‘Underground climate change’ is deforming the ground beneath buildings, study finds
Scientific Article: https://www.nature.com/articles/s44172-023-00092-1
“’Underground climate change’ is deforming the ground beneath buildings, study finds”, by Jacopo Prisco of CNN is a reaction to a Northwestern University study published in Communications Engineering. Both articles were released in July of this year, with the news article published a short six days following the scientific paper’s publication “The silent impact of underground climate change on civil infrastructure”, by Alessandro Loria. The ‘underground climate change’ referenced in the above articles are subsurface heat islands formed through the thermal contribution of buildings and infrastructure. The impact of these heat islands upon soil, rocks, and construction materials of the surrounding region leads to deformation. Loria’s research focuses on the impact and magnitude of subsurface climate change and this paper is concerned with the city of Chicago’s Loop District.
My initial impression of the CNN news article was quite positive. Prisco included a plethora of quotes from the study’s author as well as comments from professors at the University of Chicago and Durham University. The inclusion of such quotes is an excellent tool to offer direct insight from those involved in the study as well as the reaction of peers. Misunderstandings in the translation of material from scientific to public realms are minimized. The news article gave a basic outline of the methodology, including the important caveat that computer modeling was utilized for the study. While creating a sensationalized article would prove easy on this given topic, I was impressed that Prisco chose to echo the study’s assertion; that the observed underground climate change was not a threat to the safety of humans or likely to cause building collapse. The article’s primary focus was upon the phenomenon described and the limitation of its’ negative impact with new infrastructure development.
The scientific article utilizes an already existing network of surface and subsurface temperature sensors present within the Chicago Loop district since 2019. In order to model both temperature change and the alteration of deformation over the desired 1951-2051 timeframe, a 3-D, time dependent, thermo-hydro-mechanical finite element simulation was utilized in accordance with site explorations, surveys, and prior literature. Data from the Illinois State Geological Survey provided the boundaries of sand, soft clay, stiff clay, and hard clay present in the 3-D model. In the figure below the depth of z = 10, 17.5, and 23 m correspond to the average depths of soft, stiff, and hard clay layers underneath the represented district.
Within the study Loria explains that while the subsurface temperature has increased significantly over the past 70 years, it appears to be slowly approaching thermal saturation. While previous average ground warming rates reached 0.49 °C/yr, this has slowed to an annual rate of 0.14 °C/yr. The magnitude of deformation was correlated with the thermal pollution of a region. While soft and stiff clay layers were subject to contraction, the hard clay and sand layers expanded. Localized minimums and maximums reach up to +12 mm, and -8 mm respectively. Differential displacement within the millimeter scale provides cause for excessive settling of foundations or cracking of structural members. Historically, poor foundation design and construction methods were cited in cases of operation issues for buildings and infrastructure within the district, but Loria proposes that this thermal deformation of subsurface layers may be at fault. Loria proposes the harvesting of thermal power in instances where thermal insulation of buildings is not possible. The estimated 8 GWh harvested would provide only 0.5% of the 1824 GWh annual heating demands of large buildings within the Loop. Validation of the model was performed by comparing experimental data obtained from Grant Park and St. Charles with the numerical results. While the results of this comparison were satisfactory, they were only performed to a maximum depth of 4 m.
Overall, I rate this article’s representation of the scientific paper’s findings a 7.5/10. Author Prisco avoids sensationalizing the presented data. The news article largely keeps the same message of the scientific paper’s, which is that underground climate change may pose infrastructure issues long term, while health effects upon humans is largely unaltered. I was disappointed in the lack of discussion of deformation as opposed to temperature, the news article avoided much detail regarding the study’s modeling of deformation, however this was likely a good choice for news media. Loria admits within the study that the model for deformation is the most subject to simplification. The less definitive nature of these findings likely resulted in their exclusion from the news article.
The model used in the scientific article does seem to be a little complex so I can see why the news article left it out. How important is that model to the overall context of the study? How does Prisco leaving it out of his article affect the people who are reading it?
ReplyDeleteI also thought it was really interesting that the comparison study performed in Grant Park went only down to 4m when the original study went down to 23m. How were they able to get a satisfactory comparison when the depths were so different?
Regarding the overall context of the study, the model is important in that the reader is aware that computational estimations are used, based upon the 150 temperature sensors throughout the region. Loria chose to exclude the intricacies of the modeling, referencing a prior paper of his, 'Energy and geotechnical behaviour of energy piles for different design solutions', which fleshes out the methodology used. I had forgotten to include in my report the additional experimental data from the Loop which provided a maximum depth of 12 m. While the close match is reassuring, this distance is still 11 m short of the model's maximum depth. Unfortunately, all experimental data was taken from depths within the sand and soft clay layers, while the maximum modeled depth of 23 m passes through the stiff and hard clay layers (which provide additional sources for error).
DeleteI agree that the inclusion of both statements from the authors of the study as well as thoughts from peers that weren't part of the study were a good addition. I also like that the author identifies who was involved and who wasn't so we have some idea of the authority behind each statement. The news article mentions the idea of using geothermal technologies to absorb heat waste underground, but does not say what kinds of geothermal technologies are being referenced or how they work. I would have liked to hear a little bit more information on that, because I have no background in that topic and am interested to know how that works.
ReplyDeleteWhile the scientific article does not mention specific geothermal technologies, Loria references a prior paper of his which provides further insight. In Loria's paper, 'The thermal energy storage potential of underground tunnels used as heat exchangers', he advocates for the use of existing underground tunnel infrastructure (such as subway and train lines). After thermal insulation is completed these energy tunnels are used as 'thermal batteries', with the benefit that no above ground land use is required. Although they are not the primary focus of the paper, aquifers and rock/gravel bed storage are mentioned as sources for further energy storage.
DeleteI'm surprised that Loria would claim that underground climate change would cause no threat to the collapse of structures or buildings, when not only the results of her study but even the rest of her own comment contradicts this. After claiming that underground climate change does not threaten the collapse of buildings or structures, she says “It does pose a potential challenge for the functionality and the durability of structures, because excessive ground deformations can lead to distortion, tilting and potentially cracking," which definitely sounds like a threat to the structural integrity of buildings. I am not sure why she would want to downplay the severe implications of her results, maybe there are some more powerful players that aren't too pleased with increasing costs to repair buildings...
ReplyDeleteI was equally confused with the conflicting statements from Loria. Within the scientific paper the potential adverse health affects of rising temperatures (asthma, hypertension, heatstroke) are mentioned. Loria also explains that the level of deformation observed is sufficient to crack structural members and compromise foundations. Within the conclusion Loria's position shifts significantly to state that the safety of people and infrastructure are not at stake. I find your theory of outside influence as the source of Loria's inconsistency very feasible.
DeleteI agree with your comments, and think that the article did a good job of reflecting the intention of the paper. The Nature paper mentioned that the goal of the paper was to bridge a knowledge gap and address the lack of fundamental understanding of subsurface heat islands as a silent hazard for urban areas, with detrimental possibilities for the performance of civil infrastructure. The news article also mentioned that this paper was the first of its kind to discuss the impact of underground climate change on civil infrastructure. I think that both of these points were well approached, both in the scientific article as well as the news source. Also, the quotes included in the article were almost all from the author of the paper themselves, so it didn't feel like sensationalization to me. I also found the discussion of temperature and strain mentioned in the scientific article interesting, and would have found it nice if they touched on it a bit more in the article.
ReplyDeleteI agree that more details surrounding temperature and strain would have been welcomed in the news article. While Prisco did report the findings regarding heat pollution from infrastructure, the correlation the study found between air temperature and subsurface temperature goes unmentioned. I feel that if the news article was to report the magnitude of displacement, that data would have been helpful for the reader.
DeleteReading your response, article, and the paper I immediately thought of tundra regions where buildings have to be built on stilts/supports in order to prevent the warmth of the inhabitants and the home from melting the tundra and effectively destroying the building. I wonder if including this sort of situation in the article, either as a question in the beginning, or a sort of "comfort" at the end could help call attention to climate change at large without having to do a lot of extra "heavy lifting." Additionally, I agree that the inclusion of quotes in the article helps to limit the amount of miscommunications (also read "creative liberties") in the piece and can admire the article's brevity when it comes to the nitty-gritty of the generated models, but also crave a little more "sciencey" language when discussing this sort of model. Beyond this, I appreciate the article in that it does a really good job of explaining why this (could) matter and how we can work with or around this process to better adjust our behaviors in sustainable ways.
ReplyDeleteI think that your suggested comparison of stilt houses within tundra regions could have proven very helpful to the reader if included within the news article. I believe it is much easier for the reader to understand the impact that heat plays in compromising the frozen ground on which homes in the tundra lie. This comparison would help translate into understanding how the higher levels of heat pollution present in cities is capable of disturbing the ground lying beneath.
DeleteThis study involves the gradual warming of the ground beneath urban areas due to heat released by buildings and subterranean transportation systems. Researchers suggest applying thermal insulation to existing buildings, as well as deploying geothermal technologies to harness waste heat for heating and cooling. I am quite curious to know about in a world where underground climate change is becoming a growing concern for urban areas, what innovative technologies or strategies can be developed to monitor and mitigate its impact on infrastructure and the environment, while promoting more efficient use of underground heat energy?
ReplyDeleteLoria has other work into the field of harnessing underground heat energy that you may find intriguing. His paper, 'The thermal energy storage potential of underground tunnels used as heat exchangers', provides a strategy for utilizing the tunnels, walls, and slabs which are part of urban subsurface infrastructure as thermal batteries with the benefit of eliminating above ground land use required for alternative geothermal options.
DeleteI agree with your assessment of both the research article and the news article. I thought the author of the news article did a good job of not sensationalizing the study and actually taking direct quotes from the researchers to paint a more complete picture. However, a problem that I found with the study was how it simultaneously downplayed the impact of underground climate change on infrastructure and also stressed its potential hazards on the functionalities of said structures. Unfortunately, this issue also carried over to the CNN news article. I wish the author of the news report asked for more clarification from the original authors to more clearly illustrate just how big of a concern we should have. Finally, I am interested in where this area of study can go, as a researcher at the end of the news report said that other cities could be affected by such a phenomenon.
ReplyDeleteI found the conflicting statements from Loria within the scientific article confusing. As you suggested, I feel that if Prisco had requested clarification regarding Loria's evaluation of the threat at hand, significant insight would have been provided for the reader of the news article.
DeleteThe title certainly grabs your attention! In fact, by just reading the title I'm not at all surprised that such a phenomenon exists. It seems pretty intuitive that climate change would have an affect on the stability of the earth and thereby the structures that sit on it. We already know ground stability to be unpredictable and have seen an increasing number of sink holes throughout the years, we've been pumping out oil, water and now fracturing rock miles below the surface for years. We've also seen numerous examples of historical human error associated with building construction like the tower of Pisa and Salesforce tower slowly sinking in San Francisco. I didn't get a chance to dig into the details of the peer reviewed article, did they by chance mention any expected timeline or reference a simulation for a particular city? Interesting topic, thanks for sharing!
ReplyDeleteI like this news article because it is well structured and provides sufficient amount of necessary background knowledge. I am surprised to learn that this is not quite the same idea of global warming in the atmosphere, but it is indeed urban heat island. I would love to learn more about how scientists differentiate the two.
ReplyDeleteI do notice that the article did not go into depth about how deformation is influenced by clay types/soil layers and how it is modeled in relation with thermal power, depth, and time. Similar to what you stated, I actually do not think it is super necessary to cover these information because the article's focus is revealing the phenomenon of underground heating and optimistic views of its minimal impacts on human health and heat harvesting opportunities.