A third major sandstorm in five weeks has turned Beijing’s skies yellow and the sun blue. The storms—actually dust storms made up of much finer particles than sand—sent concentrations of airborne particulates (minute particles of matter floating in air) soaring to dangerous levels. Residents of China's capital city used goggles, masks and hairnets to protect themselves from the choking sand and dust. The Beijing city government ordered schools to cancel outside sport and advised the public to stay inside where possible.
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​​​​​​​21st April 2021

The storms were caused by winds from Mongolia and the northwestern Chinese region of Inner Mongolia. Recent warmer-than-average temperatures and droughts created larger areas of bare earth in the dry grasslands, from which dust was whipped up into the air by strong winds and blown eastwards at high speed. The amount of sand and dust in the air in mid-April was less than that of the two earlier sandstorms that hit northern China in March, but the wind speed was higher, enabling the dust to travel faster and farther.
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During the latest sandstorm, recorded levels of PM₁₀ particles—those measuring 10 micrometres or less, called "coarse particulate matter" (which can penetrate the deepest part of the lungs)—rose to 999 micrograms per cubic metre. This almost doubled the “hazardous” stage on the Beijing air quality index, set at a maximum level of 500. The World Health Organization (WHO) recommends that levels of PM₁₀ do not exceed 20 micrograms per cubic metre in a 24 hour period.
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Beijing regularly experiences sandstorms in March and April, partially because of the proximity of the Gobi Desert. They have worsened since the 1950s, due to widespread deforestation, overgrazing and soil erosion in Mongolia and Inner Mongolia. Millions of trees have already been planted in a vast belt of land stretching about 4800 kilometres across northern China in an effort to trap the dust. This is part of a project known as the Great Green Wall, similar to the project of the same name in Africa. Also known as the Three-North Shelterbelt Program, it was begun in 1978, and is planned to be completed around 2050.

As climate change intensifies, the environmental conditions that lead to the formation of sandstorms—warmer temperatures and drought—will probably become increasingly frequent, raising the likelihood of more frequent and intense sandstorms.
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