Oceans emit sulfur and cool the climate more than previously thought

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Southern Ocean surrounds Antarctica [image credit: theozonehole.com]

A big reality check for climate models. “Climate models have greatly overestimated the solar radiation actually reaching the Southern Ocean, largely because they are not capable of correctly simulating clouds”, says a researcher. By brightening clouds, aerosols there have a cooling effect ‘opposite of—but of the same magnitude as—that of well-known warming greenhouse gases such as carbon dioxide or methane’. What’s left of their supposed greenhouse effect, in this region at least?
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For the first time, researchers have quantified the global emissions of a sulfur gas produced by marine life, revealing that it cools the climate more than previously thought, especially over the Southern Ocean,
says Phys.org.

The study, published in the journal Science Advances, shows that the oceans not only capture and redistribute the sun’s heat, but produce gases that make particles with immediate climatic effects; for example, through the brightening of clouds that reflect this heat.

This broadens the climatic impact of marine sulfur because it adds a new compound, methanethiol, that had previously gone unnoticed.

Researchers only detected the gas recently, because it had previously been notoriously hard to measure. Earlier work had focused on warmer oceans, whereas the polar oceans are the emission hotspots.

The researchers argue that this new work improves our understanding of how the climate of the planet is regulated by adding a previously overlooked component, and that the work illustrates the crucial importance of sulfur aerosols.

They also highlight the magnitude of the impact of human activity on the climate and that the planet will continue to warm if no action is taken. [Talkshop comment – standard waffle].

Dr. Wohl, of UEA’s Centre for Ocean and Atmospheric Sciences and one of the lead authors, said, “This is the climatic element with the greatest cooling capacity, but also the least understood. We knew methanethiol was coming out of the ocean, but we had no idea about how much and where. We also did not know it had such an impact on climate.

“Climate models have greatly overestimated the solar radiation actually reaching the Southern Ocean, largely because they are not capable of correctly simulating clouds. The work done here partially closes the longstanding knowledge gap between models and observations.”

The research was led by a team of scientists from the Institute of Marine Sciences (ICM-CSIC) and the Blas Cabrera Institute of Physical Chemistry (IQF-CSIC) in Spain. They included Dr. Charel Wohl, previously at ICM-CSIC and now at the University of East Anglia (UEA) in the UK.

Their findings represent a major advance on one of the most groundbreaking theories proposed 40 years ago about the role of the ocean in regulating Earth’s climate.

This suggests that microscopic plankton living on the surface of the seas produce sulfur in the form of a gas, dimethyl sulfide, that—once in the atmosphere—oxidizes and forms small particles called aerosols.

Aerosols reflect part of the solar radiation back into space and therefore reduce the heat retained by the Earth. Their cooling effect is magnified when they become involved in making clouds, with an effect opposite of—but of the same magnitude as—that of well-known warming greenhouse gases such as carbon dioxide or methane.

Full article here.
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Image: Southern Ocean surrounds Antarctica [credit: theozonehole.com]

Source: https://tallbloke.wordpress.com/2024/11/28/oceans-emit-sulfur-and-cool-the-climate-more-than-previously-thought/