Background
The authors state that "organic aerosol (OA) components account for a large, sometimes even dominant [our italics], fraction of air particulate matter," and that "they influence the physical and chemical properties of aerosol particles and thus have effects on the atmosphere and climate through interaction with reactive trace gases, water vapour, clouds, precipitation, and radiation."

What was done
As a result of the importance of OA to global climate change, Fuzzi et al. assessed the current state of relevant science, prioritizing issues related to OA effects on atmospheric processes and climate, and providing a basis for future research activities in those fields.

What was learned
The international team of scientists, composed of researchers from Finland, Germany, Greece, Italy, Japan, Switzerland and the United States, found that "in spite of impressive advances in recent years ... our understanding of OA composition, physical and chemical properties, sources, transformation and removal characteristics is very limited [our italics], and estimates of their actual environmental effects are highly uncertain [our italics]." As a result, they say that "a comprehensive characterization and mechanistic understanding of particle sources, properties, and transformation is required for quantitative assessment, reliable prediction, and efficient control of natural and anthropogenic aerosol effects on climate," and they go on to list a host of related "outstanding issues for future research."

What it means
With so much unknown about so many aspects of something of such great importance to the subject of global climate change, it is amazing that climate alarmists have such great confidence in the output of climate model simulations, especially when many other things related to future climate change are equally riddled with unresolved complexities. Then again, maybe it's not amazing after all, if they are driven by something other than science.