Orange sepia-style skies, snow-capped peaks turning yellow… In recent hours, France has been offering images of unusual landscapes that are spreading on social networks. They are the most spectacular manifestation of a still unknown phenomenon: the passage over the country of a cloud of sand dust from the Sahara.
“This phenomenon is quite usual in winter, but this time it was particularly remarkable and noticed”, comments Vincent Guidard, head of the “atmospheric pollution” team at the National Meteorological Research Center. Global warming could further increase the frequency and intensity of these phenomena, according to Barcelona’s Atmospheric Dust Prediction Center, which monitors with supercomputers the occurrence of sand and dust storms in North Africa, the Middle East and Europe.
Research has also shown that sand particles could act as a formidable Trojan horse and be themselves contaminated with potentially dangerous chemical compounds such as heavy metals, pesticides or transport pollen, bacteria and viruses. A strong wind on the surface will lift sand dust in the desert; the captured particles will then rise to tropospheric altitudes (between 3,000 and 4,000 meters), finally, the mass flows of air directed from south to north will carry them for thousands of kilometers, and then, the particles will settle. The higher they go, the further they will be transported. In last week’s episode, dust from the Sahara traveled to England and southern Scandinavia.
According to estimates by the World Meteorological Organization, between 1 billion and 3 billion tonnes of dust are released into the atmosphere worldwide each year. A large part—between 500 million and 1 billion tonnes—comes from the Sahara. But these sandstorms can also find their source in the Salton Sea (California), Patagonia (Argentina, Chile), the Altiplano (Andes cordillera), the Lake Eyre basin (Australia), the Namib desert ( Southern Africa), the Indus Valley (Pakistan, India), the Gobi Desert (Mongolia, China) or the Taklamakan Desert (in Xinjiang, China). The share of dust emitted in Asia has been steadily increasing for twenty years, due to climate change and increasing desertification.
Learn more by Stéphane Mandard, in French, here