Aerosols emitted from ships shown to overestimate the cooling effect of clouds
By Tiantian Zhu
News article can be found here. Research article published on Science can be found here.
I was interested in learning about ship emissions because seeing major ports in the US and China, including Los Angeles, Hong Kong, and Tianjin, always made me wonder how those massive numbers of ships influenced our environment and climate. The article Ship exhaust studies overestimate cooling from pollution-altered clouds by Carolyn Gramling portrays how scientists investigate and argue if ship tracks would serve as a reliable example to study the aerosol-cloud-climate interactions. Ship tracks contain exhaust particles that act as nuclei of cloud droplets, which has been thought to brighten the clouds and enhance the cooling effect by reflecting more sunlight. However, the peer-reviewed article by Glassmeier et al. reveals a more complex story of the aerosols from ships and an overestimation of their cooling effect by up to 200%.
Gramling walks the readers through the physical processes of aerosols seeding clouds and changing clouds’ properties. It seems like they had an interview with Dr. Franziska Glassmeier, the scientist who led the study. Gramling borrows Glassmeier’s plain language to highlight the research approach of comparing ship track clouds and polluted urban clouds in order to show the difference in their response to aerosols over time. Because the ship tracks are short-lived, the cooling effects cease once the natural clouds return to the pre-pollution state. In contrast, the industrial pollution, for example in cities, has tinier aerosol-seeded droplets that accelerate cloud evaporation, continuously allowing more solar radiation through (Fig. 2).
The journal article by Glassmeier et al. unpacks the overestimation of cooling effect with much greater details and computations. The relationship between Liquid Water Path (LWP)—which is the vertically integrated amount of liquid water—and amount of cloud droplets (N) is used to derive LWP adjustment, a measure to characterize clouds and their cooling effect. Glassmeier et al. focuses on the nonprecipitating stratocumulus (Sc) clouds as they are by far the largest contributor to the clouds’ cooling effect on the planet. These clouds are expected to have negative LWP adjustments. This means with higher aerosol concentrations LWP decreases, and the clouds get thinner and darker, and thus have a warming effect.
They used climatological satellite studies, also explained briefly in the news article, to derive LWP adjustments over time. As LWP adjustment is a function of LWP vs. N, the slopes of this linear function exhibit that the initial state is followed by the steady-state condition, where LWP adjustment gets more negative overtime. This indicates that as more aerosols are emitted, the warming effect exacerbates over time. The measurements from short-lived ship tracks thus would not show the “ultimate” greater warming effect, because the clouds quickly return to the original state before the full evolution towards the steady state (as shown by Fig. 2). As Glassmeier et al. put it, the characteristic adjustment equilibrium time (which is, evolution towards steady state) exceeds the typical evolution time at sampling, τadj >> Δtship.
Therefore, ship-track studies are concluded as less suitable for representing cloud cooling/warming than the climatological satellite studies (which predominantly sample from LWPs close to steady state) are. I think neither the news nor the journal articles show extreme opinions that ship track data should be ruled out. They both carefully examine the values and drawbacks of ship track data: it is a direct and concrete example of aerosols’ impacts on clouds, while it fails to feature temporal and spatial continuity of pollution. I appreciate that the news article well conveys the nuances of this study’s conclusion. More importantly, the readers can better understand that science is ever-evolving, with no definite answers or the “best” ways to arrive at certain conclusions. In particular, as a person enthusiastic about the atmosphere, I think Gramling does a good job on describing how complex it is and how ambiguous its processes still appear to us.
I would give this news article a 9/10, mainly because of how well-paced and thought-provoking the storytelling is. I took one point off because I noticed a few jargons to be substituted or better clarified. For example, it would help to define aerosols up front before diving into the topic. “Simulations”, as mentioned in the paragraphs about research methods, might also be an abstract concept to the public. As the article describes the response of clouds in different conditions, a graphic illustration, such as Fig. 2 from the journal article, could clearly show the processes step by step.
I also found the article did a great job of condensing down the information from the paper into an easy-to-understand format.
ReplyDeleteIn regards to the paper, I found it interesting that the ability of clouds to respond to aerosols has been studied so much that a mathematical formula could be made from the data. Based on the fact that these aerosols are there because pollution on land doesn't move around, the formula stays relatively accurate. However, how would the formula change if we drastically reduced our pollution? Would these atmospheric clouds now behave more like those near ship smokestacks?
Hi Marla, I agree that one mathematical formula derived from the data seems a little simplifying given the varying factors of pollution types, concentration, and spatial and temporal characteristics! I think this is where atmospheric chemistry models are useful, which are built using a large number of formula like this.
DeleteI found the article "Ship exhaust studies overestimate cooling from pollution-altered clouds" very informative, largely comprehensive, while also exactly sharing the information from the paper. Considering the fact that this article was published in Science News it is likely that it would be a more convoluted paper. Yet I found that even so it didn't really simplify all of the concepts much which would make it difficult for a non-scientific person to digest.
ReplyDeleteI agree that neither the news article or the paper really made any final decisions on whether this data from ship routes should be fully ruled out or not. Since the pollution on these routes aren't really a great long-term model, they don't quite apply like the climatological satellite studies do.
I also agree that the news article did a great job explaining the paper's conclusions. I just don't believe they simplified anything so the article wasn't too concise.
I think its interesting it was previously assumed that ship track data would be sufficient to determine cloud liquid-water adjustments due to pollution. Ship track emissions are much more periodic compared to those in urban areas. I think this was a really important study and that the new article was one of the more well-written articles in terms of portraying the scientific findings.
ReplyDeleteThank you for sharing this great article with us which highlights the study of the complexity of how aerosols and clouds interact in the context of climate change, raising important questions about our understanding of their cooling effects. Ship tracks, which are bright lines of clouds formed by the exhaust particles from cargo ships, have been used as a real-world example to study this interaction. While these ship tracks initially create brighter clouds that reflect sunlight and have a cooling effect, the study reveals that they may not provide a complete picture of the impact of pollution on clouds. Unlike ship tracks, industrial pollution introduces aerosols steadily over time, affecting cloud behavior differently. This raises questions about the long-term consequences of industrial pollution on cloud formation and its implications for climate change. Such as how might these findings influence climate models and our ability to predict the Earth's future climate? What are the broader implications for our understanding of the relationship between aerosols, clouds, and global temperatures? How can we refine our interpretation of satellite data to better account for the gradual effects of pollution on clouds?
ReplyDeleteHi Bishvanwesha, thanks for mentioning how this study is relevant to climate models and scientists' ability to predict Earth's future! I believe the final section of the journal article does a great job of examining/breaking down different techniques of measurement and analysis for aerosol-cloud-climate interactions. It's also the part I like the most about this scientific journal article.
DeleteI agree with your rating of the article. It was easy to follow and very interesting. I haven't really considered the cooling affect of aerosols in clouds before, especially in the context of emissions from ships that are always moving. I wonder if there are other types of emissions that would show a similar pattern.
ReplyDeleteThe research you shares is very interesting and important in regards to predicting the cooling and warming of the world. It is always very fascinating when new minds are applied to an older concept and show the holes and how the predictions they have been making are incorrect. The article does a great job of scientifically summarizing the key findings and importance of the paper, but I agree with you on how it is a bit too wordy for a general audience. Her writing style and the publisher as a whole seems very science focused, so I assume that is why they do not feel the need to clarify on many of the words, since their audience is less general and more those who are interested in science.
ReplyDeleteYes it seems like they are writing to a more scientifically-focused audience rather than general public. The author also has a PhD in geosciences (or some adjacent field?), which implies why their writing style seems a little jargon-heavy. However, I don't think it's too bad to be able to follow, as they tried to use the plain language and dialogues!
DeleteThis study just goes to show the importance of questioning established results and/or accepted modes of thought within science, because what's going on could be just the opposite! I appreciate Glassmeier's daring to challenge the convention as well as the narrowed focus of the study, because although the ship track data is a particular example of aerosol's impact on cloud formation and warming mechanisms, these results could inform thinking about how aerosols from other sources could act in a similar way.
ReplyDeleteIt seems like this journal article, despite using the satellite data that can track ship emissions more continuously than ship track data, is still investigating ship emissions on a shorter time scale. I would be interested to learn more about how ship emissions impact aerosol levels in the long term, especially when considering different wind patterns that occur over water instead of land, as well as how it affects large scale ports like you mentioned in the beginning of your blog post.
ReplyDeleteI also find the news article to do a great job of disecting the science. I really enjoyed the article because of it gets you thinking! I would love to know more about what this means in terms of port city air pollution versus landlocked city air pollution. I feel like the cooling effect is interesting, and something that is not well known, but I feel like the ideas presented from this research can be taken in so many new ways like pollution effects. If i were to do further reserach, this news article could be a great starting point to gather ideas.
ReplyDeleteI found the angle of both the paper and the news article super interesting! The article was a great way to understand the more complex content covered in the research paper. I didn't realize that the brightness of the cloud was related to the particulate contained within it. Researchers in the past have used ship tracks to study the impact of aerosols in clouds, but this article explained why this isn't necessarily the most accurate way to study impacts on climate warming and cooling. I found the article appropriate for the intended audience, as it was published on Science News- someone that was seeking out information about aerosol-cloud interactions would likely be able to grasp the concepts covered in the article. As someone else mentioned, it's definitely important to question established results as new, more accurate methods of quantification and characterization emerge.
ReplyDeleteHi Tiantian! Great review of the article. I thought the article did a great job of breaking down the science and jargon from the paper. I read somewhere about how decreasing sulfate particles released from shipping vessels was part of the cause for increased ocean temperatures this summer. This was proposed to be due to the cloud seeding effect discussed in this article. I think it would be interesting to compare the results from this article to different sources regarding the seed effect of these particles. Regardless, I found the article to be a good representation of the paper's findings. It did a nice job of summarizing the main points in the paper in a easily digestible way.
ReplyDeleteGreat article! Ship emissions is not something I have ever considered when thinking about sources of gas/aerosol emissions, so I really enjoyed learning about it through reading these articles and listening to your presentation. When you were presenting, we had a brief discussion about what the chemicals could be that are actually being emitted from ships. Professor Ault mentioned that SO2, I believe, was the major emission coming from these ships. After this discussion, I started thinking about how this could link to possible detrimental effects on marine life. Acid rain occurs when gases like SO2 and NOx combine with water in the atmosphere to form acids like nitric acid and sulfuric acid (which we learned about later in class). My thought on this is, could having increased SO2 above the ocean lead to more acid rain events over the ocean, resulting in negative effects on marine ecosystems? It would be interesting to see a follow up article on this.
ReplyDeleteI really find this article interesting! Even though we discuss aerosols and their many sources, I have never before considered ship emissions. What's even more interesting to me is that it's not 100% clear as to whether ships have an overall warming or overall cooling effect thanks to those competing mechanisms. I'm both interested and excited to see future expansions on this work to find out the overall effect ship emissions have. Perhaps Professor Pratt and the team could do some sampling to determine the content of ship emissions on the way to their next field study! :-) I'd be really curious to know what's in them and what sorts of effects that could have on the local environment.
ReplyDeleteHi Tiantian, great commentary on this articles! I found your fourth paragraph very clarifying, as I wasn't originally able to understand the implication of LWP on how ship track data differed from the satellite studies on all sources (natural and anthropogenic). As was mentioned above, I'd love to know more about the specific chemicals coming from the ships besides SO2, and I'm curious to see how we could measure air quality/human health impacts when these emissions interact with other pollutants from things such as forest fires and natural gas wells. The atmospheric chemistry field in general seems like it has a lot of opportunity to do field studies and explorations across the planet in the future!
ReplyDeleteHi Tiantian, I really like your analysis of this news article. I think you were right in saying that it does well to present the nuance of scientific research, which is not often done in mainstream media. It's a difficult balancing act of being true to the science while also making the article palatable to the general public, in which I think this article did well.
ReplyDelete