... and the dust drought causes.

. . . and the dust drought causes

The large-scale winds that help to bring drought to Africa also take some of Africa away. Soil dust is swept from the parched land and is carried across the Atlantic to places such as Barbados, where Joseph M. Prospero and his co-workers have been monitoring the dust concentrations since 1965 (SN: 12/15/84, p. 376). In the April 24 NATURE, Prospero and Ruby T. Nees of the University of Miami (Fla.) present their most recent data to support the idea that this dust is a sensitive indicator of short-term meteorologic and climate change.

The researchers have noted in general a strong correlation between unusually high dust levels and periods of severe drought. For example, during the summers of 1983 and 1984, at a peak in the drought that began in the late 1960s, dust concentrations reached the highest levels on record, measuring four times that of predrought years. Prospero and Nees say the best correlations are between dust levels and rainfall averaged over the previous two to three years--an indication that soils became more vulnerable to erosion as drought conditions are prolonged. They also note that rainfall must not be the only factor influencing dust levels, since there are some years of normal rainfall and high dust concentrations.

Scientists continue to debate the specific causes of variations in dust levels. But what is clear from satellite imagery and other data is that dust outbreaks in West Africa have been particularly intense during the last few years. ". . . [T]o our knowledge,' write the researchers, "the rate of transport of dust out of North Africa is unprecedented in recent times.' Some studies have suggested that dust clouds block sunlight to a degree comparable to that envisioned for a "nuclear winter.' Dust outbreaks in Africa and elsewhere, which are caused by changes in climate, are thought in turn to affect climate--perhaps, as some have suggested, perpetuating the droughts that caused them.