Underneath major global cities, a hidden and concerning threat called “subterranean climate change” is silently impacting the stability of urban areas. The consequences of this underground phenomenon are gradually revealing themselves, as buildings and infrastructure were not originally designed to withstand its effects. In a groundbreaking study by Northwestern University, researchers have established a link between subsurface climate change and the shifting ground beneath cities. The study highlights the potential long-term consequences for infrastructure and presents an opportunity to mitigate the impact through innovative approaches. Published in Communications Engineering, this research is the first to quantify the effects of subsurface heat islands on civil infrastructure.
Impact on Buildings and Infrastructure:
As the ground beneath urban areas warms up, it undergoes deformation, resulting in excessive movement and even cracks in building foundations and surrounding ground. Northwestern University researchers have found evidence suggesting that past building damage may have been caused by rising temperatures, and they anticipate these issues will persist in the future. While this phenomenon does not pose an immediate threat to human safety, it significantly impacts the day-to-day functionality and durability of foundational systems and civil infrastructure.
Understanding Underground Climate Change:
Underground climate change, also referred to as subsurface heat islands, occurs when heat from buildings and underground transportation systems continually permeates the ground, causing it to warm rapidly. Previous research has indicated temperature increases of 0.1 to 2.5 degrees Celsius per decade in the shallow subsurface beneath cities. This underground phenomenon has been known to create ecological and health issues, such as contaminated groundwater, asthma, and heatstroke. However, until now, the specific impact on civil infrastructure remained unexplored.
Chicago as a Case Study:
To investigate the effects of underground climate change, Northwestern University conducted an extensive study in the Chicago Loop. Over three years, a wireless network of more than 150 temperature sensors was deployed both above and below ground, including basements, subway tunnels, underground parking garages, and subsurface streets. By comparing these measurements with sensors in Grant Park, a greenspace away from urban structures, researchers discovered that temperatures underground in the Loop were consistently 10 degrees warmer. This disparity in temperatures places significant stress on materials that expand and contract in response to changing conditions.
Implications for Civil Infrastructure:
Utilizing computer simulations, the research team projected the evolution of ground temperatures and the corresponding deformation until the year 2051. Their models indicated that warmer temperatures can cause the ground to expand upward by up to 12 millimeters or sink downward by up to 8 millimeters beneath the weight of buildings. Although these changes are subtle and imperceptible to humans, they exceed the tolerances of many building components and foundation systems, compromising their operational requirements over time. The study suggests that underground climate change may have already contributed to cracks and excessive foundation settlements, previously unattributed to this phenomenon due to lack of awareness.
Harnessing Heat for Mitigation:
While modern buildings are better equipped to withstand temperature variations, older structures, particularly those in European cities, are more susceptible to the effects of subsurface climate change. To address this challenge, researchers propose integrating geothermal technologies to capture and utilize waste heat emitted by subterranean transportation systems, parking garages, and basement facilities. By doing so, urban planners could mitigate the impact of underground climate change and tap into an untapped thermal energy resource. Additionally, incorporating thermal insulation in both existing and new buildings can minimize the transfer of heat to the ground, further mitigating the effects on infrastructure.
The study by Northwestern University sheds light on the silent hazard of subterranean climate change, which poses a significant threat to urban stability. Understanding the impact on civil infrastructure is crucial for developing effective mitigation strategies. By incorporating geothermal technologies and thermal insulation, cities can minimize the effects of underground climate change and harness its potential as a sustainable energy source. Awareness and proactive planning are vital for creating resilient urban environments that can adapt to the challenges posed by a changing climate.
Frequently Asked Questions (FAQs) about subterranean climate change
What is subterranean climate change?
Subterranean climate change refers to the phenomenon where the ground beneath urban areas experiences rapid warming due to heat diffusion from buildings and underground transportation systems. It can cause ground deformation and impact the stability of buildings and infrastructure.
How does subterranean climate change affect buildings and infrastructure?
Subterranean climate change leads to ground deformation, causing excessive movement and even cracks in building foundations and surrounding ground. Over time, these effects can compromise the long-term performance and durability of civil infrastructure.
Has subterranean climate change already caused damage to buildings?
The study suggests that subterranean climate change may have already contributed to cracks and excessive foundation settlements in buildings, which were previously not attributed to this phenomenon due to a lack of awareness.
Can subterranean climate change be mitigated?
The study proposes using geothermal technologies to capture and reuse waste heat emitted by underground transportation systems, parking garages, and basement facilities. Additionally, incorporating thermal insulation in buildings can minimize the transfer of heat to the ground, mitigating the effects of underground climate change.
Are all urban areas affected by subterranean climate change?
Yes, underground climate change is common to nearly all dense urban areas worldwide. Any urban area experiencing subsurface heat islands is prone to problems with infrastructure and may benefit from strategies to mitigate its impact.
How can awareness of subterranean climate change help urban planning?
Understanding the impact of subterranean climate change on infrastructure is crucial for developing effective mitigation strategies. Awareness allows urban planners to incorporate geothermal technologies, thermal insulation, and other solutions into their designs to create resilient and sustainable urban environments.
More about subterranean climate change
- Northwestern University Study: Link to the study
- Communications Engineering Journal: Link to the journal article
- National Science Foundation: Link to the NSF website