Its rotten egg smell saves lives! Methanethiol, better known as methyl mercaptan, is added to natural gas to give it an odor detectable by the human nose even at very low concentrations, and thus prevent dangers linked to gas leaks (INRS). This substance is also found in living organisms, in terrestrial but also marine environments.
However, the oceans not only capture and redistribute the sun's heat, but they also produce gases forming particles (aerosols) with immediate climatic effects, for example by brightening the clouds which reflect the heat.
Among these cooling gases is methanethiol. In the oceans, researchers have only recently detected this substance, as it is difficult to measure in the field – particularly in polar regions. The new study, published November 27 in the journal Science Advances, is the first to quantify the oceanic origin of these emissions.
In Svalbard, Greenpeace travels back in time
In line with a revolutionary theory
These results represent a “major breakthrough” compared to one of the most revolutionary theories proposed 40 years ago on the role of the ocean in regulating the Earth's climate, according to a press release from the University of East Anglia in England, where now works Dr Charel Wohl, co-author of the study.
This theory suggested that microscopic plankton living on sea surfaces produced sulfur in the form of a gas, dimethyl sulfide, which, once in the atmosphere, oxidized and formed small particles called aerosols.
Aerosols reflect part of the solar radiation back into space and thus reduce the heat retained by the Earth. We speak of a “radiative balance”. This cooling effect is amplified when these particles participate in the formation of clouds – with an opposite effect, but of the same magnitude, as that of greenhouse gases known for their warming effect, such as carbon dioxide.
-The authors of the study brought together all the available measurements of methanethiol in seawater, to which they added those they had carried out in the Southern Ocean and on the Mediterranean coast. Then, they put these measurements in a statistical relationship with sea water temperature obtained from satellites.
Thus, Spanish and British researchers were able to conclude that, annually and on a global average, methanethiol increased known marine sulfur emissions by 25%.
“It may not seem like much, but methanethiol is more effective at oxidizing and forming aerosols than dimethyl sulfide and, therefore, its impact on climate is amplified”underlines in the press release Dr Julián Villamayor, researcher at the Blas Cabrera Institute of Physical Chemistry (IQF-CSIC), in Spain, co-director of the study.
The ocean alone cannot solve our problems…
The team also integrated marine methanethiol emissions into a state-of-the-art climate model in order to assess their effect on the planet's radiation balance: the impact is even more notable in the southern hemisphere.
This result can be explained by the greater proportion of ocean surface compared to land surface in this region, as well as by a lesser presence of sulfur from fossil fuels, due to more limited human activity.
According to the researchers, this new work improves our understanding of the regulation of the planet's climate by “illustrating the crucial importance of sulfur aerosols”. The authors also point out the extent of the impact of human activity on the climate: “the planet will continue to warm if no action is taken”they warn.
