Search

Atmospheric aerosol particles can significantly influence the climate system. Analyses of observations and observation-based modelling data reveal that biogenic aerosol emissions soar in response to warming, exerting a cooling effect in a negative feedback loop.

Secondary organic aerosol (SOA) particles can scatter radiation and act as cloud condensation nuclei, and thereby influence the Earth's radiation balance. It is generally assumed that SOA particles are liquid, but these authors show that they can adopt an amorphous solid state under ambient conditions. The findings challenge traditional views of the kinetics and thermodynamics of SOA formation and transformation in the atmosphere.

The growth of the smallest atmospheric particles to sizes at which they may act as seeds for cloud droplets is a key step linking aerosols to clouds and climate. A synthesis of research indicates that the mechanisms controlling this growth depend on the size of the growing particle.

Uncertainties in the absorptive properties of black and brown carbon particles limit our understanding of their warming potential. Following an extensive field campaign, Liuet al. report that the magnitude of warming is dependent on particle coatings, which vary due to source and photochemical aging.

Organic aerosol particles are important to climate and human health but remain poorly characterized on account of their immense chemical complexity. Here, using both field and laboratory measurements of organic aerosol, we demonstrate the use of average carbon oxidation state for describing aerosol chemical properties and atmospheric transformations.

Atmospheric organic compounds are central to key chemical processes that influence air quality. Concurrent measurements of a wide range of these compounds, including previously unmeasured ones, provide closure on OH reactivity.

The growth rates of freshly formed aerosol particles influence what fraction of these can reach sizes large enough to affect cloud formation and climate. Here, the authors show that the nano-particle growth in a sulphuric acid containing system can be enhanced by the presence of ions or small acid-base clusters.

The growth of nucleated organic particles has been investigated in controlled laboratory experiments under atmospheric conditions; initial growth is driven by organic vapours of extremely low volatility, and accelerated by more abundant vapours of slightly higher volatility, leading to markedly different modelled concentrations of atmospheric cloud condensation nuclei when this growth mechanism is taken into account.

Amines at typical atmospheric concentrations of a only few molecules per trillion air molecules combine with sulphuric acid to form highly stable aerosol particles at rates similar to those observed in the lower atmosphere.

Aerosol particles can form in the atmosphere by nucleation of highly oxidized biogenic vapours in the absence of sulfuric acid, with ions from Galactic cosmic rays increasing the nucleation rate by one to two orders of magnitude compared with neutral nucleation.

The link between biogenic volatile organic compounds in the atmosphere and their conversion to aerosol particles is unclear, but a direct reaction pathway is now described by which volatile organic compounds lead to low-volatility vapours that can then condense onto aerosol surfaces, producing secondary organic aerosol.