Oceans release more sulfur and cool the climate more than expected.

Researchers have, for the first time, measured global emissions of a sulfur gas from marine life, showing it cools the climate more than previously believed, particularly over the Southern Ocean.

A study published in Science Advances reveals that oceans not only absorb and redistribute solar heat but also emit gases that create particles with immediate climatic effects, such as brightening clouds to reflect heat.

The research expands the known climatic impact of marine sulfur by identifying methanethiol, a previously undetected compound. This gas had been difficult to measure until recently, with earlier studies focusing on warmer regions instead of the polar oceans, now identified as key emission hotspots.

Scientists from Spain’s Institute of Marine Sciences (ICM-CSIC) and the Blas Cabrera Institute of Physical Chemistry (IQF-CSIC), led by Dr. Charel Wohl—formerly of ICM-CSIC and now at the University of East Anglia (UEA) in the UK—conducted the study.

Plankton, Sulfur Emissions, and Climate Cooling

Their findings build on a 40-year-old theory about the ocean’s role in climate regulation. They show that microscopic plankton at the ocean’s surface produce sulfur gas, specifically dimethyl sulfide, which oxidizes in the atmosphere to form aerosols. These aerosols reflect solar radiation back into space and cool the planet. Their cooling effect increases when they contribute to cloud formation, counteracting the warming impact of greenhouse gases like carbon dioxide and methane.

The study highlights the overlooked role of sulfur aerosols in regulating the climate and the ongoing impact of human activities on global warming. Dr. Charel Wohl of UEA noted that methanethiol, a potent but poorly understood cooling agent, had remained unquantified until now.

“Climate models have overestimated solar radiation in the Southern Ocean due to cloud simulation errors. This research narrows the gap between models and observations,” Wohl explained.

Advancing Climate Models and Policy Insights

The findings improve climate models used for predicting 1.5°C or 2°C warming, aiding policy-making. Co-author Dr. Martí Galí added that oceans were previously thought to emit sulfur only as dimethyl sulfide, a plankton byproduct responsible for shellfish odors.

Dr. Wohl explained, “Advances in measurement techniques now allow us to identify plankton emissions of methanethiol and quantify when, where, and how much of this gas is released globally. This knowledge helps us better model clouds over the Southern Ocean and more accurately estimate their cooling effect.”

The researchers compiled all existing methanethiol measurements, supplemented them with new data from the Southern Ocean and Mediterranean coast, and correlated them with satellite-derived seawater temperatures.

Their analysis revealed that methanethiol increases known marine sulfur emissions by 25% annually on a global scale.

“Although the increase might seem small, methanethiol oxidizes and forms aerosols more efficiently than dimethyl sulfide, amplifying its climatic impact,” noted co-lead Dr. Julián Villamayor of IQF-CSIC.

The team integrated these marine methanethiol emissions into a cutting-edge climate model to evaluate their effects on Earth’s radiation balance. The findings show that the impacts are most pronounced in the Southern Hemisphere, where extensive ocean areas and lower fossil fuel emissions make sulfur’s natural cooling role more evident.

Read the original article on: Phys Org

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