What was done
Airborne particulate samples were obtained from the northernmost manned site in the world - Alert, Northwest Territories, Canada - from 1980 to 1991 and analyzed to determine weekly concentrations of 24 different particulate constituents.

What was learned
One of the more interesting discoveries of the research was the identification of biogenic sulfur, including sulfate and methane sulfonate, the concentrations of which were low in winter but high in summer.  It was also found that the year-to-year variability in the strength of this biogenic sulfur signal was strongly correlated with the average temperature of the Northern Hemisphere.

What it means
In the words of the authors, "this result suggests that as the temperature rises, there is increased biogenic production of the reduced sulfur precursor compounds that are oxidized in the atmosphere to sulfate and methane sulfonate and could be evidence of a negative feedback mechanism in the global climate system."