Abstract
Abstract. During the last 30 years, significant effort has been made to improve air quality through legislation for emissions reduction. Global three-dimensional chemistry-transport simulations of atmospheric composition over the past 3 decades have been performed to estimate what the air quality levels would have been under a scenario of stagnation of anthropogenic emissions per capita as in 1980, accounting for the population increase (BA1980) or using the standard practice of neglecting it (AE1980), and how they compare to the historical changes in air quality levels. The simulations are based on assimilated meteorology to account for the year-to-year observed climate variability and on different scenarios of anthropogenic emissions of pollutants. The ACCMIP historical emissions dataset is used as the starting point. Our sensitivity simulations provide clear indications that air quality legislation and technology developments have limited the rapid increase of air pollutants. The achieved reductions in concentrations of nitrogen oxides, carbon monoxide, black carbon, and sulfate aerosols are found to be significant when comparing to both BA1980 and AE1980 simulations that neglect any measures applied for the protection of the environment. We also show the potentially large tropospheric air quality benefit from the development of cleaner technology used by the growing global population. These 30-year hindcast sensitivity simulations demonstrate that the actual benefit in air quality due to air pollution legislation and technological advances is higher than the gain calculated by a simple comparison against a constant anthropogenic emissions simulation, as is usually done. Our results also indicate that over China and India the beneficial technological advances for the air quality may have been masked by the explosive increase in local population and the disproportional increase in energy demand partially due to the globalization of the economy.
Highlights
The rapid increase in Earth’s population that took place the last 60 years and the changes in human practices towards a society with larger energy consumption resulted in intensifying the atmospheric pollutant emission (Lamarque et al, 2013; Hand et al, 2012; Wang et al, 2014; Steffen et al, 2007)
The present study indicates that the gain in air quality is larger than what is deduced by comparing current legislation (CL) to Anthropogenic Emissions 1980 (AE1980) (Table S3a), as is usually done, since comparisons of the CL and BA1980 simulations reveal a higher gain in air quality
The ACCMIP historical anthropogenic emissions that account for applied air quality legislation, technology development, as well as geographic shift in human economic activities have been the CL simulation
Summary
The rapid increase in Earth’s population that took place the last 60 years and the changes in human practices towards a society with larger energy consumption resulted in intensifying the atmospheric pollutant emission (Lamarque et al, 2013; Hand et al, 2012; Wang et al, 2014; Steffen et al, 2007). Oltmans et al (2013) performed an extended analysis on long-term (20–40 years) time series of global surface and ozonesonde observations They found that the substantial tropospheric ozone increases observed in the early 1990s, the flattening, or even the decrease in ozone levels observed at several locations (e.g., Glacier National Park, Minamitorishima) during the past 10 years are the result of the restrictions on precursor emissions. Air quality assessments are performed by comparing the pollutants concentrations at present with those of a past year (Lin et al, 2014); in order to evaluate the effectiveness of the applied air quality legislation, we need to account for the changes induced by meteorology and the increase in anthropogenic emissions due to increases in population and energy demand. The base simulation, current legislation (CL), is performed using historical anthropogenic emissions for the period 1980– 2010 that integrate the changes in industrial and technological developments, the standard of living, and the population growth, with air pollution abatement efforts
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