What was done
The authors measured size-resolved physical and chemical properties of aerosols found in northeast Atlantic marine air arriving at the Mace Head Atmospheric Research station on the west coast of Ireland during phytoplanktonic blooms at various times of the year.

What was learned
O'Dowd et al. report that in the winter, when biological activity was at its lowest, the organic fraction of the submicrometer aerosol mass was about 15%.  During the spring through autumn, however, when biological activity was high, they found that "the organic fraction dominates and contributes 63% to the submicrometer aerosol mass (about 45% is water-insoluble and about 18% water-soluble)."  Based on these findings, they performed model simulations that indicated that the marine-derived organic matter "can enhance the cloud droplet concentration by 15% to more than 100% and is therefore an important component of the aerosol-cloud-climate feedback system involving marine biota."

What it means
The authors state that "the data presented here completely change the picture of what influences marine cloud condensation nuclei given that water-soluble organic carbon, water-insoluble organic carbon and surface-active properties, all of which influence the cloud condensation nuclei activation potential, are typically not parameterized in current climate models."  Quoting them further, they say that "an important source of organic matter from the ocean is omitted from current climate-modelling predictions and should be taken into account."  We totally agree, as we have long championed the idea that both marine and terrestrial biology can influence climate via a number of important negative feedback phenomena involving atmospheric aerosols [see, for example, Feedback Factors (Biophysical) in our Subject Index].