The China Mail - UN says dust levels in air dropped slightly in 2023

The UN's weather and climate agency called for greater vigilance in the face of climate change, as drier surface soil leads to more dust being carried in the wind.

"Every year, around 2,000 million tons of dust enters the atmosphere, darkening skies and harming air quality in regions that can be thousands of kilometres away, and affecting economies, ecosystems, weather and climate," the World Meteorological Organization (WMO) said in a statement.

The global average surface dust concentration in 2023 was 12.7 microgrammes per cubic metre of air -- slightly lower than the 2022 figure of 13.8, but still above the long-term average.

Last year's slight dip was due to reduced dust emissions from regions including North Africa, the Arabian Peninsula, the Iranian Plateau, northern India, central Australia and northwestern China, the WMO said.

However, average concentrations were higher in western Central Asia, northern and central China and southern Mongolia.

The most severe dust storm of the year swept across Mongolia in March 2023, affecting more than four million square kilometres (1.5 million square miles), including several provinces in China, the WMO said in its annual Airborne Dust Bulletin.

The storm posed "considerable" health challenges due to a "dramatic decline in air quality", it said.

"It reduced visibility to less than 500 metres in parts of Beijing and led to significant disruptions in transportation and daily life, highlighting the need for effective warning systems."

Across the whole year, the highest mean surface dust concentration was located in Chad, estimated at 800 to 1,100 microgrammes per cubic metre.

- Human impact -

Dust can be transported vast distances by the wind. Though mainly a natural phenomenon, human activity is also driving dust storms.

"We need to be vigilant in the face of continuing environmental degradation and current and future climate change," WMO chief Celeste Saulo warned in the statement.

"Combined with poor land management, this is conducive to more sand and dust storms."

With changed atmospheric conditions acting like a driver, "the intensity is growing, and the frequency" of storms, Sara Basart, the WMO's sand and dust scientific officer, told journalists in Geneva.

The reduction of ice cover in places like Scandinavia and Iceland was leading to newly-exposed land there becoming new sources of sand and dust storms, she said.

The WMO said there were some positives to dust being transported over the oceans.

It cited a new study which concluded that Saharan dust deposits in the Atlantic ultimately benefit skipjack tuna by providing iron and phosphorus that boost the growth of phytoplankton.

The new organic matter transfers up the food chain, from small fish to large predators, "favouring the whole marine ecosystem", the report said.

The agency also said monitoring and forecasting accuracy had improved in recent years, notably through a system first established in 2007.

July 12 marks the first International Day of Combating Sand and Dust Storms, which aims to raise awareness of the growing health and environmental challenges they pose.

R.Yeung--ThChM