The research highlights the role of methanethiol, a sulfur gas recently identified as a key contributor to cooling through its impact on cloud formation. Methanethiol emissions were previously overlooked due to difficulties in detection and a focus on warmer ocean regions, whereas this study emphasizes polar ocean hotspots.
Led by scientists from Spain's Institute of Marine Sciences (ICM-CSIC) and the Blas Cabrera Institute of Physical Chemistry (IQF-CSIC), in collaboration with the University of East Anglia (UEA), the research enhances understanding of how sulfur aerosols influence the planet's temperature.
The study builds on a theory proposed 40 years ago that marine plankton produce dimethyl sulphide, a gas that oxidizes in the atmosphere to form aerosols, which then reflect solar radiation and cool the Earth. Methanethiol, however, appears to amplify this cooling effect.
"This is the climatic element with the greatest cooling capacity, but also the least understood," said Dr. Charel Wohl, a lead author and researcher at UEA. "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."
The findings show that methanethiol emissions account for a 25% increase in known sulfur contributions from the oceans. This effect is magnified because methanethiol oxidizes more efficiently than dimethyl sulphide, creating more aerosols that aid in cloud formation.
"Knowing the emissions of this compound will help us to more accurately represent clouds over the Southern Ocean and calculate more realistically their cooling effect," added Dr. Wohl.
The research team combined global methanethiol measurements with new data collected in the Southern Ocean and Mediterranean coast. By linking emissions to seawater temperature data from satellites, they quantified annual global methanethiol emissions and incorporated these figures into advanced climate models.
The results underscore the heightened effects of sulfur emissions in the Southern Hemisphere, where the relative lack of fossil fuel-derived sulfur enhances the visibility of marine sulfur's impact. The findings promise to improve the accuracy of climate models, crucial for forecasting scenarios like 1.5C or 2C warming.
"This discovery refines our understanding of sulfur aerosols and their role in climate regulation," said Dr. Marti Gali, an ICM-CSIC researcher and study co-author.
The research was supported by the European Research Council and the Spanish Ministry of Science and Innovation.
'Marine emissions of methanethiol increase aerosol cooling in the Southern Ocean,' Charel Wohl, Julian Villamayor, and Marti Gali et al., was published in Science Advances on November 27.
Research Report:Marine emissions of methanethiol increase aerosol cooling in the Southern Ocean
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