The Impact of New Particle Formation from Biogenic Organic Compounds in the Atmosphere

Abstract:

Nucleation or new particle formation in the atmosphere accounts for almost half of the cloud condensation nuclei (CCN) across the globe and in doing so plays a significant role in modulating the Earth’s energy balance. Experiments performed in the CERN CLOUD chamber show substantial nucleation caused by oxidation products of monoterpene emitted by vegetation. Here we show the significance of nucleation involving biogenic organic compounds in producing atmospheric particles and estimate the impact on climate. Firstly the results show that in the present-day atmosphere organic-only nucleation is highly suppressed in most parts of the world, but makes a major contribution to particle concentrations when sulphuric acid participates in the nucleation process. But organic nucleation mechanisms are likely to play a more significant role in the pre-industrial atmosphere than the present, making it an important factor to be considered when estimating the first indirect forcing of climate due to anthropogenic aerosols from pre-industrial to the present day. Previous studies have concluded that biogenic emissions are not a major factor in controlling modelled CCN number concentrations when compared to other larger model uncertainties. This study will also show to what extent the modelled CCN number concentration, and in turn the estimated first indirect forcing, is sensitive to this improved understanding of the role of biogenic organics in particle formation, in addition to the role they have been known to play in particle growth.