LA fires were about 35 per cent more likely due to climate change. In the case of Athens, modelling by NOA’s Christos Giannakopoulo shows that, under a “business as usual scenario” where little progress is made on cutting greenhouse gas emissions, the city is on course to have up to 40 more days with maximum temperatures above 35C each year by 2050 compared with the period from 1981 to 2000.
Scientists are now attempting to assess which cities are most at risk of floods, wildfires, severe localised heat and other extremes — and where the next disaster could be mapped. This is also a question preoccupying insurance modellers as the industry attempts to future-proof their business.
“Those types of phenomena at a local scale are extremely rare,” says Guillermo Rein, a fire sciences professor at Imperial College London, likening it to a black swan. “It’s almost impossible for anyone to say, ‘This is going to happen in Athens this summer.’
“But at the global level, they are becoming more probable,” he adds. “In the next year there’s going to be a big wildfire destroying a big community. But we have absolutely no idea where that is going to happen.”
In Athens, Lagouvardos and his colleagues are doing what they can to get more certainty. As he outlines the charred path of last year’s fire, he points to a mountain in the distance. “I think it will be next,” Lagouvardos says, referring to the potential starting point of Athens’ next wildfire.
Mount Hymettus, rising above the east of the city, is dotted with historic monasteries and pine forest. Simulations made with his colleague Theodore Giannaros, an atmospheric modeller, show how a fire starting on the northern foothills of Hymettus would make “very fast progress” if fanned by strong winds, Lagouvardos says.
Using the mountain’s dry forest and vegetation as a fuel source, the flames could quickly make their way down towards the city, near to an area housing the University of Athens.
“This is very close to the city limits,” he says, adding that while the mountain is “heavily protected” when there is a risk of fire, a blaze “can happen”.
The wider Athens area, like other sitting ducks, has the “perfect mix” of elements needed for a significant wildfire, says Joe McNorton, land surface modeller at European Centre for Medium-Range Weather Forecasts. Wildfires need fuel often in the form of vegetation, an ignition source such as extreme heat or a man-made fire, and the right weather conditions, he says, including strong winds.
All of this is exacerbated by urban sprawl. While forest fires are not a new phenomenon, having been part of Earth’s ecosystem for millennia, more people now live close to potentially large sources of fuel.
Since the 1950s, construction in Athens has spread from its compact historic city centre, with new low-rise buildings edging ever closer to the mountains, hills and sea that surround the area.
This has helped create a bigger wildland-urban interface or rural-urban interface — the area where buildings and wildlands meet or intermingle and is a flash point for fires.
Although such interfaces cover only 4.7 per cent of the planet’s land surface, they are home to 3.5bn people — almost half the world’s population, according to research from 2023. In Europe, this area represented 15 per cent of the continent’s land, according to a study published in the science journal Nature.
In these zones, human activity can inadvertently spark a wildfire and, because of the population concentration, those blazes then pose a bigger risk to people and property.
Erratic weather patterns are also making wildland more flammable. In the case of LA, the city had experienced an exceptionally wet period that led to the abundant growth of scrubby vegetation. This was followed by a prolonged drought that dried up the plants, creating fuel for a blaze.
It was the perfect storm. Fires raged across 55,000 acres, claiming at least 30 lives, destroying more than 16,000 structures and causing hundreds of billions of dollars in damage and economic loss.
A similar situation could play out in Athens, scientists warn, where a period of rain followed by drought would ensure an abundance of fuel. As well as pine forest, which often dries during summer heatwaves where temperatures can hit more than 40C, shrubby vegetation is also common in the region. This has increased as agriculture has declined, with the loss of goats and sheep that traditionally kept vegetation under control, says the LSE’s Smith.
The proliferation of vegetation on the edge of Athens — or in other cities — often means “there are no natural firebreaks to stop the fire from propagating”, says McNorton, the modelling expert.
Then there are the wind conditions. Like the powerful Santa Ana winds that stoked the LA wildfires, Athens is subject to the strong, northerly and dry Meltemi winds that blow in the Aegean Sea region. They typically occur during the summer months when the wildfire risk is at its highest.
In 2018, a wind-whipped blaze burnt a ferocious path from the Penteli area to the coastal town of Mati in Attica, killing 103 people — making it one of the most deadly wildfires of the 21st century. Strong winds also fanned the 2023 Hawaii wildfires that claimed at least 102 lives.
“When there is no high wind, in modern times, fire brigades can stop them,” says Rein. “The fires that no one can stop, they happen when there are high winds.”
As well as the initial assault, wildfires have long-term consequences. Flames burn away vegetation, making the soil less permeable and unable to absorb water, leading to more surface run-off and faster-moving floodwaters.
“A wildfire might damage the suburbs, especially the green ones, but the problem doesn’t end there. There is an elevated risk of floods,” says Michalis Diakakis, an expert on climate-related disasters and extreme events at the University of Athens.
This risk lasts for up to a decade after a fire in some areas, according to research by Diakakis, and can be far more damaging to city centres. “It is easy to block a critical river across a section, pushing water out and inundating the area. The flooding will eventually come down towards the city centre.”
At the Penteli Observatory, blackened trees have been felled and their trunks placed in a terrace-like pattern on slopes where the wildfire burnt last year to prevent flooding, debris flows or mudslides — secondary risks that can follow a wildfire.
The rapid urbanisation of Athens has left the city susceptible to flooding, says Firas Saleh, director of product management at the credit rating and research company Moody’s. “Many streams and rivers have been covered or built over, reducing the city’s ability to manage heavy rainfall.”
Other cities, several of which are in the US, face a similar risk, such as New York and urban areas in South Carolina, adds Saleh. Moody’s estimates that approximately 2.4bn people across the world live in locations that are at risk of inland river or flash flooding.
Houston, Dallas and Washington DC are all at risk of flash flooding, says Melanie Veltman, senior data analyst at Guidewire HazardHub, a technology platform used by the insurance industry. Climate change is increasing the frequency of such floods, because it “brings more short, intense downpours”, she adds.
In a flash flood, water “has nowhere to go and pools in low-lying areas, underpasses, basements and roads”, Veltman says, adding that they can happen anywhere and do not need a river or coast to cause devastation.
Dallas has ideal conditions for flash flooding. Over the past two decades, the city has grown rapidly, expanding into flood-prone areas with heavy use of impervious surfaces such as concrete and asphalt. Creeks and floodplains have been replaced by “pavement and structures that accelerate run-off”, adds Veltman.
At the same time, heavy rainfall is becoming more frequent and intense — a trend driven by warming air holding more moisture, according to the Environmental Protection Agency.
In August 2022, about 38cm of rain fell in 24 hours in parts of Dallas, causing flash flooding that overwhelmed homes and led to a surge in insurance claims. A quarter of the city’s housing units, or about 140,000 properties, are at risk of flooding, HazardHub data suggests.
Diakakis says that an initial climate disaster often has longer-term ramifications, such as hits to tourism that can affect local economies. “Our economic development is very tied to what happens in extreme disasters,” he adds.
Cities around the world are waking up to the long-term consequences of climate disasters.
“This issue is rising up the agenda,” says Cassie Sutherland, managing director for the climate solutions and networks team at C40 Cities, a network of urban areas concerned about climate change.
Rein, the Imperial College London professor, is also alarmed by rising wildfire risks in traditionally cooler, and greener, cities that have little experience of blazes, such as New York or urban areas in Germany and the Netherlands. “I worry more about London than I worry about Athens,” he says.
But there are growing efforts to use modelling or machine learning and other tools to help understand fire risk.
For about 50 years, Canada has used the so-called fire weather index to model the risks of forest fires in its cities. Other countries use or have developed similar models, compiling information on fuel sources, humidity, temperature, precipitation and wind speed to calculate the likelihood and intensity of forest fires. The higher the index, the more favourable the meteorological conditions to trigger a wildfire, known as fire weather days.
Moody’s is among those that has created models used by the insurance industry and others to look at the risk of wildfires, floods and other disasters. Its models show that parts of Athens will become more vulnerable to wildfire and heat stress under different climate change scenarios.
“When wildfires reach suburban areas, the damage can vary significantly,” he adds. “The worst-case scenario involves urban conflagration, as was the case in the LA fires, where houses ignite one another, turning the structures themselves into fuel.”
This is less likely in Athens, where buildings are typically constructed of blocks, bricks and concrete, but is more of a concern in countries such as Australia, Germany and Scandinavia, where wood construction is common, experts say.
In some cases, cities are being redesigned to work better for the extremes of climate change — whether that is heat, flood or both, says Sutherland, at C40 Cities.
That is certainly true for Athens, says Nikos Chrysogelos, one of the city’s deputy mayors. As well as collecting data to better understand the risks, the city centre is focused on rolling out solutions to deal with extreme heat and flooding, as well as working with nearby municipalities that are at greater risk of fires, he says.
“We are late [in responding to the climate crisis], so we have to run. We have to take action very quickly,” he adds. “We do not have any alternative.”
But many feel the city is still unprepared. “Athens is not ready,” says Diakakis, arguing that the city has struggled to cope with “moderate” floods or wildfires and would struggle in the face of a more extreme event.
As the wildfire season gets under way, the country is on high alert. Greece’s civil protection and climate crisis minister Yiannis Kefalogiannis has announced that a record number of firefighters — about 18,000 — would be deployed this year alongside about 80 drones to help detect blazes across the country.
“We shouldn’t be fooled by the fact that climate conditions this year have seemed to be a little milder than in previous years,” he said. “The bad scenarios lie ahead.”