Scientists have warned against a danger lurking undergroundthis could cause the fall of US cities such as Chicago and NY. A team from Northwestern University calls out the new phenomenon “climate change Underground”which they claim is caused by heat from underground man-made structures such as tunnels, parking lots and sewers.

Rising temperatures cause the ground to swell, contract, sag and crack, displacing buildings on the surface. The researchers studied the city of Chicago for the work and found that it has experienced a warming of 5.6 degrees Fahrenheit since 1951 and is expected to sink 8 millimeters and swell 12 millimeters by 2051. And while the changes are subtle, the team notes in the study that it’s enough to damage 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 variations 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 the foundation systems and civil infrastructure in general.”

Rotta Loria and his team will install 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, underground tunnels, subterranean parking garages and underground streets such as Lower Wacker Drive, to collect temperature data in the region.

After collecting data, the researchers found that underground temperatures under the Loop are often 10 degrees warmer than temperatures under Grant Park. “The air temperature in underground structures can be up to 25 degrees higher than the undisturbed ground temperature. When heat diffuses into the ground, it exerts significant pressure on materials that expand and contract with temperature changes,” the researchers said.

Rotta Loria called Chicago a “living laboratory,” but notes that subsurface climate change is happening in most urban areas, such as New York City, which was recently determined to perish due to climate change: the ground is sinking and the sea level is rising around the huge island.

“All urban areas suffering from subsurface climate change are prone to infrastructure problems,” said Rotta Loria. After collecting temperature data in Chicago, the team used the information to create simulations to predict how temperatures will evolve through 2051. Simulations for 2022 were generated, which the researchers say “correspond with recent data collected from the heart of the underground loop,” reads the study published in Nature.

According to simulations the warmest temperatures they can cause the soil to swell and expand up to 12 millimeters. They can also cause the ground to contract and sink, under the weight of a building, by up to eight millimeters. Although the changes are subtle, the team said this would impact the operational performance of the foundation, such as changing the buildings.

“It’s very likely that subsurface climate change has already caused excessive cracking and subsidence in foundations that we didn’t associate with this phenomenon because we weren’t aware of it.” However, the team believes that the Chicago River and Lake Michigan act as buffers to observed increases in ground temperature, absorbing residual heat.

A possible solution

Another study puts forward a theoretical idea of ​​using this heat seeped into the ground to heat homes. during colder times, in the winter. This heat can be recycled via groundwater pipes to surface heat pumps, which can then transfer that heat to cooler interiors.

The researchers believe that heat recovery will be feasible in most suburban areas have sufficient stored underground heat that can be utilized to meet local needs and enough space to install recycling equipment.