A decline in sun-dimming airborne dust has caused a fast warming of the tropical North Atlantic in recent decades, according to a study that might help predict hurricanes on the other side of the ocean. About 70 percent of the warming of the Atlantic since the early 1980s was caused by less dust, blown from Saharan sandstorms or caused by volcanic eruptions, U.S.-based scientists wrote in the journal Science. In the past, the rapid temperature rise had been blamed on factors such as global warming or shifts in ocean currents.