Particles in the atmosphere play an indispensable role in climate regulation by influencing key processes such as cloud formation and the planet’s radiation balance. In urban environments, research has predominantly concentrated on primary particles—those directly emitted from sources like vehicle exhaust, industrial activities, and construction. However, a growing body of evidence suggests that the formation of new particles through atmospheric reactions—known as secondary particles—has been largely overlooked in the context of their climatic impact, particularly in densely populated urban areas.
A recent study published in One Earth has challenged the conventional wisdom regarding urban particulate matter and its role in climate regulation. The study uncovers significant evidence suggesting that the climatic effects of newly-formed particles in urban areas have been substantially underestimated, calling for a more comprehensive approach to understanding atmospheric processes in these environments.
A Call for Long-Term Vertical Observations
“To accurately assess the climate effects of particles, we need comprehensive long-term vertical observations,” says Markku Kulmala, an academician at the Institute for Atmospheric and Earth System Research (INAR) at the University of Helsinki. This statement underscores the complexity of atmospheric processes and the need for data that captures particle behavior at various heights above ground level.
Traditionally, climate research in urban areas has relied on measurements taken at ground level, offering insights into particle dynamics near the Earth’s surface. However, the atmosphere is a dynamic and layered system, with atmospheric processes varying significantly at different altitudes. By neglecting data from higher altitudes, previous studies have missed critical information regarding how particles behave in urban environments, especially when considering the formation of new particles in elevated layers of the atmosphere.
New Insights from Elevated Measurements
In a groundbreaking new study, researchers employed a 325-meter meteorological tower in Beijing, one of the world’s largest and most polluted urban centers, to gather data on particle formation at various heights. This innovative measurement approach has yielded fresh insights into particle dynamics in urban environments. The findings reveal that particle formation is notably more intense at higher altitudes, with conditions such as increased concentrations of sulfuric acid and higher relative humidity playing pivotal roles in promoting the growth of particles.
This discovery has profound implications for understanding urban aerosols. In contrast to rural environments, where particle formation is primarily driven by ground-level processes, urban areas feature complex atmospheric dynamics—such as varied pollution sources, traffic emissions, and building-induced turbulence—that contribute to particle growth at altitudes above street level.
Wei Du, one of the key researchers involved in the study, emphasized the significance of these findings, saying, “The enhanced particle formation aloft suggests that while ground-level measurements provide valuable insights, they may not capture the full picture of particle dynamics, particularly in densely populated urban areas.” This critical insight highlights the necessity of examining the atmosphere above the urban landscape to gain a more holistic understanding of urban aerosol behavior and its climatic effects.
Enhanced Particle Growth and Cloud Formation
One of the primary ways that particles influence the climate is by acting as cloud condensation nuclei (CCN), tiny particles that serve as the foundation for cloud droplets to form. Clouds are essential for regulating the Earth’s temperature, as they reflect sunlight and help to redistribute heat and moisture across the planet. The formation of new particles, often derived from human-made emissions, plays a crucial role in the process of cloud formation and, in turn, climate regulation.
The study suggests that when gaseous precursors from anthropogenic emissions are transported into higher layers of the atmosphere, they contribute to the formation and growth of particles, which then act as CCN. These particles are instrumental in cloud development, which can affect local and regional climates.
In light of these findings, the researchers argue that the contribution of new particles to the total population of CCN has been underestimated by approximately 20%. This suggests that the role of newly-formed particles in regulating cloud properties and local climate is far more significant than previously thought. As clouds can both cool the Earth’s surface by reflecting sunlight and warm it by trapping heat, understanding the full extent of particle formation is crucial for accurately predicting the climate effects of urban pollution.
Implications for Urban Planning and Policy
The study’s conclusions have important implications for both urban planning and policy-making. As urban centers around the world continue to grapple with the challenges of air pollution, climate change, and public health, understanding how particles behave at different altitudes in the atmosphere is essential for developing effective strategies to mitigate the impact of urban emissions on the climate.
Wei Du notes, “As cities continue to grapple with air pollution and climate challenges, understanding the vertical profiles of atmospheric processes can help develop more effective strategies to mitigate their impacts on both climate and public health.” This knowledge is vital for creating targeted interventions to reduce emissions, improve air quality, and better manage the urban environment.
The findings underscore the importance of moving beyond traditional ground-level measurements to a more comprehensive approach that includes vertical profiles of the atmosphere. This could involve developing new monitoring platforms that can capture data at different heights or incorporating existing tools like tall towers, balloons, and drones to monitor particles in urban areas at various altitudes.
The Collaborative Effort
The study represents a collaborative effort between researchers from the University of Helsinki, the Chinese Academy of Sciences, and various international partners. Their work builds on previous research in atmospheric science but introduces new methodologies that enhance the understanding of particle formation in urban environments.
According to Yele Sun, Professor at the Chinese Academy of Sciences, “The Beijing 325 m Meteorological Tower is a unique research platform for atmospheric and climate science in megacities. We are pleased to collaborate with international partners to address climate change together.” The collaboration between institutions in both Finland and China underscores the global nature of atmospheric research and the collective effort required to tackle pressing climate issues.
A New Era of Atmospheric Research
This study is part of a broader push to better understand the complexities of urban atmospheric dynamics and their implications for climate regulation. With the growing recognition of the importance of new particle formation in urban areas, future research will likely expand on these findings, exploring the precise mechanisms behind particle growth, their interaction with urban pollutants, and their influence on cloud formation and climate feedback loops.
In addition to scientific advancements, the study’s findings contribute to broader policy discussions surrounding climate change and air quality. As cities worldwide continue to grow and develop, policymakers will need to consider new research on atmospheric processes to inform decisions on urban sustainability, emissions reduction, and climate mitigation.
By adopting enhanced measurement techniques and incorporating vertical observations, researchers and policymakers alike can develop more effective strategies to combat air pollution, reduce greenhouse gas emissions, and safeguard public health—ultimately working toward a healthier, more sustainable urban future.
Conclusion
The climate effects of new particles in urban environments have long been underappreciated in scientific research, leading to significant gaps in our understanding of their role in climate regulation. The recent study from Beijing, which highlights the importance of vertical observations in urban areas, challenges conventional thinking and provides new insights into particle formation and its contribution to cloud formation and climate control.
As cities continue to face growing challenges related to air pollution and climate change, this research offers valuable guidance for the development of more effective climate mitigation strategies. By examining particles at various altitudes and incorporating comprehensive atmospheric profiles, we can gain a clearer understanding of how urban pollution affects climate patterns and take steps to protect the environment and public health for future generations.
Reference: Wei Du et al, Impacts of enhanced new-particle growth events above urban roughness sublayer on cloud condensation nuclei, One Earth (2024). DOI: 10.1016/j.oneear.2024.12.005