Ah, the wonders of modern climate science. For decades, we have been convinced that climate models are fine-tuned predictive tools that can tell us what our planet will look like a hundred years from now. But every now and then, like a plot twist in a mediocre detective novel, we discover a new, “game-changing” variable. Methyl mercaptan (MeSH) has become a new favorite for aerosol cooling over the Southern Ocean.
According to a recent publication in scientific progressMeSH – a sulfur compound previously overlooked for its reactivity – is now considered a key factor in climate cooling.
This finding suggests that MeSH emissions from marine biological activity increase the sulfate aerosol burden in the Southern Ocean by 70%. These aerosols scatter sunlight and cool the atmosphere, reducing radiative biases in climate patterns in the region. Oh, this is no small adjustment. We're talking about a 28% increase in the direct radiative effect of aerosols over a large area. Oops, missed decades.
abstract
Ocean emissions of dimethyl sulfide (DMS) are a major source of aerosols contributing to climate cooling. However, most marine biological sulfur cycles occur not through DMS, but through methyl mercaptan (MeSH), another volatile species whose reactivity has so far hindered measurements. Therefore, the global emissions and climate impacts of MeSH remain unexplored. We compiled a database of seawater MeSH concentrations, determined their statistical predictors, and generated monthly columns of global oceanic MeSH emissions that were added to DMS emissions. When implemented in global chemical climate models, MeSH emissions increase sulfate aerosol loading in the Southern Ocean by 30% to 70%, enhancing aerosol cooling effects while depleting atmospheric oxidants and increasing DMS lifetime and transport. Taking MeSH emissions into account can reduce the radiative bias of current climate models in this climate-relevant region.
https://www.science.org/doi/10.1126/sciadv.adq2465
But let’s not get too hung up on the past. Of course, we've been modeling ocean sulfur emissions for years and conveniently left MeSH out because no one thought it was important enough. Dimethyl sulfide (DMS) has everyone's attention. It is the prom queen of sulfur compounds, while MeSH lurks in the shadows, its impact obscured by inconvenient analytical challenges. If only we had better tools sooner, or more curiosity. Instead, climate models have been buzzing with ignorance about this super-potent source of sulfur.
The Myth of “Established Science”
This latest discovery underscores the obvious: The so-called “established science” of climate predictions is as settled as a house of cards in a storm. For years we have been told that these models are robust and their predictions reliable. Meanwhile, every few years, another key factor (like MeSH) comes along that requires a major recalibration, but we are constantly reassured by the past accuracy and future reliability of these models, as if these revelations were just footnotes rather than a paradigm shift. Are these models approximations of reality, or random guesses cloaked in complex mathematics?
The study's authors painstakingly collected global data on MeSH concentrations, feeding them into chemical climate models to quantify its effects. result? MeSH not only enhances the aerosol cooling effect, but also extends the service life of DMS and enhances its cooling effect. Essentially, the climate system has been hiding the dual nature of sulfur-driven cooling that we are only now discovering.
Why does this keep happening?
Perhaps it’s time to acknowledge that climate models, while valuable, are not omniscient. They concern both what we know and what we do not know. MeSH joins a long list of overlooked or misunderstood variables (such as cloud microphysics, ocean circulation anomalies, and feedback loops) that are fundamentally changing our understanding of Earth's climate system.
In this case, the consequences are obvious. The additional cooling effect of MeSH may mean that we are overestimating some warming scenarios. Or, it might just add another layer of uncertainty to already imprecise forecasts. Regardless, the narrative of “fixed science” has taken another hit.
Lessons in humility (or lack of humility)
To the climate science community: Congratulations on this groundbreaking discovery. really. But let’s not pretend this is the last time something crawls out of the data to rewrite the story. The next unconsidered variable may already be lurking, ready to wreak havoc on those so-called “final” IPCC models.
To everyone else: remember this the next time you're told to trust a model without question. They are useful tools, but they are only as good as the data and assumptions behind them. As MeSH shows, these assumptions are often incomplete.
MeSH is thus an unsung brimstone hero who proves once again that “sound science” is more marketing than reality. What other surprises does climate science hold? stay tuned. Or don't. Whether we are ready or not, the climate will continue to change.
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