Underground climate change is weakening major cities across America including Chicago and NYC

Scientists have warned of a “silent danger” lurking underground that could bring down American cities like Chicago and New York.

A team from Northwestern University is calling the new phenomenon “underground climate change,” which they claimed is caused by the heat from underground man-made structures such as tunnels, parking garages and sewers.

The rising temperatures cause the ground to swell, contract, sink and crack, shifting buildings on the surface.

Researchers studied Chicago for the work and found that it has experienced a warming of 5.6 degrees Fahrenheit since 1951 and will sink eight millimeters by 2051 and swell by 12 millimeters.

And while the changes are subtle, the team notes in the study that it’s enough to disrupt infrastructure and other surface operations.

Northwestern’s Alessandro F. Rotta Loria, who led the study, said in a statement: “The ground deforms due to temperature fluctuations and no existing civil structure or infrastructure is designed to withstand these variations.

“Although this phenomenon is not necessarily dangerous for people’s safety, it will affect the normal day-to-day operation of foundation systems and civil infrastructure in general.”

Rotta Loria and his team installed a wireless network of more than 150 temperature sensors in the Chicago Loop in 2022 – both above and below ground.

These sensors were placed in basements, subway tunnels, underground parking garages and underground streets such as Lower Wacker Drive to collect temperature data in the region.

After collecting data, researchers found that underground temperatures under the Loop are often 10 degrees warmer than temperatures under Grant Park.

The heat from underground man-made structures such as tunnels, parking garages and sewers is released into the earth’s layers, causing the soil to swell, contract, sink and crack

The team will install a wireless network of more than 150 temperature sensors in the Chicago Loop in 2022 – both above and below ground.

“Air temperatures in underground structures can be up to 25 degrees higher compared to the undisturbed ground temperature,” the researchers said.

“When the heat diffuses to the ground, it puts significant pressure on materials that expand and contract with changing temperatures.”

Rotta Loria called Chicago a “living lab,” but notes that underground climate change is happening in most urban areas, such as New York City, which was recently determined to sink because of climate change — the ground is sinking and sea levels are rising around the huge island.

“All urban areas that suffer from subsurface climate change tend to have problems with infrastructure,” says Rotta Loria.

After collecting temperature data in Chicago, the team used the information to create simulations to predict how temperatures will evolve through 2051.

The team used the temperature data to see how they would evolve by 2051, showing that hard clay would experience the greatest increase

Warmer temperatures could cause the ground to swell and expand up to 12 millimeters, according to the simulations. They can also cause the ground to contract and drop by up to eight millimeters – under the weight of a building

Simulations were generated for 2022, which the researchers say “correspond with recent data collected from the heart of the Loop’s subsurface,” reads the study published in Nature.

Warmer temperatures could cause the ground to swell and expand up to 12 millimeters, according to the simulations.

They can also cause the ground to contract and drop by up to eight millimeters – under the weight of a building.

While the changes are subtle, the team said it would impact the operational performance of foundations, such as moving buildings.

“Based on our computer simulations, we have shown that ground deformations can be so severe that they lead to problems for the performance of civil infrastructure,” said Rotta Loria.

‘It’s not like a building suddenly collapses. Things sink very slowly.

‘The consequences for the usability of constructions and infrastructures can be very serious, but it takes a long time before you see them.

“It is very likely that subsurface climate change has already caused cracks and excessive foundation settlement that we did not associate with this phenomenon because we were not aware of it.”

However, the team believes that the Chicago River and Lake Michigan act as buffers to the observed increases in ground temperature, absorbing waste heat.

Rotta Loria also noted that subsurface climate change is unlikely to affect major European cities.

“In the United States, the buildings are all relatively new,” he said.

‘European cities with very old buildings will be more sensitive to subsurface climate change.

‘Stone and brick buildings that resort to design and construction practices of the past are generally in a very delicate balance with the disruptions associated with the current operations of cities.

“The thermal disturbances associated with subsurface heat islands can have detrimental effects on such structures.”