For decades, scientists believed that the ocean’s ability to cool the planet was largely due to dimethyl sulfide (DMS)—a sulfur compound released by marine life that helps form reflective clouds. But a new study published in Science Advances reveals a surprising player in this process: methanethiol (MeSH). This lesser-known gas, long dismissed as a minor contributor, turns out to have a major cooling effect on the Earth’s climate. The discovery could help explain long-standing errors in climate models, particularly over the Southern Ocean, where projections have consistently overestimated solar radiation levels.
The ocean plays a critical role in regulating the Earth’s temperature. Tiny marine organisms release sulfur compounds into the air, which then interact with the atmosphere to form clouds that reflect sunlight, cooling the planet. Until now, scientists focused on DMS. However, this study reveals that MeSH, its chemical cousin, has been quietly amplifying DMS’s cooling effects all along—and at a much greater scale than previously believed.
By compiling the first global database of oceanic MeSH concentrations, researchers found that this gas contributes 30–70% more to the cooling effect of marine sulfur emissions than previously accounted for. This impact is especially strong over the Southern Ocean, where MeSH levels are higher in colder waters as compared to warmer, more biologically productive regions. Additionally, MeSH doesn’t just add its own cooling influence—it actually enhances DMS’s effect, extending its atmospheric lifespan and increasing its ability to reflect sunlight. These new findings suggest that marine sulfur emissions have been underestimated by at least 25% globally, requiring updates to current climate models.
To uncover MeSH’s true role, scientists collected data from multiple oceanic research expeditions spanning from the tropical Atlantic to the icy waters of Antarctica. Using advanced atmospheric modeling, they incorporated MeSH concentrations into climate simulations and found a significant increase in cooling potential, particularly during the Southern Hemisphere summer when marine life is most active. By comparing these new simulations to existing climate models, researchers confirmed that MeSH plays a crucial role in regulating Earth’s temperature.
Current climate models have struggled to accurately simulate cloud formation over the Southern Ocean, leading to an overestimation of the region’s warming potential. “Climate models have greatly overestimated the solar radiation actually reaching the Southern Ocean, largely because they are not capable of correctly simulating clouds,” explains Dr. Charel Wohl, lead author of the study. Incorporating MeSH into climate projections could significantly improve temperature predictions and help policymakers create more accurate strategies for combating global warming.
Furthermore, as human sulfur emissions decline due to stricter air quality regulations, natural sources of sulfur—like MeSH—will become increasingly important in shaping future climate patterns.
Co-lead author Dr. Julián Villamayor adds, “It may not seem like much, but methanethiol is more efficient at oxidizing and forming aerosols than dimethyl sulfide, and, therefore, its climate impact is magnified.”
The next step for researchers is to refine global climate models by integrating MeSH’s full influence on atmospheric chemistry. Future studies will also investigate how changes in ocean temperature and marine life activity could affect MeSH production. As scientists work to close the gaps in climate modeling, this discovery highlights the hidden yet powerful role of oceanic sulfur gases in shaping Earth’s climate.
This study sheds light on one of the ocean’s best-kept climate secrets—a naturally occurring gas that has been quietly cooling our planet for centuries. By factoring MeSH into climate predictions, scientists can improve global models and develop more effective climate policies. As we race to mitigate climate change, understanding the ocean’s hidden role in the fight against global warming is more crucial than ever.
For more details, read the full study in Science Advances.
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