GENEVA: An exceptionally rare haze of Saharan dust cloaked Switzerland and southeastern France on Saturday, sparking health warnings as a yellow hue tinged the sky.

The phenomenon, which began in Switzerland on Friday, brings with it “a very clear worsening of sunlight and visibility. Added to that is an increase in concentrations of fine particles”, the MeteoSuisse weather service posted on X.

With the dust concentrated at lower than 3,000 metres (around 9,800 feet), air quality was especially affected, with Switzerland’s airCHeck monitoring application flagging high levels of pollution in a corridor stretching from the southwest to the northeast.

Calculations estimate that the amount of dust reached around 180,000 tonnes, double the levels recorded during recent similar events, SRF Meteo forecaster Roman Brogli told public radio.

Skies turn yellow, prompting health warnings

In neighbouring France, local authorities in the southeast and south announced that the air pollution threshold was breached on Saturday, with the Herault department asking residents to avoid intense physical effort, particularly those with heart or respiratory problems.

The Sahara desert releases 60 to 200 million tonnes of mineral dust per year. While the largest particles come rapidly back down to earth, the smallest can travel thousands of kilometres.

The sand gives an orange tint to snow and can impact melting processes, notably for glaciers, which are shrinking as average temperatures rise, by reducing the ice’s ability to reflect sunlight. The situation is due to improve in France and Switzerland on Sunday.

According to SWI website, the surge in dust was propelled by a robust southerly current, ferrying particles from the Sahara desert in northern Africa to Swiss skies as early as Friday.

The Sahara stands as the planet’s primary source of mineral dust, emitting between 60 to 200 million tonnes annually. While larger particles precipitate swiftly, smaller ones embark on journeys spanning thousands of kilometres, traversing entire continents, including Europe. These Saharan dust events significantly contribute to aerosol pollution, particularly in the transitional seasons of spring and autumn.

The presence of Saharan dust alters atmospheric dynamics, manifesting in a yellowish hue across the skies and enhancing the spectacle of sunrises and sunsets.

Moreover, when settling upon snow, it can impede outdoor activities like skiing.

While the influx of Saharan dust captures attention, its health implications remain minimal for the majority.

Published in Dawn, March 31st, 2024