The study quantifies for the first time the global emission of methanethiol, a sulfur gas produced by marine life, and its contribution to the formation of airborne particles and clouds with cooling effects on the climate.
Almost 40 years ago, one of the most ground-breaking hypotheses about the role of the ocean in regulating the Earth's climate was put forward. The hypothesis proposed that microscopic plankton living on the surface of the seas produce sulphur in the form of a gas which, once in the atmosphere, is oxidised and forms tiny particles called aerosols. Aerosols reflect part of the solar radiation back into space and therefore reduce the heat retained by the Earth, with an effect opposite to that of the well-known greenhouse gases. The cooling effect of aerosols is amplified because these particles are essential for the condensation of water droplets and the formation of optically thick clouds. Clouds are the climatic element with the greatest cooling capacity.
The new discovery expands the climate impact of marine sulphur, because it adds a compound that had gone unnoticed. The impacts are much more visible in the southern hemisphere, where there are fewer continents and less human activity, and the presence of sulphur from the burning of fossil fuels is lower.
The inclusion of methanethiol in the climate model increases the formation of sulfur aerosols over the Southern Ocean by 30% to 70%, reducing incident solar radiation in summer by an amount between 0.3 and 1.5 W/m2. Current climate models greatly overestimate the solar radiation that actually reaches the Southern Ocean, mainly because they are not able to correctly simulate clouds. Incorporating this new sulfur emission will allow us to bring the model closer to reality.
Wohl, C., J. Villamayor, M. Galí, A.S. Mahajan, R.P. Fernández, C.A. Cuevas, A. Bossolasco, Q. Li, A.J. Kettle, T. Williams, R. Sarda-Estève, V. Gros, R. Simó and A. Saiz-Lopez. Marine emissions of methanethiol increase aerosol cooling in the Southern Ocean. Science Advances. DOI: 10.1126/sciadv.adq2465
https://www.science.org/doi/10.1126/sciadv.adq2465