By Yuang Wang — The Mark News —
In the last 30 years, with a quasi-exponential growth in industrialization, population, and urbanization, many Asian countries have experienced deteriorating air quality and a dramatic increase in anthropogenic emissions of aerosol in the atmosphere. Enormous manufacturing, industrial, and power plants, as well as automobiles, have produced huge amounts of air pollutants.
China, for instance, has experienced severe air pollution, with aerosols or fine particulate matter smaller than 2.5 micrometers (PM2.5) reaching unprecedented high levels across many cities in recent winters. Measurements in Beijing showed that levels of PM2.5 were about 350 to 500 μg/m3, which are more than 10 times higher than the 25 μg/m3 that the World Health Organization considers safe.
In January 2014, China experienced record levels of pollution several times, even exceeding the maximum that the U.S. Embassy’s equipment can measure. Because of the ever-growing air pollution in China, in the last three decades, the nationwide number of deaths from lung cancer has risen by about 465 percent.
Man-made aerosols are also linked to the modification of weather and climate. Our previous studies have shown that air pollution in China can reduce the surface temperature by scattering or absorbing the solar radiation aloft, and can suppress light precipitation and enhance extreme heavy rain by modulating cloud systems. Air pollution is also found to increase the frequency of lightning associated with thunderstorms.
While these results indicate that man-made aerosols strongly contribute to extreme weather near the emission source, a more critical question is about the far-reaching effects of Asian pollution.
Under the influence of the wintertime monsoon flow from Asia to the Pacific Ocean, huge amounts of man-made aerosols from Asia, mainly composed of sulfate and black carbon, can be lifted a few miles high and transported downwind to the northern Pacific Ocean and even North America.
Using global climate models and observational data, our recent study suggests that Asian pollutants can significantly affect cloud formations, precipitation, and the intensity of storms over the northern Pacific Ocean. These findings explain the increase in wintertime convective clouds that researchers have observed in this region (using satellite measurements) since the 1990s.
Since the mid-latitude storm is critical to the global general circulation that transports heat and moisture from low latitudes to the polar regions, we can expect that the storms modulated by Asian pollution will affect the weather in the Northern Hemisphere. Inter-governmental agencies should use the quantitative predictions of the far-reaching effects of Asian pollution when developing strategies to mitigate the regional and global impacts of anthropogenic pollutants.
Yuan Wang is currently a researcher in the Jet Propulsion Lab at the National Aeronautics and Space Administration (NASA).