Sahara dust helps remove greenhouse gas methane from atmosphere: research

The Sahara dust that sometimes leaves a thin layer of sand over the Netherlands actually plays a big role against climate change, a team of international scientists, including Jan-Berend Stuut of the Netherlands Institute for Sea Research (NIOZ), found. The dust helps absorb methane from the atmosphere. Methane is a greenhouse gas that causes 30 times as much warming as CO2.

Researchers already knew that Sahara dust plays many vital roles in our planet’s climate, Stuut said on the NIOZ site. “In high regions of the atmosphere, it controls the amount of sunlight reaching the earth’s surface. And it can trap heat in the lower part of the atmosphere. The dust is also fertilizing phytoplankton in the oceans. Plankton captures CO2 from the atmosphere.”

But the dust’s link with methane absorption is newly discovered. It was already known that more methane was absorbed in the Caribbean in the summer and autumn. “But there was no explanation for this,” Stuut said. That is until Maarten van Herpen, the first author of the study and working at Acacia Impact Innovation, and Stuut noticed that the higher absorption coincided with the times that a lot of Sahara dust was blown toward the West. The link was quickly confirmed.

Blowing mineral dust mixes with sea spray to form “Minderal Dust-Sea Spray Aerosol” (MDSA), the researchers concluded. Their results suggest that sunlight activates MDSA to produce an abundance of chlorine atoms, which oxidize atmospheric methane and tropospheric ozone.

“Under the influence of sunlight, the iron from desert dust forms chlorine radicals from sea salt. These ions bind to the greenhouse gas methane, thereby removing it from the atmosphere,” Stuut explained.

How the MDSA mechanism works in other parts of the world requires further research, the scientists said. Follow-up research is underway. “Our current research is focused on getting a better understanding of what exactly influences how much methane MDSA particles are removing from the atmosphere,” Van Herpen said.

For this research, the scientists asked seafarers to fill flasks with air as they crossed through the African dust cloud. “We have collected 500 flasks so far,” Van Herpen said. They’re analyzing the flasks along with samples from across the North Atlantic, provided by atmospheric observatories. “Early results are looking very encouraging, but we need a full year of data before we can draw conclusions.”