Researchers have, for the first time, measured the global emissions of a sulfur gas produced by marine organisms, uncovering that it cools the climate more significantly than previously recognized, particularly over the Southern Ocean. This new study highlights how oceans not only absorb and redistribute solar heat but also emit gases that create particles with immediate climate impact, such as enhancing the brightness of clouds which in turn reflect solar heat.
The findings, published in the journal Science Advances, indicate that oceans play a dual role in climate regulation: they capture solar heat and generate gases that influence climate directly by affecting cloud behavior.
This research expands the understanding of marine sulfur’s climatic effects by introducing a previously overlooked compound known as methanethiol. Until recently, detecting this gas was challenging, and past studies concentrated on warmer ocean areas, not realizing that polar regions are actually hotspots for these emissions.
A team of scientists from the Institute of Marine Sciences (ICM-CSIC) and the Blas Cabrera Institute of Physical Chemistry (IQF-CSIC) in Spain led this research, with Dr. Charel Wohl, who previously worked at ICM-CSIC and is currently at the University of East Anglia (UEA) in the UK, as one of the contributors.
Their results signify a significant step forward in a major theory introduced 40 years ago regarding the ocean’s role in regulating Earth’s climate.
This theory proposed that tiny plankton in the ocean’s surface produce sulfur as a gas called dimethyl sulfide, which, when released into the atmosphere, oxidizes and creates small particles known as aerosols.
Aerosols can reflect part of the sun’s radiation back into space, thereby reducing the heat retained by the Earth. Their cooling effect is amplified when they participate in cloud formation, providing a counteracting influence similar in magnitude to that of well-known warming greenhouse gases such as carbon dioxide and methane.
The researchers argue that this study enhances the understanding of climate regulation by introducing this previously undetected element and underscores the vital role of sulfur aerosols. They emphasize the significant impact of human activities on climate change and warn that without intervention, global temperatures will continue to rise.
According to Dr. Wohl from UEA’s Centre for Ocean and Atmospheric Sciences, “This represents the climatic component with the highest cooling potential, yet it remains poorly understood. While we suspected that methanethiol was being released from the ocean, we were unaware of its quantity and global distribution, nor did we recognize its substantial climate impact.”
“Climate models have often overestimated the amount of solar radiation reaching the Southern Ocean because they struggle to accurately simulate cloud behavior. Our study helps bridge the gap between model predictions and observational data.”
With this discovery, scientists can better calibrate climate models used in forecasting temperature increases of +1.5 ºC or +2 ºC, which will significantly inform policy development.
“Previously, it was thought that oceans emitted sulfur primarily in the form of dimethyl sulfide, responsible for the characteristic odor of shells,” noted Dr. Martà Galà from ICM-CSIC and another lead author of the study.
Dr. Wohl added, “Thanks to advancements in measurement technologies, we now know that plankton also produce methanethiol, and we have developed a method to quantify this emission on a global scale, including when and where it occurs.”
“Understanding the emissions of this compound will refine our ability to depict cloud behavior over the Southern Ocean and more accurately evaluate their cooling effects.”
The research team compiled all existing measurements of methanethiol in seawater, augmented those they collected in the Southern Ocean and along the Mediterranean coast, and statistically correlated them with seawater temperatures gathered from satellites.
This analysis led them to conclude that, on a global average per annum, methanethiol increases known marine sulfur emissions by 25%.
Although this number may seem modest, methanethiol is more effective at oxidizing and forming aerosols compared to dimethyl sulfide. Consequently, its impact on climate is enhanced,” explained Dr. Julián Villamayor, a co-lead author and researcher at IQF-CSIC.
The team also incorporated marine emissions of methanethiol into a cutting-edge climate model to evaluate their influence on the planet’s energy balance.
The results indicated that the effects are significantly more pronounced in the Southern Hemisphere, where larger ocean areas and lesser human activity result in lower levels of sulfur emissions from fossil fuel combustion.
This research received support from various organizations, including the European Research Council and the Spanish Ministry of Science and Innovation.
