Dust storms and global warming
Dust storms are significant meteorological events characterized by reduced visibility due to the presence of fine particles in the air, primarily originating from arid and semi-arid regions. These storms are influenced by various wind conditions, particularly associated with frontal systems and high pressure gradients. Dust particles can travel vast distances; for example, plumes from the Sahara Desert can reach southern Europe and even cross the Atlantic to the Caribbean. The interaction between dust emissions and global warming is complex, as dust can influence climate by altering atmospheric properties and contributing nutrients to ecosystems, particularly in oceans.
However, increased dust activity may also contribute to adverse health effects, such as respiratory issues, and be linked to changes in rainfall patterns and intensifying drought conditions. The frequency and intensity of dust storms are expected to rise due to climate change, which exacerbates desertification processes. While some studies predict an increase in dust emissions linked to rising wind speeds, other models suggest potential reductions due to increased rainfall and vegetation cover. The United Nations has recognized the growing concern over dust storms, designating July 12 as the International Day of Combating Sand and Dust Storms to raise awareness and encourage action against the challenges posed by these natural phenomena.
Subject Terms
Dust storms and global warming
Definition
Dust storms are meteorological events in which visibility is reduced to 1 kilometer or less as a result of blowing dust (defined as material less than 63 microns in size—the size of silt and clay). In many areas, wind conditions conducive to dust storms are associated with the passage of frontal systems (especially cold fronts) and downdrafts from convectional storms. Elsewhere, strengthened pressure gradients give rise to sustained high wind speeds capable of raising dust. Examples include the Shamal and Hundred Days winds in the Arabian Gulf and Seistan regions of Iran and Afghanistan and the Santa Ana winds of Southern California.
The dust emission process involves both the horizontal transport of coarse, sand-sized material and the vertical of fine, silt- or clay-sized particles. Coarse particles abrade fine materials (as, for example, on the surfaces of dry lake beds) and eject the fine particles into the air, where atmospheric turbulence transports them in suspension, often for many tens or hundreds of kilometers. Plumes of dust from the Sahara Desert regularly reach southern Europe, and they occasionally cross the Atlantic Ocean to reach the Caribbean Sea and South America. Dust plumes from China reach Japan on a regular basis and occasionally cross the Pacific Ocean to North America.
Significance for Climate Change
Dust emitted and transported from deserts represents a major linkage between deserts and other environments. Dust deposition has important effects on ocean and terrestrial productivity by contributing nutrients to ecosystems (especially iron, which is limiting to marine productivity). Air quality is affected by particulate loading. Atmospheric radiative properties are changed through the scattering and absorption of solar radiation by mineral aerosols. Such processes may result in either warming or cooling effects, depending on the size and composition of the dust particles. Dust is trapped by vegetation and adds to soils on desert margins and elsewhere. Saharan dust is a major component of soils throughout the Mediterranean Basin and even as far afield as the Caribbean. Human health is affected by high dust concentrations, which can lead to respiratory disease. Changes in the dust loading of the atmosphere have also been linked to rainfall changes in areas adjacent to the Sahara and to the intensification of drought conditions.
Most dust source areas are located in zones and are associated with topographic lows, flat surfaces, finely textured soils, and sparse or no vegetation cover. Such areas have been identified by orbital sensors, particularly the Total Ozone Mapping Spectrometer Aerosol Index (TOMS AI), as well as ground observations. The majority of mineral dust is derived from natural surfaces; the contribution of human activities (such as agriculture) to the dust loading of the atmosphere is uncertain; global estimates vary from anywhere between 50 percent to less than 10 percent. Major dust source areas include the Bodelé Depression in Tchad, the Aral Sea area, southeast Iran, the Taklamakan Desert of China, Inner Mongolia, and the loess plateau of China. The Sahara region is believed to be the largest single dust source, accounting for as much as 690 million metric tons of dust per year. Satellite data show that three of the world’s most important dust source areas lie in this region.
The interannual frequency and magnitude of dust storms is strongly linked to climatic variability; in many areas, dust emissions are inversely correlated to rainfall, although in a complex nonlinear manner, in part because a supply of fine sediment is required for dust emission. For example, periods of increased rainfall cause runoff that may flood playas and contribute sediment that is mobilized by wind in subsequent dry periods. In this way, dust emissions appear to correlate with El Niño-Southern Oscillation (ENSO) cycles in the southwestern United States. Elsewhere, there are strong anticorrelations between the flux of dust from the Sahara and rainfall. A 2021 study of a deadly dust storm in Mongolia and northern China confirmed that, since climate change helps drive desertification, dust storms of increasing intensity and frequency could result from continued global warming, with major consequences for human health.
On a longer time scale, important millennial and centennial variations in global and regional dust loadings are recorded by dust deposits in marine sediments and ice cores. For example, dust flux from the Sahara and many other desert regions (such as Australia) was high during the Last Glacial Maximum, as a result of increased aridity and wind strength at this time. Dust flux also increased sharply following the desiccation of the Sahara some five thousand years ago.
Future changes in dust emissions are therefore likely to be influenced by climate change, most notably as the effect of vegetation-cover change, with human activities affecting conditions locally. The direction of change in dust emissions, as predicted by different models, is, however, uncertain. In one model, Saharan dust emissions are predicted to increase by 11 percent as a result of higher wind speeds. Other simulations predict a decrease of 4 percent as a result of increased monsoonal rainfall and vegetation cover.
In 2023, the United Nations designated July 12 as the first International Day of Combating Sand and Dust Storms. The organization hoped that the designated day would help raise international awareness of the threats posed by the expected increase in dust storms as global climate change advances. Additionally, the United Nations hoped that such awareness might spur new international efforts to aid communities affected by desertification and dust storms.
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