Aerosols: Health vs Climate Change
When talking about air pollution, one often hears the word “aerosol” come up in conversation. These are extremely small solid particles or liquid droplets emitted from either natural or anthropogenic sources, and comprise the particulate matter (PM) concentration measured while investigating air pollution [1].
Ship tracks are a common example of anthropogenic aerosols in the atmosphere. (Source: https://earthobservatory.nasa.gov/images/37455/ship-tracks-south-of-alaska)
Moreover, I find aerosols particularly interesting while discussing air pollution owing to how they also play a complex role in temperature changes associated with climate change. Accordingly, greater amounts of reflective aerosols present in the atmosphere tend to increase the earth’s albedo [2]. The albedo refers to the reflectivity of the earth’s surface to incoming solar radiation. In other words, higher amounts of aerosols allow for more sunlight to be reflected, therefore possibly having a cooling effect on earth’s temperature2. Although black carbon aerosols (such as soot) absorb solar radiation and warm the atmosphere, the majority of aerosols are associated with cooling effects on the planet [3]. However, aerosols also contribute to various health problems when inhaled, such as reduced life expectancy owing to cardiovascular and respiratory diseases [4]. Evidently, aerosols are complex substances, influencing both planetary and human health in drastically different ways.
Moreover, a peculiar dilemma appears to arise: would the process of clearing up air pollution (thereby reducing the amount of aerosols present in the atmosphere) lead to an inevitable increase in global temperatures? Additionally, should developing countries prioritise the health of their population and remove aerosols, or let them remain in the atmosphere to curb global increases in temperature associated with climate change?
Unfortunately, there appears to be no clear answer. Scientists urge caution, as there is significant uncertainty regarding aerosol-radiation interactions in the first place [5]. Recent studies also showcase that perhaps the once lauded cooling effect of aerosols may be weaker than initially thought [6]. Therefore, there remains a knowledge gap which must be closed through rigorous modelling and research into aerosol science and natural cloud variability before enacting policies to balance between human health and climate change mitigation.
References
[1] Buseck, P. R., & Schwartz, S. E. (2014). Tropospheric Aerosols. Treatise on Geochemistry, 95–137. https://doi.org/10.1016/b978-0-08-095975-7.00404-6
[2] Twomey, S. (1977). The influence of pollution on the shortwave albedo of clouds. Journal of the Atmospheric Sciences, 34(7), 1149–1152. https://doi.org/10.1175/1520-0469(1977)034<1149:tiopot>2.0.co;2
[3] NASA. (2020). Just 5 questions: Aerosols. Climate Change: Vital Signs of the Planet. https://climate.nasa.gov/news/215/just-5-questions-aerosols/#:~:text=It%20turns%20out%20that%20most
[4] Shiraiwa, M., Ueda, K., Pozzer, A., Lammel, G., Kampf, C. J., Fushimi, A., Enami, S., Arangio, A. M., Fröhlich-Nowoisky, J., Fujitani, Y., Furuyama, A., Lakey, P. S., Lelieveld, J., Lucas, K., Morino, Y., Pöschl, U., Takahama, S., Takami, A., Tong, H., … Sato, K. (2017). Aerosol health effects from molecular to Global Scales. Environmental Science & Technology, 51(23), 13545–13567. https://doi.org/10.1021/acs.est.7b04417
[5] Haywood, J. (2021). Atmospheric aerosols and their role in climate change. In Climate change (pp. 645-659). Elsevier.
[6] Glassmeier, F., Hoffmann, F., Johnson, J. S., Yamaguchi, T., Carslaw, K. S., & Feingold, G. (2021). Aerosol-cloud-climate cooling overestimated by ship-track data. Science, 371(6528), 485–489. https://doi.org/10.1126/science.abd3980