Climate effects of particles in urban air have been underestimated

Urban environments are complex ecosystems where pollution, weather patterns, and human activities constantly interact. Among the many factors shaping urban climates, airborne particles play a crucial role in influencing cloud formation and radiation balance.

These particles affect how sunlight is absorbed or reflected, how clouds develop, and even how precipitation forms.

Traditionally, scientific research has focused on primary particles – those emitted directly from vehicle exhaust, industrial processes, and other sources. However, new particles formed through atmospheric reactions have received far less attention.

Impact on climate regulation

Despite their invisible presence, these secondary particles significantly impact climate regulation. Recent findings suggest that scientists may have underestimated their role in urban climate systems.

A study published in the journal One Earth provides strong evidence that new particles in urban areas influence atmospheric processes in ways that were previously overlooked. This new understanding could reshape approaches to air quality management and climate mitigation strategies.

“To accurately assess the climate effects of particles, we need comprehensive long-term vertical observations,” noted Academician Markku Kulmala from the Institute for Atmospheric and Earth System Research (INAR) at the University of Helsinki.

Why urban particles matter for climate

Urban air pollution is a well-documented problem, but most studies have primarily focused on what happens at ground level.

The formation of new particles occurs in the atmosphere itself, driven by chemical reactions between pollutants and natural compounds. These newly formed particles can grow in size and eventually influence cloud development, which in turn affects local and regional climates.

Cities produce a variety of gaseous emissions that act as precursors for particle formation. When these gases mix with atmospheric compounds, they create new particles that rise and spread through different layers of the atmosphere.

The extent to which these particles impact climate has remained uncertain due to the difficulty of measuring them at various altitudes.

Recognizing this gap, researchers have turned to advanced monitoring methods to capture the full picture of urban particle behavior. By shifting the focus from ground-based observations to a more comprehensive vertical analysis, they have uncovered new insights into how particle formation varies at different heights.

Role of altitude in particle formation

The researchers conducted their study using a 325-meter meteorological tower in Beijing, one of the tallest atmospheric research platforms in the world.

This tower allowed the team to measure particle formation at multiple heights, providing a clearer understanding of how these processes differ at various atmospheric levels.

The findings revealed that particle formation is far more pronounced at higher altitudes than previously assumed. Factors such as increased sulfuric acid concentration and higher relative humidity contribute to particle growth in the upper layers of the urban atmosphere.

This suggests that air pollution dynamics in cities are far more layered and complex than traditional ground-level measurements have shown.

Full picture of urban particle dynamics

“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,” said study lead author Wei Du.

By analyzing particles at different heights, researchers discovered that elevated regions of the atmosphere serve as active zones for new particle formation.

These findings suggest that policymakers and scientists must consider vertical air movement when assessing air pollution and climate impacts.

Urban particles and cloud formation

Clouds play a crucial role in regulating Earth’s climate by reflecting sunlight and distributing moisture.

The process of cloud formation depends on cloud condensation nuclei (CCN), which provide surfaces for water vapor to condense into droplets. Many of these nuclei originate from newly formed particles in the atmosphere.

When gaseous emissions rise and interact with chemicals at higher altitudes, they contribute to the growth of these tiny particles. As they increase in size, they become more effective at attracting water vapor and forming clouds.

The study found that the impact of new particles on CCN has been underestimated by around 20%, highlighting the need for more accurate climate models that include vertical particle behavior.

The ability of these particles to influence cloud formation means they also affect temperature regulation and precipitation patterns. This has wide-ranging implications for urban climates, which are already experiencing shifts due to increasing pollution and global climate change.

Implications for urban climate policy

The study’s findings go beyond scientific discovery and have important real-world applications. Cities around the world are grappling with air pollution and climate-related challenges, making it essential to develop policies that address the full complexity of atmospheric processes.

By understanding how new particles behave at different altitudes, urban planners and policymakers can create more effective strategies to manage pollution and mitigate climate impacts.

“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,” noted Wei Du.

A collaborative approach

This study represents a collaborative effort between leading institutions, including the University of Helsinki and the Chinese Academy of Sciences.

Scientists from multiple disciplines contributed to the research, highlighting the importance of international cooperation in addressing climate challenges.

“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,” said Yele Sun, professor at the Chinese Academy of Sciences.

Expanding climate research

By expanding the scope of climate research to include vertical measurements, scientists are gaining a more complete understanding of how urban atmospheric particles behave and influence climate.

These insights can shape future climate policies, helping cities adapt to environmental changes while improving air quality for millions of people.

As research continues, long-term monitoring will be key to refining climate models and identifying more effective solutions for pollution control.

This study marks an important step in that direction, emphasizing the need to look beyond ground-level observations and consider the full atmospheric picture.

The study is published in the journal One Earth.

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