London is falling down, and it’s because of climate change

LONDON - Britain’s increasingly extreme weather is shaking the very foundations of its centuries-old history. 

The

nation has been experiencing prolonged periods of drought

after wet winters since 2022. That is causing the porous rock beneath vast parts of south-east England, including London, to move more than usual, cracking or tilting many of the city’s historical homes in the plushest neighbourhoods. The damage has triggered the highest insurance payout in almost two decades, with experts warning that it could get worse.

London clay, the type of soil that covers most of these areas, “is quite unique” because it can shrink and swell a lot, according to Mr Lee Jones, a geological engineer at the British Geological Survey who has studied British hazards for over 30 years. “The wetter it gets, the more it swells and expands, and the drier it gets, the more it shrinks and cracks,” he said, adding that future temperature extremes will exacerbate the impact on buildings and roads.

That phenomenon – known as subsidence – has become worse in Britain after 2022’s drought and a deadly heatwave that pushed temperatures past 40 deg C in July 2022 to record levels. Heat advisories are out for this summer, too, underscoring the vulnerability of London’s historical buildings, some of which have stood since the mid-1800s and survived World War II, including the Blitz which started in 1940 and saw the city being bombed for months.

London clay is the most susceptible to shrinking among soil types, meaning it has the highest risk of being a subsidence hazard. British insurers expect to pay £219 million (S$378 million) for subsidence claims made in 2022, “many of which were caused by last summer’s record-breaking high temperatures”, according to data published earlier in 2023 by the Association of British Insurers. This is the highest expected insurance subsidence bill since 2006, it said.

“We are expecting to see an increase in subsidence claims in coming months,” said Mr Anthony Baddeley, a network support manager at Aspray, a United Kingdom-based property loss assessor that helps people with insurance claims.

“Many properties within the UK are built on shrinkable clay, and this particularly dry weather can result in property shift.”

The hit from subsidence is most visible and costly in London, home to nine million people. Subsidence can dent the value of these homes, and severely damaged houses could even be unsafe for habitation. 

One in six homes in England was built before 1900, when engineering standards did not account for extreme temperatures. Also, while other parts of Europe underwent massive reconstruction after World War II, Britain’s historical buildings were comparatively unharmed, and that is why a much higher proportion of the housing inventory is of an older vintage. 

Climate risk data provider Climate X predicts increasing rates of subsidence due to climate change under higher or even current emissions trajectory, according to Dr Claire Burke, its director of science. In most other parts of the world, subsidence happens usually as a result of groundwater extraction, she said. 

According to a note published by Zurich Insurance Group in June, “the next six weeks will be key weather-wise in determining” whether there will be an increase in clay-related subsidence claims. The report pointed out that England had its driest February in 30 years in 2023, followed by its wettest March in over 40 years – a weather pattern that risks spiking insurance claims. There was a 26 per cent increase in overall claim volumes reported for the UK in 2022 compared with in 2021. The first five months of 2023 have already seen reported claim volumes jump 40 per cent versus the same period in 2022, the note said.

The tree-lined streets in the eastern parts of London are particularly prone to subsidence, according to Mr Jones, implying the clay there can expand and shrink more than in other areas. 

London Mayor Sadiq Khan’s office did not comment specifically on subsidence-related problems in response to questions. But a spokesman said Mr Khan is committed to ensuring the city is prepared to deal with the risks associated with climate change, including extreme heat. 

While climate change is not the only factor behind subsidence-related damage to buildings – tree roots also cause this by reaching deep and soaking all the moisture from the soil – erratic weather events, coupled with London’s unique clay, have certainly exacerbated the problem. 

Geological research is needed to figure out when the risk of subsidence is more likely, according to Mr Jones. It could mean pinning down a temperature threshold or a certain number of consecutive high-temperature days.

“What we need to find out is if there are trigger points and when exactly this happens,” he said. Then “we can use these trigger points to better advise and shape policy”. BLOOMBERG