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Saharan dust is bad for health. But it’s also crucial to Earth’s biology and climate
The Saharan dust plume is a supersized version of ones that cross the Atlantic all the time, ferrying particles that irritate lungs but also fertilize plant and ocean life.
The massive dust cloud arrived in Puerto Rico the Sunday before last, sweeping in and staining the evening sky a milky white. Monday and Tuesday, the air grew heavier with dust by the hour. Late on Tuesday, Olga Mayol-Bracero, an atmospheric chemist at the University of Puerto Rico, Rio Piedras, checked the readings at the atmospheric observation station she runs on the northeastern tip of the island. The numbers were higher than anything she’d seen in the 16 years she’s been taking measurements at the station.
“I couldn’t see the sky or clouds, just a grayish layer,” she says. “Definitely, we have never seen something like this.”
The dust over Puerto Rico represented the leading edge of a giant plume that
