Many effects of a warming climate are well understood – increased temperatures, longer fire seasons, drought, rising sea level and intense storms. But drier conditions are also increasing the amount of dust blowing around the globe. In 2009, a dramatic “Red Dawn” dust storm overwhelmed Sydney in a 3000 kilometre-long plume. Almost 2.5 million tonnes of soil was deposited in the ocean – three times the monthly average – increasing iron levels and causing a spike in the growth of phytoplankton as far away as the Tasman Sea.
Dehydrated soil can be swept up into the air, transforming wind patterns and affecting ocean currents.
In the past, the major global sources of dust were the Sahara Desert, the Arabian Peninsula and some parts of South Asia. Now, a changing climate is expanding the arid lands that are a source of dust storms. A study released in February last year claimed that in Europe, Asia and the Mediterranean, dust storms were likely to become more intense as a result of climate change. As warmer temperatures lead to harsher droughts and the need to develop arid regions for farming and settlement, the necessary removal of vegetation dries out the soil.
Dehydrated soil can be swept up into the air, transforming wind patterns and affecting ocean currents, which can produce new sources of dust and new destinations for storms, with complex and unpredictable consequences. From the Himalayas to the Caucasus and the Rocky Mountains, the once-pristine white snowfields now feature streaks of red and brown. From 2005 to 2008, five times more dust blew onto the Rocky Mountains than during a similar period in the 1800s. As the darker, dust-speckled snow absorbs more sun, it melts 30 to 60 days faster. The result is that plants grow for a longer season and consume more water, transpiring it back into the atmosphere instead of it flowing into rivers and streams.
An increase in the amount of allergens, pathogens and pollution transported in dust is posing a major risk to global health. Dust storms can carry sand, silt, bacteria, fungi, aerosols and particle pollution over long distances. Dust particles frequently transport PM10 and PM2.5 particles – with a diameter less than 10 μm or 2.5 μm – which cause many types of respiratory and cardiovascular diseases. The UN Convention to Combat Desertification has linked outbreaks of Valley Fever in the United States and meningitis in Africa to dust storms. In 2000, there were 2,757 reported cases of Valley Fever. By 2019, that number had risen to 18,407. In China and Japan, a childhood vascular condition called Kawasaki disease that can cause irreparable cardiac damage is believed to be spread by spores of the Candida fungus, which blows in with dust from the farmlands of China. A link between wind-blown dust and poor respiratory health among Indigenous children in Western Australia has been established by research at the University of Tasmania.
In the United States, 41 per cent of the worst dust days are produced from sources in Asia.
There is a geopolitical dimension to this problem. Plumes and storms of dust transgress national boundaries, making domestic attempts to contain them ineffective. Around the world, 151 countries experience dust storms, but only 45 of these countries actually generate dust themselves. In Asia, dust from the Gobi and Taklimakan Deserts affects air quality in Central and Eastern Asian countries such as Korea and Japan. In the United States, 41 per cent of the worst dust days are produced from sources in Asia. In early March this year, an intense storm originating in the Mongolian desert lifted dust plumes high into the air and deposited them as far away as China and South Korea. The storm killed nine people, grounded flights and closed schools. It led to an explosion in particulate matter pollution in China’s major cities, including a sharp spike in PM10 and PM2.5 levels, which were up to 8 times World Health Organisation acceptable levels.
Fairly straightforward action, such as vegetation regeneration in source areas, can reduce the amount of dust that ends up airborne. In China, reforestation has reduced dust storm frequency. However, as the destructive storm in March makes clear, the initiative of one country alone cannot prevent the effects altogether. Better communication and notification of storms between countries would help vulnerable people prepare. More research is needed to understand the complex interplay and peculiar dynamics of dust, ocean and weather patterns. And the global cooperation mechanisms in place to combat carbon emissions must be expanded into a program of action to prevent some of the changing climate’s more unexpected consequences.