11:45 AM - 12:00 PM
[AAS11-16] Quantitative Analysis of Global Air Cleanliness Using the Clean aIr Index (CII)
Keywords:Global Air Cleanliness, Clean aIr Index (CII), Tropospheric Chemistry Reanalysis version 2, Quantitative Analysis
Air pollution poses significant risks to public health and the environment, and pollutants can travel across national boundaries, leading to transboundary pollution.
In this study, we evaluated global air cleanliness using the Clean aIr Index (CII), which integrates multiple air pollutants into a single metric by normalizing the concentrations of individual pollutants. A CII value of 1 indicates completely clean air (no air pollutants), and 0 indicates the presence of air pollutants that meet the numerical environmental criteria for the normalization. Here, we adopted the numerical standards specified by the World Health Organization's (WHO) Air Quality Guidelines (AQGs).
We employed the Tropospheric Chemistry Reanalysis version 2 (TCR-2), a global chemical transport model, to calculate surface concentrations of O3, PM2.5, NO2, CO, and SO2 from 2005 to 2021. We validated these data against ground-based measurements from the OpenAQ database, finding strong agreement (correlation coefficient = 0.64).
Results show a global average CII of 0.8048, with a statistically significant downward trend of -0.0033 per year (Seasonal Kendall Test). Notable differences emerged between oceanic and terrestrial regions: oceanic areas exhibited an average CII of 0.86 with a milder decline (-0.0010 year^-1), whereas terrestrial regions showed a lower average CII of 0.76 with a steeper rate of decrease (-0.0058 year^-1). On a continental scale, Asia had the lowest mean CII (0.47). India and Bangladesh experienced marked declines (-0.064 year^-1 and -0.051 year^-1, respectively), whereas China's CII rose by +0.064 year^-1, likely reflecting the impacts of stringent environmental policies. Europe and North America remained relatively stable, while Africa and South America showed decreases of -0.016 year^-1 and -0.00019 year^-1, respectively.
These findings underscore the importance of continuous air quality monitoring and effective policy measures. The CII offers a comprehensive framework for evaluating global air cleanliness and informs policymakers and researchers about the need for sustained, targeted interventions. Future studies should focus on evaluating the effects of specific policy interventions.
In this study, we evaluated global air cleanliness using the Clean aIr Index (CII), which integrates multiple air pollutants into a single metric by normalizing the concentrations of individual pollutants. A CII value of 1 indicates completely clean air (no air pollutants), and 0 indicates the presence of air pollutants that meet the numerical environmental criteria for the normalization. Here, we adopted the numerical standards specified by the World Health Organization's (WHO) Air Quality Guidelines (AQGs).
We employed the Tropospheric Chemistry Reanalysis version 2 (TCR-2), a global chemical transport model, to calculate surface concentrations of O3, PM2.5, NO2, CO, and SO2 from 2005 to 2021. We validated these data against ground-based measurements from the OpenAQ database, finding strong agreement (correlation coefficient = 0.64).
Results show a global average CII of 0.8048, with a statistically significant downward trend of -0.0033 per year (Seasonal Kendall Test). Notable differences emerged between oceanic and terrestrial regions: oceanic areas exhibited an average CII of 0.86 with a milder decline (-0.0010 year^-1), whereas terrestrial regions showed a lower average CII of 0.76 with a steeper rate of decrease (-0.0058 year^-1). On a continental scale, Asia had the lowest mean CII (0.47). India and Bangladesh experienced marked declines (-0.064 year^-1 and -0.051 year^-1, respectively), whereas China's CII rose by +0.064 year^-1, likely reflecting the impacts of stringent environmental policies. Europe and North America remained relatively stable, while Africa and South America showed decreases of -0.016 year^-1 and -0.00019 year^-1, respectively.
These findings underscore the importance of continuous air quality monitoring and effective policy measures. The CII offers a comprehensive framework for evaluating global air cleanliness and informs policymakers and researchers about the need for sustained, targeted interventions. Future studies should focus on evaluating the effects of specific policy interventions.